JP4455959B2 - Hydraulic system - Google Patents

Description

  The present invention uses a load pressure sensitive type priority valve capable of supplying a divided flow of pressure oil to a plurality of actuators including a priority actuator, and a hydraulic pressure capable of giving priority to the flow separation to the priority actuator. In particular, the present invention relates to a hydraulic system suitably used for industrial vehicles such as forklifts and trucks.

  Conventionally, in this type of hydraulic system, by using a priority valve mechanism, for example, pressure oil is preferentially diverted to an actuator for driving the steering, and the surplus flow is supplied to other non-prioritized actuators. It has a configuration that can. As a configuration for preferentially supplying pressure oil to a priority actuator, many circuit configurations are used in which a switching control valve is interposed on a connection line between the priority valve and another actuator. In this circuit configuration, the pressure oil output from the priority valve to the other actuator is switched to the drain line by the switching control valve placed in the middle of the connection pipe, discharged to the tank, and supplied to the other actuator. Being restricted.

  Using an emergency valve having the same effect as a switching control valve disposed on a connection pipe line between the priority valve and another actuator, the priority valve and the other actuator are connected via an unload path connected to the emergency valve. A multi-valve device (see Patent Document 1) that can switch and connect the connecting pipe line to the tank line has been proposed.

  As shown in FIG. 3, in the multiple valve device described in Patent Document 1, pressure oil supplied from a hydraulic pump (not shown) is divided into a priority flow and a surplus flow by a priority valve mechanism 80. The priority valve mechanism 80 is configured by integrally incorporating various valves such as a priority valve main body 87 into a main body in which a hydraulic path is formed, and pressure oil supplied from a hydraulic pump (not shown) is used as a priority flow. Divide into surplus flow.

  The priority flow discharged from the priority valve mechanism 80 is used as pressure oil for operating the priority valve mechanism 80, and is supplied from the port 101 to a steering operation auxiliary circuit (not shown) as pressure oil for steering operation. Further, when the differential pressure between the load pressure 102 of the steering operation circuit and the steering pump port 101 rises above a predetermined pressure, the spool position of the priority valve mechanism 80 is switched by the differential pressure and supplied from a hydraulic pump (not shown). A portion of the pressurized oil can be used as a surplus flow.

  The surplus flow discharged from the priority valve mechanism 80 is guided to a plurality of switching valve mechanisms 81A and 81B connected to the priority valve mechanism. That is, the surplus flow is guided through the parallel line 83 to the input ports of the switching valves 82A and 82B in the switching valve mechanisms 81A and 81B, respectively.

  The parallel line 83 and the tank line 84 are connected via an unload path 91 provided in the emergency valve block 85. When the emergency valve 90 provided on the unload path 91 is opened, the parallel line 83 communicates with the tank line 84 through the switching valve 93 and the flow rate control valve 94.

  The switching valve mechanisms 81A and 81B are configured by integrating three-input three-output switching valves 82A and 82B and the like into valve sections 88A and 88B having hydraulic paths formed therein. One switching valve mechanism 82 </ b> A includes an output port 97 connected to the lift cylinder 96. The internal path of the switching valve 82A is switched by manual operation of the lift lever 95, and the operation of the lift cylinder 96 can be controlled.

  The other switching valve mechanism 81B includes two output ports 99A and 99B connected to the tilt cylinder 98, respectively. The switching valve 82B can control the operation of the tilt cylinder 98 by switching the internal path by manual operation of the tilt lever 100.

The emergency valve 90 is a solenoid valve, and is disposed on an unload path 91 that connects a hydraulic path that forms the tank line 84 and a hydraulic path that forms the parallel line 83 among the internal hydraulic paths of the emergency valve block 85. Yes. When the electromagnetic valve 93 is opened, the emergency valve 90 is opened and the parallel line 83 and the tank line 84 are communicated with each other through the flow control valve 94.
JP 2001-99108 A

  In the multiple valve device as described in Patent Document 1, the priority valve mechanism 80 is connected to the input ports of the switching valves 82A and 82B through the parallel line 83, and the parallel line 83 and the tank line 84 are an emergency valve block. It is connected via an unload path 91 provided at 85. As a result, the surplus flow in the parallel line 83 can be completely unloaded by opening the emergency valve 90 before leading the surplus flow in the parallel line 83 to the lift cylinder 96 and the tilt cylinder 98 via the switching valves 82A and 82B.

  However, in order to unload the surplus flow, the parallel line 83 had to be extended, and a switching valve as the emergency valve 90 and a flow rate control valve 94 had to be provided separately. In addition, there is a problem that a switching valve capable of switching a large amount of pressure oil must be used as the emergency valve 90 in order to flow the surplus flow.

  In the invention of the present application, a hydraulic system that solves these problems and can preferentially perform diversion to the preferred actuator with a simple configuration without using a switching valve capable of switching a large flow rate. It is to provide.

The object of the present invention can be achieved by the inventions described in claims 1 to 3.
That is, in the present invention, as described in claim 1, in the hydraulic system using the load pressure sensitive priority valve, the actuator is divided into a preferred actuator and at least one or more other actuators. As a first operating pressure to be switched to a switching position for stopping the diversion to the other actuators among the operating pressures for operating the priority valve, a first pressure is used. The second detection pressure, which is the detection pressure of the output pressure from the priority valve, acts as the second operating pressure that is switched to the switching position side where the detection pressure and the urging force of the spring are applied and the flow is divided to the other actuator. The first detection pressure is a combined pressure of the detection pressure of the output pressure from the priority valve and the load detection pressure of the priority actuator taken out via the switching control valve. There, the output pressure from the priority valve, and has a most important characterized by being joined to the load sensing pressure of an actuator that is preferentially via a diaphragm.

Further, in the present invention, as described in claim 2, instead of the first detection pressure and the second detection pressure in claim 1, the detection pressure of the output pressure from the priority valve is given priority as the first detection pressure. The combined pressure of the detected pressure of the output pressure from the priority valve and the load detected pressure of the priority actuator taken out via the switching control valve is used as the second detected pressure. , The output pressure from the priority valve at the first detection pressure merges with the load detection pressure of the actuator to be prioritized via the throttle, and the output pressure from the priority valve at the second detection pressure via the throttle The most important feature is that the load detection pressure of the preferred actuator taken out via the switching control valve is merged .

  Furthermore, as described in claim 3, the present invention is characterized in that the output part of the control signal for controlling the switching control valve is specified.

  In the first invention of the present application, the oil supply stop state to the other actuators that are not prioritized, that is, the state in which the pump circuit is closed with respect to the other actuators, can be made by switching the switching control valve.

  When the switching control valve is opened, the detection pressure of the output pressure from the priority valve and the load detection pressure of the priority actuator are merged to become the first detection pressure. Thereby, a 1st detection pressure can be made into the said load detection pressure.

  At this time, the load detection pressure and the urging force act as the first operating pressure for switching the priority valve to the switching position side where the diversion to the other actuator is stopped. Further, as the second operating pressure for switching the priority valve to the switching position side where the flow is divided to other actuators, the detection pressure of the output pressure from the priority valve acts. Thereby, as a priority valve, the function as a normal priority valve can be show | played.

  When the switching control valve is switched and closed from this state, that is, when the first detection pressure is a detection pressure detected from the priority valve, the detection pressure detected from the priority valve is: The first detection pressure and the second detection pressure act on the priority valve.

  For this reason, the priority valve is switched to a position where oil supply to the other actuator is stopped by the biasing force of the spring at the first operating pressure. At this time, the priority valve stops supplying oil to the other actuators, and a state where the priority valve can supply oil only to the priority actuator is maintained.

  Further, since the output pressure from the priority valve is merged with the load detection pressure of the actuator that is prioritized via the throttle, the output pressure from the priority valve is the load of the actuator that is prioritized via the throttle. Can be supplied to the detection pressure detection line. Thereby, the output pressure from the priority valve depressurized by the throttle can be used as the load detection pressure of the priority actuator.

  In the second invention of the present application, the oil supply stop state to the other actuators that are not prioritized, that is, the state in which the pump circuit is closed with respect to the other actuators, can be made by switching the switching control valve.

  When the switching control valve is opened, the load detection pressure of the priority actuator and the detection pressure of the output pressure from the priority valve merge to become the second detection pressure. At this time, the load detection pressure of the actuator is given priority as the second detection pressure. The first detection pressure is a combined pressure of the detection pressure of the output pressure from the priority valve and the load detection pressure of the priority actuator, and the load detection pressure of the priority actuator is the first detection pressure. For this reason, the first detection pressure and the second detection pressure are the same pressure.

  As a result, the priority valve is switched to a position where oil supply to other actuators is stopped by the biasing force of the spring acting on the priority valve as the first operating pressure. As the priority valve, the oil supply to the other actuators is stopped, and the state where the oil can be supplied only to the priority actuator is maintained.

  When the switching control valve is closed, the second detection pressure becomes the detection pressure of the output pressure from the priority valve, and the first detection pressure is given priority to the load detection pressure of the actuator in the same manner as when the switching control valve is opened. It becomes.

  As a result, the load detection pressure of the priority actuator and the biasing force of the spring act as the first operating pressure for switching the priority valve to the switching position side where the diversion to other actuators is stopped. Further, as the second operating pressure for switching the priority valve to the switching position side where the flow is divided to other actuators, the detection pressure of the output pressure from the priority valve acts. For this reason, the priority valve can function as a normal priority valve.

  Since the present invention is configured as described above, a circuit for draining the output pressure supplied from the priority valve to the other actuators, which is necessary for closing the output pressure with respect to the other actuators not prioritized as in the prior art. No configuration is required. In addition, it is possible to prevent wasteful use of oil such as returning the output pressure from the priority valve to the tank as it is conventionally.

  In addition, in the conventional switching control valve arranged to return the pressure oil output from the priority valve to the other actuators to the tank as it is, a switching control valve that can perform switching control of a large flow rate must be used. did not become. On the other hand, in the present invention, the flow rate switched by the switching control valve is a small flow rate flowing as the load detection pressure. Therefore, in the present invention, a switching control valve for small flow rate can be used.

  As a result, the space for installing the switching control valve can be reduced, and the responsiveness as the switching control valve can be improved. Moreover, it is possible to use a switching control valve that is lower in cost than a switching control valve that performs switching control of a large flow rate.

  With the configuration described in claim 3 of the present application, for example, when the operator leaves the driver's seat in the operation of the forklift, even if the work implement lever is operated, the work implement can be kept stationary. . The priority valve in this state is maintained at a switching position where only the priority actuator can be supplied with oil. In addition, for example, an actuator that drives and operates a steering wheel can be set as a priority actuator, and an actuator of a work machine can be set as another actuator.

  Preferred embodiments of the present invention will be specifically described below with reference to the accompanying drawings. The configuration of the hydraulic system of the present invention will be described below by taking a hydraulic system in a forklift as an example. However, the hydraulic system of the present invention is not limited to the hydraulic system of the forklift, and the hydraulic system of the present invention is applied. The present invention can be applied to various hydraulic systems that can be used.

  FIG. 1 is a hydraulic circuit diagram according to the first embodiment of the present invention. The figure shows a hydraulic circuit in which the actuator for driving the steering of the forklift is given priority and the lift cylinders 13A, 13B for raising and lowering the fork and the tilt cylinders 20A, 20B for tilting the mast forward and backward are other actuators. Yes. The diversion to the priority actuator and the other actuators can be performed by the load pressure sensitive priority valve 3.

  The priority valve 3 has three ports 23 </ b> A to 23 </ b> C, and the port 23 </ b> C is connected to the variable displacement pump 1 through a pipe line 30. The port 23 </ b> A is connected to the port 24 </ b> E of the first direction switching valve 8 through the pipe line 38 and is connected to the port 25 </ b> D of the second direction control valve 17 through the check valve 16. The port 23B is connected to an actuator for driving a steering (not shown) via a pipe line 32, and can supply the discharge pressure oil of the variable displacement pump 1 for a priority actuator.

  The priority valve 3 can be switched to three positions from the first position 3-1 to the third position 3-3. The first position 3-1 stops the supply of the output pressure to the pipeline 38 that is a supply pipeline to the other actuators, and the output pressure to the pipeline 32 that is the supply pipeline to the preferred actuator. It is a position that can supply.

  The second position 3-2 is a position where the output pressure can be supplied to the pipe line 38 and the pipe line 32. The third position is a position where the output pressure can be supplied to the pipe line 38 and the output pressure is supplied to the pipe line 32 through a throttle.

  The output pressure output from the priority valve 3 to the pipe 32 is supplied to a steering operation actuator (not shown) that is a priority actuator. The pressure in the pipe line 32 is detected as a detected pressure through a pilot line 33, a throttle 52 and a throttle 50 disposed in the pilot pipe 34, respectively.

  Further, the output pressure in the pipe line 32 communicates with the load pressure detection line 35 through a pilot pipe line 34-1 and a throttle 57. The output pressure in the pipe line 32 decompressed by the throttle 57 can be the load detection pressure of the actuator that has priority.

  The pilot line 34 merges with the pilot line 36 branched from the load pressure detection line 35, and is connected to one end of the priority valve 3 through the throttle 51. The pressure oil passing through the throttle 51 acts as a first detection pressure and acts on the priority valve 3 together with the urging force of the spring 4. The first detection pressure and the biasing force of the spring 4 become the first operating pressure, and the priority valve 3 can be switched to the first position 3-1 side in FIG.

  An electromagnetic switching control valve 5 is disposed in the pilot line 36, and can be switched between a valve opening state and a valve closing state by exciting or de-energizing the magnetic coil 7 of the electromagnetic switching control valve 5. FIG. 1 shows a state where the electromagnetic coil 7 is in a non-excited state and the electromagnetic switching control valve 5 closes the pilot line 36.

  The second detection pressure obtained via the throttle 52 arranged in the pilot line 33 acts to switch the priority valve 3 to the third position 3-3 side in FIG. 1, contrary to the first detection pressure. ing. When the electromagnetic switching control valve 5 is in the open state, the detected pressure in the pilot line 34 becomes equal to the load detected pressure in the load detected pressure line 35.

  At this time, the load detection pressure in the load detection pressure line 35 and the biasing force of the spring 4 are acting as the first operating pressure for switching the priority valve 3 to the first position 3-1. Further, as the second operating pressure for switching the priority valve 3 to the third position 3-3, the output pressure in the pipe line 32 supplied to the steering operation actuator of the steering acts as the second detection pressure.

  When the differential pressure between the second operating pressure and the first operating pressure is greater than or equal to a preset differential pressure for driving the steering drive actuator, the priority valve 3 is driven by the second operating pressure according to the differential pressure. The second position 3-1 is switched to the second position 3-2 and the third position 3-3. Thereby, the pressure oil more than the flow rate required to drive the steering drive operation actuator can be supplied from the pipe line 38 to the lift cylinders 13A and 13B and / or the tilt cylinders 20A and 20B.

  Further, when the electromagnetic switching control valve 5 is switched from this state to close the valve, that is, the pilot pipe line 36 and the load pressure detection line 35 are in a non-conductive state, both the first detection pressure and the second detection pressure are the pipe line. It becomes the pilot pressure in 32, and becomes equal pressure.

  For this reason, the priority valve 3 is switched to the first position 3-1 by the biasing force of the spring 4, and the first position 3-1 state is maintained. As a result, the priority valve 3 is in a state of stopping oil supply to the lift cylinders 13A and 13B and / or the tilt cylinders 20A and 20B, which are other actuators. Further, the priority valve 3 can supply oil only to the actuator to be prioritized, and is maintained in a state of communicating only with the pipe line 32.

  As the switching control of the electromagnetic switching control valve 5, for example, switching control can be performed by a seating confirmation switch installed in the driver's seat. That is, when it is detected by the seating confirmation switch that the driver is seated in the driver's seat, the electromagnetic coil 7 of the electromagnetic switching control valve 5 is energized to be in the conductive state, and the pilot line 36 and the load pressure are set. The detection line 35 can be in a conductive state.

  When it is detected by the seating confirmation switch that the driver has left the driver's seat, the electromagnetic coil 7 of the electromagnetic switching control valve 5 is de-energized as shown in FIG. 5 spools can be moved to the closed state. At this time, the pilot line 36 and the load pressure detection line 35 are in a non-conductive state, the first detection pressure and the second detection pressure are substantially equal to each other, and the priority valve 3 is first driven by the biasing force of the spring 4. It will be maintained at position 3-1. Thereby, when the driver is away from the driver's seat, the work machine can be kept in an inoperable state.

  The switching control valve for bringing the load pressure detection line and the pilot pipe line 36 into a conducting state and a non-conducting state is not limited to an electromagnetic switching control valve, and other switching control valves can be used. Further, the switching control valve can be turned on by an ON signal, or the switching control valve can be turned on by an OFF signal.

  Further, the control signal for controlling the electromagnetic switching control valve 5 is not limited to the one by the seating confirmation switch arranged in the driver's seat, and the detection signal by the other detection switch is used as the control signal for the electromagnetic switching control valve. It is also possible to perform control for the electromagnetic switching control valve using other control signals.

  The pressure oil discharged from the variable displacement pump 1 to the conduit 30 acts on one end surface of the pump displacement control valve 2 through the pilot conduit 31. The other end face of the pump displacement control valve 2 has the highest load among the load pressure of the actuator for driving the steering, the load pressure of the lift cylinders 13A and 13B, and the load pressure of the tilt cylinders 20A and 20B. Pressure is acting through the maximum load pressure sensing line 48.

  As a result, the pump displacement control valve 2 can be controlled according to the differential pressure between the hydraulic pressure of the conduit 30 and the maximum load pressure among the load pressures of the actuator, and the variable displacement pump can be controlled according to the differential pressure. 1 protruding flow rate can be controlled.

  Among the load pressure detection lines 45 of the tilt cylinders 20A and 20B and the load pressure detection lines 44 and 46 of the lift cylinders 13A and 13B, the pressure oil on the high pressure side is led to the load pressure detection line 47 by the shuttle valve 21. Of the load pressure detection line 47 and the load pressure detection line 35 of the actuator for driving the steering, the high pressure side hydraulic pressure is led to the maximum load pressure detection line 48 by the shuttle valve 22. As a result, the highest load pressure among the load pressures of the actuator can be applied to the pump displacement control valve 2.

  The first direction switching valve 8 has seven ports 23A to 24G, and has a spool that is divided into a first spool 11A and a second spool 11B. The ports 24B and 24D of the first direction switching valve 8 merge on the downstream side, pass through the pipeline 39 through the pilot check valve 12, and are connected to the lift cylinders 13A and 13B.

  The port 24 </ b> A is a port connected via the pressure oil chamber of the pilot check valve 12 and the electromagnetic switching control valve 15. A pilot pipe 37 branched from the steering load pressure detection line 35 is connected to the pilot check valve 12, and the hydraulic pressure output from the port 24B of the first directional control valve 8 is equal to or higher than the steering load detection pressure. The hydraulic pressure output from the port 24B can be supplied to the lift cylinders 13A and 13B when the load pressure of the lift cylinders 13A and 13B that are currently applied becomes higher than the load pressure.

  The port 24C supplies the output pressure supplied to the lift cylinders 13A and 13B to the shuttle valve 21 through the pilot line 46 as pilot pressure when the first directional control valve 8 is in the first position 8-1. It has become a port that can.

  The ports 24E and 24G are used as ports for discharging the back pressure discharged from the lift cylinders 13A and 13B to the drain conduit 43, and are also used as ports for operating the second pressure 11B as a pilot pressure on the second spool 11B. Is done. Based on the pilot pressure from the ports 24E and 24G, the second spool 11B can be moved to the left in FIG. 1 against the biasing force of the spring 10.

  That is, the lift control lever 9 of the first direction switching valve 8 is operated to switch the first direction switching valve 8 to the third position 8-3, and the electromagnetic switching control valve 15 is controlled to connect the pilot line 44 to the first. The direction switching valve 8 is communicated with the port 24A. At this time, the back pressure discharged from the ports 24G and 24E to the drain conduit 43 can be controlled to move the second spool 11B to the left direction in FIG.

  As a result, the flow rate of the pressure oil discharged from the port 24D is controlled by the pilot pressure acting on the second spool 11B. That is, the first direction switching valve 8 can have a flow control characteristic for the port 24D, and the lowering of the lift cylinders 13A and 13B can be controlled by the first direction control valve 8.

  The lift cylinder 13 </ b> A and the lift cylinder 13 </ b> B are connected via a descending safety valve 14 disposed in the pipe line 40. For example, the lowering safety valve 14 functions to stop the lowering of the lift cylinder 13B even when the lift cylinder 13A is lowered when the pipeline 39 or the like is damaged.

  FIG. 1 shows an example in which the first direction control valve 8 is provided with a flow control valve function. However, by providing a flow control valve in the pipeline 39, the lift cylinder 13A and the lift cylinder 13B are connected to each other. When the load pressure is large, it is possible to prevent the fork descending speed from becoming excessive when the fork is lowered.

  The operation of the tilt cylinders 20A and 20B can be controlled by switching the pressure oil in the pipe line 38 output from the priority valve 3 from the port 25D to the port 25A or the port 25B in the second direction switching valve 17. The pressure oil discharged from the tilt cylinders 20 </ b> A and 20 </ b> B can return to the tank 27 from the drain pipe 43 through the pipe 41 or the pipe 42.

  FIG. 2 shows a hydraulic circuit diagram in the second embodiment according to the present invention. Of the configurations in the second embodiment, the same reference numerals as those used in the first embodiment are used for the same configurations as the first embodiment, and the description thereof is omitted.

  In the second embodiment, the pilot pipe line 67 connected to the load pressure detection line 35 via the electromagnetic switching control valve 5 and the pilot pipe line 66 using the output pressure in the pipe line 32 as the detection pressure are merged, and the restriction is made. 60 is connected to the priority valve 3 as a second detection pressure.

  In addition, the pilot line 69 using the output pressure in the line 32 as a detection pressure and the pilot line 68 connected to the load pressure detection line 35 merge, and the first detection pressure is supplied to the priority valve 3 via the throttle 58. Connected.

  A restrictor 59 is disposed in the pilot conduit 66 upstream of the junction of the pilot conduit 66 and the pilot conduit 67, and a restrictor 54 is disposed in the pilot conduit 69. Other configurations in the second embodiment are the same as those in the first embodiment.

  FIG. 2 shows the time when the electromagnetic switching control valve 5 is open. When the electromagnetic switching control valve 5 is opened by exciting the electromagnetic coil 7 now, the pressure upstream of the throttle 60 in the pilot line 66 becomes equal to the load detection pressure in the load detection pressure line 35. That is, at this time, the second detection pressure is the load detection pressure of the load pressure detection line 35.

  On the other hand, since the pilot pipe line 69 and the load pressure detection line 35 communicate with each other through the pilot pipe line 68, the pressure in the pilot pipe line 69 becomes equal to the load detection pressure of the load pressure detection line 35. For this reason, the first detection pressure and the second detection pressure become the same pressure, and the priority valve 3 is operated by the urging force of the spring 4.

  As a result, the priority valve 3 is switched to the first position 3-1 by the biasing force of the spring 4, and the switched first position 3-1 state is maintained. The priority valve 3 is in a state where the oil supply to the lift cylinders 13A, 13B and / or the tilt cylinders 20A, 20B, which are other actuators, is stopped, and only the priority actuator can be supplied with oil. The communication state can be maintained.

  When the electromagnetic coil 7 is de-energized and the electromagnetic switching control valve 5 is closed by the urging force of the spring 6, the communication state with the load pressure detection line 35 that has been in communication with the pilot line 66 is cut off, and the pilot line The pressure in 66 is a pressure using the output pressure of the pipe line 32 as a detection pressure. As a result, as the second operating pressure at which the priority valve 3 is switched to the third position 3-3, the output pressure in the pipe line 32 is guided to the pilot pipe line 66 and acts as the second detection pressure.

  On the other hand, since the pilot line 69 is in communication with the load pressure detection line 35, the pressure in the pilot line 69 is equal to the load detection pressure of the load pressure detection line 35. As a result, the load detection pressure of the load pressure detection line 35 and the urging force of the spring 6 act as the first operating pressure. Therefore, the priority valve 3 functions normally as a normal priority valve.

  That is, when the differential pressure between the second operating pressure and the first operating pressure is greater than or equal to a preset differential pressure for driving the steering operation actuator of the steering, the priority valve 3 responds to the second operating pressure. Thus, the second position 3-1 is switched to the second position 3-2 and the third position 3-3. Thereby, the pressure oil more than the flow rate required to drive the steering drive operation actuator can be supplied to the lift cylinders 13A, 13B and / or the tilt cylinders 20A, 20B from the pipe line 38.

  As described in the first embodiment, the switching control of the electromagnetic switching control valve 5 is performed by the detection signal detected by the seating confirmation switch installed in the driver's seat or the control signal from the control device. Can do.

  The present invention can apply the technical idea of the present invention to a hydraulic system using a priority valve.

It is a hydraulic circuit diagram. Example 1 It is a hydraulic circuit diagram. (Example 2) It is a hydraulic circuit diagram. (Conventional example)

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Variable displacement pump 2 Pump displacement control valve 3 Priority valve 5 Electromagnetic switching control valve 7 Electromagnetic coil 8 1st direction switching valve 11A 1st spool 11B 2nd spool 12 Pilot check valve 13A, 13B Lift cylinder 14 Lowering safety valve 15 Electromagnetic switching Valve 17 Second direction switching valve 20A, 20B Tilt cylinder 23A-23C Port 24A-24G Port 27 Tank 28 Relief valve 29 Check valve 30 Line 32 Line 33, 34 Pilot line 34-1 Line 35 Load pressure detection line 36, 37 Pilot line 43 Drain line 48 Maximum load pressure detection line 80 Priority valve mechanism 81A, 81B Switching valve mechanism 82A, 82B Switching valve 83 Parallel line 84 Tank line 85 Emergency valve block 87 Priority valve body 88A, 88B Valve section 89A, 89B operation Part 90 Emergency valve 91 Unload path 92 Pilot path 94 Flow control valve 96 Lift cylinder 97 Output port 98 Tilt cylinder 102 Load pressure 3-1 First position 3-2 Second position 3-3 Third position 8-1 First Position 8-2 Second position 8-3 Third position

Claims (3)

Using a load pressure sensitive type priority valve that diverts the priority actuator and at least one other actuator, and prioritizes the diversion to the priority actuator,
Of the operating pressures that actuate the priority valve, the first detection pressure and the biasing force of the spring are applied as the first operating pressure that switches to the switching position side that stops the diversion to the other actuator.
A second detection pressure that is a detection pressure of an output pressure from the priority valve is applied as a second operating pressure to be switched to a switching position side that performs a diversion to the other actuator;
The first detection pressure is a merged pressure between a detection pressure of the output pressure from the priority valve and a load detection pressure of the priority actuator taken out via the switching control valve;
The hydraulic system, wherein the output pressure from the priority valve is merged with a load detection pressure of an actuator that is prioritized through a throttle. Using a load pressure sensitive type priority valve that diverts the priority actuator and at least one other actuator, and prioritizes the diversion to the priority actuator,
Of the operating pressures that actuate the priority valve, the first detection pressure and the biasing force of the spring are applied as the first operating pressure that switches to the switching position side that stops the diversion to the other actuator.
As the second operating pressure to be switched to the switching position side for performing the diversion to the other actuator, the second detection pressure is applied,
The first detection pressure is a combined pressure of a detection pressure of an output pressure from the priority valve and a load detection pressure of the priority actuator;
The output pressure from the priority valve at the first detection pressure is merged with the load detection pressure of the actuator that is prioritized via the throttle,
The second detection pressure is a merging pressure between a detection pressure of the output pressure from the priority valve and a load detection pressure of the priority actuator taken out via the switching control valve;
The hydraulic system, wherein an output pressure from the priority valve at the second detection pressure is merged with a load detection pressure of the priority actuator taken out via the switching control valve via a throttle . The hydraulic system according to claim 1 or 2, wherein the switching control valve is controlled by a seating confirmation detection switch arranged in a driver's seat.

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