EP-4741586-A1 - WORKING MACHINE AND METHOD FOR CONTROLLING SAME

EP4741586A1EP 4741586 A1EP4741586 A1EP 4741586A1EP-4741586-A1

Abstract

This working machine may comprise: a high pressure side; a low pressure side; a hydraulic machine configured to rotate and drive a load; an inlet valve configured to allow or block fluid communication between the high pressure side and an inlet side of the hydraulic machine; an outlet valve configured to allow or block fluid communication between an outlet side of the hydraulic machine and the low pressure side; and a control unit configured to perform hydraulic machine control to, if an actual differential pressure (ΔP act ) of a differential pressure (ΔP = P h - P i ) between a hydraulic pressure (P h ) on the high pressure side and a pressure (P i ) on the inlet side of the hydraulic machine becomes less than a preset reference differential pressure (ΔPref), increase the capacity of the hydraulic machine, and if the actual differential pressure becomes greater than the reference differential pressure, reduce the capacity of the hydraulic machine. In addition, the control unit may be configured to perform valve control to, if the actual rotational speed of the hydraulic machine becomes less than the required rotational speed of the hydraulic machine corresponding to a request input to an operator input device, increase the degree of opening of the inlet valve, and if the actual rotational speed becomes greater than the required rotational speed, reduce the degree of opening.

Inventors

BAE, SANGKI
KWON, Hoeryoung
YOON, Gijun

Assignees

Volvo Construction Equipment AB

Dates

Publication Date: 20260513
Application Date: 20230703

Claims (15)

A working machine, comprising; a high pressure side, a low pressure side, a hydraulic machine configured to rotate and drive a load, an inlet valve configured to allow or block fluid communication between the high pressure side and an inlet side of the hydraulic machine, an outlet valve configured to allow or block fluid communication between the low pressure side and an outlet side of the hydraulic machine, a control unit configured to perform hydraulic machine control to increase the displacement of the hydraulic machine when the actual differential pressure between the hydraulic pressure on the high pressure side and the pressure on the inlet side of the hydraulic machine becomes smaller than a preset reference differential pressure, and to decrease the displacement of the hydraulic machine when the actual differential pressure becomes larger than the reference differential pressure.
The working machine of claim 1, wherein the hydraulic machine is a traveling actuator, wherein the reference differential pressure is set based on the flat ground travel of the working machine.
The working machine of claim 1, further comprising an operator input device configured to receive a request for the rotational speed of the hydraulic machine, wherein the control unit is configured to perform valve control to, if the actual rotational speed of the hydraulic machine becomes smaller than the demanded rotational speed of the hydraulic machine corresponding to the request input to the operator input device, increase the degree of opening of the inlet valve, and if the actual rotational speed becomes greater than the demanded rotational speed, decrease the degree of opening.
A working machine, comprising; a high pressure side, a low pressure side, a hydraulic machine configured to rotate and drive a load, an inlet valve configured to allow or block fluid communication between the high pressure side and an inlet side of the hydraulic machine, an outlet valve configured to allow or block fluid communication between the low pressure side and an outlet side of the hydraulic machine, an operator input device configured to receive a request for the rotational speed of the hydraulic machine, a control unit configured to perform valve control to, if the actual rotational speed of the hydraulic machine becomes smaller than the demanded rotational speed of the hydraulic machine corresponding to a request input to the operator input device, increase the degree of opening of the inlet valve, and if the actual rotational speed becomes greater than the demanded rotational speed, decrease the degree of opening.
The working machine of claim 3 or 4, wherein the hydraulic machine is a traveling actuator.
The working machine of any one of claims 1 to 4, wherein the hydraulic machine is a hydraulic motor.
The working machine of any one of claims 1 to 4, further comprising at least one hydraulic cylinder and/or swing hydraulic motor in which an inlet side is configured to be in fluid communication with the high pressure side and an outlet side is configured to be in fluid communication with the low pressure side.
The working machine of any one of claims 1 to 4, comprising a first valve and a second valve as the inlet valves, and a third valve and a fourth valve as the outlet valves, wherein the first valve is arranged between the high pressure side and the first side of the hydraulic machine, wherein the second valve is arranged between the high pressure side and the second side of the hydraulic machine, wherein the third valve is arranged between the low pressure side and the first side, wherein the fourth valve is arranged between the low pressure side and the second side, wherein the first side is in fluid communication with the high pressure side as the inlet side and the second side is in fluid communication with the low pressure side as the outlet side, as the first valve is opened, the second valve is closed, the third valve is closed, and the fourth valve is opened, wherein the second side is in fluid communication with the high pressure side as the inlet side and the first side is in fluid communication with the low pressure side as the outlet side, as the first valve is closed, the second valve is opened, the third valve is opened, and the fourth valve is closed.
The working machine of any one of claims 1 to 4, further comprising a pump configured to provide pressurized fluid to the high pressure side.
The working machine of any one of claims 1 to 4, wherein the high pressure side comprises at least one high pressure accumulator, wherein the low pressure side comprises at least one low pressure accumulator.
A method for controlling a working machine, wherein the working machine comprises a high pressure side, a low pressure side, a hydraulic machine configured to rotate and drive a load, an inlet valve configured to allow or block fluid communication between the high pressure side and the inlet side of the hydraulic machine, and an outlet valve configured to allow or block fluid communication between the outlet side of the hydraulic machine and the low pressure side, wherein the method comprises performing hydraulic machine control to increase the displacement of the hydraulic machine when the actual differential pressure between the hydraulic pressure on the high pressure side and the pressure on the inlet side of the hydraulic machine becomes smaller than a preset reference differential pressure, and to decrease the displacement of the hydraulic machine when the actual differential pressure becomes larger than the reference differential pressure.
The working machine of claim 11, wherein the hydraulic machine is a traveling actuator, wherein the reference differential pressure is set based on the flat ground travel of the working machine.
The method of claim 11, wherein the working machine further comprises an operator input device configured to receive a request for the rotational speed of the hydraulic machine, wherein the method comprises performing valve control to, if the actual rotational speed of the hydraulic machine becomes smaller than the demanded rotational speed of the hydraulic machine corresponding to the request input to the operator input device, increase the degree of opening of the inlet valve, and if the actual rotational speed becomes greater than the demanded rotational speed, decrease the degree of opening.
A method for controlling a working machine, wherein the working machine comprises a high pressure side, a low pressure side, a hydraulic machine configured to rotate and drive a load, an inlet valve configured to allow or block fluid communication between the high pressure side and the inlet side of the hydraulic machine, an outlet valve configured to allow or block fluid communication between the outlet side of the hydraulic machine and the low pressure side, and an operator input device configured to receive a request for the rotational speed of the hydraulic machine, wherein the method comprises performing valve control to, if the actual rotational speed of the hydraulic machine becomes smaller than the demanded rotational speed of the hydraulic machine corresponding to the request input to the operator input device, increase the degree of opening of the inlet valve, and if the actual rotational speed becomes greater than the demanded rotational speed, decrease the degree of opening.
The method of any one of claims 11 to 14, wherein the working machine comprises a first valve and a second valve as the inlet valves, and a third valve and a fourth valve as the outlet valves, wherein the first valve is arranged between the high pressure side and the first side of the hydraulic machine, wherein the second valve is arranged between the high pressure side and the second side of the hydraulic machine, wherein the third valve is arranged between the low pressure side and the first side, wherein the fourth valve is arranged between the low pressure side and the second side, wherein the first side is in fluid communication with the high pressure side as the inlet side and the second side is in fluid communication with the low pressure side as the outlet side, as the first valve is opened, the second valve is closed, the third valve is closed, and the fourth valve is opened, wherein the second side is in fluid communication with the high pressure side as the inlet side and the first side is in fluid communication with the low pressure side as the outlet side, as the first valve is closed, the second valve is opened, the third valve is opened, and the fourth valve is closed.

Description

TECHNICAL FIELD The present disclosure relates to a working machine and a method for controlling the same, and relates to a working machine and a method for controlling the same, which optimally controls the displacement of a hydraulic machine that rotates and drives a load and the opening and closing of an inlet valve. BACKGROUND ART Hydraulic systems are used in a variety of applications. For example, working machines typically rely on hydraulic systems to provide power to handle loads. Hydraulic systems for working machines may include various hydraulic actuators, such as hydraulic cylinders and rotary hydraulic machines. A hydraulic cylinder may be provided for operating a working device including, for example, an arm and a bucket. Rotary hydraulic machines can be used, for example, for propulsion of working machines and/or for swing of excavators. Hydraulic hybrid systems can be used to reduce fuel consumption in internal combustion engines, for example, by recovering energy from hydraulic actuators. A hydraulic system that includes a dedicated high pressure side and a dedicated low pressure side may be referred to as a dual pressure hydraulic system. A dual pressure hydraulic system typically includes one or more high pressure accumulators connected to the high pressure side, and one or more low pressure accumulators connected to the low pressure side. Advantages associated with dual pressure hydraulic systems are, for example, improved energy efficiency and controllability. DETAILED DESCRIPTION OF THE INVENTION Means for Solving Problem According to a first aspect of the present disclosure, there is provided a working machine comprising: a high pressure side; a low pressure side; a hydraulic machine configured to rotate and drive a load; an inlet valve configured to allow or block fluid communication between the high pressure side and an inlet side of the hydraulic machine; an outlet valve configured to allow or block fluid communication between an outlet side of the hydraulic machine and the low pressure side; and a control unit configured to perform hydraulic machine control to, if an actual differential pressure (ΔPact) of a differential pressure (ΔP = Ph-Pi) between a hydraulic pressure (Ph) on the high pressure side and a pressure (Pi) on the inlet side of the hydraulic machine becomes less than a preset reference differential pressure (ΔPref), increase the displacement of the hydraulic machine, and if the actual differential pressure becomes greater than the reference differential pressure, decrease the displacement of the hydraulic machine. In some examples, the hydraulic machine is a traveling actuator, and the reference differential pressure can be set based on the ground level traveling of the working machine. In some examples, an operator input device configured to receive a request for a rotational speed of the hydraulic machine is further comprised, and the control unit may be configured to perform valve control to, if the actual rotational speed (Vact) of the hydraulic machine becomes less than the demanded rotational speed (Vdmd) of the hydraulic machine corresponding to the request input to the operator input device, increase the degree of opening of the inlet valve, and if the actual rotational speed (Vact) becomes greater than the demanded rotational speed (Vdmd), decrease the degree of opening. According to a second aspect of the present disclosure, there is provided a working machine comprising: a high pressure side; a low pressure side; a hydraulic machine configured to rotate and drive a load; an inlet valve configured to allow or block fluid communication between the high pressure side and an inlet side of the hydraulic machine; an outlet valve configured to allow or block fluid communication between an outlet side of the hydraulic machine and the low pressure side; an operator input device configured to receive a request for a rotational speed of the hydraulic machine; and a control unit configured to perform valve control to, if an actual rotational speed of the hydraulic machine becomes less than a demanded rotational speed of the hydraulic machine corresponding to the request input to the operator input device, increase the degree of opening of the inlet valve, and if the actual rotational speed becomes greater than the demanded rotational speed, decrease the degree of opening. In some examples, the hydraulic machine may be a traveling actuator. In some examples, the hydraulic machine may be a hydraulic motor. In some examples, it may further comprise at least one hydraulic cylinder and/or a swing hydraulic motor in which an inlet side is configured to be in fluid communication with the high pressure side and an outlet side is configured to be in fluid communication with the low pressure side. In some examples, a first valve and a second valve are included as the inlet valves, and a third valve and a fourth valve are included as the outlet valves, wherein the first valve is