Method for regulating the release pressure of a release valve for a swing motor

Abstract

Task: To provide a method for adjusting the release pressure of the release valve of a swing motor, which can set the release pressure of each release valve with high precision without rotating the upper swing body. Solution: Sequentially switch the release valves of the swing motors to be adjusted; and while the rotation of each swing motor (17a, 17b) is forcibly stopped and the release pressure of the release valve of the swing motor to be adjusted is lower than that of the release valves of other swing motors, the process of adjusting the release pressure of the release valve of the swing motor to be adjusted is performed while the working oil is supplied from the pump (11) at a flow rate lower than the maximum flow rate of the swing motor.

Description

Technical Field

[0001] This invention relates to a method for adjusting the release pressure of a release valve for multiple swing motors, wherein the multiple swing motors rotate the swing body of a working machine. Background Technology

[0002] In hydraulically driven machinery, various release valves installed in the hydraulic circuit can achieve the desired performance in each component driven by an appropriately set release pressure (see, for example, Patent Documents 1 and 2).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: JP 1999-94105A

[0006] Patent Document 2: JP 1993-60105A Summary of the Invention

[0007] The problem to be solved by the present invention

[0008] For example, a relief valve is also provided in a hydraulic motor, which is a fluid pressure actuator (fluid pressure motor) used to rotate the upper swing body of a working machine, and the performance of the relief pressure and rotational torque is directly related. For example, when the relief pressure is set at a low level, it is easier to increase the rotational flow rate due to insufficient acceleration torque on the slope or insufficient braking torque, which may prevent rotation in the inclined direction.

[0009] Specifically, in the case of large-scale machinery, two oscillating motor units can be installed. Each of these units is equipped with a release valve, resulting in two release valves on the same system. Then, by equally distributing the hydraulic oil supplied from the pump to each unit, each release valve operates at half the pump flow rate, which is the sum of the maximum flow rates of the oscillating motors. Therefore, it is ideal to set the release pressure under these flow conditions.

[0010] However, in the case of a swing motor unit, when the hydraulic oil flows and drives the machine like other pumps and motors while adjusting the pressure of the relief valve, the upper swing body will rotate, requiring a large amount of space, which is impractical, especially for large machinery. Therefore, when actually adjusting the pressure of the relief valve, the swing motor unit is forcibly stopped, preventing the upper swing body from rotating. In this situation, due to factors such as pipeline pressure drop balancing, without equal distribution of pump flow rate, the flow rate on either side of the relief valve can easily be too high or too low, making it difficult to adjust the pressure with high precision.

[0011] Furthermore, adding a circuit for pressure regulation requires additional piping, which complicates the process, increases the number of parts, and raises the risk of leaks.

[0012] Therefore, the object of the present invention is to provide a method for adjusting the release pressure of the release valve of a swing motor, which can set the release pressure of each release valve with high precision without causing the swing body to rotate.

[0013] Problem Solving

[0014] According to one aspect of the present invention, a method for adjusting the release pressure of the release valve of a swing motor for a working machine is provided, wherein the step of adjusting the release pressure of the release valve of the swing motor to be adjusted is performed by sequentially switching the release valve of the swing motor to be adjusted while the rotation of each swing motor is forcibly stopped and the release pressure of the release valve of the swing motor to be adjusted is lower than the release pressure of the release valve of another swing motor, while supplying working fluid from a pump at a flow rate less than or equal to the maximum flow rate of the swing motor.

[0015] Advantageously, in the method for adjusting the release pressure of the release valve for the oscillating motor according to the invention, when the oscillating motors are arranged in pairs and the rotation of each oscillating motor is forced to stop, the release pressure of the release valve for one oscillating motor is set higher than the release pressure of the release valve for the other oscillating motor; when the working fluid is supplied from the pump at a flow rate lower than the maximum flow rate of the oscillating motor, the release pressure of the release valve for one oscillating motor is adjusted; the release pressure of the release valve for one oscillating motor is set lower than the release pressure of the release valve for the other oscillating motor adjusted in the first step; and when the working fluid is supplied from the pump at a flow rate lower than the maximum flow rate of the oscillating motor, the release pressure of the release valve for one oscillating motor is adjusted.

[0016] Advantageously, in the method for regulating the release pressure of the release valve for the oscillating motor according to the invention, the path for one oscillating motor to supply working fluid from the pump is shorter than the path for the other oscillating motor.

[0017] Advantageously, in the method for adjusting the release pressure of the release valve for the oscillating motor according to the invention, the flow rate of the supplied working fluid is the maximum flow rate of the oscillating motor when the release pressure is adjusted.

[0018] Effects of the present invention

[0019] According to the present invention, the pressure releases for multiple oscillating motors are arranged in priority order, and the total flow rate is concentrated on the pressure release valves for the oscillating motors to be adjusted, so that the pressure release of each pressure release valve can be set with high precision without rotating the oscillating body.

[0020] According to the present invention, the setting of the release pressure is prioritized by a release valve for one oscillating motor and a release valve for another oscillating motor to concentrate the total flow rate to one of them, so that the release pressure of each release valve can be set with high precision without rotating the oscillating element.

[0021] According to the present invention, the pressure can be adjusted with the pressure loss of the supply line of the working fluid as small as possible, and the release pressure can be set with higher precision.

[0022] According to the present invention, when the oscillating body actually rotates, the release pressure can be set to the maximum state of the flow rate supplied to one oscillating motor or another oscillating motor, so that the expected rotational torque can be obtained when the oscillating body actually rotates. Attached Figure Description

[0023] Figure 1 An embodiment of a method for adjusting the release pressure of a release valve for a swing motor according to the present invention is shown, wherein (a) is a fluid pressure circuit diagram showing the first step, and (b) is a graph showing the release pressure setting of the release valve in the first step.

[0024] Figure 2 (a) is a fluid pressure loop diagram showing the second step, and (b) is a graph showing the release pressure setting of the release valve in the second step.

[0025] Figure 3 This is a fluid pressure circuit diagram showing the operating state under the release pressure set by the method for adjusting the release pressure of the release valve used for the above-mentioned swing motor.

[0026] Figure 4 This is a side view showing the working machine including the aforementioned fluid pressure circuit. Detailed Implementation

[0027] Embodiments of the present invention will now be described with reference to the accompanying drawings.

[0028] exist Figure 4 In this embodiment, 1 represents the working machine. The working machine 1 is a hydraulically driven machine driven by working hydraulic fluid pressure; in the illustrated example, it is, for example, a hydraulic excavator. The working machine 1 in this embodiment is, for example, a large working machine weighing 49 tons or more.

[0029] The operating machine 1 is a rotary operating machine comprising a lower traveling body 3 and an upper swinging body 4, the upper swinging body being a swinging body rotatably mounted on the lower traveling body 3. The upper swinging body 4 is equipped with a cab 5 and a working device 6, wherein the cab 5 is the operator's cabin. The working device 6 is axially connected to the upper swinging body 4 on one side of the cab 5. Furthermore, the upper swinging body 4 is provided with a machine room 7 containing an engine, pump, control valves, etc., and various oil tanks, such as hydraulic oil tanks and oil tanks, are located on opposite sides of the cab 5, with the working device 6 situated between them. A counterweight 8 is mounted at the end opposite the working device 6, relative to the machine room 7 and the various oil tanks.

[0030] like Figure 1 As shown in (a), the hydraulic circuit 10, which is a fluid pressure circuit used in the working machine 1, supplies hydraulic oil, which is drawn in and discharged from the hydraulic oil tank by a pump (main pump) 11 driven by the engine, to a hydraulic actuator. This hydraulic actuator is a fluid pressure actuator, and the flow rate and direction of the supplied hydraulic oil are controlled by a control valve that operates in response to the operator's operation. This control valve is, for example, installed on... Figure 4 The control levers or pedals on the cab 5 shown allow for the execution of various tasks via the work device 6, such as stopping the rotation of the lower traveling body 3 on the upper swing body 4 by driving the lower traveling body 3 forward and backward.

[0031] Return to Figure 1 (a) Pump 11 is connected via control valves to a plurality of, for example, pairs of oscillating motor units 13a and 13b. Oscillating motor unit 13a is connected between output channels 15a and 16a supplying hydraulic oil from pump 11, an oscillating motor 17a, pairs of oppositely oriented release valves 18a and 19a, and pairs of oppositely oriented replenishment check valves 20a and 21a, and replenishment channel 23a is connected between release valves 18a and 19a and between check valves 20a and 21a. Similarly, oscillating motor unit 13b is connected between output channels 15b and 16b supplying hydraulic oil from pump 11, an oscillating motor 17b, pairs of oppositely oriented release valves 18b and 19b, and pairs of oppositely oriented replenishment check valves 20b and 21b, and replenishment channel 23b is connected between release valves 18b and 19b and between check valves 20b and 21b. Supplemental channels 23a and 23b are connected to the oil tank, for example, via an oil cooler or a spring-loaded check valve.

[0032] Output channels 15a, 15b and output channels 16a, 16b are switched such that one is connected to channel 25 and the other to channel 26 via a control valve. Output channel 15b branches from output channel 15a and is longer than output channel 15a. Output channel 16b also branches from output channel 16a and is longer than output channel 16a. Therefore, the oscillating motor 17a is closer to pump 11 than the oscillating motor 17b, and the hydraulic oil supply line from pump 11 is shorter. Furthermore, a large flow rate (the flow rate of both oscillating motors 17a, 17b) flows into output channels 15a, 16a before the hydraulic oil branches to oscillating motor 17b; therefore, from the viewpoint of pressure loss, the hydraulic pipe diameter of output channels 15a, 16a is typically designed to be larger than that of output channels 15b, 16b.

[0033] Channels 25 and 26 are channels through which hydraulic oil is supplied from pump 11 to one side and returned to the tank on the other side via a switching control valve. Pressure sensors 28 and 29 are provided in channels 25 and 26. In this embodiment, pump pressure is primarily detected by pressure sensor 28, and pressure sensor 29 is not a mandatory component.

[0034] The swing motors 17a and 17b are hydraulic motors that function as fluid pressure motors, enabling the upper swing body 4 ( Figure 4 ) relative to the lower driving body 3 ( Figure 4 The oscillating motors 17a and 17b are arranged opposite each other, for example, relative to the rotation center of the upper oscillating body 4. Figure 4 The swing motors 17a and 17b are equipped with braking devices 31a and 31b for stopping the rotation of the swing motors 17a and 17b. Braking devices 31a and 31b are also referred to as parking brake mechanisms, etc. By stopping the rotation of the swing motors 17a and 17b, for example in the working machinery 1 (… Figure 4 When the operation of ) stops, the braking devices 31a and 31b cause the upper swing body 4 ( Figure 4 ) relative to the lower driving body 3 ( Figure 4 To maintain a forced stop of rotation. In this embodiment, braking devices 31a and 31b are exemplified as mechanical brakes for mechanically braking the rotation of swing motors 17a and 17b. For example, each braking device 31a, 31b includes cylinders 34a, 34b having braking load springs 33a, 33b, and pistons 35a, 35b that transmit the braking load of springs 33a, 33b to the swing motor shaft. The spring chambers of cylinders 34a, 34b are connected to an oil tank via discharge channels 36a, 36b, and the piston chambers of cylinders 34a, 34b are connected to a common pilot pump via brake release guide channels 37a, 37b and a brake release solenoid valve.

[0035] Then, the release valves 18a, 19a and 18b, 19b set the upper limit of the supply pressure from the pump 11 to their release pressure by opening and allowing hydraulic oil to flow from the replenishment channels 23a, 23b to the oil tank, so as to release pressure when a pressure higher than the set release pressure is applied. Therefore, based on the release pressure of the release valves 18a, 19a and 18b, 19b, the swing motors 17a, 17b, i.e., the upper swing body 4 ( Figure 4 The rotational torque of the valves. Relief valves 18a, 19a and 18b, 19b are variable relief valves, for example, electromagnetic variable relief valves that set the relief pressure according to the current value.

[0036] Check valves 20a, 21a and 20b, 21b open in response to the pressure difference between output channels 15a, 16a and 15b, 16b and replenishment channels 23a, 23b, and replenish hydraulic oil from the tank to output channels 15a, 16a or 15b, 16b (on the side of swing motors 17a, 17b) via replenishment channels 23a, 23b, to prevent hydraulic oil from the upper swing body 4 from entering when the rotation of swing motors 17a, 17b stops. Figure 4 The vacuum is created by the inertial rotation of ( ).

[0037] exist Figures 1 to 3 In this paper, the hydraulic circuits connecting hydraulic actuators such as hydraulic cylinders and hydraulic motors other than swing motor 15 and pump 11 are omitted.

[0038] Next, a method for adjusting the release pressure of the release valve according to the illustrated embodiment will be described.

[0039] like Figure 3 As shown, during the actual rotation of the upper swing body 4 ( Figure 4 The hydraulic oil discharged from pump 11 is evenly distributed to the two swing motors 17a and 17b, and the two swing motors 17a and 17b are balanced by swing motors 17a and 17b rotating at the same rotational speed.

[0040] Thus, in order to ensure that the hydraulic oil discharged from pump 11 is evenly distributed to the two swing motors 17a and 17b, the release pressures of the release valves 18a and 19a of swing motor 17a and the release valves 18b and 19b of swing motor 17b must be set to the same or substantially the same pre-set target pressures. If these release pressures are different, the flow balance will be unbalanced because more hydraulic oil discharged from pump 11 will flow to the swing motors, where the relative pressure is lower.

[0041] However, when attempting to set the release pressure of the release valves 18a and 19a for the swing motor 17b and the release pressure of the release valves 18b and 19b, while actually allowing hydraulic oil to flow to the swing motors 17a and 17b and driving the hydraulic oil to the swing motors 17a and 17b, the upper swing body 4 ( Figure 4 ) rotation, especially in large-scale work machinery that requires a lot of space 1 ( Figure 4 In the case of ), it is therefore ideal to set the release pressure of the swing motors 17a and 17b that are forcibly stopped by the braking devices 31a and 31b.

[0042] However, when the swing motors 17a and 17b are forcibly stopped, and hydraulic oil is simultaneously supplied from pump 11 to the swing motors 17a and 17b, the flow rate of the hydraulic oil is biased between the swing motor 17a side and the swing motor 17b side due to the influence of pipeline pressure loss, i.e., the influence of the length of the hydraulic oil supply pipeline from pump 11. Therefore, it is difficult to set the release pressure with high precision.

[0043] Therefore, in this embodiment, the flow rate of hydraulic oil from pump 11 is throttled to less than or equal to the maximum flow rate of swing motors 17a and 17b, and the release pressure can be set with high precision by preferentially setting the release pressure and concentrating the entire flow rate on one side by means of release valves 18a, 19a and 18b, 19b.

[0044] In other words, when the release pressure of the swing motor to be adjusted is lower than the release pressure of other swing motors, preferably lower than the target pressure, while supplying hydraulic oil from pump 11 at a flow rate lower than the maximum flow rate of the swing motor, the steps of forcibly stopping the rotation of each swing motor and adjusting the release pressure of the release valve of the swing motor to be adjusted are performed by sequentially switching the release valve of the swing motor to be adjusted.

[0045] Specifically, in this embodiment with a pair of swing motors 17a and 17b, firstly, when the rotation of the swing motors 17a and 17b is forcibly stopped by the braking devices 31a and 31b, as a first step, the release pressure of the release valve of one swing motor is set to a higher pressure than the release pressure of the release valve of the other swing motor, and the release pressure of the release valve of the other swing motor is adjusted, while the flow rate is squeezed below the maximum flow rate of the swing motor, and hydraulic oil is supplied from the pump 11.

[0046] In this case, preferably, one swing motor is located on the shorter side of the hydraulic oil supply line from pump 11, as swing motor 17a in this embodiment, while the other swing motor is located on the longer side of the hydraulic oil supply line from pump 11, as swing motor 17b in this embodiment.

[0047] That is, as the first step, such as Figure 1 As shown in (a) and 1(b), the release pressure Pa of the release valves 18a and 19a of the oscillating motor 17a, which has a short supply line of hydraulic oil from pump 11, is set and fixed at a higher pressure than the release pressure Pb of the release valves 18b and 19b of the oscillating motor 17b, which has a long supply line of hydraulic oil from pump 11. The release pressure Pb of the release valves 18b and 19b of the oscillating motor 17b is adjusted to a target pressure PT, while the flow rate from pump 11 is reduced to less than half the sum Q of the maximum flow rates of the oscillating motors 17a and 17b to supply hydraulic oil. Thus, since the release pressure Pb of the release valves 18b and 19b of the oscillating motor 17b is lower than the release pressure Pa of the release valves 18a and 19a of the oscillating motor 17a, the hydraulic oil discharged from pump 11 flows to the oscillating motor 17b side at essentially the full flow rate.

[0048] At this point, the flow rate of pump 11 is assumed to be the flow rate to the oscillating motor 17b during actual rotation, i.e., 1 / 2Q or less, which is the maximum flow rate of the oscillating motor 17b. However, by taking into account the increase in release pressure due to the increase in release volume or flow rate (i.e., the effect of the override characteristic), the release pressure of release valves 18b and 19b can be precisely set to the target pressure, preferably 1 / 2Q, during actual rotation. When the flow rate of hydraulic oil from pump 11 is reduced, it is preferable that the control valve is substantially fully open and the discharge flow rate of pump 11 itself is reduced so as not to affect the pressure loss caused by the control valve as much as possible when setting the release pressure.

[0049] In this embodiment, the release pressure is adjusted while the pump pressure is monitored by the pressure sensor 28. Specifically, the release pressure of the release valve 18b is set based on whether the pump pressure detected by the pressure sensor 28 is the target pressure. The release pressure of the release valve 19b is also set based on whether the pump pressure detected by the pressure sensor 28 is the target pressure.

[0050] It should be noted that when the release pressure of release valve 18b is set and when the release pressure of release valve 19b is set, the supply direction of hydraulic oil from pump 11 is reversed by the control valve.

[0051] Then, as a second step, the release pressure of the release valve for one swing motor is set to be lower than the release pressure of the release valve for the other swing motor that was adjusted in the first step, and the release pressure of the release valve for one swing motor is adjusted while the flow rate is squeezed and hydraulic oil is discharged compared with the sum of the maximum flow rates of the swing motors paired with pump 11.

[0052] As described above, in this embodiment, one swing motor is swing motor 17a, and the other swing motor is swing motor 17b. In the second step, as... Figure 2 As shown in (a) and 2(b), the release pressure Pa of the release valves 18a and 19a for the oscillating motor 17a is set to a lower pressure than the release pressure Pb of the release valves 18b and 19b for the oscillating motor 17b adjusted in the first step, and the release pressure Pa of the release valves 18a and 19a for the oscillating motor 17a is adjusted to the target pressure PT. At the same time, the flow rate from the pump 11 is squeezed to less than half of the sum Q of the maximum flow rates of the oscillating motors 17a and 17b, and hydraulic oil is discharged. In this way, since the release pressure Pa of the release valves 18a and 19a for the oscillating motor 17a is lower than the release pressure Pb of the release valves 18b and 19b for the oscillating motor 17b, the hydraulic oil discharged from the pump 11 flows to the oscillating motor 17a side at essentially the full flow rate.

[0053] At this point, if the flow rate of pump 11 is the same as the flow rate to the oscillating motor 17a during actual rotation, i.e., 1 / 2Q or less, which is the maximum flow rate of the oscillating motor 17a, then the flow rate of pump 11 can be the same as or different from that in the first step. Preferably, as in the first step, by taking the override characteristic of the release valves as 1 / 2Q, the release pressure of release valves 18a and 19a can be precisely set to the target pressure during actual rotation. When the flow rate of hydraulic oil from pump 11 is squeezed, it is preferable that the control valve is substantially fully open, and the discharge flow rate of pump 11 itself is squeezed so as not to affect the pressure loss caused by the control valve as much as possible when setting the release pressure.

[0054] In this embodiment, the release pressure is adjusted while the pump pressure is monitored by pressure sensors 28 and 29. In other words, the release pressure of release valve 18a is set based on whether the pump pressure detected by pressure sensor 28 is the target pressure. Furthermore, the release pressure of release valve 19a is set based on whether the pump pressure detected by pressure sensor 28 is the target pressure.

[0055] Note that when the release pressure of release valve 18a is set and when the release pressure of release valve 19a is set, the supply direction of hydraulic oil from pump 11 is reversed by the control valve.

[0056] In this way, the release pressure of the release valves for multiple swing motors is set in priority, and the total flow rate is concentrated on the release valves for the swing motors to be adjusted, so that the release pressure of each release valve can be set with high precision without rotating the upper swing body 4.

[0057] In this embodiment, the release pressures of the release valves 18a and 19a for the swing motor 17a and the release valves 18b and 19b for the swing motor 17b are set in priority order, and the entire flow rate is concentrated on one of the release valves 18a, 19a and 18b, 19b, so that the release pressures of the release valves 18a, 19a and 18b, 19b can be set with high precision without rotating the upper swing body 4.

[0058] Furthermore, for example, if the release pressure of the release valves 18a and 19a of the swing motor 17a near the pump 11 side is set first (i.e., the hydraulic oil supply line is short), and then the release pressure of the release valves 18b and 19b of the swing motor 17b far from the pump 11 side is set (i.e., the hydraulic oil supply line is long), in this case, when the release pressure of the release valves 18b and 19b is set according to the increase of the pump pressure, the pressure loss of the hydraulic oil supply line to the swing motor 17b side makes it easier for the hydraulic oil from the pump 11 to flow to the release valves 18a and 19a side where the release pressure was previously set, and it is easier for all the hydraulic oil to flow to the release valves 18b and 19b side during pressure regulation. Furthermore, even when the release pressures of the release valves 18b and 19b on the side of the oscillating motor 17b are significantly low, the release pressures of the release valves 18b and 19b on the side of the oscillating motor 17b will not be detected. The side of the oscillating motor 17b is the side where the pressure loss may be greater due to the smaller diameter of the hydraulic lines supplying the oscillating motor 17a compared to the side of the oscillating motor 17a, and it is located far from the pump 11. Therefore, in this embodiment, the release pressures of the release valves 18b and 19b of the oscillating motor 17b, which have relatively larger pressure losses the further away from the pump 11, are first set. Then, the release pressures of the release valves 18a and 19a of the oscillating motor 17a, which have relatively smaller pressure losses the closer to the pump 11, are set. As a result, when the release pressures of the release valves 18a and 19a for the oscillating motor 17a are set, the pressure loss of the hydraulic oil supply lines is less affected by the pressure of the hydraulic fluid, and the total amount of hydraulic oil from the pump 11 can be supplied to the release valves 18a and 19a before the pressure regulation ends, so that changes in pump pressure can be considered changes in the release pressures of the release valves 18a and 19a. Therefore, by adjusting the pressure in the order of this embodiment, the pressure can be controlled to minimize the pressure loss in the hydraulic oil supply line, and the release pressure can be set to a higher precision.

[0059] Furthermore, by setting the flow rate of the hydraulic oil supplied in the first and second steps to 1 / 2Q of the maximum flow rate of each swing motor 17a, 17b, the release pressure can be set to the maximum state of the flow rate supplied to the swing motor 17a or swing motor 17b during the actual rotation of the upper swing body 4. Therefore, the expected rotational torque can be obtained when the upper swing body 4 actually rotates.

[0060] As a result, sufficient acceleration torque and braking torque of the upper swing body 4 can be ensured, the upper swing body 4 can reliably rotate tilted in the tilting direction, and the rotational flow of the upper swing body 4, i.e., the inertial rotation when stopped, can be reduced.

[0061] Industrial applicability

[0062] This invention can be used by manufacturers engaged in the manufacture and sale of work machinery with oscillating bodies, etc.

Claims

1. A method for adjusting the release pressure of a release valve for multiple swing motors, wherein the multiple swing motors rotate the swing body of a working machine, characterized in that, The adjustment method includes: The release valve of the swing motor to be adjusted is switched sequentially; and The process of forcibly stopping the rotation of each swing motor is performed, and while the release pressure of the release valve of the swing motor to be adjusted is lower than the release pressure of the release valve of the other swing motors, the release pressure of the release valve of the swing motor to be adjusted is adjusted while the working fluid is supplied from the pump at a flow rate lower than the maximum flow rate of the swing motor.

2. The method for adjusting the release pressure of the release valve for multiple swing motors according to claim 1, characterized in that: The swing motors are set in pairs. The rotation of each swing motor, which is forced to stop, The release pressure of the release valve for one oscillating motor is set to a higher pressure than the release pressure of the release valve for the other oscillating motor, so as to regulate the release pressure of the release valve for the other oscillating motor while supplying the working fluid from the pump at a flow rate less than or equal to the maximum flow rate of the oscillating motor. The release pressure of the release valve for one oscillating motor is set to a lower pressure than the release pressure of the release valve for the other oscillating motor adjusted in the first step, so as to adjust the release pressure of the release valve for one oscillating motor while supplying the working fluid from the pump at a flow rate less than or equal to the maximum flow rate of the oscillating motor.

3. The method for adjusting the release pressure of the release valve for multiple swing motors according to claim 1, characterized in that: One oscillating motor has a shorter supply line for the working fluid from the pump than the other oscillating motor.

4. The method for adjusting the release pressure of the release valve for a plurality of swing motors according to any one of claims 1 to 3, characterized in that: The flow rate of the working fluid supplied when adjusting the release pressure is the maximum flow rate of the oscillating motor.

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