JP6424880B2 - Hydraulic drive system for cargo handling vehicle and flow control valve - Google Patents

Description

  The present invention relates to a hydraulic drive system for a cargo handling vehicle and a flow control valve.

  As a hydraulic drive of a cargo handling vehicle, for example, one described in Patent Document 1 is known. The hydraulic drive system described in Patent Document 1 includes an elevating hydraulic cylinder for raising and lowering an elevating object by supply and discharge of hydraulic oil, an elevating operation unit for operating the elevating hydraulic cylinder, and hydraulic oil for the elevating hydraulic cylinder. It is disposed between the hydraulic pump that performs supply and discharge, the motor that drives the hydraulic pump, and the suction port of the hydraulic pump and the bottom chamber of the lifting hydraulic cylinder, and operates based on the operation amount of the lowering operation of the lifting operation unit And a control valve for controlling the flow of oil. The hydraulic drive system also supplies hydraulic fluid pressurized from an accumulator to the hydraulic pump in order to reuse the potential energy of the elevating hydraulic cylinder.

Japanese Patent Application Publication No. 2009-510358

  Here, in the conventional hydraulic drive as described above, the following problems exist. That is, there is a case where the hydraulic oil does not flow to the accumulator because the pressure on the raising and lowering hydraulic cylinder side is low, or the hydraulic oil does not flow to the accumulator because the pressure on the accumulator side is high. As a result, the flow rate of hydraulic fluid from the elevating hydraulic cylinder fluctuates, and there is a problem that the hydraulic cylinder can not be lowered at a desired lowering speed. Therefore, it has been required to be able to efficiently recover the potential energy of the load, and to lower the lifting hydraulic cylinder at a desired lowering speed.

  An object of the present invention is to provide a hydraulic drive system for a cargo handling vehicle, and a flow control valve, capable of efficiently recovering potential energy of a load and lowering a lifting hydraulic cylinder at a desired lowering speed. It is.

  A hydraulic drive system for a cargo handling vehicle according to one aspect of the present invention comprises: a hydraulic cylinder for raising and lowering an elevating object by supply and discharge of hydraulic oil; an operation unit for operating the hydraulic cylinder; A hydraulic pump for supplying and discharging, a hydraulic circuit connected to the hydraulic cylinder, and a descending oil passage through which hydraulic fluid discharged from the hydraulic cylinder flows, and a descending oil passage are disposed. The control valve for controlling the flow of the hydraulic fluid, the bypass oil passage branched from the descending oil passage at the branch point and conducting the branch point and the tank storing the hydraulic oil, the branch point of the descending oil passage and the hydraulic pressure A regenerative oil passage connected to the suction port of the pump, an accumulator provided on the regenerative oil passage for accumulating hydraulic oil discharged from the hydraulic cylinder, an operation valve, and an accumulator and a tank The flow control valve includes a flow control valve that controls the flow of oil, and the flow control valve controls a bypass flow control valve that controls the bypass flow that is the flow of hydraulic fluid flowing to the tank, and the flow of hydraulic fluid accumulated in the accumulator And an accumulated pressure control valve unit to control.

  A hydraulic drive system for a cargo handling vehicle according to one aspect of the present invention is provided on a regenerative oil path connecting a branch point of a descending oil path and a suction port of a hydraulic pump, and accumulates hydraulic oil discharged from a hydraulic cylinder. It has an accumulator. For such an accumulator, a pressure accumulation flow control valve unit that controls the flow rate of hydraulic oil accumulated in the accumulator is provided between the control valve and the accumulator. In addition, a bypass flow control valve unit is provided between the control valve and the tank for controlling a bypass flow that is a flow of hydraulic fluid flowing to the tank. As described above, the hydraulic drive system is provided with two flow control valve units, ie, an accumulated pressure control valve unit and a bypass flow control valve unit. Therefore, when the accumulator can be accumulated, the hydraulic oil discharged from the elevating hydraulic cylinder can be accumulated to the accumulator through the accumulated flow control valve unit. Thus, the potential energy of the load can be accumulated in the accumulator and can be used at other timings. On the other hand, when the accumulator can not store pressure, the hydraulic fluid discharged from the elevating hydraulic cylinder can be supplied to the tank via the bypass flow control valve. Therefore, it is possible to suppress the fluctuation of the flow rate of the hydraulic oil discharged from the elevating hydraulic cylinder and to lower the hydraulic cylinder at a desired lowering speed. As described above, the potential energy of the load can be efficiently recovered, and the elevating hydraulic cylinder can be lowered at a desired lowering speed. Moreover, since the flow control valve which is one valve functions as two flow control valve parts, flow control can be performed by stable operation.

  Further, in the hydraulic drive system for a cargo handling vehicle according to another aspect of the present invention, the flow rate control valve reciprocates the movable body in the stroke space according to the pressure difference generated when the hydraulic oil passes through the operation valve. The pilot-type flow control valve adjusts the opening degree, and the movable body is provided on one end side in the movement direction and is provided on the other end side in the movement direction and the first enlarged diameter portion closing the stroke space. A second enlarged diameter portion closing the stroke space, and a connection portion separated from the inner wall forming the stroke space and connecting the first enlarged diameter portion and the second enlarged diameter portion; bypass flow rate control The valve unit is connected to at least a bypass oil passage connected to the stroke space, an oil passage connected to the stroke space, and supplying hydraulic oil from the operation valve to the stroke space, and a reciprocating movement of the movable body. , Bypass oil path The accumulated flow rate control valve unit is constituted by at least a regenerative oil passage connected to the stroke space, and is connected to the stroke space, and the stroke space And a first diameter-increased portion that adjusts the opening degree by closing the regenerative oil passage along with the reciprocating movement of the movable body. Thereby, pressure accumulation flow control and bypass flow control can be performed with a simple configuration using one moving body.

  In the hydraulic drive system for a cargo handling vehicle according to another aspect of the present invention, the bypass oil passage is disposed closer to one end in the moving direction than the regenerative oil passage with respect to the stroke space, and the bypass flow control valve portion is It may have a stroke section in which the bypass oil passage is completely closed at the enlarged diameter portion. Thus, by completely closing the bypass oil passage, hydraulic fluid can be supplied only to the accumulator in the pressure accumulation flow control valve portion.

  In the hydraulic drive system for a cargo handling vehicle according to another aspect of the present invention, the flow control valve reciprocates the movable body in the stroke space according to the pressure difference generated when the hydraulic oil passes through the operation valve. A pilot-type flow control valve that adjusts the opening degree. The moving body is provided on one end side in the moving direction to close the stroke space, and the moving body is provided on the other end side in the moving direction. A second enlarged diameter portion closing the space, a connecting portion separated from the inner wall forming the stroke space, and connecting the first enlarged diameter portion and the second enlarged diameter portion, a first enlarged diameter portion and a first enlarged diameter portion A third enlarged diameter portion disposed between the first expanded diameter portion and the second expanded diameter portion in the moving direction, and a bypass flow rate control The valve portion is a straw at least between the first enlarged diameter portion and the third enlarged diameter portion. A bypass side supply which is connected to the stroke space between the bypass oil passage connected to the space and the first enlarged diameter portion and the third enlarged diameter portion and supplies the hydraulic oil to the stroke space from the operation valve side An oil passage and a first enlarged diameter portion that adjusts the opening degree by closing the bypass side supply oil passage along with the reciprocating movement of the movable body, and the pressure accumulation flow control valve portion is at least the second Between the second enlarged diameter portion and the third enlarged diameter portion, and the regenerative oil passage connected to the stroke space between the third enlarged diameter portion and the third enlarged diameter portion. A third diameter-increased portion that adjusts the opening degree by closing the pressure-accumulation-side supply oil passage along with the pressure-accumulation-side supply oil passage that supplies hydraulic fluid to the stroke space from the operation valve side and the reciprocating movement of the movable body. And may be configured. Thereby, pressure accumulation flow control and bypass flow control can be performed with a simple configuration using one moving body.

  In the hydraulic drive system for a cargo handling vehicle according to another aspect of the present invention, the bypass flow control valve portion may have a stroke section in which the bypass oil passage is completely closed at the first enlarged diameter portion. Thus, by completely closing the bypass oil passage, hydraulic fluid can be supplied only to the accumulator in the pressure accumulation flow control valve portion.

  The flow control valve according to one aspect of the present invention operates by adjusting the opening degree by reciprocating the movable body in the stroke space according to the pressure difference generated when the hydraulic fluid passes through the other valve. A pilot flow control valve for controlling the flow rate of oil, the first flow control valve unit controlling the flow rate of hydraulic fluid flowing to the first portion, and the flow rate of hydraulic fluid flowing to the second portion The movable body is provided on one end side in the moving direction to close the stroke space, and the moving body is provided on the other end side in the moving direction to provide the stroke space A second enlarged diameter portion closing the opening, and a connection portion separated from the inner wall forming the stroke space and connecting the first enlarged diameter portion and the second enlarged diameter portion; At least a first oil passage connected to the stroke space and a stroke A supply oil passage for supplying hydraulic oil from another valve to the stroke space, and closing the first oil passage as the movable body reciprocates to adjust the opening degree. The second flow control valve portion is constituted by the enlarged diameter portion, and the second flow path connected to the stroke space at least the second oil passage connected to the stroke space, and the operation from the other valve in the stroke space It is comprised by the supply oil path which supplies oil, and the 1st enlarged diameter part which adjusts an opening degree by closing a 2nd oil path with reciprocation of a mobile.

  By using the flow control valve according to one aspect of the present invention, it is possible to obtain the same operation and effect as the above-described hydraulic drive system for a cargo handling vehicle.

  The flow control valve according to one aspect of the present invention operates by adjusting the opening degree by reciprocating the movable body in the stroke space according to the pressure difference generated when the hydraulic fluid passes through the other valve. A pilot flow control valve for controlling the flow rate of oil, the first flow control valve unit controlling the flow rate of hydraulic fluid flowing to the first portion, and the flow rate of hydraulic fluid flowing to the second portion The movable body is provided on one end side in the moving direction to close the stroke space, and the moving body is provided on the other end side in the moving direction to provide the stroke space A second enlarged diameter portion closing the opening, a connecting portion separated from the inner wall forming the stroke space, and connecting the first enlarged diameter portion and the second enlarged diameter portion, a first enlarged diameter portion and a second enlarged diameter portion Between the first enlarged diameter portion and the second enlarged diameter portion in the moving direction And the first flow control valve portion is connected to the stroke space at least between the first diameter expansion portion and the third diameter expansion portion. Is connected to the stroke space between the first oil passage and the first enlarged diameter portion and the third enlarged diameter portion, and the first hydraulic fluid is supplied from the other valve side to the stroke space. The second flow control valve portion is constituted by an oil supply passage and a first diameter-increased portion that adjusts the opening degree by closing the first oil supply passage along with the reciprocating movement of the movable body. At least between the second expanded diameter portion and the third expanded diameter portion, between the second oil passage connected to the stroke space, and between the second expanded diameter portion and the third expanded diameter portion A second supply oil passage connected to the stroke space and supplying the hydraulic fluid to the stroke space from the other valve side, and closing the second supply oil passage with the reciprocating movement of the movable body It constituted a third diameter section for adjusting the degree of opening by between.

  By using the flow control valve according to one aspect of the present invention, it is possible to obtain the same operation and effect as the above-described hydraulic drive system for a cargo handling vehicle.

  According to the present invention, the potential energy of the load can be efficiently recovered, and the elevating hydraulic cylinder can be lowered at a desired lowering speed.

1 is a side view showing a cargo handling vehicle provided with a hydraulic drive system according to an embodiment of the present invention. FIG. 1 is a hydraulic circuit diagram showing a hydraulic drive system according to an embodiment of the present invention. It is a block diagram which shows the control system of the hydraulic drive shown in FIG. It is the block diagram described in detail about the composition near the regeneration oil way of the hydraulic drive of a cargo handling vehicle. It is sectional drawing which shows the detailed structure of a flow control valve. It is sectional drawing which shows the detailed structure of a flow control valve. It is sectional drawing which shows the detailed structure of a flow control valve. It is sectional drawing which shows the detailed structure of a flow control valve. It is sectional drawing which shows the detailed structure of the flow control valve concerning a modification. It is a graph which shows an example of the waveform of the various parameters of the hydraulic drive of a cargo handling vehicle. It is a graph which shows an example of the waveform of the various parameters of the hydraulic drive of a cargo handling vehicle. It is a graph which shows an example of the waveform of the various parameters of the hydraulic drive of a cargo handling vehicle.

  BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the hydraulic drive system for a cargo handling vehicle according to the present invention will be described in detail below with reference to the drawings. In the drawings, the same or equivalent elements will be denoted by the same reference symbols, without redundant description.

  FIG. 1 is a side view showing a cargo handling vehicle provided with a hydraulic drive system according to an embodiment of the present invention. In the figure, the cargo handling vehicle 1 according to the present embodiment is an engine-type forklift. The cargo handling vehicle 1 includes a vehicle body frame 2 and a mast 3 disposed at the front of the vehicle body frame 2. The mast 3 is composed of a pair of left and right outer masts 3a supported so as to be tiltable to the vehicle body frame 2 and an inner mast 3b which is disposed inside the outer masts 3a and which can be raised and lowered relative to the outer mast 3a. There is.

  On the rear side of the mast 3, a lift cylinder 4 as a lifting hydraulic cylinder is disposed. The tip of the piston rod 4p of the lift cylinder 4 is connected to the upper portion of the inner mast 3b.

  The lift bracket 5 is supported by the inner mast 3b so as to be able to move up and down. The lift bracket 5 is provided with a fork (lifting and lowering object) 6 for loading a load. A chain wheel 7 is provided on the upper part of the inner mast 3 b, and a chain 8 is hooked on the chain wheel 7. One end of the chain 8 is connected to the lift cylinder 4, and the other end of the chain 8 is connected to the lift bracket 5. When the lift cylinder 4 is expanded and contracted, the fork 6 moves up and down together with the lift bracket 5 via the chain 8.

  Tilt cylinders 9 as tilting hydraulic cylinders are respectively supported on the left and right sides of the vehicle body frame 2. The tip of the piston rod 9p of the tilt cylinder 9 is rotatably connected to the substantially central portion in the height direction of the outer mast 3a. When the tilt cylinder 9 is extended and retracted, the mast 3 tilts.

  A driver's cab 10 is provided at the top of the vehicle body frame 2. A lift operation lever (first operation unit) 11 for operating the lift cylinder 4 to move the fork 6 up and down and a tilt for operating the tilt cylinder 9 to tilt the mast 3 at the front of the cab 10 An operating lever 12 is provided.

  Further, a steering 13 for steering is provided at the front of the cab 10. The steering 13 is a hydraulic power steering, and can assist the driver's steering with a PS cylinder 14 (see FIG. 2) as a hydraulic cylinder for power steering (PS).

  The cargo handling vehicle 1 also includes an attachment cylinder 15 (see FIG. 2) as an attachment hydraulic cylinder that operates an attachment (not shown). As an attachment, there are, for example, one for moving the fork 6 left and right, tilting and rotating. Further, in the driver's cab 10, an attachment control lever (not shown) for operating the attachment cylinder 15 to operate the attachment is provided.

  Furthermore, although not shown in the figure, the driver's cab 10 is provided with a direction switch for switching the traveling direction (forward / reverse / neutral) of the cargo handling vehicle 1.

  FIG. 2 is a hydraulic circuit diagram showing a first embodiment of a hydraulic drive system according to the present invention. In the figure, the hydraulic drive device 16 of the present embodiment is a device for driving the lift cylinder 4, the tilt cylinder 9, the attachment cylinder 15 and the PS cylinder 14.

  The hydraulic drive 16 comprises a single hydraulic pump 17 and an engine 18 for driving the hydraulic pump 17. The hydraulic pump 17 has a suction port 17a for sucking in hydraulic fluid and a discharge port 17b for discharging hydraulic fluid. The hydraulic pump 17 is configured to be rotatable in one direction.

  A tank 19 for storing hydraulic oil is connected to a suction port 17 a of the hydraulic pump 17 via a hydraulic pipe 20. The hydraulic piping 20 is provided with a check valve 21 that allows hydraulic fluid to flow only in the direction from the tank 19 to the hydraulic pump 17. The hydraulic pump 17 supplies hydraulic fluid to the lift cylinder 4 when the lift operation lever 11 is lifted.

  The discharge port 17 b of the hydraulic pump 17 and the bottom chamber 4 b of the lift cylinder 4 are connected via a hydraulic pipe 22. The hydraulic piping 22 is provided with an electromagnetic proportional valve 23 for lift lift. The solenoid proportional valve 23 blocks the flow of hydraulic fluid from the hydraulic pump 17 to the bottom chamber 4 b of the lift cylinder 4, and the open position 23 a that allows the hydraulic fluid from the hydraulic pump 17 to flow to the bottom chamber 4 b of the lift cylinder 4. And the closed position 23b.

  The solenoid proportional valve 23 is normally located at the closed position 23b (shown), and an operation signal (lift lift solenoid current command value corresponding to the amount of lift operation of the lift control lever 11) is input to the solenoid operation unit 23c. And switches to the open position 23a. Then, the hydraulic oil is supplied from the hydraulic pump 17 to the bottom chamber 4b of the lift cylinder 4, the lift cylinder 4 is extended, and the fork 6 is lifted accordingly. When the proportional solenoid valve 23 is in the open position 23a, it opens at an opening degree corresponding to the operation signal. Between the solenoid proportional valve 23 and the lift cylinder 4 in the hydraulic piping 22, a check valve 24 is provided that allows hydraulic fluid to flow only in the direction from the solenoid proportional valve 23 to the lift cylinder 4.

  A tilt solenoid proportional valve 26 is connected to a branch point between the hydraulic pump 17 and the solenoid proportional valve 23 in the hydraulic pipeline 22 via the hydraulic pipeline 25. The hydraulic piping 25 is provided with a check valve 27 that allows hydraulic fluid to flow only in the direction from the hydraulic pump 17 to the solenoid proportional valve 26.

  The solenoid proportional valve 26 and the rod chamber 9 a and the bottom chamber 9 b of the tilt cylinder 9 are connected via hydraulic pipes 28 and 29, respectively. The solenoid proportional valve 26 allows the hydraulic oil to flow from the hydraulic pump 17 to the rod chamber 9 a of the tilt cylinder 9, and allows the hydraulic fluid from the hydraulic pump 17 to the bottom chamber 9 b of the tilt cylinder 9 to flow. The open position 26b is switched between the closed position 26c where the hydraulic fluid from the hydraulic pump 17 to the tilt cylinder 9 is shut off.

  The solenoid proportional valve 26 is normally in the closed position 26c (shown), and an operation signal (a tilt solenoid current command value corresponding to the operation amount of the tilt operation of the tilt operation lever 12) is sent to the solenoid operation unit 26d on the open position 26a side. Is input to the open position 26a, and an operation signal (a tilt solenoid current command value according to the amount of operation of the forward tilting operation of the tilt operation lever 12) is input to the solenoid operation unit 26e on the open position 26b side. Then, it switches to the open position 26b. When the solenoid proportional valve 26 is switched to the open position 26a, hydraulic oil is supplied from the hydraulic pump 17 to the rod chamber 9a of the tilt cylinder 9, and the tilt cylinder 9 is contracted, and the mast 3 is inclined accordingly. When the solenoid proportional valve 26 is switched to the open position 26b, hydraulic oil is supplied from the hydraulic pump 17 to the bottom chamber 9b of the tilt cylinder 9, the tilt cylinder 9 is extended, and the mast 3 is inclined accordingly. When the proportional solenoid valve 26 is in the open position 26a, 26b, it opens at an opening degree corresponding to the operation signal.

  An electromagnetic proportional valve 31 for attachment is connected to the hydraulic pipe 25 on the upstream side of the check valve 27 via the hydraulic pipe 30. The hydraulic piping 30 is provided with a check valve 32 which allows hydraulic fluid to flow only in the direction from the hydraulic pump 17 to the solenoid proportional valve 31.

  The solenoid proportional valve 31 and the rod chamber 15 a and the bottom chamber 15 b of the attachment cylinder 15 are connected via hydraulic pipes 33 and 34, respectively. The solenoid proportional valve 31 allows the flow of hydraulic fluid from the hydraulic pump 17 to the bottom chamber 15 b of the attachment cylinder 15, and the open position 31 a that allows the hydraulic fluid to flow from the hydraulic pump 17 to the rod chamber 15 a of the attachment cylinder 15. It switches between the open position 31b to be closed and the closed position 31c to block the flow of hydraulic fluid from the hydraulic pump 17 to the attachment cylinder 15.

  The solenoid proportional valve 31 is normally in the closed position 31c (shown), and an operation signal is sent to the solenoid operation unit 31d on the open position 31a side (solenoid current command value for attachment corresponding to the operation amount of one operation of the attachment operation lever) Is input to the open position 31a, and an operation signal (attachment solenoid current command value corresponding to the operation amount of the other operation of the attachment control lever) is input to the solenoid operation unit 31e on the open position 31b side. And switch to the open position 31b. The operation of the attachment cylinder 15 is omitted. When the proportional solenoid valve 31 is at the open position 31a, 31b, it opens at an opening degree corresponding to the operation signal.

  On the upstream side of the check valve 32 in the hydraulic piping 30, an electromagnetic proportional valve 36 for PS is connected via the hydraulic piping 35. The hydraulic piping 35 is provided with a check valve 37 that allows hydraulic fluid to flow only in the direction from the hydraulic pump 17 to the solenoid proportional valve 36.

  The solenoid proportional valve 36 and the first rod chamber 14 a and the second rod chamber 14 b of the PS cylinder 14 are connected via hydraulic pipes 38 and 39 respectively. The solenoid proportional valve 36 has an open position 36 a that allows hydraulic fluid to flow from the hydraulic pump 17 to the first rod chamber 14 a of the PS cylinder 14, and hydraulic fluid from the hydraulic pump 17 to the second rod chamber 14 b of the PS cylinder 14. Between the hydraulic pump 17 and the PS cylinder 14 and the closed position 36c.

  The solenoid proportional valve 36 is normally in the closed position 36c (shown), and an operation signal is sent to the solenoid operation unit 36d on the open position 36a side (PS solenoid current command value according to the operation speed of the left or right side operation of the steering 13) Is input to the open position 36a, and an operation signal (PS solenoid current command value corresponding to the operation speed of the other left / right operation of the steering 13) is input to the solenoid operation unit 36e on the open position 36b side. And switch to the open position 36b. The operation of the PS cylinder 14 is omitted. When the proportional solenoid valve 36 is in the open positions 36a and 36b, it opens at an opening degree corresponding to the operation signal.

  A branch point between the hydraulic pump 17 and the solenoid proportional valve 23 in the hydraulic piping 22 is connected to the tank 19 via the hydraulic piping 40. The hydraulic pressure pipe 40 is provided with an unloading valve 41 and a filter 42. The hydraulic piping 40 and the solenoid proportional valves 26, 31, 36 are connected via hydraulic piping 43-45. Further, the solenoid proportional valves 23, 26, 31, 36 are connected to the hydraulic piping 40 via the hydraulic piping 46.

  The suction port 17 a of the hydraulic pump 17 and the bottom chamber 4 b of the lift cylinder 4 are connected via a hydraulic pipe (falling oil passage) 47. The hydraulic piping 47 is provided with an operation valve 48 for lowering the lift. The control valve 48 switches between an open position 48a which permits the flow of hydraulic fluid from the bottom chamber 4b of the lift cylinder 4 and a closed position 48b which blocks the flow of hydraulic fluid from the bottom chamber 4b of the lift cylinder 4 Be

  When the operation valve 48 is normally in the closed position 48 b (shown) and the operation signal (lift lowering solenoid current command value corresponding to the amount of operation for lowering the lift operation lever 11) is input to the solenoid operation unit 48 c , Switch to the open position 48a. Then, the fork 6 is lowered by the weight of the fork 6 and the lift cylinder 4 is contracted accordingly, and the hydraulic fluid flows out from the bottom chamber 4 b of the lift cylinder 4. When the operation valve 48 is at the open position 48a, the operation valve 48 opens at an opening degree corresponding to the operation signal.

  A branch point between the hydraulic pump 17 and the operation valve 48 in the hydraulic piping 47 is connected to the tank 19 via a bypass oil passage 49. The bypass oil passage 49 is provided with a flow control valve 50 including a bypass flow control valve unit. The flow control valve 50 is a flow control valve with a pressure compensation function. The detailed configuration of the flow control valve 50 will be described later. In the bypass oil passage 49, a filter 54 is provided.

  An accumulator 80, a pressure release control valve 82, and a check valve 83 are provided on the regenerative oil passage 47a of the hydraulic piping 47, which is an oil passage closer to the hydraulic pump 17 than the branch point. A detailed description of these components is provided below with reference to FIG.

  Among the cylinders described above, the tilt cylinder 9, the attachment cylinder 15, and the PS cylinder 14 that perform operations different from the lift cylinder (first hydraulic cylinder) 4 by the supply and discharge of hydraulic oil are collectively referred to as "second hydraulic cylinder 70 It may be called "." In addition, the tilt operation lever 12, the steering 13, and the attachment operation lever, which are levers for operating the second hydraulic cylinder 70, may be collectively referred to as "second operation portion 73".

  FIG. 3 is a block diagram showing a control system of the hydraulic drive device 16. In the figure, the hydraulic drive 16 detects the amount of operation of the lift operation lever 11, and the amount of operation of the tilt operation lever (the operation amount detection unit) 55 and the amount of operation of the tilt operation lever A sensor 56, an attachment operation lever operation amount sensor 57 for detecting an operation amount of an attachment operation lever (not shown), a steering operation speed sensor 58 for detecting an operation speed of the steering 13, and a controller 60. .

  The block diagram which described in detail about the structure of regeneration oil path 47a vicinity of the hydraulic drive 16 of the cargo handling vehicle 1 in FIG. 4 is shown. As described above, in the hydraulic piping 47, the operation valve 48 is provided closer to the lift cylinder 4 than the branch point. A flow control valve 50 is provided in the bypass oil passage 49 and the regeneration oil passage 47 a that communicate the branch point with the tank 19. An accumulator 80 is provided on the regenerative oil passage 47a, a pressure release control valve 82 is provided on the hydraulic pump 17 side of the accumulator 80, and a check valve 83 is provided between the accumulator 80 and a branch point. .

  In the present embodiment, the pressure before and after the operation valve 48 is used as the pilot pressure of the flow control valve 50. As described above, the operating valve 48 has an opening degree corresponding to the amount of operation of the lift operating lever 11 by the operator. Therefore, the differential pressure generated by the operation valve 48 per flow rate of the hydraulic oil becomes a value corresponding to the operation amount of the lift operation lever 11, and becomes smaller as the lever operation amount is larger. The flow rate control valve 50 includes a bypass flow rate control valve unit 50A that controls a bypass flow rate, which is a flow rate of hydraulic fluid flowing to the tank 19, and an accumulated pressure flow control valve unit 50B that controls the flow rate of hydraulic fluid accumulated in the accumulator 80. Equipped with As described above, the flow rate control valve 50 is provided with a function as a bypass flow rate control valve and a function as an accumulated pressure flow control valve simultaneously while being one valve. The flow control valve 50 is a pilot flow control valve that adjusts the opening degree according to the pressure difference generated when the hydraulic fluid passes through the operation valve 48.

  As described above, the bypass flow control valve unit 50A functions as a pilot flow control valve that adjusts the opening degree according to the differential pressure generated when the hydraulic fluid passes through the operation valve 48. That is, the bypass flow control valve unit 50A receives the pressure before and after the operation valve 48 as the pilot pressure, and adjusts the flow rate of the bypass circuit so that the differential pressure generated before and after the operation valve 48 becomes constant. Such differential pressure is called "control differential pressure". When the opening degree of the operation valve 48 is small, the control differential pressure is reached with a small flow rate, and the bypass flow control valve unit 50A controls the bypass flow rate so that the flow rate does not increase further. When the opening degree of the operation valve 48 is large, the control differential pressure can not be reached unless the hydraulic oil having a sufficiently large flow rate flows. Therefore, a sufficiently large flow rate of hydraulic oil flows through the bypass flow control valve unit 50A. That is, the flow rate which the bypass flow control valve unit 50A can flow increases in accordance with the lever operation amount. Thus, the flow rate of the hydraulic oil which can be flowed by the flow control valve is referred to as "control flow rate". The main function of the bypass flow control valve unit 50A is to bypass to the tank 19 side when the hydraulic oil does not flow to the accumulator 80, such as when the load is light or when the accumulator 80 becomes full. This makes it possible to obtain the desired lowering speed of the lift cylinder 4.

  Similar to the bypass flow control valve unit 50A, the pressure accumulation flow control valve unit 50B functions as a pilot flow control valve that adjusts the opening degree according to the differential pressure generated when the hydraulic fluid passes through the operation valve 48. That is, the pressure accumulation flow control valve unit 50B inputs the pressure before and after the operation valve 48 as a pilot pressure, and adjusts the flow rate of the regenerative oil passage 47a so that the differential pressure generated before and after the operation valve 48 becomes constant. The control flow rate of the pressure accumulation flow control valve unit 50B increases in accordance with the lever operation amount. Here, the flow rate control valve 50 has a stroke section in which only the pressure accumulation flow control valve unit 50B is opened with the bypass flow control valve unit 50A completely closed (details will be described later). Therefore, all the hydraulic fluid from the lift cylinder 4 can be accumulated in the accumulator 80 until the accumulator 80 is full. Therefore, energy can be stored in the accumulator 80 with high efficiency. The main function of the pressure accumulation flow control valve unit 50B is to reduce the opening degree of the load to obtain a desired lowering speed of the lift cylinder 4 when the load is heavy and an excess flow rate flows to the accumulator 80.

  The flow rate control valve 50 has an open position 50a that permits the flow of hydraulic fluid to the regenerative oil passage 47a and the bypass fluid passage 49, and a closed position 50b that blocks the flow of hydraulic fluid to the regenerative fluid passage 47a and the bypass fluid passage 49. And the throttle position 50c for adjusting the flow rate of the hydraulic fluid to the bypass oil passage 49 and the throttle position 50g for adjusting the flow rate of the hydraulic fluid to the regenerative oil passage 47a. The pilot operation portion on the closed position 50 b side of the flow control valve 50 and the upstream side (front side) of the operation valve 48 are connected via a pilot flow passage 51. The pilot operation portion on the side of the open position 50 a of the flow control valve 50 and the downstream side (rear side) of the operation valve 48 are connected via a bypass flow passage 52. The flow control valve 50 opens at an opening degree corresponding to the pressure difference before and after the operation valve 48. Specifically, the flow control valve 50 is normally in the open position (shown). Then, as the pressure difference before and after the operation valve 48 increases, the opening degree of the bypass flow control valve unit 50A or the pressure accumulation flow control valve unit 50B decreases.

  The accumulator 80 is a device for accumulating hydraulic oil. Further, the accumulator 80 accumulates the hydraulic oil flowing from the lift cylinder 4 side and releases the hydraulic oil to the hydraulic pump 17 side. The accumulator 80 is internally filled with gas, and as the hydraulic oil is stored, the gas is compressed to increase the internal pressure. Here, when regeneration is performed even when the load is light, it is necessary to set a low gas pressure so that low pressure hydraulic oil can be received. However, if such a setting is made, an excess flow of hydraulic oil will flow to the accumulator 80 if the load is heavy enough. Therefore, in order to suppress the lowering speed of the lift cylinder 4 from becoming excessive, the opening degree of the pressure accumulation flow control valve unit 50B is narrowed, the pressure loss becomes large, and the efficiency is lowered. Therefore, it is preferable to adjust the gas pressure to be filled so as to be most efficient in accordance with the load amount handled by the operator. Preferably, the volume of the accumulator 80 is sufficiently large to receive all the hydraulic fluid discharged from the lift cylinder 4. However, even if the accumulator 80 can not be enlarged due to physical constraints, the hydraulic oil that has become unacceptable can be discharged to the tank 19 via the bypass flow control valve unit 50A, so that the operation is Problem does not occur.

  The check valve 83 is a device that shuts off the flow of hydraulic oil from the accumulator 80 side and allows the flow of hydraulic oil from the branch point side. Therefore, the flow of hydraulic fluid from the lift cylinder 4 to the accumulator 80 is permitted. On the other hand, the flow of hydraulic oil from the accumulator 80 to the lift cylinder 4 is shut off.

  The pressure release control valve 82 releases the hydraulic oil accumulated in the accumulator 80 to the hydraulic pump 17 side. The pressure release control valve 82 shuts off the circuit when the lift cylinder 4 is lowered. On the other hand, when the lift cylinder 4 is raised or the operation of the second hydraulic cylinder 70 is performed, the pressure release control valve 82 conducts the circuit and guides the pressurized fluid of the accumulator 80 to the hydraulic pump 17. The hydraulic pump 17 can be rotated by the pressurized fluid, so that the torque of a power source such as an engine can be reduced and the fuel consumption rate can be reduced. Further, the timing of utilizing the energy stored in the accumulator 80 is considered not only during operation of the second hydraulic cylinder 70 but also during travel, so the switching timing of the pressure release control valve 82 is particularly limited. It is not a thing.

  Specifically, the pressure release control valve 82 is switched between an open position 82a that allows the hydraulic fluid to flow from the accumulator 80 to the suction port 17a of the hydraulic pump 17 and a closed position 82b that blocks the flow. The pressure release control valve 82 is normally in the closed position 82b (shown), and when an operation signal (for example, a solenoid current command value corresponding to the operation amount of the second operation unit 73) is input to the solenoid operation unit 82c. , Switch to the open position 82a. Then, the hydraulic oil flows out of the accumulator 80. When the pressure release control valve 82 is at the open position 48a, the pressure release control valve 82 opens at an opening degree corresponding to the operation signal.

  Next, the detailed configuration of the flow control valve 50 will be described with reference to FIGS. 5 to 8. 5 to 8 are cross-sectional views showing the detailed configuration of the flow control valve 50. As shown in FIG. 5 to 7 show the order of the operation of the flow control valve 50 when the load amount of load on the lift cylinder 4 is heavy. FIG. 8 shows the order of operation of the flow control valve 50 when the load amount on the lift cylinder 4 is light.

  As shown in FIG. 5, the flow control valve 50 includes a spool (moving body) 90 disposed in the stroke space 50 f and reciprocating in the space, and a spring 93 for pressing the spool 90. . The spool 90 is provided with an enlarged diameter portion 91 provided at one end side to close the stroke space 50f, and an enlarged diameter portion 92 provided at the other end side so as to close the stroke space 50f. And a connecting portion 96 connecting the enlarged diameter portions 91 and 92 with each other and having a smaller diameter than the enlarged diameter portions 91 and 92. The connection portion 96 is separated from the inner wall forming the stroke space 50 f, and forms a gap with the inner wall. A pilot space 50e connected to the pilot flow passage 51 is formed at a position outside the end of the enlarged diameter portion 91 in the stroke space 50f. The end of the enlarged diameter portion 91 disposed in the pilot space 50e constitutes a pressure receiving surface 91a. At a position outside the end of the enlarged diameter portion 92 in the stroke space 50f, a spring chamber 50d connected to the bypass flow path 52 and in which the spring 93 is disposed is formed. The end of the enlarged diameter portion 92 disposed in the spring chamber 50d constitutes a pressure receiving surface 92a.

  An oil passage 47b of the hydraulic piping 47 on the side of the operation valve 48 is connected to the stroke space 50f. The oil passage 47 b functions as an oil passage for supplying the hydraulic oil from the operation valve 48 between the enlarged diameter portions 91 and 92 in the stroke space 50 f. A bypass oil passage 49 directed to the tank 19 is connected to the stroke space 50f on the opposite side to the oil passage 47b, and a regenerative oil passage 47a directed to the accumulator 80 is connected. The bypass oil passage 49 is disposed closer to one end side (the enlarged diameter portion 91 side) in the moving direction of the spool 90 than the regenerative oil passage 47a. In addition, since the hydraulic oil from the operation valve 48 is branched by the flow control valve 50, the flow control valve 50 functions as a branch point between the hydraulic piping 47 and the bypass oil passage 49.

  Among the components of the flow control valve 50, the bypass flow control valve unit 50A is connected to the spool 90 including the enlarged diameter portions 91 and 92 and the connection portion 96, the spring 93, and the stroke space 50f. An oil passage 47b, a bypass oil passage 49 connected to the stroke space 50f, a bypass passage 52 connected to the spring chamber 50d, and a pilot passage 51 connected to the pilot space 50e. Further, among the components of the flow control valve 50, the pressure accumulation flow control valve unit 50B includes a spool 90 having enlarged diameter portions 91 and 92 and a connection portion 96, a spring 93, and an oil passage 47b connected to the stroke space 50f. , A regenerative oil passage 47a connected to the stroke space 50f, a bypass passage 52 connected to the spring chamber 50d, and a pilot passage 51 connected to the pilot space 50e. As described above, the bypass flow control valve unit 50A and the pressure accumulation flow control valve unit 50B have configurations other than the bypass oil passage 49 and the regeneration oil passage 47a as common components.

  The oil passage 47 b is disposed at a position corresponding to the connection portion 96, and is disposed at a position at which the enlarged diameter portions 91 and 92 are small regardless of the reciprocation of the spool 90. The bypass oil passage 49 is disposed at a position where the amount of closure of the enlarged diameter portion 91 can be adjusted by the reciprocating movement (displacement) of the spool 90. That is, the enlarged diameter portion 91 adjusts the opening degree by closing the bypass oil passage 49 as the spool 90 reciprocates. In particular, the bypass oil passage 49 is disposed at a position where it can be completely blocked by the enlarged diameter portion 91 in the process of the reciprocating operation of the spool 90. Thus, the bypass flow control valve unit 50A has a stroke section in which the bypass oil passage 49 is completely closed by the enlarged diameter portion 91. The stroke section in which the bypass oil passage 49 is completely closed in the enlarged diameter portion 91 is a section in which the bypass oil passage 49 is completely closed in the enlarged diameter portion 91 among the movement sections in which the spool 90 moves. It is. In the following description, the “stroke section” in the predetermined state is a section in which the predetermined state is maintained among the movement sections in which the spool 90 moves. The bypass flow control valve unit 50A has a stroke section in which the bypass oil passage 49 is partially closed by the enlarged diameter portion 91, and a stroke section in which the bypass oil passage 49 is completely opened.

  The regenerative oil passage 47 a is disposed at a position where the amount of closure of the large diameter portion 91 can be adjusted by the reciprocation (displacement) of the spool 90. That is, the enlarged diameter portion 91 adjusts the opening degree by closing the regenerative oil passage 47 a as the spool 90 reciprocates. In particular, in the process of reciprocating operation of the spool 90, the regenerative oil passage 47a can be completely opened at a position where the bypass oil passage 49 is completely blocked by the enlarged diameter portion 91, and partially enlarged. It is disposed at a position where it can be closed by the part 91. As described above, the pressure accumulation flow control valve unit 50B has a stroke section in which the regenerative oil passage 47a is partially closed by the enlarged diameter portion 91, and a stroke section in which the regenerative oil passage 47a is completely opened.

  Next, with reference to FIGS. 5 to 7, the operation of the flow control valve 50 in the case where the load amount of load on the lift cylinder 4 is heavy will be described. First, immediately after the start of lowering of the lift cylinder 4, as shown in FIG. 5A, the spool 90 is disposed closest to the pilot flow passage 51, and the pilot space 50e has disappeared. In this state, the bypass oil passage 49 and the regeneration oil passage 47a are completely open to the stroke space 50f. The oil passage 47b, which is the inlet of the hydraulic oil, is in a high pressure state, and the bypass oil passage 49 and the regeneration oil passage 47a are in a low pressure state. Therefore, the accumulated flow rate and the bypass flow rate are both excessive. Therefore, the spool 90 moves toward the spring chamber 50d in order to make the pilot pressure constant. By moving the spool 90, the bypass oil passage 49 is partially closed at the enlarged diameter portion 91, as shown in FIG. 5 (b). As a result, although the bypass flow rate decreases, the spool 90 further moves because the accumulated pressure flow rate remains excessive. Accordingly, as shown in FIG. 6A, the enlarged diameter portion 91 completely blocks the bypass oil passage 49. The spool 90 further moves to the spring chamber 50d because the accumulated pressure flow rate is excessive even in this state. As a result, as shown in FIG. 6 (b), the regenerative oil passage 47a is narrowed to decrease the accumulated pressure flow, whereby the accumulated pressure flow becomes an appropriate flow rate.

  Next, when a sufficient amount of hydraulic oil is accumulated in the accumulator 80, the pressure of the accumulator 80 is increased, whereby the accumulated flow rate decreases from the state shown in FIG. 7A. As a result, as shown in FIG. 7B, the spool 90 is pushed by the spring 93 and moves toward the pilot space 50e. As a result, the regenerative oil passage 47a is gradually released from the enlarged diameter portion 91, and the accumulated pressure flow rate is increased. When the pressure accumulation to the accumulator 80 is completed, the accumulated pressure flow rate becomes zero, so the spool 90 moves toward the pilot space 50e to open the bypass oil passage 49 as shown in FIG. Can be controlled to an appropriate flow rate.

  Next, with reference to FIG. 8, the operation of the flow control valve 50 when the product load amount at the lift cylinder 4 is light will be described. First, the pressure of the oil passage 47b, which is the inlet of the hydraulic oil, remains low because the load amount of the load is light. Therefore, as shown to Fig.8 (a), a pressure accumulation flow becomes zero. On the other hand, since the cylinder flow rate is excessive, the spool 90 moves to the spring chamber 50d side. As a result, as shown in FIG. 8B, the bypass oil passage 49 is narrowed at the enlarged diameter portion 91, whereby the bypass flow rate can be appropriately controlled.

  Next, with reference to FIGS. 10 to 12, examples of waveforms of respective parameters of the hydraulic drive 16 are shown. As shown in FIG. 10 (a), the inlet pressure of the accumulator (Acc) rises as the hydraulic oil is accumulated, and becomes constant after full. On the other hand, the pressure (cylinder bottom pressure) of the bottom chamber 4b of the lift cylinder 4 and the branch point of the hydraulic pipe 47 rapidly increase with the start of operation and become constant at a predetermined pressure. The difference between the pressure at the inlet of the accumulator and the pressure at the branch point is the pressure that has been throttled by the pressure accumulation flow control valve unit 50B and converted to heat for flow adjustment. When the pressure at the branch point and the inlet pressure of the accumulator 80 become equal, the hydraulic fluid does not flow to the pressure accumulation side, and the bypass flow control valve 50A is used to compensate for the lack of the cylinder flow path corresponding to the desired descent speed. The hydraulic oil flows to the tank 19 side. As shown in FIG. 10 (b), the variation of the cylinder flow rate is small and kept approximately constant at the switching timing (near 4 seconds). From this point, stable operation of the lift cylinder 4 can be confirmed.

  As shown in FIG. 11 (a), the integrated value of the cylinder flow rate monotonously increases, while the integrated value of the flow rate to the accumulator 80 monotonously increases until full, and increases after full Will stop. As shown in FIG. 11 (b), the pressure accumulation efficiency to the accumulator 80 (except for the portion that rises sharply in the initial stage) increases as the accumulated pressure amount increases, and becomes approximately 0 after being full. As shown in FIG. 12 (a), the electric power calculated by multiplying the flow rate by the pressure becomes substantially constant on the cylinder bottom side, and increases on the inlet side of the accumulator 80 as the accumulated pressure increases and becomes full. After that, it will be approximately 0. The amount of power on the cylinder bottom side monotonously increases, and the inlet side of the accumulator 80 monotonously increases and stops increasing after being full.

  Next, the operation and effects of the hydraulic drive device 16 of the cargo handling vehicle 1 according to the present embodiment will be described.

  The hydraulic drive unit 16 of the cargo handling vehicle 1 according to the present embodiment is provided on a regenerative oil passage 47 a connecting the branch point of the hydraulic piping 47 and the suction port 17 a of the hydraulic pump 17 and operates from the lift cylinder 4. An accumulator 80 for accumulating oil is provided. A pressure accumulation flow control valve unit 50 B is provided between the accumulator 80 and the operation valve 48 to control the flow rate of the hydraulic fluid accumulated in the accumulator 80 with respect to such an accumulator 80. Further, between the tank 19 and the operation valve 48, a bypass flow control valve unit 50A for controlling a bypass flow that is a flow of hydraulic oil flowing to the tank 19 is provided. As described above, the hydraulic drive system 16 includes two flow control valve units, the pressure accumulation flow control valve unit 50B and the bypass flow control valve unit 50A. Therefore, when the accumulator 80 is capable of accumulating pressure, the hydraulic oil discharged from the lift cylinder 4 for raising and lowering can be accumulated to the accumulator 80 through the accumulated pressure control valve unit 50B. Thus, the potential energy of the load can be accumulated in the accumulator 80 and used at other timings. On the other hand, when the accumulator 80 can not store pressure, hydraulic oil discharged from the lift cylinder 4 for raising and lowering can be supplied to the tank 19 via the bypass flow control valve unit 50A. Therefore, the fluctuation of the flow rate of the hydraulic fluid discharged from the lift cylinder 4 for raising and lowering can be suppressed, and the lift cylinder 4 can be lowered at a desired lowering speed. As described above, the potential energy of the load can be efficiently recovered, and the lift cylinder 4 for raising and lowering can be lowered at a desired lowering speed. In addition, since the flow control valve, which is one valve, functions as two flow control valve parts, for example, abnormal flow pulsation due to resonance, generation of vibration can be suppressed, and flow control can be performed in a stable operation. it can.

  Further, in the hydraulic drive system 16 of the cargo handling vehicle 1, the flow control valve 50 including the bypass flow control valve unit 50A and the accumulated flow control valve unit 50B is operated according to the pressure difference generated when the hydraulic oil passes through the operation valve 48. It is a pilot type flow control valve that adjusts the opening degree. Further, by configuring the flow rate control valve 50 as shown in FIG. 5 and FIG. 9, the hydraulic oil from the lift cylinder 4 can be accumulated in the accumulator 80 via the accumulated pressure flow control valve unit 50B. Also, after the accumulator 80 is full, the hydraulic oil can be directed to the tank 19 via the bypass flow control valve unit 50A. Thus, the cargo energy can be automatically recovered at the timing at which the accumulator 80 can be pressure-accumulated. Also, the two flow rate control valves automatically adjust the flow rate of hydraulic fluid according to the load, oil temperature, and lever operation amount, so that the lift cylinder 4 can be set to the desired lowering speed under all conditions. Can be lowered. Further, the hydraulic drive device 16 can obtain the above-described effect at a low cost with a simple configuration without providing a load sensor, an oil temperature sensor, a hydraulic motor / pump for regeneration only, and the like.

  Further, in the hydraulic drive system 16 of the loading vehicle 1, the flow rate control valve 50 is opened by reciprocating the spool 90 in the stroke space 50f in accordance with the pressure difference generated when the hydraulic fluid passes through the operation valve 48. It is a pilot type flow control valve that adjusts the degree. The spool 90 is provided with an enlarged diameter portion 91 provided on one end side in the movement direction to close the stroke space 50f, an enlarged diameter portion 92 provided on the other end side in the movement direction to close the stroke space 50f, and a stroke space 50f. And a connecting portion 96 which is separated from the inner wall to connect the enlarged diameter portion 91 and the enlarged diameter portion 92. The bypass flow control valve unit 50A is at least a bypass oil passage 49 connected to the stroke space 50f and an oil passage connected to the stroke space 50f to supply the hydraulic oil from the operation valve 48 to the stroke space 50f. A certain oil passage 47 b and an enlarged diameter portion 91 that adjusts the opening degree by closing the bypass oil passage 49 in accordance with the reciprocal movement of the spool 90. The pressure accumulation flow control valve unit 50B is at least a regenerative oil passage 47a connected to the stroke space 50f, and an supply oil passage connected to the stroke space 50f to supply the hydraulic oil from the operation valve 48 to the stroke space 50f. It is comprised by a certain oil path 47b and the enlarged diameter part 91 which adjusts an opening degree by closing the regeneration oil path 47a with reciprocation of the spool 90. Thereby, pressure accumulation flow control and bypass flow control can be performed with a simple configuration using one spool 90.

  In the hydraulic drive system 16 of the loading vehicle 1, the bypass oil passage 49 is disposed at one end side in the moving direction with respect to the stroke space 50f, and the bypass flow control valve portion 50A is an enlarged diameter portion 91. It may have a stroke section in which the bypass oil passage 49 is completely closed. Thus, the hydraulic fluid can be supplied only to the accumulator 80 by the pressure accumulation flow control valve unit 50B by completely closing the bypass oil passage 49.

  The flow rate control valve 50 according to the present embodiment reciprocates the spool 90 in the stroke space 50f in accordance with the pressure difference generated when the hydraulic fluid passes through the operation valve (other valve) 48, thereby opening the opening degree. It is a pilot type flow control valve that adjusts and controls the flow rate of hydraulic oil. The flow control valve 50 operates to flow to a bypass flow control valve unit (first flow control valve unit) 50A that controls the flow rate of hydraulic fluid flowing to a tank (first portion) and an accumulator (second portion) 80 And a pressure accumulation flow control valve unit (second flow control valve unit) 50B for controlling the flow rate of oil. The spool 90 is provided with an enlarged diameter portion 91 provided on one end side in the movement direction to close the stroke space 50f, an enlarged diameter portion 92 provided on the other end side in the movement direction to close the stroke space 50f, and a stroke space 50f. And a connecting portion 96 which is separated from the inner wall to connect the enlarged diameter portion 91 and the enlarged diameter portion 92. The bypass flow control valve unit 50A is connected to at least the bypass oil passage (first oil passage) 49 connected to the stroke space 50f and the stroke space 50f, and the hydraulic fluid from the operation valve 48 is connected to the stroke space 50f. And an enlarged diameter portion 91 that adjusts the opening degree by closing the bypass oil passage 49 as the spool 90 reciprocates. The pressure accumulation flow control valve unit 50B is connected to at least the regenerative oil passage (second oil passage) 47a connected to the stroke space 50f and the stroke space 50f, and the hydraulic oil from the operation valve 48 is connected to the stroke space 50f. And an enlarged diameter portion 91 that adjusts the opening degree by closing the regenerative oil passage 47a along with the reciprocating movement of the spool 90.

  By using such a flow control valve 50, it is possible to obtain the same operation and effect as the hydraulic drive 16 of the cargo handling vehicle 1 described above.

  Although the preferred embodiments of the hydraulic drive system for a cargo handling vehicle according to the present invention have been described above, the present invention is not limited to the above embodiments.

  For example, the configuration of the flow control valve is not limited to the configuration of the above-described embodiment, and can be appropriately changed without departing from the spirit of the present invention. For example, as a flow control valve, a configuration as shown in FIG. 9 may be employed. The spool 90 of the flow control valve 150 shown in FIG. 9 is disposed between the enlarged diameter portion 91 and the enlarged diameter portion 92 and at a position separated from the enlarged diameter portion 91 and the enlarged diameter portion 92 in the moving direction. A diameter portion 97 is provided. The bypass oil passage 49 is connected to the stroke space 50 f between the enlarged diameter portion 91 and the enlarged diameter portion 97. The bypass oil passage 49 is disposed at a position corresponding to the connection portion 96, and is disposed at a position at which the enlarged diameter portions 91 and 97 are engaged regardless of the reciprocation of the spool 90. The regenerative oil passage 47a is connected to the stroke space 50f between the enlarged diameter portion 92 and the enlarged diameter portion 97. The regenerative oil passage 47a is disposed at a position corresponding to the connection portion 96, and is disposed at a position at which the enlarged diameter portions 92 and 97 are small regardless of the reciprocation of the spool 90.

Further, in FIG. 9, the oil passage 47b to the accumulator-side oil supply passage 47 ₁ in the branch point, and is branched into a bypass-side oil supply passage 47b _2. Bypass-side supply oil passage 47b ₂ is between the enlarged diameter portion 91 and the enlarged diameter portion 97 is connected to the stroke space 50f, supplies hydraulic fluid from the operating valve 48 side to the stroke space 50f. The bypass side supply oil passage 47 b ₂ is disposed at a position where the amount of closure of the enlarged diameter portion 91 can be adjusted by the reciprocating operation (displacement) of the spool 90. That is, the enlarged diameter portion 91 adjusts the opening degree by closing the bypass side supply oil passage 47 b ₂ as the spool 90 reciprocates. Accumulator side supply oil passage 47 _1, between the enlarged diameter portion 92 and the enlarged diameter portion 97 is connected to the stroke space 50f, supplies hydraulic fluid from the operating valve 48 side to the stroke space 50f. Accumulator side supply oil passage 47 _1, the reciprocating motion of the spool 90 (displacement), the amount covered by the enlarged diameter portion 97 is disposed in adjustable positions. That is, the enlarged diameter portion 97, with the reciprocating movement of the spool 90, adjusting the opening by blocking the accumulator-side oil supply passage 47 _1.

The flow control valve 150 shown in FIG. 9, the bypass flow control valve unit 150A is expanding to adjust the bypass oil passage 49, the bypass-side oil supply passage 47b _2, the opening by blocking the bypass-side supply oil passage 47b ₂ It is comprised by the diameter part 91 and. Also, the accumulator flow rate control valve unit 150B includes a regenerative oil passage 47a, the accumulator-side oil supply passage 47b _1, and the enlarged diameter portion 97 for adjusting the opening by blocking the accumulator-side oil supply passage 47b _1, is constituted by Ru. The bypass flow control valve unit 150A and the pressure accumulation flow control valve unit 150B include the spool 90, the spring 93, the bypass flow passage 52 connected to the spring chamber 50d, and the pilot flow passage 51 connected to the pilot space 50e. , As a common component.

Such flow control valve 150, when the cargo weight in the lift cylinder 4 is heavy, first, by closing the enlarged diameter portion 91 is the complete bypass side supply oil passage 47b _2, enlarged the accumulator-side oil supply passage 47 ₁ While throttling in part 97, the accumulated pressure flow is appropriately controlled. Then, as the accumulator 80 becomes full, the flow control valve 150 appropriately controls the bypass flow rate while squeezing the bypass side supply oil passage 47 b ₂ with the enlarged diameter portion 91. Further, when the accumulated load amount at the lift cylinder 4 is light, the flow control valve 150 appropriately controls the bypass flow while throttling the bypass oil passage 49 with the enlarged diameter portion 91 while the accumulated pressure flow is 0. .

In the hydraulic drive 16 of the cargo handling vehicle 1 according to such a modification, the flow rate control valve 150 reciprocates the spool 90 in the stroke space 50f according to the pressure difference generated when the hydraulic oil passes through the operation valve 48. It is a pilot type flow control valve which adjusts an opening degree by making it do. The movable body is provided with an enlarged diameter portion 91 provided on one end side in the movement direction to close the stroke space 50f, an enlarged diameter portion 92 provided on the other end side in the movement direction to close the stroke space 50f, and a stroke space 50f. Between the enlarged diameter portion 91 and the enlarged diameter portion 92, between the enlarged diameter portion 91 and the enlarged diameter portion 92, and a connection portion 96 which is separated from the inner wall to connect the enlarged diameter portion 91 and the enlarged diameter portion 92; And an enlarged diameter portion 97 disposed at a position spaced apart in the movement direction. The bypass flow control valve portion 150A includes at least a bypass oil passage 49 connected to the stroke space 50f between the enlarged diameter portion 91 and the enlarged diameter portion 97, and between the enlarged diameter portion 91 and the enlarged diameter portion 97. , is connected to the stroke space 50f, and the bypass-side oil supply passage 47b ₂ for supplying working oil from the operating valve 48 side to the stroke space 50f, along with the reciprocating movement of the spool 90 to close the bypass-side supply oil passage 47b ₂ And an enlarged diameter portion 91 for adjusting the opening degree. The pressure accumulation flow control valve unit 150 B includes at least a regenerative oil passage 47 a connected to the stroke space 50 f between the enlarged diameter portion 92 and the enlarged diameter portion 97, and between the enlarged diameter portion 92 and the enlarged diameter portion 97. , it is connected to the stroke space 50f, and accumulator-side oil supply passage 42b ₁ supplies hydraulic fluid from the operating valve 48 side to the stroke space 50f, along with the reciprocating movement of the spool 90 to close the accumulator-side oil supply passage 42b ₁ And an enlarged diameter portion 97 for adjusting the opening degree. Thereby, pressure accumulation flow control and bypass flow control can be performed with a simple configuration using one spool 90.

  In the hydraulic drive system 16 of the loading vehicle 1, the bypass flow control valve portion 150A may have a stroke section in which the bypass oil passage 49 is completely closed by the enlarged diameter portion 91. As a result, by completely closing the bypass oil passage 49, hydraulic fluid can be supplied only to the accumulator 80 by the pressure accumulation flow control valve unit 150B.

The flow rate control valve 150 according to the present embodiment reciprocates the spool 90 in the stroke space 50f in accordance with the pressure difference generated when the hydraulic fluid passes through the operation valve (other valve) 48, thereby opening the opening degree. It is a pilot type flow control valve that adjusts and controls the flow rate of hydraulic oil. Flow control valve 150 operates to flow to bypass flow control valve unit (first flow control valve unit) 150A for controlling the flow rate of hydraulic fluid flowing to the tank (first portion) and accumulator (second portion) 80 And a pressure accumulation flow control valve unit (second flow control valve unit) 150B for controlling the flow rate of oil. The spool 90 is provided with an enlarged diameter portion 91 provided on one end side in the movement direction to close the stroke space 50f, an enlarged diameter portion 92 provided on the other end side in the movement direction to close the stroke space 50f, and a stroke space 50f. Between the enlarged diameter portion 91 and the enlarged diameter portion 92, between the enlarged diameter portion 91 and the enlarged diameter portion 92, and a connection portion 96 which is separated from the inner wall to connect the enlarged diameter portion 91 and the enlarged diameter portion 92; And an enlarged diameter portion 97 disposed at a position spaced apart in the movement direction. The bypass flow control valve portion 150A includes at least a bypass oil passage (first oil passage) 49 connected to the stroke space 50f between the enlarged diameter portion 91 and the enlarged diameter portion 97, an enlarged diameter portion 91, and an enlarged diameter portion 91. The bypass side supply oil passage (first supply oil passage) 47 b _2, which is connected to the stroke space 50 f and supplies the working oil from the operation valve 48 side to the stroke space 50 f, and the spool 90 with the reciprocating movement, and the enlarged diameter portion 91 for adjusting the opening, by by closing the bypass-side oil supply passage 47b _2. The pressure accumulation flow control valve unit 150B includes at least a regenerative oil passage (second oil passage) 47a connected to the stroke space 50f between the enlarged diameter portion 92 and the enlarged diameter portion 97, and the expanded diameter portion 92 and the expanded diameter portion 92. The pressure storage side supply oil passage (second supply oil passage) 42 b _1, which is connected to the stroke space 50 f and supplies the working oil from the operation valve 48 side to the stroke space 50 f, and the spool 90 with the reciprocating movement, and the enlarged diameter portion 97 for adjusting the opening, by by closing the accumulator-side oil supply passage 42b _1.

  By using such a flow control valve 150, it is possible to obtain the same operation and effect as the hydraulic drive 16 of the cargo handling vehicle 1 described above.

  Further, in the above-described embodiment, a tilt cylinder, a PS cylinder, and an attachment cylinder are provided as the second hydraulic cylinder. However, there may be at least one second hydraulic cylinder, and some may be omitted. For example, although the attachment and the power steering are mounted in the above embodiment, the hydraulic drive system of the present invention is also applicable to a forklift which is not mounted with the attachment and the power steering. Further, the hydraulic drive system of the present invention can be applied not only to battery-type forklifts but also to engine-type and battery-type cargo handling vehicles other than forklifts.

  As a control valve that controls the flow of hydraulic fluid based on the lowering operation of the lift control lever and a control valve that controls the flow of hydraulic fluid based on the operation of the second operation unit, an electromagnetic proportional valve has been exemplified. It may be either hydraulic or mechanical.

  DESCRIPTION OF SYMBOLS 1 ... cargo handling vehicle, 4 ... lift cylinder (hydraulic cylinder), 4b ... bottom chamber, 6 ... fork (lifting and lowering object), 11 ... lift operation lever (operation part), 16 ... hydraulic drive, 17 ... hydraulic pump (hydraulic pump (hydraulic pump) 17a: suction port 17b: discharge port 47: hydraulic pipe (falling oil passage) 47a: regenerative oil passage 48: operation valve 49: bypass oil passage 50, 150: flow control valve 50A, 150A ... bypass flow control valve unit, 50B, 150B ... accumulated pressure flow control valve unit, 80 ... accumulator, 90 ... spool (moving body), 91 ... enlarged diameter section (first enlarged diameter section), 92 ... expanded diameter section (first 2) enlarged diameter portion, 96: connection portion, 97: enlarged diameter portion (third enlarged diameter portion).

Claims (7)

A lifting hydraulic cylinder that raises and lowers the lifting object by the supply and discharge of hydraulic oil;
An operating unit for operating the hydraulic cylinder;
A hydraulic pump for supplying and discharging the hydraulic fluid to and from the hydraulic cylinder;
A descending oil passage connected to the hydraulic cylinder through which hydraulic fluid discharged from the hydraulic cylinder flows;
An operation valve disposed in the descending oil passage and controlling a flow of hydraulic fluid discharged from the hydraulic cylinder based on the descending operation of the operation unit;
A bypass oil passage which branches from the descending oil passage at a branch point and which electrically connects the branch point and a tank for storing the hydraulic oil;
A regenerative oil passage connecting the branch point of the descending oil passage and the suction port of the hydraulic pump;
An accumulator, which is provided on the regenerative oil path and accumulates the hydraulic oil discharged from the hydraulic cylinder,
And a flow control valve provided between the operation valve and the accumulator and the tank for controlling the flow rate of the hydraulic fluid.
The flow control valve is
A bypass flow control valve unit that controls a bypass flow rate which is a flow rate of hydraulic oil flowing to the tank;
A hydraulic drive system for a cargo handling vehicle, comprising: an accumulated pressure control valve unit that controls the flow rate of the hydraulic oil accumulated in the accumulator. The flow control valve is a pilot flow control valve that adjusts the opening degree by reciprocating the moving body in the stroke space according to the pressure difference generated when the hydraulic fluid passes through the operation valve. ,
The moving body is
A first enlarged diameter portion provided on one end side in the movement direction to close the stroke space;
A second enlarged diameter portion provided on the other end side in the movement direction to close the stroke space;
A connecting portion separated from the inner wall forming the stroke space and connecting the first enlarged diameter portion and the second enlarged diameter portion;
The bypass flow control valve unit at least
The bypass oil passage connected to the stroke space;
An oil supply passage connected to the stroke space for supplying hydraulic oil from the operation valve to the stroke space;
It is comprised by the said 1st enlarged diameter part which adjusts an opening degree by closing the said bypass oil path with reciprocation of the said mobile body,
The accumulated pressure flow control valve unit at least
The regenerative oil passage connected to the stroke space;
The supply oil passage connected to the stroke space to supply the hydraulic fluid from the operation valve to the stroke space;
The hydraulic drive system for a cargo handling vehicle according to claim 1, wherein the first expanded diameter portion adjusts the opening degree by closing the regenerative oil passage along with the reciprocating movement of the movable body. With respect to the stroke space, the bypass oil passage is disposed closer to the one end side in the movement direction than the regenerative oil passage,
The hydraulic drive system for a cargo handling vehicle according to claim 2, wherein the bypass flow control valve portion has a stroke section in which the bypass oil path is completely closed at the first enlarged diameter portion. The flow control valve is a pilot flow control valve that adjusts the opening degree by reciprocating the moving body in the stroke space according to the pressure difference generated when the hydraulic fluid passes through the operation valve. ,
The moving body is
A first enlarged diameter portion provided on one end side in the movement direction to close the stroke space;
A second enlarged diameter portion provided on the other end side in the movement direction to close the stroke space;
A connecting portion separated from the inner wall forming the stroke space and connecting the first enlarged diameter portion and the second enlarged diameter portion;
A first position between the first enlarged diameter portion and the second enlarged diameter portion, the position being separated from the first expanded diameter portion and the second enlarged diameter portion in the movement direction And 3 diameter enlarged parts,
The bypass flow control valve unit at least
The bypass oil passage connected to the stroke space between the first enlarged diameter portion and the third enlarged diameter portion;
A bypass side supply oil passage connected to the stroke space between the first enlarged diameter portion and the third enlarged diameter portion and supplying the hydraulic fluid to the stroke space from the operation valve side;
It is comprised by the said 1st enlarged diameter part which adjusts an opening degree by obstructing the said bypass side supply oil path with reciprocation of the said mobile body,
The accumulated pressure flow control valve unit at least
The regenerative oil passage connected to the stroke space between the second enlarged diameter portion and the third enlarged diameter portion;
An accumulator side oil supply passage connected to the stroke space between the second enlarged diameter portion and the third enlarged diameter portion and supplying the hydraulic oil to the stroke space from the operation valve side;
The hydraulic drive of a cargo handling vehicle according to claim 1, wherein the third expanded diameter portion adjusts the opening degree by closing the pressure accumulation side supply oil passage along with the reciprocating movement of the movable body. apparatus.   The hydraulic drive system for a cargo handling vehicle according to claim 4, wherein the bypass flow control valve portion has a stroke section in which the bypass oil passage is completely closed at the first enlarged diameter portion. A pilot-type flow control valve that adjusts the opening degree to control the flow rate of the hydraulic fluid by reciprocating the movable body in the stroke space according to the pressure difference generated when the hydraulic fluid passes through another valve. And
A first flow control valve unit for controlling the flow rate of the hydraulic fluid flowing to the first portion;
A second flow control valve unit for controlling the flow rate of the hydraulic fluid flowing to the second portion;
The moving body is
A first enlarged diameter portion provided on one end side in the movement direction to close the stroke space;
A second enlarged diameter portion provided on the other end side in the movement direction to close the stroke space;
A connecting portion separated from the inner wall forming the stroke space and connecting the first enlarged diameter portion and the second enlarged diameter portion;
The first flow control valve unit at least
A first oil passage connected to the stroke space;
An oil supply passage connected to the stroke space to supply the hydraulic fluid from the other valve to the stroke space;
It is comprised by the said 1st enlarged diameter part which adjusts an opening degree by obstructing the said 1st oil path with reciprocation of the said mobile body,
The second flow rate control valve unit at least
A second oil passage connected to the stroke space;
The supply oil passage connected to the stroke space to supply the hydraulic fluid from the other valve to the stroke space;
A flow control valve comprising: the first diameter-increased portion adjusting an opening degree by closing the second oil passage along with the reciprocating movement of the movable body. A pilot-type flow control valve that adjusts the opening degree to control the flow rate of the hydraulic fluid by reciprocating the movable body in the stroke space according to the pressure difference generated when the hydraulic fluid passes through another valve. And
A first flow control valve unit for controlling the flow rate of the hydraulic fluid flowing to the first portion;
A second flow control valve unit for controlling the flow rate of the hydraulic fluid flowing to the second portion;
The moving body is
A first enlarged diameter portion provided on one end side in the movement direction to close the stroke space;
A second enlarged diameter portion provided on the other end side in the movement direction to close the stroke space;
A connecting portion separated from the inner wall forming the stroke space and connecting the first enlarged diameter portion and the second enlarged diameter portion;
A first position between the first enlarged diameter portion and the second enlarged diameter portion, the position being separated from the first expanded diameter portion and the second enlarged diameter portion in the movement direction And 3 diameter enlarged parts,
The first flow control valve unit at least
A first oil passage connected to the stroke space between the first expanded diameter portion and the third expanded diameter portion;
A first supply oil passage connected to the stroke space between the first enlarged diameter portion and the third enlarged diameter portion and supplying the hydraulic oil to the stroke space from the other valve side; ,
It is comprised by the said 1st enlarged diameter part which adjusts an opening degree by obstruct | occluding the said 1st oil supply path with the reciprocation of the said mobile body,
The second flow rate control valve unit at least
A second oil passage connected to the stroke space between the second enlarged diameter portion and the third enlarged diameter portion;
A second supply oil passage connected to the stroke space between the second enlarged diameter portion and the third enlarged diameter portion and supplying the hydraulic fluid to the stroke space from the other valve side; ,
A flow control valve comprising: the third expanded diameter portion adjusting an opening degree by closing the second supply oil passage in accordance with reciprocating movement of the movable body.

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