Hydrostatic Piston Machine

• US 20200132069A1
• Filed: 09/27/2019
• Published: 04/30/2020
• Est. Priority Date: 10/30/2018
• Status: Active Grant

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Nafz, Timo
• Granted Patent: US 11,261,861 B2
• Time in Patent Office: Days
• CPC Class Codes: F03C 1/0636 having rotary cylinder block
• CPC Class Codes: F03C 1/0686 by changing the inclination of the swash plate
• CPC Class Codes: F04B 1/20 having rotary cylinder block
• CPC Class Codes: F04B 1/22 having two or more sets of cylinders or pistons
• CPC Class Codes: F04B 1/295 by changing the inclination of the swash plate
• CPC Class Codes: F04B 1/324 by changing the inclination of the swash plate
• CPC Class Codes: F04B 2201/1204 Position of a rotating inclined plate
• CPC Class Codes: F04B 49/002 Hydraulic systems to change the pump delivery
• CPC Class Codes: F04B 49/08 Regulating by delivery pressure
• CPC Class Codes: F04B 49/12 by varying the length of stroke of the working members

Abstract

A hydrostatic piston machine has a lifting element that is adjustable for varying a swept volume, and a rotating cylinder part having a plurality of cylinder bores with pistons that are supported on the lifting element and delimit a displacement chamber. Each displacement chamber is moved in an alternating manner by a connecting opening to overlap a low-pressure control opening situated on a low-pressure side of a stationary control part and a high-pressure control opening situated on a high-pressure side of the control part. Two switching regions are situated between the low-pressure control opening and the high-pressure control opening, the pistons changing direction at a dead center within the switching regions. The position of the lifting element is determined from a pressure profile which is a function of the variable size of the displacement chambers in a switching region, the variable size depending on the position of the lifting element.

Claims

1. A hydrostatic piston machine, which has a variable swept volume, comprising:

a lifting element that is adjustable to vary the swept volume, a position of the lifting element being determinable; and

a rotating cylinder part defining a plurality of cylinder bores, each of which includes a respective piston that is supported on the lifting element and delimits a respective displacement chamber,

wherein each respective displacement chamber is moved by way of a connecting opening in an alternating manner so as to overlap a low-pressure control opening, which is situated on a low-pressure side of a stationary control part, and a high-pressure control opening, which is situated on a high-pressure side of the stationary control part,

wherein two switching regions are situated on the stationary control part between the low-pressure control opening and the high-pressure control opening, the pistons switching direction at a dead center within the two switching regions,

wherein a state variable of the piston machine is determined from a pressure profile, which is a function of the variable size of the respective displacement chambers in a respective switching region of the two switching regions, the variable size depending on the position of the lifting element.

2. The hydrostatic piston machine according to claim 1, wherein the state variable is the position of the lifting element determined from the pressure profile.

3. The hydrostatic piston machine according to claim 1, wherein each displacement chamber, in one switching region of the two switching regions located after separation from one control opening of the low-pressure control opening and the high-pressure control opening, and prior to overlapping the other control opening of the low-pressure control opening and the high-pressure control opening, is connectable to a fluid volume via a mouth of a connecting line situated in the one switching region.

4. The hydrostatic piston machine according to claim 3, further comprising:

an electric pressure sensor configured to sense a pressure in the fluid volume,

wherein the position of the lifting element is determined from the pressure in the fluid volume.

5. The hydrostatic piston machine according to claim 4, wherein:

the mouth of the connecting line lies in the one switching region in which the respective displacement chamber changes from the low-pressure control opening to the high-pressure control opening,

the pressure in the fluid volume is a high pressure prior to connecting one of the displacement chambers to the fluid volume and, while connecting the fluid volume and the one of the displacement chambers, the pressure in the fluid volume drops to a minimum pressure, and

the position of the lifting element is determined from a ratio between the minimum pressure and the high pressure.

6. The hydrostatic piston machine according to claim 3, wherein the connecting opening is open simultaneously to the fluid volume and to the high-pressure control opening within a specific angular range and pressurized fluid for building up high pressure flows from the high-pressure control opening by way of the connecting opening and by way of the connecting line to the fluid volume.

7. The hydrostatic piston machine according to claim 3, wherein the fluid volume is throttled by a second connecting line that is permanently connected to the high-pressure side.

8. The hydrostatic piston machine according to claim 3, wherein a ratio between a size of the fluid volume and a maximum size of the respective displacement chamber in a position of the lifting element corresponds to a maximum swept volume is between 0.3 and 3.

9. The hydrostatic piston machine according to claim 8, wherein the ratio between the size of the fluid volume and the maximum size of the respective displacement chamber in a position of the lifting element corresponding to the maximum swept volume is at least approximately 0.7.

10. The hydrostatic piston machine according to claim 1, wherein each respective piston is configured without a cavity that is open toward the respective displacement chamber.

11. The hydrostatic piston machine according to claim 1, wherein an available volume of the respective displacement chamber remaining up to the stationary control part in an inner dead center of the piston in a position of the lifting element corresponding to a maximum swept volume is at least approximately zero.

12. The hydrostatic piston machine according to claim 1, further comprising:

an electric pressure sensor arranged in at least one of the two switching regions configured to detect a pressure in the respective displacement chamber.

13. The hydrostatic piston machine according to claim 1, wherein a rotating speed of the hydrostatic piston machine is determined from a frequency at which identical or similar pressure profiles succeed one another.

14. The hydrostatic piston machine according to claim 1, wherein a high pressure is determined from a maximum strength of a signal emitted by a pressure sensor.

15. The hydrostatic piston machine according to claim 1, further comprising:

an electric evaluation unit configured to receive electric signals emitted by a pressure sensor and to determine the state variable.

16. The hydrostatic piston machine according to claim 15, wherein the electric evaluation unit is configured to determine the swept volume of the hydrostatic piston machine as the state variable.

17. The hydrostatic piston machine according to claim 15, wherein the electric evaluation unit is further configured to determine at least one of a rotating speed of the hydrostatic piston machine and a high pressure.

18. The hydrostatic piston machine according to claim 1, wherein the hydrostatic piston machine is configured as a hydrostatic axial piston machine.