JP2019105288A - Fluid pressure control device and working vehicle including fluid pressure control device - Google Patents

Abstract

To improve volumetric efficiency while securing a neutral region of a discharge mechanism.SOLUTION: A fluid pressure control device 100 includes: a communication passage 5 for connecting a connection flow passage 3 to a connection flow passage 4; and an on-off valve 6 provided to the communication passage 5. The on-off valve 6 closes the valve thereof to shut down the communication passage 5 when a flow rate of hydraulic oil discharged from a two-way pump 1 is equal to or higher than a constant value, and opens the valve thereof to open through the communication passage 5 when the flow rate of hydraulic oil discharged from the two-way pump 1 is less than the constant value.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fluid pressure control device and a work vehicle provided with the fluid pressure control device.

  Patent Document 1 discloses a hydraulic pump (discharge device) having two ports, a hydraulic motor for driving a drive wheel, and a hydraulic fluid line for fluidly connecting both the hydraulic pump and the hydraulic motor so that they form a closed circuit. , And HST (Hydro Static Transmission) is described.

  In the HST described in Patent Document 1, in order to secure a neutral region of the hydraulic pump, a flow control valve is provided in a flow passage that communicates the hydraulic fluid line with the pump-side charge fluid passage.

JP 2007-198419 A

  In the HST described in Patent Document 1, the hydraulic oil line and the pump side charge oil path are always in communication by the flow control valve. In this configuration, although the neutral region of the hydraulic pump (discharge device) can be secured, a part of the high-pressure hydraulic oil supplied from the hydraulic pump to the hydraulic motor during normal traveling is a low pressure through the flow control valve from the hydraulic oil line. Since the fluid flows out to the pump side charge oil passage of the above, the volumetric efficiency of the hydraulic pump is reduced.

  The present invention has been made in view of the above problems, and aims to improve volumetric efficiency while securing a neutral region of a discharge device.

  According to a first aspect of the present invention, there is provided a discharge device for discharging a working fluid from one of a first port and a second port, a fluid pressure motor driven by the working fluid discharged from the discharge device, and a first port of the discharge device. A first connection channel connecting one port of the fluid pressure motor, a second connection channel connecting the second port of the discharge device and the other port of the fluid pressure motor, a first connection channel and a first connection channel (2) A bypass flow path connecting the connection flow path and an on-off valve provided in the bypass flow path. The on-off valve is closed when the flow rate of the working fluid discharged from the discharge device is equal to or more than a predetermined value. It is characterized in that the bypass flow path is shut off, and when the flow rate of the working fluid discharged from the discharge device is less than a predetermined value, the flow path is opened to open the bypass flow path.

  In the first aspect of the invention, when the flow rate of the working fluid discharged from the discharge device is equal to or more than a predetermined value, the bypass flow path is shut off by the on-off valve, so the working fluid discharged from the discharge device is totally fluid pressure motor To improve the volumetric efficiency of the discharge device. Further, when the flow rate of the working fluid discharged from the discharge device is equal to or less than a predetermined value, the bypass flow path is opened, so that the working fluid discharged from the discharge device is bypassed without being supplied to the fluid pressure motor. Since the fluid is returned to the discharge device through the flow path, the neutral region of the discharge device can be secured.

  In a second aspect of the invention, the discharge device is a variable displacement bidirectional pump having an adjustment member for adjusting the discharge capacity, and the on-off valve operates a valve body for blocking or opening the bypass flow passage. The operating member is characterized in that the operating member is connected to the adjusting member.

  In the second aspect of the invention, the on-off valve is opened and closed in accordance with the operation of the adjusting member, so that the operation of the on-off valve can be stabilized.

  According to a third aspect of the present invention, a first orifice provided in the first connection flow path, a second orifice provided in the second connection flow path, and a biasing member biasing the on-off valve in the valve opening direction. Further, the on-off valve has a pressure on the discharge device side of the first orifice and a pressure on the discharge device side of the second orifice acting in the valve closing direction, and the pressure on the fluid pressure motor side of the first orifice and the second The pressure on the fluid pressure motor side of the orifice acts in the valve opening direction.

  A fourth invention supplies a working fluid to a first orifice provided in a first connection flow channel, a second orifice provided in a second connection flow channel, and the first connection flow channel and the second connection flow channel. Charge pump, a charge flow path for guiding the working fluid discharged from the charge pump to the first connection flow path and the second connection flow path, and a working fluid provided in the charge flow path from the charge pump to the first connection flow path A second check valve provided in the charge flow path and permitting only the flow of the working fluid from the charge pump to the second connection flow path, and the first connection flow path And the first communication passage connected to the charge pump side of the charge flow passage relative to the first check valve, and the second connection passage connected to the charge pump side relative to the second check valve And the second communication passage And the first on-off valve provided in the first communication passage, the biasing member urging the first on-off valve in the valve opening direction, and the second on-off valve provided in the second communication passage And a biasing member for biasing the second on-off valve in the valve opening direction, and pressure on the discharge device side of the first orifice acts on the first on-off valve in the valve closing direction, and the first orifice The pressure on the fluid pressure motor side acts on the valve opening direction, and the pressure on the discharge device side of the second orifice acts on the second on-off valve in the valve closing direction, and the pressure on the fluid pressure motor side of the second orifice Acts in the valve opening direction, and the bypass flow path connects the first connection flow path and the second connection flow path through the first communication path and the charge flow path, or the second communication path and the charge flow path. It features.

  In the third and fourth inventions, even when the discharge device and the on-off valve are separated and can not be connected, the volumetric efficiency can be improved while securing the neutral region of the discharge device.

  A fifth invention is characterized in that the work vehicle includes the fluid pressure control device according to any one of the first invention to the fourth invention.

  According to the present invention, the volumetric efficiency can be improved while securing the neutral region of the discharge device.

FIG. 1 is a hydraulic circuit diagram of a fluid pressure control device according to a first embodiment of the present invention. It is a figure which shows the operation range of the control lever which concerns on 1st Embodiment of this invention. It is a hydraulic circuit figure showing the modification of the fluid pressure control device concerning a 1st embodiment of the present invention. FIG. 7 is a hydraulic circuit diagram of a fluid pressure control device according to a second embodiment of the present invention. It is a hydraulic circuit figure of the fluid pressure control device concerning a 3rd embodiment of the present invention. It is a hydraulic circuit figure showing the modification of the fluid pressure control device concerning a 3rd embodiment of the present invention. It is a hydraulic circuit diagram showing another modification of the fluid pressure control device concerning a 3rd embodiment of the present invention. It is a hydraulic circuit figure of the fluid pressure control device concerning a 4th embodiment of the present invention.

First Embodiment
Hereinafter, a fluid pressure control device 100 according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a hydraulic circuit diagram showing a fluid pressure control device 100. As shown in FIG.

  The fluid pressure control device 100 is mounted on a vehicle body of a working vehicle driven by fluid pressure, such as a lawn mower, a farming machine, a wheel loader, or the like. In the fluid pressure control device 100, hydraulic oil is used as the working fluid, but other fluids such as working water may be used as the working fluid.

  As shown in FIG. 1, the fluid pressure control device 100 includes a bidirectional pump 1 as a discharge device for discharging hydraulic fluid, and a hydraulic motor as a fluid pressure motor driven by hydraulic fluid discharged from the bidirectional pump 1. 2, a connection flow path 3 as a first connection flow path connecting the one port 1 a as the first port of the bidirectional pump 1 and the one port 2 a of the hydraulic motor 2, and the second of the bidirectional pump 1 Connection flow path 4 as a second connection flow path connecting the other port 1 b as a port and the other port 2 b of the hydraulic motor 2, and bypass flow path connecting the connection flow path 3 and the connection flow path 4 The communication passage 5 and the on-off valve 6 provided in the communication passage 5 are provided.

  The bidirectional pump 1 is a swash plate type axial piston pump driven by the power of the engine E. The bidirectional pump 1 can adjust the displacement of the hydraulic fluid by adjusting the tilt angle of the swash plate 1c, and control the direction in which the hydraulic fluid is discharged (port 1a or port 1b). It is a variable displacement pump that can In the bidirectional pump 1, the tilt angle of the swash plate 1c is adjusted by operating the operation lever 7 as an adjustment member connected to a trunnion shaft (not shown) that pivotally supports the swash plate 1c.

  The hydraulic motor 2 is an internal gear motor, and is used as a traveling hydraulic motor for driving wheels. The hydraulic motor 2 is rotationally driven in response to the supply of hydraulic fluid discharged from the bidirectional pump 1. The hydraulic motor 2 is switched to forward rotation or reverse rotation depending on the flow direction of the hydraulic fluid discharged from the bidirectional pump 1. Specifically, the hydraulic fluid discharged from the port 1a of the bidirectional pump 1 is guided to the hydraulic motor 2a of the hydraulic motor 2 through the connection flow path 3, whereby the hydraulic motor 2 rotates forward and the work vehicle advances. On the other hand, the hydraulic oil discharged from the port 1b of the bidirectional pump 1 is guided to the hydraulic motor 2b through the connection flow path 4, whereby the hydraulic motor 2 rotates in the reverse direction, and the work vehicle moves backward.

  The hydraulic motor 2 has an internal leak. The hydraulic oil that has leaked inside is returned to the tank T through the drain passage 2c. The hydraulic motor 2 is not limited to the internal gear motor having a fixed capacity, but may be a swash plate type axial piston motor or a swash plate type axial piston motor having a variable capacity.

  The on-off valve 6 opens the communication passage 5 at the communication position A, and blocks the communication passage 5 at the blocking position B and the blocking position C. The on-off valve 6 has an operating lever 6 a as an operating member for operating a valve for blocking or opening the communication passage 5. The control lever 6 a of the on-off valve 6 is mechanically coupled to the control lever 7 of the bidirectional pump 1 by a mechanical link mechanism 8. Thus, the operating lever 6 a of the on-off valve 6 is operated in accordance with the operation of the operating lever 7.

  FIG. 2 is a view showing an operating range of the operating lever 7. When the operating lever 7 is operated within the predetermined operating range P from the neutral position and the neutral position, the operating lever 6a is also operated within the predetermined operating range, so the on-off valve 6 is held at the communication position A. When the control lever 7 is operated to one side beyond the predetermined operation range P, the open / close valve 6 is switched to the blocking position B because the operation lever 6a is also operated beyond the predetermined operation range. When the control lever 7 is operated to the other side beyond the predetermined operation range P, the open / close valve 6 is switched to the blocking position C because the operation lever 6a is also operated beyond the predetermined operation range.

  The fluid pressure control device 100 includes a charge pump 9 driven by the engine E and provided coaxially with the bidirectional pump 1 and a charge flow path for guiding the hydraulic oil discharged from the charge pump 9 to the connection flow path 3 and the connection flow path 4 And a relief valve 11 provided in a flow path connecting the charge flow path 10 and the tank T.

  The charge pump 9 discharges the hydraulic oil sucked from the tank T to the charge flow path 10. The hydraulic oil discharged from the charge pump 9 is charged from the charge flow path 10 through the check valve 12 into the connection flow paths 3 and 4 when the hydraulic oil in the connection flow paths 3 and 4 is insufficient. The relief valve 11 opens and discharges the hydraulic oil to the tank T when the pressure in the charge flow passage 10 rises above a predetermined value.

  The operation of the fluid pressure control device 100 configured as described above will be described. First, the case of advancing the work vehicle from the stopped state will be described.

  When the crew operates the control lever 7 gradually toward one side, the swash plate 1c of the bidirectional pump 1 gradually inclines from the neutral position to one side, and the tilting angle of the swash plate 1c from the port 1a of the bidirectional pump 1 The hydraulic fluid of the flow rate according to is discharged to the connection flow path 3. At this time, since the control lever 6 a of the on-off valve 6 is connected to the control lever 7 by the link mechanism 8, the control lever 6 a operates in conjunction with the operation of the control lever 7. When the operating lever 7 is operated slightly, specifically, when operating within the operating range Q of FIG. 2, the operating lever 6a of the on-off valve 6 is also within a certain operating range, and the on-off valve 6 is in the communication position A Maintained. Therefore, the whole amount of the hydraulic oil discharged from the bidirectional pump 1 to the connection flow path 3 is returned to the connection flow path 4 on the suction side through the communication path 5. Therefore, the hydraulic motor 2 is not driven. In this way, the situation where the hydraulic motor 2 does not operate even though the bidirectional pump 1 discharges the hydraulic fluid, and the operating range Q of the operating lever 7 in such a situation, in the following "neutral state" Or it is called "neutral area".

  Further operating the operating lever 7 from this state, specifically, when the operating lever 7 is operated out of the operating range Q (operating range R) within the operating range P, the swash plate 1c of the bidirectional pump 1 is further inclined; The flow rate of the hydraulic oil discharged from the bidirectional pump 1 is increased. In this state, the operating lever 6a of the on-off valve 6 is also in a certain operating range, and the on-off valve 6 is maintained at the communication position A. However, in this state, since the flow rate of the hydraulic fluid discharged from the bidirectional pump 1 becomes large, the entire amount of the hydraulic fluid discharged from the bidirectional pump 1 can not be returned from the communication passage 5 to the connection passage 4 . As a result, the hydraulic oil that can not be returned to the connection flow path 4 is supplied from the port 2 a to the hydraulic motor 2, and the hydraulic motor 2 is started. Thus, the work vehicle starts to move forward. As described above, the condition where the hydraulic motor 2 operates by part of the hydraulic fluid discharged by the bidirectional pump 1, and the operation range R of the control lever 7 in such a condition are hereinafter referred to as "slow speed state" or "slow speed area" "

  When the control lever 7 is further operated beyond the operating range P from this state, the swash plate 1c of the bidirectional pump 1 is further inclined. At the same time, the operating lever 6a of the on-off valve 6 is also operated beyond a certain operating range, so the on-off valve 6 is switched to the blocking position B. For this reason, the communication passage 5 is shut off, and the hydraulic oil discharged from the bidirectional pump 1 to the connection passage 3 is supplied to the hydraulic motor 2 as a whole. In the region beyond the operation range P, the hydraulic motor 2 is supplied with a flow rate corresponding to the amount of operation of the operation lever 7. Therefore, the work vehicle advances at a speed corresponding to the amount of operation of the control lever 7. As described above, the condition in which the hydraulic motor 2 is operated by the total amount of hydraulic fluid discharged by the bidirectional pump 1, and the operation range of the operation lever 7 in such a condition are hereinafter referred to as "normal traveling state" or "normal traveling area "

  As described above, in the fluid pressure control device 100, when the operation lever 7 is operated within the predetermined operation range Q, the communication passage 5 is maintained in the open state, and the hydraulic oil discharged from the bidirectional pump 1 is It is not supplied to the hydraulic motor 2. Thereby, the neutral region of the bidirectional pump 1 can be secured. In addition, since the hydraulic oil is not returned to the connection flow path 4 through the on-off valve 6 in the normal traveling state, the volumetric efficiency of the bidirectional pump 1 can be improved.

  Further, in the fluid pressure control device 100, a low speed region is provided between the neutral region and the normal travel region. If the low speed region is not provided, the hydraulic motor 2 may start with a shock since the neutral state is suddenly switched to the normal running state. Specifically, in the neutral state, the whole amount of the hydraulic oil discharged from the bidirectional pump 1 to the connection flow path 3 is returned to the connection flow path 4 on the suction side through the communication path 5 and the hydraulic motor 2 Has stopped. From this state, when the vehicle is switched to the normal traveling state without passing through the slow speed state, the hydraulic oil returned from the communication passage 5 to the connection flow passage 4 is suddenly supplied to the hydraulic motor 2. For example, even when the operating lever 7 is operated slowly, when the hydraulic motor 2 is thus rapidly supplied with hydraulic fluid, the hydraulic motor 2 operates slowly even though the operating lever 7 is operated slowly. There is a risk of starting with a shock.

  Therefore, in the fluid pressure control device 100, when the slow speed region is provided as described above, and it is not possible to return the entire amount of the discharged hydraulic oil to the connection flow path 4 through the communication path 5, a part of the hydraulic oil Is configured to start the hydraulic motor 2. As a result, the hydraulic motor 2 is started with a small flow rate, so it is possible to suppress the shock at the start.

  Next, the case of stopping the work vehicle from the traveling state will be described.

  When the operation amount of the control lever 7 is reduced from the normal traveling state, the inclination of the swash plate 1c of the bidirectional pump 1 becomes smaller, and the flow rate of the hydraulic fluid discharged from the bidirectional pump 1 also becomes smaller. Therefore, the rotational speed of the hydraulic motor 2 is reduced.

  From this state, when the operation amount of the operation lever 7 is reduced to within the above-described slow speed region (operation range R), the on-off valve 6 is switched from the blocking position B to the communication position A, and the communication passage 5 is opened. As a result, part of the hydraulic oil discharged from the bidirectional pump 1 is returned to the connection flow path 4 through the communication path 5, and the hydraulic motor 2 is further decelerated.

  From this state, when the operation amount of the operation lever 7 is further reduced to the neutral region (operation range Q), the entire amount of hydraulic oil discharged from the bidirectional pump 1 is returned to the connection flow passage 4 through the communication passage 5 Therefore, the hydraulic motor 2 is further decelerated. Furthermore, when the control lever 7 is returned to the neutral position, the tilt angle of the swash plate 1c becomes zero, and the hydraulic fluid is not discharged from the bidirectional pump 1.

  When the control lever 7 is returned to the neutral region or the neutral position, the hydraulic vehicle 2 is forcibly rotated because the work vehicle continues to move forward by inertia. Thus, the hydraulic motor 2 sucks in hydraulic fluid from the port 2a and discharges it from the port 2b. The hydraulic fluid thus discharged from the port 2 b is returned to the connection flow path 3 through the communication path 5 and the on-off valve 6. At this time, the hydraulic motor 2 is gradually decelerated and stopped because the braking force acts on the hydraulic motor 2 due to the pressure loss generated when the hydraulic oil passes through the on-off valve 6 and the pressure loss generated by the hydraulic motor 2. As described above, the fluid pressure control device 100 is configured such that the on-off valve 6 opens the communication passage 5 when the control lever 7 is returned to the neutral position, so the hydraulic motor 2 is accompanied by a shock. Without it, it can be stopped smoothly.

  In the fluid pressure control device 100, when the operation amount of the operation lever 7 is a predetermined value or more (outside of the operation range P), the on-off valve 6 closes the valve to shut off the communication passage 5, and the operation amount of the operation lever 7 When it is less than a predetermined value (within the operation range P), the communication passage 5 is opened by opening the valve. The operation amount of the operation lever 7 corresponds to the flow rate of the hydraulic fluid discharged by the bidirectional pump 1. That is, in the fluid pressure control device 100, the on-off valve 6 closes the communication passage 5 when the flow rate of the hydraulic fluid discharged from the bidirectional pump 1 is equal to or more than a predetermined value, and shuts off the communication passage 5. When the flow rate of the hydraulic oil to be fed is less than a predetermined value, the communication passage 5 is opened to open.

  Further, the fluid pressure control device 100 has an effect that the traveling can be stabilized when the work vehicle travels on the downhill in the low speed region. Below, this effect is demonstrated concretely.

  When the work vehicle travels at a low speed, the operation lever 7 is operated in the above-described low speed region (within the operation range R). At this time, hydraulic fluid corresponding to the operation amount of the control lever 7 is discharged from the bidirectional pump 1 to the connection flow path 3. In this state, as described above, since the on-off valve 6 is located at the communication position A, a portion of the hydraulic oil discharged from the bidirectional pump 1 is returned to the connection flow path 4 through the communication path 5. Further, the remaining hydraulic oil is supplied to the hydraulic motor 2 and the hydraulic motor 2 is driven.

  When the work vehicle travels downhill, the work vehicle accelerates by its own weight. As a result, the hydraulic motor 2 is forced to rotate, so the hydraulic motor 2 functions as a hydraulic pump that sucks in hydraulic fluid from the port 2a and discharges it to the port 2b.

  Here, for comparison, a configuration in which the communication passage 5 and the on-off valve 6 are not provided will be described. When the communication passage 5 and the on-off valve 6 are not provided, the hydraulic oil discharged from the port 2 b of the hydraulic motor 2 flows toward the port 1 b of the bidirectional pump 1. However, when the hydraulic motor 2 functions as a hydraulic pump as described above, the hydraulic oil exceeding the suction amount in the bidirectional pump 1 is supplied into the connection flow path 4, so the pressure in the connection flow path 4 Increases above the pressure in the connection channel 3. At this time, in the hydraulic motor 2 configured by the internal gear motor, a leak occurs between the inner and outer gears, and the hydraulic oil flows back from the connection flow path 4 to the connection flow path 3 There are times when When such a leak occurs, the pressure in the connection channel 4 temporarily decreases. Thereafter, the pressure of the connection flow path 4 is increased again by the hydraulic oil supplied from the hydraulic motor 2. By repeating the rise and fall of such pressure, hunting occurs in the hydraulic motor 2 and the operation of the work vehicle may be jerky.

  In the fluid pressure control device 100, since the on-off valve 6 is configured to open the communication passage 5 in the low speed region, when the pressure of the connection flow passage 4 is thus increased, the connection flow is performed through the communication passage 5 The pressure can be released to the road 3. Therefore, when the work vehicle travels at a very low speed on the downward slope, it is possible to suppress the occurrence of hunting, and the traveling becomes stable.

  When moving the work vehicle backward, the operation lever 7 is operated in the reverse direction to that at the time of forward movement. As a result, the swash plate 1c of the bidirectional pump 1 is inclined in the opposite direction to that at the time of forward movement, and the hydraulic oil is discharged from the port 1b of the bidirectional pump 1. Further, as in the forward movement, when the operation amount of the operation lever 7 exceeds the operation range P, the on-off valve 6 switches from the communication position A to the blocking position C. Since the on-off valve 6 functions in the same manner as at the time of forward movement, the description thereof will be omitted.

  According to the first embodiment described above, the following effects can be obtained.

  When the control lever 7 is operated in the normal travel area, that is, when the flow rate of the hydraulic fluid discharged from the bidirectional pump 1 is equal to or more than a predetermined value, the communication passage 5 is shut off by the on-off valve 6. As a result, since the entire amount of hydraulic oil discharged from the bidirectional pump 1 is supplied to the hydraulic motor 2, the volumetric efficiency of the bidirectional pump 1 is improved. Further, when the control lever 7 is operated in the neutral range (operation range Q), that is, when the flow rate of the hydraulic fluid discharged from the bidirectional pump 1 is less than a predetermined value, the on-off valve 6 is in the communication position A And the communication passage 5 is opened. Thereby, the hydraulic fluid discharged from the bidirectional pump 1 is not supplied to the hydraulic motor 2, and the connection channel 3 or connection channel 4 on the high pressure side through the communication channel 5 to the connection channel 3 or connection on the low pressure side Since it returns to the flow path 4, the neutral region of the bidirectional pump 1 can be secured. Therefore, according to the fluid pressure control device 100, volumetric efficiency can be improved while securing the neutral region of the bidirectional pump 1.

  In the fluid pressure control device 100, the on-off valve 6 is configured to open the communication passage 5 in the low speed region, so the hydraulic motor 2 functions as a hydraulic pump when the work vehicle travels at a low speed at a downward slope. Thus, even if the pressure in the connection channel 4 is increased, the pressure can be released to the connection channel 3 through the communication channel 5. Therefore, it is possible to suppress the occurrence of hunting in the hydraulic motor 2 when the work vehicle travels at a very low speed on the downward slope, so that the travel of the work vehicle can be stabilized.

  Further, in the fluid pressure control device 100, the control lever 6 a of the on-off valve 6 is mechanically connected to the control lever 7 of the bidirectional pump 1. As a result, the on-off valve 6 is opened and closed in accordance with the operation of the control lever 7, so that the operation of the on-off valve 6 can be stabilized.

  The on-off valve 6 may be configured as the on-off valve 16 shown in FIG. 3. This modification will be described below.

  In the modification shown in FIG. 3, the on-off valve 16 is provided with a blocking position D for blocking the communication passage 5 when the control lever 7 is in the neutral position. Thereby, when the control lever 7 is in the neutral position, that is, when the hydraulic fluid is not discharged from the bidirectional pump 1, the hydraulic motor 2 can be locked by the hydraulic circuit. As a result, when the control lever 7 is in the neutral position, the hydraulic motor 2 can be prevented from traveling by itself.

  As described above, by providing the on-off valve 16 instead of the on-off valve 6, the hydraulic motor 2 can be locked when the control lever 7 is in the neutral position, so that a mechanical lock mechanism can be eliminated.

Second Embodiment
A fluid pressure control device 200 according to a second embodiment of the present invention will be described with reference to FIG. Hereinafter, differences from the above-described first embodiment will be mainly described, and the same components as those of the fluid pressure control device 100 of the first embodiment will be assigned the same reference numerals and descriptions thereof will be omitted.

  In the first embodiment, the on-off valve 6 opens and closes in response to the movement of the control lever 7 of the bidirectional pump 1, while in the second embodiment, the pressure at which the on-off valve 60 is led from the connection flow paths 3 and 4 It differs in that it opens and closes according to the difference of. The details will be described below.

  The fluid pressure control device 200 includes an opening / closing valve 60 provided in the communication passage 5 and an orifice 31 as a first orifice provided on the bidirectional pump 1 side with respect to a junction of the communication passage 5 of the connection flow passage 3. And an orifice 41 as a second orifice provided closer to the bidirectional pump 1 than a junction of the connection flow path 4 with the communication path 5.

  The on-off valve 60 opens the communication passage 5 at the communication position E and blocks the communication passage 5 at the blocking position F. The on-off valve 60 includes a spring 61 that biases the on-off valve 60 toward the blocking position F in the valve closing direction. In the on-off valve 60, the pressure on the bidirectional pump 1 side of the orifice 31 and the pressure on the bidirectional pump 1 side of the orifice 41 act in the valve closing direction through the flow paths 32 and 42, respectively. The pressure on the side and the pressure on the hydraulic motor 2 side of the orifice 41 act in the valve opening direction through the flow paths 33 and 43, respectively.

  The operation of the fluid pressure control device 200 configured as described above will be described. First, the case of advancing the work vehicle from the stopped state will be described.

  When the crew operates the control lever 7 gradually toward one side, the swash plate 1c of the bidirectional pump 1 gradually inclines from the neutral position to one side, and the tilting angle of the swash plate 1c from the port 1a of the bidirectional pump 1 The hydraulic fluid of the flow rate according to is discharged to the connection flow path 3. At this time, the pressure on the upstream side (the bidirectional pump 1 side of the orifice 31) in the connection flow path 3 acts in the valve closing direction of the on-off valve 60 through the flow path 32, and the downstream side of the orifice 31 (hydraulic motor 2 side) Pressure acts in the opening direction of the on-off valve 60 through the flow path 33. In this state, since the flow rate of the hydraulic fluid discharged from the bidirectional pump 1 is small, the biasing force in the valve closing direction (direction for switching the on-off valve 60 to the blocking position F) by the differential pressure before and after the orifice 31 Since the biasing force of the spring 61 in the valve opening direction (the direction of switching the on-off valve 60 to the communication position E) is large, the on-off valve 60 is held at the communication position E. As a result, the high-pressure hydraulic oil discharged from the bidirectional pump 1 to the connection flow path 3 is returned to the connection flow path 4 which is the suction side through the communication path 5. Therefore, the hydraulic motor 2 is not driven.

  In this state, the operating lever 7 is further operated. Specifically, when the operating lever 7 is operated to the operating range R, the swash plate 1 c of the bidirectional pump 1 is further inclined, and the hydraulic fluid discharged from the bidirectional pump 1 Flow rate increases. In this state, the spring 61 opens more than the biasing force in the valve closing direction (direction in which the on-off valve 60 is switched to the blocking position F) by the differential pressure before and after the orifice 31 (hereinafter referred to as “front-rear differential pressure”). Since the biasing force in the valve direction (the direction in which the on-off valve 60 is switched to the communication position E) is large, the on-off valve 60 is held at the communication position E. However, in this state, since the flow rate of the hydraulic fluid discharged from the bidirectional pump 1 becomes large, the entire amount of the hydraulic fluid discharged from the bidirectional pump 1 can not be returned from the communication passage 5 to the connection passage 4 . As a result, the hydraulic oil that can not be returned to the connection flow path 4 is supplied from the port 2 a to the hydraulic motor 2, and the hydraulic motor 2 is started. Thus, the work vehicle starts to move forward.

  When the control lever 7 is further operated beyond the operating range P from this state, the swash plate 1c of the bidirectional pump 1 is further inclined. As a result, the flow rate of the hydraulic fluid discharged from the bidirectional pump 1 further increases, so the differential pressure across the orifice 31 becomes larger, and the valve closing direction (the on-off valve 60 is set to the blocking position F) The biasing force in the switching direction is larger than the biasing force in the valve opening direction (the direction in which the on-off valve 60 is switched to the communication position E) by the spring 61. Therefore, the on-off valve 60 is switched to the blocking position F. For this reason, the communication passage 5 is shut off, and the hydraulic oil discharged from the bidirectional pump 1 to the connection passage 3 is supplied to the hydraulic motor 2 as a whole. In the region beyond the operation range P, the hydraulic motor 2 is supplied with a flow rate corresponding to the operation amount of the operation lever 7, and the work vehicle advances at a speed according to the operation amount of the operation lever 7.

  The hydraulic oil supplied to the hydraulic motor 2 is discharged from the port 2 b to the connection flow path 4. As described above, the connection flow path 4 is provided with the orifice 41, and the pressure on the bidirectional pump 1 side of the orifice 41 acts in the closing direction of the on-off valve 60 through the flow path 42. The pressure on the motor 2 side acts in the opening direction of the on-off valve 60 through the flow path 43.

  As described above, there is an internal leak in the hydraulic motor 2, and this internal leak is returned to the tank T through the drain passage 2c. Therefore, the flow rate of the hydraulic oil discharged to the connection flow path 4 is smaller than the flow rate of the hydraulic oil supplied to the connection flow path 3. Therefore, the differential pressure generated in the orifice 41 provided in the connection flow channel 4 is smaller than the differential pressure generated in the orifice 31 provided in the connection flow channel 3. That is, in the on-off valve 60, the biasing force in the valve closing direction by the differential pressure of the orifice 31 is the biasing force in the valve opening direction by the differential pressure of the orifice 41 and the biasing force in the valve opening direction by the spring 61. When it becomes larger than the sum, it is switched to the blocking position F.

  The differential pressure across the orifices 31 and 41 depends on the flow rate of the hydraulic fluid discharged from the bidirectional pump 1. Therefore, the on-off valve 60 closes when the flow rate of the hydraulic fluid discharged from the bidirectional pump 1 is equal to or greater than a predetermined value to shut off the communication passage 5, and the flow rate of the hydraulic fluid discharged from the bidirectional pump 1 is When it is less than a fixed value, the valve is opened to open the communication passage 5.

  Next, the case of stopping the work vehicle from the traveling state will be described.

  When the operation amount of the control lever 7 is reduced from the normal traveling state, the inclination of the swash plate 1c of the bidirectional pump 1 becomes smaller, and the flow rate of the hydraulic fluid discharged from the bidirectional pump 1 also becomes smaller. Therefore, the rotational speed of the hydraulic motor 2 is reduced.

  From this state, if the operation amount of the operation lever 7 is reduced to within the slow speed region (operation range R), the pressure difference across the orifice 31 decreases, so the on-off valve 60 is switched from the blocking position F to the communication position E. The passage 5 opens. As a result, part of the hydraulic oil discharged from the bidirectional pump 1 is returned to the connection flow path 4 through the communication path 5, and the hydraulic motor 2 is further decelerated.

  From this state, when the operation amount of the operation lever 7 is further reduced to the neutral region (operation range Q), the entire amount of hydraulic oil discharged from the bidirectional pump 1 is returned to the connection flow passage 4 through the communication passage 5 Therefore, the hydraulic motor 2 is further decelerated. Furthermore, when the control lever 7 is returned to the neutral position, the tilt angle of the swash plate 1c becomes zero, and the hydraulic fluid is not discharged from the bidirectional pump 1.

  When the control lever 7 is returned to the neutral region or the neutral position, the hydraulic vehicle 2 is forcibly rotated because the work vehicle continues to move forward by inertia. Thus, the hydraulic motor 2 sucks in hydraulic fluid from the port 2a and discharges it from the port 2b. The hydraulic oil thus discharged from the port 2 b is returned to the connection flow path 3 through the communication path 5 and the on-off valve 60. At this time, the braking force acts on the hydraulic motor 2 by the pressure loss generated when the hydraulic oil passes through the on-off valve 60 and the pressure loss generated by the hydraulic motor 2, so the hydraulic motor 2 is gradually decelerated and stopped. As described above, since the fluid pressure control device 200 is configured to open the communication passage 5 when the control lever 7 is returned to the neutral position, the hydraulic motor 2 is accompanied by a shock. Without it, it can be stopped smoothly.

  Also in the fluid pressure control device 200, when the work vehicle travels on the downward slope in the low speed region, the travel can be stabilized. Below, this effect is demonstrated concretely.

  When the work vehicle travels in the low speed region, the operation lever 7 is operated in the low speed region (within the operation range R). At this time, hydraulic fluid corresponding to the operation amount of the control lever 7 is discharged from the bidirectional pump 1 to the connection flow path 3. In this state, as described above, since the on-off valve 60 is located at the communication position E, a portion of the hydraulic oil discharged from the bidirectional pump 1 is returned to the connection channel 4 through the communication channel 5. Further, the hydraulic motor 2 is driven by the remaining hydraulic oil.

  When the work vehicle travels downhill, the work vehicle accelerates by its own weight. As a result, the hydraulic motor 2 is forced to rotate, so the hydraulic motor 2 functions as a hydraulic pump that sucks in hydraulic fluid from the port 2a and discharges it to the port 2b.

  Also in the fluid pressure control device 200, the on-off valve 60 is configured to open the communication passage 5 in the low speed region, so when the pressure in the connection flow passage 4 is increased in this manner, connection is made through the communication passage 5 The pressure can be released to the flow path 3. Therefore, when the work vehicle travels at a very low speed on the downhill, the traveling becomes stable.

  When moving the work vehicle backward, the control lever 7 is operated in the reverse direction to that at the time of forward movement. As a result, the swash plate 1c of the bidirectional pump 1 is inclined in the opposite direction to that in forward movement, and the hydraulic fluid is discharged from the port 1b of the bidirectional pump 1. At this time, the orifice 41 functions in the same manner as the orifice 31 at the time of forward movement, and switches the on-off valve 60, so the description thereof will be omitted.

  According to the above second embodiment, in addition to the effects of the first embodiment, the following effects can be obtained.

  In the fluid pressure control device 200, since there is no need to mechanically connect the control lever 7 and the on-off valve 60, the distance between the bidirectional pump 1 and the on-off valve 60 is large and can not be mechanically connected. However, volumetric efficiency can be improved while securing the neutral region of the bidirectional pump 1.

Third Embodiment
A fluid pressure control device 300 according to a third embodiment of the present invention will be described with reference to FIG. Hereinafter, differences from the above-described second embodiment will be mainly described, and the same components as those of the fluid pressure control device 200 of the second embodiment will be assigned the same reference numerals and descriptions thereof will be omitted.

  In the second embodiment, the communication passage 5 directly communicates the connection flow passage 3 and the connection flow passage 4, whereas in the third embodiment, the connection flow passage 3 and the connection flow passage 4 are connected through the charge flow passage 10. The difference is that they are in communication. Further, in the second embodiment, one on-off valve 60 is provided in the communication passage 5, whereas in the third embodiment, the first and second on-off valves 161 and 162 are provided in the communication passage 150. It is different. The details will be described below.

  The fluid pressure control device 300 is provided in the charge flow channel 10, and allows only the flow of hydraulic oil from the charge pump 9 to the connection flow channel 3, and cuts off the flow from the connection flow channel 3 to the charge pump 9 A check valve 12a as a valve, and a second flow passage provided in the charge flow passage 10 to allow only the flow of hydraulic oil from the charge pump 9 to the connection flow passage 4 and blocking the flow from the connection flow passage 4 to the charge pump 9 A check valve 12b as a check valve, a first communication passage 151 connected to the connection flow passage 3 and further connected to the charge pump 9 than the check valve 12a of the charge flow passage 10; And the second communication passage 152 connected to the charge pump 9 side closer to the charge pump 9 than the check valve 12 b of the charge passage 10 and the first communication passage 151 provided in the first communication passage 151 or Comprising a first on-off valve 161 through a second on-off valve 162 to block or open the second communication path 152 provided in the second communication passage 152, the.

  The first communication passage 151 and the second communication passage 152 respectively merge with the charge flow passage 10 at junctions 153 and 154 on the upstream side of the check valves 12 a and 12 b of the charge flow passage 10. In the fluid pressure control device 300, the charge flow path 10 reaching the connection flow path 4 from the first communication path 151 and the junction 153 through the check valve 12b, and the connection flow from the second communication path 152 and the junction 154 through the check valve 12a. The charge flow paths 10 reaching the path 3 correspond to the communication paths 150 as bypass flow paths, respectively.

  The first on-off valve 161 has a communication position G for opening the first communication passage 151 and a blocking position H for blocking the first communication passage 151. The second on-off valve 162 has a communication position I for opening the second communication passage 152 and a blocking position J for blocking the second communication passage 152.

  The first on-off valve 161 includes a spring 161 a that biases the first on-off valve 161 toward the blocking position H in the valve closing direction. In the first on-off valve 161, the pressure on the bidirectional pump 1 side of the orifice 31 acts in the valve closing direction through the flow path 32, and the pressure on the hydraulic motor 2 side of the orifice 31 acts in the valve opening direction through the flow path 33 Do.

  The second on-off valve 162 includes a spring 162 a that urges the second on-off valve 162 toward the blocking position J in the valve closing direction. In the second on-off valve 162, the pressure on the bidirectional pump 1 side of the orifice 41 acts in the valve closing direction through the flow path 42, and the pressure on the hydraulic motor 2 side of the orifice 41 acts in the valve opening direction through the flow path 43 Do.

  The operation of the fluid pressure control device 300 configured as described above will be described. First, the case of advancing the work vehicle from the stopped state will be described.

  When the crew operates the control lever 7 gradually toward one side, the swash plate 1c of the bidirectional pump 1 gradually inclines from the neutral position to one side, and the tilting angle of the swash plate 1c from the port 1a of the bidirectional pump 1 The hydraulic fluid of the flow rate according to is discharged to the connection flow path 3. At this time, the pressure on the upstream side (the bidirectional pump 1 side of the orifice 31) in the connection flow path 3 acts in the valve closing direction of the first on-off valve 161 through the flow path 32, and the downstream side of the orifice 31 (hydraulic motor 2 The pressure on the side) acts in the valve opening direction of the first on-off valve 161 through the flow path 33. In this state, since the flow rate of the hydraulic fluid discharged from the bidirectional pump 1 is small, the biasing force in the valve closing direction (direction to switch the first on-off valve 161 to the blocking position H) by the differential pressure before and after the orifice 31 Since the biasing force in the valve opening direction (direction in which the first on-off valve 161 is switched to the communication position G) by the spring 161 a is larger than that, the first on-off valve 161 is held at the communication position G. As a result, the high-pressure hydraulic oil discharged from the bidirectional pump 1 to the connection flow path 3 flows into the charge flow path 10 from the first communication path 151 through the junction 153, and passes through the check valve 12b. It is returned to the connection channel 4 which is the low pressure side. Therefore, the hydraulic motor 2 is not driven.

  From this state, the operating lever 7 is further operated. Specifically, when the operating lever 7 is operated to the operating range R, the swash plate 1c of the bidirectional pump 1 is further inclined, and the flow rate of hydraulic fluid discharged from the bidirectional pump 1 Becomes larger. In this state, the valve opening direction by the spring 161a (the first on-off valve 161 in the communication position is more than the biasing force in the valve closing direction (the direction to switch the first on-off valve 161 to the blocking position H) The first on-off valve 161 is held at the communication position G because the biasing force in the direction of switching to G) is large. However, in this state, the flow rate of the hydraulic fluid discharged from the bidirectional pump 1 increases, so that the entire amount of hydraulic fluid discharged from the bidirectional pump 1 can be returned from the first communication passage 151 to the connection passage 4. become unable. As a result, the hydraulic oil that can not be returned to the connection flow path 4 is supplied from the port 2 a to the hydraulic motor 2, and the hydraulic motor 2 is started. Thus, the work vehicle starts to move forward.

  When the control lever 7 is further operated beyond the operating range P from this state, the swash plate 1c of the bidirectional pump 1 is further inclined. As a result, the flow rate of the hydraulic fluid discharged from the bidirectional pump 1 further increases, so the differential pressure across the orifice 31 becomes larger, and the valve closing direction by the differential pressure across the orifice 31 (the first on-off valve 161 shut off position The biasing force in the direction of switching to H) is larger than the biasing force in the valve opening direction (direction of switching the first on-off valve 161 to the communication position G) by the spring 161a. Therefore, the first on-off valve 161 is switched to the blocking position H. Therefore, the first communication passage 151 is shut off, and the hydraulic oil discharged from the bidirectional pump 1 to the connection passage 3 is supplied to the hydraulic motor 2 as a whole. In the region beyond the operation range P, the hydraulic motor 2 is supplied with a flow rate corresponding to the operation amount of the operation lever 7, and the work vehicle advances at a speed according to the operation amount of the operation lever 7.

  The hydraulic oil supplied to the hydraulic motor 2 is discharged from the port 2 b to the connection flow path 4. As described above, the connection flow path 4 is provided with the orifice 41, and the pressure on the bidirectional pump 1 side of the orifice 41 acts in the valve closing direction of the second on-off valve 162 through the flow path 42. The pressure on the hydraulic motor 2 side acts on the second on-off valve 162 through the flow path 43 in the valve opening direction. At this time, the pressure in the flow path 43 is higher than the pressure in the flow path 42, and the first on-off valve 161 opens in the valve-opening direction (the second on-off valve 162 is switched to the communication position I by the spring 162a. And the second on-off valve 162 is held at the communication position I.

  In the fluid pressure control device 300, even if the second on-off valve 162 is at either the communication position I or the blocking position J when the work vehicle advances, the operation that flows into the charge flow path 10 from within the connection flow path 3 The oil can flow to the connection channel 4 through the check valve 12b. Even if the hydraulic oil on the hydraulic motor 2 side from the orifice 41 of the connection flow passage 4 flows into the charge flow passage 10 through the second communication passage 152, it can be returned to the connection flow passage 4 through the check valve 12b.

  The differential pressure across the orifice 31 depends on the flow rate of the hydraulic fluid discharged from the bidirectional pump 1. Therefore, the first on-off valve 161 is closed when the flow rate of the hydraulic fluid discharged from the bidirectional pump 1 is equal to or more than a predetermined value to shut off the first communication passage 151 and the operation discharged from the bidirectional pump 1 When the flow rate of oil is less than a predetermined value, the valve opens to open the first communication passage 151.

  When the pressure in the connection flow passage 4 is higher than the charge flow passage 10, more specifically, when the pressure in the connection flow passage 4 is higher than the set pressure of the relief valve 11, the relief valve The valve 11 is opened, and the hydraulic oil is discharged from the relief valve 11 to the tank T.

  Next, the case of stopping the work vehicle from the traveling state will be described.

  When the operation amount of the control lever 7 is reduced from the normal traveling state, the inclination of the swash plate 1c of the bidirectional pump 1 becomes smaller, and the flow rate of the hydraulic fluid discharged from the bidirectional pump 1 also becomes smaller. Therefore, the rotational speed of the hydraulic motor 2 is reduced.

  From this state, if the operation amount of the operation lever 7 is reduced to within the slow speed region (operation range R), the first on-off valve 161 is switched from the blocking position H to the communication position G because the differential pressure across the orifice 31 decreases. , And the first communication passage 151 is opened. As a result, part of the hydraulic fluid discharged from the bidirectional pump 1 is returned to the connection flow path 4 through the first communication path 151 and the charge flow path 10, and the hydraulic motor 2 is further decelerated.

  From this state, when the operation amount of the operation lever 7 is further reduced to the neutral region (operation range Q), the entire amount of hydraulic oil discharged from the bidirectional pump 1 passes through the first communication passage 151 and the charge passage 10 As it is returned to the connection channel 4, the hydraulic motor 2 is further decelerated. Furthermore, when the control lever 7 is returned to the neutral position, the tilt angle of the swash plate 1c becomes zero, and the hydraulic fluid is not discharged from the bidirectional pump 1.

  When the control lever 7 is returned to the neutral region or the neutral position, the hydraulic vehicle 2 is forcibly rotated because the work vehicle continues to move forward by inertia. Thus, the hydraulic motor 2 sucks in hydraulic fluid from the port 2a and discharges it from the port 2b. The hydraulic oil thus discharged from the port 2 b is returned to the connection flow path 3 through the second communication path 152, the second on-off valve 162, the charge flow path 10, and the check valve 12 a. At this time, the braking force acts on the hydraulic motor 2 by the pressure loss generated when the hydraulic oil passes through the second on-off valve 162 and the pressure loss generated by the hydraulic motor 2, so the hydraulic motor 2 is gradually decelerated and stopped Do. Thus, the fluid pressure control device 300 is configured such that the on-off valve 60 opens the communication passage 150 (the second communication passage 152 and the charge passage 10) when the control lever 7 is returned to the neutral position. Thus, the hydraulic motor 2 can be smoothly stopped without shock.

  Also in the fluid pressure control device 300, when the work vehicle travels on the downhill in the low speed region, the traveling can be stabilized. Below, this effect is demonstrated concretely.

  When the work vehicle travels in the low speed region, the operation lever 7 is operated in the above-described low speed region (within the operation range R). At this time, hydraulic fluid corresponding to the operation amount of the control lever 7 is discharged from the bidirectional pump 1 to the connection flow path 3. As described above, since the first on-off valve 161 is located at the communication position G, the hydraulic oil discharged from the bidirectional pump 1 is partially through the first communication passage 151, the charge flow passage 10, and the check valve 12b. It is returned to the connection channel 4 and the hydraulic motor 2 is driven by the remaining hydraulic oil. Thereby, the work vehicle moves forward at a slight speed.

  When the work vehicle travels downhill, the work vehicle accelerates by its own weight. As a result, the hydraulic motor 2 is forced to rotate, so the hydraulic motor 2 functions as a hydraulic pump that sucks in hydraulic fluid from the port 2a and discharges it to the port 2b.

  At this time, the pressure on the bidirectional pump 1 side of the orifice 41 acts in the closing direction of the second on-off valve 162 through the flow path 42 and the pressure on the hydraulic motor 2 side of the orifice 41 flows through the flow path 43 to the second on-off valve It acts in the valve opening direction of 162. The pressure in the flow path 43 is higher than the pressure in the flow path 42, and the second on-off valve 162 is opened in the valve opening direction (a direction to switch the second on-off valve 162 to the communication position I) by the spring 162a. The second on-off valve 162 is held at the communication position I because it is biased. Therefore, high-pressure hydraulic fluid discharged from the hydraulic motor 2 can release pressure from the second communication passage 152 to the connection passage 3 through the charge passage 10 and the check valve 12 a. Therefore, when the work vehicle travels at a very low speed on the downhill, the traveling becomes stable.

  When the work vehicle is moved backward, when the work vehicle is moved backward, the operation lever 7 is operated in the reverse direction to that at the time of forward movement. As a result, the swash plate 1c of the bidirectional pump 1 is inclined in the opposite direction to that in forward movement, and the hydraulic fluid is discharged from the port 1b of the bidirectional pump 1. At this time, the functions of the first on-off valve 161 and the second on-off valve 162 are merely interchanged, so the description will be omitted.

  According to the above third embodiment, the same effect as the second embodiment can be obtained.

  As in the modification shown in FIG. 6, only the first on-off valve 161 may be provided without providing the second on-off valve 162, and the communication passage 150 may be shut off only when moving forward. In this case, volumetric efficiency can be improved while securing a neutral region in the forward direction of the bidirectional pump 1.

  Further, as in the modification shown in FIG. 7, instead of the first on-off valve 161 of FIG. 6, an on-off valve 206 switched by the operating lever 206a connected by the operating lever 7 and the link mechanism 8 is provided. It is also good. Also in this case, volumetric efficiency can be improved while securing a neutral region in the forward direction of the bidirectional pump 1.

Fourth Embodiment
A fluid pressure control device 400 according to a third embodiment of the present invention will be described with reference to FIG. Hereinafter, differences from the above-described first embodiment will be mainly described, and the same components as those of the fluid pressure control device 100 of the first embodiment will be assigned the same reference numerals and descriptions thereof will be omitted.

  In the first embodiment, the bidirectional pump 1 functions as a discharge device, whereas in the fourth embodiment, the discharge device 401 is configured by the unidirectional pump 402 and the switching valve 403. The details will be described below.

  As shown in FIG. 8, the fluid pressure control device 400 includes a unidirectional pump 402 and a switching valve 403 that switches the direction of hydraulic fluid discharged from the pump 402. One port 2 a of the hydraulic motor 2 is connected to the port 403 a of the switching valve 403, and the other port 2 b is connected to the port 403 b of the switching valve 403. In the present embodiment, the port 403 a functions as a first port of the discharge device 401, and the port 403 b functions as a second port of the discharge device 401.

  The switching valve 403 is switched by the operation lever 403c. The operating lever 403 c is mechanically connected to the operating lever 6 a of the on-off valve 6 by a mechanical link mechanism 8. Thereby, the operating lever 6a of the on-off valve 6 is operated in accordance with the operation of the operating lever 403c. Similar to the control lever 7 in the first embodiment, the control lever 403c is provided with a region corresponding to the neutral region (control range Q) and the low speed region (control range R).

  In the fluid pressure control device 400 configured as described above, by operating the operation lever 403c of the switching valve 403, the discharge device 401 is switched to discharge hydraulic fluid from either the port 403a or the port 403b. . The other components operate in the same manner as the fluid pressure control device 100, and thus the description of the operation of the fluid pressure control device 400 is omitted.

  According to the above fourth embodiment, the same effect as that of the first embodiment can be obtained.

  The configuration, operation, and effects of the embodiment of the present invention configured as described above will be collectively described.

  The fluid pressure control devices 100, 200, 300, and 400 each include a discharge device (bidirectional pump 1, discharge device 401) that discharges working fluid (hydraulic oil) from either the first port or the second port, and a discharge device A fluid pressure motor (hydraulic motor 2) driven by hydraulic fluid (hydraulic fluid) discharged from the bidirectional pump 1, discharge device 401), and a first port of the discharge device (bidirectional pump 1, discharge device 401) The first connection flow path (connection flow path 3) for connecting the port 1a, the port 403a) and one port 2a of the fluid pressure motor (hydraulic motor 2), and the discharge device (bidirectional pump 1, discharge device 401) A second connection channel (connection channel 4) connecting the second port (port 1b, port 403b) and the other port 2b of the fluid pressure motor (hydraulic motor 2), and a first connection channel (connection channel) 3) and the second contact A bypass flow path (communication path 5, communication path 150) connecting the flow path (connection flow path 4) and an on-off valve (on-off valve 6, opening / closing valve provided in the bypass flow path (communication path 5, communication path 150) 16, an on-off valve 60, a first on-off valve 161, a second on-off valve 162, an on-off valve 206), the on-off valve (on-off valve 6, on-off valve 16, on-off valve 60, first on-off valve 161, second The on-off valve 162 and the on-off valve 206 are closed when the flow rate of the hydraulic fluid (hydraulic oil) discharged from the discharge device (bidirectional pump 1, discharge device 401) is equal to or more than a predetermined value. When the flow rate of the working fluid (hydraulic fluid) discharged from the discharge device (bidirectional pump 1, discharge device 401) is less than a predetermined value, the passage 5 and the communication passage 150 are shut off to open the bypass flow passage The communication passage 5 and the communication passage 150) are opened.

  According to this configuration, when the flow rate of the working fluid (hydraulic fluid) discharged from the discharge device (bidirectional pump 1, discharge device 401) is equal to or greater than a predetermined value, the bypass flow passage (communication passage 5, communication passage 150) Is shut off by the on-off valve (on-off valve 6, on-off valve 16, on-off valve 60, first on-off valve 161, second on-off valve 162, on-off valve 206). The entire amount of the working fluid (working fluid) discharged from the above is supplied to the fluid pressure motor (hydraulic motor 2), and the volumetric efficiency of the discharge device (bidirectional pump 1, discharge device 401) is improved. In addition, when the flow rate of the working fluid (hydraulic oil) discharged from the discharge device (bidirectional pump 1, discharge device 401) is equal to or less than a predetermined value, the bypass flow passage (communication passage 5, communication passage 150) is opened. Therefore, the working fluid (hydraulic fluid) discharged from the discharge device (bidirectional pump 1, discharge device 401) is not supplied to the fluid pressure motor (hydraulic motor 2), and the bypass flow passage (communication passage 5; continuous gear) Since it is returned to the discharge device (bidirectional pump 1, discharge device 401) through the passage 150), the neutral region of the discharge device (bidirectional pump 1, discharge device 401) can be secured. Therefore, volumetric efficiency can be improved while securing the neutral region of the discharge device (bidirectional pump 1, discharge device 401).

  Further, in the fluid pressure control device 100, the bidirectional pump 1 is a variable displacement bidirectional pump having an adjusting member (a control lever 7) for adjusting the displacement, and the on-off valves 6, 16 are bypassed. It has an operation member (operation lever 6a) for operating the valve body for blocking or opening the flow path (communication passage 5), and the operation member (operation lever 6a) is connected to the adjustment member (operation lever 7) It is characterized by

  According to this configuration, since the on-off valves 6 and 16 are opened and closed in accordance with the operation of the control lever 7, the operation of the on-off valve 6 can be stabilized.

  Further, the fluid pressure control device 200 includes a first orifice (orifice 31) provided in the first connection channel (connection channel 3) and a second orifice provided in the second connection channel (connection channel 4). The orifice (orifice 41) and a biasing member (spring 61) for biasing the on-off valve 60 in the valve opening direction are further provided, and the on-off valve 60 has a discharge device for the first orifice (orifice 31) (bidirectional The pressure on the pump 1) side and the pressure on the discharge device (bidirectional pump 1) side of the second orifice (orifice 41) act in the valve closing direction, and the fluid pressure motor (hydraulic motor) of the first orifice (orifice 31) 2) The pressure on the side and the pressure on the fluid pressure motor (hydraulic motor 2) side of the second orifice (orifice 41) act in the valve opening direction.

  Further, the fluid pressure control device 300 includes a first orifice (orifice 31) provided in the first connection channel (connection channel 3) and a second orifice provided in the second connection channel (connection channel 4). A charge pump 9 for supplying a working fluid (hydraulic oil) to an orifice (the other of the orifice 41), the first connection flow path (connection flow path 3) and the second connection flow path (connection flow path 4) Charge flow path 10 for guiding the working fluid (working oil) discharged from the first connection flow path (connection flow path 3) and the second connection flow path (connection flow path 4), and charge flow path 10 A first check valve (check valve 12a) that allows only the flow of hydraulic fluid (hydraulic oil) from the pump 9 to the first connection channel (connection channel 3), and a charge pump 9 provided in the charge channel 10 Hydraulic fluid (hydraulic fluid to second connection channel (connection channel 4) The second check valve (check valve 12b), which permits only the flow of the fuel, and the first connection flow passage (connection flow passage 3), is connected to the second connection check valve 12b and charges more than the first check valve (check valve 12a) The first communication passage 151 connected to the pump 9 side, and the charge pump 9 connected to the second connection passage (connection passage 4) and the second check valve (check valve 12b) of the charge passage 10 And the first on-off valve (the first on-off valve 161, the second on-off valve 162) is connected to the first on-off valve 161 provided on the first communication passage 151; A biasing member (spring 161a) for biasing the on / off valve 161 in the valve opening direction, a second on / off valve 162 provided in the second communication passage 152, and a bias for biasing the second on / off valve 162 in the valve opening direction A member (spring 162a), and the first opening The pressure on the discharge device (bidirectional pump 1) side of the first orifice 31 acts on the valve 161 in the valve closing direction and the pressure on the fluid pressure motor (hydraulic motor 2) side of the first orifice 31 opens in the valve 161 The pressure on the discharge device (bidirectional pump 1) side of the second orifice 41 acts on the second on-off valve 162 in the valve closing direction, and the fluid pressure motor (hydraulic motor 2) of the second orifice 41 The pressure on the side acts in the valve opening direction, and the bypass channel (communication channel 150) is the first connection channel through the first communication channel 151 and the charge channel 10, or the second communication channel 152 and the charge channel 10. (Connection flow path 3) and the second connection flow path (connection flow path 4) are connected.

  According to these configurations, even when the discharge device (the bidirectional pump 1) and the on-off valve (the on-off valve 60, the first on-off valve 161, the second on-off valve 162) are separated and can not be connected, both While securing the neutral region of the directional pump 1, volumetric efficiency can be improved.

  The work vehicle is characterized by including any one of the fluid pressure control devices 100, 200, 300, and 400.

  As mentioned above, although the embodiment of the present invention was described, the above-mentioned embodiment showed only a part of application example of the present invention, and in the meaning of limiting the technical scope of the present invention to the concrete composition of the above-mentioned embodiment. Absent.

  Although not shown, the fluid pressure control device 200 can also be configured to function only in the forward direction by not providing the orifice 41 and the channels 42 and 43.

100, 200, 300, 400 · · · Fluid pressure control device, 1 · · · Bidirectional pump (discharge device), 1a · · · Port (first port), 1b · · · Port (second port), 1c ... Swash plate, 2 ... hydraulic motor (fluid pressure motor), 2a ... port, 2b ... port 3, 4 ... connection flow path (first connection flow path or second connection flow Path), 5 ... communication path (bypass flow path), 6 ... on-off valve, 6 a ... operation lever (operation member), 7 ... operation lever (adjustment member), 9 ... charge pump 10: charge flow path, 16: on-off valve, 31, 41: orifice (first and second orifice), 60: on-off valve, 61: spring (biasing member), 150 ··· communication passage, 161 · · · first on-off valve, 161 a · · · spring (biasing member), 162 · · · second Valve closing, 162a: spring (biasing member), 401: discharge device, 402: pump, 403: switching valve, 403a: port (first port), 403b: port (2nd port), 403c ... Operation lever

Claims (5)

A discharge device having a pump for discharging the working fluid from either the first port or the second port;
A fluid pressure motor driven by a working fluid discharged from the discharge device;
A first connection channel connecting a first port of the discharge device and one port of the fluid pressure motor;
A second connection channel connecting the second port of the discharge device and the other port of the fluid pressure motor;
A bypass flow path connecting the first connection flow path and the second connection flow path;
And an on-off valve provided in the bypass channel,
The on-off valve is closed when the flow rate of the working fluid discharged from the discharge device is a predetermined value or more to shut off the bypass flow path, and the flow rate of the working fluid discharged from the discharge device is less than a fixed value The fluid pressure control device is characterized in that the valve is opened to open the bypass channel. The discharge device is a variable displacement bidirectional pump having an adjustment member for adjusting a discharge volume,
The on-off valve has an operating member for operating a valve body for blocking or opening the bypass flow path,
The fluid pressure control device according to claim 1, wherein the operation member is connected to the adjustment member. A first orifice provided in the first connection channel,
A second orifice provided in the second connection channel,
And a biasing member for biasing the on-off valve in the valve opening direction,
The pressure on the discharge device side of the first orifice and the pressure on the discharge device side of the second orifice act on the on-off valve in the valve closing direction, and the fluid pressure motor side of the first orifice The fluid pressure control device according to claim 1, wherein the pressure and the pressure on the fluid pressure motor side of the second orifice act in a valve opening direction. A first orifice provided in the first connection channel,
A second orifice provided in the second connection channel,
A charge pump for supplying a working fluid to the first connection passage and the second connection passage;
A charge flow path for guiding the working fluid discharged from the charge pump to the first connection flow path and the second connection flow path;
A first check valve provided in the charge flow path and permitting only the flow of working fluid from the charge pump to the first connection flow path;
A second check valve provided in the charge flow path and permitting only the flow of the working fluid from the charge pump to the second connection flow path;
A first communication passage connected to the first connection passage and connected to the charge pump side with respect to the first check valve of the charge passage;
And a second communication passage connected to the second connection passage and connected to the charge pump side with respect to the second check valve of the charge passage.
The on-off valve is
A first on-off valve provided in the first communication passage;
An urging member for urging the first on-off valve in the valve opening direction;
A second on-off valve provided in the second communication passage;
And a biasing member for biasing the second on-off valve in the valve opening direction,
The pressure on the discharge device side of the first orifice acts on the first on-off valve in the valve closing direction, and the pressure on the fluid pressure motor side of the first orifice acts on the first on-off valve,
The pressure on the discharge device side of the second orifice acts on the second on-off valve in the valve closing direction, and the pressure on the fluid pressure motor side of the second orifice acts on the second on-off valve,
The bypass flow path connects the first connection flow path and the second connection flow path through the first communication path and the charge flow path, or the second communication path and the charge flow path. The fluid pressure control device according to claim 1.   A work vehicle comprising the fluid pressure control device according to any one of claims 1 to 4.

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