Hydrostatic traction drive in closed hydraulic circuit and method for controlling the hydrostatic traction drive

Patent metadata

Field	Value
Publication number	US-10071719-B2
Application number	US-201514676761-A
Country	US
Kind code	B2
Filing date	Apr 1, 2015
Priority date	Apr 1, 2014
Publication date	Sep 11, 2018
Grant date	Sep 11, 2018

Abstract

A hydrostatic traction drive in a closed hydraulic circuit includes two hydraulic machines in the closed hydraulic circuit and a control unit configured to control a braking torque of the traction drive. A method for controlling the hydrostatic traction drive includes controlling the braking torque for the hydrostatic traction drive.

First claim

What is claimed is:

1. A hydrostatic traction drive, comprising:
a first hydraulic machine with a variable displacement volume, the first hydraulic machine configured to be coupled to a drive machine;
a second hydraulic machine with a variable displacement volume, the second hydraulic machine configured to be coupled to a wheel to be driven or to a chain or axle to be driven, the first and second hydraulic machines fluidically connected by a first branch line and a second branch line; and
a control unit configured to:
determine an overrun mode of the traction drive depending on a measured actual value of a revolution rate of the second hydraulic machine and on a calculated theoretical value of the revolution rate of the second hydraulic machine, the theoretical value calculated based on a measured actual value of a revolution rate of the first hydraulic machine;
control a braking torque of the traction drive depending on the determined overrun mode;
in response to determining that the traction drive is in the overrun mode, reduce the displacement volume of the first hydraulic machine and the displacement volume of the second hydraulic machine, such that a ratio between the displacement volume of the first hydraulic machine and the displacement volume of the second hydraulic machine is maintained, until the traction drive is in a neutral drive state; and
in response to the traction drive entering the neutral drive state, increase the displacement volume of the second hydraulic machine.

2. The traction drive according to claim 1 , wherein the braking torque is configured to be produced by restricting a partial flow of a return volumetric flow directed from the second hydraulic machine to the first hydraulic machine.

3. The traction drive according to claim 2 , further comprising a hydraulic restriction mechanism having a pressure medium input and a pressure medium output, the pressure medium input fluidically connected to a branch line and the pressure medium output fluidically connected to a pressure medium sink of the traction drive.

4. The traction drive according to claim 1 , wherein the control unit is configured to determine the overrun mode based on the actual value of the revolution rate of the second hydraulic machine deviating from the theoretical value of the revolution rate by more than a predetermined threshold amount.

5. The traction drive according to claim 4 , wherein the control unit is further configured to determine the overrun mode based on an actual value of a revolution rate of the drive machine deviating from a target value for the drive machine by more than a predetermined threshold.

6. The traction drive according to claim 1 , wherein the theoretical value is a theoretical loss-free value of revolution speed for the second hydraulic machine.

7. The traction drive according to claim 1 , wherein the control unit is further configured to determine the theoretical value depending on a ratio of actual values of displacement volumes of the hydraulic machines.

8. The traction drive according to claim 1 , wherein the control unit is configured to determine for at least one of the hydraulic machines an actual value of its displacement volume depending on a target value of its displacement volume.

9. The traction drive according to claim 8 , wherein a characteristic field of the actual value of the displacement volume is stored in the control unit as a function of the target value of the displacement volume.

10. The traction drive according to claim 1 , further comprising one or more of (i) a first revolution rate detection unit configured to detect the measured actual value of the revolution rate of the first hydraulic machine or a revolution rate that is configured to be derived therefrom and (ii) a second revolution rate detection unit configured to detect the actual value of the revolution rate of the second hydraulic machine.

11. A method for controlling a braking torque of a hydrostatic traction drive including a first hydraulic machine with a variable displacement volume and a second hydraulic machine with a variable displacement volume, the method comprising:
determining an overrun mode of the traction drive depending on a measured actual value of a revolution rate of the second hydraulic machine and on a calculated theoretical value of the revolution rate, the theoretical value calculated based on a measured actual value of a revolution rate of the first hydraulic machine;
controlling the braking torque depending on the determined overrun mode;
in response to determining that the traction drive is in the overrun mode, reducing the displacement volume of the first hydraulic machine and the displacement volume of the second hydraulic machine, such that a ratio between the displacement volume of the first hydraulic machine and the displacement volume of the second hydraulic machine is maintained, until the traction drive is in a neutral drive state; and
in response to the traction drive entering the neutral drive state, increasing the displacement volume of the second hydraulic machine.

12. The method according to claim 11 , wherein determining the overrun mode of the traction drive includes:
determining that a deviation of the actual value of the revolution rate of the second hydraulic machine from the theoretical value of the revolution rate is greater than a predetermined threshold amount.

13. The method according to claim 12 , wherein determining the overrun mode of the traction drive further includes, prior to the determining that a deviation of the actual value of the revolution rate of the second hydraulic machine from the theoretical value of the revolution rate is greater than the predetermined threshold amount:
measuring the actual value of the revolution rate of the second hydraulic machine, and
calculating the theoretical value of the revolution rate.

14. The method according to claim 13 , wherein calculation of the theoretical value of the revolution rate is further based on a ratio of actual values of displacement volumes of the hydraulic machines.

15. The method according to claim 12 , wherein determining the overrun mode of the traction drive further includes:
determining that a deviation of an actual value of a revolution rate of the drive machine from a target value for the drive machine is more than a predetermined threshold.

16. The method according to claim 11 , wherein controlling the braking torque depending on the determined overrun mode includes:
adjusting at least one of the displacement volumes of the hydraulic machines.

Assignees

• Bosch Gmbh Robert

Inventors

• Behm Martin

Classifications

• F16H61/4157

  Control of braking, e.g. preventing pump over-speeding when motor acts as a pump · CPC title

• B60T1/08

  using fluid or powdered medium · CPC title

• F16H61/40 Primary

  hydrostatic · CPC title

• B60T13/585

  comprising friction brakes and retarders · CPC title

• F16H61/42

  involving adjustment of a pump or motor with adjustable output or capacity · CPC title