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US-20260125877-A1 - WORKING MACHINE

US20260125877A1US 20260125877 A1US20260125877 A1US 20260125877A1US-20260125877-A1

Abstract

A working machine may include a tank; a working device including an actuator; an accumulator; a recovery path connecting the actuator and the accumulator; a return valve installed between the recovery path and the tank to control the flow rate of fluid discharged from the recovery path to the tank; a command generating device that generates a command; and a control unit that receives the command from the command generating device and controls the return valve so that the return valve has an opening amount corresponding to the command according to a preset relationship, thereby adjusting the operating speed of the actuator and the charging speed of the accumulator. The command generating device may be a first operator input device that receives a request from an operator for one of the operating speed of the actuator, the charging speed of the accumulator, and the opening amount of the return valve.

Inventors

  • Jinwoo KO
  • Sangseok KANG

Assignees

  • VOLVO CONSTRUCTION EQUIPMENT AB

Dates

Publication Date
20260507
Application Date
20251031
Priority Date
20241107

Claims (20)

  1. 1 . A working machine comprising: a tank, a working device including an actuator; an accumulator; a recovery path connecting the actuator and the accumulator; a return valve installed between the recovery path and the tank to control the flow rate of fluid discharged from the recovery path to the tank; a command generating device that generates a command; a control unit that receives the command from the command generating device and controls the return valve so that the return valve has an opening amount corresponding to the command according to a preset relationship, thereby adjusting the operating speed of the actuator and the charging speed of the accumulator.
  2. 2 . The working machine of claim 1 , wherein the command generating device is a first operator input device that receives a request from an operator for one of the operating speed of the actuator, the charging speed of the accumulator, and the opening amount of the return valve, and wherein the control unit controls the opening amount of the return valve according to the request.
  3. 3 . The working machine of claim 2 , wherein the first operator input device selectively receives, from the operator, at least a request for a first operating speed and a request for a second operating speed of the actuator and the second operating speed is faster than the first operating speed, and wherein the control unit controls the return valve to have a first opening amount according to the request for the first operating speed and controls the return valve to have a second opening amount according to the request for the second operating speed, wherein the second opening amount is larger than the first opening amount.
  4. 4 . The working machine of claim 3 , wherein, as the requested operating speed input to the first operator input device becomes faster, the control unit controls the return valve so that the return valve has a larger opening amount.
  5. 5 . The working machine of claim 1 , wherein the command generating device is a sensor that detects the position of a predetermined portion of the working device, and wherein the control unit controls the opening amount of the return valve according to the position of the predetermined portion of the working device detected by the sensor.
  6. 6 . The working machine of claim 5 , wherein the predetermined portion of the working device is a bucket.
  7. 7 . The working machine of claim 5 , wherein the control unit at least controls the return valve to have a third opening amount when the predetermined portion of the working device is at a third position, and controls the return valve to have a fourth opening amount when the predetermined portion of the working device is at a fourth position, wherein the fourth position is at lower height than the third position and the fourth opening amount is larger than the third opening amount.
  8. 8 . The working machine of claim 7 , wherein, as the position of the predetermined portion of the working device detected by the sensor becomes lower, the control unit controls the return valve so that the return valve has a larger opening amount.
  9. 9 . The working machine of claim 7 , wherein the third position and the fourth position are positions lower than the preset reference height.
  10. 10 . The working machine of claim 9 , wherein the reference height is the floor height of the working machine, and the third position and the fourth position are positions lower than the floor of the working machine.
  11. 11 . The working machine of claim 9 , wherein, when the predetermined portion of the working device is at a position higher than or equal to the reference height, the control unit controls the return valve so that the return valve has a constant opening amount, and wherein the constant opening amount is smaller than both the third opening amount and the fourth opening amount.
  12. 12 . The working machine of claim 1 , wherein the actuator is a boom actuator, wherein the working machine further includes a second operator input device that receives a request for raising/lowering the boom of the boom actuator from an operator, and wherein the flow of fluid from the boom actuator to the recovery path only occurs when a boom down request to lower the boom is input to the second operator input device.
  13. 13 . The working machine of claim 12 , further comprising a third operator input device for receiving an energy recovery function activation request from an operator to activate an energy recovery function for recovering energy from fluid discharged from the boom actuator, wherein the flow of fluid from the boom actuator to the recovery path only occurs when the energy recovery function activation request is input to the third operator input device.
  14. 14 . The working machine of claim 13 , further comprising a directional control valve installed between the boom actuator and the tank to selectively discharge fluid from the boom actuator to the tank, wherein, when the energy recovery function activation request is input to the third operator input device and the boom down request is input to the second operator input device, the directional control valve prevents fluid from being discharged from the boom actuator to the tank.
  15. 15 . The working machine of claim 13 , further comprising a pump that draws and pressurizes fluid from the tank, and a directional control valve installed between the pump and the boom actuator to selectively supply pressurized fluid from the pump to the boom actuator, wherein, when the energy recovery function activation request is input to the third operator input device and the boom down request is input to the second operator input device, the directional control valve prevents pressurized fluid from being supplied from the pump to the boom actuator.
  16. 16 . The working machine of claim 13 , further comprising a directional control valve installed between the boom actuator and the tank to selectively discharge fluid from the boom actuator to the tank, wherein, when the boom down request is input to the second operator input device while the energy recovery function activation request is not input to the third operator input device, the directional control valve causes fluid to be discharged from the boom actuator to the tank.
  17. 17 . The working machine of claim 13 , further comprising a pump that draws and pressurizes fluid from the tank, and a directional control valve installed between the pump and the boom actuator to selectively supply pressurized fluid from the pump to the boom actuator, wherein, when the boom down request is input to the second operator input device while the energy recovery function activation request is not input to the third operator input device, the directional control valve causes pressurized fluid to be supplied from the pump to the boom actuator.
  18. 18 . The working machine of claim 1 , wherein the actuator is a boom actuator having a bottom chamber and a load chamber, wherein the recovery path is connected to the bottom chamber.
  19. 19 . The working machine of claim 1 , further comprising an assist motor connected to the accumulator.
  20. 20 . The working machine of claim 1 , wherein the actuator is a boom actuator, wherein the operating speed of the actuator is the speed at which the boom of the boom actuator is lowered.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application claims priority to Korean Patent Application No. 10-2024-0157190, filed on Nov. 7, 2024, the disclosure and content of which is incorporated by reference herein in its entirety. TECHNICAL FIELD The present disclosure relates to a working machine, and more particularly, to a working machine capable of efficiently increasing the operating speed of a working device while efficiently recovering energy discharged from a boom actuator. BACKGROUND A working machine is a device that performs work by supplying high-pressure pressurized fluid to (an actuator of) a working device. To improve the fuel efficiency of such working machines, a technology has been proposed that recovers energy from the fluid discharged from the boom actuator. However, since energy recovery efficiency and the operating speed of the working device are in a trade-off relationship, there was a limitation that increasing the energy recovery efficiency would slow down the operating speed of the working device, and conversely, increasing the operating speed of the working device would lower the energy recovery efficiency. SUMMARY According to a first aspect of the present disclosure, there is provided a working machine comprising: a tank; a working device including an actuator; an accumulator; a recovery path connecting the actuator and the accumulator; a return valve installed between the recovery path and the tank to control the flow rate of fluid discharged from the recovery path to the tank; a command generating device that generates a command; and a control unit that receives the command from the command generating device and controls the return valve so that the return valve has an opening amount corresponding to the command according to a preset relationship, thereby adjusting the operating speed of the actuator and the charging speed of the accumulator. This working machine has an advantage of efficiently increasing the operating speed of the working device while efficiently recovering the energy discharged from the boom actuator. According to some embodiments, the command generating device is a first operator input device that receives a request from an operator for one of the operating speed of the actuator, the charging speed of the accumulator, and the opening amount of the return valve, and the control unit can control the opening amount of the return valve according to the request. According to some embodiments, the first operator input device selectively receives, from the operator, at least a request for a first operating speed and a request for a second operating speed of the actuator, wherein the second operating speed is faster than the first operating speed, and the control unit controls the return valve to have a first opening amount according to the request for the first operating speed, and controls the return valve to have a second opening amount according to the request for the second operating speed, wherein the second opening amount may be larger than the first opening amount. According to some embodiments, the faster the requested operating speed input to the first operator input device, the more the control unit can control the return valve to have a larger opening amount. According to some embodiments, the command generating device is a sensor that detects the position of a predetermined portion of the working device, and the control unit can control the opening amount of the return valve according to the position of the predetermined portion of the working device detected by the sensor. According to some embodiments, the predetermined portion of the working device may be a bucket. According to some embodiments, the control unit at least controls the return valve to have a third opening amount when the predetermined portion of the working device is at a third position, and controls the return valve to have a fourth opening amount when the predetermined portion of the working device is at a fourth position, wherein the fourth position is at lower height than the third position and the fourth opening amount may be larger than the third opening amount. According to some embodiments, the lower the position of the predetermined portion of the working device detected by the sensor, the more the control unit can control the return valve so that the return valve has a larger opening amount. According to some embodiments, the third position and the fourth position may be lower than a preset reference height. According to some embodiments, the reference height is the floor height of the working machine, and the third position and the fourth position may be at positions lower than the floor of the working machine. According to some embodiments, when the predetermined portion of the working device is at a position higher than or equal to the reference height, the control unit controls the return valve so that the return valve has a constant opening amount, wherein the const