Powertrain system with variator speed balancing

Patent metadata

Field	Value
Publication number	US-10036460-B2
Application number	US-201615375340-A
Country	US
Kind code	B2
Filing date	Dec 12, 2016
Priority date	Dec 12, 2016
Publication date	Jul 31, 2018
Grant date	Jul 31, 2018

Abstract

A powertrain system for a machine includes a hydraulic variator assembly coupled with a mechanical transmission, and a speed balancing system including a hydraulic accumulator, and being configured to limit a speed balancing error between first and second variators in the variator assembly by commanding adjustment of a valve mechanism to fluidly connect a hydraulic accumulator with one of the variators to increase a fluid flow rate therethrough. The hydraulic accumulator can be charged by way of an implement system in a machine driven by way of the powertrain system.

First claim

What is claimed is:

1. A powertrain system for a machine comprising:
a mechanical transmission including a planetary gear set coupled between an input shaft and an output shaft;
a hydraulic variator assembly including a first variator and a second variator, and transmission input gearing coupling the first variator and the second variator with the planetary gear set, and each of the first variator and the second variator including a respective pump and motor and operating at a speed that is dependent upon a rate of flow of hydraulic fluid between the respective pump and motor; and
a speed balancing system for the hydraulic variator assembly including a hydraulic accumulator, an electronically controlled valve mechanism fluidly connected between the hydraulic accumulator and each of the first variator and the second variator, and a control mechanism;
the electronically controlled valve mechanism being in a first state where the hydraulic accumulator is blocked from fluid communication with either of the first variator or the second variator, and adjustable to a second state at which the valve mechanism fluidly connects the hydraulic accumulator to the second variator but not the first variator; and
the control mechanism being configured to limit a speed balancing error between the first variator and the second variator at least in part by commanding adjustment of the valve mechanism to the second state, such that a speed of the second variator is adjusted according to a flow of hydraulic fluid between the second variator and the hydraulic accumulator that varies the rate of flow between the corresponding pump and motor.

2. The system of claim 1 wherein the control mechanism is further configured to receive data indicative of a difference, in speeds of the motor in the first variator and the motor in the second variator, that defines the speed balancing error, and to command the adjustment to the valve mechanism based on the speed balancing error such that a flow of fluid, from the hydraulic accumulator to the motor in the second variator, increases the speed of the motor in the second variator.

3. The system of claim 2 wherein the transmission input gearing includes a differential coupled between the motor in the first variator and the motor in the second variator.

4. The system of claim 2 wherein each of the first variator and the second variator includes hydraulic circuitry fluidly connecting the corresponding pump and motor, and wherein the speed balancing system includes a first hydraulic line fluidly connecting to the hydraulic circuitry of the first variator at a location fluidly between the corresponding pump and motor, and a second hydraulic line fluidly connecting to the hydraulic circuitry of the second variator at a location fluidly between the corresponding pump and motor.

5. The system of claim 4 wherein the valve mechanism includes a third state where the valve mechanism fluidly connects the hydraulic accumulator to the first variator by way of the first hydraulic line.

6. The system of claim 4 further comprising a hydraulic implement actuator fluidly connected to the hydraulic accumulator, and wherein the valve mechanism fluidly connects the hydraulic implement actuator with the hydraulic accumulator in the first state.

7. The system of claim 1 wherein each of the first variator and the second variator has a variable displacement and includes a pump displacement actuator.

8. The system of claim 7 wherein the control mechanism is further configured to determine and re-determine a closed loop control term indicative of an error in a position of the pump displacement actuator in the second variator, and to successively command adjustments to the position of the pump displacement actuator based on the determined and re-determined closed loop control term.

9. The system of claim 8 wherein the control mechanism is further configured to determine an open loop control term based on the speed balancing error, and to command the adjustment of the valve mechanism based on the determined open loop control term.

10. A method of operating a powertrain system in a machine, the method comprising:
conveying hydraulic fluid between a pump and a motor in each of a first variator and a second variator in a hydraulic variator assembly coupled with a mechanical transmission;
transferring torque from the motor in each of the first variator and the second variator to a planetary gear set in the mechanical transmission;
transferring torque between the motor in the first variator and the motor in the second variator;
establishing a flow of hydraulic fluid between the second variator and a hydraulic accumulator such that a rate of flow of the hydraulic fluid between the pump and the motor in the second variator is varied;
reducing a speed difference between the first variator and the second variator by way of varying of the rate of flow, such that the transferring of the torque between the motor in the first variator and the motor in the second variator is limited.

11. The method of claim 10 further comprising charging the hydraulic accumulator from a hydraulic implement actuator in an implement system of the machine.

12. The method of claim 10 further comprising determining a control term indicative of an error in a position of a displacement actuator in the pump of the second variator, and commanding adjusting the position of the displacement actuator based on the control term.

13. The method of claim 10 further comprising determining a control term based on the speed difference, and commanding adjusting a valve mechanism positioned fluidly between the hydraulic accumulator and the second variator according to the control term so as to establish the flow of hydraulic fluid.

14. The method of claim 10 wherein the transferring of the torque from the motor in each of the first variator and the second variator to the planetary gear set includes transferring the torque by way of a differential.

15. The method of claim 10 wherein the establishing of the flow of hydraulic fluid includes establishing a flow of hydraulic fluid from the hydraulic accumulator to hydraulic circuitry fluidly connecting the pump and the motor of the second variator.

16. The method of claim 15 wherein the reducing of the speed difference includes reducing the speed difference by way of increasing a speed of the second variator.

17. A control system for balancing speeds of a first variator and a second variator in a hydraulic variator assembly coupled with a planetary gear set in a mechanical transmission of a powertrain system, the control system comprising:
an electrical actuator configured to couple with a valve mechanism positionable fluidly between a hydraulic accumulator and each of the first variator and the second variator in the hydraulic variator system;
a control mechanism coupled with the electrical actuator, and being configured to vary an electrical energy state of the electrical actuator to adjust the valve mechanism between a first state where the hydraulic accumulator is blocked from fluid communication with either of the first variator or the second variator, and a second state at which the valve mechanism fluidly connects the hydraulic accumulator to the second variator but not the first variator; and
the control mechanism being configured to limit a speed balancing error between the first variator and the second variator at least in part by commanding the adjustment of the valve mechanism to the second state to produce a flow of hydraulic fluid between the second variator and the hydraulic

Assignees

• Caterpillar Inc

Inventors

• Ge Xinyu

Classifications

• F16H61/4035

  Control of circuit flow · CPC title

• F16H2047/045

  the fluid gearing comprising a plurality of pumps or motors · CPC title

• F16H61/4148

  Open loop circuits · CPC title

• F16H47/04 Primary

  the mechanical gearing being of the type with members having orbital motion · CPC title

• F16H61/4096

  with pressure accumulators · CPC title