Hydrostatic transmission and method for braking using the same

Patent metadata

Field	Value
Publication number	US-10753469-B2
Application number	US-201815894769-A
Country	US
Kind code	B2
Filing date	Feb 12, 2018
Priority date	Feb 14, 2017
Publication date	Aug 25, 2020
Grant date	Aug 25, 2020

Abstract

A hydrostatic transmission for a traction drive of a mobile working machine includes a variable-displacement pump and one or more motors connected to one another in a closed hydraulic circuit. An electronic control unit of the hydrostatic transmission is configured to initiate and to end a braking operation by the hydrostatic transmission if a traveling speed of the mobile working machine reaches a threshold value. The threshold value is adjustable by the electronic control unit automatically or in a manner dependent on a driver demand. The braking torque is also adjustable.

First claim

What is claimed is:

1. A hydrostatic transmission for a traction drive of a mobile working machine, comprising:
a primary unit including a driveshaft coupled to an internal combustion engine of the traction drive;
at least one secondary unit coupled to an output of the traction drive;
two working lines of a closed circuit each configured to fluidically connect the primary unit and the at least one secondary unit; and
an electrical control unit configured to control an adjustable pivot angle or an adjustable swept volume of the primary unit during a braking operation of the hydrostatic transmission,
wherein the electrical control unit is further configured to automatically initiate the braking operation if an actual traveling speed of the mobile working machine or a variable derived from the former reaches an activation threshold of the traveling speed or an activation threshold derived from the former, and
wherein the activation threshold is variable or adjustable, and
further comprising:
a first pressure-limiting valve arranged on a first working line of the two working lines; and
a second pressure-limiting valve arranged on a second working line of the two working lines,

wherein the braking operation is a high-power braking operation in which a first part of the braking power is dissipated via one of the first and the second pressure-limiting valves, while a second part of the braking power is dissipated via the primary unit, and
wherein the first and second pressure-limiting valves each have a flat characteristic curve with regard to their pressure difference as a function of their passed-through volume flow.

2. The hydrostatic transmission according to claim 1 , wherein the activation threshold is adjustable based on a driver demand.

3. The hydrostatic transmission according to claim 2 , wherein the activation threshold is equal to a sum of a setpoint rotational speed, derived from the driver demand, of the at least one secondary unit and an added-on value.

4. The hydrostatic transmission according to claim 3 , wherein:
the braking operation is automatically ended as a result of a decrease of the actual traveling speed of the mobile working machine or of the variable derived from the former below a deactivation threshold of the traveling speed or a deactivation threshold derived from the former, and
the deactivation threshold is variable or adjustable.

5. The hydrostatic transmission according to claim 4 , wherein the deactivation threshold is equal to a sum of the setpoint rotational speed, derived from the driver demand, of the at least one secondary unit and another added-on value.

6. The hydrostatic transmission according to claim 1 , wherein the electrical control unit is further configured such that the braking operation is automatically initiated and ended based on automatic monitoring of an actual rotational speed of the internal combustion engine or of a variable derived from the former.

7. The hydrostatic transmission according to claim 1 , wherein the electrical control unit is further configured to control an adjustable pivot angle or an adjustable swept volume of the at least one secondary unit during the braking operation.

8. The hydrostatic transmission according to claim 1 , wherein a braking torque is variable or adjustable during the braking operation.

9. The hydrostatic transmission according to claim 8 , wherein the braking torque is controllable, or controllable in closed-loop fashion, in a manner dependent on a difference between the actual traveling speed or the variable derived from the former and a setpoint traveling speed or a variable derived from the former.

10. The hydrostatic transmission according to claim 8 , wherein the braking torque is controllable, or controllable in closed-loop fashion, in a manner dependent on a difference between the actual traveling speed or the variable derived from the former and a maximum traveling speed or a variable derived from the former.

11. The hydrostatic transmission according to claim 1 , wherein the pivot angle and the swept volume of the primary unit are adjustable in both directions from a zero position.

12. A method for closed-loop control of a braking operation with a hydrostatic transmission for a traction drive of a mobile working machine, comprising:
determining an activation threshold of a traveling speed or of the activation threshold derived from the former;
attaining an actual traveling speed or a variable, derived from the former, of the activation threshold; and
automatically initiating a braking operation of the hydrostatic transmission using an electrical control unit,
wherein the hydrostatic transmission includes
a primary unit including a driveshaft coupled to an internal combustion engine of the traction drive,
at least one secondary unit coupled to an output of the traction drive,
two working lines of a closed circuit each configured to fluidically connect the primary unit and the at least one secondary unit, and
the electrical control unit,

wherein the electrical control unit is further configured to control an adjustable pivot angle or an adjustable swept volume of the primary unit during the braking operation of the hydrostatic transmission, and
wherein the activation threshold is adjustable based on a driver demand, and
wherein the activation threshold is equal to a sum of a setpoint rotational speed, derived from the driver demand, of the at least one secondary unit and an added-on value.

13. The method according to claim 12 , further comprising:
determining a deactivation threshold of the traveling speed or of the deactivation threshold derived from the former;
attaining the actual traveling speed or the variable, derived from the former, of the deactivation threshold; and
automatically ending the braking operation of the hydrostatic transmission using the electrical control unit.

14. A hydrostatic transmission for a traction drive of a mobile working machine, comprising:
a primary unit including a driveshaft coupled to an internal combustion engine of the traction drive;
at least one secondary unit coupled to an output of the traction drive;
two working lines of a closed circuit each configured to fluidically connect the primary unit and the at least one secondary unit; and
an electrical control unit configured to control an adjustable pivot angle or an adjustable swept volume of the primary unit during a braking operation of the hydrostatic transmission,
wherein the electrical control unit is further configured to automatically initiate the braking operation if an actual traveling speed of the mobile working machine or a variable derived from the former reaches an activation threshold of the traveling speed or an activation threshold derived from the former, and
wherein the activation threshold is adjustable based on a driver demand, and
wherein the activation threshold is equal to a sum of a setpoint rotational speed, derived from the driver demand, of the at least one secondary unit and an added-on value.

Assignees

• Bosch Gmbh Robert

Inventors

• Witte Heiko
• Behm Martin

Classifications

• F16H59/44

  dependent on machine speed {, e.g. the vehicle speed} (F16H59/46 takes precedence) · CPC title

• F16H2059/366

  Engine or motor speed · CPC title

• F16H61/435

  Pump capacity control by electric actuators · CPC title

• F16H61/425

  Motor capacity control by electric actuators · CPC title

• F16H59/18

  dependent on the position of the accelerator pedal · CPC title