JP6466824B2 - Hydraulic motor control device - Google Patents

Description

  The present invention relates to a hydraulic motor control device.

  2. Description of the Related Art Conventionally, in a drive control circuit for a cooling fan hydraulic motor in a construction machine, a drive control circuit is known that avoids a sudden increase in circuit pressure when the fan is reversely rotated (see, for example, Patent Document 1). ).

  A drive control circuit described in Patent Document 1 includes a switching valve that switches between normal rotation and reverse rotation of a hydraulic motor that drives a fan, a variable relief valve that is provided in the hydraulic motor drive circuit and can change a relief pressure, a switching valve, And a controller for switching and controlling the variable relief valve. A controller outputs a control signal to an electromagnetic valve that supplies a control pressure to the switching valve and a variable relief valve. When the rotational direction of the hydraulic motor is switched, the controller outputs a relief pressure lowering signal to the variable relief valve, and outputs a switching signal to the switching valve after the number of rotations of the hydraulic motor has decreased.

Japanese Patent No. 4390201

  However, in the technique described in Patent Document 1, since a control signal is individually given from the controller to the switching valve and the variable relief valve, two signal lines are required. As a result, reliability such as disconnection failure is reduced.

  A hydraulic motor control device according to the present invention switches a direction of flow of pressure oil from a hydraulic pump to rotate a hydraulic motor for driving a cooling fan forward and backward, and is supplied from the hydraulic pump to the hydraulic motor. A variable relief valve for controlling the pressure of the driving pressure oil to be below a relief set pressure, an electromagnetic valve for outputting a switching control pressure for switching the rotational direction control valve from an outlet port, and a switching control signal for the electromagnetic valve. And a controller for outputting a relief pressure control unit that receives the switching control pressure and controls a relief setting pressure of the variable relief valve based on the switching control pressure, the relief pressure control The relief set pressure is controlled by the control unit at least during switching from reverse rotation to normal rotation and during switching from normal rotation to reverse rotation. The relief set pressure of the relief valve, is lower than a preset relief set 圧初 life values, characterized in that it is a control to then return to the relief setting 圧初 life values.

  According to the present invention, since no signal line is required between the relief pressure control unit and the controller, reliability can be improved.

FIG. 1 is a diagram showing a wheel loader equipped with a hydraulic motor control device according to an embodiment of the present invention. FIG. 2 is a schematic diagram of a hydraulic circuit for driving the hydraulic motor. FIG. 3 is a diagram illustrating the operation of the relief pressure control unit in the first embodiment. FIG. 4 is a diagram showing a change in the relief set pressure when the rotation direction is switched. FIG. 5 is a diagram illustrating a modification of the first embodiment. FIG. 6 is a diagram illustrating a second embodiment. FIG. 7 is a diagram for explaining the operation of the relief pressure control unit in the second embodiment. FIG. 8 is a diagram illustrating a third embodiment. FIG. 9 is a diagram for explaining the operation of the relief pressure control unit in the third embodiment.

  Hereinafter, a hydraulic motor control device according to an embodiment of the present invention will be described in detail with reference to the drawings. Hereinafter, a wheel loader will be described as an example of a work machine on which the hydraulic motor control device is mounted. However, the present invention is not limited to a wheel loader and can be applied to hydraulic motor control devices of various work machines.

-First embodiment-
FIG. 1 is a diagram showing a wheel loader 200 equipped with a hydraulic motor control device according to an embodiment of the present invention. The wheel loader 200 includes a front vehicle body 203 having an arm 201, a bucket 202, front wheels 101a, 101b, and the like, and a rear vehicle body 204 having an operator cab 102, an engine (not shown), rear wheels 101c, 101d, and the like. The arm 201 is pivoted up and down (up and down) by driving the arm cylinder 103. The bucket 202 is rotated (dumped or clouded) in the vertical direction by driving the bucket cylinder 104. Hereinafter, the front wheels 101a and 101b and the rear wheels 101c and 101d are collectively referred to as wheels 101.

  The front vehicle body 203 and the rear vehicle body 204 are rotatably connected to each other by a connecting shaft 205. The wheel loader 200 is an articulated work vehicle in which a front vehicle body 203 and a rear vehicle body 204 are bent by a connecting shaft 205. One end and the other end of a pair of steering cylinders 105 centering on the connecting shaft 205 are rotatably engaged with the front vehicle body 203 and the rear vehicle body 204, respectively. One of the pair of steering cylinders 105 is extended by a hydraulic device described later, and the other is retracted, thereby rotating the front vehicle body 203 and the rear vehicle body 204 around the connecting shaft 205, respectively. Thereby, the relative attachment angle of the front vehicle body 203 and the rear vehicle body 204 changes.

  The rear vehicle body 204 is provided with a cooling fan 3 and a hydraulic motor 4 for rotationally driving the fan 3. By rotating the fan 3, cooling air is blown to the radiator 10 and the oil cooler 11.

  FIG. 2 is a schematic diagram of a hydraulic circuit for driving the hydraulic motor 4. Cooling air obtained by rotationally driving the fan 3 with the hydraulic motor 4 is blown to the radiator 10 and the oil cooler 11. A fan circuit 5 that adjusts the direction and flow rate of pressure oil supplied to the hydraulic motor 4 is provided in an oil passage 7 that connects the hydraulic pump 2 and the hydraulic motor 4. The hydraulic pump 2 is axially connected to the engine 1 and is driven by the engine 1.

  Normally, the fan 3 is rotated forward, and the outside air that serves as cooling air is sucked from above in the figure. By the way, since dust is also sucked together with the outside air, the sucked dust may cause the radiator 10 to be clogged. In such a case, the fan 3 is rotated in the reverse direction to blow away the dust adhering to the radiator 10.

  The fan circuit 5 includes a pilot operated switching valve 51, a variable relief valve 52, an electromagnetic valve 53, a relief pressure control unit 5a, and check valves 56a and 56b. The switching valve 51 is a direction control valve that controls the direction of pressure oil sent from the hydraulic pump 2 to the hydraulic motor 4. A pilot pressure (hereinafter referred to as switching control pressure) input to the switching valve 51 is output from the electromagnetic valve 53.

  The electromagnetic valve 53 is an electromagnetic proportional pressure reducing valve, receives the control signal from the controller 6, makes the discharge pressure from the hydraulic pump 2 the primary pressure, and supplies the control pressure to the switching valve 51 and the variable relief valve 52. In the solenoid valve 53, the spool moves between the first position 53a and the second position 53b in accordance with a command value from the controller 6. When a forward rotation command is input from the controller 6, the spool moves to the first position 53a.

  When a reverse rotation command is input from the controller 6, the spool moves to a predetermined position between the first position 53a and the second position 53b, and the secondary pressure of the electromagnetic valve 53 is increased to the command value. Hereinafter, in order to simplify the description, it is assumed that the spool moves to the second position 53b at the time of a reverse rotation command. The secondary pressure when the forward rotation command is input is called a normal rotation control pressure, and the secondary pressure when the reverse rotation command is input is called a reverse rotation control pressure.

  When the normal rotation control pressure is input to the switching valve 51, the switching valve 51 becomes the normal rotation position 51a, the port 41 of the hydraulic motor 4 is connected to the oil passage 7, and the hydraulic motor 4 rotates forward. On the other hand, when the reverse rotation control pressure is input to the switching valve 51, the switching valve 51 becomes the reverse rotation position 51b, the port 42 of the hydraulic motor 4 is connected to the oil passage 7, and the hydraulic motor 4 rotates in the reverse direction.

  The check valves 56a and 56b prevent the occurrence of cavitation by introducing the pressure oil from the tank 8 into the port when the pressure at both ports of the hydraulic motor 4 falls below the drain pressure.

  The variable relief valve 52 is arranged on the oil passage 9 that branches from the oil passage 7 and guides the pressure oil from the hydraulic pump 2 to the tank 8, and defines the upper limit pressure of the pressure oil sent from the hydraulic pump 2 to the switching valve 51. . The upper limit pressure can be changed by controlling the relief set pressure of the variable relief valve 52. The variable relief valve 52 includes three pressure application ports A, B, and C, and a spring 52 a is provided to face the pressure application port A. A discharge pressure of the hydraulic pump is guided to the pressure application port A through the oil passages 7 and 9. The secondary pressure of the electromagnetic valve 53 is guided to the pressure application port B facing the spring 52a and the pressure application port C facing the pressure application ports A and B via the relief pressure control unit 5a.

  The relief pressure control unit 5 a adjusts the relief set pressure, and guides the secondary pressure of the electromagnetic valve 53 to the pressure application ports B and C of the variable relief valve 52. The relief pressure control unit 5a is provided between the pressure application port C and the outlet port (that is, the secondary pressure side) of the solenoid valve 53, and the secondary throttle of the solenoid valve 53 from the first throttle 54c and the pressure application port C. Provided between the first control unit 50a connected in parallel with the first check valve 55c allowing the flow of pressure oil to the pressure side, the pressure application port B and the outlet port of the electromagnetic valve 53, The second control unit 50b is connected in parallel with the throttle 54b and a second check valve 55b that allows the flow of pressure oil from the secondary pressure side of the solenoid valve 53 to the pressure application port B.

(Description of operation of relief pressure control unit 5a)
Next, the control of the relief set pressure by the relief pressure control unit 5a will be described with reference to FIGS. FIG. 3 is a diagram for explaining the operation of the relief pressure control unit 5a when the switching valve 51 is switched to reverse the rotation direction of the hydraulic motor 4. FIG. 3A shows the case where the normal rotation is switched to the reverse rotation, and FIG. 3B shows the case where the reverse rotation is switched to the normal rotation. 4A and 4B are diagrams showing changes in the relief set pressure when the rotation direction is switched, wherein FIG. 4A shows the time change in pressure at the pressure application ports B and C, and FIG. 4B shows the time change in the relief set pressure. Indicates.

  First, the case where the rotation direction of the hydraulic motor 4 is switched from the normal rotation state shown in FIG. 2 to the reverse rotation direction will be described. In the forward rotation state shown in FIG. 2, the secondary pressure of the electromagnetic valve 53 is the drain pressure P0 as in the situation at time t = 0 in FIG. 4A, and the pressure application ports B, The pressure of C is also the drain pressure P0.

  When a control signal instructing reverse rotation is output from the controller 6 to the electromagnetic valve 53 at time T1 in FIG. 4, the spool of the electromagnetic valve 53 moves to the second position 53b as shown in FIG. The secondary pressure of the solenoid valve 53 is increased to the command value. The secondary pressure at this time is set as the reverse control pressure P1. As a result, the switching valve 51 is switched from the forward rotation position 51 a to the reverse rotation position 51 b, and the oil passage 7 is connected to the port 42 of the hydraulic motor 4.

  When the secondary pressure of the solenoid valve 53 rises to the reverse control pressure P1, the check valve 55b is opened, and the secondary pressure (reverse control pressure P1 of the solenoid valve 53 is connected to the pressure application port B of the variable relief valve 52 via the check valve 55b. ) Is introduced. The pressure Pb at the pressure application port B is raised to the reverse control pressure P1 without time delay as indicated by the solid line L1 in FIG. On the other hand, since the secondary pressure of the electromagnetic valve 53 is introduced into the pressure application port C of the variable relief valve 52 through the throttle 54c, as shown by the broken line L2 in FIG. The pressure is increased with a response delay corresponding to the throttle diameter and the pressure chamber volume of the pressure application port C.

  At this time, a force proportional to the differential pressure Pb-Pc acts as a force facing the spring 52a. The pressure receiving areas of the pressure application port B and the pressure application port C are set equal. Therefore, the relief setting pressure Pr of the variable relief valve 52 is a relief setting defined by the force applied to the pressure application port A (the discharge pressure of the hydraulic pump 2 in the case of FIG. 2) and the spring force of the spring 52a. This is a value obtained by subtracting the pressure ΔP proportional to the differential pressure Pb−Pc from the initial pressure value Pr0. Therefore, at time T1, the relief set pressure Pr of the variable relief valve 52 once decreases greatly to the pressure value Pr1, and then gradually increases to return to the relief set pressure initial value Pr0.

  In this way, when the forward rotation is switched to the reverse rotation, the relief set pressure Pr once decreases greatly to the pressure value Pr1, so that the pressure oil in the oil passage 7 is relieved via the variable relief valve 52, and the pressure in the oil passage 7 is increased. Decreases. As a result, the circuit pressure can be kept low until the rotational speed of the hydraulic motor 4 that rotates forward due to inertia decreases.

  By the way, in the conventional hydraulic excavator, even if the switching valve 51 is switched from the forward rotation position 51a to the reverse rotation position 51b at time T1, the hydraulic motor 4 does not immediately reversely rotate, but immediately after switching, due to inertia. I am doing. When the oil passage 7 is connected to the port 42 of the hydraulic motor 4 in the forward rotating state in this way, an excessive load is generated because the flow of the pressure oil supplied to the hydraulic motor 4 suddenly reverses. Or noise is generated.

  However, in the configuration shown in FIGS. 2 and 3, as shown in FIG. 4B, immediately after the reverse rotation, the relief set pressure Pr once drops greatly to the pressure value Pr 1, the variable relief valve 52 is relieved, and the oil passage 7 Since the pressure is reduced, it is possible to prevent the generation of excessive load and noise as described above.

  Next, a case where the rotation direction of the hydraulic motor 4 is switched from the reverse rotation state to the normal rotation state will be described. In the reverse rotation state, the switching valve 51 is in a state as shown in FIG. When a control signal (OFF signal) instructing the normal rotation to the electromagnetic valve 53 is output from the controller 6 at time T2 in FIG. 4, the spool of the electromagnetic valve 53 is in the first state as shown in FIG. Moving to the position 53a, the secondary pressure of the electromagnetic valve 53 is dropped to the drain pressure (forward rotation control pressure) P0. As a result, the switching valve 51 is switched from the reverse rotation position 51b to the normal rotation position 51a, and the oil passage 7 is connected to the port 41 of the hydraulic motor 4.

  When the secondary pressure decreases to the normal rotation control pressure P0, the check valve 55c is opened, and the pressure application port C of the variable relief valve 52 is connected to the secondary pressure side of the electromagnetic valve 53 via the check valve 55c. Immediately before time T2, the value of the pressure Pc at the pressure application port C is the reverse control pressure P1, but when the check valve 55c is opened at time T2, as shown by the line L2 in FIG. The rolling control pressure (drain pressure) decreases to P0. On the other hand, since the pressure application port B of the variable relief valve 52 is connected to the secondary pressure side of the electromagnetic valve 53 via the throttle 54b, as shown by the line L1 in FIG. 4A, the throttle diameter of the throttle 54b. The pressure is reduced with a response delay corresponding to the pressure chamber volume of the pressure application port B.

  As a result, at time T2, the relief set pressure Pr of the variable relief valve 52 decreases once to the pressure value Pr1, and then gradually increases to return to the relief set pressure initial value Pr0. Thus, even when switching from reverse rotation to normal rotation, the relief set pressure Pr once decreases greatly to the pressure value Pr1, so that the pressure oil in the oil passage 7 is relieved via the variable relief valve 52 and the oil passage 7 The pressure drops. As a result, the circuit pressure can be kept low until the rotational speed of the hydraulic motor 4 that reverses due to inertia decreases.

As described above, in the present embodiment, the relief set pressure of the variable relief valve 52 is set to a preset relief set pressure initial value at the time of switching from forward rotation to reverse rotation and at the time of switching from reverse rotation to normal rotation. The pressure is lowered below Pr0, and thereafter, the pressure is returned to the relief set pressure initial value Pr0. As a result, when the rotation direction of the hydraulic motor 4 is reversed, it is possible to suppress a rapid increase in circuit pressure, and it is possible to prevent an excessive load or noise.
The

  In particular, as shown in FIG. 4 (b), the relief set pressure of the variable relief valve 52 is once lowered from the preset relief set pressure initial value Pr0, and is delayed to a relief set pressure initial value Pr0. By gradually increasing the pressure so as to return, the circuit pressure can be kept low until the rotational speed of the hydraulic motor 4 is sufficiently reduced.

  As described above, the relief pressure control unit 5a sets the relief set pressure of the variable relief valve 52 according to the secondary pressure of the electromagnetic valve 53 that is the switching control pressure of the switching valve 51, as shown in FIG. Adjustment is performed to prevent a rapid increase in circuit pressure when the rotation direction of the hydraulic motor 4 is reversed. Thus, since the relief pressure control unit 5a is configured to operate by the secondary pressure of the electromagnetic valve 53 used as the pilot pressure of the switching valve 51, the signal line from the controller 6 requires only one system related to the electromagnetic valve 53. . Therefore, the reliability can be improved as compared with the conventional configuration requiring two signal lines.

  In the embodiment described above, the relief set pressure of the variable relief valve 52 is set from the preset relief set pressure initial value Pr0 once when switching from forward rotation to reverse rotation and when switching from reverse rotation to forward rotation. After that, the relief set pressure initial value Pr0 is returned to the initial value Pr0, but it may be applied to at least one of switching from forward rotation to reverse rotation and switching from reverse rotation to forward rotation. good.

(Modification of the first embodiment)
FIG. 5 is a diagram illustrating a modification of the first embodiment. The primary pressure of the electromagnetic valve 53 is led from a pilot hydraulic power source 12 provided separately from the hydraulic pump 2. About another structure, it is the same as that of the structure shown in FIG. 2 of 1st Embodiment mentioned above. With this configuration, in addition to the operational effects of the first embodiment described above, the circuit pressure of the drive control circuit that drives the hydraulic motor 4 is maintained at the pressure required for valve switching of the switching valve 51. Therefore, it is possible to provide a circuit with lower energy consumption.

-Second Embodiment-
FIG. 6 is a diagram illustrating a second embodiment. In the second embodiment, the configuration of the relief pressure control unit 5a is different from that of the first embodiment, and other configurations are the same as in the case of the first embodiment. In the configuration shown in FIG. 6, the primary pressure of the electromagnetic valve 53 is led from the pilot hydraulic power source 12 as in the configuration of FIG. 5 shown in the modification of the first embodiment. You may comprise so that it may guide from 2.

  The relief pressure control unit 5 a shown in FIG. 6 includes a first switching valve 57 and a second switching valve 58. The first switching valve 57 is provided between the pressure application port C and the outlet port of the electromagnetic valve 53 (that is, the secondary pressure side). The first switching valve 57 includes a first switching position 57a when the pressure at the pressure application port C is higher than the pressure at the secondary pressure side of the solenoid valve 53, and the pressure at the secondary pressure side of the solenoid valve 53 at the pressure application port C. And a second switching position 57b when the pressure is higher than the pressure. The pressure of the pressure application port C of the variable relief valve 52 is guided as a pilot pressure to the first switching position 57a side of the spool of the first switching valve 57, and the electromagnetic pressure as the pilot pressure is introduced to the second switching position 57b side of the spool. The secondary pressure of the valve 53 is guided. At the first switching position 57a, the pressure application port C and the secondary pressure side of the solenoid valve 53 are connected, and at the second switching position 57b, the pressure application port C and the secondary pressure side of the solenoid valve 53 are connected via the throttle 570. Connected.

  The second switching valve 58 is provided between the pressure application port B and the outlet port of the electromagnetic valve 53 (that is, the secondary pressure side). The second switching valve 58 includes a first switching position 58a when the pressure at the pressure application port B is higher than the pressure at the secondary pressure side of the solenoid valve 53, and a pressure at the secondary pressure side of the solenoid valve 53 at the pressure application port B. And a second switching position 58b when the pressure is higher than the pressure. The pressure of the pressure application port B of the variable relief valve 52 is guided as a pilot pressure to the first switching position 58a side of the spool of the second switching valve 58, and the electromagnetic pressure as the pilot pressure is introduced to the second switching position 58b side of the spool. The secondary pressure of the valve 53 is guided. At the first switching position 58a, the pressure application port B and the secondary pressure side of the solenoid valve 53 communicate with each other through the throttle 580. At the second switching position 58b, the pressure application port B and the secondary pressure side of the solenoid valve 53 are connected.

  FIG. 7 is a diagram for explaining the operation of the relief pressure control unit 5a when the switching valve 51 is switched to reverse the rotation direction of the hydraulic motor 4. The change in the relief setting pressure when the rotation direction is switched will be described with reference to FIG. 4 described above.

(Operation during forward rotation → reverse rotation)
First, the case where the rotation direction of the hydraulic motor 4 is switched from the normal rotation state shown in FIG. 6 to the reverse rotation direction will be described. In the forward rotation state, the solenoid valve 53, the first switching valve 57, and the second switching valve 58 are in a state as shown in FIG. In this case, as in the situation at time t = 0 in FIG. 4A, the secondary pressure of the electromagnetic valve 53 is the normal rotation control pressure (drain pressure) P0 (<P1), and the pressure of the variable relief valve 52 The pressure at the application ports B and C is also the normal rotation control pressure P0.

  FIG. 7A shows a case where the normal rotation is switched to the reverse rotation. When a control signal instructing reverse rotation is output from the controller 6 to the electromagnetic valve 53 at time T1 in FIG. 4, the spool of the electromagnetic valve 53 moves to the second position 53b as shown in FIG. The secondary pressure of the electromagnetic valve 53 is increased to the command value (reverse control pressure P1). As a result, the switching valve 51 is switched from the forward rotation position 51 a to the reverse rotation position 51 b, and the oil passage 7 is connected to the port 42 of the hydraulic motor 4.

  When the secondary pressure of the electromagnetic valve 53 increases to the reverse control pressure P1, the pilot pressure on the second switching position 57b side of the first switching valve 57 to which the secondary pressure of the electromagnetic valve 53 is guided, and the second switching valve As a pilot pressure on the second switching position 58b side of 58, the secondary pressure (reverse control pressure P1) of the electromagnetic valve 53 is introduced. On the other hand, immediately after switching from forward rotation to reverse rotation (immediately after time T1), the pressure at the pressure application port B and the pressure application port C is substantially the pressure P0. As a result, as shown in FIG. 7A, the spools of the first switching valve 57 and the second switching valve 58 move downward in the figure, the first switching valve 57 is switched to the second switching position 57b, The two switching valve 58 is switched to the second switching position 58b.

  When the second switching valve 58 reaches the second switching position 58b, the pressure Pb of the pressure application port B is increased to the reverse control pressure P1 without time delay as shown by the solid line L1 in FIG. Further, when the first switching valve 57 reaches the second switching position 57 b, the secondary pressure of the electromagnetic valve 53 is introduced into the pressure application port C through the throttle 570. The pressure Pc of the pressure application port C is increased with a response delay corresponding to the diameter of the restriction 570 and the pressure chamber volume of the pressure application port C, as indicated by the broken line L2 in FIG. As a result, the relief set pressure Pr of the variable relief valve 52 immediately after time T1 changes as shown in FIG. 4B, as in the case of the first embodiment.

  In this way, when the forward rotation is switched to the reverse rotation, the relief set pressure Pr once decreases greatly to the pressure value Pr1, so that the pressure oil in the oil passage 7 is relieved via the variable relief valve 52, and the pressure in the oil passage 7 is increased. Decreases. As a result, the circuit pressure can be kept low until the rotational speed of the hydraulic motor 4 that rotates forward due to inertia decreases.

(Operation when reverse rotation → forward rotation)
Next, a case where the rotation direction of the hydraulic motor 4 is switched from the reverse rotation state to the normal rotation state will be described. In the reverse rotation state, the switching valve 51, the first switching valve 57, and the second switching valve 58 are in a state as shown in FIG. When a control signal (OFF signal) instructing the normal rotation to the electromagnetic valve 53 is output from the controller 6 at time T2 in FIG. 4, the spool of the electromagnetic valve 53 is in the first state as shown in FIG. 7B. Moving to the position 53a, the secondary pressure of the electromagnetic valve 53 is dropped to the normal rotation control pressure (drain pressure) P0. As a result, the switching valve 51 is switched from the reverse rotation position 51b to the normal rotation position 51a, and the oil passage 7 is connected to the port 41 of the hydraulic motor 4.

  When the secondary pressure of the electromagnetic valve 53 decreases to the normal rotation control pressure (drain pressure) P0, the pilot pressure on the second switching position 57b side of the first switching valve 57 to which the secondary pressure is guided, and the second The pilot pressure on the second switching position 58b side of the switching valve 58 becomes the normal rotation control pressure P0. On the other hand, immediately after switching from reverse rotation to normal rotation, the pressures at the pressure application port B and the pressure application port C are substantially the reverse control pressure P1. As a result, as shown in FIG. 7B, the spools of the first switching valve 57 and the second switching valve 58 move upward in the drawing, and the first switching valve 57 is switched to the first switching position 57a. The switching valve 58 is switched to the first switching position 58a.

  When the first switching valve 57 reaches the first switching position 57a at time T2, the pressure Pc at the pressure application port C decreases to the normal rotation control pressure P0 without time delay as shown by the line L2 in FIG. When the second switching valve 58 is in the first switching position 58 a, the pressure application port B of the variable relief valve 52 is connected to the secondary pressure side of the electromagnetic valve 53 via the throttle 580. The pressure Pb at the pressure application port B is reduced with a response delay corresponding to the restriction diameter of the restriction 580 and the pressure chamber volume of the pressure application port B, as indicated by the line L1 in FIG. As a result, the relief set pressure Pr of the variable relief valve 52 immediately after time T2 changes as shown in FIG. 4B, as in the case of the first embodiment.

  As a result, at time T2, the relief set pressure Pr of the variable relief valve 52 decreases once to the pressure value Pr1, and then gradually increases to return to the relief set pressure initial value Pr0. Thus, even when switching from reverse rotation to normal rotation, the relief set pressure Pr once decreases greatly to the pressure value Pr1, so that the pressure oil in the oil passage 7 is relieved via the variable relief valve 52 and the oil passage 7 The pressure drops. As a result, the circuit pressure can be kept low until the rotational speed of the hydraulic motor 4 that reverses due to inertia decreases.

-Third embodiment-
FIG. 8 is a diagram illustrating a third embodiment. In the third embodiment, the configuration of the relief pressure control unit 5a is different from that of the first embodiment, and other configurations are the same as in the case of the first embodiment. In the configuration shown in FIG. 8, the primary pressure of the electromagnetic valve 53 is led from the pilot hydraulic power source 12 as in the configuration of FIG. 5 shown in the modification of the first embodiment. You may comprise so that it may guide from 2.

  The relief pressure control unit 5 a includes a switching valve 59. The switching valve 59 includes a first switching position 59a when the pressure at the pressure application port B and the pressure application port C is higher than the pressure at the outlet port of the solenoid valve 53 (that is, the secondary pressure side), and the secondary position of the solenoid valve 53. And a second switching position 59b when the pressure-side pressure is higher than the pressure at the pressure application port B and the pressure application port C. At the first switching position 59a, the secondary pressure side of the solenoid valve 53 is connected to the pressure application port C, and the secondary pressure side of the solenoid valve 53 is connected to the pressure application port B via the throttle 591. At the second switching position 59 b, the secondary pressure side of the solenoid valve 53 and the pressure application port B are connected, and the secondary pressure side of the solenoid valve 53 and the pressure application port C are connected via the throttle 592.

(Operation during forward rotation → reverse rotation)
First, the case where the rotation direction of the hydraulic motor 4 is switched from the normal rotation state shown in FIG. 8 to the reverse rotation direction will be described. In the normal rotation state, the solenoid valve 53 and the switching valve 59 are in a state as shown in FIG. In this case, as in the situation at time t = 0 in FIG. 4A, the secondary pressure of the electromagnetic valve 53 is the normal rotation control pressure (drain pressure) P0 (<P1), and the pressure of the variable relief valve 52 The pressure at the application ports B and C is also the normal rotation control pressure P0.

  FIG. 9A shows a case where the normal rotation is switched to the reverse rotation. When a control signal instructing reverse rotation is output from the controller 6 to the electromagnetic valve 53 at time T1 in FIG. 4, the spool of the electromagnetic valve 53 moves to the second position 53b as shown in FIG. The secondary pressure of the electromagnetic valve 53 is increased to the command value (reverse control pressure P1). As a result, the switching valve 51 is switched from the forward rotation position 51 a to the reverse rotation position 51 b, and the oil passage 7 is connected to the port 42 of the hydraulic motor 4.

  When the secondary pressure of the solenoid valve 53 rises to the reverse control pressure P1, the secondary pressure of the solenoid valve 53 is used as the pilot pressure on the second switching position 59b side of the switching valve 59 to which the secondary pressure of the solenoid valve 53 is guided. (Reverse control pressure P1) is derived. On the other hand, the pilot pressure on the first switching position 59a side of the switching valve 59 connected to the pressure application port B and the pressure application port C is almost the normal rotation control pressure (drain pressure) P0 immediately after switching from normal rotation to reverse rotation. Therefore, the spool of the switching valve 59 moves downward in the figure, and the switching valve 59 is switched to the second switching position 59b.

  When the switching valve 59 reaches the second switching position 59b, the pressure Pb of the pressure application port B is increased to the pressure P1 without time delay as shown by the solid line L1 in FIG. On the other hand, the secondary pressure of the electromagnetic valve 53 is introduced into the pressure application port C through the throttle 592. The pressure Pc of the pressure application port C is increased with a response delay corresponding to the diameter of the restriction 592 and the pressure chamber volume of the pressure application port C, as indicated by the broken line L2 in FIG. As a result, the relief set pressure Pr of the variable relief valve 52 immediately after the time T1 changes as shown in FIG. 4B as in the case of the first embodiment.

  In this way, when the forward rotation is switched to the reverse rotation, the relief set pressure Pr once decreases greatly to the pressure value Pr1, so that the pressure oil in the oil passage 7 is relieved via the variable relief valve 52, and the pressure in the oil passage 7 is increased. Decreases. As a result, the circuit pressure can be kept low until the rotational speed of the hydraulic motor 4 that rotates forward due to inertia decreases.

(Operation when reverse rotation → forward rotation)
Next, a case where the rotation direction of the hydraulic motor 4 is switched from the reverse rotation direction to the normal rotation state will be described. In the reverse rotation state, the switching valves 51 and 59 are in a state as shown in FIG. When a control signal (OFF signal) instructing the normal rotation to the electromagnetic valve 53 is output from the controller 6 at time T2 in FIG. 4, the spool of the electromagnetic valve 53 is in the first state as shown in FIG. 9B. Moving to the position 53a, the secondary pressure of the electromagnetic valve 53 is dropped to the normal rotation control pressure (drain pressure) P0. As a result, the switching valve 51 is switched from the reverse rotation position 51b to the normal rotation position 51a, and the oil passage 7 is connected to the port 41 of the hydraulic motor 4.

  When the secondary pressure of the electromagnetic valve 53 is reduced to the normal rotation control pressure P0, the pilot pressure on the second switching position 59b side of the switching valve 59 to which the secondary pressure is guided becomes the normal rotation control pressure P0. On the other hand, in the direct switching from the reverse rotation to the normal rotation, the pressure at the pressure application port B and the pressure application port C is substantially the reverse rotation control pressure P1. As a result, as shown in FIG. 9B, the spool of the switching valve 59 moves upward in the drawing, and the switching valve 59 is switched to the first switching position 59a.

  When the switching valve 59 reaches the first switching position 59a at time T2, the pressure Pc of the pressure application port C decreases to the normal rotation control pressure P0 without time delay as shown by a line L2 in FIG. When the switching valve 59 is in the first switching position 59a, the pressure application port B of the variable relief valve 52 is connected to the secondary pressure side of the electromagnetic valve 53 via the throttle 591. The pressure Pb of the pressure application port B is reduced with a response delay according to the throttle diameter of the throttle 591 and the pressure chamber volume of the pressure application port B, as indicated by a line L1 in FIG. As a result, the relief set pressure Pr of the variable relief valve 52 immediately after time T2 changes as shown in FIG. 4B, as in the case of the first embodiment.

  As a result, at time T2, the relief set pressure Pr of the variable relief valve 52 decreases once to the pressure value Pr1, and then gradually increases to return to the relief set pressure initial value Pr0. Thus, even when switching from reverse rotation to normal rotation, the relief set pressure Pr once decreases greatly to the pressure value Pr1, so that the pressure oil in the oil passage 7 is relieved via the variable relief valve 52 and the oil passage 7 The pressure drops. As a result, the circuit pressure can be kept low until the rotational speed of the hydraulic motor 4 that reverses due to inertia decreases.

  In addition, the relief setting pressure at the time of forward rotation and the relief setting pressure at the time of reverse rotation may be made different by providing a difference in the pressure receiving areas of the pressure application port B and the pressure application port C of the variable relief valve 52. . For example, in the above-described embodiment, the fan 3 is reversed in order to blow away dust attached to the radiator 10. Therefore, by increasing the relief setting pressure and increasing the rotational speed of the hydraulic motor 4 during reverse rotation, it is possible to improve the dust removal effect by increasing the air volume.

  In addition, the above description is an example to the last, and this invention is not limited to the said embodiment at all unless the characteristic of this invention is impaired. Moreover, you may use embodiment mentioned above and each modification individually or in combination.

  DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Hydraulic pump, 3 ... Fan, 4 ... Hydraulic motor, 5 ... Fan circuit, 5a ... Relief pressure control part, 6 ... Controller, 7, 9 ... Oil path, 10 ... Radiator, 11 ... Oil cooler, DESCRIPTION OF SYMBOLS 51 ... Switching valve (rotation direction control valve), 50a ... 1st control part, 50b ... 2nd control part, 52 ... Variable relief valve, 53 ... Solenoid valve, 54a, 54b ... Restriction, 55a, 55b ... Check valve, 57 ... 1st switching valve, 57a, 59a ... 1st switching position, 57b, 59b ... 2nd switching position, 58 ... 2nd switching valve, 58a ... 1st switching position (3rd switching position), 58b ... 2nd switching position (Fourth switching position), 59 ... switching valve (third switching valve), A ... pressure application port (first pressure application port), B ... pressure application port (second pressure application port), C ... pressure application port ( (3rd pressure application port)

Claims (6)

A rotation direction control valve that switches the flow direction of the pressure oil from the hydraulic pump to forward and reverse the hydraulic motor for driving the cooling fan;
A variable relief valve for controlling the pressure of the driving hydraulic oil supplied from the hydraulic pump to the hydraulic motor to a relief setting pressure or less;
An electromagnetic valve that outputs a switching control pressure for switching the rotational direction control valve from an outlet port;
A controller that outputs a switching control signal of the solenoid valve, and a hydraulic motor control device comprising:
A relief pressure control unit configured to input the switching control pressure and control a relief setting pressure of the variable relief valve based on the switching control pressure;
Control of the relief set pressure by the relief pressure control unit is such that the relief set pressure of the variable relief valve is preset in at least one of switching from reverse rotation to normal rotation and switching from normal rotation to reverse rotation. A hydraulic motor control device, characterized in that the control is performed such that the pressure is lower than a relief set pressure initial value and then returned to the relief set pressure initial value. In the hydraulic motor control device according to claim 1,
In the control of the relief set pressure,
A hydraulic pressure characterized in that the relief set pressure of the variable relief valve is lowered from a preset relief set pressure initial value and gradually increased so as to return to the relief set pressure initial value with a time delay. Motor control device. In the hydraulic motor control device according to claim 1,
The solenoid valve controls the rotation direction control valve to the reverse rotation position, and the normal rotation control pressure for controlling the rotation direction control valve to the normal rotation position is different from the normal rotation control pressure as the switching control pressure. Output reverse control pressure,
The variable relief valve is
A first pressure application port that is opposed to a spring that biases the valve body and to which a pump pressure of the hydraulic pump is applied;
A second pressure application port to which a control pressure opposed to the spring is applied;
A third pressure application port to which a control pressure opposite to the control pressure applied to the first and second pressure application ports is applied;
The relief pressure control unit
The first pressure application port is provided between the third pressure application port and the outlet port of the solenoid valve, and allows the flow of pressure oil from the first throttle and the third pressure application port to the outlet port side of the solenoid valve. A first control unit connected in parallel with one check valve;
The second pressure application port is provided between the second pressure application port and the outlet port of the solenoid valve, and allows a flow of pressure oil from the second throttle and the outlet port side of the solenoid valve to the second pressure application port. A hydraulic motor control device comprising: a second control unit connected in parallel with two check valves. In the hydraulic motor control device according to claim 1,
The solenoid valve controls the rotation direction control valve to the reverse rotation position, and the normal rotation control pressure for controlling the rotation direction control valve to the normal rotation position is different from the normal rotation control pressure as the switching control pressure. Output reverse control pressure,
The variable relief valve is
A first pressure application port that is opposed to a spring that biases the valve body and to which a pump pressure of the hydraulic pump is applied;
A second pressure application port to which a control pressure opposed to the spring is applied;
A third pressure application port to which a control pressure opposite to the control pressure applied to the first and second pressure application ports is applied;
The relief pressure control unit
The third pressure application port is provided between the third pressure application port and the outlet port of the solenoid valve, and the pressure of the third pressure application port is higher than the pressure of the outlet port of the solenoid valve. A first switching position that communicates with the outlet port of the solenoid valve, and the outlet of the solenoid valve via a throttle when the pressure of the outlet port of the solenoid valve is higher than the pressure of the third pressure application port A first switching valve having a second switching position that communicates a port with the third pressure application port;
Provided between the second pressure application port and the outlet port of the electromagnetic valve, and when the pressure of the second pressure application port is higher than the pressure of the outlet port of the electromagnetic valve, the electromagnetic A third switching position for communicating the outlet port of the valve with the second pressure application port; and the outlet of the solenoid valve when the pressure of the outlet port of the solenoid valve is higher than the pressure of the second pressure application port. A hydraulic motor control device comprising: a second switching valve having a port and a fourth switching position communicating with the second pressure application port. In the hydraulic motor control device according to claim 1,
The solenoid valve controls the rotation direction control valve to the reverse rotation position, and the normal rotation control pressure for controlling the rotation direction control valve to the normal rotation position is different from the normal rotation control pressure as the switching control pressure. Output reverse control pressure,
The variable relief valve is
A first pressure application port that is opposed to a spring that biases the valve body and to which a pump pressure of the hydraulic pump is applied;
A second pressure application port to which a control pressure opposed to the spring is applied;
A third pressure application port to which a control pressure opposite to the control pressure applied to the first and second pressure application ports is applied;
The relief pressure control unit
When the pressure of the second and third pressure application ports is higher than the pressure of the outlet port of the solenoid valve, the outlet port of the solenoid valve is communicated with the third pressure application port, and the outlet port is A first switching position communicating with the second pressure application port via a restriction;
When the pressure of the outlet port of the solenoid valve is higher than the pressure of the second and third pressure application ports, the outlet port of the solenoid valve is communicated with the second pressure application port, and the outlet port is A hydraulic motor control device comprising: a third switching valve having a second switching position communicating with the third pressure application port via a throttle. In the hydraulic motor control device according to claim 3,
When the rotational direction control valve is in the normal rotation position, the set pressure of the variable relief valve is set to the normal pressure set relief pressure,
When the rotational direction control valve is in the reverse rotation position, the set pressure of the variable relief valve is set to the reverse relief pressure setting,
The initial relief setting pressure value at the time of switching from reverse rotation to forward rotation is the relief setting pressure at the time of reverse rotation, and the initial relief setting pressure value at the time of switching from normal rotation to reverse rotation is the relief setting pressure at the time of forward rotation. There is a hydraulic motor control device.

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