Multistep reduction gear

• US 6,960,149 B2
• Filed: 03/27/2002
• Issued: 11/01/2005
• Est. Priority Date: 03/30/2001
• Status: Expired due to Term

• Current Assignee: ZF Friedrichshafen AG (Zeppelin - Stiftung der Stadt Friedrichshafen)
• Original Assignee: ZF Friedrichshafen AG (Zeppelin - Stiftung der Stadt Friedrichshafen)
• Inventors: Ziemer, Peter
• Primary Examiner(s): Ho, Ha
• Application Number:
  US10/472,918
• Publication Number:
  US 20040048716A1
• Time in Patent Office: 1,315 Days
• Field of Search: 475/275, 475/276, 475/277, 475/278, 475/280, 475/296
• US Class Current: 475/276
• CPC Class Codes: B62M 11/18 with a plurality of planetary gear units
• CPC Class Codes: F16H 2200/003 characterised by the number of forward speeds
• CPC Class Codes: F16H 2200/0056 the gear ratios comprising seven forward speeds
• CPC Class Codes: F16H 2200/0065 the gear ratios comprising nine forward speeds
• CPC Class Codes: F16H 2200/0073 the gear ratios comprising eleven forward speeds
• CPC Class Codes: F16H 2200/0091 the gear ratios comprising three reverse speeds
• CPC Class Codes: F16H 2200/201 with three sets of orbital gears
• CPC Class Codes: F16H 2200/2012 with four sets of orbital gears
• CPC Class Codes: F16H 2200/2015 with five sets of orbital gears
• CPC Class Codes: F16H 2200/2023 using a Ravigneaux set with 4 connections
• CPC Class Codes: F16H 2200/2046 with six engaging means
• CPC Class Codes: F16H 2200/2048 with seven engaging means
• CPC Class Codes: F16H 2200/2051 with eight engaging means
• CPC Class Codes: F16H 2200/2053 with nine engaging means
• CPC Class Codes: F16H 2200/2097 comprising an orbital gear set member permanently connected to the housing, e.g. a sun wheel permanently connected to the housing
• CPC Class Codes: F16H 3/66 composed of a number of gear trains without drive passing from one train to another
• CPC Class Codes: F16H 3/663 with conveying rotary motion between axially spaced orbital gears, e.g. RAVIGNEAUX
• CPC Class Codes: F16H 3/666 with compound planetary gear units, e.g. two intermeshing orbital gears F16H3/663 takes precedence

Abstract

A multi-step reduction gear having a drive shaft (1) connected to a front-mounted gear group (VS) having switch elements (A, B, C, D, E) which is connected to a rear-mounted gear group (NS) having switch elements (M, H, L) by a spacer shaft (2) rotating at an output speed (nvs) of the front-mounted gear group (VS). An input speed (n) of the drive shaft (1) can be transmitted to an output shaft (3) for at least seven forward gears wherein a change from one gear to the next highest or next lowest gear only requires a disconnection of one switch element and a connection of one other switch element.

Claims

1. A multi-step reduction gear comprising:

a drive shaft (1) which is connected to a front-mounted gear group (VS),

an output shaft (3) which is connected to a rear-mounted gear group (NS),

a plurality of switch elements (A, B, C, D, E) acting on the front-mounted gear group (VS); and

first and second switch elements (M, H, L) acting on the rear-mounted gear group (NS), and by selectively switching said switch elements (A, B, C, D, E and M, H, L), acting on the front-mounted and rear-mounted gear groups (VS, NS), an input speed (n) of the drive shaft (1) can be transmitted to the output shaft (3) for the purpose of shifting at least seven forward gears in such a way that in order to change from one gear to the next highest or next lowest gear the switch elements (A, B, C, D, E and M, H, L, M), acting on the front-mounted and rear-mounted gear groups (VS, NS), that have just been actuated only disconnect one switch element and connect one further switch element, and the rear-mounted group (NS) can be connected to the drive shaft (1) via at least the second switch element (H) acting on the rear-mounted group (NS);

wherein the front-mounted gear group (VS) is formed by first and second coupled, shiftable front-mounted planetary gear sets (VS1, VS2) and a maximum of two further non-shiftable front-mounted planetary gear sets (VSa, VSb), and the rear-mounted gear group (NS) is firmly connected to the front-mounted gear group (VS) by one spacer shaft (2) rotating at an output speed (nvs) of the front-mounted gear group (VS), with the spacer shaft not being connected to any one of the switch elements (A, B, C, D, E and M, H, L), acting on the front-mounted and rear-mounted gear groups (VS, NS), and the output speed (nvs) of the front-mounted gear group (VS) is generated by selectively engaging a maximum of two of the plurality switch elements (A, B, C, D, E) acting on the front-mounted gear group (VS).

2. The multi-step reduction gear pursuant to claim 1, wherein the rear-mounted group (NS) is a shiftable two-planet carrier/four-shaft transmission, including a first and a second rear-mounted planetary gear set (NS1, NS), the first switch element (M) of the rear-mounted group (NS) is a brake and the second switch element (H) of the rear-mounted group (NS) is a clutch, and the rear-mounted group (NS) can be connected to the drive shaft (1) through the second switch element (H), and at least nine forward gears can be shifted.

3. The multi-step reduction gear pursuant to claim 1, wherein the rear-mounted group (NS) is a shiftable two-planet carrier/four-shaft transmission, including a first and a second rear-mounted planetary gear set (NS1, NS2), the first switch element (M) is a clutch, the second switch element (H) is a clutch, and a third switch element (L), acting on the rear-mounted gear group (NS), is a clutch or a brake, and the rear-mounted group (NS) can be connected to the drive shaft (1) through the second switch element (H), and at least nine forward gears can be shifted.

4. The multi-step reduction gear pursuant to claim 1, wherein the spacer shaft (2), between the front-mounted group (VS) and the rear-mounted group (NS), is connected to a spider gear of a second rear-mounted planetary gear set (NS2).

5. The multi-step reduction gear pursuant to claim 4, wherein the spider gear of the second rear-mounted planetary gear set (NS2), with said gear being connected to the spacer shaft (2), is a sun wheel (41) of the second rear-mounted planetary gear set (NS2).

6. The multi-step reduction gear pursuant to claim 4, wherein the spider gear of the second rear-mounted planetary gear set (NS2), with said gear being connected to the spacer shaft (2), is a ring gear (43) of the second rear-mounted planetary gear set (NS2).

7. The multi-step reduction gear pursuant to claim 2, wherein:

the plurality of switch elements acting on the front-mounted group (VS) comprises first, second, third and fourth switch elements (A, B, C, D), a shiftable first front-mounted planetary gear set (VS1) with a sun wheel (11), a ring gear (13) and a planet carrier (15) with planetary gears (12), as well as a shiftable second front-mounted planetary gear set (VS2) with a sun wheel (21), a ring gear (23) and a planet carrier (25) with planetary gears (22);

the shiftable first rear-mounted planetary gear set (NS1) includes a sun wheel (31), a ring gear (33) and a planet carrier (35) with planetary gears (32);

the shiftable second rear-mounted planetary gear set (NS2) includes a sun wheel (41), a ring gear (43) and a planet carrier (45) with planetary gears (42);

the ring gear (13) of the first front-mounted planetary gear set (VS1) and the planet carrier (25) of the second front-mounted planetary gear set (VS2) are connected to each other and can be fixed by the fourth switch element (D) of the front-mounted group (VS);

the ring gear (23) of the second front-mounted planetary gear set (VS2) and the planet carrier (15) of the first front-mounted planetary gear set (VS1) are connected to each other and via the spacer shaft (2) also to the sun wheel (41) of the second rear-mounted planetary gear set (NS2);

the ring gear (33) of the first mar-mounted planetary gear set (NS1) and the planet carrier (45) of the second rear-mounted planetary gear set (NS2) are connected to each other and can be connected to the drive shaft (1) by the second switch element (H) of the rear-mounted group (NS);

the ring gear (43) of the second rear-mounted planetary gear set (NS2) and the planet carrier (35) of the first rear-mounted planetary gear set (NS1) are connected to each other and to the output shaft (3);

the sun wheel (11) of the first front-mounted planetary gear set (VS1) can be connected to the drive shaft (1) through the first switch element (A) of the front-mounted group (VS);

the sun wheel (21) of the second front-mounted planetary gear set (VS2) can be connected to the drive shaft (1) through the second switch element (B) of the front-mounted group (VS) and can be fixed by the third switch element (C) of the front-mounted group (VS); and

the sun wheel (31) of the first rear-mounted planetary gear set (NS1) can be fixed by the first switch element (M) of the rear-mounted group (NS).

8. The multi-step reduction gear pursuant to claim 2, wherein:

the plurality of switch elements acting on the front-mounted group (VS) comprises first, second, third and fourth switch elements (A, B, D, E), a shiftable first front-mounted planetary gear set (VS1) with a sun wheel (11), a ring gear (13) and a planet carrier (15) with planetary gears (12), and a shiftable second front-mounted planetary gear set (VS2) with a sun wheel (21), a ring gear (23) and a planet carrier (25) with planetary gears (22);

the shiftable first rear-mounted planetary gear set (NS1) includes a sun wheel (31) a ring gear (33) and a planet carrier (35) with planetary gears (32);

the shiftable second rear-mounted planetary gear set (NS2) includes a sun wheel (41), a ring gear (43) and a planet carrier (45) with planetary gears (42);

the ring gear (13) of the first front-mounted planetary gear set (VS1) and the planet carrier (25) of the second front-mounted planetary gear set (VS2) are connected to each other, can be fixed by the third switch element (B) of the front-mounted group (VS) and can be connected to the drive shaft (1) through the fourth switch element (E) of the front-mounted group (VS);

the ring gear (23) of the second front-mounted planetary gear set (VS2) and the planet carrier (15) of the first front-mounted planetary gear set (VS1) are connected to each other and via the spacer shaft (2) also to the ring gear (43) of the second rear-mounted planetary gear set (NS2);

the ring gear (33) of the first rear-mounted planetary gear set (NS1) and the planet carrier (45) of the second rear-mounted planetary gear set (NS2) are connected to each other and can be connected to the drive shaft (1) by the second switch element (H) of the rear-mounted group (NS);

the sun wheels (31, 41) of the first and second rear-mounted planetary gear sets (NS1, NS2) are connected to each other and can be fixed by the first switch element (M) of the rear-mounted group (NS);

the sun wheel (21) of the second front-mounted planetary gear set (VS2) can be connected to the drive shaft (1) through the second switch element (B) of the front-mounted group (VS);

the sun wheel (11) of the first front-mounted planetary gear set (VS1) can be fixed by the first switch element (A) of the front-mounted group (VS); and

the planet carrier (35) of the first rear-mounted planetary gear set (NS1) is connected to the output shaft (3).

9. The multi-step reduction gear pursuant to claim 2, wherein:

the plurality of switch elements (A, B, C, D, E) acting on the front-mounted group (VS) comprises first, second, third and fourth switch elements (A, B, C, D), a shiftable first front-mounted planetary gear set (VS1) with a sun wheel (11), a ring gear (13) and two coupled planet carriers (15′

, 15″

) with interior and exterior planetary gears (12′

, 12″

), as well as a shiftable second front-mounted planetary gear set (VS2) with a sun wheel (21), a ring gear (23) and a planet carrier (25) with planetary gears (22);

the shiftable first rear-mounted planetary gear set (NS1) includes a sun wheel (31), a ring gear (33) and a planet carrier (35) with planetary gears (32);

the shiftable second rear-mounted planetary gear set (NS2) includes a sun wheel (41), a ring gear (43) and two coupled planet carriers (45′

, 45″

) with interior and exterior planetary gears (42′

, 42′

);

the ring gears (13, 23) of the two front-mounted planetary gear sets (VS1, VS2) are connected to each other and are connected to the sun wheel (41) of the second rear-mounted planetary gear set (NS2) by the spacer shaft (2);

the planet carriers (15′

, 15″

, 25) of the two front-mounted planetary gear sets (VS1, VS2) are connected to each other and can be fixed with the fourth switch element (D) of the front-mounted group (VS);

the ring gears (33, 43) of the two rear-mounted planetary gear sets (NS1, NS2) are connected to each other and can be connected to the drive shaft (1) by the second switch element (H) of the rear-mounted group (NS);

the planet carriers (35, 45″

, 45′

) of the two rear-mounted planetary gear sets (NS1, NS2) are connected to each other and to the output shaft (3);

the sun wheel (11) of the first front-mounted planetary gear set (VS1) can be connected to the drive shaft (1) through the first switch element (A) of the front-mounted group (VS);

the sun wheel (21) of the second front-mounted planetary gear set (VS2) can be connected to the drive shaft (1) through the second switch element (B) of the front-mounted group (VS) and can be fixed by the third switch element (C) of the front-mounted group (VS); and

the sun wheel (31) of the first rear-mounted planetary gear set (NS1) can be fixed by the first switch element (M) of the rear-mounted group (NS).

10. The multi-step reduction gear pursuant to claim 2, wherein:

the plurality of switch elements (A, B, D, E) acting on the front-mounted group (VS) comprises first, second, third, fourth and fifth switch elements (A, B, C, D, E), a shiftable first front-mounted planetary gear set (VS1) with a sun wheel (11), a ring gear (13) and a planet carrier (15) with planetary gears (12), as well as a shiftable second front-mounted planetary gear set (VS2) with a sun wheel (21), a ring gear (23) and a planet carrier (25) with planetary gears (22);

the shiftable first rear-mounted planetary gear set (NS1) includes a sun wheel (31), a ring gear (33) and a planet carrier (35) with planetary gears (32);

the shiftable second rear-mounted planetary gear set (NS2) includes a sun wheel (41), a ring gear (43) and a planet carrier (45) with planetary gears (42);

the ring gear (13) of the first front-mounted planetary gear set (VS1) and the planet carrier (25) of the second front-mounted planetary gear set (VS2) are connected to each other, can be fixed by the fourth switch element (D) of the front-mounted group (VS) and can be connected to the drive shaft (1) by the fifth switch element (E) of the front-mounted group (VS);

the ring gear (23) of the second front-mounted planetary gear set (VS2) and the planet carrier (15) of the first front-mounted planetary gear set (VS1) are connected to each other and via the spacer shaft (2) also to the sun wheel (41) of the second rear-mounted planetary gear set (NS2);

the ring gear (33) of the first rear-mounted planetary gear set (NS1) and the planet carrier (45) of the second rear-mounted planetary gear set (NS2) are connected to each other and can be connected to the drive shaft (1) by the second switch element (H) of the rear-mounted group (NS);

the ring gear (43) of the second rear-mounted planetary gear set (NS2) and the planet carrier (35) of the first rear-mounted planetary gear set (NS1) are connected to each other and to the output shaft (3);

the sun wheel (11) of the first front-mounted planetary gear set (VS1) can be fixed through the first switch element (A) of the front-mounted group (VS);

the sun wheel (21) of the second front-mounted planetary gear set (VS2) can be connected to the drive shaft (1) through the second switch element (B) of the front-mounted group (VS) and can be fixed by the third switch element (C) of the front-mounted group (VS); and

the sun wheel (31) of the first rear-mounted planetary gear set (NS1) can be fixed by the first switch element (M) of the rear-mounted group (NS).

11. The multi-step reduction gear pursuant to claim 2, wherein:

the plurality of switch elements (A, B, C, D, E) acting on the front-mounted group (VS) comprises first, second, third, fourth and fifth switch elements (A, B, C, D, E), a shiftable first front-mounted planetary gear set (VS1) with a sun wheel (11), a ring gear (13) and a planet carrier (15) with planetary gears (12), as well as a shiftable second front-mounted planetary gear set (VS2) with a sun wheel (21), a ring gear (23) and a planet carrier (25) with planetary gears (22);

the shiftable first rear-mounted planetary gear set (NS1) includes a sun wheel (31), a ring gear (33) and a planet carrier (35) with planetary gears (32);

the shiftable second rear-mounted planetary gear set (NS2) includes a sun wheel (41), a ring gear (43) and a planet carrier (45) with planetary gears (42);

the ring gear (13) of the first front-mounted planetary gear set (VS1) and the planet carrier (25) of the second front-mounted planetary gear set (VS2) are connected to each other, can be fixed by the fourth switch element (D) of the front-mounted group (VS) and can be connected to the drive shaft (1) by the fifth switch element (E) of the front-mounted group (VS);

the ring gear (23) of the second front-mounted planetary gear set (VS2) and the planet carrier (15) of the first front-mounted planetary gear set (VS1) are connected to each other and via the spacer shaft (2) also to the ring gear (43) of the second rear-mounted planetary gear set (NS2);

the ring gear (33) of the first rear-mounted planetary gear set (NS1) and the planet carrier (45) of the second rear-mounted planetary gear set (NS2) are connected to each other and can be connected to the drive shaft (1) by the second switch element (H) of the rear-mounted group (NS);

the planet carrier (35) of the first rear-mounted planetary gear set (NS1) is connected to the output shaft (3);

the sun wheel (11) of the first front-mounted planetary gear set (VS1) can be connected to the drive shaft (1) through the first switch element (A) of the front-mounted group (VS);

the sun wheel (21) of the second front-mounted planetary gear set (VS2) can be connected to the drive shaft (1) through the second switch element (B) of the front-mounted group (VS) and can be fixed by the third switch element (C) of the front-mounted group (VS); and

the sun wheels (31, 41) of the two rear-mounted planetary gear sets (NS1, NS2) are connected to each other and can be fixed by the first switch element (M) of the rear-mounted group (NS).

12. The multi-step reduction gear pursuant to claim 2, wherein:

the plurality of switch elements (A, B, C, D, E) acting on the front-mounted group (VS) comprises first, second, third, fourth and fifth switch elements (A, B, C, D, E), a shiftable first front-mounted planetary gear set (VS1) with a sun wheel (11), a ring gear (13) and a planet carrier (15) with planetary gears (12), a shiftable second front-mounted planetary gear set (VS2) with a sun wheel (21), a ring gear (23) and a planet carrier (25) with planetary gears (22), as well as a non-shiftable

third front-mounted planetary gear set (VSa) includes a sun wheel (11a), a ring gear (13a) and two coupled planet carriers (15a′

, 15a″

) with interior and exterior planetary gears (12a′

, 12a″

);

the shiftable first rear-mounted planetary gear set (NS1) includes comprises a sun wheel (31), a ring gear (33) and a planet carrier (35) with planetary gears (32);

the shiftable second rear-mounted planetary gear set (NS2) includes a sun wheel (41), a ring gear (43) and a planet carrier (45) with planetary gears (42);

the sun wheel (11a) of the third front-mounted planetary gear set (VSa) is fixed;

the coupled planet carriers (15a′

, 15a″

) of the third front-mounted planetary gear set (VSa) are connected to the drive shaft (1);

the sun wheel (11a) of the first front-mounted planetary gear set (VS1) can be connected to the drive shaft (1) through the first switch element (A) of the front-mounted group (VS);

the sun wheel (21) of the second front-mounted planetary gear set (VS2) can be connected to the ring gear (13a) of the third front-mounted planetary gear set (VSa) through the second switch element (B) of the front-mounted group (VS) and can be fixed through the third switch element (C) of the front-mounted group (VS);

the sun wheel (31) of the first rear-mounted planetary gear set (NS1) can be fixed through the first switch element (M) of the rear-mounted group (NS);

the ring gear (13) of the first front-mounted planetary gear set (VS1) and the planet carrier (25) of the second front-mounted planetary gear set (VS2) are connected to each other, can be fixed through the fourth switch element (D) of the front-mounted group (VS) and can be connected to the drive shaft (1) by the fifth switch element (E) of the front-mounted group (VS);

the ring gear (23) of the second front-mounted planetary gear set (VS2) and the planet carrier (15) of the first front-mounted group gear set (VS1) are connected to each other and via the spacer shaft (2) to the sun wheel (41) of the second rear-mounted planetary gear set (NS2);

the ring gear (33) of the first rear-mounted planetary gear set (NS1) and the planet carrier (45) of the second rear-mounted group gear set (NS2) are connected to each other and can be connected via the second switch element (H) of the rear-mounted group (NS) to the drive shaft (1); and

the ring gear (43) of the second rear-mounted planetary gear set (NS2) and the planet carrier (35) of the first rear-mounted gear set (NS1) are connected to each other and to the output shaft (3).

13. The multi-step reduction gear pursuant to claim 2, wherein:

the plurality of switch elements (A, B, C, D, E) acting on the front-mounted group (VS) comprises first, second, third, fourth and fifth switch elements (A, B, C, D, E), a shiftable first front-mounted planetary gear set (VS1) with a sun wheel (11), a ring gear (13) and a planet carrier (15) with planetary gears (12), a shiftable second front-mounted planetary gear set (VS2) with a sun wheel (21), a ring gear (23) and a planet carrier (25) with planetary gears (22), as well as a non-shiftable third front-mounted planetary gear set (Vsa) with a sun wheel (11a), a ring gear (13a) and a planet carrier (15a) with a stepped planetary gear system comprising small and large planetary gears (12ak, 12ag);

the shiftable first rear-mounted planetary gear set (NS1) includes a sun wheel (31), a ring gear (33) and a planet carrier (35) with planetary gears (32);

the shiftable second rear-mounted planetary gear set (NS2) includes a sun wheel (41), a ring gear (43) and a planet carrier (45) with planetary gears (42);

the sun wheel (11a) of the third front-mounted planetary gear set (VSa) engages with the small planetary gears (12ak) of the third front-mounted planetary gear set (VSa) and is fixed;

the ring gear (13a) of the third front-mounted planetary gear set (VSa) is connected to the drive shaft (1) and engages on the large planetary gears (12ag) of the third front-mounted planetary gear set (VSa);

the sun wheels (11, 21) of the two front-mounted planetary gear sets (VS1, VS2) are connected to each other, can be fixed through the third switch element (C) of the front-mounted group (VS), and can be connected to the planet carrier (15a) of the third front-mounted planetary gear set (VSa) by the second switch element (B) of the front-mounted group (VS);

the ring gears (13, 23) of the two front-mounted planetary gear sets (VS1, VS2) are connected to each other and can be connected to the drive shaft (1) by the first switch element (A) of the front-mounted group (VS);

the planet carrier (25) of the second front-mounted planetary gear set (VS2) can be connected to the planet carrier (15a) of the third front-mounted planetary gear set (VSa) through the fourth switch element (D) of the front-mounted group (VS) as well as to the drive shaft (1) by the fifth switch element (E) of the front-mounted group (VS);

the planet carriers (35, 45) of the two rear-mounted planetary gear sets (NS1, NS2) are connected to each other and can be connected to the drive shaft (1) through the second switch element (H) of the rear-mounted group (NS);

the sun wheel (41) of the second rear-mounted planetary gear set (NS2) and the ring gear (33) of the first rear-mounted gear set (NS1) are connected to each other and via the spacer shaft (2) to the planet carrier (15) of the first front-mounted planetary gear set (VS1);

the sun wheel (31) of the first rear-mounted planetary gear set (NS1) can be fixed via the first switch element (M) of the rear-mounted group (NS); and

the ring gear (43) of the second rear-mounted planetary gear set (NS2) is connected to the output shaft (3).

14. The multi-step reduction gear pursuant to claim 2, wherein:

the plurality of switch elements (A, B, C, D, E) acting on the front-mounted group (VS) comprises first, second, third, fourth and fifth switch elements (A, B, C, D, E), a shiftable first front-mounted planetary gear set (VS1) with a sun wheel (11), a ring gear (13) and a planet carrier (15) with planetary gears (12), a shiftable second front-mounted planetary gear set (VS2) with a sun wheel (21), a ring gear (23) and a planet carrier (25) with planetary gears (22), as well as a non-shiftable third front-mounted planetary gear set (Vsa) with a sun wheel (11a), a ring gear (13a) and two coupled planet carriers (15a′

, 15a″

) with interior and exterior planetary gears (12a′

, 12a);

the shiftable first rear-mounted planetary gear set (NS1) includes a sun wheel (31), a ring gear (33) and a planet carrier (35) with planetary gears (32);

the shiftable second rear-mounted planetary gear set (NS2) includes a sun wheel (41), a ring gear (43) and a planet carrier (45) with planetary gears (42);

the sun wheel (11a) of the third front-mounted planetary gear set (VSa) is fixed;

the coupled planet carriers (15a′

, 15a″

) of the third front-mounted planetary gear set (VSa) are connected to the drive shaft (1);

the sun wheel (11) of the first front-mounted planetary gear set (VS1) and the ring gear (23) of the second front-mounted planetary gear set (VS2) are connected to each other and can be connected by the first switch element (A) of the front-mounted group (VS);

the sun wheel (21) of the second front-mounted planetary gear set (VS2) can be connected to the ring gear (13a) of the third front-mounted planetary gear set (VSa) through the second switch element (B) of the front-mounted group (VS) and can be fixed by the third switch element (C) of the front-mounted group (VS);

the ring gear (13) of the first front-mounted planetary gear set (VS1) and the planet carrier (25) of the second front-mounted planetary gear set (VS2) are connected to each other, can be connected to the ring gear (13a) of the third front-mounted planetary gear set (VSa) through the fourth switch element (D) of the front-mounted group (VS) as well as to the drive shaft (1) by the fifth switch element (E) of the front-mounted group (VS);

the sun wheel (41) of the second rear-mounted planetary gear set (NS2) and the ring gear (33) of the first rear-mounted planetary gear set (NS1) are connected to each other and can be connected to the planet carrier (15) of the first front-mounted planetary gear set (VS1) through the spacer shaft (2);

the planet carriers (35, 45) of the two rear-mounted planetary gear sets (NS1, NS2) are connected to each other and can be connected to the drive shaft (1) via the second switch element (H) of the rear-mounted group (NS);

the sun wheel (31) of the first rear-mounted planetary gear set (NS1) can be fixed via the first switch element (M) of the rear-mounted group (NS); and

the ring gear (43) of the second rear-mounted planetary gear set (NS2) is connected to the output shaft (3).

15. The multi-step reduction gear pursuant to claim 3, wherein:

the plurality of switch elements (A, B, C, D, E) acting on the front-mounted group (VS) comprises first, second and third switch elements (A, B, D), a shiftable first front-mounted planetary gear set (VS1) with a sun wheel (11), a ring gear (13) and a planet carrier (15) with planetary gears (12), as well as a shiftable second front-mounted planetary gear set (VS2) with a sun wheel (21), a ring gear (23) and a planet carrier (25) with planetary gears (22);

the shiftable first rear-mounted planetary gear set (NS1) includes a sun wheel (31), a ring gear (33) and a planet carrier (35) with planetary gears (32);

the shiftable second rear-mounted planetary gear set (NS2) includes a sun wheel (41), a ring gear (43) and a planet carrier (45) with planetary gears (42);

the sun wheel (11) of the first front-mounted planetary gear set (VS1) can be fixed by the first switch element (A) of the front-mounted group (VS);

the sun wheel (21) of the second front-mounted planetary gear set (VS2) can be connected to the drive shaft (1) through the second switch element (B) of the front-mounted group (VS);

the sun wheel (31) of the first rear-mounted planetary gear set (NS1) can be connected to the drive shaft (1) by the first switch element (M) of the rear-mounted group (NS);

the ring gear (13) of the first front-mounted planetary gear set (VS1) and the planet carrier (25) of the second front-mounted planetary gear set (VS2) are connected to each other and can be fixed by the third switch element (D) of the front-mounted group (VS);

the ring gear (23) of the second front-mounted planetary gear set (VS2) and the planet carrier (15) of the first front-mounted planetary gear set (VS1) are connected to each other and to the sun wheel (41) of the second rear-mounted group gear set (NS2) via the spacer shaft (2);

the ring gear (33) of the first rear-mounted planetary gear set (NS1) and the planet carrier (45) of the second rear-mounted planetary gear set (NS2) are connected to each other, can be connected to the drive shaft (1) by the second switch element (H) of the rear-mounted group (NS) and can be fixed by the third switch element (L) of the rear-mounted group (NS); and

the ring gear (43) of the second rear-mounted planetary gear set (NS2) and the planet carrier (35) of the first rear-mounted planetary carrier set (NS1) are connected to each other and to the output shaft (3).

16. The multi-step reduction gear pursuant to claim 3, wherein:

the plurality of switch elements (A, B, C, D, E) acting on the front-mounted group (VS) comprises first, second, third and fourth switch elements (A, B, D, E), a shiftable first front-mounted planetary gear set (VS1) with a sun wheel (11), a ring gear (13) and a planet carrier (15) with planetary gears (12), as well as a shiftable second front-mounted planetary gear set (VS2) with a sun wheel (21), a ring gear (23) and a planet carrier (25) with planetary gears (22);

the shiftable first rear-mounted planetary gear set (NS1) includes a sun wheel (31), a ring gear (33) and a planet carrier (35) with planetary gears (32);

the shiftable second rear-mounted planetary gear set (NS2) includes a sun wheel (41), a ring gear (43) and a planet carrier (45) with planetary gears (42);

the sun wheel (11) of the first front-mounted planetary gear set (VS1) can be fixed by the first switch element (A) of the front-mounted group (VS);

the sun wheel (21) of the second front-mounted planetary gear set (VS2) can be connected to the drive shaft (1) by the second switch element (B) of the front-mounted group (VS);

the sun wheel (31) of the first rear-mounted planetary gear set (NS1) can be connected to the drive shaft (1) by the first switch element (M) of the rear-mounted group (NS);

the ring gear (13) of the first front-mounted planetary gear set (VS1) and the planet carrier (25) of the second front-mounted planetary gear set (VS2) are connected to each other, can be fixed by the third switch element (D) of the front-mounted group (VS), and can be connected to the drive shaft (1) by the fourth switch element (E) of the front-mounted group (VS);

the ring gear (23) of the second front-mounted planetary gear set (VS2) and the planet carrier (15) of the first front-mounted planetary gear set (VS1) are connected to each other and via the spacer shaft (2) to the sun wheel (41) of the second rear-mounted gear set (NS2);

the ring gear (33) of the first rear-mounted planetary gear set (NS1) and the planet carrier (45) of the second rear-mounted planetary gear set (NS2) are connected to each other, can be connected to the drive shaft (1) by the second switch element (H) of the rear-mounted group (NS) and can be fixed by the third switch element (L) of the rear-mounted group (NS); and

the ring gear (43) of the second rear-mounted planetary gear set (NS2) and the planet carrier (35) of the first rear-mounted planetary carrier set (NS1) are connected to each other and to the output shaft (3).

17. The multi-step reduction gear pursuant to claim 3, wherein:

the plurality of switch elements (A, B, C, D, E) acting on the front-mounted group (VS) comprises first, second, third and fourth switch elements (A, B, C, D), a shiftable first front-mounted planetary gear set (VS1) with a sun wheel (11), a ring gear (13) and a planet carrier (15) with planetary gears (12), as well as a shiftable second front-mounted planetary gear set (VS2) with a sun wheel (21), a ring gear (23) and a planet carrier (25) with planetary gears (22);

the shiftable first rear-mounted planetary gear set (NS1) includes a sun wheel (31), a ring gear (33) and a planet carrier (35) with planetary gears (32);

the shiftable second rear-mounted planetary gear set (NS2) includes a sun wheel (41), a ring gear (43) and a planet carrier (45) with planetary gears (42);

the sun wheel (11) of the first front-mounted planetary gear set (VS1) can be connected to the drive shaft (1) by the first switch element (A) of the front-mounted group (VS);

the sun wheel (21) of the second front-mounted planetary gear set (VS2) can be connected to the drive shaft (1) through the second switch element (B) of the front-mounted group (VS) and can be fixed by the third switch element of the front-mounted group (VS);

the ring gear (13) of the first front-mounted planetary gear set (VS1) and the planet carrier (25) of the second front-mounted planetary gear set (VS2) are connected to each other and can be fixed by the fourth switch element (D) of the front-mounted group (VS);

the ring gear (23) of the second front-mounted planetary gear set (VS2) and the planet carrier (15) of the first front-mounted planetary gear set (VS1) are connected to each other and to the spacer shaft (2);

the spacer shaft (2) is connected to the sun wheel (41) of the second rear-mounted planetary gear set (NS2) and to the ring gear (33) of the first rear-mounted planetary gear set (NS1) coupled to said sun wheel (41);

the sun wheel (31) of the first rear-mounted planetary gear set (NS1) can be connected to the drive shaft (1) by the first switch element (M) of the rear-mounted group (NS);

the planet carriers (35, 45) of the two rear-mounted planetary gear sets (NS1, NS2) are connected to each other, can be connected to the drive shaft (1) via the second switch element (H) of the rear-mounted group (NS) and can be fixed by the third switch element (L) of the rear-mounted group (NS); and

the ring gear (43) of the second rear-mounted planetary gear set (NS2) is connected to the output shaft (3).

18. The multi-step reduction gear pursuant to claim 3, wherein:

the plurality of switch elements (A, B, C, D, E) acting on the front-mounted group (VS) comprises first, second, third, fourth and fifth switch elements (A, B, C, D, E), a shiftable first front-mounted planetary gear set (VS1) with a sun wheel (11), a ring gear (13) and a planet carrier (15) with planetary gears (12), a shiftable second front-mounted planetary gear set (VS2) with a sun wheel (21), a ring gear (23) and a planet carrier (25) with planetary gears (22), as well as a non-shiftable third front-mounted planetary gear set (VSa) with a sun wheel (11a), a ring gear (13a) and two coupled planet carriers (15a′

, 15a″

) with interior and exterior planetary gears (12a′

, 12a″

);

the shiftable first rear-mounted planetary gear set (NS1) includes a sun wheel (31), a ring gear (33) and a planet carrier (35) with planetary gears (32);

the shiftable second rear-mounted planetary gear set (NS2) includes a sun wheel (41), a ring gear (43) and a planet carrier (45) with planetary gears (42);

the drive shaft (1) is connected to the sun wheel (11a) of the third front-mounted planetary gear set (VSa);

the drive shaft (1) can be connected to the sun wheel (11) of the first front-mounted planetary gear set (VS1) via the first switch element (A) of the front-mounted group (VS);

the drive shaft (1) can be connected to the planet carrier (25) of the second front-mounted planetary gear set (VS2) via the fifth switch element (2) of the front-mounted group (VS);

the drive shaft (1) can be connected to the planet carrier (45) of the second rear-mounted planetary gear set (NS2) via the second switch element (H) of the rear-mounted group (NS);

the coupled planet carriers (15a′

, 15a″

) of the third front-mounted planetary gear set (VSa) are fixed;

the sun wheel (21) of the second front-mounted planetary gear set (VS2) can be fixed by the third switch element (C) of the front-mounted group (VS) by the planet carrier (15a″

) of the exterior planetary gears (12a″

) of the third front-mounted planetary gear set (VSa);

the ring gear (13a) of the third front-mounted planetary gear set (VSa) can be connected to the sun wheel (21) of the second front-mounted planetary gear set (VS2) through the second switch element (B) of the front-mounted group (VS);

the ring gear (13a) of the third front-mounted planetary gear set (VSa) can be connected to the planet carrier (25) of the second front-mounted planetary gear set (VS2) through the fourth switch element (D) of the front-mounted group (VS);

the ring gear (13a) of the third front-mounted planetary gear set (VSa) can be connected to the planet carrier (45) of the second rear-mounted planetary gear set (NS2) through the third switch element (L) of the rear-mounted group (NS);

the ring gear (13a) of the third front-mounted planetary gear set (VSa) can be connected to the sun wheel (31) of the first rear-mounted planetary gear set (NS1) by the first switch element (M) of the rear-mounted group (NS);

the planet carrier (25) of the second front-mounted planetary gear set (VS2) and the ring gear (13) of the first front-mounted planetary gear set (VS1) are connected to each other;

the sun wheel (11) of the first front-mounted planetary gear set (VS1) and the ring gear (23) of the second front-mounted planetary gear set (VS2) are connected to each other;

the planet carrier (15) of the first front-mounted planetary gear set (VS1) is connected to the sun wheel (41) of the second rear-mounted planetary gear set (NS2) via the spacer shaft (2);

the planet carrier (45) of the second rear-mounted planetary gear set (NS2) is connected to the ring gear (33) of the first rear-mounted planetary gear set (NS1); and

the planet carrier (35) of the first rear-mounted planetary gear set (NS1) is connected to the ring gear (43) of the second rear-mounted planetary gear set (NS2) and to the output shaft (3).

19. The multi-step reduction gear pursuant to claim 3, wherein:

the front-mounted group (VS) further includes a non-shiftable third front-mounted planetary gear set (VSa), a non-shiftable fourth front-mounted planetary gear set (Vsb) and the plurality of switch elements (A, B, C, D, E) acting on the front-mounted group (VS) comprises first, second, third, fourth and fifth switch elements (A, B, C, D, E);

the drive shaft (1) is connected to the sun wheel (11b) of the fourth front-mounted planetary gear set (VSb);

the drive shaft (1) can be connected to a sun wheel (21) of the second shiftable front-mounted planetary gear set (VS2) via the second switch element (B) of the front-mounted group (VS);

the drive shaft (1) can be connected to a planet carrier (25) comprising planetary gears (22) of the second shiftable front-mounted planetary gear set (VS2) via the fifth switch element (E) of the front-mounted group (VS);

the drive shaft (1) can be connected to a planet carrier (45) comprising planetary gears (42) of the second rear-mounted planetary gear set (NS2) via the second switch element (H) of the rear-mounted group (NS);

a sun wheel (11a) of the third front-mounted planetary gear set (VSa) is fixed;

a planet carrier (15a) with planetary gears (12a) of the third front-mounted planetary gear set (VSa) is connected to a planet carrier (15b″

) comprising exterior planetary gears (12b″

) of the fourth front-mounted planetary gear set (VSb);

the planet carrier (15a) of the third front-mounted planetary gear set (VSa) is connected to a planet carrier (15b′

) with interior planetary gears (12b′

) of the fourth front-mounted planetary gear set (VSb);

the planet carrier (15a) of the third front-mounted planetary gear set (VGSa) is connected to the sun wheel (21) of the second shiftable front-mounted planetary gear set (VS2) by the third switch element (C) of the front-mounted group (VS);

the planet carrier (15a) of the third front-mounted planetary gear set (VGSa) can be connected to the planet carrier (25) of the second shiftable front-mounted planetary gear set (VS2) by the fourth switch element (D) of the front-mounted group (VS);

the planet carrier (15a) of the third front-mounted planetary gear set (VGSa) can be connected to a planet carrier (35″

) with exterior planetary gears (32″

) of the first rear-mounted planetary gear set (NS1) by the third switch element (L) of the rear-mounted group (NS);

the planetary gears (12a) of the third front-mounted planetary gear set (VGSa) and the exterior planetary gears (12b″

) of the fourth front-mounted planetary gear set (VSb) are grouped;

a ring gear (13a) of the third front-mounted planetary gear set (VSa) and a ring gear (13b) of the fourth front-mounted planetary gear set (VSb) are connected to each other;

the ring gears (13a, 13b) of the third and fourth front-mounted planetary gear sets (VSa, VSb) can be connected to a sun wheel (11) of the first shiftable front-mounted planetary gear set (VS1) by the first switch element (A) of the front-mounted group (VS);

the ring gears (13a, 13b) of the third and fourth front-mounted planetary gear sets (VSa, VSb) can be connected to a sun wheel (31) of the first rear-mounted planetary gear set (NS1) by the first switch element (M) of the rear-mounted group (NS);

the sun wheel (11) of the first shiftable front-mounted planetary gear set (VS1) is connected to a ring gear (23) of the second shiftable front-mounted planetary gear set (VS2);

the planet carrier (25) of the second shiftable front-mounted planetary gear set (VS2) is connected to a ring gear (13) of the first shiftable front-mounted planetary gear set (VS1);

a planet carrier (15) with planetary gears (12) of the first shiftable front-mounted planetary gear set (VS1) is connected to a sun wheel (41) of the second rear-mounted planetary gear set (NS2) via the spacer shaft (2);

the planet carrier (35″

) with the exterior planetary gears (32″

) of the first rear-mounted planetary gear set (NS1) and a planet carrier (35′

) with interior planetary gears (32′

) of the first rear-mounted planetary gear set (NS1) and the planet carrier (45) with the planetary gears (42) of the second rear-mounted planetary gear set (NS2) are connected to each other;

the exterior planetary gears (32″

) of the first rear-mounted planetary gear set (NS1) and the planetary gears (42) of the second rear-mounted planetary gear set (NS2) are grouped;

a ring gear (33) of the first rear-mounted planetary gear set (NS1) and a ring gear (43) of the second rear-mounted planetary gear set (NS2) are connected to each other;

the ring gears (33,43) of the first and second rear-mounted planetary gear sets (NS1, NS2) are connected to the output shaft (3).

25. The multi-step reduction gear pursuant to claim 2, wherein a second rear-mounted group (NS′

) is a shiftable two-planet carrier/four-shaft transmission arranged after the rear-mounted group (NS), and at least eighteen forward gears can be created, the second rear-mounted group (NS′

) is formed by two shiftable rear-mounted planetary gear sets (NS1′

, NS2′

), the first switch element (M′

) is a brake and the second switch element (H′

) is a clutch, is securely connected on the input side to the output shaft (3) rotating at an output speed (nns) of the rear-mounted group (NS) and can be connected to the drive shaft (1) via the second switch element (H′

) of the second rear-mounted group (NS′

) and is connected on the output side to the output shaft (4) of the multi-step reduction gear, as well.

26. The multi-step reduction gear pursuant to claim 25, wherein:

the first shiftable rear-mounted planetary gear set (NS1′

) of the second rear-mounted group (NS′

) includes a sun wheel (51), a ring gear (53) and a planet carrier (55) with planetary gears (52);

the second shiftable rear-mounted planetary gear set (NS2′

) of the second rear-mounted group (NS′

) includes a sun wheel (61), a ring gear (63) and a planet carrier (65) with planetary gears (62);

the sun wheels (51, 61) of the first and second shiftable rear-mounted planetary gear sets (NS1′

, NS2′

) of the second rear-mounted group (NS′

) are connected to each other and can be fixed by the first switch element (M′

) of the second rear-mounted group (NS′

);

the ring gear (53) of the first shiftable rear-mounted planetary gear set (NS1′

) of the second rear-mounted group (NS′

) and the planet carrier (65) of the second shiftable rear-mounted planetary gear set (NS2′

) of the second rear-mounted group (NS′

) am connected to each other and can be connected to the drive shaft (1) via the second switch element (H′

) of the second rear-mounted group (NS′

);

the ring gear (63) of the second shiftable rear-mounted planetary gear set (NS2′

) of the second rear-mounted group (NS′

) is connected to the output shaft (3) and

the planet carrier (55) of the first shiftable rear-mounted planetary gear set (NS1) of the second rear-mounted group (NS′

) is connected to the output shaft (4).

27. The multi-step reduction gear pursuant to claim 25, wherein:

the first shiftable rear-mounted planetary gear set (NS1′

) of the second rear-mounted group (NS′

) includes a sun wheel (51), a ring gear (53) and a planet carrier (55) with planetary gears (52);

the second shiftable rear-mounted planetary gear set (NS2′

) of the second rear-mounted group (NS′

) includes a sun wheel (61), a ring gear (63) and two coupled planet carriers (65′

, 65″

) with interior and exterior planetary gears (62′

, 62″

);

the sun wheel (51) of the first shiftable rear-mounted planetary gear set (NS1′

) of the second rear-mounted group (NS′

) can be fixed by the first switch element (M′

) of the second rear-mounted group (NS′

);

the ring gears (53, 63) of the first and second shiftable rear-mounted planetary gear sets (NS1′

, NS2′

) of the second rear-mounted group (NS′

) are connected to each other and can be connected to the drive shaft (1) via the second switch element (H′

) of the second rear-mounted group (NS′

);

the sun wheel (61) of the second shiftable rear-mounted planetary gear set (NS2′

) of the second rear-mounted group (NS′

) is connected to the output shaft (3); and

the planet carriers (55, 65′

, 65″

) of the first and second shiftable rear-mounted planetary gear sets (NS1′

, NS2′

) of the second shiftable rear-mounted group (NS′

) are connected to each other and to the output shaft (4).

28. The multi-step reduction gear pursuant to claim 26, wherein:

the drive shaft (1) is connected to a sun wheel (11a) of a third front-mounted planetary gear set (VSa);

the drive shaft (1) can be connected to a planet carrier (25) with planetary gears (22) of the second shiftable front-mounted planetary gear set (VS2) via the fifth switch element (E) of the front-mounted group (VS);

the drive shaft (1) can be connected to a ring gear (13) of the first shiftable front-mounted planetary gear set (VS1) via the first switch element (A) of the front-mounted group (VS);

the drive shaft (1) can be connected to a planet carrier (45) with planetary gears (42) of the second shiftable rear-mounted planetary gear set (NS2) via the second switch element (H) of the rear-mounted group (NS);

the third front-mounted planetary gear set (VSa) is a plus-transmission;

a planet carrier (15a′

) with interior planetary gears (12a′

) of the third front-mounted planetary gear set (VSa) and a planet carrier (15a″

) with exterior planetary gears (12a″

) of the third front-mounted planetary gear set (VSa) are connected to each other and fixed;

a ring gear (13a) of the third front-mounted planetary gear set (VSa) can be connected to a sun wheel (21) of the second shiftable front-mounted planetary gear set (VS2) by the second switch element (B) of the front-mounted group;

the ring gear (13a) of the third front-mounted planetary gear set (VSa) can be connected to the planet carrier (25) of the second shiftable front-mounted planetary gear set (VS2) by a fourth switch element (D) of the front-mounted group;

the sun wheel (21) of the second shiftable front-mounted planetary gear set (VS2) is connected to a sun wheel (11) of the first shiftable front-mounted planetary gear set (VS1);

the sun wheel (21) of the second shiftable front-mounted planetary gear set (VS2) can be fixed by the third switch element (C) of the front-mounted group (VS);

the ring gear (13) of the first front-mounted, planetary shiftable (VS1) is connected to a ring gear (23) of the second shiftable front-mounted planetary gear set (VS2);

a planet carrier (15) with planetary gears (12) of the first shiftable front-mounted planetary gear set (VS1) is connected to a sun wheel (41) of the second shiftable rear-mounted planetary gear set (NS2) via the spacer shaft (2);

the planet carrier (15) of the first shiftable front-mounted planetary gear set (VS1) is connected to a ring gear (33) of the first shiftable rear-mounted planetary gear set (NS1);

the planet carrier (45) of the second shiftable rear-mounted planetary gear set (NS2) and a planet carrier (35) comprising planetary gears (32) of the first shiftable rear-mounted planetary gear set (NS1) are connected to each other;

a sun wheel (31) of the first shiftable rear-mounted planetary gear set (NS1) can be fixed by the first switch element (M) of the rear-mounted group (NS); and

a ring gear (43) of the second shiftable rear-mounted planetary gear set (NS2) is connected to the second rear-mounted group (NS) via the output shaft (3).

20. A multi-step reduction gear, comprising:

a drive shaft (1) connected to a front-mounted gear group (VS),

an output shaft (3) connected to a rear-mounted gear group (NS),

a plurality of switch elements (A, B, C, D, E) acting on the front-mounted gear group (VS); and

first, second and third switch elements (M, H, L) acting on the rear-mounted gear group (NS), and by selectively switching said switch elements (A, B, C, D, E and M, H, L), acting on the front-mounted and rear-mounted gear groups (VS, NS), an input speed (n) of the drive shaft (1) can be transmitted to the output shaft (3) for the purpose of shifting at least seven forward gears in such a way that in order to change from one gear to the next highest or next lowest gear the switch elements (A, B, C, D, E and M, H, L), acting on the front-mounted and rear-mounted gear groups VS, NS), that have just been actuated only disconnect one switch element and connect one further switch element;

the front-mounted group (VS) is formed by coupled, first and second shiftable front-mounted planetary gear sets (VS1, VS2) and a maximum of two further non-shiftable front-mounted planetary gear sets (VSa, VSb), the rear-mounted group (NS) is connected firmly to the front-mounted group (VS) via a spacer shaft (2) rotating at an output speed (nvs) of the front-mounted group (VS) and can be connected to the drive shaft (1) via at least the second switch element (H) acting on the rear-mounted group (NS), the spacer shaft (2) is connected to a spider gear of a second shiftable rear-mounted planetary gear set (NS2) designed as a sun wheel (41), and the output speed (nvs) of the front-mounted group (VS) is generated by selectively engaging a maximum of two of the plurality of switch elements (A, B, C, D, E) acting on the front-mounted group (VS),

wherein the plurality of switch elements (A, B, C, D, E) acting on the front-mounted group (VS) comprises first, second and third switch elements (A, B, D), the first shiftable front-mounted planetary gear set (VS1) having a sun wheel (11), a ring gear (13) and a planet carrier (15) with planetary gears (12), as well as the second shiftable front-mounted planetary gear set (VS2) with a sun wheel (21), a ring gear (23) and a planet carrier (25) with planetary gears (22);

a first shiftable rear-mounted planetary gear set (NS1) includes a sun wheel (31), a ring gear (33) and a planet carrier (35) with planetary gears (32);

the second shiftable rear-mounted planetary gear set (NS2) includes the sun wheel (41), a ring gear (43) and a planet carrier (45) with planetary gears (42);

the sun wheel (11) of the first shiftable front-mounted planetary gear set (VS1) can be fixed by the first switch element (A) of the front-mounted group (VS);

the sun wheel (21) of the second shiftable front-mounted planetary gear set (VS2) is connected to the drive shaft (1);

the sun wheel (31) of the first shiftable rear-mounted planetary gear set (NS1) can be connected to the drive shaft (1) by the first switch element (M) of the rear-mounted group (NS);

the ring gear (13) of the first shiftable front-mounted planetary gear set (VS1) and the planet carrier (25) of the second shiftable front-mounted planetary gear set (VS2) are connected to each other and can be fixed by the third switch element (D) of the front-mounted group (VS);

the ring gear (23) of the second shiftable front-mounted planetary gear set (VS2) and the planet carrier (15) of the first shiftable front-mounted planetary gear set (VS1) are connected to each other and via the spacer shaft (2) to the sun wheel (41) of the second shiftable rear-mounted gear set (NS2) and can be fixed by the second switch element (B) of the front-mounted group (VS);

the ring gear (33) of the first shiftable rear-mounted planetary gear set (NS1) and the planet carrier (45) of the second shiftable rear-mounted planetary gear set (NS2) are connected to each other, can be connected to the drive shaft (1) by the second switch element (H) of the rear-mounted group (NS) and can be fixed by the third switch element (L) of the rear-mounted group (NS); and

the ring gear (43) of the second shiftable rear-mounted planetary gear set (NS2) and the planet carrier (35) of the first rear-mounted planetary carrier set (NS1) are connected to each other and to the output shaft (3).

22. A multi-step reduction gear, comprising:

a drive shaft (1) connected to a front-mounted gear group (VS),

an output shaft (3) connected to a rear-mounted gear group (NS),

a plurality of switch elements (A, B, C, D, D) acting on the front-mounted gear group (VS); and

first, second and third switch elements (M, H, L) acting on the rear-mounted gear group (NS), and by selectively switching said switch elements (A, B, C, D, E and M, H, L), acting on the front-mounted and rear-mounted gear groups (VS, NS), an input speed (n) of the drive shaft (1) can be transmitted to the output shaft (3) for the purpose of shifting at least seven forward gears in such a way that in order to change from one gear to the next highest or next lowest gear the switch elements (A, B, C, D, E and M, H, L), acting on the front-mounted and rear-mounted gear groups (VS, NS), that have just been actuated only disconnect one switch element and connect one further switch element;

the front-mounted group (VS) is formed by coupled, first and second shiftable front-mounted planetary gear sets (VS1, VS2) and a maximum of two further non-shiftable front-mounted planetary gear sets (VSa, VSb), the rear-mounted group (NS) is firmly connected to the front-mounted group (VS) by a spacer shaft (2) rotating at an output speed (nvs) of the front-mounted group (VS) and can be connected to the drive shaft (1) via at least the second switch element (H) acting on the rear-mounted gear set (NS), the spacer shaft (2) is connected to a spider gear of a second rear-mounted planetary gear set (NS2) designed as a ring gear (43), and the output speed (nvs) of the front-mounted group (VS) is generated by selectively engaging a maximum of two switch elements (A, B, C, D, E) acting on the front-mounted group (VS);

wherein the plurality of switch elements (A, B, C, D, E) acting on the front-mounted group (VS) comprises first, second and third switch elements (A, B, D), a shiftable first front-mounted planetary gear set (VS1) with a sun wheel (11), a ring gear (13) and a planet carrier (15) with planetary gears (12), as well as a shiftable second front-mounted planetary gear set (VS2) with a sun wheel (21), a ring gear (23) and a planet carrier (25) with planetary gears (22);

a first shiftable rear-mounted planetary gear set (NS1) includes a sun wheel (31), a ring gear (33) and a planet carrier (35) with planetary gears (32);

the second shiftable rear-mounted planetary gear set (NS2) includes a sun wheel (41), the ring gear (43) and a planet carrier (45) with planetary gears (42);

the sun wheels (11, 21) of the first and second shiftable front-mounted planetary gear sets (VS1, VS2) are connected to each other and can be fixed by the first switch element (A) of the front-mounted group (VS);

the ring gear (23) of the second shiftable front-mounted planetary gear set (VS2) is connected to the drive shaft (1);

the ring gear (13) of the first shiftable front-mounted planetary gear set (VS1) and the planet carrier (25) of the second shiftable front-mounted planetary gear set (VS2) are connected to each other and can be fixed by the third switch element (D) of the front-mounted group (VS);

the planet carrier (15) of the first shiftable front-mounted planetary gear set (VS1) can be fixed by the second switch element (B) of the front-mounted group and is connected to the ring gear (43) of the second shiftable rear-mounted planetary gear set (NS2) via the spacer shaft (2);

the sun wheels (31, 41) of the first and second shiftable rear-mounted planetary gear sets are connected to each other and can be connected to the drive shaft (1) by the first switch element (M) of the rear-mounted group (NS);

the ring gear (33) of the first shiftable rear-mounted planetary gear set (NS1) and the planet carrier (45) of the second rear-mounted planetary carrier set (NS2) are connected to each other, can be connected to the drive shaft (1) via the second switch element (H) of the rear-mounted group (NS) and can be fixed with the third switch element (L) of the rear-mounted group (NS); and

the planet carrier (35) of the first shiftable rear-mounted planetary gear set (NS1) is connected to the output shaft (3).

21. The multi-step reduction gear pursuant to claim 22, wherein:

the first shiftable front-mounted planetary gear set (VS1) with the sun wheel (11), the ring gear (13) and the planet carrier (15) with planetary gears (12), as well as the second shiftable front-mounted planetary gear set (VS2) with the sun wheel (21), the ring gear (23) and two coupled planet carriers (25′

, 25″

) with interior and exterior planetary gears (22′

, 22″

);

the first shiftable rear-mounted planetary gear set (NS1) includes a sun wheel (31), a ring gear (33) and two coupled planet carriers (35′

, 35″

) with interior and exterior planetary gears (32′

, 32″

);

the second shiftable rear-mounted planetary gear set (NS2) includes the sun wheel (41), a ring gear (43) and a planet carrier (45) with planetary gears (42);

the sun wheel (11) of the first shiftable front-mounted planetary gear set (VS1) can be fixed by the first switch element (A) of the front-mounted group (VS);

the sun wheel (21) of the second shiftable front-mounted planetary gear set (VS2) is connected to the drive shaft (1);

the ring gears (13, 23) of the first and second shiftable front-mounted planetary gear sets (VS1, VS2) are connected to each other and can be fixed through the third switch element (D) of the front-mounted group (VS);

the planet carriers (15, 25′

, 25″

) of the first and second shiftable front-mounted planetary gear sets (VS1, VS2) are connected to each other, can be fixed by the second switch element (B) of the front-mounted group (VS), and are connected to the sun wheel (41) of the second shiftable rear-mounted planetary gear set (NS2) via the spacer shaft (2);

the sun wheel (31) of the first shiftable rear-mounted planetary gear set (NS1) can be connected to the drive shaft (1) by the first switch element (M) of the rear-mounted group (NS);

the planet carriers (35′

, 35″

, 45) of the first and second shiftable rear-mounted planetary gear sets (NS1, NS2) are connected to each other, can be connected to the drive shaft (1) by the second switch element (H) of the rear-mounted group (NS) and can be fixed by the third switch element (L) of the rear-mounted group (NS); and

the ring gears (33, 43) of the first and second shiftable rear-mounted planetary gear sets (NS1, NS2) are connected to each other and to the output shaft (3).

23. A multi-step reduction gear, comprising:

a drive shaft (1) connected to a front-mounted gear group (VS),

an output shaft (3) connected to a rear-mounted gear group (NS),

first and second switch elements (A, B) acting on the front-mounted gear group (VS); and

first, second and third switch elements (M, H, L) acting on the rear-mounted gear group (NS), and by selectively switching said switch elements (A, B, M, H, L), acting on the front-mounted and rear-mounted gear groups (VS, NS), an input speed (n) of the drive shaft (1) can be transmitted to the output shaft (3) for the purpose of shifting at least seven forward gears in such a way that in order to change from one gear to the next highest or next lowest gear the switch elements (A, B, M, H, L), acting on the front-mounted and rear-mounted gear groups (VS, NS), that have just been actuated only disconnect one switch element and connect one further switch element;

the rear-mounted group (NS) is a shiftable two-planet carrier/four-shaft transmission with a first and a second shiftable rear-mounted planetary gear set (NS1, NS2), the shiftable rear-mounted group (NS) can be connected to the drive shaft (1) by at least one of the first, second and third switch elements (M, H, L) acting on the shiftable rear-mounted group (NS);

wherein the front-mounted gear group (VS) is formed by first and second shiftable front-mounted planetaries (VS1, VS2), of which at least one is shiftable, the shiftable rear-mounted gear group (NS) is firmly connected to the front-mounted gear group (VS) by a spacer shaft (2) rotating at an output speed (nvs) of the front-mounted gear group (VS), the spacer shaft is not connected to any one of the switch elements (A, B, M, H, L) acting on the front-mounted and rear-mounted gear groups (VS, NS), and the output speed (nvs) of the front-mounted gear group (VS) is generated by selectively engaging one of the first and second switch elements (A, B) acting on the front-mounted gear group (VS) in one of the first and second shiftable front-mounted planetary gear sets (VS1, VS2).

24. The multi-step reduction gear pursuant to claim 23, wherein:

the drive shaft (1) is connected to a sun wheel (11) of the first shiftable front-mounted planetary gear set (VS1);

the drive shaft (1) can be connected to a sun wheel (21) of the second shiftable front-mounted planetary gear set (VS2) via the second switch element (B) of the front-mounted group (VS);

a planet carrier (25) with planetary gears (22) of the second shiftable front-mounted planetary gear set (VS2) is fixed;

a ring gear (13) of the first shiftable front-mounted planetary gear set (VS1) can be connected to the fixed planet carrier (25) of the second shiftable front-mounted planetary gear set (VS2) by the first switch element (A) of the front-mounted group;

the drive shaft (1) can be connected to a sun wheel (31) of the first rear-mounted planetary gear set (NS1) by the first switch element (M) of the rear-mounted group (NS);

the drive shaft (1) can be connected to a planet carrier (45) with planetary gears (42) of the second shiftable rear-mounted planetary gear set (NS2) by the second switch element (H) of the rear-mounted group (NS);

the planet carrier (45) of the second shiftable rear-mounted planetary gear set (NS2) is connected to a ring gear (33) of the first shiftable rear-mounted planetary gear set (NS1);

the planet carrier (45) of the second shiftable rear-mounted planetary gear set (NS2) can be fixed by the third switch element (L) of the rear-mounted group (NS);

a ring gear (23) of the second shiftable front-mounted planetary gear set (VS2) is connected to a planet carrier (15) of the planetary gears (12) of the first shiftable front-mounted planetary gear set (VS1);

a ring gear (23) of the second shiftable front-mounted planetary gear set (VS2) is connected to a sun wheel (41) of the second shiftable rear-mounted planetary gear set (NS2) via the spacer shaft (2);

a ring gear (43) of the second shiftable rear-mounted planetary gear set (NS2) is connected to a planet carrier (35) of the planetary gears (32) of the first shiftable rear-mounted planetary gear set (NS1); and

the ring gear (43) of the second shiftable rear-mounted planetary gear set (NS2) is connected to the output shaft (3).