JP2010111344A - Hydraulic device of industrial vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic device of an industrial vehicle favorable for consistently obtaining a kickback improving effect while suppressing energy consumption. <P>SOLUTION: The hydraulic device includes a priority flow rate control valve 5 for changing a partial flow rate to a power steering device 3 by preferentially feeding a working fluid to the power steering device 3, feeding the remaining working fluid to a cargo handling device 4, and introducing steering pilot pressure generated in a load signal port P30 of the power steering device 3 via a load signal line 36, a closed center type cargo handling operation valve 20 which stops the return of the fed working fluid to a tank 13 in a neutral point, and outputs the working pressure of the cargo handling operation as cargo handling pilot pressure during cargo handling operation, a return passage 11 branched from a feed passage to the priority flow rate control valve 5 from a hydraulic pump 2 to return the working fluid to the tank 13, and a back pressure valve 6 which is arranged in the return passage 11 to regulate the operational pressure of the feed passage 10 according to the cargo handling pilot pressure. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a hydraulic device for an industrial vehicle represented by a forklift, and more particularly to a hydraulic device for an industrial vehicle that supplies hydraulic oil from a single hydraulic pump to a power steering device and a cargo handling device. is there.

  2. Description of the Related Art Conventionally, there has been proposed a hydraulic device for an industrial vehicle that supplies hydraulic oil from a single hydraulic pump to a power steering device and a cargo handling device separately (see Patent Document 1).

This is because the hydraulic oil discharged from the hydraulic pump is preferentially divided and supplied to the power steering device by the priority flow control valve, and the remaining hydraulic oil is diverted to the cargo handling valve of the cargo handling device. An orifice for generating a predetermined back pressure is arranged in a path for supplying and discharging the hydraulic oil supplied when the cargo handling operation valve is not operated to the tank, and the cargo handling operation of the cargo handling device is rapidly performed during the operation of the power steering device. In this case, the problem that kickback to the steering wheel occurs when the operation is canceled is canceled.
JP 2006-321267 A

  However, since the conventional example has a configuration in which the back pressure on the cargo handling valve side of the priority flow control valve is generated by the fixed orifice, the back pressure generated by the fixed orifice changes when the flow rate to the cargo handling valve side changes. However, the phenomenon that the kickback improvement effect is not stable occurs. Moreover, in an industrial vehicle in which the hydraulic pump is driven by a travel drive engine (generally, the hydraulic pump is directly connected to the engine), the hydraulic pump rotational speed is determined according to the engine rotational speed associated with the amount of depression of the accelerator pedal. Therefore, depending on the accelerator opening, the flow rate to the cargo handling valve may be small, and the back pressure on the cargo handling valve side may be insufficient, so that a sufficient kickback improvement effect may not be obtained. Conversely, if the flow rate to the cargo handling operation valve is large, the effect of improving the kickback is great, but unnecessary pressure loss due to the fixed orifice occurs and energy is consumed. In particular, an engine-driven industrial vehicle has a problem in that energy consumption increases in this respect because the hydraulic pump is directly connected to the engine and continues to rotate while the vehicle is running.

  Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to provide an industrial vehicle hydraulic device suitable for stably obtaining a kickback improvement effect while suppressing energy consumption.

  The present invention is a steering pilot that preferentially diverts and supplies hydraulic oil from a hydraulic pump to a power steering apparatus and diverts and supplies the remaining hydraulic oil to a cargo handling apparatus and generates at a load signal port of the power steering apparatus. Priority flow rate control valve that changes the flow rate of hydraulic oil to the power steering system according to pressure, and stops or restricts the return of hydraulic oil supplied to the tank when neutral, and is generated by cargo handling operation during cargo handling operation From a closed center type switching valve that outputs the operating pressure as a cargo handling pilot pressure, from a cargo handling operation valve for handling the cargo handling device, a hydraulic oil supply passage from the hydraulic pump to the priority flow control valve, or a priority flow control valve A return passage that branches off from the hydraulic oil supply passage to the cargo handling valve and returns the hydraulic oil to the tank. When, by adjusting the amount of hydraulic oil that recirculates from the supply passage in accordance with the handling pilot pressure to the tank through the return passage, and a back pressure valve for adjusting the working pressure of the supply passage.

  Therefore, in the present invention, the hydraulic oil from the hydraulic pump is preferentially divided and supplied to the power steering apparatus, and the remaining hydraulic oil is diverted and supplied to the cargo handling apparatus, which is generated at the load signal port of the power steering apparatus. A priority flow rate control valve that changes the flow rate of hydraulic fluid to the power steering device according to the steering pilot pressure, and stops or restricts the return of hydraulic fluid supplied to the tank to neutral during neutralization and A cargo handling operation valve composed of a closed center type switching valve that outputs the generated working pressure as a cargo handling pilot pressure, and a hydraulic oil supply passage from the hydraulic pump to the priority flow control valve or from the priority flow control valve to the cargo handling operation valve A return passage that branches off from the hydraulic oil supply passage and returns the hydraulic oil to the tank. By adjusting the amount of hydraulic oil to be returned to the tank via the return passage from the supply passage in accordance with the handling pilot pressure, and a back pressure valve for adjusting the working pressure of the supply passage. For this reason, even if the cargo handling operation is interrupted or stopped during the execution of both the cargo handling operation and the steering operation, the back pressure on the cargo handling valve side can be prevented from abruptly decreasing and sufficient back pressure can be secured. A sufficient kickback improvement effect can be obtained. Moreover, since the flow rate supplied from the hydraulic pump to the cargo handling operation valve via the priority flow rate control valve can be adjusted by the back pressure valve that operates according to the cargo handling pilot pressure, the hydraulic pump that rotates synchronously with the engine rotation and discharges hydraulic oil Even if it is equipped with, the problem of increased energy consumption can be solved.

  Hereinafter, an industrial vehicle hydraulic device of the present invention is explained based on each embodiment.

(First embodiment)
1 to 4 show a first embodiment of an industrial vehicle hydraulic device to which the present invention is applied, FIG. 1 is a hydraulic circuit diagram in which the industrial vehicle hydraulic device is applied to a forklift, and FIG. 2 is an all hydraulic power steering device. FIG. 3 is a hydraulic circuit diagram illustrating details of the priority flow control valve, and FIG. 4 is a cross-sectional view illustrating the structure of the priority flow control valve.

  In FIG. 1, a hydraulic device for an industrial vehicle includes a hydraulic pump 2 driven by a driving engine 1, a cargo handling device 4, an all-hydraulic power steering device 3, and a supply passage 10 from the hydraulic pump 2. A priority flow rate control valve 5 for preferentially diverting the supplied hydraulic oil to the all-hydraulic power steering device 3 and diverting excess hydraulic oil to the cargo handling device 4, and hydraulic oil discharged from the hydraulic pump 2 And a back pressure valve 6 for controlling the hydraulic pressure supplied to the priority flow rate control valve 5. The supply passage 10 is provided with a main relief valve 12 that is opened when the pump discharge hydraulic pressure rises to a predetermined pressure value or more and restricts further pressure rise.

  The hydraulic pump 2 is always driven regardless of whether the vehicle is stopped or traveling, directly connected to the travel drive engine 1 or via a speed reducer, and sucks and discharges hydraulic oil stored in the oil tank 13. Oil is supplied to the supply passage 10. The amount of oil discharged from the hydraulic pump 2 increases / decreases according to the engine speed, and the amount of oil discharged becomes minimum during idle rotation when the accelerator pedal is not depressed, and the oil discharged as the engine speed increases as the accelerator pedal is depressed. The amount also increases.

  In the illustrated example, the cargo handling device 4 is a forklift that includes a lift cylinder and a tilt cylinder as an example of an industrial vehicle. A lift operation valve 21 for operating the lift cylinder 23 and a tilt operation valve 22 for operating the tilt cylinder 24 are provided as a cargo handling operation valve 20, both of which are switched by operation levers 21A and 22A. Any of the lift operation valve 21 and the tilt operation valve 22 may be arranged upstream, but here, the lift operation valve 21 arranged upstream is described.

  The lift operation valve 21 communicates with a pressure oil introduction port P11 that introduces hydraulic oil via a one-way valve, a cylinder port P12 that communicates with a lift cylinder 23, a pilot port P13 that outputs pilot pressure, and a tank 13 A drain port P14 for switching, and a spool 21B for switching communication between these ports.

  Then, the neutral position LN for locking the lift cylinder 23 with the supply and discharge of the hydraulic oil to the lift cylinder 23 shut off, the raised position LU for supplying the hydraulic oil to the lift cylinder 23, and the hydraulic oil is discharged from the lift cylinder 23. The lowering position LD is provided, and these positions can be switched by the lift operation lever 21A.

  In the neutral position LN, the pilot port P13 and the drain port P14 are communicated with each other, and the communication between the pressure oil introduction port P11 and the cylinder port P12 is blocked. Since pilot port P13 communicates with drain port P14, no pilot pressure is generated. In the illustrated example, the communication between the pressure oil introduction port P11 and the drain port P14 is blocked, but a small flow rate may flow between the two by a flow restriction orifice.

  At the raised position LU, the drain port P14 is blocked, the pressure oil introduction port P11 and the cylinder port P12 are communicated with each other via the flow restriction orifice, and the cylinder port P12 and the pilot port P13 are communicated. The supplied hydraulic oil flows from the pressure oil introduction port P11 to the cylinder port P12, extends the lift cylinder 23 communicating with the cylinder port P12, and raises a lift fork (not shown). Further, since the pilot port P13 communicates with the cylinder port P12, a pilot pressure is generated.

  At the lowered position LD, the pressure oil introduction port P11 and the pilot port P13 are blocked, and the cylinder port P12 and the drain port P14 are communicated. The supplied hydraulic oil is blocked from flowing at the pressure oil introduction port P11, while the cylinder port P12 communicates with the drain port P14, so that the hydraulic oil in the lift cylinder 23 is drained via the cylinder port P12 and the drain port P14. Then, the lift cylinder 23 is contracted, and a lift fork (not shown) is lowered. In this case, no pilot pressure is generated.

  A shutoff valve 25 and a descending speed limiting valve 26 are interposed between the lift cylinder 23 and the lift operation valve 21. The shutoff valve 25 maintains a shutoff state when the lowering solenoid valve 27 is in the lowering prohibition position, and is switched to a release state when the lowering solenoid valve 27 is in the lowering permission position. The lowering solenoid valve 27 can be switched by a controller (not shown). Further, the lowering speed limiting valve 26 functions to limit the discharge flow rate of the hydraulic oil at the lowered position LD where the hydraulic oil is discharged from the lift cylinder 23 and to mitigate the impact caused by the rapid contraction of the lift cylinder 23. .

  The tilt operation valve 22 includes a pressure oil introduction port P21 to which hydraulic oil is supplied via a one-way valve, a pair of cylinder ports P22 communicating with the respective cylinders of the tilt cylinder 24, and a pilot port that outputs a pilot pressure. P23, a drain port P24 that communicates with the tank 13, and a spool 22C that switches between these ports for communication.

  Then, the hydraulic oil is supplied to one cylinder chamber of the tilt cylinder 24 from the neutral position TN that locks the tilt cylinder 24 by blocking the supply and discharge of the hydraulic oil to and from the cylinder chamber of the tilt cylinder 24, and from the other cylinder chamber. The hydraulic oil is discharged and the tilt cylinder 24 tilts the mast (not shown) forward, and the hydraulic oil is supplied to the other cylinder chamber of the tilt cylinder 24 and the hydraulic oil is discharged from one cylinder chamber to tilt. The cylinder 24 is provided with a rearward tilt position TU for tilting a mast (not shown), and these positions can be switched by a tilt operation lever 22A.

  At the neutral position TN, the pilot port P23 and the drain port P24 are communicated with each other, and the communication between the pressure oil introduction port P21 and both the cylinder ports P22 is blocked. Since pilot port P23 communicates with drain port P24, no pilot pressure is generated. In the illustrated example, the communication between the pressure oil introduction port P21 and the drain port P24 is blocked, but a small flow rate may flow between the two by a flow restriction orifice.

  In the forward inclined position TD, the pressure oil introduction port P21 and one cylinder port P22 communicate with each other via a flow restriction orifice, the drain port P24 communicates with the other cylinder port P22, and one cylinder port P22. And the pilot port P23 are communicated with each other. The supplied hydraulic oil is introduced into one cylinder chamber of the tilt cylinder 24 from the pressure oil introduction port P21 via one cylinder port P22, and the hydraulic oil in the other cylinder chamber of the tilt cylinder 24 is supplied to the other cylinder port. Drained through P22 and drain port P24. For this reason, the tilt cylinder 24 is extended to tilt a mast (not shown) forward. Since the pilot port P23 communicates with one cylinder port P22, a pilot pressure is generated.

  At the rearward tilted position TU, the drain port P24 and one cylinder port P22 communicate with each other, the pressure oil introduction port P21 and the other cylinder port P22 communicate with each other via a flow restriction orifice, and the other cylinder port P22. And the pilot port P23 are communicated with each other. The supplied hydraulic oil is introduced into the other cylinder chamber of the tilt cylinder 24 from the pressure oil introduction port P21 via the other cylinder port P22, and the hydraulic oil in one cylinder chamber of the tilt cylinder 24 is supplied to one cylinder port. Drained through P22 and drain port P24. For this reason, the tilt cylinder 24 is contracted to tilt the mast (not shown) backward. Since the pilot port P23 communicates with the other cylinder port P22, a pilot pressure is generated.

  As shown in FIG. 2, the power steering device 3 is a known all-hydraulic power steering device 3 including a steering control valve 30 and a steering cylinder 31. The steering control valve 30 is operated by steering a steering handle 33. A metering device 34 called a rotating orbit roll pump and a switching valve 35 are provided. The hydraulic fluid supplied from the hydraulic pump 2 through the PS passage 14 via the priority flow control valve 5 is made to correspond to the steering direction by the switching valve 35 that is switched corresponding to the steering direction, and according to the steering speed. Then, only the flow rate measured by the metering device 34 that rotates is supplied to the steering cylinder 31. The steering cylinder 31 is of a double rod type, and is operated by hydraulic oil supplied from the steering control valve 30 corresponding to the steering direction, and the piston rod 31A is displaced according to the steering direction, thereby moving a knuckle arm (not shown) in the steering direction. The steering wheel (not shown) is steered left or right.

  The switching valve 35 is in a neutral position when the steering handle 33 is not rotated, and cuts off the supply of hydraulic oil supplied from the priority flow control valve 5 through the PS passage 14 to the metering device 34. At the same time, the load signal port P30 is connected to the drain port P31, and the hydraulic oil supplied via the control orifices 36A and 36B of the load signal line 36 and the steering pilot passage 37 is drained to the tank 13 to reduce the steering pilot pressure to zero. And When the steering handle 33 is rotated, the steering wheel 33 is switched from the neutral position according to the rotation direction, and the hydraulic oil supplied from the PS passage 14 is supplied to the metering device 34 according to the rotation direction. The hydraulic pressure supplied to the ring device 34 is output from the load signal port P36 as the steering pilot pressure. The steering pilot pressure and the supply pressure to the metering device 34 are increased or decreased according to the steering speed of the steering handle 33 and the steering load of the steering cylinder 31. As shown in FIG. 1, the steering pilot passage 37 is provided with a relief valve 38 that opens when the steering pilot pressure rises to a predetermined pressure value or more and restricts the pressure rise beyond that.

  As shown in FIGS. 3 and 4, the priority flow control valve 5 includes a power steering device 3 in which hydraulic oil from the hydraulic pump 2 is connected to a PS port P2 that is a priority outflow port via a PS passage 14; The flow is diverted to the cargo handling operation valve 20 of the cargo handling device 4 connected via the EF passage 15 connected to the EF port P3 which is a surplus outflow port. The priority flow rate control valve 5 includes a valve spool 40 for the diversion control, and the diversion ratio between the power steering device 3 side and the cargo handling valve 20 side can be changed according to the position of the valve spool 40.

  One end surface of the valve spool 40 constitutes a spring chamber 42 together with the valve sleeve 41. In the spring chamber 42, a spring 44 that biases the valve spool 40 to the other side and a load pressure that changes in accordance with the steering pilot pressure from the load signal port P 30 of the power steering device 3 in cooperation with the spring 44. Works. The urging force generated by the spring 44 and the load pressure urges the valve spool 40 to be in the B position side (PS port large) in the drawing so that the inflow fluid supplied from the hydraulic pump 2 flows to the power steering device 3 side. Energize to.

  The spring chamber 42 connects the supply pressure to the power steering device 3 to the load signal port P30 of the power steering device 3 via the load signal line 36 having a plurality of control orifices 36A and 36B and the steering pilot passage 37. Are communicated with each other between the plurality of control orifices 36A, 36B. The load pressure is a plurality of control orifices 36A within a pressure region set by the supply pressure (PS pressure) of the PS passage 14 to the power steering device 3 and the steering pilot pressure of the load signal port P30 of the power steering device 3. , 36B is an intermediate pressure generated at the branch point of the load signal line 36 between the two.

  The other end surface of the valve spool 40 constitutes a damper chamber 43 together with the valve sleeve 41. The damper chamber 43 is supplied with the supply pressure to the power steering device 3 via the damping orifice 45 and allows the hydraulic oil to flow out of the damper chamber 43 but prevents the hydraulic oil from flowing into the damper chamber 43. A check valve 46 is provided in parallel with the damping orifice 45. Hereinafter, the damping orifice 45 and the check valve 46 may be collectively referred to as a one-way damper or a damper orifice with a check valve. The supply pressure to the power steering device 3 introduced into the damper chamber 43 urges the valve spool 40 to be at the A position side (large EF port) in the figure, and increases the partial flow rate to the cargo handling valve 20 side. Acts like

  The damping orifice 45 has a damping function for restricting the entry and exit of hydraulic oil in the damper chamber 43 and braking the valve spool 40 so as to move gradually. The check valve 46 connected in parallel with the check valve 46 prevents the hydraulic oil from flowing into the damper chamber 43, and is installed in a direction allowing the hydraulic oil to flow out of the damper chamber 43. The movement to the A position side (large EF port) is gradually moved by the restriction of the damping orifice 45, and the movement to the B position side (large PS port) can be moved quickly without being restricted by the damping orifice 45. Yes.

  When the steering operation is not performed, the urging force due to the spring force and the load pressure of the spring chamber 43 is opposed to the counter force caused by the supply pressure to the power steering device 3 of the damper chamber 43 opposed across the valve spool 40. And is set to be large. That is, the hydraulic oil supplied to the priority flow rate control valve 5 acts on the damper chamber 43 to urge the valve spool 40 toward the A position. The hydraulic fluid supplied to the priority flow rate control valve 5 is drained from the load port P30 of the power steering device 3 via the load signal line 36 and the steering pilot passage 37, and the control orifices 36A and 36B of the load signal line 36. The intermediate pressure (load pressure) is introduced into the spring chamber 42 and urges the valve spool 40 to the B position side together with the spring force. Since the intermediate pressure (load pressure) is dropped by the upstream control orifice 36A, the spring 44 that exerts an urging force that exceeds the pressure drop is adopted, so that the valve spool 40 can be operated when the steering is not operated. It is set to be located on the position side (PS port is large).

  Further, as shown in FIG. 4, even when the valve spool 40 reaches the stroke end on the B position side (the direction in which the spring 44 extends), the opening degree to the cargo handling valve 20 side, that is, the EF port P3, is a predetermined opening degree. It is set not to be below. As a result, when the opening to the EF port P3 is closed, the pilot flow rate from the cargo handling operation valve 20 cannot be secured, and the phenomenon that the cargo handling operation becomes impossible can be prevented. The pilot flow rate is ensured and stable cargo handling control is possible. Therefore, in the illustrated example, a stopper 43 </ b> A that restricts the stroke of the valve spool 40 is disposed in the damper chamber 43. Further, even if the valve spool 40 reaches the stroke end, the shape of the valve spool 40 and the shape of the valve sleeve 41 are changed so that the opening degree to the cargo handling valve 20 (EF port P3) is secured. You may make it change into the opening characteristic.

  The back pressure valve 6 is disposed in a return passage 11 for branching a supply passage 10 for supplying hydraulic oil discharged from the hydraulic pump 2 to the priority flow rate control valve 5 and returning it to the tank 13. And the introduction port P5 connected to the supply channel | path 11, the drain port P6 connected to the oil tank 13, and the valve spool 50 which controls the communication state of these ports are provided. The valve spool 50 can gradually change its valve opening according to its position, and the hydraulic oil supplied from the hydraulic pump 2 to the priority flow rate control valve 5 is diverted according to the valve opening to provide oil. It functions to drain the tank 13 and reduce the amount of hydraulic oil supplied to the priority flow control valve 5.

  One end face of the valve spool 50 constitutes a spring chamber 52 together with a valve sleeve (not shown). A spring 54 that urges the valve spool 50 to the other and a pilot pressure described later in cooperation with the spring 54 acts on the spring chamber 52. The biasing force generated by the spring 54 and the pilot pressure biases the valve spool 50 to the other side, and acts so that the back pressure valve 6 is closed.

  The pilot pressure introduced into the spring chamber 52 includes a handling pilot pressure from the pilot ports P13 and P23 of the lift operation valve 21 and the tilt operation valve 22 of the cargo handling device 4, and a steering pilot from the load signal port P30 of the power steering device 3. Pressure is introduced. The steering pilot pressure is introduced through a steering pilot passage 37 connected to the load signal port P30 of the power steering device 3.

  The cargo handling pilot pressure is connected to the pilot ports P13 and P23 of the lift operating valve 21 and the tilt operating valve 22 of the cargo handling device 4, respectively, and is introduced through the cargo handling pilot passage 16 including the shuttle valve 16A and the damping orifice 16B. The shuttle valve 16A selects and introduces the pilot pressure on the higher side of the pilot ports P13 and P23 of the lift operation valve 21 and the tilt operation valve 22 at a high level. The cargo handling pilot passage 16 is connected to the oil tank 13 via an unloading valve 18. When the unloading valve 18 is opened, the cargo handling pilot passage 16 is communicated with the oil tank 13, The pilot pressure is drained to zero pressure. The cargo handling pilot pressure and the steering pilot pressure are selected high by the shuttle valve 17 and the higher pressure value is introduced.

  The other end surface of the valve spool 50 constitutes a damper chamber 53 together with a valve sleeve (not shown). The damper chamber 53 is connected to the supply passage 10 via a damping orifice 55, and supply pressure to the priority flow rate control valve 5 is introduced. Further, a check valve 56 that allows the hydraulic oil to flow out of the damper chamber 53 but prevents the hydraulic oil from flowing into the damper chamber 53 is provided in parallel with the damping orifice 55. Hereinafter, the damping orifice 55 and the check valve 56 may be collectively referred to as a one-way damper or a damper orifice with a check valve. The supply pressure to the priority flow rate control valve 5 introduced into the damper chamber 53 urges the valve spool 50 to one side so that the back pressure valve 6 is opened.

  The damping orifice 55 has a damping function for restricting the entry and exit of hydraulic oil in the damper chamber 53 and braking the valve spool 50 so as to move gradually. Further, the check valve 56 connected in parallel with the check valve 56 is installed in a direction to prevent the hydraulic oil from flowing into the damper chamber 53 while allowing the hydraulic oil to flow out from the damper chamber 53. Therefore, the movement of the valve spool 50 toward the valve opening side is gradually opened due to the restriction of the damping orifice 55, and the movement of the valve spool 50 toward the valve closing side is promptly closed without being restricted by the damping orifice 55. It is possible to move.

  The back pressure valve 6 branches and drains part of the oil discharged from the hydraulic pump 2 to the oil tank 13 while being throttled by the valve spool 50, and supplies the remaining hydraulic oil to the priority flow control valve 5. The urging force according to the spring force of the spring chamber 52 and the pilot pressure urges the valve spool 50 in the valve closing direction to restrict the branch flow to the oil tank 13 and supply the pressure to the priority flow control valve 5 (damper chamber 53). Pressure) is smaller than the urging force, the valve spool 50 is further moved in the valve closing direction to reduce the throttle opening, and the pressure supplied to the priority flow control valve 5 (damper chamber) 53 pressure). Further, when the counter force due to the pressure supplied to the priority flow control valve 5 (pressure in the damper chamber 53) becomes larger than the urging force, the valve spool 50 is moved in the valve opening direction to increase the throttle opening. The pressure supplied to the priority flow control valve 5 (pressure in the damper chamber 53) is decreased by increasing the pressure. Then, the counter force generated by the pressure supplied to the priority flow rate control valve 5 (pressure in the damper chamber 53) is stopped in a state where it is balanced with the biasing force, and the pressure supplied to the priority flow rate control valve 5 corresponds to the biasing force. Adjust to pressure value.

  For this reason, when the pilot pressure in the spring chamber 52 is reduced, the pressure supplied to the priority flow control valve 5 is increased by increasing the branch flow to the tank 13 by moving the valve spool 50 in the valve opening direction. The pressure is reduced to a pressure value corresponding to the urging force by 54. Further, when the pilot pressure in the spring chamber 52 is increased, the valve spool 50 is moved in the valve closing direction to reduce the branch flow to the tank 13, and the pressure value corresponding to the urging force by the spring 54 and the pilot pressure. To rise.

  Further, when the power steering device 3 is not operated, the steering pilot pressure introduced into the spring chamber 52 becomes zero, so that the valve spool 50 is pressed in the valve closing direction by the urging force of only the spring 54. For this reason, most of the hydraulic oil supplied from the hydraulic pump 2 is drained to the oil tank 13 via the back pressure valve 6, and the pressure supplied to the priority flow control valve 5 is reduced to a pressure value corresponding to the urging force. Thus, a small amount of hydraulic oil is supplied to the priority flow control valve 5 in a low pressure state. The supplied low-pressure and small-flow hydraulic fluid passes through the control orifice 36 </ b> A on the upstream side of the priority flow control valve 5 and is introduced into the spring chamber 52. Therefore, the spring 54 disposed in the spring chamber 52 of the priority flow control valve 5 is selected to have an urging force exceeding the pressure drop of the upstream control orifice 36A in this state. That is, when the power steering device 3 is not operated, the biasing force of the back pressure valve 6 (pilot pressure + spring pressure) = the supply pressure to the priority flow control valve 5 <the biasing force of the spring chamber 52 of the priority flow control valve 5 ( The downstream pressure of the upstream control orifice 36 </ b> A is set to have the relationship of the spring pressure and the spring force.

  The operation of the hydraulic device for an industrial vehicle having the above configuration will be described below. In an engine-driven vehicle, when the engine 1 is started by an ignition key, the hydraulic pump 2 is driven, and a small amount of discharged hydraulic oil is supplied to the priority flow control valve 5 and most of the hydraulic fluid is passed through the back pressure valve 6. And drained to the tank 13. The priority flow rate control valve 5 divides and supplies the supplied hydraulic oil to the steering control valve 30 of the power steering device 3 and the cargo handling operation valve 20 of the cargo handling device 4, and the control orifices 36 A and 36 B of the load signal line 36 and This is supplied to the load signal port P30 in the switching valve 35 of the steering control valve 30 via the steering pilot passage 37. FIG. 5 is a time chart showing the pressure characteristics and flow characteristics of the priority flow control valve 5 at the start of the power steering operation. Hereinafter, the time chart shown in FIG. 5 will also be described.

  Since the steering operation is not being performed, the hydraulic fluid to the power steering device 3 is blocked by the switching valve 35, and the cargo handling operation valve 20 is in a non-operation state, and therefore is in a neutral position of the lift operation valve 21 and the tilt operation valve 22 and lift operation. The hydraulic oil to the valve 21 and the tilt operation valve 22 is blocked by the pressure oil introduction ports P11 and P21. The hydraulic fluid supplied from the priority flow control valve 5 to the load signal port P30 of the steering control valve 30 via the control orifices 36A and 36B of the load signal line 36 and the steering pilot passage 37 is drained by the switching valve 35. The steering pilot pressure is set to zero. Since the pilot ports P13 and P23 are in communication with the drain ports P14 and P24 because the lift operation valve 21 and the tilt operation valve 22 are in the neutral positions, the handling pilot pressure output from the handling pilot passage 16 is also zero. Set to For this reason, the pressure value supplied to the priority flow control valve 5 is set so that the back pressure valve 6 has the lowest pressure value (for example, 0.5 [MPa]) that is commensurate with the urging force of the spring 54 disposed in the spring chamber 52. Set. For this reason, most of the hydraulic fluid discharged from the hydraulic pump 2 is drained to the tank 13 via the back pressure valve 6, and only the low flow rate (for example, 1 [L / min]) hydraulic fluid is a priority flow rate control valve. 5 is supplied.

  In the priority flow control valve 5, the steering pilot pressure of the load signal port P30 of the power steering device 3 is zero, so that the load pressure of the spring chamber 42 introduced through the steering pilot passage 37 and the load signal line 36 is as described above. Is set to the minimum pressure. However, as described above, the priority flow rate control valve 5 sets the supply flow rate to a low flow rate (for example, 1 [L / min]) by the back pressure valve 6 when the steering operation is not started (time t0 in FIG. 5D). Therefore, the load pressure and the urging force of the spring 44 overcome the opposing force of the opposing damper chamber 43 and are located on the B position side, so that the opening amount of the PS port P2 is increased. (See time points t0 to t1 in FIG. 5B). Note that the pressure of the PS port P2 is, for example, 0.5 [MPa] set by the back pressure valve 6 (see time points t0 to t1 in FIG. 5C). In this case, since the engine 1 is rotating in an idling state and the hydraulic pump 2 is driven at a relatively low rotation, a small amount of hydraulic fluid is discharged.

  When a forward / reverse lever (not shown) is switched from a neutral position to a forward position or a reverse position and the accelerator pedal is depressed, the drive wheels are driven via a transmission / final speed reducer (not shown) to advance or reverse the vehicle. Traveling starts. As the engine speed increases, the discharge flow rate of the hydraulic pump 2 also increases. However, since neither the steering operation nor the cargo handling operation is performed, the set pressure by the back pressure valve 6 does not change, so the amount of increase in the discharge hydraulic oil is It is drained to the tank 13 by the back pressure valve 6.

  When the steering handle 33 is steered while the vehicle is traveling straight (time t1 in FIG. 5), the steering pilot pressure from the load signal port P30 also increases according to the steering load and the operation speed of the steering handle 33. The rise of the steering pilot pressure is introduced into the spring chamber 52 of the back pressure valve 6 via the steering pilot passage 37 and the shuttle valve 17, and the urging force for urging the valve spool 50 in the valve closing direction is increased. Increase the set pressure. For this reason, the valve spool 50 of the back pressure valve 6 moves in a direction in which the return passage 11 is suddenly closed, and the power steering pressure also suddenly rises, for example, to about 6.3 MPa (see time points t1 to t2 in FIG. 5C). ).

  At the same time, the flow rate to the return passage 11 also decreases, so that the supply flow rate to the priority flow rate control valve 5 is rapidly increased (for example, 10 [L / min]) (see time points t1 to t2 in FIG. 5D). The movement of the back pressure valve 6 in the valve closing direction of the valve spool 50 is promptly executed without causing movement resistance by a one-way damper with a check valve 56 in a pilot passage that connects the damper chamber 53 to the supply passage 10. The

  The hydraulic oil supplied to the power steering device 3 operates the steering cylinder 31 via the steering control valve 30 to steer the steered wheels according to the steering of the steering handle 33. In this case, since the power steering flow rate and the power steering pressure are sufficiently ensured, the catch at the beginning of turning of the steering operation is improved. Note that the load pressure of the priority flow control valve 5 gradually increases via the control orifices 36A and 36B due to the increase of the steering pilot pressure and urges the valve spool 40 toward the B position. Since the pressure rises quickly, the valve spool 40 slightly moves to the A position side (see time points t1 to t2 in FIG. 5B).

  By the way, the hydraulic device of the conventional example is configured to include an open center type cargo handling operation valve. When the steering operation is not started, the power steering pressure is about 0.5 MPa, and the priority flow control valve The PS port opening amount is small (see the broken line at time points t0 to t1 in FIG. 5B), and is positioned on the A position side for supplying most of the excess hydraulic oil to the cargo handling valve. When steering operation is started from this state, the PS spool opening amount of the priority flow control valve needs to move in the direction from small to large, and the control orifice of the load signal line becomes resistance, and the valve spool moves It takes time, and the power steering pressure and the power steering flow rate increase only slowly (see broken lines at time points t1 to t3 in FIGS. 5C and 5D). For this reason, there is a problem that the steering operation is caught.

  However, in the present embodiment, the back pressure valve 6 is disposed upstream of the priority flow control valve 5, and most of the pump supply flow is discharged to the return passage 11 to the tank 13 by the back pressure valve 6. The amount of opening on the PS port P2 side of the priority flow rate control valve 5 is prevented from being reduced to a small value by reducing the supply flow rate to. Therefore, when the steering operation is started from this state, the opening amount of the priority flow rate control valve 5 on the PS port P2 side is not required without requiring the valve spool 40 of the priority flow rate control valve 5 to move to the B position side. Is already large, a sufficient flow rate is ensured as the supply flow rate to the power steering device 3 and the steering at the beginning of turning of the steering handle 33 is improved.

  When the vehicle is decelerated to start the cargo handling operation and one of the cargo handling levers 21A and 22A is operated, the lift operation valve 21 or the tilt operation valve 22 is switched from the neutral positions LN and TN to the operation position. Then, the supplied hydraulic oil is introduced into the target cylinder and the cargo handling operation is started. At the same time, the cargo handling pilot pressure is introduced into the pilot ports P13 and P23 of the lift operating valve 21 or the tilt operating valve 22, and the cargo handling pilot pressure reaches the cargo handling pilot passage 16 and the shuttle valve 17. The shuttle valve 17 selects the higher pressure of the steering pilot passage 37 or the cargo handling pilot passage 16 and introduces it into the spring chamber 52 of the back pressure valve 6 (in general, the cargo handling pilot pressure is often high).

  The back pressure valve 6 introduces a cargo handling pilot pressure that is normally higher than the steering pilot pressure, thereby increasing the set pressure and reducing the return discharge amount to the tank 13. At the same time, although not shown, an operation amount sensor for detecting the operation amount of the cargo handling levers 21A and 22A is installed in the vehicle. In an engine-driven vehicle, the engine speed is increased based on the operation amount at that time, The flow rate of the hydraulic oil discharged from the hydraulic pump 2 is increased. For this reason, the hydraulic pressure and hydraulic fluid amount of hydraulic fluid supplied from the hydraulic pump 2 to the priority flow rate control valve 5 are increased.

  The priority flow rate control valve 5 does not change the steering pilot pressure from the load signal port P30 on the power steering device 3 side, and the load pressure introduced into the spring chamber 42 via the load signal line 36 is slightly increased. Therefore, without increasing the amount of hydraulic fluid supplied to the power steering device 3, the flow rate of hydraulic fluid supplied to the cargo handling valve 20 of the cargo handling device 4 is increased according to the amount of manipulation of the cargo handling levers 21A and 22A ( It is biased toward the position A in FIG. As a result, hydraulic oil having a flow rate corresponding to the amount of operation of the operated cargo handling levers 21A and 22A is supplied to the hydraulic cylinder of the cargo handling equipment such as the lift cylinder 23 or the tilt cylinder 24 operated from the lift operation valve 21 or the tilt operation valve 22. The cargo handling device 4 is actuated at an operating speed corresponding to the operation amount of the cargo handling levers 21A and 22A.

  As described above, the time chart showing the pressure characteristics of the priority flow control valve 5 when the operation of the cargo handling device 4 is stopped from the state where both the power steering device 3 and the cargo handling device 4 are being operated. 6 will be described.

  In a state where both the power steering device 3 and the cargo handling device 4 are operated (time points t5 to t6), the power steering pressure of the PS port P2 of the priority flow control valve 5 is, for example, 6.3 [MPa], The cargo handling pressure of the EF port P3 is increased to, for example, 15 [MPa] corresponding to the load.

  When the operation of the cargo handling device 4 is stopped from this state (time t6), the lift operation valve 21 or the tilt operation valve 22 is returned to the neutral positions LN and TN. By switching to the neutral positions LN and TN of the lift operation valve 21 or the tilt operation valve 22 of the cargo handling device 4, the pilot ports P13 and P23 are connected to the drain ports P14 and P24, and the cargo handling pilot pressure is reduced to zero.

  The pilot pressure in the spring chamber 52 of the back pressure valve 6 is switched from the handling pilot pressure (high) to the steering pilot pressure (medium). The back pressure valve 6 operates the valve spool 50 in the valve opening direction to lower the set pressure, but the valve spool 50 operates only slowly in the valve opening direction by the damper orifice 55 provided in the pilot passage to the damper chamber 53. .

  The lift operation valve 21 and the tilt operation valve 22 employ a closed center cargo handling operation valve 20. For this reason, the destination of the hydraulic oil supplied to the cargo handling valve 20 disappears, and the pressure on the cargo handling valve 20 side (EF port P3 side) and the pressure on the power steering device 3 side (PS port P2 side) are reversed. To the relief pressure set by the main relief valve 12 and the relief valve 38 of the cargo handling pilot passage 37 for a moment, then the pressure on the cargo handling valve 20 side (EF port P3 side) and the power steering device 3 side (PS The pressure on the port P2 side) does not drop rapidly, but slowly decreases.

  The priority flow rate control valve 5 moves to the B position side (PS port P2 large, EF port P3 small) in response to a decrease in supply pressure and supply flow rate, and supply pressure (EF port P3 pressure) to the cargo handling operation valve 20 and The supply amount is reduced to secure the supply pressure (PS port P2 pressure) and supply amount to the power steering device 3 (time t7). Then, the pressure is reduced to a pressure set by the steering pilot pressure of the back pressure valve 6, for example, 6.3 [MPa] and converges (time t8).

  By the way, the conventional hydraulic device is configured to include an open center type cargo handling operation valve, and the operation of the cargo handling device is stopped when both the power steering device and the cargo handling device are operated. In, the supply pressure (EF port pressure) to the cargo handling valve is rapidly reduced. In conjunction with the rapid decrease in the supply pressure to the cargo handling operation valve, the supply pressure (PS port pressure) to the power steering device is simultaneously decreased as shown by the broken line in FIG. Then, the switching movement of the valve spool braked by the control orifice of the priority flow rate control valve to the B position is completed, and the supply pressure to the power steering device is returned to the required pressure value (time t7). This temporary decrease in the supply pressure causes a temporary decrease in the assist force of the power steering apparatus, and causes a kickback that temporarily increases the operating force of the steering handle.

  On the other hand, in this embodiment, when the cargo handling operation is turned OFF during the steering operation + the cargo handling operation, the cargo handling operation valves 21 and 22 close the pressure oil introduction ports P11 and P21, and at the same time, the back pressure valve 6 The pilot pressure is switched from the handling pilot pressure (high) to the steering pilot pressure (medium). Although the back pressure valve 6 operates in a direction to reduce the back pressure, the back pressure valve 6 operates only slowly in the direction of opening the opening area by the damper orifice 55 provided in the passage to the damper chamber 53. The pressure on the 20 side (EF port P3 side) and the pressure on the power steering device 3 side (PS port P2 side) do not decrease suddenly, but gradually decrease. The catch can be improved. In the engine-driven vehicle, when the operation amount of the cargo handling levers 21A and 22A becomes zero, the engine speed is decreased with respect to the operation of the cargo handling device 4, and the amount of hydraulic oil discharged from the hydraulic pump 2 is reduced. Let

  When the operation of the steering handle 33 is stopped, the hydraulic oil to the power steering device 3 is shut off by the switching valve 35, the steering pilot pressure is reduced to zero, and the pilot pressure introduced into the spring chamber 52 of the back pressure valve 6 is also reduced. Reduced to zero. For this reason, the pressure value supplied to the priority flow control valve 5 is set so that the back pressure valve 6 has the lowest pressure value (for example, 0.5 [MPa]) that is commensurate with the urging force of the spring 54 disposed in the spring chamber 52. Set. For this reason, most of the hydraulic fluid discharged from the hydraulic pump 2 is drained to the tank 13 via the back pressure valve 6, and only the low flow rate (for example, 1 [L / min]) hydraulic fluid is a priority flow rate control valve. 5 is supplied.

  In the priority flow control valve 5, the steering pilot pressure of the load signal port P30 of the power steering device 3 is zero, so that the load pressure of the spring chamber 42 introduced through the steering pilot passage 37 and the load signal line 36 is as described above. Is set to the minimum pressure. However, as described above, the priority flow rate control valve 5 has a low flow rate (for example, 1 [L / min]) by the back pressure valve 6 when the steering operation is not started. The biasing force with the spring 44 overcomes the opposing force of the opposing damper chamber 43 and is positioned on the B position side so that the opening amount of the PS port P2 is increased. Note that the pressure of the PS port P2 is set at the back pressure valve 6, for example, 0.5 [MPa].

  Further, when only the cargo handling device 4 is operated, the priority flow rate control valve 5 is configured so that even if the valve spool 40 reaches the stroke end on the B position side (direction in which the spring 44 extends), That is, since the opening to the EF port P3 is set so as not to be less than or equal to the predetermined opening, the pilot flow rate from the cargo handling valve 20 is reliably ensured and stable cargo handling operation is possible. For this reason, the lift operation valve 21 or the tilt operation valve 22 is switched from the neutral positions LN and TN to the operation position, and the supplied hydraulic oil is introduced into the target cylinder to start the cargo handling operation.

  At the same time, cargo handling pilot pressure is introduced into the pilot ports P13 and P23 of the lift operating valve 21 or the tilt operating valve 22, and the cargo handling pilot pressure passes through the cargo handling pilot passage 16 and the shuttle valve 17 into the spring chamber 52 of the back pressure valve 6. Introduce. The back pressure valve 6 increases its set pressure and reduces the return discharge amount to the tank 13 when the cargo handling pilot pressure is introduced. For this reason, the hydraulic pressure and hydraulic fluid amount of hydraulic fluid supplied from the hydraulic pump 2 to the priority flow rate control valve 5 are increased.

  The priority flow rate control valve 5 increases the pressing force of the damper chamber 43 as the amount of supply oil and the supply pressure increase, and the valve spool 40 moves from the stroke end on the B position side (the direction in which the spring 44 extends) to the A position side. The amount of hydraulic oil that is moved in the direction of contracting the spring 44 and supplied to the cargo handling operation valve 20 of the cargo handling device 4 is increased in accordance with the amount of operation of the cargo handling levers 21A and 22A. As a result, hydraulic oil having a flow rate corresponding to the amount of operation of the operated cargo handling levers 21A and 22A is supplied to the hydraulic cylinder of the cargo handling equipment such as the lift cylinder 23 or the tilt cylinder 24 operated from the lift operation valve 21 or the tilt operation valve 22. The cargo handling device 4 is actuated at an operating speed corresponding to the operation amount of the cargo handling levers 21A and 22A. Then, the engine speed is increased based on the operation amount of any of the cargo handling levers 21 </ b> A and 22 </ b> A at that time, and the flow rate of the hydraulic oil discharged from the hydraulic pump 2 is increased and supplied to the priority flow rate control valve 5.

  Since the steering handle 7 is not operated, the priority flow rate control valve 5 minimizes the amount of hydraulic oil to be supplied by reducing the opening amount of the PS port P2 to the power steering device 3 so that the cargo handling device 4 can handle the cargo. The flow rate of hydraulic oil supplied by increasing the opening amount of the EF port P3 to the operation valve 20 is increased according to the operation amount of the cargo handling levers 21A and 22A. As a result, the hydraulic cylinder of the cargo handling device 4 such as the tilt cylinder 24 or the lift cylinder 23 operated by the tilt operation valve 22 or the lift operation valve 21 is supplied with hydraulic oil at a flow rate corresponding to the operated amount of the operated cargo handling levers 21A and 22A. The cargo handling device 4 can be operated at an operation speed corresponding to the operation amount of the cargo handling levers 21A and 22A.

  In the present embodiment, the following effects can be achieved.

  (A) The hydraulic oil discharged from the hydraulic pump 2 is preferentially diverted and supplied to the power steering device 3 and the remaining hydraulic oil is diverted and supplied to the cargo handling device 4, and the load signal of the power steering device 3 is supplied. A priority flow rate control valve 5 for changing the flow rate of hydraulic fluid to the power steering device 3 by introducing a steering pilot pressure generated at the port P30 via a load signal line 36 having control orifices 36A and 36B; The cargo handling is constituted by a closed center type switching valve which stops or restricts the return of the hydraulic oil supplied at the time of neutral to the tank 13 and outputs the working pressure generated by the cargo handling operation during the cargo handling operation as a cargo handling pilot pressure. The material handling valve 20 for operating the device 4 and the hydraulic fluid from the hydraulic pump 2 to the priority flow rate control valve 5 A return passage 11 branched from the supply passage to return the hydraulic oil to the tank 13 and disposed in the return passage 11 and returned to the tank 13 from the supply passage 10 via the return passage 11 according to the cargo handling pilot pressure. And a back pressure valve 6 for adjusting the operating pressure of the supply passage 10 by adjusting the amount of hydraulic oil to be adjusted.

  For this reason, even when the cargo handling operation is interrupted or stopped during the execution of both the cargo handling operation and the steering operation, the back pressure valve 6 generates the back pressure when the cargo handling operation valve 20 returns to the neutral position. Therefore, it is possible to stabilize the back pressure, prevent a sudden pressure drop, prevent the back pressure on the cargo handling valve 20 side from abruptly decreasing, and secure a sufficient back pressure. A catching effect, that is, a sufficient kickback improvement effect can be obtained. Moreover, since the flow rate supplied from the hydraulic pump 2 to the cargo handling operation valve 20 via the priority flow rate control valve 5 can be adjusted by the back pressure valve 6 that operates according to the cargo handling pilot pressure, the hydraulic oil is rotated synchronously with the engine rotation. Even if the hydraulic pump 2 for discharging is mounted, the problem that the energy consumption increases can be solved.

  (A) The hydraulic oil discharged from the hydraulic pump 2 is preferentially divided and supplied to the power steering device 3 and the remaining hydraulic oil is diverted and supplied to the cargo handling device 4. A priority flow rate control valve that changes the flow rate of hydraulic fluid to the power steering device 3 by introducing the steering pilot pressure generated at the load signal port P30 via the load signal line 36 having the control orifices 36A and 36B. 5, a cargo handling operation valve 20 for operating the cargo handling device 4, which includes a switching valve of a closed center type that stops or restricts the return of hydraulic oil supplied to the tank 13 during neutrality, and priority from the hydraulic pump 2. A return passage 11 that branches from the hydraulic oil supply passage 10 to the flow control valve 5 and returns the hydraulic oil to the tank 13; The operating pressure of the supply passage 10 is adjusted by adjusting the amount of hydraulic oil that is disposed in the return passage 11 and returns from the supply passage 10 to the tank 13 via the return passage 11 according to the steering pilot pressure. A back pressure valve 6.

  For this reason, when the steering operation is not performed, the back pressure valve 6 discharges most of the pump supply flow rate to the return passage 11 to reduce the supply flow rate to the priority flow rate control valve 5. The amount of opening on the power steering device 3 side is prevented from being reduced. When the steering operation is started, the back pressure valve 6 receives the steering pilot pressure, operates the opening area of the return passage 11 in the closing direction, and sharply reduces the discharge amount to the tank 13 to control the priority flow rate control. The supply flow rate to the valve 5 is increased. At this time, since the opening amount of the priority flow control valve 5 on the power steering device 3 side is already large as described above, it is not necessary to move the opening amount of the priority flow control valve 5 on the power steering device 3 side. A sufficient flow rate is ensured as the steering flow rate, and the catch at the beginning of turning of the steering operation can be improved. In addition, a hydraulic pump 2 that rotates in synchronization with engine rotation and discharges hydraulic oil is installed to adjust the flow supplied from the hydraulic pump 2 to the priority flow control valve 5 by the back pressure valve 6 that operates according to the steering pilot pressure. Even if it does, the malfunction that energy consumption becomes large can be eliminated.

  (C) The hydraulic oil discharged from the hydraulic pump 2 is preferentially divided and supplied to the power steering device 3 and the remaining hydraulic oil is diverted and supplied to the cargo handling device 4, and the load signal of the power steering device 3 is supplied. A priority flow rate control valve 5 for changing the flow rate of hydraulic fluid to the power steering device 3 by introducing a steering pilot pressure generated at the port P30 via a load signal line 36 having control orifices 36A and 36B; The cargo handling is constituted by a closed center type switching valve which stops or restricts the return of the hydraulic oil supplied at the time of neutral to the tank 13 and outputs the working pressure generated by the cargo handling operation during the cargo handling operation as a cargo handling pilot pressure. The cargo handling valve 20 for operating the device 4 and the supply of hydraulic oil from the hydraulic pump 2 to the priority flow control valve 5 A return passage 11 that branches off from the passage 10 and returns the hydraulic oil to the tank 13, and is disposed in the return passage 11, and passes through the return passage 11 from the supply passage 10 according to the steering pilot pressure and the handling pilot pressure. A back pressure valve 6 that adjusts the operating pressure of the supply passage 10 by adjusting the amount of hydraulic oil to be returned to the tank 13.

  For this reason, the back pressure valve 6 generates a back pressure when the cargo handling operation is interrupted or stopped during the execution of both the cargo handling operation and the steering operation. It can prevent the decrease, prevent the back pressure on the cargo handling valve 20 side from abruptly decreasing and secure a sufficient back pressure, and can catch the steering operation when the cargo handling is OFF, that is, has a sufficient kickback improvement effect. be able to. When the steering operation is not being performed, the back pressure valve 6 discharges most of the pump supply flow rate to the return passage 11 to reduce the supply flow rate to the priority flow rate control valve 5, thereby reducing the power of the priority flow rate control valve 5. The opening amount on the steering device 3 side is prevented from being reduced. When the steering operation is started, the back pressure valve 6 receives the steering pilot pressure, operates the opening area of the return passage 11 in the closing direction, and sharply reduces the discharge amount to the tank 13 to control the priority flow rate control. The supply flow rate to the valve 5 is increased. At this time, since the opening amount of the priority flow rate control valve 5 on the power steering device 3 side is already large as described above, the opening amount of the priority flow rate control valve 5 on the power steering device 3 side is increased without any movement. A sufficient flow rate is ensured as the steering flow rate, and the catch at the beginning of turning of the steering operation can be improved.

  Moreover, since the flow rate supplied from the hydraulic pump 2 to the priority flow rate control valve 5 can be adjusted by the back pressure valve 6 that operates according to the cargo handling pilot pressure and the steering pilot pressure, the hydraulic pressure that rotates synchronously with the engine rotation and discharges the hydraulic oil Even if the pump 2 is mounted, the problem of increased energy consumption can be solved.

  (D) The back pressure valve 6 has a damper orifice 55 in the hydraulic oil supply passage 10 from the hydraulic pump 2 to the priority flow control valve 5 (or the hydraulic oil supply passage 15 from the priority flow control valve 5 to the cargo handling valve 20). The valve spool 50 is seated on one end surface of the valve spool 50 to which the cargo handling pilot pressure or the steering pilot pressure is introduced so as to face the other end surface of the valve spool 50 through which the feedback pressure is introduced. The priority flow control valve 5 is provided with a spring 54 and is opposed to the other end surface of the valve spool 40 that introduces feedback pressure into the hydraulic oil supply passage 14 to the power steering device 3 via the damper orifice 45. Valves for introducing pilot pressure through control orifices 36A, 36B of the load signal line 36 A spring 44 that sits on one end face of the handle 40 and biases the valve spool 40 to the other, and acts on one end of the back pressure valve 6 when the power steering device 3 is not operated. The biasing force that acts on one end of the priority flow control valve 5 and presses the valve spool 40 to the other is set larger than the biasing force that presses the valve spool 50 to the other.

  As a result, the biasing force on the spring chamber 42 side of the priority flow control valve 5 when the power steering device 3 is not operated can always be greater than the pressure on the damper chamber 43 side of the priority flow control valve 5. 5 moves in the direction in which the spring 44 extends, and can create a state where the opening degree of the priority flow control valve 5 on the power steering device 3 side becomes large. From this state, when the steering operation is started, the back pressure valve 6 receives the steering pilot pressure, operates the opening area of the return passage 11 in the closing direction, and drastically reduces the discharge amount to the tank 13 to give priority. The supply flow rate to the flow control valve 5 is increased. At this time, since the opening amount of the priority flow rate control valve 5 on the power steering device 3 side is already large, the valve spool 40 does not need to be moved to the opening amount increasing side on the power steering device 3 side, and the power steering flow rate is set. A sufficient flow rate can be secured, and the catch at the beginning of turning of the steering operation can be improved.

  Even when the power steering device 3 is in the relief state, the back pressure valve 6 and the priority flow control valve 5 are in the same pressure relationship as in the above state, so the power steering device 3 side of the priority flow control valve 5 is open. The amount is in a large state. For this reason, when the steering operation is switched from there, the opening amount on the power steering device 3 side of the priority flow rate control valve 5 has already increased, so the opening amount on the power steering device 3 side is the movement resistance of the valve spool 40. Therefore, it is possible to sufficiently secure the power steering flow rate, and to improve the catch when turning back the steering operation.

  (E) In the priority flow rate control valve 5, even when the valve spool 40 is biased to the other and the valve spool 40 reaches the stroke end, the valve opening degree with respect to the supply passage 15 to the cargo handling valve 20 is set in advance. Since the opening is set to a predetermined opening, when the opening to the cargo handling valve 20 side port P3 is closed, the pilot flow from the cargo handling valve 20 cannot be secured and the cargo handling operation becomes impossible. Generation | occurrence | production is prevented, the pilot flow volume from the cargo handling operation valve 20 is ensured reliably, and stable cargo handling operation is attained.

  (F) The back pressure valve 6 is connected in parallel with the damper orifice 55 for introducing the feedback pressure, and prevents the hydraulic oil from flowing into the other end surface of the valve spool 50, while operating from the other end surface of the valve spool 50. Since the check valve 56 that allows oil to flow out is provided, the movement of the valve spool 50 toward the valve opening side is gradually opened due to the restriction of the damping orifice 55, and the movement of the valve spool 50 toward the valve closing side is performed. The valve can be moved quickly without any restrictions. For this reason, since the opening operation of the back pressure valve 6 can be operated more slowly, the back pressure does not rapidly decrease, and the catching of the steering operation when the cargo handling is OFF can be improved more reliably.

(Second Embodiment)
FIG. 7 is a hydraulic circuit diagram applied to a forklift showing a second embodiment of an industrial vehicle hydraulic device to which the present invention is applied. In the present embodiment, a configuration in which the back pressure valve is connected to the EF passage downstream of the priority flow control valve is added to the first embodiment. The same devices as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted or simplified.

  In FIG. 7, the hydraulic apparatus for an industrial vehicle according to the present embodiment is provided with a return passage 11 so as to communicate between the EF passage 15 downstream of the EF port P3 of the priority flow control valve 5 and the tank 13. The back pressure valve 6 is arranged in the front. As in the first embodiment, the steering pilot pressure and the cargo handling pilot pressure are selected and introduced into the spring chamber 52 of the back pressure valve 6 while the pressure in the EF passage 15 is attached to the damper chamber 53 with a check valve 56. It introduce | transduces through the damper orifice 55 of this. Other configurations are the same as those in the first embodiment.

  In the present embodiment, the total flow rate of the hydraulic oil discharged from the hydraulic pump 2 flows into the priority flow rate control valve 5. In the back pressure valve 6, when neither steering operation nor cargo handling operation is performed, pilot pressure is not introduced into the spring chamber 52, so that a set pressure set only by the spring 54 is generated in the damper chamber 53 and the EF passage 15. The valve spool 50 is moved to adjust the valve opening.

  The priority flow rate control valve 5 is prevented from flowing hydraulic oil into the power steering device 3 and the cargo handling operation valve 20 and has a lowest load value because no steering pilot pressure is generated. It is located on the A position side (large EF port) by the pressure of 43. And it is stable in a state where the opening amount of the EF port P3 on the cargo handling valve 20 side is slightly increased and the opening amount of the PS port P2 on the power steering device 3 side is decreased.

  Therefore, a small amount of hydraulic oil supplied from the hydraulic pump 2 is returned to the tank 13 via the PS port P2, the load signal line 36 and the load signal port P30 of the power steering device 3, and the remaining total amount. Is returned to the tank 13 via the EF port P 3, the EF passage 15, the return passage 11 and the back pressure valve 6.

  When the steering operation is started from this state, a steering pilot pressure corresponding to the steering speed and the steering load is generated from the load signal port P30 of the power steering device 3, and the steering pilot pressure is passed through the steering pilot passage 37 and the shuttle valve 17. Then, the pressure is introduced into the spring chamber 52 of the back pressure valve 6 and the set pressure of the back pressure valve 6 is increased. As the set pressure of the back pressure valve 6 increases, the return passage 11 is throttled by the movement of the valve spool 50 in the valve closing direction, and the pressures of the supply passage 10 from the EF passage 15, the EF port P3, and the hydraulic pump 2 are increased. At the same time, the pressure in the PS port P2 and the PS passage 14 also increases.

  The pressure increase in the PS passage 14 of the priority flow control valve 5 increases the amount of hydraulic fluid passing through the control orifices 36A and 36B of the load signal line 36. For this reason, the pressure of the spring chamber 42 of the priority flow control valve 5 is suddenly increased, and the valve spool 40 is suddenly moved in the direction of increasing the opening amount of the PS port P2 (B position side). Therefore, a sufficient power steering flow rate is supplied to the power steering device 3, and the catch at the start of the steering operation can be improved.

  When the cargo handling operation valve 20 is neutral, most of the flow rate supplied from the hydraulic pump 2 passes through the priority flow rate control valve 5 and reaches the downstream back pressure valve 6, so that hydraulic oil passes through the priority flow rate control valve 5. The pressure loss at the time of cargo handling neutrality is generated by the resistance.

  When the cargo handling operation is started, the lift operation valve 21 or the tilt operation valve 22 is switched from the neutral positions LN and TN to the operation position, and the supplied hydraulic oil is introduced into the target cylinder to perform the cargo handling operation. Is started. At the same time, cargo handling pilot pressure is introduced into the pilot ports P13 and P23 of the lift operating valve 21 or the tilt operating valve 22, and the cargo handling pilot pressure passes through the cargo handling pilot passage 16 and the shuttle valve 17 into the spring chamber 52 of the back pressure valve 6. Introduce. The back pressure valve 6 increases its set pressure and reduces the return discharge amount to the tank 13 when the cargo handling pilot pressure is introduced. For this reason, the hydraulic pressure and hydraulic fluid amount of the hydraulic fluid supplied to the cargo handling operation valve 20 are increased to the priority flow control valve 5.

  The priority flow rate control valve 5 increases the pressing force of the damper chamber 43 by increasing the amount of oil supplied to the cargo handling operation valve 20 and the supply pressure, and the valve spool 40 is moved to the A position side (direction in which the spring 44 is contracted). And the flow rate of the hydraulic oil supplied to the cargo handling operation valve 20 of the cargo handling device 4 is increased according to the operation amount of the cargo handling levers 21A and 22A. As a result, hydraulic oil having a flow rate corresponding to the amount of operation of the operated cargo handling levers 21A and 22A is supplied to the hydraulic cylinder of the cargo handling equipment such as the lift cylinder 23 or the tilt cylinder 24 operated from the lift operation valve 21 or the tilt operation valve 22. The cargo handling device 4 is actuated at an operating speed corresponding to the operation amount of the cargo handling levers 21A and 22A.

  When the steering operation is ON and the cargo handling operation is ON, the steering pilot pressure from the steering pilot passage 37 and the pilots P13 and P23 of the lift operation valve 21 or the tilt operation valve 22 and the cargo handling pilot from the cargo handling pilot passage 16 are used. The pressure reaches the shuttle valve 17. The shuttle valve 17 selects the higher pressure of the steering pilot passage 37 or the cargo handling pilot passage 16 and introduces it into the spring chamber 52 of the back pressure valve 6. The back pressure valve 6 is introduced with a handling pilot pressure that is normally higher than the steering pilot pressure, and raises the set pressure to reduce the return discharge amount to the tank 13, so that the priority flow control valve 5 from the hydraulic pump 2 is reduced. The hydraulic pressure of the hydraulic oil supplied to is increased. The priority flow rate control valve 5 increases the power steering pressure of the PS port P2 to 6.3 [MPa], for example, and the cargo handling pressure of the EF port P3 to 15 [MPa], for example, corresponding to the load. ing.

  From this state, when the cargo handling operation is turned OFF, the lift operation valve 21 or the tilt operation valve 22 is returned to the neutral positions LN and TN. By switching to the neutral position LN of the lift operation valve 21 or the tilt operation valve 22 of the cargo handling device 4, the pilot ports P13 and P23 are connected to the drain ports P14 and P24, and the cargo handling pilot pressure is reduced to zero.

  The pilot pressure in the spring chamber 52 of the back pressure valve 6 is switched from the handling pilot pressure (high) to the steering pilot pressure (medium). The back pressure valve 6 operates the valve spool 50 in the valve opening direction to lower the set pressure, but the valve spool 50 operates only slowly in the valve opening direction by the damper orifice 55 provided in the pilot passage to the damper chamber 53. .

  The lift operation valve 21 and the tilt operation valve 22 employ a closed center cargo handling operation valve 20. For this reason, the destination of the hydraulic oil supplied to the cargo handling valve 20 disappears, and the pressure on the cargo handling valve 20 side (EF port P3 side) and the pressure on the power steering device 3 side (PS port P2 side) are reversed. To the relief pressure set by the main relief valve 12 and the relief valve 38 of the cargo handling pilot passage 37 for a moment, then the pressure on the cargo handling valve 20 side (EF port P3 side) and the power steering device 3 side (PS The pressure on the port P2 side) does not drop rapidly, but slowly decreases.

  The priority flow rate control valve 5 moves to the B position side (PS port P2 large, EF port P3 small) in response to a decrease in supply pressure and supply flow rate, and supply pressure (EF port P3 pressure) to the cargo handling operation valve 20 and By reducing the supply amount, the supply pressure (PS port P2 pressure) and supply amount for the power steering device 3 are secured.

  Then, the pressure is reduced to a pressure set by the steering pilot pressure of the back pressure valve 6, for example, 6.3 [MPa] and converges. The pressure on the loading / unloading operation valve 20 side (EF port P3 side) and the pressure on the power steering device 3 side (PS port P2 side) do not decrease rapidly, but slowly decrease. The catch of steering operation can be improved.

  (G) In this embodiment, the return passage 11 branches from the hydraulic oil supply passage 15 to the cargo handling operation valve 20 via the priority flow control valve 5 and returns the hydraulic oil to the tank 13. A back pressure valve 6 that adjusts the operating pressure of the supply passage 15 by adjusting the amount of hydraulic oil that is recirculated from the supply passage 15 to the tank 13 via the return passage 11 according to the handling pilot pressure. , The effects described in the effects (a) and (e) to (f) in the first embodiment can be achieved.

  (H) Further, by adjusting the amount of hydraulic oil that is disposed in the return passage 11 and recirculates from the supply passage 15 to the tank 13 via the return passage 11 according to the steering pilot pressure, Even in the case of including the back pressure valve 6 that adjusts the operating pressure, the effects described in the effects (A) and (E) to (F) in the first embodiment can be achieved.

  (G) Further, the hydraulic fluid is disposed in the return passage 11 and adjusts the amount of hydraulic oil that is recirculated from the supply passage 15 to the tank 13 via the return passage 11 according to the steering pilot pressure and the cargo handling pilot pressure. Even when the back pressure valve 6 for adjusting the operating pressure of the supply passage 15 is provided, the effects described in the effects (c) and (d) to (f) in the first embodiment can be achieved.

The hydraulic circuit diagram which applied the hydraulic device of the industrial vehicle which shows one Embodiment of this invention to the forklift. 1 is a hydraulic circuit diagram of an all hydraulic power steering device. FIG. The hydraulic circuit diagram explaining the detail of a priority flow control valve. Sectional drawing explaining the structure of a priority flow control valve. The time chart of the pressure change and flow volume change at the time of steering operation start from the state where cargo handling operation and steering operation are not performed. The time chart of the pressure change at the time of sudden stop of cargo handling operation from the state where cargo handling operation and steering operation are performed together. The hydraulic circuit diagram which applied the hydraulic device of the industrial vehicle which shows 2nd Embodiment of this invention to the forklift.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2 Hydraulic pump 3 Power steering apparatus 4 Cargo handling apparatus 5 Priority flow control valve 6 Back pressure valve 10 Supply path 11 Return path 13 Tank 14 PS path 15 EF path 16 Cargo handling pilot path 20 Cargo handling operation valve

Claims (6)

Steering pilot pressure generated at the load signal port of the power steering device by supplying the hydraulic oil discharged from the hydraulic pump with priority to the power steering device and supplying the remaining hydraulic fluid to the cargo handling device. , A priority flow rate control valve for changing the flow rate of hydraulic oil to the power steering device by introducing a load signal line with a control orifice,
The cargo handling device comprising a closed center type switching valve that stops or restricts the return of hydraulic oil supplied to the tank during neutral operation to the tank and outputs the working pressure generated by the cargo handling operation as a cargo handling pilot pressure. A cargo handling valve to be operated;
A return path that branches from the hydraulic oil supply path from the hydraulic pump to the priority flow control valve or the hydraulic oil supply path from the priority flow control valve to the cargo handling valve, and returns the hydraulic oil to the tank;
A back pressure valve that is disposed in the return passage and adjusts the operating pressure of the supply passage by adjusting the amount of hydraulic oil that is recirculated from the supply passage to the tank via the return passage according to the cargo handling pilot pressure; An industrial vehicle hydraulic device comprising: Steering pilot pressure generated at the load signal port of the power steering device by supplying the hydraulic oil discharged from the hydraulic pump with priority to the power steering device and supplying the remaining hydraulic fluid to the cargo handling device. , A priority flow rate control valve for changing the flow rate of hydraulic oil to the power steering device by introducing a load signal line with a control orifice,
A cargo handling operation valve for operating the cargo handling device, comprising a closed center type switching valve that stops or restricts the return of hydraulic oil supplied to the tank at the neutral time;
A return path that branches from the hydraulic oil supply path from the hydraulic pump to the priority flow control valve or the hydraulic oil supply path from the priority flow control valve to the cargo handling valve, and returns the hydraulic oil to the tank;
A back pressure valve that is arranged in the return passage and adjusts the operating pressure of the supply passage by adjusting the amount of hydraulic oil that is recirculated from the supply passage to the tank via the return passage according to the steering pilot pressure; An industrial vehicle hydraulic device comprising: Steering pilot pressure generated at the load signal port of the power steering device by supplying the hydraulic oil discharged from the hydraulic pump with priority to the power steering device and supplying the remaining hydraulic fluid to the cargo handling device. , A priority flow rate control valve for changing the flow rate of hydraulic oil to the power steering device by introducing a load signal line with a control orifice,
The cargo handling device comprising a closed center type switching valve that stops or restricts the return of hydraulic oil supplied to the tank during neutral operation to the tank and outputs the working pressure generated by the cargo handling operation as a cargo handling pilot pressure. A cargo handling valve to be operated;
A return path that branches from the hydraulic oil supply path from the hydraulic pump to the priority flow control valve or the hydraulic oil supply path from the priority flow control valve to the cargo handling valve, and returns the hydraulic oil to the tank;
The operating pressure of the supply passage is adjusted by adjusting the amount of hydraulic oil that is disposed in the return passage and returns to the tank from the supply passage through the return passage according to the steering pilot pressure and the handling pilot pressure. An industrial vehicle hydraulic device comprising a back pressure valve. The back pressure valve is provided on the other side of the valve spool that introduces feedback pressure via a damper orifice into the hydraulic oil supply passage from the hydraulic pump to the priority flow control valve or the hydraulic oil supply passage from the priority flow control valve to the cargo handling operation valve. Opposing to the end face is provided with a spring that sits on one end face of the valve spool to which cargo handling pilot pressure or steering pilot pressure is introduced and biases the valve spool to the other,
The priority flow rate control valve opposes the other end face of the valve spool that introduces feedback pressure to the hydraulic oil supply passage to the power steering device via the damper orifice, and controls the steering pilot pressure via the control orifice of the load signal line. A spring that sits on one end face of the valve spool to be introduced and urges the valve spool to the other,
When the power steering device is not operated, the valve acts on one end of the priority flow control valve against the urging force that acts on one end of the back pressure valve and presses the valve spool against the other. The hydraulic device for an industrial vehicle according to any one of claims 1 to 3, wherein an urging force for pressing the spool to the other is set large.   In the priority flow control valve, even when the valve spool is biased to the other and the valve spool reaches the stroke end, the valve opening relative to the supply passage to the cargo handling valve is opened to a predetermined opening. The industrial vehicle hydraulic device according to any one of claims 1 to 4, wherein the hydraulic device is an industrial vehicle.   The back pressure valve is connected in parallel with a damper orifice that introduces feedback pressure, and prevents hydraulic oil from flowing into the other end face of the valve spool, while allowing hydraulic oil to flow out from the other end face of the valve spool. The industrial vehicle hydraulic device according to any one of claims 1 to 5, further comprising a check valve.

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