Multi-piston engine, such as a pump or compressor, with improved vibrational behaviour

• US 20030059314A1
• Filed: 10/03/2002
• Published: 03/27/2003
• Est. Priority Date: 12/17/1999
• Status: Active Grant

• Current Assignee: Peugeot Citroen Automobile SA (Stellantis NV)
• Original Assignee: Peugeot Citroen Automobile SA (Stellantis NV)
• Inventors: Sagnet, Michel
• Granted Patent: US 6,814,548 B2
• Time in Patent Office: Days
• US Class Current: 417/221
• CPC Class Codes: F04B 11/005 using two or more pumping pistons
• CPC Class Codes: F04B 11/0091 using a special shape of fluid pass, e.g. throttles, ducts
• CPC Class Codes: F04B 39/0055 with a special shape of fluid passage, e.g. bends, throttles, diameter changes, pipes

Abstract

The invention relates to a piston engine which is essentially comprised of an engine shaft (1) and a set of modules, each of which comprises a cylinder (2a, 2b) and a piston (3a, 3b) powered by the engine shaft in the cylinder, each module resulting in vibratory excitation of the engine at a determined fundamental frequency (Fa, Fb). Rather than introducing phase differences between the various vibratory excitations, as is the case in prior art, the invention introduces a frequency offset (ΔFab) between the fundamental frequencies (Fa, Fb) thereof in order to avoid a high-amplitude vibration at a common excitation frequency (F), arising from the spectral spread thus obtained.

Claims

1. A multi-piston engine, such as, for example, a pump or a compressor, which comprises drive shaft (1);

a number of cylinders (2a, 2b, 2c);

a number of pistons (3a, 3b, 3c) selectively driven by the alternating motion of the drive shaft and respectively housed in cylinders (2a, 2b, 2c) in order to delimit, for a fluid put in motion by the engine, a corresponding number of chambers (4a, 4b, 4c) with variable volume, each of which presents a predetermined maximum volume (Va, Vb, Vc) to the fluid and has low pressure intake (40a, 40b, 40c) and high-pressure outlet (41a, 41b, 41c); and

a number of delivery channels (5a, 5b, 5c) connecting the high pressure outlets of the respective chambers to delivery outlet (6) of the engine, each delivery channel (5a, 5b, 5c) having a predetermined cross section (Sa, Sb, Sc) and a predetermined length (La, Lb, Lc), the movement of each piston (3a, 3b, 3c) bringing about a vibrational excitation of the engine, of determined fundamental frequency (Fa, Fb, Fc), and each chamber (4a, 4b, 4c), in association with piston (3a, 3b, 3c) which delimits it and with delivery channel (5a, 5b, 5c) which connects it to delivery outlet (6), forming a corresponding module (3a, 4a, 5a;

3b, 4b, 5b;

3c, 4c, 5c) of the engine, characterized by the fact that it comprises at least a first spectral spreading means associated with a first pair of modules (3a, 4a, 5a;

3b, 4b, 5b) including a first pair of pistons (3a, 3b), this first spectral spreading means being suitable for introducing, between the fundamental frequencies (Fa, Fb) of the vibrational excitations resulting from the respective movements of pistons (3a, 3b) of this first pair, a frequency shift (Δ

Fab) equal to at most 10% of the fundamental frequency (Fa) of the vibrational excitation resulting from the movement of either (3a) of the pistons of this first pair (3a, 3b).

2. The multi-piston engine according to claim 1, characterized by the fact that the first spectral spreading means entails a difference (Ga−

Gb) between magnitudes (Ga, Gb) respectively associated with the modules of the first pair of modules (3a, 4a, 5a;

3b, 4b, 5b), each of these magnitudes (Ga, Gb) being represented, for the associated module, by the ratio (Sa/(Va·

La), Sb/(Vb·

Lb)) of the cross section (Sa, Sb) of delivery channel (5a, 5b) of this module to the product of the maximum volume (Va, Vb) of chamber (4a, 4b) of this module and the length (La, Lb) of delivery channel (5a, 5b) of this module.

3. The multi-piston engine according to claim 1 or 2, characterized by the fact that the frequency shift (Δ

Fab) introduced between the fundamental frequencies (Fa, Fb) of the vibrational excitations resulting from the respective movements of pistons (3a, 3b) of the first pair is advantageously at least equal to 1% of the fundamental frequency (Fa) of the vibrational excitation resulting from the movement of either (3a) of these pistons.

4. The multi-piston engine according to claim 3, characterized by the fact that the frequency shift (Δ

Fab) introduced between the fundamental frequencies (Fa, Fb) of the vibrational excitations resulting from the respective movements of pistons (3a, 3b) of the first pair is on the order of 2% of the fundamental frequency (Fa) of the vibrational excitation resulting from the movement of either (3a) of these pistons.

5. The multi-piston engine according to any one of the preceding claims, characterized by the fact that pistons (3a, 3b) respectively delimiting chambers 4a, 4b) of the modules of the first pair of modules are identical.

6. The multi-piston engine according to any one of the preceding claims is combination with claim 2, characterized by the fact that the first spectral spreading means entails at least a difference (Δ

Vab) between the maximum volumes (Va, Vb) of the respective chambers (4a, 4b) of the modules of the first pair of modules (3a, 4a, 5a;

3b, 4b, 5b).

7. The multi-piston engine according to claim 6, characterized by the fact that the cylinders (2a, 2b) of the modules of the first pair of modules are different.

8. The multi-piston engine according to any one of claims 1 to 6, characterized by the fact that cylinders (2a, 2b) of the modules of the first pair of modules are identical, and by the fact that at least one (2a) of these cylinders contains a solid filler block (8a) which modifies the maximum volume (Va) of chamber (4a) defined in this cylinder (2a).

9. The multi-piston engine according to claim 8, characterized by the fact that filler block (8a) is formed by a stack of several block elements (80a) all having the same volume.

10. The multi-piston engine according to claim 8 or 9, characterized by the fact that filler block (8a) is produced out of a flexible material such as polyurethane or a compressible elastomer.

11. The multi-piston engine according to any one of the preceding claims, characterized by the fact that is has as many spectral spreading means as the number of pairs of modules containing neighboring pistons.

12. The multi-piston engine according to any one of claims 1 to 10, characterized by the fact that it comprises as many spectral spreading means as the number of modules.

13. The multi-piston engine according to any one of the preceding claims, characterized by the fact that cylinders (2a, 2b, 2c) are arranged in a regular manner with respect to drive shaft (1).

14. The multi-piston engine according to any one of the preceding claims, characterized by the fact that each delivery channel (5a, 5b, 5c) is separated from delivery outlet (6) of the piston engine by non-return valve (7a, 7b, 7c).