Method and apparatus for recovering inertial energy

• US 9,963,855 B2
• Filed: 08/10/2012
• Issued: 05/08/2018
• Est. Priority Date: 08/12/2011
• Status: Active Grant

• Current Assignee: Danfoss A/S
• Original Assignee: Eaton Intelligent Power Limited (Eaton Corporation PLC.)
• Inventors: Jagoda, Aaron Hertzel
• Primary Examiner(s): Leslie, Michael
• Assistant Examiner(s): Wiblin, Matthew
• Application Number:
  US13/572,115
• Publication Number:
  US 20130061588A1
• Time in Patent Office: 2,097 Days
• CPC Class Codes: B60K 6/12 by means of a chargeable fluidic accumulator
• CPC Class Codes: B66C 13/28 utilising regenerative braking for controlling descent of heavy loads and having means for preventing rotation of motor in the hoisting direction when load is released
• CPC Class Codes: E02F 9/128 Braking systems
• CPC Class Codes: E02F 9/2004 Control mechanisms, e.g. control levers control levers per se G05G
• CPC Class Codes: E02F 9/2025 Particular purposes of control systems not otherwise provided for E02F3/16, E02F3/26, sub-groups of E02F3/43, E02F3/651, sub-groups of E02F3/84, E02F3/907, E02F5/145 take precedence
• CPC Class Codes: E02F 9/2217 with energy recovery arrangements, e.g. using accumulators, flywheels
• CPC Class Codes: E02F 9/2267 Valves or distributors position of valves arrangements on upper-structures E02F9/0875
• CPC Class Codes: F15B 1/024 used as a supplementary power source, e.g. to store energy in idle periods to balance pump load
• CPC Class Codes: F16H 61/4096 with pressure accumulators
• CPC Class Codes: F16H 61/4148 Open loop circuits
• CPC Class Codes: Y02T 10/62 Hybrid vehicles

Abstract

A hydraulic system adapted to recover inertial energy is disclosed. The hydraulic system includes a pump, a variable displacement pump/motor having an input/output shaft, an accumulator, and a valve arrangement. The valve arrangement is operable in: a) a first mode where the variable displacement pump/motor is driven by the pump to rotate the input/output shaft and the load; b) a second mode where the variable displacement pump/motor uses inertial energy from a deceleration of the load to charge the accumulator; and c) a third mode where the variable displacement pump/motor is driven by the accumulator to rotate the input/output shaft and the load. The hydraulic system also includes a controller for controlling operation of the pump, the variable displacement pump/motor and the valve arrangement.

Claims

1. A hydraulic system adapted to recover inertial energy, the hydraulic system comprising:

a pump;

a variable displacement pump/motor having an input/output shaft adapted for connection to a load;

an accumulator having a charging state and a fully charged state;

at least one pressure relief valve having pressure relief settings, the at least one pressure relief valve being adapted to limit a differential pressure across the variable displacement pump/motor when a set pressure is exceeded;

the variable displacement pump/motor being operable in;

a) a first mode where the variable displacement pump/motor is driven by the pump to rotate the input/output shaft and the load;

b) a second mode where the variable displacement pump/motor uses inertial energy from a deceleration of the load to charge the accumulator;

c) a third mode where the variable displacement pump/motor is driven by the accumulator to rotate the input/output shaft and the load; and

d) a fourth mode where the variable displacement pump/motor dumps inertial energy from a deceleration of the load on the at least one pressure relief valve when the accumulator is in the fully charged state;

a controller for controlling operation of the pump and the variable displacement pump/motor, the controller controlling the variable displacement pump/motor to control a torque transferred through the input/output shaft of the variable displacement pump/motor;

an operator interface for inputting a torque control signal to the controller for controlling a direction of rotation of the input/output shaft and for controlling a speed of rotation of the input/output shaft; and

memory storing a control model including a three-dimensional control map that defines a relationship between a value of the torque control signal, a sensed rotational speed of the input/output shaft of the variable displacement pump/motor, and a torque command that establishes an amount of torque to be transferred through the input/output shaft of the variable displacement pump/motor, the controller using the control model to determine the amount of torque to be transferred through the input/output shaft, the three-dimensional control map including a three-dimensional control map surface defined along first, second and third axes that are perpendicular to one another, the first axis corresponding to the torque command, the second axis corresponding to the torque control signal and the third axis corresponding to the sensed rotational speed of the input/output shaft; and

wherein the pressure relief settings of the at least one pressure relief valve define a top horizontal plane of the control map surface and a bottom horizontal plane of the control map surface, wherein the top horizontal plane corresponds to a torque command establishing a maximum clockwise torque, and wherein the bottom horizontal plane corresponds to a torque command establishing a maximum counterclockwise torque.

2. The hydraulic system of claim 1, wherein the variable displacement pump/motor includes a swash plate, and wherein the controller controls a position of the swash plate to control a torque transferred through the input/output shaft of the variable displacement pump/motor during braking.

3. The hydraulic system of claim 2, wherein the swash plate is an over-the-center swash plate.

4. The hydraulic system of claim 1, wherein the controller interfaces with a speed sensor that senses the rotational speed of the input/output shaft.

5. The hydraulic system of claim 1, wherein the controller interfaces with a pressure sensor arrangement that senses a pressure differential across the variable displacement pump/motor.

6. The hydraulic system of claim 1, further comprising a pressure sensor for sensing a charge pressure of the accumulator, wherein the controller only shifts the valve arrangement to the third mode when the charge pressure is greater than a pre-determined threshold charge pressure.

7. The hydraulic system of claim 1, wherein the variable displacement pump/motor pivots an upper structure of an excavator about a swing axis relative to an undercarriage of the excavator, and wherein the upper structure includes an excavation boom.

8. The hydraulic system of claim 7, wherein the pump also drives a hydraulic cylinder used to pivot the excavation boom up and down.

9. The hydraulic system of claim 8, wherein the pump also drives a hydraulic motor powering a track of the undercarriage.

10. The hydraulic system of claim 1, wherein the variable displacement pump/motor includes a swash plate, and wherein the controller adjusts a position of the swash plate to alter a torque applied through the input/output shaft in response to a value of the torque control signal.

11. The hydraulic system of claim 1, wherein the torque control signal is generated by a joystick.

12. The hydraulic system of claim 1, wherein the three-dimensional map surface includes a sloped surface or surfaces between the top and bottom horizontal planes that correspond to torque commands establishing transitional torque values between the maximum clockwise and counterclockwise torques.

13. The hydraulic system of claim 1, wherein the controller and the control model provide means for emulating a base line system.

14. The hydraulic system of claim 1, wherein the controller uses a negative flow control pump control strategy to control the pump.

15. The hydraulic system of claim 14, wherein the controller and the control model provide means for emulating a conventional fluid system that uses a negative flow control pump control strategy.

16. A hydraulic swing drive for use on an excavating machine, the hydraulic swing drive urging acceleration and deceleration on an excavating structure of the excavating machine, the hydraulic swing drive comprising:

a hydraulic pump producing a pump pressure of hydraulic fluid in a pump supply line;

an accumulator with hydraulic fluid under an accumulator pressure, the accumulator in fluid communication with an accumulator line, the accumulator having a charging state and a fully charged state;

a tank with hydraulic fluid in fluid communication with a tank line;

a variable displacement pump/motor selectively urging the acceleration and the deceleration on the excavating structure, the variable displacement pump/motor in fluid communication with a first line and a second line of the variable displacement pump/motor, the variable displacement pump/motor including a swash plate; and

a valve arrangement selectively connecting the accumulator line with the first line of the variable displacement pump/motor and selectively connecting the tank line with the second line of the variable displacement pump/motor when the accumulator pressure is greater than a threshold pressure and the acceleration of the excavating structure is requested, the valve arrangement selectively connecting the pump supply line with the first line of the variable displacement pump/motor and selectively connecting the tank line with the second line of the variable displacement pump/motor when the accumulator pressure is less than or equal to the threshold pressure and the acceleration of the excavating structure is requested, and the valve arrangement selectively connecting the accumulator line with the second line of the variable displacement pump/motor and selectively connecting the tank line with the first line of the variable displacement pump/motor when the deceleration of the excavating structure is requested and accumulator charging is desired;

the swing drive being operable in a first state in which a controller controls a position of the swash plate to selectively increase and decrease a rate of deceleration of the excavation structure without throttling, and the swing drive also being operable in a second state in which the variable displacement pump/motor dumps inertial energy from a deceleration of the excavating structure on at least one pressure relief valve when the accumulator is in the fully charged state.

17. The hydraulic swing drive of claim 16, wherein the variable displacement pump/motor is an over-center variable displacement pump/motor.

18. The hydraulic swing drive of claim 17, further comprising a controller and an operator interface, the operator interface generating an acceleration request signal when the acceleration of the excavating structure is requested, the operator interface generating a deceleration request signal when the deceleration of the excavating structure is requested, the controller receiving the acceleration and the deceleration request signals, and the controller sending at least one valve signal to the valve arrangement when the controller receives the acceleration or the deceleration request signals.

19. A hydraulic system adapted to recover inertial energy, the hydraulic system comprising:

a pump;

a variable displacement pump/motor having an input/output shaft adapted for connection to a load;

an accumulator;

at least one pressure relief valve having pressure relief settings;

a valve arrangement operable in;

a) a first mode where the variable displacement pump/motor is driven by the pump to rotate the input/output shaft and the load;

b) a second mode where the variable displacement pump/motor uses inertial energy from a deceleration of the load to charge the accumulator; and

c) a third mode where the variable displacement pump/motor is driven by the accumulator to rotate the input/output shaft and the load;

a controller for controlling operation of the pump, the variable displacement pump/motor and the valve arrangement, the controller controlling the variable displacement pump/motor to control a torque transferred through the input/output shaft of the variable displacement pump/motor;

an operator interface for inputting a torque control signal to the controller for controlling a direction of rotation of the input/output shaft and for controlling a speed of rotation of the input/output shaft, wherein when the torque control signal corresponds to a deceleration command, the controller shifts the valve arrangement to the second mode, and wherein the variable displacement pump/motor provides a pumping and braking function when the valve arrangement is in the second mode; and

memory storing a control model including a three-dimensional control map that defines a relationship between a value of the torque control signal, a sensed rotational speed of the input/output shaft of the variable displacement pump/motor, and a torque command that establishes an amount of torque to be transferred through the variable displacement pump/motor, the controller using the control model to determine the amount of torque to be transferred through the input/output shaft, the three-dimensional control map including a three-dimensional control map surface defined along first, second and third axes that are perpendicular to one another, the first axis corresponding to the torque command, the second axis corresponding to the torque control signal and the third axis corresponding to the sensed rotational speed of the input/output shaft;

wherein the pressure relief settings of the at least one pressure relief valve define a top horizontal plane of the control map surface and a bottom horizontal plane of the control map surface, wherein the top horizontal plane corresponds to a torque command establishing a maximum clockwise torque, and wherein the bottom horizontal plane corresponds to a torque command establishing a maximum counterclockwise torque; and

wherein the valve arrangement includes a three-position directional flow control valve and a return flow control valve, wherein in the first mode the directional flow control valve places an outlet side of the pump in fluid communication with a first side of the variable displacement pump/motor and the return flow control valve places a second side of the variable displacement pump/motor in fluid communication with a tank, wherein in the second mode the directional flow control valve blocks fluid communication between the pump and the first side of the variable displacement pump/motor and the return flow control valve blocks fluid communication between the second side of the variable displacement pump/motor and the tank, and wherein in the third mode the directional flow control valve places the accumulator in fluid communication with the first side of the variable displacement pump/motor and the return flow control valve places the second side of the variable displacement pump/motor in fluid communication with the tank.

20. The hydraulic system of claim 19, wherein in the second mode a first check valve allows fluid communication between the tank and the first side of the variable displacement pump/motor and a second check valve allows fluid communication between the second side of the variable displacement pump/motor and the accumulator.

21. The hydraulic system of claim 19, further comprising first and second parallel flow lines that cross-connect the first and second sides of the variable displacement pump/motor, the first flow line including two pressure relief valves and the second flow line including two check valves, the first and second flow lines being fluidly connected to each other at locations between the check valves and between the pressure relief valves.

22. The hydraulic system of claim 21, further comprising a tank line that by-passes the return flow control valve and connects to the second line between the check valves.

23. A hydraulic system adapted to recover inertial energy, the hydraulic system comprising:

a variable displacement pump/motor having an input/output shaft adapted for connection to a load;

a controller for controlling the variable displacement pump/motor, the controller controlling the variable displacement pump/motor to control a torque transferred through the input/output shaft of the variable displacement pump/motor;

memory storing a control model including a three-dimensional control map that defines a relationship between a value of the torque control signal, a sensed rotational speed of the input/output shaft of the variable displacement pump/motor, and a torque command that establishes an amount of torque to be transferred through the variable displacement pump/motor, the controller using the control model to determine the amount of torque to be transferred through the input/output shaft, the three-dimensional control map including a three-dimensional control map surface defined along first, second and third axes that are perpendicular to one another, the first axis corresponding to the torque command, the second axis corresponding to the torque control signal and the third axis corresponding to the sensed rotational speed of the input/output shaft;

at least one pressure relief valve, the at least one pressure relief valve being adapted to limit a differential pressure across the variable displacement pump/motor when a set pressure is exceeded; and

an accumulator, the accumulator having a charging state and a fully charged state;

wherein a deceleration of the load charges the accumulator when the accumulator is in the charging state; and

wherein the variable displacement pump/motor is configured to dump inertial energy from a deceleration of the load on the at least one pressure relief valve when the accumulator is in the fully charged state.

24. The hydraulic system of claim 23, wherein a portion of the three-dimensional control map corresponds to generating a signal by the controller for decelerating the input/output shaft.