JP4553680B2 - Travel drive fluid circuit - Google Patents

Description

    The present invention relates to a traveling drive fluid circuit capable of preventing theft of a vehicle such as a construction machine.

    In a vehicle such as a construction machine represented by a hydraulic excavator, the engine is started by inserting the key into the key switch and then rotating the key. Since the same key is used, there is a problem that the vehicle is often stolen.

For this reason, conventionally, in order to prevent theft as described above, for example, the one described in Patent Document 1 below has been proposed.
JP 2004-58720 A

  This means that the password input means, the password storage means, the password entered from the input means and the password stored in the storage means are compared, and when both password numbers match. And a comparator for enabling the start of the engine starter by operating the key switch, and preventing the start of the engine starter by operating the key switch when both passwords do not match.

    However, in such a conventional device, after the driver leaves the vehicle with the engine and the fluid pump stopped, the thief opens the vehicle engine cover and connects the electrical wiring of the engine starter. When directly connected, there is a problem that the vehicle cannot be prevented from traveling.

  An object of the present invention is to provide a fluid circuit for driving that can prevent a vehicle such as a construction machine from traveling even if an engine and a fluid pump are illegally operated by direct connection of electric wiring.

The first object is to connect a switching valve connected to a fluid pump and a tank, a fluid motor that drives a vehicle, and the switching valve, and supply the fluid to the fluid motor by switching the switching valve. A pair of main passages to be discharged, a counter balance valve that is interposed in the middle of the pair of main passages and restricts the fluid flowing through the high-pressure side main passage when the fluid motor performs pumping, and the high-pressure fluid through the brake passage When the high pressure fluid selected from the high pressure side main passage is supplied, the traveling drive fluid is provided with a negative brake that releases the braking force on the fluid motor. In the circuit, while connecting the pair of main passages, while providing a connection passage provided with a prevention switching valve that switches between the open position and the closed position in the middle, When stopping the operation of the body pump, a pilot path to switch to the open position by applying the open signal to the anti-switching valve provided by preventing the switching valve in the open position, the high pressure fluid to the other of the main passage from one of the main passage It can be achieved by the fluid circuit for driving driving that prevents the internal pressure of the main passage from rising by flowing out ,

Second, a switching valve connected to the fluid pump and the tank, a fluid motor that drives the vehicle, and the switching valve are connected, and a pair of main passages that supply and discharge fluid to the fluid motor by switching the switching valve And a counter balance valve that is interposed in the middle of the pair of main passages and restricts the fluid flowing through the high-pressure side main passage when the fluid motor performs a pump action, and when high-pressure fluid is not supplied through the brake passage In the travel drive fluid circuit, the brake passage includes a negative brake that applies a braking force to the fluid motor and releases a braking force to the fluid motor when a high-pressure fluid selected from the high-pressure side main passage is supplied. A preventive switching valve that switches between the open position and the closed position is installed in the middle of the operation, and when the fluid pump is stopped, the preventive switching valve is closed. The imparted provided a pilot path to switch to the closed position, the anti-switching valve in the closed position, that the pressure in the main passage is not supplied to the negative brake continues to impart a braking force to the hydraulic motor by negative brake Can be achieved by the fluid circuit for driving driving as described above ,

Third, a switching valve connected to the fluid pump and the tank, a fluid motor that drives the vehicle, and the switching valve are connected, and a pair of main passages that supply and discharge fluid to the fluid motor by switching the switching valve And a counter balance valve that is interposed in the middle of the pair of main passages and restricts fluid flowing through the high-pressure side main passage when the fluid motor performs a pump action, and when high-pressure fluid is not supplied through the brake passage In the travel drive fluid circuit comprising a negative brake that applies a braking force to the fluid motor and releases a braking force to the fluid motor when a high-pressure fluid selected from the high-pressure side main passage is supplied. A preventive switching valve that switches between an open position and a closed position is provided in the middle of a pair of pilot passages that guide high-pressure fluid from the main passage to the spool of the valve. Rutotomoni When stopping the operation of the fluid pump, preventing the switching valve to be applied close signal is provided to pilot path to switch to the closed position, the anti-switching valve in the closed position, high pressure fluid in the main passage of the counterbalance valve This can be achieved by the travel drive fluid circuit that keeps the counterbalance valve in the neutral position by preventing it from being guided to the spool .

    In the invention according to claim 1, while the pair of main passages are connected, a connection passage is provided in the middle of which is provided a prevention switching valve that switches between the open position and the closed position, while the operation of the fluid pump is performed. Since the pilot path for switching to the open position by giving an open signal to the prevention switching valve is provided, the fluid pump is illegally operated and the high pressure discharged from the fluid pump into one of the main passages. Even if the fluid is supplied, the high-pressure fluid flows out to the remaining main passage through the connection passage and the prevention switching valve in the open position, and then returned to the tank. As a result, the internal pressure of the one main passage does not increase so much and the operation of the fluid motor is easily and reliably prevented.

  In the invention according to claim 2, a preventive switching valve that switches between an open position and a closed position is interposed in the middle of the brake passage, and when the operation of the fluid pump is stopped, Since a pilot path is provided to switch to the closed position by giving a close signal, the fluid pump is illegally operated, and the high pressure fluid discharged from the fluid pump is supplied to one of the main passages to try to operate the fluid motor. However, since the prevention switching valve is in the closed position, the high pressure in the one main passage is not supplied to the negative brake, and as a result, the negative brake continues to apply the braking force to the fluid motor. . As a result, the operation of the fluid motor is easily and reliably prevented.

  Further, in the invention according to claim 3, a preventive switching valve that switches between an open position and a closed position is interposed in the middle of a pair of pilot passages that guide high-pressure fluid from the main passage to the spool of the counter balance valve. At the same time, when stopping the operation of the fluid pump, a pilot path is provided for switching to the closed position by giving a close signal to the prevention switching valve, so that the fluid pump is illegally operated and the fluid pump is installed in one of the main passages. Even when the high pressure fluid discharged from the high pressure fluid is supplied, the high pressure fluid in the one main passage is not guided to the spool of the counter balance valve through the pilot passage by the prevention switching valve in the closed position. The valve continues to maintain a neutral position, preventing fluid flow in the main passage. In this way, the operation of the fluid motor is simply and reliably prevented.

According to the fourth aspect of the present invention, since the pilot path and the control path are connected via the pilot control valve, the pilot path ahead of the pilot control valve becomes unnecessary, and as a result, the structure is simplified. As a result, the production cost can be reduced.
Furthermore, if constituted as in claim 5, a high-pressure fluid for switching the prevention switching valve can be taken out from the main passage, so that no special high-pressure source is required, and as a result, the structure becomes simple. Production costs can be reduced.

Embodiment 1 of the present invention will be described below with reference to the drawings.
In FIG. 1, reference numeral 11 denotes a fluid motor that applies a driving force for traveling to a vehicle (construction machine) such as a power shovel via a speed reducer 10, and the fluid motor 11 can switch the rotational speed to two stages. This is a variable capacity fluid motor. The fluid motor 11 has a swash plate 12 as a capacity variable member that can be tilted between two tilt positions of a high-speed rotation position and a low-speed rotation position. Then, the suction capacity of the fluid motor 11 is switched to a small value so as to rotate at a high speed. On the other hand, when the low speed rotation position is reached, the suction capacity of the fluid motor 11 is switched to a large value so as to rotate at a low speed.

  The fluid motor 11 and a switching valve 55 to be described later are connected by a pair of main passages 13 and 14, and in the middle of the main passages 13 and 14, high-pressure fluid is selected from the main passages 13 and 14 on the high-pressure side. A counter balance valve 15 that can be taken out is provided. The counter balance valve 15 has a spool 18 biased to return to the neutral position C by springs 16 and 17, and check valves 21 and 22 provided in bypass passages 19 and 20 for bypassing the spool 18, respectively. Have. Reference numeral 55 denotes a four-port three-position switching valve. The switching valve 55 is connected to a fluid pump 56 and a tank 57 connected to the engine 59 through a supply passage 60 and a discharge passage 61, respectively. Reference numeral 58 denotes a suction passage that connects the fluid pump 56 and the tank 57.

  The bypass passage 19 and the spool 18 are connected by a pilot passage 26 provided with a restriction 25 in the middle, and the bypass passage 20 and the spool 18 are connected by a pilot passage 28 provided with a restriction 27 in the middle. The pilot passages 26, 28 guide the fluid in the bypass passage 19 (main passage 13) or the bypass passage 20 (main passage 14) to the spool 18 of the counterbalance valve 15 and apply a pressing force against the springs 17, 16 to the spool 18. To grant.

  31 is a negative brake that applies a braking force when the rotation of the fluid motor 11 is stopped, and this negative brake 31 and the high pressure outlet of the counter balance valve 15 are connected by a brake passage 33 provided with a throttle 32 in the middle. . When the high pressure fluid selected and taken out from the high pressure side main passages 13 and 14 by the counter balance valve 15 is supplied to the negative brake 31 through the brake passage 33, the negative brake 31 applies a braking force to the fluid motor 11. To release. On the other hand, when the high-pressure fluid is not taken out by the counter balance valve 15, the fluid is discharged from the negative brake 31 to the drain path 34 by the biasing force of the spring 35 and the braking force is applied to the fluid motor 11.

  Reference numeral 38 denotes a tilt cylinder capable of applying a tilt force to the swash plate 12, and a tilt piston 40 as a piston is slidably accommodated in a cylinder case 39 of the tilt cylinder 38. The tilting piston 40 has a piston rod 41 whose tip is in contact with the swash plate 12. As a result, when high-pressure fluid is guided to the tilting piston 40 of the tilting cylinder 38, the tilting piston 40 40. The piston rod 41 protrudes to press the swash plate 12, and tilts the swash plate 12 from the low speed rotation position to the high speed rotation position. On the other hand, when the inside of the cylinder case 39 becomes tank pressure and no high pressure fluid is guided to the tilting piston 40, the swash plate 12 is moved from the high speed rotation position by the high pressure fluid flowing into the fluid motor 11 from the high pressure side main passages 13 and 14. The tilting piston 40 and the piston rod 41 of the tilting cylinder 38 are retracted while allowing the tilting.

  45 is a selection valve interposed in the middle of the connecting passage 46 connecting the main passage 13 and the main passage 14, and this selection valve 45 selects the high-pressure fluid from the main passage 13 or the main passage 14 on the high-pressure side. It can be taken out. 47 is a connecting passage for connecting the selection valve 45 and the tilting piston 40 of the tilting cylinder 38. This connection passage 47 guides the high-pressure fluid taken out by the selection valve 45 to the tilting piston 40, and The piston 40 is protruded. A control valve 50 is interposed in the connection passage 47, and the control valve 50 can be switched between a low speed position L and a high speed position K.

  Reference numeral 52 denotes a control passage for connecting the control valve 50 and a control means (high pressure fluid source) for supplying high pressure fluid as a switching signal (not shown). Through this control passage 52, the control valve 50 is supplied with a predetermined pressure from the high pressure fluid source. When the high pressure fluid is supplied, the control valve 50 is switched from the low speed position L to the high speed position K, so that the high pressure fluid selected from the high pressure side main passage 13 or 14 by the selection valve 45 becomes the tilting piston 40. Led to. On the other hand, when the high-pressure fluid is not supplied to the control passage 52, the control valve 50 is switched from the high speed position K to the low speed position L by the biasing force of the spring 51. As a result, the tilt cylinder 38 communicates with the drain path 34. Then, the inside of the cylinder case 39 becomes a tank pressure.

  In FIGS. 1, 2, and 3, reference numeral 65 denotes a prevention switching valve that can be switched between an open position and a closed position. This prevention switching valve 65 includes a cylindrical spool chamber 74 formed in the casing 73. Have. At the center in the axial direction of the spool chamber 74, the other end of the first connection passage 66a whose one end is connected to the main passage 13 and the other end of the second connection passage 66b whose one end is connected to the main passage 14 are shafts. Open away in the direction. A spool 75 is housed in the spool chamber 74 so as to be movable in the axial direction. The spool 75 includes a pair of lands 76 and 77 separated in the axial direction and an annular groove formed between the lands 76 and 77. 78. The first and second connection passages 66a and 66b described above constitute a connection passage 66 that connects the main passage 13 and the main passage 14 as a whole, and the prevention switching valve 65 is provided in the middle of the connection passage 66 as described above. It is intervened.

  Here, when the spool 75 moves to the other end in the axial direction as shown in FIG. 2 and the other end opening of the first connection passage 66a is closed by the land 76, the prevention switching valve 65 is switched to the closed position. The communication between the main passages 13 and 14 is blocked. On the other hand, as shown in FIG. 3, when the spool 75 moves to one end in the axial direction and the first and second connection passages 66a and 66b communicate with each other through the annular groove 78, the prevention switching valve 65 is switched to the open position. The main passages 13 and 14 communicate with each other through the connection passage 66. 79 is an operation hole formed in the casing 73 for inserting an operation means (for example, a specially shaped return rod) not shown in the prevention switching valve 65. The operation hole 79 is an axis of the spool chamber 74. Opened at one end in the direction.

  When the spool 75 is given a pressing force from the operating means (return rod) toward the other side in the axial direction as a closing signal and moves to the other end in the axial direction, the prevention switching valve 65 moves from the open position to the closed position. And switch. A pilot path 64 is connected to the prevention switching valve 65 and the switching valve 68. The pilot path 64 opens to the other axial end of the spool chamber 74. When a high-pressure fluid as an open signal is applied to the spool 75 of the prevention switching valve 65 through the pilot path 64, the spool 75 moves to one end in the axial direction, whereby the prevention switching valve 65 is closed. To the open position.

  Reference numeral 67 denotes an accumulator in which a high-pressure fluid serving as an open signal is stored. The accumulator 67 and the switching valve 68 are connected through a fluid passage 69. As a result, when the switching valve 68 is switched to the supply position, the high-pressure fluid from the accumulator 67 is supplied to the prevention switching valve 65 through the fluid passage 69 and the pilot path 64, while when the switching valve 68 is switched to the discharge position, The high-pressure fluid is discharged to the drain passage 34.

Next, the operation of the first embodiment of the present invention will be described.
Now, when the engine 59 is started and the fluid pump 56 is operated, the fluid is sucked into the fluid pump 56 from the tank 57 through the suction passage 58 and simultaneously discharged from the fluid pump 56 to the switching valve 55 through the supply passage 60. Is done. At this time, when the switching valve 55 is switched and either one, for example, high pressure fluid is supplied to the main passage 13, the high pressure fluid is guided to the spool 18 of the counterbalance valve 15 through the pilot passage 26. Is moved to the first position D while being compressed.

  At this time, the counter balance valve 15 selects and takes out the high-pressure fluid from the high-pressure side main passage 13, and supplies the negative brake 31 through the brake passage 33. Therefore, the negative brake 31 releases the braking force on the fluid motor 11, As a result, the fluid motor 11 starts rotating with the high-pressure fluid supplied through the main passage 13. The low-pressure fluid that has flowed out of the fluid motor 11 is discharged to the tank 57 through the main passage 14 and the discharge passage 61. As a result, the vehicle (construction machine) to which the driving force for traveling is applied from the granular motor 11 via the speed reducer 10 travels.

  As described above, when the high pressure fluid is supplied to the main passage 13, the high pressure fluid in the main passage 13 is selected and taken out by the selection valve 45. At this time, the control valve 50 is biased by the spring 51. When the low-pressure position L is reached, the extracted high-pressure fluid is not guided to the tilting piston 40, so that the swash plate 12 is in a low-speed rotation position, whereby the fluid motor 11 rotates at a low speed.

  Here, when the fluid motor 11 is rotated at a high speed, the high-pressure fluid is supplied from the high-pressure fluid source to the control valve 50 through the control passage 52, and the control valve 50 is switched from the low speed position L to the high speed position K. As a result, the high-pressure fluid selected by the selection valve 45 is guided to the tilting piston 40 through the connection passage 47 and tilts the swash plate 12 to the high-speed rotation position. As a result, the fluid motor 11 switches to a small suction capacity and rotates at a high speed.

  Next, when stopping the vehicle (construction machine), the switching valve 55 is switched to the neutral position, and both the main passages 13 and 14 are connected to the tank 57 to reduce the tank pressure. As a result, the rotation of the fluid motor 11 stops and the counter balance valve 15 returns to the neutral position C by the biasing force of the spring 17, while the negative brake 31 brakes against the fluid motor 11 by the biasing force of the spring 35. Giving power.

  Next, after the engine 59 is turned off and the fluid pump 56 is stopped, the driver leaves the vehicle. At this time, the switching valve 68 is switched to the supply position. As a result, high-pressure fluid is supplied from the accumulator 67 to the prevention switching valve 65 through the fluid passage 69 and the pilot passage 64, and the prevention switching valve 65 is switched to the open position. Here, once the prevention switching valve 65 is switched to the open position, the opening position may continue to be maintained, and then the switching valve 68 may be returned to the discharge position.

  When such a vehicle is stopped, if the theft is illegally connected directly to the electrical wiring to illegally start the engine 59, actuate the fluid pump 56, and switch the switching valve 55, either one, for example, the main passage 13 While the high-pressure fluid discharged from the fluid pump 56 is supplied, the counter balance valve 15 is switched to the first position D. At this time, the high-pressure fluid supplied to the main passage 13 is prevented from passing through the prevention switching valve 65 having a small passage resistance. Then, it flows out to the remaining main passage 14 through the connection passage 66 and then returned to the tank 57. As a result, the internal pressures of the one and the other main passages 13 and 14 do not rise so much, and the fluid motor 11 on which a large load is acting is simply and reliably prevented from rotating. Thus, even if the electrical wiring is directly connected and the engine 59 is operated illegally, the vehicle (construction machine) will not be stolen.

  In order to run the vehicle that has not been stolen again, a pressing force is applied to the spool 75 using the return rod, and the prevention switching valve 65 is switched from the open position to the closed position. At this time, the return rod has a special shape as described above, so that the prevention switching valve 65 is not easily returned to the closed position. Then, the engine 59 is started in the same manner as described above, and the high-pressure fluid is discharged from the fluid pump 56 to one of the main passages 13 and 14. At this time, since the prevention switching valve 65 is in the closed position, the high-pressure fluid does not flow out to the other main passages 13 and 14 through the connection passage 66, so that the fluid motor 11 operates as usual, The vehicle (construction machine) travels.

    FIG. 4 is a diagram showing Embodiment 2 of the present invention. In this embodiment, instead of omitting the prevention switching valve 65, the connection passage 66, and the pilot passage 64 in the first embodiment, a prevention switching valve 83 that switches between an open position and a closed position in the middle of the brake passage 33 is provided. And a pilot path 84 for connecting the prevention switching valve 83 and the switching valve 68 described above is provided.

  When the prevention switching valve 83 is in the open position, the high-pressure fluid taken out from the high-pressure side main passage 13 or 14 by the counter balance valve 15 is supplied to the negative brake 31 through the brake passage 33. The negative brake 31 releases the braking force applied to the fluid motor 11. On the other hand, when the switching valve 68 is switched to the supply position, the high-pressure fluid (closed signal) from the accumulator 67 is supplied to the prevention switching valve 83 through the fluid passage 69 and the pilot path 84, and the prevention switching valve 83 is switched to the closed position. .

  As a result, the fluid in the negative brake 31 flows out to the drain path 34 through the prevention switching valve 83, whereby the negative brake 31 applies a braking force to the fluid motor 11. At this time, even if the high-pressure fluid is taken out from the high-pressure side main passage 13 or 14 by the counter balance valve 15, the high-pressure fluid is shut off by the closed position prevention switching valve 83 interposed in the middle of the brake passage 33, and negative It is not supplied to the brake 31.

  Then, after the driver turns off the engine 59 and stops the operation of the fluid pump 56, when the driver leaves the vehicle, the switching valve 68 is switched to the supply position. As a result, the high-pressure fluid is supplied from the accumulator 67 to the prevention switching valve 83 through the pilot path 84, so that the prevention switching valve 83 is switched to the closed position.

  After that, if the thief connects the electrical wiring directly and illegally operates the engine 59 and switches the switching valve 55, for example, supplies the high-pressure fluid discharged from the fluid pump 56 to one main passage 13, Therefore, even if the fluid motor 11 is to be operated, the high-pressure fluid in the main passage 13 is not supplied to the negative brake 31 because the prevention switching valve 83 is switched to the closed position. As a result, the negative brake 31 continues to apply a braking force to the fluid motor 11, whereby the operation of the fluid motor 11 is easily and reliably prevented, and the vehicle (construction machine) is not stolen. In order to run the vehicle again, the prevention switching valve 83 may be switched from the closed position to the open position using the return rod. Other configurations and operations are the same as those in the first embodiment.

    FIG. 5 is a diagram showing Embodiment 3 of the present invention. In this embodiment, instead of omitting the prevention switching valve 65, the connection passage 66, and the pilot passage 64 in the first embodiment, a pair of high pressure fluids led from the high pressure side main passages 13, 14 to the spool 18 of the counter balance valve 15. In addition, a preventive switching valve 88 that switches between an open position and a closed position is provided in the middle of the pilot passages 26 and 28, and a pilot path 89 that connects the preventive switching valve 88 and the aforementioned switching valve 68 is provided. ing.

  When the prevention switching valve 88 is in the open position, for example, the spool 18 is moved by the high pressure fluid from the high pressure side pilot passage 26 and the counter balance valve 15 is switched to the first position D. The high-pressure fluid discharged from the pump 56 to the main passage 13 is guided to the fluid motor 11, while the low-pressure fluid flowing out from the fluid motor 11 is discharged to the tank 57 through the main passage 14. At this time, since the high-pressure fluid taken out by the counter balance valve 15 passes through the brake passage 33 and is supplied to the negative brake 31, the negative brake 31 releases the braking force applied to the fluid motor 11.

  On the other hand, when the switching valve 68 is switched to the supply position, the high-pressure fluid (closed signal) from the accumulator 67 is supplied to the prevention switching valve 88 through the fluid passage 69 and the pilot passage 89, and the prevention switching valve 88 is switched to the closed position. . As a result, the pilot passages 26 and 28 are interrupted in the middle, and no high-pressure fluid is guided to the spool 18 of the counterbalance valve 15, and the counterbalance valve 15 returns to the neutral position C by the urging force of the springs 16 and 17. Thus, even if high-pressure fluid is supplied from the fluid pump 56 to the main passage 13 or 14, the low-pressure return fluid from the fluid motor 11 flows out to the tank 57 by the counter balance valve 15 and the check valve 22 at the neutral position C. Is shut off, so that the fluid motor 11 does not rotate.

  At this time, since the high-pressure fluid is not supplied to the brake passage 33, the negative brake 31 continues to apply the braking force to the fluid motor 11, and more reliably stops the rotation of the fluid motor 11. In order to switch the prevention switching valve 88 from the closed position to the open position, a return rod may be used as described above. Then, after the driver turns off the engine 59 and stops the operation of the fluid pump 56, when the switching valve 68 is switched to the supply position when leaving the vehicle, the prevention switching valve 88 causes the high-pressure fluid from the accumulator 67 to flow. By being supplied to the prevention switching valve 88 through the pilot path 89, the position is switched to the closed position.

  After that, if the thief connects the electrical wiring directly and illegally operates the engine 59 and the fluid pump 56 and switches the switching valve 55, the high pressure fluid is supplied to one of the main passages, for example, the main passage 13, and the fluid motor Even when trying to rotate 11, the high-pressure fluid in the main passage 13 is not guided to the spool 18 of the counterbalance valve 15 through the pilot passage 26 by the prevention switching valve 88 that is switched to the closed position. The spool 18 of the counter balance valve 15 continues to maintain the neutral position C, and the flow of fluid in the main passages 13 and 14 is prevented. In addition, since the high-pressure fluid in the main passage 13 is not supplied to the negative brake 31, the negative brake 31 continues to apply a braking force to the fluid motor 11. For this reason, the operation of the fluid motor 11 is easily and reliably prevented, and the vehicle (construction machine) is not stolen.

  In the third embodiment, when the prevention switching valve 88 is in the closed position, the pilot passages 26 and 28 on the counter balance valve 15 side of the prevention switching valve 88 and the pilot passages on the main passages 13 and 14 side of the prevention switching valve 88 are provided. Although all the passages 26 and 28 were shut off, as shown in FIG. 6, the pilot passages 26 and 28 on the counterbalance valve 15 side from the prevention switching valve 88 and the main passages 13 and 14 side from the prevention switching valve 88. The pilot passages 26 and 28 may be communicated with each other by the prevention switching valve 88 in the closed position.

  In this way, the pressure in the pilot passages 26 and 28 on the counterbalance valve 15 side from the prevention switching valve 88 becomes equal, so that the counterbalance valve 15 reliably returns to the neutral position C and the prevention switching valve 88 The pilot passages 26 and 28 on the side of the main passages 13 and 14 with respect to 88 function as bypass passages that connect the main passages 13 and 14 as in the first embodiment. Other configurations and operations are the same as those in the first embodiment.

    FIG. 7 is a diagram showing Embodiment 4 of the present invention. In this embodiment, a three-position switching valve 95 is provided instead of omitting the accumulator 67, the switching valve 68 and the fluid passage 69 in the first embodiment. The switching valve 95 can be switched to a left position P, an intermediate position Q, and a right position R, and is connected to the tank 57 through a supply passage 98 and a discharge passage 99. In the middle of the supply passage 98, a fluid pump 94 connected to the engine 93 is interposed, and from the fluid pump 94, a predetermined pressure for switching the control valve 50 to the high speed position K, for example, a high pressure fluid of 5 MPa is discharged. .

   Reference numeral 100 denotes an accumulator that is higher than the predetermined pressure and stores a set pressure as an open signal, for example, a high-pressure fluid of 10 MPa, and the accumulator 100 and the switching valve 95 are connected through a fluid passage 97. 96 is a pilot control valve that switches from the discharge position (closed position) to the supply position (open position) when the high-pressure fluid of the set pressure is introduced. This pilot control valve 96 is connected to the control valve 50 and the switching valve 95. When the pressure of the guided high-pressure fluid becomes less than the set pressure, it is switched to the discharge position (closed position) by the urging force of the spring 101.

  When the switching valve 95 is switched to the left position P, the control passage 52 becomes the tank pressure, the control valve 50 is switched to the low speed position L, and the pilot control valve 96 is switched to the discharge position (closed position). When the switching valve 95 is switched to the intermediate position Q, the control passage 52 becomes a predetermined pressure and the control valve 50 is switched to the high speed position K, while the pilot control valve 96 is set to the discharge position (closed position). maintain. Further, when the switching valve 95 is switched to the right position R, the control passage 52 becomes the set pressure, the control valve 50 is switched to the high speed position K, and the pilot control valve 96 is switched to the supply position (open position). Change.

  As described above, when the pilot control valve 96 is switched to the supply position (open position), the high-pressure fluid having the set pressure introduced into the control passage 52 is connected to the pilot control valve 96 and the prevention switching valve 65. The prevention switching valve 65 is supplied through 64 to switch the prevention switching valve 65 to the open position. Since the pilot path 64 and the control path 52 are connected via the pilot control valve 96 in this way, a pilot path ahead of the pilot control valve 96 is not required. As a result, the structure is simplified and the production cost is reduced. can do. Other configurations and operations are the same as those in the first embodiment.

    FIG. 8 is a diagram showing Embodiment 5 of the present invention. In this embodiment, instead of omitting the switching valve 55, accumulator 67, switching valve 68 and fluid passage 69 in the first embodiment, a switching valve 105 is provided. The switching valve 105 can be switched between an open position and a closed position, and is connected to the pair of main passages 13 and 14 via connection passages 106 and 107, respectively. Reference numeral 108 denotes an accumulator in which a high-pressure fluid as an open signal is stored. The accumulator 108 and the switching valve 105 are connected through a fluid passage 109.

   110 and 111 are a pair of supply switching valves that can be switched between a supply position (open position) and a discharge position (closed position). These supply switch valves 110 and 111 are piloted in the main passages 13 and 14. They are connected via the passages 113 and 114, respectively, and can be switched to the discharge position (closed position) by the biasing force of the springs 115 and 116. The supply switching valve 110 is connected to the supply switching valve 111 through a supply passage 112 and to the prevention switching valve 65 through a pilot path 64. Reference numeral 117 denotes a four-port three-position switching valve provided in place of the switching valve 55. The switching valve 117 is connected to the fluid pump 56 and the tank 57 through a supply passage 60 and a discharge passage 61, respectively.

  When the switching valve 105 is in the closed position, one of the supply switching valves 110 or 111 to which the high-pressure fluid is supplied from the high-pressure side main passage 13 or 14 is switched to the supply position (open position), but the other Since the supply switching valve 110 or 111 maintains the discharge position (closed position), inflow of high-pressure fluid into the pilot path 64 is prevented. On the other hand, when the switching valve 117 is switched to the neutral position after the switching valve 117 is switched to the neutral position, the same pressure as an open signal, for example, a high-pressure fluid of 10 MPa or more is accumulated in both the pair of main passages 13 and 14 as an accumulator. While being supplied from 108, the high-pressure fluid is also supplied to the pilot passages 113 and 114, and both the supply switching valves 110 and 111 are switched to the supply position (open position).

  When the pair of supply switching valves 110 and 111 are both switched to the supply position (open position) in this way, the high-pressure fluid introduced into the pilot passage 114 passes through the supply passage 112 and the pilot passage 64 to the prevention switching valve 65. The preventive switching valve 65 is switched to the open position. At this time, the high pressure is confined in the main passages 13 and 14 and the pilot path 64, and the prevention switching valve 65 maintains the open position. In this way, the pilot path 64 and the main passages 13 and 14 are connected via the pair of supply switching valves 110 and 111, and the high-pressure fluid for switching the prevention switching valve 65 is taken out from the main passages 13 and 14. This eliminates the need for a special high-pressure source. As a result, the structure is simplified and the production cost can be reduced. Other configurations and operations are the same as those in the first embodiment.

    FIG. 9 is a diagram showing Embodiment 6 of the present invention. In this embodiment, instead of omitting the switching valve 105, the connection passages 106 and 107, the accumulator 108 and the fluid passage 109 in the fifth embodiment, the main passages 13 and 14 between the counterbalance valve 15 and the switching valve 117 are omitted. In addition, a switching valve 120 that switches between a supply / discharge position and a supply position is interposed, and the switching valve 120 and the tank 57 described above are connected, and a relief passage 121 in which a relief valve 122 is interposed is provided on the way. Provided. 123 is a selection valve interposed in the middle of the connecting passage 124 connecting the main passages 13 and 14 between the switching valve 117 and the switching valve 120. The selection valve 123 and the switching valve 120 are connected through the selection passage 125. It is connected.

  When the switching valve 120 is in the supply / discharge position, the high-pressure fluid selected and taken out from the main passages 13 and 14 by the selection valve 123 is not guided to the relief valve 122. On the other hand, the supply switching valve 110 or 111 supplied with the high-pressure fluid from the high-pressure side main passage 13 or 14 is switched to the supply position (open position), but the remaining supply switching valve 110 or 111 is the discharge position (closed position). ) Is maintained, the flow of high-pressure fluid into the pilot path 64 is prevented.

  When the switching valve 120 is switched to the supply position in this state, the high-pressure fluid selected by the selection valve 123 is guided to both the main passages 13 and 14 and the relief passage 121 through the selection passage 125. At this time, the main passage 13 14, the pressure in the relief passage 121 becomes the set pressure set by the relief valve 122. When the same pressure (set pressure) as an open signal, for example, a high-pressure fluid of 10 MPa or more is supplied from the operating fluid pump 56 to both the pair of main passages 13 and 14, the supply switching valve 110, Both 111 are switched to the supply position (open position).

  When the pair of supply switching valves 110 and 111 are both switched to the supply position (open position) in this way, the high-pressure fluid introduced into the pilot passage 114 passes through the supply passage 112 and the pilot passage 64 to the prevention switching valve 65. The preventive switching valve 65 is switched to the open position. Thereafter, when the switching valve 117 is switched to the neutral position and the engine 59 and the fluid pump 56 are stopped, the set pressure is confined in the main passages 13 and 14 and the pilot path 64, and the prevention switching valve 65 maintains the open position. .

  In this way, the pilot passage 64 and the main passages 13 and 14 are connected via the supply switching valves 110 and 111, and the high-pressure fluid for switching the prevention switching valve 65 is taken out from the main passages 13 and 14. This eliminates the need for a high-pressure source, and as a result, the structure is simplified and the production cost can be reduced. Other configurations and operations are the same as those in the fifth embodiment.

    In the above-described embodiment, the high-pressure fluid supplied from the accumulator 67 through the pilot paths 64, 84, 89 is used as the open signal for switching the prevention switching valves 65, 83, 88 to the open position. The preventive switching valve may be composed of an electromagnetic valve, and an electrical signal applied through the pilot path as an open signal may be used. Further, in the above-described embodiment, the return rod having a special shape is used as the operation means for returning the prevention switching valves 65, 83, and 88 to the closed position, but in this invention, the prevention switching valve is energized. A spring may be provided, and when the open signal is no longer applied to the prevention switching valve, the prevention switching valve may be automatically returned from the open position to the closed position by the spring.

  The present invention can be applied to a travel drive fluid circuit capable of preventing theft of a vehicle such as a construction machine.

It is a circuit diagram which shows Example 1 of this invention. It is front sectional drawing of the prevention switching valve vicinity. It is front sectional drawing similar to FIG. 2 explaining the action | operation of a prevention switching valve. It is a circuit diagram which shows Example 2 of this invention. It is a circuit diagram which shows Example 3 of this invention. It is a circuit diagram which shows the example of improvement of Example 3 of this invention. It is a circuit diagram which shows Example 4 of this invention. It is a circuit diagram which shows Example 5 of this invention. It is a circuit diagram which shows Example 6 of this invention.

Explanation of symbols

11… Fluid motor 12… Variable capacity member
13, 14 ... Main passage 15 ... Counterbalance valve
18… Spool 26, 28… Pilot passage
31 ... Negative brake 33 ... Brake passage
40 ... Piston 50 ... Control valve
52 ... Control passage 55, 117 ... Switch valve
56 ... Fluid pump 57 ... Tank
64, 84, 89 ... Pilot path 65, 83, 88 ... Prevention switching valve
66 ... Connection passage 96 ... Pilot control valve
110, 111 ... Supply switching valve

Claims (5)

A switching valve connected to a fluid pump and a tank; a fluid motor that drives a vehicle; and the switching valve; a pair of main passages that supply and discharge fluid to and from the fluid motor by switching the switching valve; A counter balance valve that restricts the fluid that flows through the high-pressure side main passage when the fluid motor performs a pump action when the fluid motor performs a pump action, and brakes the fluid motor when high-pressure fluid is not supplied through the brake passage. When the high-pressure fluid selected from the high-pressure side main passage is supplied, the pair of main passages are connected in a traveling drive fluid circuit having a negative brake that releases the braking force to the fluid motor. In addition, while providing a connection passage with a preventive switching valve that switches between the open position and the closed position in the middle, the operation of the fluid pump is stopped. When the pilot path to switch to the open position by applying the open signal to the anti-switching valve provided by preventing the switching valve in the open position, the internal pressure of the main passage from one of the main passage to flow out the high pressure fluid to the other of the main passage A fluid circuit for driving driving, characterized in that it is not raised . A switching valve connected to a fluid pump and a tank; a fluid motor that drives a vehicle; and the switching valve; a pair of main passages that supply and discharge fluid to and from the fluid motor by switching the switching valve; A counter balance valve that restricts the fluid that flows through the high-pressure side main passage when the fluid motor performs a pump action when the fluid motor performs a pump action, and brakes the fluid motor when high-pressure fluid is not supplied through the brake passage When a high-pressure fluid selected from the high-pressure side main passage is supplied, a traveling drive fluid circuit having a negative brake for releasing the braking force on the fluid motor is opened in the middle of the brake passage. A preventive switching valve that switches between the position and the closed position is installed, and when the operation of the fluid pump is stopped, a close signal is given to the preventive switching valve. Provided a pilot path to switch to the closed position Te, by preventing the switching valve in the closed position, the high pressure in the main passage Being not supplied to the negative brake, and so continue to impart a braking force to the hydraulic motor by negative brake A fluid circuit for driving driving characterized by the above. A switching valve connected to a fluid pump and a tank; a fluid motor that drives a vehicle; and the switching valve; a pair of main passages that supply and discharge fluid to and from the fluid motor by switching the switching valve; A counter balance valve that restricts the fluid that flows through the high-pressure side main passage when the fluid motor performs a pump action when the fluid motor performs a pump action, and brakes the fluid motor when high-pressure fluid is not supplied through the brake passage. When a high-pressure fluid selected from the high-pressure side main passage is supplied, a travel drive fluid circuit having a negative brake for releasing the braking force on the fluid motor is provided to the spool of the counter balance valve. When a preventive switching valve that switches between an open position and a closed position is installed in the middle of a pair of pilot passages that guide high-pressure fluid from the main passage , When stopping the operation of the fluid pump, provided with a pilot path to switch to the closed position by applying a close signal to prevent switching valve, by preventing the switching valve in the closed position, high pressure fluid in the main passage of the counterbalance valve spool The travel drive fluid circuit is characterized in that the counter balance valve is continuously held in the neutral position by preventing it from being guided to the vehicle.     The fluid motor is composed of a variable displacement fluid motor capable of switching the rotational speed in two steps by changing the position of the variable displacement member by moving the piston, and a high pressure fluid of a predetermined pressure is supplied through the control passage. A control valve for switching to guide the high-pressure fluid selected from the high-pressure side main passage to the piston, and a high-pressure fluid having a set pressure higher than a predetermined pressure between the control passage and the pilot passage. The travel drive fluid circuit according to any one of claims 1 to 3, further comprising a pilot control valve that is in an open position when is supplied to the control passage.     When a high-pressure fluid is supplied to both of the pair of main passages, a pair of supply switching valves are provided which are both opened by the high pressure in the main passages and supply the high pressure in the main passage to the pilot path. Item 4. The travel drive fluid circuit according to any one of Items 1 to 3.

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