JP2017095192A - Hydraulic drive unit of cargo handling vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic drive unit of a cargo handling vehicle which can operate the other actuator at a desired speed, and can descend a lifting-material lift at a desired descending speed when a descending operation of a lift hydraulic cylinder and an operation of the other hydraulic cylinder are simultaneously performed.SOLUTION: A bypass flow rate control valve 50 for controlling a flow rate of a working fluid which returns to a tank 19 from a lift operation lever 11 is arranged on hydraulic piping 49. In hydraulic piping 47, a regeneration flow rate control valve 80 for controlling a flow rate of the working fluid flowing to a hydraulic pump motor 17 from the lift operation lever 11 is arranged between a suction port 17a of the hydraulic pump motor 17 and a branch point 91. Since the descending operation and the operation of a hydraulic cylinder are simultaneously performed when a motor rotation number is raised more than that at single descending, the regeneration flow rate control valve 80 controls the flow rate of the working fluid, and an abrupt increase of a fork descending speed can be thereby suppressed.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a hydraulic drive device for a cargo handling vehicle.

  As a hydraulic drive device for a cargo handling vehicle, for example, one described in Patent Document 1 is known. The hydraulic drive device described in Patent Document 1 includes a lifting hydraulic cylinder that lifts and lowers a lifting object by supplying and discharging hydraulic oil, a lifting operation unit for operating the lifting hydraulic cylinder, a lifting hydraulic cylinder, and other actuators. A hydraulic pump that supplies and discharges hydraulic oil to and from the hydraulic cylinder, an electric motor that drives the hydraulic pump, a suction port of the hydraulic pump, and a bottom chamber of the lifting hydraulic cylinder; And a control valve that controls the flow of hydraulic oil based on the operation amount of the lowering operation.

US Pat. No. 5,649,422

  Here, the conventional hydraulic drive apparatus as described above has the following problems. That is, in the hydraulic drive device, there are a case where the lowering operation of the lifting hydraulic cylinder is performed alone and a case where the lowering operation of the lifting hydraulic cylinder and the operation of the hydraulic cylinders related to other actuators are performed simultaneously. In the case where the lowering operation of the lifting hydraulic cylinder and the operation of other hydraulic cylinders are performed at the same time, if the motor speed is controlled so that the other actuators can be operated at a desired speed, the lowering speed of the lifting object is reduced. There was a possibility that it would be faster or slower than the desired speed. Therefore, when the lowering operation of the lifting hydraulic cylinder and the operation of other hydraulic cylinders are performed simultaneously, it is required to control the rotation speed of the electric motor so that the lifting object can be lowered at a desired lowering speed. It was.

  An object of the present invention is to provide a hydraulic drive device for a cargo handling vehicle capable of lowering an ascending / descending object at a desired lowering speed when a lowering operation of a lifting hydraulic cylinder and an operation of another hydraulic cylinder are performed simultaneously. That is.

  A hydraulic drive device for a cargo handling vehicle according to one aspect of the present invention performs a first hydraulic cylinder for raising and lowering a lifted object by supplying and discharging hydraulic oil and an operation different from that of the first hydraulic cylinder by supplying and discharging hydraulic oil. The second hydraulic cylinder, the first operating part for operating the first hydraulic cylinder, the second operating part for operating the second hydraulic cylinder, and the supply of hydraulic oil to the first hydraulic cylinder and the second hydraulic cylinder A hydraulic pump that discharges, an electric motor that is connected to the hydraulic pump and functions as an electric motor or a generator, a tank that stores hydraulic oil, a suction port of the hydraulic pump, and a first hydraulic cylinder are connected to each other; A first hydraulic fluid passage for sending hydraulic fluid from the hydraulic cylinder to the hydraulic pump, a branch point on the first hydraulic fluid passage, and a tank are connected, and the hydraulic fluid from the first hydraulic cylinder is returned to the tank. Second work An oil flow path, a first flow rate control valve disposed on the second hydraulic oil path and controlling the flow rate of the hydraulic oil returning from the first hydraulic cylinder to the tank; and suction of the hydraulic pump in the first hydraulic oil path A second flow rate control valve that is disposed between the opening and the branch point and controls the flow rate of the hydraulic fluid flowing from the first hydraulic cylinder to the hydraulic pump, and a lowering operation by the first operation unit and a second operation unit If the motor rotation speed increases and the flow rate of the hydraulic pump increases compared to when the first operation unit is operated alone, the second flow rate control valve moves from the first hydraulic cylinder to the hydraulic pump. Control to reduce the flow rate of hydraulic oil.

  In the hydraulic drive system for a cargo handling vehicle according to the present invention, the second hydraulic fluid passage is connected via a branch point from the first hydraulic fluid passage for sending hydraulic fluid from the first hydraulic cylinder to the hydraulic pump. . A first flow rate control valve for controlling the flow rate of the hydraulic fluid returning from the first hydraulic cylinder to the tank is disposed on the second hydraulic fluid passage. In the first hydraulic oil flow path, a second flow rate control valve for controlling the flow rate of the hydraulic oil flowing from the first hydraulic cylinder to the hydraulic pump is disposed between the suction port of the hydraulic pump and the branch point. Yes. According to such a configuration, the lowering operation by the first operation unit and the operation of the second operation unit are performed at the same time, so that the motor rotation speed is increased compared with the single operation of the first operation unit, and the flow rate of the hydraulic pump is increased. When it goes up, it can control that a fork lowering speed increases rapidly by controlling so that the 2nd flow control valve may control the flow of hydraulic oil which goes to the hydraulic pump from the 1st hydraulic cylinder. As described above, when the lowering operation of the first hydraulic cylinder for raising and lowering and the operation of the other second hydraulic cylinder are simultaneously performed, the elevator can be lowered at a desired lowering speed.

  In the hydraulic drive system for a cargo handling vehicle according to another aspect of the present invention, the flow rate of the hydraulic fluid that can be controlled by the second flow rate control valve is set to be higher than the flow rate of the hydraulic fluid that can be controlled by the first flow rate control valve. May have been. As a result, with respect to a predetermined lowering operation amount, the lowering speed of the lifting / lowering object is kept constant by controlling the second flow rate control valve, and the lowering speed of the lifting / lowering object is kept constant by the control of the first flow rate control valve. In comparison with the case, the descending speed of the lifted object by the control of the second flow rate control valve can be made higher. In this case, when the motor rotational speed is increased, a transition portion in which the descending speed of the ascending / descending object is partially increased with the motor rotational speed at a portion where the control by the first flow control valve is shifted to the control by the second flow control valve. Can be provided. By such a transition part, it can suppress that it changes suddenly from control by the 1st flow control valve to control by the 2nd flow control valve.

  Further, in the hydraulic drive system for a cargo handling vehicle according to another aspect of the present invention, the first hydraulic fluid passage is disposed between the first hydraulic cylinder and the branch point, and is operated to lower the first operation portion. A proportional valve that opens at an opening according to the amount, and the second flow control valve may control the flow rate of the hydraulic oil based on a pressure difference before and after the proportional valve. Thereby, the 2nd flow control valve can be controlled by the descent speed of the raising / lowering object according to the operation amount of the descent operation of the 1st operation part.

  Further, in the hydraulic drive system for a cargo handling vehicle according to another aspect of the present invention, the first hydraulic fluid passage is disposed between the first hydraulic cylinder and the branch point, and is operated to lower the first operation portion. And a proportional valve that opens at an opening according to the amount, and the first flow control valve may control the flow rate of the hydraulic oil based on a pressure difference before and after the proportional valve. Thereby, the 1st flow control valve can be controlled by the descent speed of the raising / lowering object according to the operation amount of the descent operation of the 1st operation part.

  According to the present invention, when the lowering operation of the lifting hydraulic cylinder and the operation of other hydraulic cylinders are performed simultaneously, the lifting object can be lowered at a desired lowering speed.

It is a side view showing a cargo handling vehicle provided with a hydraulic drive concerning an embodiment of the present invention. 1 is a hydraulic circuit diagram showing a hydraulic drive device according to an embodiment of the present invention. It is a block diagram which shows the control system of the hydraulic drive unit shown in FIG. It is a block block diagram which shows the control system of the hydraulic drive unit shown in FIG. It is a flowchart which shows the control processing procedure performed by the controller shown in FIG. It is a graph which shows the relationship between the descent | fall operation amount and motor rotation speed, and the graph which shows the relationship between a motor rotation speed and cylinder flow volume. It is a figure which shows the timing chart of the motor rotation speed which concerns on each control form. It is a figure which shows the timing chart of the motor rotation speed which concerns on each control form.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of a hydraulic drive device for a cargo handling vehicle according to the invention will be described in detail with reference to the drawings. In the drawings, the same or equivalent elements are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a side view showing a cargo handling vehicle including a hydraulic drive device according to an embodiment of the present invention. In the figure, a cargo handling vehicle 1 according to the present embodiment is a battery-type forklift. The cargo handling vehicle 1 includes a body frame 2 and a mast 3 disposed at a front portion of the body frame 2. The mast 3 includes a pair of left and right outer masts 3a supported to be tiltable on the vehicle body frame 2, and an inner mast 3b which is disposed inside these outer masts 3a and can be moved up and down with respect to the outer mast 3a. Yes.

  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 part of the inner mast 3b.

  A lift bracket 5 is supported on the inner mast 3b so as to be movable up and down. A fork (lifting object) 6 for loading a load is attached to the lift bracket 5. A chain wheel 7 is provided on the upper portion of the inner mast 3b, 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 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 body frame 2. The tip of the piston rod 9p of the tilt cylinder 9 is rotatably connected to the substantially central portion of the outer mast 3a in the height direction. When the tilt cylinder 9 is expanded and contracted, the mast 3 tilts.

  A driver's cab 10 is provided on the upper part of the body frame 2. At the front of the cab 10, there are provided a lift operation lever 11 for operating the lift cylinder 4 to raise and lower the fork 6, and a tilt operation lever 12 for operating the tilt cylinder 9 to tilt the mast 3. It has been.

  A steering wheel 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 by a PS cylinder 14 (see FIG. 2) as a hydraulic cylinder for power steering (PS).

  Further, the cargo handling vehicle 1 includes an attachment cylinder 15 (see FIG. 2) as an attachment hydraulic cylinder for operating an attachment (not shown). As the attachment, for example, there is one that moves, tilts, and rotates the fork 6 left and right. The cab 10 is provided with an attachment operation lever (not shown) for operating the attachment cylinder 15 to operate the attachment.

  Further, although not particularly illustrated, the 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 the hydraulic drive apparatus according to the present invention. In the figure, a hydraulic drive device 16 of the present embodiment is a device that drives a lift cylinder 4, a tilt cylinder 9, an attachment cylinder 15, and a PS cylinder 14.

  The hydraulic drive device 16 includes a single hydraulic pump motor 17 and a single electric motor 18 that drives the hydraulic pump motor 17. The hydraulic pump motor 17 has a suction port 17a for sucking hydraulic oil and a discharge port 17b for discharging hydraulic oil. The hydraulic pump motor 17 is configured to be rotatable in one direction.

  The electric motor 18 functions as an electric motor or a generator. Specifically, when the hydraulic pump motor 17 operates as a hydraulic pump, the electric motor 18 functions as an electric motor, and when the hydraulic pump motor 17 operates as a hydraulic motor, the electric motor 18 functions as a generator. To do. When the electric motor 18 functions as a generator, the electric power generated by the electric motor 18 is stored in a battery (not shown). That is, a regenerative operation is performed.

  A tank 19 for storing hydraulic oil is connected to a suction port 17 a of the hydraulic pump motor 17 via a hydraulic pipe 20. The hydraulic pipe 20 is provided with a check valve 21 for flowing hydraulic oil only in the direction from the tank 19 to the hydraulic pump motor 17. The hydraulic pump motor 17 functions as a pump that supplies hydraulic oil to the lift cylinder 4 when the lift operation lever 11 is raised, and is driven by the hydraulic oil discharged from the lift cylinder 4 when the lift operation lever 11 is lowered. Functions as a hydraulic motor.

  The discharge port 17 b of the hydraulic pump motor 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 lifting the lift. The electromagnetic proportional valve 23 has an open position 23 a that allows the hydraulic oil to flow from the hydraulic pump motor 17 to the bottom chamber 4 b of the lift cylinder 4, and the hydraulic oil flows from the hydraulic pump motor 17 to the bottom chamber 4 b of the lift cylinder 4. Is switched to the closed position 23b that shuts off.

  The electromagnetic proportional valve 23 is normally in a closed position 23b (illustrated), and an operation signal (a lift raising solenoid current command value corresponding to an operation amount of the lifting operation of the lift operation lever 11) is input to the solenoid operating portion 23c. Then, it switches to the open position 23a. Then, hydraulic oil is supplied from the hydraulic pump motor 17 to the bottom chamber 4b of the lift cylinder 4, the lift cylinder 4 extends, and the fork 6 rises accordingly. When the electromagnetic proportional valve 23 is in the open position 23a, the electromagnetic proportional valve 23 is opened at an opening corresponding to the operation signal. A check valve 24 is provided between the electromagnetic proportional valve 23 and the lift cylinder 4 in the hydraulic pipe 22 so that hydraulic fluid flows only in the direction from the electromagnetic proportional valve 23 to the lift cylinder 4.

  An electromagnetic proportional valve 26 for tilt is connected to a branch point between the hydraulic pump motor 17 and the electromagnetic proportional valve 23 in the hydraulic pipe 22 via a hydraulic pipe 25. The hydraulic pipe 25 is provided with a check valve 27 that allows hydraulic oil to flow only in the direction from the hydraulic pump motor 17 to the electromagnetic proportional valve 26.

  The electromagnetic proportional valve 26 and the rod chamber 9a and the bottom chamber 9b of the tilt cylinder 9 are connected via hydraulic pipes 28 and 29, respectively. The electromagnetic proportional valve 26 has an open position 26 a that allows the hydraulic oil to flow from the hydraulic pump motor 17 to the rod chamber 9 a of the tilt cylinder 9, and the hydraulic oil flows from the hydraulic pump motor 17 to the bottom chamber 9 b of the tilt cylinder 9. Is switched between an open position 26b allowing the hydraulic oil and a closed position 26c interrupting the flow of the hydraulic oil from the hydraulic pump motor 17 to the tilt cylinder 9.

  The electromagnetic proportional valve 26 is normally in a closed position 26c (illustrated), and an operation signal (a tilt solenoid current command value corresponding to an operation amount of a tilting operation of the tilt operation lever 12) is sent to a solenoid operation unit 26d on the open position 26a side. ) Is switched to the open position 26a, and an operation signal (tilt solenoid current command value corresponding to the amount of forward tilt operation of the tilt operation lever 12) is input to the solenoid operation portion 26e on the open position 26b side. If it does, it will switch to the open position 26b. When the electromagnetic proportional valve 26 is switched to the open position 26a, hydraulic oil is supplied from the hydraulic pump motor 17 to the rod chamber 9a of the tilt cylinder 9, the tilt cylinder 9 contracts, and the mast 3 tilts backward along with this. When the electromagnetic proportional valve 26 is switched to the open position 26b, hydraulic oil is supplied from the hydraulic pump motor 17 to the bottom chamber 9b of the tilt cylinder 9, the tilt cylinder 9 extends, and the mast 3 tilts forward. When the electromagnetic proportional valve 26 is in the open positions 26a and 26b, the electromagnetic proportional valve 26 is opened at an opening corresponding to the operation signal.

  An attachment electromagnetic proportional valve 31 is connected to the upstream side of the check valve 27 in the hydraulic pipe 25 via a hydraulic pipe 30. The hydraulic pipe 30 is provided with a check valve 32 that circulates hydraulic oil only in the direction from the hydraulic pump motor 17 to the electromagnetic proportional valve 31.

  The electromagnetic proportional valve 31 and the rod chamber 15a and the bottom chamber 15b of the attachment cylinder 15 are connected via hydraulic pipes 33 and 34, respectively. The electromagnetic proportional valve 31 has an open position 31a that allows the hydraulic fluid to flow from the hydraulic pump motor 17 to the rod chamber 15a of the attachment cylinder 15, and the hydraulic fluid to flow from the hydraulic pump motor 17 to the bottom chamber 15b of the attachment cylinder 15. Is switched between an open position 31b that allows the hydraulic oil and a closed position 31c that blocks the flow of hydraulic oil from the hydraulic pump motor 17 to the attachment cylinder 15.

  The electromagnetic proportional valve 31 is normally in a closed position 31c (illustrated), and an operation signal (attachment solenoid current command value corresponding to an operation amount of one side operation of the attachment operation lever) is sent to a solenoid operation unit 31d on the open position 31a side. Is switched 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 operation lever) is input to the solenoid operation portion 31e on the open position 31b side. And switch to the open position 31b. The operation of the attachment cylinder 15 is omitted. Further, when the electromagnetic proportional valve 31 is in the open positions 31a and 31b, the electromagnetic proportional valve 31 is opened at an opening corresponding to the operation signal.

  A PS electromagnetic proportional valve 36 is connected to the upstream side of the check valve 32 in the hydraulic pipe 30 via a hydraulic pipe 35. The hydraulic pipe 35 is provided with a check valve 37 for flowing hydraulic oil only in the direction from the hydraulic pump motor 17 to the electromagnetic proportional valve 36.

  The electromagnetic proportional valve 36 and the first rod chamber 14a and the second rod chamber 14b of the PS cylinder 14 are connected via hydraulic pipes 38 and 39, respectively. The electromagnetic proportional valve 36 has an open position 36a that allows the hydraulic oil to flow from the hydraulic pump motor 17 to the first rod chamber 14a of the PS cylinder 14, and from the hydraulic pump motor 17 to the second rod chamber 14b of the PS cylinder 14. The position is switched between an open position 36 b that allows the hydraulic oil to flow and a closed position 36 c that blocks the hydraulic oil flow from the hydraulic pump motor 17 to the PS cylinder 14.

  The electromagnetic proportional valve 36 is normally in a closed position 36c (illustrated), and an operation signal (PS solenoid current command value corresponding to the operation speed of the left and right one side operation of the steering wheel 13) is sent to the solenoid operation unit 36d on the open position 36a side. Is switched to the open position 36a, and an operation signal (PS solenoid current command value corresponding to the operation speed of the left and right other side operation of the steering wheel 13) is input to the solenoid operating portion 36e on the open position 36b side. Then, it switches to the open position 36b. Note that the operation of the PS cylinder 14 is omitted. When the electromagnetic proportional valve 36 is in the open positions 36a and 36b, the electromagnetic proportional valve 36 is opened at an opening corresponding to the operation signal.

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

  The suction port 17 a of the hydraulic pump motor 17 and the bottom chamber 4 b of the lift cylinder 4 are connected via a hydraulic pipe (first hydraulic oil flow path) 47. The hydraulic piping 47 is connected to the bottom chamber 4b of the lift cylinder 4 and the hydraulic pump motor 17 so that the hydraulic oil discharged from the lift cylinder 4 flows to the suction port 17a of the hydraulic pump motor 17 when the lift operation lever 11 is operated alone. To the suction port 17a. The hydraulic pipe 47 is provided with an electromagnetic proportional valve 48 for lowering the fork. The electromagnetic proportional valve 48 includes an open position 48 a that allows the hydraulic oil to flow from the bottom chamber 4 b of the lift cylinder 4 to the suction port 17 a of the hydraulic pump motor 17, and the suction of the hydraulic pump motor 17 from the bottom chamber 4 b of the lift cylinder 4. It is switched between a closed position 48b that blocks the flow of hydraulic oil to the port 17a.

  The electromagnetic proportional valve 48 is normally in a closed position 48b (illustrated), and an operation signal (a solenoid current command value for fork lowering according to an operation amount of the lowering operation of the lift operation lever 11) is input to the solenoid operating portion 48c. Then, it switches to the open position 48a. Then, the fork 6 descends due to the weight of the fork 6, and the lift cylinder 4 contracts accordingly, and hydraulic oil flows out from the bottom chamber 4 b of the lift cylinder 4. When the electromagnetic proportional valve 48 is in the open position 48a, the electromagnetic proportional valve 48 is opened at an opening corresponding to the operation signal.

  A branch point 91 between the hydraulic pump motor 17 and the electromagnetic proportional valve 48 in the hydraulic pipe 47 is connected to the tank 19 via a hydraulic pipe (second hydraulic oil flow path) 49. The hydraulic pipe 49 is provided with a bypass flow control valve (first flow control valve) 50. The bypass flow control valve 50 controls the flow rate of the hydraulic oil that returns from the lift cylinder 4 to the tank 19. The hydraulic pipe 49 is provided with a filter 54.

  The bypass flow control valve 50 is switched between an open position 50a that allows the flow of hydraulic fluid, a closed position 50b that blocks the flow of hydraulic fluid, and a throttle position 50c that adjusts the flow rate of hydraulic fluid. The pilot operating part on the closed position 50 b side of the bypass flow control valve 50 and the upstream side (front side) of the electromagnetic proportional valve 48 are connected via a pilot flow path 51. The pilot operating part on the open position 50 a side of the bypass flow control valve 50 and the downstream side (rear side) of the electromagnetic proportional valve 48 are connected via a pilot flow path 52. The bypass flow control valve 50 opens at an opening corresponding to the pressure difference before and after the electromagnetic proportional valve 48. Specifically, the bypass flow control valve 50 is in the closed position at the normal time when the electromagnetic proportional valve 48 is closed. When the electromagnetic proportional valve 48 is opened, the bypass flow control valve 50 opens at an opening degree corresponding to the pressure difference before and after the electromagnetic proportional valve 48. At this time, as the pressure difference before and after the electromagnetic proportional valve 48 becomes smaller, the opening degree of the bypass flow control valve 50 becomes larger. As the pressure difference before and after the electromagnetic proportional valve 48 becomes larger, the bypass flow control valve 50 opens. The degree becomes smaller.

  In the hydraulic piping 47, a regenerative flow control valve (second flow control valve) 80 is disposed between the suction port 17 a of the hydraulic pump motor 17 and the branch point 91. The regenerative flow control valve 80 controls the flow rate of the hydraulic fluid flowing from the lift cylinder 4 to the hydraulic pump motor 17. The regenerative flow control valve 80 is switched between an open position 80a that allows the flow of hydraulic fluid, a closed position 80b that blocks the flow of hydraulic fluid, and a throttle position 80c that adjusts the flow rate of hydraulic fluid. The pilot operating portion on the closed position 80 b side of the regenerative flow control valve 80 and the upstream side (front side) of the electromagnetic proportional valve 48 are connected via a pilot flow path 81. The pilot operating portion on the open position 80 a side of the regenerative flow control valve 80 and the downstream side (rear side) of the electromagnetic proportional valve 48 are connected via a pilot flow path 82. The regenerative flow control valve 80 opens at an opening corresponding to the pressure difference before and after the electromagnetic proportional valve 48. Specifically, the regenerative flow control valve 80 is in the closed position at the normal time when the electromagnetic proportional valve 48 is closed. When the electromagnetic proportional valve 48 is opened, the regenerative flow control valve 80 is opened at an opening corresponding to the pressure difference before and after the electromagnetic proportional valve 48. At this time, as the pressure difference before and after the electromagnetic proportional valve 48 decreases, the opening degree of the regenerative flow control valve 80 increases, and as the pressure difference before and after the electromagnetic proportional valve 48 increases, the regenerative flow control valve 80 opens. The degree becomes smaller.

  Among the cylinders described above, the tilt cylinder 9, the attachment cylinder 15, and the PS cylinder 14 that perform different operations from the lift cylinder (first hydraulic cylinder) 4 by supplying and discharging hydraulic oil are collectively referred to as “second hydraulic cylinder 70. May be called. Further, the tilt operation lever 12, the steering wheel 13, and the attachment operation lever, which are levers for operating the second hydraulic cylinder 70, may be collectively referred to as a “second operation unit 73”.

  FIG. 3 is a configuration diagram showing a control system of the hydraulic drive device 16. In the figure, a hydraulic drive device 16 includes a lift operation lever operation amount sensor (operation amount detection unit) 55 that detects an operation amount of the lift operation lever 11 and a tilt operation lever operation amount that detects an operation amount of the tilt operation lever 12. A sensor 56, an attachment operation lever operation amount sensor 57 for detecting the operation amount of an attachment operation lever (not shown), a steering operation speed sensor 58 for detecting the operation speed of the steering wheel 13, and the actual rotational speed of the electric motor 18 ( A rotation speed sensor 59 for detecting the actual rotation speed of the motor) and a controller 60 are provided.

  The controller 60 inputs detection values of the operation lever operation amount sensors 55 to 57, the steering operation speed sensor 58, and the rotation speed sensor 59, performs predetermined processing, and performs the electric motor 18, the electromagnetic proportional valves 23, 26, 31, 36. , 48 are controlled. The sensors 56, 57, and 58 that detect the operation amount of the second operation unit 73 may be referred to as “second operation amount detection unit 71”. In addition, electromagnetic proportional valves 26, 31, 36 that are disposed between the discharge port 17 b of the hydraulic pump motor 17 and the second hydraulic cylinder and control the flow of the hydraulic oil based on the operation of the second operation unit 73 are provided. It may be referred to as “second control valve 72”.

  FIG. 4 is a block configuration diagram showing a block configuration of a control system of the hydraulic drive device 16. As shown in FIG. 4, the controller 60 includes a motor driver 61, a power running torque limit control target rotational speed calculation unit 66, a motor command rotational speed calculation unit 67, and a determination unit 69.

  The motor driver 61 includes comparison units 62A and 62B, a PID calculation unit 63, a power running torque limit value calculation unit 68, an output torque determination unit (control unit) 64, and a motor control unit (control unit) 65. ing. The comparison unit 62A calculates a rotational speed deviation between the motor command rotational speed set by the motor command rotational speed calculation unit 67 and the actual motor rotational speed detected by the rotational speed sensor 59. The comparison unit 62B calculates a rotational speed deviation between the power running torque limit control target rotational speed set by the power running torque limit control target rotational speed calculation unit 66 and the actual motor rotational speed detected by the rotational speed sensor 59. The PID calculation unit 63 performs a PID calculation of a rotation speed deviation between the motor command rotation speed and the motor actual rotation speed, and obtains a power running torque command value of the electric motor 18 such that the rotation speed deviation becomes zero. The PID calculation is a combination of a proportional operation, an integral operation, and a derivative operation. The power running torque limit value calculation unit 68 calculates the power running torque limit value of the electric motor 18 based on the rotation speed deviation between the power running torque limit control target rotation speed and the actual motor rotation speed detected by the rotation speed sensor 59. Set. The power running torque limit value is a value for limiting the output torque so as not to increase when the output torque of the electric motor 18 moves toward the power running side. The power running torque limit value set by the power running torque limit value calculation unit 68 will be described in detail.

  The output torque determination unit 64 and the motor control unit 65 constituting the control unit control the electric motor 18 so that the rotation speed is based on the motor command rotation speed (rotation speed command value), and the output torque of the electric motor 18 is power running. When heading to the side, the electric motor 18 is controlled so that the rotational speed is based on the power running torque limit value. The output torque determination unit 64 is a power running torque command value (a value based on the motor command rotational speed) obtained by the PID calculation unit 63 and a power running torque of the electric motor 18 set by the power running torque limit value calculation unit 68. The output torque of the electric motor 18 is determined by comparing with the limit value. Specifically, when the power running torque command value is less than or equal to the power running torque limit value, the power running torque command value is set as the output torque of the electric motor 18, and when the power running torque command value is higher than the power running torque limit value, the power running torque limit is set. The value is the output torque of the electric motor 18. The motor control unit 65 converts the output torque determined by the output torque determination unit 64 into a current signal and sends it to the electric motor 18. When the electric motor 18 is controlled so as to have a rotational speed based on the power running torque limit value and cannot be driven based on the motor command rotational speed, the bypass flow control valve 50 is connected via the hydraulic pipe 49. The hydraulic oil is discharged to the tank 19.

  The motor command rotation speed calculation unit 67 acquires detection values detected by the sensors 55, 56, 57, and 58, and sets a motor command rotation speed (rotation speed command value) based on the detection values. The motor command rotation speed calculation unit 67 sets the motor command rotation speed according to the operation amount of each operation lever. The motor command rotational speed set by the motor command rotational speed calculation unit 67 will be described in detail. The power running torque limit control target rotational speed calculation unit 66 acquires the detection values detected by the sensors 55, 56, 57, and 58, and sets the power running torque limit control target rotational speed based on the detected values. The power running torque limit control target rotational speed calculation unit 66 sets the power running torque limit control target rotational speed according to the operation state of each operation lever.

  The determination unit 69 determines whether the lowering operation of the lift operation lever 11 is performed alone and whether the second operation unit 73 including the lowering operation of the lift operation lever 11 is performed simultaneously. For example, when the fork lowering + tilt operation, the fork lowering + attachment operation, the fork lowering + power steering operation, and the fork lowering + tilt + power steering operation are performed, the determination unit 69 includes the second operation unit including the lift operation lever 11. It is determined that the operations 73 are performed simultaneously. The determination unit 69 outputs the determination result to the motor command rotational speed calculation unit 67 and the power running torque limit value calculation unit 68.

  FIG. 5 is a flowchart showing a control processing procedure executed by the controller 60. In this control process, only the operation including the lowering of the fork 6 (fork lowering) is targeted. In addition, the period for executing this control process is appropriately determined by experiments or the like.

  In the figure, first, the operation amounts of the lift operation lever 11, the tilt operation lever 12 and the attachment operation lever detected by the operation lever operation amount sensors 55 to 57, and the operation speed of the steering wheel 13 detected by the steering operation speed sensor 58. Is acquired (procedure S101).

  Subsequently, the fork lowering mode as the operation condition is determined based on the operation amount of the lift operation lever 11, the tilt operation lever 12, the attachment operation lever and the operation speed of the steering wheel 13 acquired in step S101 (step S102). Fork lowering modes include fork lowering single operation, fork lowering + tilt operation, fork lowering + attachment operation, fork lowering + power steering operation, fork lowering + tilt + power steering operation.

  Subsequently, the solenoid proportional valve solenoid current according to the operation amount of the lift operation lever 11, the tilt operation lever 12, the attachment operation lever and the operation speed of the steering wheel 13 acquired in step S101 and the fork lowering mode determined in step S102. A command value is obtained (procedure S103). The solenoid proportional valve solenoid current command value includes a fork lowering solenoid current command value corresponding to the operation amount of the lowering operation of the lift operation lever 11, a tilt solenoid current command value corresponding to the operation amount of the tilt operation lever 12, and an attachment operation. There are an attachment solenoid current command value according to the lever operation amount and a power steering (PS) solenoid current command value according to the operation speed of the steering 13.

  Subsequently, a necessary rotational speed for the operation condition obtained in step S102 is obtained (procedure S104). The required rotational speed includes a lift required motor speed, a tilt required motor speed, an attachment required motor speed, and a power steering (PS) required motor speed. The lift required motor rotation speed is the rotation speed of the electric motor 18 necessary for performing the lift operation. The tilt required motor rotational speed is the rotational speed of the electric motor 18 necessary for performing the tilt operation. The attachment-required motor rotational speed is the rotational speed of the electric motor 18 necessary for performing the attachment operation. The PS required motor rotational speed is the rotational speed of the electric motor 18 necessary for performing the PS operation.

  Subsequently, the motor command rotational speed calculation unit 67 sets a motor rotational speed command value (motor command rotational speed) based on the fork lowering mode determined in step S102 and the necessary rotational speed obtained in step S104 ( Procedure S105). At this time, the motor command rotational speed is set based on the above-described FIG.

  Subsequently, the power running torque limit value of the electric motor 18 is set based on the fork lowering mode determined in step S102 (step S106). The power running torque limit value is an allowable power running torque value. At this time, the power running torque limit value calculation unit 68 is set based on the above-described FIG.

  After performing step S106, the electromagnetic proportional valve solenoid current command value obtained in step S103 is sent to the solenoid operation unit of the corresponding electromagnetic proportional valve (step S107). At this time, the fork lowering solenoid current command value is sent to the solenoid operating portion 48 c of the electromagnetic proportional valve 48. Also, when the tilt solenoid current command value is obtained, the current command value is sent to either of the solenoid operating portions 26d and 26e of the electromagnetic proportional valve 26, and when the attachment solenoid current command value is obtained, When the current command value is sent to one of the solenoid operating portions 31d and 31e of the electromagnetic proportional valve 31 and the PS solenoid current command value is obtained, the current command value is sent to the solenoid operating portions 36d and 36e of the electromagnetic proportional valve 36. To any of the above.

  Subsequently, the motor rotational speed command value (motor command rotational speed) set in step S105, the actual motor rotational speed detected by the rotational speed sensor 59, and the power running torque limit value of the electric motor 18 set in step S106 are obtained. Based on this, the output torque of the electric motor 18 is obtained, and the output torque is sent to the electric motor 18 as a control signal (step S108). The process of step S108 is executed by a motor driver 61 included in the controller 60 as shown in FIG.

  Next, the characteristics of the motor speed of the electric motor 18 and the cylinder flow rate of the lift cylinder 4 in the hydraulic drive device 16 of the present embodiment will be described with reference to FIG. FIG. 6A is a graph showing the relationship between the lowering operation amount and the motor rotation speed. The horizontal axis of FIG. 6A is the operation amount of the lift operation lever 11 (hereinafter referred to as the downward operation amount), and the vertical axis indicates the motor rotation speed of the electric motor 18. The motor rotation speed is equivalent to the pump rotation speed of the hydraulic pump motor 17 and is a value corresponding to the opening of the descending electromagnetic proportional valve 48. As shown in FIG. 6A, a direct proportional relationship is established between the lowering operation amount and the motor speed (that is, the opening degree of the electromagnetic proportional valve 48 for lowering).

  FIG. 6B is a graph showing the relationship between the motor speed and the cylinder flow rate. The horizontal axis of FIG. 6B indicates the motor rotation speed of the electric motor 18 and may be regarded as being equivalent to the pump rotation speed of the hydraulic pump motor 17. The vertical axis in FIG. 6B is the cylinder flow rate of the lift cylinder 4 and may be regarded as a value corresponding to the fork lowering speed. Further, in FIG. 6B, the graph L1 indicating the characteristics when the lowering operation amount is “large”, the graph L2 indicating the characteristics when the lowering operation amount is “medium”, and the lowering operation amount. A graph L3 showing characteristics in the case of “small” is shown. As can be seen from the graphs L1, L2, and L3, the control is performed so that the cylinder flow rate, that is, the fork lowering speed increases as the lowering operation amount increases. As shown in FIG. 6A, the operation amount can be set steplessly by the driver's lever operation. In FIG. 6B, for the sake of explanation, “large”, “medium”, and “small” are used. The three-stage case is taken as an example.

  FIG. 6B shows a graph LP indicating the relationship between the motor rotation speed (pump rotation speed) and the pump flow rate of the hydraulic pump motor 17. As shown in the graph LP, a direct proportional relationship is established between the motor rotation speed and the pump flow rate of the hydraulic pump motor 17. When the fork lowering operation is performed independently, the motor rotation speed command value for each lowering operation amount is set to P1, P2, and P3 on the graph LP, respectively. For example, when the lowering operation amount is “large”, the fork lowering operation is performed alone, the load is heavy, and the bypass flow control valve 50 controls the flow rate of the hydraulic oil (discharges the hydraulic oil to the tank 19). Is not performed, the motor rotation speed and the cylinder flow rate are values at “P1”.

  Here, the flow rate control by the bypass flow control valve 50 is performed in the region E1 in which the motor rotation speed is more negative than the graph LP (left side of the drawing). That is, the flow control by the bypass flow control valve 50 is performed in the graphs L1a, L2a, and L3a on the region E1 side in the graphs L1, L2, and L3. At this time, the regenerative flow control valve 80 is in an “open” state. In the region E1, as shown in the graphs L1a, L2a, and L3a, the flow rate of the hydraulic oil discharged by the bypass flow control valve 50 so that the cylinder flow rate (that is, the fork lowering speed) becomes constant according to the downward operation amount. To control. For example, the motor rotational speed in the state where the lowering operation amount is “large” and the single lowering operation is performed is “P1”, and the state shifts from this state to the simultaneous operation of the second hydraulic cylinder 70 and the motor rotational speed is “P1”. “R1” smaller than “”. In this case, since the pressure difference before and after the electromagnetic proportional valve 48 becomes smaller, the opening degree of the regenerative flow control valve 80 becomes larger and the opening degree of the bypass flow control valve 50 becomes larger, so that a part of the cylinder flow rate is reduced. It is discharged to the tank 19 via the bypass flow control valve 50. Specifically, hydraulic oil corresponding to the flow rate indicated by “V 1” between the graph L 1 a and the pump flow rate graph LP is discharged to the tank 19 by the bypass flow control valve 50. On the other hand, regeneration is performed by the hydraulic oil relating to the flow rate indicated by “V2” in the graph LP flowing into the suction port 17a of the hydraulic pump motor 17.

  In the region E2 where the motor rotational speed is on the positive side (the right side of the drawing) than the graph LP, the flow rate control by the regenerative flow rate control valve 80 is performed. That is, the flow control by the regenerative flow control valve 80 is performed in the graphs L1b, L2b, and L3b and the graphs L1c, L2c, and L3c on the region E2 side in the graphs L1, L2, and L3. The bypass flow control valve 50 at this time is in a “closed” state. In the region E2, as shown in the graphs L1c, L2c, and L3c, the regenerative flow control valve 80 causes the suction of the hydraulic pump motor 17 so that the cylinder flow rate (that is, the fork lowering speed) becomes constant according to the lowering operation amount. The flow rate of the hydraulic oil flowing to the port 17a is controlled. In the graphs L1c, L2c, and L3c, the difference between the pump flow rate corresponding to the motor rotation speed and the cylinder flow rate kept constant is that the hydraulic pump motor 17 pulls the hydraulic oil from the tank 19 via the hydraulic pipe 20. It is supplemented by that. Therefore, regeneration does not occur in the graphs L1c, L2c, and L3c. The cylinder flow rate (that is, the fork lowering speed) in the graphs L1c, L2c, and L3c is set higher than the cylinder flow rate (that is, the fork lowering speed) in the graphs L1a, L2a, and L3a. That is, the flow rate of the hydraulic oil that can be controlled by the regenerative flow control valve 80 is set to be larger than the flow rate of the hydraulic oil that can be controlled by the bypass flow control valve.

  In the graphs L1b, L2b, and L3b, the degree of throttling of the regenerative flow control valve 80 is adjusted so that the cylinder flow rate slightly rises along the pump flow rate graph LP as the motor rotation speed increases. Regeneration occurs in the graphs L1b, L2b, and L3c. The portions of the graphs L1b, L2b, and L3b function as a buffer unit when shifting from the flow control by the bypass flow control valve 50 to the flow control by the regenerative flow control valve 80.

  When the second hydraulic cylinder 70 is operated simultaneously in addition to the lowering operation of the lift cylinder 4 and the required rotational speed of the second hydraulic cylinder 70 is larger than the required rotational speed of the lowering, the motor rotational speed increases and the region E2 side control is performed. For example, the motor rotational speed in a state where the lowering operation amount is “large” and the single lowering operation is performed is “P1”. From this state, the second hydraulic cylinder 70 is simultaneously operated and the motor rotational speed is “P1”. "R2" larger than "." In this case, since the pressure difference before and after the electromagnetic proportional valve 48 increases, the opening of the bypass flow control valve 50 decreases and the opening of the regenerative flow control valve 80 decreases, so that the cylinder flow corresponds to the graph L1c. The value to be That is, a significant change in the descending speed is suppressed. On the other hand, hydraulic fluid having a flow rate related to “V3” between the pump flow rate and the cylinder flow rate at the motor rotation speed “R2” is sucked up from the tank 19 via the hydraulic pipe 20 by the hydraulic pump motor 17.

  Next, the operation of the hydraulic drive device 16 of this embodiment will be described with reference to FIG. When the fork lowering operation is performed independently, the control units 64 and 65 set the power running torque limit control target rotational speed to be close to 0 rpm and perform the power running torque limit control. As described above, in the power running torque limit control, “rotational speed deviation = power running torque limit control target rotational speed−actual rotational speed” is set, and the power running torque limit value output is determined so that the rotational speed deviation becomes zero. The In FIG. 7, three patterns of control forms are shown. In any form, such a power running torque limit control is performed at the time of the single operation of the fork lowering operation (hereinafter simply referred to as “single operation”). The

  FIG. 7 shows a case where the other necessary rotational speed necessary for operating other actuators other than the fork at a desired speed is smaller than the necessary rotational speed necessary for lowering the fork at the desired speed. The upper graph in FIG. 7 shows a state where the load is large (high load state) and sufficient regeneration can be performed. The lower graph of FIG. 7 shows a state where the load is small (low load state) and sufficient regeneration cannot be performed.

  In the control mode shown in FIG. 7A, when the fork lowering operation is performed alone, the power running torque limit control is turned ON, and the command rotation speed of the electric motor 18 is set to the power running torque limit target rotation speed (for example, 0 rpm). Set the value in the neighborhood). When a fork lowering operation and a simultaneous operation of the second hydraulic cylinder 70 (hereinafter simply referred to as “simultaneous operation”) are performed, the command rotational speed of the electric motor 18 is the required rotational speed and the second hydraulic cylinder 70. Is set to a higher one (represented by “other required rotation number”). Further, the power running torque limit control is set to OFF (power running is 100% permitted). As shown in the upper graph of FIG. 7A, since the energy of the load is sufficiently large in a high load state, the hydraulic oil discharged from the lift cylinder 4 is electrically operated during the single operation for performing the fork lowering operation alone. Regeneration is performed with the actual rotational speed of the motor 18 being the required rotational speed. Further, when the operation is shifted from the single operation to the simultaneous operation in a high load state, the actual rotational speed of the electric motor 18 is controlled to the revolving required rotational speed, regeneration is performed, and the hydraulic oil discharged from the lift cylinder 4 As a result, the hydraulic pump motor 17 is driven and hydraulic oil is supplied to the second hydraulic cylinder 70. That is, in this case, regeneration and other actuator operations can be performed by effectively using the energy of the load. On the other hand, as shown in the lower graph of FIG. 7A, during the single operation in the low load state, the energy of the hydraulic oil discharged from the lift cylinder 4 is small, and the actual rotational speed of the electric motor 18 is required to be lowered. Does not rise to a number. In this case, since the pressure difference before and after the electromagnetic proportional valve 48 becomes smaller, the opening degree of the bypass flow control valve 50 becomes larger, and much of the hydraulic oil discharged from the lift cylinder 4 passes through the bypass flow control valve 50. And discharged to the tank 19. Further, when the operation is shifted from the single operation to the simultaneous operation in the low load state, the power running torque limit control is turned off, so that the electric motor 18 is powered and the actual rotational speed of the electric motor 18 is reduced to the required rotational speed (other necessary rotational speeds). Higher than the number). At this time, the opening degree of the bypass flow control valve 50 is controlled to an opening degree corresponding to the pressure difference of the electromagnetic proportional valve 48, and a part of the hydraulic oil discharged from the lift cylinder 4 is bypassed to the tank 19.

  In the control mode shown in FIG. 7B, when the fork lowering operation is performed alone, the power running torque limit control is turned ON, and the command rotation speed of the electric motor 18 is set to the power running torque limit target rotation speed (for example, 0 rpm). Set the value in the neighborhood). When the fork lowering operation and the second hydraulic cylinder 70 are simultaneously performed, the command rotational speed of the electric motor 18 is set to the necessary rotational speed of the second hydraulic cylinder 70 (other necessary rotational speed). . Further, the power running torque limit control is set to OFF (power running is 100% permitted). As shown in the upper graph of FIG. 7B, regeneration is performed with the actual rotational speed of the electric motor 18 being the required rotational speed at the time of single operation at a high load. Further, during simultaneous operation with a high load, regeneration is performed by controlling the actual rotational speed of the electric motor 18 to other required rotational speed that is smaller than the required rotational speed, and the electric motor 18 is driven by hydraulic oil discharged from the lift cylinder 4. The hydraulic oil is supplied to the second hydraulic cylinder via the hydraulic pump motor 17. At this time, the pressure difference before and after the electromagnetic proportional valve 48 is reduced, so that the degree of opening of the bypass flow control valve 50 is increased, and a part of the hydraulic oil discharged from the lift cylinder 4 is bypassed. It is discharged to the tank 19 through the control valve 50. As shown in the lower graph of FIG. 7B, the actual rotational speed of the electric motor 18 does not increase to the required rotational speed during the single operation with a low load. In this case, the pressure difference before and after the electromagnetic proportional valve 48 becomes smaller, the opening degree of the bypass flow control valve 50 becomes larger, and most of the hydraulic oil discharged from the lift cylinder 4 passes through the bypass flow control valve 50. And discharged to the tank 19. Further, during simultaneous operation with a low load, the power running torque limit control is turned off, so that the electric motor 18 is powered and the actual rotational speed of the electric motor 18 is controlled to the other necessary rotational speed. At this time, the opening degree of the bypass flow control valve 50 is controlled to an opening degree corresponding to the pressure difference of the electromagnetic proportional valve 48, and a part of the hydraulic oil discharged from the lift cylinder 4 is bypassed to the tank 19.

  In the control mode shown in FIG. 7C, when the fork lowering operation is performed alone, the power running torque limit control is turned ON, and the command rotation speed of the electric motor 18 is set to the power running torque limit target rotation speed (for example, 0 rpm). Set the value in the neighborhood). When the fork lowering operation and the second hydraulic cylinder 70 are simultaneously performed, the command rotational speed of the electric motor 18 is equal to the required rotational speed of the lowering and the required rotational speed of the second hydraulic cylinder 70 (other required rotational speed). Set to the higher one. The power running torque limit control is set to ON. The power running torque limit control target rotational speed is set to a necessary rotational speed of the second hydraulic cylinder 70 (other necessary rotational speed). As shown in the upper graph of FIG. 7 (c), during a single operation with a high load, the actual rotational speed of the electric motor 18 is increased to the required rotational speed for reduction, and regeneration is performed. Further, at the same time when the high load is operated, the actual rotational speed of the electric motor 18 is controlled to the revolving required rotational speed to perform regeneration, and the hydraulic pump motor 17 is driven by the hydraulic oil discharged from the lift cylinder 4 to 2 Hydraulic oil is supplied to the hydraulic cylinder 70. As shown in the lower graph of FIG. 7C, the actual rotational speed of the electric motor 18 does not increase to the required rotational speed during the single operation with a low load. In this case, the pressure difference before and after the electromagnetic proportional valve 48 becomes smaller, the opening degree of the bypass flow control valve 50 becomes larger, and most of the hydraulic oil discharged from the lift cylinder 4 passes through the bypass flow control valve 50. And discharged to the tank 19. Further, during simultaneous operation with a low load, the power running torque limit control is turned ON, and the actual rotational speed of the electric motor 18 is limited to other necessary rotational speeds. At this time, the opening degree of the bypass flow control valve 50 is controlled to an opening degree corresponding to the pressure difference of the electromagnetic proportional valve 48, and a part of the hydraulic oil discharged from the lift cylinder 4 is bypassed to the tank 19.

  A case where the same control as in FIGS. 7A, 7B, and 7C is performed and the other required rotational speed is larger than the required rotational speed for lowering will be described. In this case, regardless of which control content is employed, a graph having the same actual rotational speed is drawn as shown in FIG. As shown in the upper graph of FIG. 8, in a high load state, the fork lowering operation is performed independently regardless of the control in FIGS. 7 (a), 7 (b), and 7 (c). During the single operation, the hydraulic oil discharged from the lift cylinder 4 causes the actual rotational speed of the electric motor 18 to become the required rotational speed to be regenerated. Further, when the operation is shifted from the single operation to the simultaneous operation in a high load state, the actual rotational speed of the electric motor 18 is controlled to the other necessary rotational speed to perform regeneration, and the hydraulic oil discharged from the lift cylinder 4 As a result, the hydraulic pump motor 17 is driven and hydraulic oil is supplied to the second hydraulic cylinder 70. As shown in the lower graph of FIG. 8, during a single operation in a low load state, the energy of the hydraulic oil discharged from the lift cylinder 4 is small, and the actual rotational speed of the electric motor 18 does not increase to the required rotational speed. In this case, since the pressure difference before and after the electromagnetic proportional valve 48 becomes smaller, the opening degree of the bypass flow control valve 50 becomes larger, and much of the hydraulic oil discharged from the lift cylinder 4 passes through the bypass flow control valve 50. And discharged to the tank 19. Further, when shifting from the single operation to the simultaneous operation in the low load state, the actual rotational speed of the electric motor 18 becomes the other necessary rotational speed (higher than the descending necessary rotational speed) in any control. At this time, the opening degree of the bypass flow control valve 50 is controlled to an opening degree corresponding to the pressure difference of the electromagnetic proportional valve 48, and a part of the hydraulic oil discharged from the lift cylinder 4 is bypassed to the tank 19.

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

  In the hydraulic drive device 16 of the cargo handling vehicle 1 according to this embodiment, a hydraulic pipe 49 is connected via a branch point 91 from a hydraulic pipe 47 for sending hydraulic oil from the lift operation lever 11 to the hydraulic pump motor 17. . A bypass flow control valve 50 for controlling the flow rate of the hydraulic oil returning from the lift operation lever 11 to the tank 19 is disposed on the hydraulic pipe 49. Further, in the hydraulic pipe 47, a regenerative flow control valve 80 that controls the flow rate of the hydraulic oil flowing from the lift operation lever 11 to the hydraulic pump motor 17 is provided between the suction port 17 a of the hydraulic pump motor 17 and the branch point 91. It is arranged. According to such a configuration, for example, when the load is light, the motor rotation speed of the electric motor 18 connected to the hydraulic pump motor 17 is higher than the motor rotation speed corresponding to the operation amount of the lowering operation of the lift operation lever 11. When it is low (on the side of the region E1 in FIG. 6), the bypass flow control valve 50 returns the hydraulic oil from the lift operation lever 11 to the tank 19, whereby the fork lowering speed corresponding to the operation amount of the lowering operation can be obtained. On the other hand, the lowering operation and the operation of the other hydraulic cylinder are performed simultaneously (and the required rotation speed of the other hydraulic cylinder is larger than the required rotation speed of the other hydraulic cylinder), so that the motor rotation speed is increased compared with the single lowering operation. When the flow rate of the pump motor 17 increases (the region E2 side in FIG. 6), the regenerative flow control valve 80 controls the hydraulic oil flow from the lift operation lever 11 to the hydraulic pump motor 17 so as to lower the fork. The rapid increase in speed can be suppressed. As described above, when the lowering lift cylinder 4 is lowered and the other hydraulic cylinders are simultaneously operated, the other actuators can be operated at a desired speed and the lifted object lift can be lowered at the desired lowering speed. it can. In addition, during simultaneous operation, even if the required rotational speed for lowering is greater than the required rotational speed for other hydraulic cylinders, it is possible to operate other hydraulic cylinders using the load load energy. As a result, energy saving can be achieved.

  In the hydraulic drive device 16 of the cargo handling vehicle 1 according to the present embodiment, the flow rate of the hydraulic fluid that can be controlled by the regenerative flow control valve 80 is set to be larger than the flow rate of the hydraulic fluid that can be controlled by the bypass flow control valve 50. ing. Accordingly, when the fork descending speed is kept constant by controlling the regenerative flow control valve 80 with respect to a predetermined lowering operation amount (the portions of the graphs L1c, L2c, and L3c in FIG. 6), the bypass flow control valve 50 is used. As compared with the case where the fork descending speed is kept constant by the control (the portions of the graphs L1a, L2a, L3a in FIG. 6), the fork descending speed by the control of the regenerative flow control valve 80 can be made higher. . As a result, when the motor rotational speed is increased, the transition from the control by the bypass flow control valve 50 to the control by the regenerative flow control valve 80 is performed. Graphs L1b, L2b, and L3b shown in FIG. 6) can be provided. By providing such a transition portion, it is possible to suppress abrupt change from the control by the bypass flow control valve 50 to the control by the regenerative flow control valve 80. For example, even if the motor rotation speed slightly increases due to temperature changes, etc., instead of simultaneous operation, if the control is switched immediately, regeneration will not be performed at unnecessary timing, reducing the regeneration efficiency. End up. By providing the transition portion that functions as the buffer unit, such a decrease in regeneration efficiency can be suppressed.

  In the hydraulic drive device 16 of the cargo handling vehicle 1 according to this embodiment, the regenerative flow control valve 80 controls the flow rate of the hydraulic oil based on the pressure difference before and after the electromagnetic proportional valve 48. Thereby, the regenerative flow control valve can be controlled at a fork lowering speed corresponding to the operation amount of the lowering operation.

  In the hydraulic drive device 16 of the cargo handling vehicle 1 according to the present embodiment, the bypass flow control valve 50 controls the flow rate of the hydraulic oil based on the pressure difference before and after the electromagnetic proportional valve 48. Thereby, the regenerative flow control valve can be controlled at a fork lowering speed corresponding to the operation amount of the lowering operation.

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

  In the above-described embodiment, a tilt cylinder, a PS cylinder, and an attachment cylinder are provided as the second hydraulic cylinder. However, at least one second hydraulic cylinder may be provided, and a part thereof may be omitted. For example, in the above-described embodiment, the attachment and the power steering are mounted, but the hydraulic drive device of the present invention can be applied to a forklift that is not mounted with the attachment and the power steering. The hydraulic drive device of the present invention is applicable to any battery-type cargo handling vehicle other than a forklift.

  DESCRIPTION OF SYMBOLS 1 ... Cargo handling vehicle, 4 ... Lift cylinder (hydraulic cylinder), 6 ... Fork (lifting object), 11 ... Lift operation lever (1st operation part), 16 ... Hydraulic drive device, 17 ... Hydraulic pump motor (hydraulic pump), 17a ... Suction port, 17b ... Discharge port, 18 ... Electric motor, 47 ... Hydraulic piping (first hydraulic fluid flow path), 48 ... Electromagnetic proportional valve (electromagnetic proportional valve) for fork lowering, 49 ... Hydraulic piping (first Hydraulic fluid flow), 50 ... bypass flow control valve (first flow control valve), 70 ... second hydraulic cylinder, 73 ... second operating portion, 80 ... regenerative flow control valve.

Claims (4)

A first lifting / lowering hydraulic cylinder that lifts and lowers the lifting object by supplying and discharging hydraulic oil;
A second hydraulic cylinder that operates differently from the first hydraulic cylinder by supplying and discharging the hydraulic oil;
A first operating portion for operating the first hydraulic cylinder;
A second operating portion for operating the second hydraulic cylinder;
A hydraulic pump for supplying and discharging the hydraulic oil to and from the first hydraulic cylinder and the second hydraulic cylinder;
An electric motor connected to the hydraulic pump and functioning as an electric motor or a generator;
A tank for storing the hydraulic oil;
A first hydraulic fluid passage for connecting the suction port of the hydraulic pump and the first hydraulic cylinder, and for sending the hydraulic fluid from the first hydraulic cylinder to the hydraulic pump;
A second hydraulic oil passage for connecting the branch point on the first hydraulic oil passage and the tank, and returning the hydraulic oil from the first hydraulic cylinder to the tank;
A first flow rate control valve disposed on the second hydraulic oil flow path for controlling the flow rate of the hydraulic oil returning from the first hydraulic cylinder to the tank;
A second flow rate that is disposed between the suction port of the hydraulic pump and the branch point in the first hydraulic fluid flow path and controls the flow rate of the hydraulic fluid that flows from the first hydraulic cylinder to the hydraulic pump. A control valve,
When the lowering operation by the first operation unit and the operation of the second operation unit are performed at the same time, the number of rotations of the hydraulic pump is increased and the flow rate of the hydraulic pump is increased compared with the single operation of the first operation unit. A hydraulic drive device for a cargo handling vehicle that controls the second flow rate control valve so as to suppress a flow rate of the hydraulic fluid from the first hydraulic cylinder to the hydraulic pump.   2. The hydraulic pressure of the cargo handling vehicle according to claim 1, wherein a flow rate of the hydraulic oil that can be controlled by the second flow rate control valve is set to be greater than a flow rate of the hydraulic oil that can be controlled by the first flow rate control valve. Drive device. A proportional valve that is disposed between the first hydraulic cylinder and the branch point in the first hydraulic oil flow path and opens at an opening degree corresponding to an operation amount of the lowering operation of the first operation unit; Prepared,
The hydraulic drive device for a cargo handling vehicle according to claim 1 or 2, wherein the second flow rate control valve controls a flow rate of the hydraulic oil based on a pressure difference before and after the proportional valve. A proportional valve that is disposed between the first hydraulic cylinder and the branch point in the first hydraulic oil flow path and opens at an opening degree corresponding to an operation amount of the lowering operation of the first operation unit; Prepared,
The hydraulic drive device for a cargo handling vehicle according to any one of claims 1 to 3, wherein the first flow rate control valve controls a flow rate of the hydraulic oil based on a pressure difference before and after the proportional valve.

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