JPH0630255U - Hydraulic motor drive circuit - Google Patents

Abstract

(57) [Summary] [Purpose] To reduce the occurrence of shocks when starting and braking when turning or running a construction machine. A drive circuit for a hydraulic motor, in which two main pipe lines 15 and 16 are provided between a hydraulic pump 12 and a hydraulic motor, and a first pilot oil line is provided between the two main pipe lines 15 and 16. 21 is provided and is connected to the inlet port of the selection valve 24 via the first shuttle valve 22. The pilot oil passage 23 to this inlet port is branched to derive the pilot pressure to the pilot port 26 on the opening side of the selection valve 24. Further, the second pilot oil passage 29 is provided between the two main pilot oil passages 27, 28 branched from the upstream side of the counter balance valve 13.
Is provided and the pilot pressure is led out to the pilot port 34 with the spring 33 on the closing side of the selection valve 24 via the second shuttle valve 30. A throttle valve 32 is provided in the pilot oil passage 31 leading to the pilot port 34.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a drive circuit for a hydraulic motor of a construction machine, and more particularly to a drive circuit for a hydraulic motor for reducing a shock generated when starting or braking a construction machine.

[0002]

[Prior art]

 When turning or traveling a construction machine, a shock is likely to occur when the operation is started or when braking is performed. As a conventional technique for reducing this shock, for example, the one disclosed in Japanese Patent Publication No. 61-37481 or the one disclosed in Japanese Patent Publication No. 47-9646 is known.

[0003]

[Problems to be solved by the device]

 The one described in Japanese Patent Publication No. Sho 61-37481 described above attempts to reduce the shock by keeping the relief pressure at a low pressure for a certain period at the beginning of starting or braking, but after a certain period of time, the high pressure is set. Therefore, the shock of the stop gap cannot be reduced.

On the other hand, the one disclosed in Japanese Examined Patent Publication No. 47-9646 discloses that a driving pressure is applied to a back pressure chamber of a spring chamber of a driving side relief valve to generate a high torque during driving to set a high pressure, During braking, a low pressure setting is applied to reduce the shock. However, if the low pressure setting is left as it is, it is not possible to set the low pressure to a certain level or lower because it is dangerous because the braking time and the braking distance are extended during downhill braking such as traveling, and it is not possible to significantly reduce the shock. Can not.

Therefore, when starting and braking during turning or traveling of the construction machine, there arises a technical problem to be solved in order to reduce the occurrence of shock as much as possible. The invention aims to solve this problem.

[0006]

[Means for Solving the Problems]

 The present invention has been proposed to achieve the above object, and the discharge oil of a hydraulic pump is connected to a hydraulic motor by two main pipes via a directional control valve and a counterbalance valve. In a drive circuit of a hydraulic motor in which a bypass oil passage is connected between the passages and a relief valve of a set pressure variable type is provided in the crossover, a first pilot oil passage is provided between the two main pipelines. The first shuttle valve is interposed, the pilot oil passage of the outlet port of the first shuttle valve is connected to the inlet port of the closed or open selection valve, and the pilot oil of the outlet port of the first shuttle valve is connected. Branch the other pilot oil passage from the passage and connect it to the pilot port on the open side of the selection valve.

Further, a second pilot oil passage is provided between two main pilot oil passages branched from the upstream side of the counter balance valve, and a second shuttle valve is interposed between the two main pilot oil passages. A throttle valve is installed in the pilot oil passage of the outlet port and connected to the pilot port with spring on the closing side of the selection valve. Furthermore, the third and fourth pilot oil passages are provided at the outlet port of the selection valve, and the two main pilot oil passages from the counterbalance valve and the third and fourth pilot oil passages are provided. Are connected by a third shuttle valve and a fourth shuttle valve, respectively, and the pilot oil passages of the outlet ports of the third shuttle valve and the fourth shuttle valve are respectively set. It provides a drive circuit for the hydraulic motor connected to the.

[0008]

[Action]

 The spool of the directional control valve and the counterbalance valve is switched to one when starting or turning the construction machine, but one of the two main pilot oil passages branched from the upstream side of the counterbalance valve is used. The pilot pressure is supplied to the pressure increasing means of the one set pressure variable relief valve from the passage via the third shuttle valve. Therefore, the relief set pressure can be gradually changed from a low pressure to a high pressure, and a smooth start can be performed. At this time, the spool of the selection valve is held in the closed state.

Next, while the construction machine is turning or running, a driving pressure is applied to the main circuit to increase the pressure by the one set pressure variable relief valve, and the high pressure state is maintained to maintain the maximum torque. Can occur. Also, when turning the construction machine or braking during running, the spools of the directional control valve and the counterbalance valve return to the neutral position, and the main pipe line on the return side is closed, but due to inertial force, the first pilot oil line The pilot pressure is discharged from the shuttle valve of No. 1 to the inlet port of the selection valve, and the pilot pressure on the opening side increases and the selection valve opens. Therefore, the pilot oil led to the fourth pilot oil passage pressurizes the other set pressure variable type relief valve via the fourth shuttle valve. This boosting time can be adjusted by the spool stroke of the selection valve and the throttle valve installed after the second shuttle valve, etc., to maintain a low pressure state for a long time during flatland traveling to reduce shock during braking and to reduce downhill slopes. At the time of sudden braking, etc., shorten the low pressure state and immediately increase it to a high pressure to stop the hydraulic motor.

[0010]

【Example】

 Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a drive circuit diagram of the hydraulic motor, showing a state in which the spool of the directional control valve 11 is in the neutral position 11a without operating the operating lever 10 and the discharge oil of the hydraulic pump 12 is closed. A counter balance valve 13 is provided on the downstream side of the direction control valve 11, and two main pipelines 15 and 16 are connected to the hydraulic motor 14. Bypass oil passages 17 and 18 are provided between the two main pipes 15 and 16, and relief valves 19 and 20 of variable set pressure are provided in the crossover.

Further, a first pilot oil passage 21 is provided between the two main pipes 15 and 16, and a first shuttle valve 22 is interposed in the middle portion thereof. The pilot oil passage 23 of the outlet port of the first shuttle valve 22 is connected to the inlet port of the selection valve 24, and another pilot oil passage 25 is branched from the pilot oil passage 23 to open the selection valve 24. To the pilot port 26 of the.

On the other hand, two main pilot oil passages 27 and 28 are provided so as to be branched from the upstream side of the counter balance valve 13, and a second pilot oil passage 29 is provided between the two main pilot oil passages 27 and 28. Is provided, and the second shuttle valve 30 is interposed in the middle part thereof. A throttle valve 32 is provided in a pilot oil passage 31 at the outlet port of the second shuttle valve 30 and connected to a pilot port 34 with a spring 33 on the closing side of the selection valve 24.

Further, two third and fourth pilot oil passages 35 and 36 are provided at the outlet port of the selection valve 24, and one main pilot oil passage 27 from the counter balance valve 13 and the third pilot oil passage 27 are provided. The pilot oil passage 35 is connected via a third shuttle valve 37, and the other main pilot oil passage 28 and the fourth pilot oil passage 36 are connected via a fourth shuttle valve 38. The pilot oil passage 39 at the outlet port of the third shuttle valve 37 is connected to the pressure increasing means 19a of the one set pressure variable relief valve 19, and the pilot oil at the outlet port of the fourth shuttle valve 38 is connected. The passage 40 is connected to the pressure increasing means 20a of the other relief valve 20 of the variable set pressure type.

The operation of the drive circuit for the hydraulic motor will be described. First, the case where the spool of the directional control valve 11 is switched from the position 11a to the position 11b by the operation lever 10 will be described. As shown in FIG. 2, when the directional control valve 11 is switched, the spool of the counter balance valve 13 is also switched from the position of 13a to the position of 13b, the hydraulic oil of the hydraulic pump 12 is led to one main pipe line 15, and the other main pipe line is drawn. Since 16 communicates with the tank 41, the hydraulic motor 14 starts rotating. At this time, the pilot pressure is applied from the main pilot oil passage 27 via the third shuttle valve 37 to the pressure increasing means 19a of the relief valve 19 of one set pressure variable type, and the operation of the one relief valve 19 causes the main pipe to operate. The hydraulic pressure in the passage 15 gradually changes from low pressure to high pressure, and the hydraulic motor 14 smoothly starts rotating. Although not shown, if a delay means such as a throttle valve is provided in the pilot oil passage 39, it is possible to further reduce the shock at startup.

At that time, pilot oil is also discharged from the main pilot oil passage 27 to the pilot oil passage 31 via the second shuttle valve 30, and this pilot oil passes through the throttle valve 32 and has the spring 33. Pilot pressure is generated in the pilot port 34 on the closing side of the selection valve 24. On the other hand, pilot oil is also discharged from the main pipeline 15 to the pilot oil passage 23 via the first shuttle valve 22, and a part of the pilot oil is supplied from the pilot oil passage 25 to the pilot port 26 on the opening side of the selection valve 24. generate.

Here, pilot pressure is applied to the pilot ports 34 and 26 on both sides of the selection valve 24, but the throttle valve 32 delays the supply of pilot oil to the pilot port 34 side, and the spool of the selection valve 24 Attempt to switch from position 24a to position 24b. However, by adjusting the stroke of the spool of the selection valve 24 and the opening of the throttle valve 32, before the spool of the selection valve 24 is switched to 24b, the pilot pressures of both pilot ports 34 and 26 become equal, and the spring 33 The spool of the selection valve 24 is held at the position of 24a by the pressing force of. Therefore, when the rotation of the hydraulic motor 14 is started, the selection valve 24 maintains the closed state, and the pilot oil is not led to the third pilot oil passage 35 and the fourth pilot oil passage 36 of the outlet port.

Next, a description will be given of when the hydraulic motor 14 is rotationally driven. At this time, the hydraulic oil of the hydraulic pump 12 continues to be supplied to the hydraulic motor 14 via the main pipe line 15, and the pilot oil is also supplied to the pressure increasing means 19a of the one relief valve 19, so that the relief valve The hydraulic oil supplied from the main pipe 15 to the hydraulic motor 14 by the operation of 19 is maintained at a high pressure, and the hydraulic motor 14 can generate the maximum torque.

The case of braking the rotation of the hydraulic motor 14 will be described. When the spool of the directional control valve 11 is switched from the position 11b to 11a by the operating lever 10, the counter balance valve 13 also switches the spool from the position 13b to 13a and returns to the state shown in FIG. At this time, the main pipelines 15 and 16 are closed, and the inertial force of the hydraulic motor 14 causes the hydraulic pressure on the side of the main pipeline 16 to sharply increase and braking is performed.

Then, by the action of the relief valves 19 and 20 of both set pressure variable type provided in the crossover, the hydraulic pressures of the main pipelines 15 and 16 are averaged and gradually reduced to a low pressure, and a shock at the time of braking is generated. Reduce. At that time, the hydraulic oil in the main pipe line 16 is led out to the pilot oil lines 23 and 25 via the first shuttle valve 22. On the other hand, since the two main pilot oil passages 27 and 28 communicate with the tank 41, the pilot oil is not led to the pilot oil passage 31. Accordingly, no pilot pressure is applied to the pilot port 34 on the closing side of the selection valve 24, and only the pressing force of the spring 33 acts, and the pilot port 26 on the opening side of the selection valve 24 acts on the pilot oil from the main pipeline 16. Acts as pilot pressure.

Thus, the spool of the selection valve 24 is switched from the position of 24a to the position of 24b. However, depending on the stroke of the spool of the selection valve 24 and the setting of the opening of the throttle valve 32, the aircraft can run on level ground. When braking, adjust so that the spool of the selection valve 24 does not switch to the position of 24b until the aircraft completely stops. Therefore, the spool of the selection valve 24 stays in the closed state at the position of 24a, and pilot oil is not led out to the third pilot oil passage 35 and the fourth pilot oil passage 36 of the outlet port. That is, no pilot pressure is applied to the left and right inlet ports of the third shuttle valve 37 and the fourth shuttle valve 38, the pressure increasing means 19a and 20a of both the relief valves 19 and 20 do not operate, and the main pipe The paths 15 and 16 are braked to the low pressure state, and the shock during braking can be reduced.

[0021] Here, for example, when the vehicle is braking on a downhill, since the positional energy is added to the inertial energy, the braking time and the braking distance become long if the low pressure setting is left as it is. Due to the difference in the braking time, the spool of the selection valve 24 is switched from the position 24a to the position 24b, and the selection valve 24 is opened as shown in FIG. Therefore, the pilot oil in the first pilot oil passage 21 passes through the oil passage 23 and the selection valve 24 via the shuttle valve 22, and is sent to the third pilot oil passage 35 and the fourth pilot oil passage 36. Is derived. In that case, the pilot pressure is applied to the pressure increasing means 19a and 20a of both the relief valves 19 and 20 and the main pipelines 15 and 16 of both sides become high in pressure, so that the aircraft is completely stopped and safety can be ensured. it can.

The present invention can be variously modified without departing from the spirit of the present invention, and it goes without saying that the present invention extends to the modified one.

[0023]

[Effect of device]

 As described in detail in the above-mentioned embodiment, the present invention provides a first pilot provided between the main pipelines to the respective pressure increasing means of the relief valve of the preset pressure variable type provided in the crossover between the two main pipelines. The pilot oil in the oil passage is led out through the selection valve. Since the selection valve adjusts the stroke of the spool and the opening of the throttle leading to the pilot port, the selection valve is kept closed when the hydraulic motor is started and when the vehicle normally runs or stops on level ground.

Therefore, when the airframe is started, the pilot oil from the two pilot oil passages is led to the pressure increasing means of the two relief valves to gradually increase the oil pressure in the main pipeline from a low pressure to a high pressure, resulting in an extremely smooth operation. It is possible to start the rotation of the hydraulic motor. On the other hand, at the time of normal stop on level ground, the selection valve is closed, so the pilot pressure is not applied to the pressure increasing means of both relief valves, and the main pipeline is kept in the low pressure state for a certain period of time, and the aircraft is shocked. Stop without causing.

Thus, it is possible to reduce shocks both when the hydraulic motor is activated and when the brake is applied.

[Brief description of drawings]

FIG. 1 is a drive circuit diagram of a hydraulic motor according to an embodiment of the present invention.

FIG. 2 is a drive circuit diagram of a hydraulic motor showing an operating state of a directional control valve.

FIG. 3 is a drive circuit diagram of a hydraulic motor showing an operating state of a selection valve.

[Explanation of symbols]

 11 Directional Control Valve 12 Hydraulic Pump 13 Counter Balance Valve 14 Hydraulic Motor 15 and 16 Main Pipe Line 17 and 18 Bypass Oil Line 19 and 20 Variable Setting Pressure Relief Valve 19a and 20a Boosting Means 21 First Pilot Oil Line 22 1st Shuttle valve 23,25 Pilot oil passage 24 Selection valve 26,34 Pilot port 27,28 Main pilot oil passage 29 Second pilot oil passage 30 Second shuttle valve 31 Pilot oil passage 32 Throttle valve 33 Spring 35 Third Pilot oil passage 36 Fourth pilot oil passage 37 Third shuttle valve 38 Fourth shuttle valve 39,40 Pilot oil passage

Claims (1)

[Scope of utility model registration request] Claim: What is claimed is: 1. Discharge oil of a hydraulic pump is connected to a hydraulic motor by two main pipelines via a directional control valve and a counterbalance valve, and a bypass oil passage is connected between the two main pipelines to change a set pressure. In a drive circuit of a hydraulic motor having a cross-type relief valve provided in a crossover, a first pilot oil passage is provided between the two main pipelines, and a first shuttle valve is interposed between the two main pipelines. The pilot oil passage at the outlet port of the shuttle valve is connected to the inlet port of the closing or opening selection valve, and another pilot oil passage is branched from the pilot oil passage at the outlet port of the first shuttle valve to select the selection valve. Connected to the open pilot port of the counter balance valve, a second pilot oil passage is provided between the two main pilot oil passages branched from the upstream side of the counterbalance valve, and a second shuttle valve is interposed between the two main pilot oil passages. 2 Shat A throttle valve in the pilot oil passage of the outlet port of the valve, and is connected to the spring-loaded pilot port on the closing side of the selection valve. Pilot oil passages are provided, and the two main pilot oil passages from the counterbalance valve and the third and fourth pilot oil passages are connected by the third shuttle valve and the fourth shuttle valve, respectively, Pilot oil passage of the outlet port of the shuttle valve of 3 and the fourth shuttle valve,
A drive circuit for a hydraulic motor, characterized in that the drive circuit is connected to pressure increasing means of relief valves of variable set pressures.