JP6318891B2 - Hydraulic drive device for cargo handling vehicle - Google Patents

Description

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

  A battery-type forklift that is one of cargo handling vehicles includes a lift cylinder that lifts and lowers the fork, a tilt cylinder that tilts the mast, a hydraulic pump that supplies hydraulic oil to the lift cylinder and the tilt cylinder, and an electric motor that drives the hydraulic pump And. In such a forklift, when unloading a load with a fork, there is a case where cargo handling regeneration is performed in which the hydraulic oil is returned from the lift cylinder to the hydraulic pump by using the weight of the load.

  As a conventional technique for performing such a cargo handling regeneration operation, for example, a hydraulic lift device as described in Patent Document 1 is known. The hydraulic lift device described in Patent Document 1 is connected in series toward a hydraulic pump between a control valve assembly disposed between a bottom chamber of a lift cylinder and a hydraulic pump, and between the control valve assembly and the hydraulic pump. A hydraulic pilot switching valve and an electromagnetic switching valve are provided.

US Pat. No. 5,649,422

  In the above prior art, when the fork is lowered while the load load of the fork (lifting object) is small (light load state), the hydraulic oil from the lift cylinder is switched to the hydraulic pilot switching valve and the electromagnetic switching without carrying out the cargo handling regeneration. It returns to the tank through the valve. At this time, since the hydraulic pilot switching valve and the electromagnetic switching valve are arranged in series, the pressure loss when hydraulic fluid flows increases. In particular, when the hydraulic pilot switching valve and the electromagnetic switching valve are reduced in size due to the recent demand for miniaturization of the apparatus, the flow area (flow channel diameter) of the hydraulic pilot switching valve and the electromagnetic switching valve must be reduced. Such a problem becomes remarkable because it cannot be obtained. If the pressure loss when the hydraulic oil flows in this way becomes large, when the fork is lowered in a light load state, the flow rate of the hydraulic oil that returns to the tank decreases, so the lowering speed of the fork becomes slow.

  An object of the present invention is to provide a hydraulic drive device for a cargo handling vehicle capable of increasing a descending speed of an elevating object at a light load.

  The present invention relates to a hydraulic drive device for a cargo handling vehicle having a hydraulic cylinder that raises and lowers a lifted object by supplying and discharging hydraulic oil, a tank for storing hydraulic oil, and a hydraulic pump that sucks hydraulic oil from the tank and supplies the hydraulic cylinder to the hydraulic cylinder. Connecting the suction port of the hydraulic pump and the bottom chamber of the hydraulic cylinder, connecting the first hydraulic fluid passage for sending the hydraulic fluid from the hydraulic cylinder to the hydraulic pump, the first hydraulic fluid passage and the tank. A second hydraulic oil passage for returning the hydraulic oil from the hydraulic cylinder to the tank, a flow rate control valve disposed on the second hydraulic oil passage and controlling the flow rate of the hydraulic oil returning from the hydraulic cylinder to the tank; A pilot check valve disposed upstream of the flow rate control valve on the second hydraulic fluid flow path and allowing the hydraulic oil to pass only in a direction returning to the tank; and a pilot check valve downstream of the flow rate control valve in the second hydraulic fluid flow path and the pilot A pilot passage connecting the Ekku valve, characterized in that it comprises a closing valve disposed in the pilot flow path.

  In such a hydraulic drive device for a cargo handling vehicle according to the present invention, when the lifted object is lowered in a state where the load load of the lifted object is small (light load state), the hydraulic oil from the hydraulic cylinder is supplied to the second hydraulic oil passage. Return to the tank through. A flow rate control valve that controls the flow rate of the hydraulic fluid that returns from the hydraulic cylinder to the tank and a pilot check valve that allows the hydraulic fluid to pass only in the direction that returns to the tank are disposed on the second hydraulic fluid passage. For this reason, the hydraulic oil from the hydraulic cylinder returns to the tank through the pilot check valve and the flow rate control valve. By the way, the opening degree of the pilot check valve is determined by the differential pressure between the pressure on the upstream side of the pilot check valve in the second hydraulic oil passage and the pressure in the pilot passage. As the differential pressure increases, the opening of the pilot check valve increases. Here, the pilot check valve is disposed upstream of the flow rate control valve on the second hydraulic oil passage. For this reason, the pressure upstream of the pilot check valve in the second hydraulic oil passage is not lost by the flow control valve. The pilot flow path connects the downstream side of the flow control valve in the second hydraulic oil flow path and the pilot check valve. When the lift is lowered in a light load state, the on-off valve disposed on the pilot channel is opened. At this time, the pressure in the pilot channel is sufficiently low (for example, tank pressure). Accordingly, since the differential pressure between the pressure upstream of the pilot check valve in the second hydraulic oil flow path and the pressure in the pilot flow path increases, the opening of the pilot check valve increases, and the flow rate of the hydraulic oil returning to the tank increases. Become more. Thereby, the descent | fall speed of the raising / lowering object at the time of a light load can be made quick.

  The flow control valve may be a pilot flow control valve that opens at an opening degree corresponding to the pilot pressure. In this case, an inexpensive flow control valve can be used.

  The flow control valve may be an electromagnetic proportional flow control valve that opens at an opening degree corresponding to the control signal. In this case, the flow rate of the hydraulic oil passing through the flow rate control valve can be controlled smoothly, so that the lowering operation (lowering speed) of the lifted object can be controlled smoothly.

  According to the hydraulic drive apparatus for a cargo handling vehicle according to the present invention, the descending speed of the lifting object at a light load can be increased.

It is a side view showing a cargo handling vehicle provided with a first embodiment of a hydraulic drive device according to the present invention. 1 is a hydraulic circuit diagram showing a first embodiment of a hydraulic drive device according to the present invention. It is a figure which shows the structure of the pilot check valve shown in FIG. It is a 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. 5 is a table showing a list of control items used in a lift lowering operation in the controller shown in FIG. 4. It is a flowchart which shows the detail of the control processing procedure of the electromagnetic switching valve for pilots shown in FIG. It is a block diagram which shows the detail of the motor torque output processing procedure shown in FIG. It is a figure which shows the timing chart in the case of performing lift descent single operation in the state (heavy load state) with a large load. It is a figure which shows the timing chart in the case of performing lift descent single operation in the state (light load state) with a small load. It is a figure which shows a timing chart in the case of performing simultaneous operation of lift lowering and tilting in a state where the load is large (heavy load state). It is a figure which shows the timing chart in the case of performing simultaneous operation of a lift descent | fall and a tilt in the state where a load load is small (light load state). It is a block diagram which shows the control system of 2nd Embodiment of the hydraulic drive device which concerns on this invention. 14 is a table showing a list of control items used in a lift lowering operation in the controller shown in FIG. 13. It is a flowchart which shows the detail of the power running torque limit value setting process procedure performed by the controller shown in FIG. It is a figure which shows the time chart of the rotation speed of an electric motor when a power running torque limit value setting process procedure shown in FIG. 15 is performed, and a power running torque limit value. It is a flowchart which shows the modification of the power running torque limit value setting process procedure shown in FIG. It is a figure which shows the time chart of the rotation speed of an electric motor when a power running torque limit value setting process procedure shown in FIG. 17 is performed, and a power running torque limit value. It is a block diagram which shows the structure of a part of controller in 3rd Embodiment of the hydraulic drive device which concerns on this invention. 20 is a table showing a list of control items used in the lift lowering operation in the controller shown in FIG. It is a figure which shows the time chart of the rotation speed of an electric motor, and a power running torque limitation value when a power running torque limitation value is set by the torque limitation value setting part shown in FIG. It is a hydraulic circuit diagram which shows 4th Embodiment of the hydraulic drive device which concerns on this invention. It is a flowchart which shows the detail of the control processing procedure of the electromagnetic proportional valve performed by the controller shown in FIG.

  Hereinafter, embodiments of the present 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 provided with a first embodiment of a hydraulic drive apparatus according to the present invention. In the figure, a cargo handling vehicle 1 according to the present embodiment is a battery-type forklift. The forklift 1 includes a body frame 2 and a mast 3 disposed at the front 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 forklift 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 forklift 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 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 rod chamber 14a and the bottom 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 fluid to flow from the hydraulic pump motor 17 to the rod chamber 14a of the PS cylinder 14, and the hydraulic fluid flows from the hydraulic pump motor 17 to the bottom chamber 14b of the PS cylinder 14. Is switched between an open position 36b that permits the hydraulic fluid and a closed position 36c that blocks the flow of hydraulic oil 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 47. The hydraulic piping 47 constitutes a first hydraulic fluid passage for sending hydraulic fluid from the lift cylinder 4 to the hydraulic pump motor 17.

  The hydraulic piping 47 is provided with an electromagnetic proportional valve 48 for lowering the lift. 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 the closed position 48b (illustrated), and an operation signal (a lift lowering solenoid current command value corresponding to the operation amount of the lowering operation of the lift operation lever 11) is input to the solenoid operation 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 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 49. That is, the hydraulic pipe 49 connects the hydraulic pipe 47 and the tank 19. The hydraulic pipe 49 constitutes a bypass hydraulic oil passage (second hydraulic oil passage) for returning the hydraulic oil from the lift cylinder 4 to the tank 19.

  The hydraulic pipe 49 is provided with a flow rate control valve 50 with a pressure compensation function for controlling the flow rate of the hydraulic oil returning from the lift cylinder 4 to the tank 19. The flow control valve 50 is a pilot flow control valve that opens at an opening degree corresponding to the pilot pressure. A filter 51 is provided between the flow control valve 50 and the tank 19 in the hydraulic piping 49.

  The flow control valve 50 is switched between an open position 50a that allows the flow of hydraulic oil, a closed position 50b that blocks the flow of hydraulic oil, and a throttle position 50c that adjusts the flow of hydraulic oil. A pilot operating part on the closed position 50 b side of the flow control valve 50 and the upstream side of the electromagnetic proportional valve 48 in the hydraulic piping 47 are connected via a pilot flow path 52. A pilot operating portion on the open position 50 a side of the flow control valve 50 and the upstream side of the flow control valve 50 in the hydraulic piping 49 are connected via a pilot flow path 53.

  The flow control valve 50 opens at an opening degree corresponding to a pressure difference (differential pressure) between the pressure upstream of the electromagnetic proportional valve 48 in the hydraulic piping 47 and the pressure upstream of the flow control valve 50 in the hydraulic piping 49. Specifically, the flow control valve 50 is normally in the open position 50a (shown). As the differential pressure between the upstream pressure of the electromagnetic proportional valve 48 in the hydraulic piping 47 and the upstream pressure of the flow control valve 50 in the hydraulic piping 49 increases, the opening degree of the flow control valve 50 decreases.

  A pilot check valve 54 that allows hydraulic oil to pass only in a direction returning to the tank 19 is disposed upstream of the flow control valve 50 in the hydraulic piping 49. The pilot check valve 54 and the downstream side of the flow rate control valve 50 in the hydraulic piping 49 are connected via a pilot channel 55. On the pilot flow path 55, a pilot electromagnetic switching valve 56 is disposed. The pilot electromagnetic switching valve 56 is an on-off valve that is switched to the open position 56a or the closed position 56b. The pilot electromagnetic switching valve 56 is normally in a closed position 56b (illustrated), and is switched to an open position 56a when an ON signal is input to the solenoid operating portion 56c.

  As shown in FIG. 3, the pilot check valve 54 includes a plunger 57 that opens and closes a flow path between the electromagnetic proportional valve 48 and the flow control valve 50, and a flow path between the electromagnetic proportional valve 48 and the flow control valve 50. And a spring 58 that urges the plunger 57 in the closing direction. The plunger 57 is formed with an orifice 57 a for supplying hydraulic oil from the lift cylinder 4 to the pilot flow path 55.

  When the fork 6 is lowered (lift-down operation), the electromagnetic proportional valve 48 is switched from the closed position 48b to the open position 48a, and the pilot electromagnetic switching valve 56 is switched from the closed position 56b to the open position 56a. Then, as described above, the fork 6 is lowered by its own weight, and the lift cylinder 4 is contracted. At this time, immediately after opening the pilot electromagnetic switching valve 56, the hydraulic oil from the lift cylinder 4 returns to the tank 19 through the orifice 57a of the pilot check valve 54 and the pilot flow path 55 (see arrow A).

  When the flow rate of the hydraulic oil passing through the orifice 57a increases, the plunger 57 resists the biasing force of the spring 58 by the pressure difference (differential pressure) between the pressure upstream of the orifice 57a and the pressure downstream of the orifice 57a. Is pushed up, the flow path between the electromagnetic proportional valve 48 and the flow control valve 50 opens. As a result, the hydraulic oil from the lift cylinder 4 passes through the pilot check valve 54 and the flow rate control valve 50 and returns to the tank 19 (see arrow B).

  Thus, the opening degree of the pilot check valve 54 is the differential pressure between the pressure upstream of the orifice 57a (upstream of the pilot check valve 54 in the hydraulic piping 49) and the pressure downstream of the orifice 57a (pilot flow path 55). That is, it is determined by the differential pressure between the pressure on the upstream side of the flow control valve 50 and the pressure on the downstream side of the flow control valve 50 (the differential pressure across the flow control valve 50). In other words, the differential pressure before and after the flow rate control valve 50 is used as the differential pressure for opening the pilot check valve 54.

  FIG. 4 is a configuration diagram showing a control system of the hydraulic drive device 16. In the figure, the hydraulic drive device 16 includes a controller 60, a lift operation lever operation amount sensor 61 that detects the operation amount of the lift operation lever 11, and a tilt operation lever operation amount sensor 62 that detects the operation amount of the tilt operation lever 12. An attachment operation lever operation amount sensor 63 for detecting an operation amount of an attachment operation lever (not shown), a steering operation speed sensor 64 for detecting the operation speed of the steering wheel 13, and an actual rotational speed (motor actual speed) of the electric motor 18. A rotation speed sensor 65 for detecting the rotation speed).

  The controller 60 inputs detection values of the operation lever operation amount sensors 61 to 63, the steering operation speed sensor 64, and the rotation speed sensor 65, performs predetermined processing, and performs the electric motor 18, the electromagnetic proportional valves 23, 26, 31, 36. , 48 and the pilot electromagnetic switching valve 56 are controlled.

  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 (lift 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 61 to 63, and the operation speed of the steering wheel 13 detected by the steering operation speed sensor 64. Is acquired (procedure S101).

  Subsequently, the lift 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). The lift lowering mode includes lift lowering single operation, lift lowering + tilt operation, lift lowering + attachment operation, lift lowering + power steering operation, lift 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 lift lowering mode determined in step S102. A command value is obtained (procedure S103). The solenoid proportional valve solenoid current command value includes a lift 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, the required motor speed for the operation condition obtained in step S102 is obtained (step S104). The required motor 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, a motor rotation speed command value (motor command rotation speed) is set based on the lift lowering mode determined in step S102 and the required motor rotation speed obtained in step S104 (step S105). At this time, the motor command rotational speed is as shown in FIG. Specifically, in the case of the lift lowering single operation, the motor command rotational speed is set as the lift required motor rotational speed N_lift. In the case of lift lowering + tilt operation, the motor command rotational speed is set to the tilt required motor rotational speed N_tilt. In the case of lift lowering + attachment operation, the motor command rotational speed is set as the attachment required motor rotational speed N_atmt. In the case of lift lowering + power steering operation, the motor command rotational speed is set to PS required motor rotational speed N_ps. In the case of lift lowering + tilt + power steering operation, the motor command rotational speed is set to the maximum value of the tilt required motor rotational speed N_tilt and the PS required motor rotational speed N_ps.

  Subsequently, the power running torque limit value of the electric motor 18 is set based on the lift lowering mode determined in step S102 (step S106). The power running torque limit value is an allowable power running torque value. As shown in FIG. 6, in the case of the lift lowering single operation, the power running torque limit is turned ON. At this time, the power running torque limit value is set to 0 Nm (0%) or a value close thereto, for example. In the case of lift lowering + tilt operation, lift lowering + attachment operation, lift lowering + power steering operation, lift lowering + tilt + power steering operation, the power running torque limit is turned OFF. That is, the power running torque limit value at this time is set to 100%.

  Subsequently, on the basis of the lift lowering mode determined in step S102, the motor command rotational speed set in step S105, and the actual motor rotational speed detected by the rotational speed sensor 65, the pilot electromagnetic switching valve 56 is opened and closed ( ON / OFF) operation is controlled. The details of the control processing procedure of the pilot electromagnetic switching valve 56 are shown in FIG.

  In FIG. 7, it is first determined whether or not the lift lowering mode is a lift lowering single operation (step S111). When it is determined that the lift lowering mode is the lift lowering single operation, the actual motor rotation speed detected by the rotation speed sensor 65 is acquired (step S112).

  Subsequently, it is determined whether or not the difference between the motor command rotational speed set in step S105 (see FIG. 4) and the actual motor rotational speed is equal to or greater than a certain value N (procedure S113). When it is determined that the difference between the motor command rotational speed and the motor actual rotational speed is equal to or greater than a predetermined value N, an ON signal is sent to the solenoid operation portion 56c of the pilot electromagnetic switching valve 56 to thereby switch the pilot electromagnetic switching. The valve 56 is set to the open position 56a (ON) (step S114). When it is determined that the difference between the motor command rotational speed and the motor actual rotational speed is not equal to or greater than a certain value N, an OFF signal is sent to the solenoid operating portion 56c of the pilot electromagnetic switching valve 56, thereby the pilot electromagnetic switching valve. 56 is set to the closed position 56b (OFF) (step S115).

  In step S111, the lift lowering mode is not the lift lowering single operation, that is, the lift lowering mode is any one of lift lowering + tilt operation, lift lowering + attachment operation, lift lowering + power steering operation, lift lowering + tilt + power steering operation. 6, the pilot electromagnetic switching valve 56 is turned on by sending an ON signal to the solenoid operating portion 56c of the pilot electromagnetic switching valve 56 as shown in FIG. 6 (step S114). ).

  In this process, when the difference between the motor command rotation speed and the motor actual rotation speed is equal to or greater than a certain value N, the pilot electromagnetic switching valve 56 is turned ON, and the difference between the motor command rotation speed and the motor actual rotation speed is set. Is not equal to or greater than a certain value N, the pilot electromagnetic switching valve 56 is turned off. For example, in order to prevent chattering, when the difference between the motor command rotation speed and the motor actual rotation speed is equal to or greater than a predetermined value N_on, the pilot electromagnetic switching valve 56 is turned ON, and the motor command rotation speed and the motor actual rotation speed are When the difference is equal to or less than a certain value N_off (<N_on), the pilot electromagnetic switching valve 56 may be turned off.

  Returning to FIG. 5, after performing step S107, the electromagnetic proportional valve solenoid current command value obtained in step S103 is sent to the solenoid operation portion of the corresponding electromagnetic proportional valve (step S108). At this time, the lift 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 65, 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 S109). The process of step S109 is executed by a motor torque output unit 66 included in the controller 60, as shown in FIG.

  In FIG. 8, the motor torque output unit 66 includes a comparison unit 67, a PID calculation unit 68, an output torque determination unit 69, and a motor control unit 70. The comparison unit 67 calculates a rotational speed deviation between the motor command rotational speed set in step S <b> 105 and the actual motor rotational speed detected by the rotational speed sensor 65. The PID calculation unit 68 performs a PID calculation of a rotational speed deviation between the motor command rotational speed and the motor actual rotational speed, and obtains a powering torque command value of the electric motor 18 such that the rotational speed deviation becomes zero. The PID calculation is a combination of a proportional operation, an integral operation, and a derivative operation.

  The output torque determination unit 69 compares the power running torque command value obtained by the PID calculation unit 68 with the power running torque limit value of the electric motor 18 set in step S106, and determines the output torque of the electric motor 18. 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 70 converts the output torque determined by the output torque determination unit 69 into a current signal and sends it to the electric motor 18.

  In the above, the lift operation lever operation amount sensor 61, the tilt operation lever operation amount sensor 62, the attachment operation lever operation amount sensor 63, the steering operation speed sensor 64, and the controller 60 are set means for setting the command rotational speed of the electric motor 18, and The determination means determines whether or not the lowering operation of the elevating operation means 11 is performed alone and whether or not the operations of the plurality of manual operation means including the lowering operation of the elevating operation means 11 are performed simultaneously. The controller 60 constitutes electric motor control means for controlling the electric motor 18 based on the command rotational speed set by the setting means and the actual rotational speed detected by the rotational speed detection means 65.

  Further, when it is determined by the determination means that the lowering operation of the elevating operation means 11 has been performed alone, the controller 60 is detected by the command rotational speed of the electric motor 18 and the rotational speed detection means 65 set by the setting means. When the difference from the actual rotational speed of the electric motor 18 is equal to or greater than a predetermined value, the valve means 56 is controlled to be switched to the open position 56a, and the determination means includes a plurality of manual operation means including the lowering operation of the elevating operation means 11. When it is determined that the operations are performed simultaneously, a valve opening / closing control unit is configured to control the valve unit 56 so as to switch to the open position 56a unconditionally.

  Further, the controller 60 limits the power running torque of the electric motor 18 when the determination unit determines that the lowering operation of the lifting operation unit 11 is performed alone, and includes a plurality of operations including the lowering operation of the lifting operation unit 11 by the determination unit. When it is determined that the manual operation means are simultaneously operated, torque limiting control means for releasing the restriction of the power running torque of the electric motor 18 is configured.

  Here, steps S101 and S102 shown in FIG. 5 function as a part of the determination unit. The procedures S101 and S103 to S105 function as a part of setting means. The procedure S106 functions as torque limit control means. The procedure S107 functions as a valve opening / closing control means. The procedure S109 functions as an electric motor control unit.

  Next, the operation of the hydraulic drive device 16 of this embodiment will be described with reference to FIGS. FIG. 9 is a timing chart when the lift lowering single operation is performed in a state where the load load of the fork 6 is large (heavy load state).

In FIG. 9, first, at time t1, since the lift lowering single operation is started, the power running torque limit of the electric motor 18 is turned ON. Further, a lift lowering solenoid current command value (see broken line B) corresponding to the operation amount of the lift operation lever 11 (see solid line A) is obtained, and the current command value is output to the electromagnetic proportional valve 48. Then, the electromagnetic proportional valve 48 is switched from the closed position 48b to the open position 48a. At this time, since the load load of the fork 6 is large, the differential pressure between the pressure upstream of the electromagnetic proportional valve 48 in the hydraulic piping 47 and the pressure upstream of the flow control valve 50 in the hydraulic piping 49 increases, and the flow control valve 50 is switched from the open position 50a to the closed position 50b. The lift required motor speed corresponding to the lift lowering solenoid current command value is obtained as the motor command speed (see the broken line C ₀ ), and the motor command speed is output to the electric motor 18.

  Thereafter, at time t2, when the difference between the motor command rotational speed and the actual motor rotational speed (see the solid line C) becomes a certain value N or more, the pilot electromagnetic switching valve 56 is turned on (see the solid line D). At this time, since the hydraulic pump motor 17 is rotated by the suction pressure of the hydraulic pump motor 17, the actual motor rotation speed approaches the motor command rotation speed.

  At a subsequent time t3, the difference between the motor command rotational speed and the motor actual rotational speed is smaller than a certain value N, so that the pilot electromagnetic switching valve 56 is turned OFF (see solid line D). Then, the flow rate (bypass flow rate) Q3 of the hydraulic oil that returns to the tank 19 becomes 0, and the flow rate Q1 of the hydraulic fluid from the lift cylinder 4 becomes all the flow rate Q2 of the hydraulic fluid supplied to the hydraulic pump motor 17. Accordingly, the hydraulic pump motor 17 can easily operate as a hydraulic motor, and the electric motor 18 functions as a generator. Thereby, the cargo handling regeneration mentioned above can be performed efficiently.

  FIG. 10 is a timing chart when the lift lowering single operation is performed in a state where the load load of the fork 6 is small (light load state).

In FIG. 10, first, at time t1, since the lift lowering single operation is started, the power running torque limitation of the electric motor 18 is turned ON. Further, a lift lowering solenoid current command value (see broken line B) corresponding to the operation amount of the lift operation lever 11 (see solid line A) is obtained, and the current command value is output to the electromagnetic proportional valve 48. Then, the electromagnetic proportional valve 48 is switched from the closed position 48b to the open position 48a. At this time, since the load load of the fork 6 is small, the differential pressure between the upstream pressure of the electromagnetic proportional valve 48 in the hydraulic piping 47 and the upstream pressure of the flow control valve 50 in the hydraulic piping 49 is small. Is open. The lift required motor speed corresponding to the lift lowering solenoid current command value is obtained as the motor command speed (see the broken line C ₀ ), and the motor command speed is output to the electric motor 18.

  Thereafter, at time t2, when the difference between the motor command rotational speed and the actual motor rotational speed (see the solid line C) becomes a certain value N or more, the pilot electromagnetic switching valve 56 is turned on (see the solid line D). At this time, since the suction pressure of the hydraulic pump motor 17 is low, the hydraulic pump motor 17 is not rotated, and the actual motor rotation speed does not reach the motor command rotation speed. For this reason, the pilot electromagnetic switching valve 56 is maintained in the ON state.

  In this state, the opening degree of the flow control valve 50 increases until the hydraulic oil bypass flow rate Q3 returning to the tank 19 reaches a required amount. Then, the necessary amount of hydraulic fluid Q1 from the lift cylinder 4 is secured. Thereby, a necessary lift lowering speed can be ensured. Further, since the electric motor 18 is not powered, the power consumption can be kept low.

  FIG. 11 is a timing chart in the case where simultaneous operation of lift lowering and tilting is performed in a state where the load load of the fork 6 is large (heavy load state). In FIG. 11, the operation at times t1 to t3 is the same as that shown in FIG.

At subsequent time t4, since the tilt operation is started, the power running torque limit of the electric motor 18 is turned OFF, and the pilot electromagnetic switching valve 56 is turned ON from OFF (see the solid line D). Then, a tilt solenoid current command value corresponding to the operation amount of the tilt operation lever 12 (see the solid line E) is obtained, and the current command value is output to the electromagnetic proportional valve 26. Then, the electromagnetic proportional valve 26 is switched from the closed position 26c to any one of the open positions 26a and 26b. Then, the tilt required motor rotational speed corresponding to the tilt solenoid current command value is obtained as the motor command rotational speed (see the broken line C ₀ ), and the motor command rotational speed is output to the electric motor 18.

  At this time, since the power running torque limit of the electric motor 18 is OFF, the actual motor rotation speed follows the motor command rotation speed. Depending on the load, it is possible to perform cargo handling regeneration.

  Here, since the motor command rotational speed decreases from the lift required motor rotational speed to the tilt required motor rotational speed, the actual motor rotational speed decreases. For this reason, the flow rate Q2 of the hydraulic oil supplied to the hydraulic pump motor 17 is reduced. Then, the flow control valve 50 opens until it reaches an opening that can compensate for the decreased flow Q2. Accordingly, the hydraulic oil bypass flow rate Q3 returning to the tank 19 increases, and the hydraulic oil flow rate Q1 from the lift cylinder 4 becomes substantially constant. Thereby, even if simultaneous operation of lift lowering and tilting is performed, the lift lowering speed can be kept constant. Further, the lift lowering operation and the tilting operation can be performed at the same time by utilizing the regenerative energy of the load to the maximum.

  FIG. 12 is a diagram showing a timing chart in the case where simultaneous operations of lift lowering and tilting are performed in a state where the load load of the fork 6 is small (light load state). In FIG. 12, operations at times t1 and t2 are the same as those shown in FIG.

At a subsequent time t4, since the tilt operation is started, the power running torque limit of the electric motor 18 is turned off, and the pilot electromagnetic switching valve 56 is kept on (see the solid line D). Then, a tilt solenoid current command value corresponding to the operation amount of the tilt operation lever 12 is obtained, and the current command value is output to the electromagnetic proportional valve 26. Then, the electromagnetic proportional valve 26 is switched from the closed position 26c to any one of the open positions 26a and 26b. Then, the tilt required motor rotational speed corresponding to the tilt solenoid current command value is obtained as the motor command rotational speed (see the broken line C ₀ ), and the motor command rotational speed is output to the electric motor 18.

  At this time, since the power running torque limit of the electric motor 18 is OFF, the actual motor rotation speed follows the motor command rotation speed. Depending on the load, it is possible to perform cargo handling regeneration.

  Here, since the actual motor speed has not reached the motor command speed before time t4, the actual motor speed increases (see solid line C). For this reason, the flow rate Q2 of the hydraulic oil supplied to the hydraulic pump motor 17 increases. Then, since the opening degree of the flow control valve 50 is reduced so as to reduce the bypass flow Q3 of the hydraulic oil that returns to the tank 19 by the increased flow Q2, the flow Q1 of the hydraulic oil from the lift cylinder 4 becomes substantially constant. Become. Thereby, even if simultaneous operation of lift lowering and tilting is performed, the lift lowering speed can be kept constant.

  Note that the operations for simultaneous operation of lift lowering and attachment, and for simultaneous operation of lift lowering and power steering are substantially the same as those for simultaneous operation of lift lowering and tilt.

  As described above, in the present embodiment, the hydraulic pump motor 17 and the lift cylinder 4 are connected by the hydraulic piping 47, the hydraulic piping 47 and the tank 19 are connected by the hydraulic piping 49, and flow control is performed on the hydraulic piping 49. A valve 50 is provided, a pilot check valve 54 is provided on the upstream side of the flow control valve 50 in the hydraulic pipe 49, and a pilot flow path 55 is provided between the pilot check valve 54 and the downstream side of the flow control valve 50 in the hydraulic pipe 49. The pilot electromagnetic switching valve 56 is disposed on the pilot flow path 55.

  With this configuration, the differential pressure for opening the pilot check valve 54 (opening differential pressure of the pilot check valve 54) is the pressure upstream of the flow control valve 50 and the pressure downstream of the flow control valve 50 (tank The pressure difference is equivalent to the pressure). For this reason, compared with the case where the flow control valve 50 is provided upstream of the pilot check valve 54 in the hydraulic piping 49, the valve opening differential pressure of the pilot check valve 54 is increased by the amount that pressure loss due to the flow control valve 50 does not occur. growing. Therefore, the opening degree of the pilot check valve 54 is increased, and the pressure loss of the hydraulic oil flowing through the hydraulic pipe 49 is reduced. As a result, when the lift lowering operation is performed at a light load, the flow rate of the working oil returning to the tank 19 increases, so that the lift lowering speed can be increased.

  Further, in the present embodiment, during the lift-down single operation in the heavy load state, the entire flow rate of the hydraulic oil from the lift cylinder 4 is sent to the hydraulic pump motor 17, so that cargo handling regeneration can be performed with high efficiency. In addition, during the lift lowering single operation in a light load state, most of the flow rate of the hydraulic oil from the lift cylinder 4 returns to the tank 19, so that the necessary lift lowering speed can be ensured with the minimum necessary power.

  Further, during lift lowering alone operation, even if the load can be regenerated when the lift lowering speed is low, if the lift lowering speed becomes high, the pressure of the hydraulic oil is reduced to a pressure that cannot be regenerated. However, in this case, most of the flow rate of the hydraulic oil from the lift cylinder 4 returns to the tank 19, so that the electric motor 18 is not powered and the power consumption can be reduced.

  Furthermore, even when other cargo handling operations such as tilting and attachment or steering operations are performed during the lift lowering operation, a part of the flow rate of the hydraulic oil from the lift cylinder 4 returns to the tank 19, so that the fluctuation of the lift lowering speed is changed. Can be suppressed. In addition, depending on the load and the amount of operation of the operation lever, it is possible to perform other cargo handling operations or steering operations by making maximum use of the regenerative energy of the load, so that power consumption can be reduced.

  In addition, when the lift lowering operation and other cargo handling operation or steering operation are performed simultaneously, the lift required motor speed may be higher than the tilt required motor speed, the attachment required motor speed, and the power steering required motor speed. The required motor speed other than the lift required motor speed is set as the motor command speed. For this reason, since it is prevented that the hydraulic fluid more than necessary is supplied to the tilt cylinder 9, the attachment cylinder 15, and the PS cylinder 14, an increase in loss can be prevented.

  Further, the flow rate control with a pressure compensation function that reduces the speed change even if the pressure difference between the upstream pressure of the electromagnetic proportional valve 48 in the hydraulic piping 47 and the upstream pressure of the flow control valve 50 in the hydraulic piping 49 fluctuates. Since the valve 50 is used, fluctuations in the lift lowering speed due to fluctuations in the load can be suppressed.

  Further, whether the pilot electromagnetic switching valve 56 is ON / OFF is determined based on whether or not the difference between the motor command rotational speed and the motor actual rotational speed is equal to or greater than a predetermined value N. Therefore, a pressure sensor, a stroke sensor, and the like are required. You don't have to. Further, it is not necessary to provide a plurality of hydraulic pump motors 17 and electric motors 18. In addition, an inexpensive pilot flow control valve is used as the flow control valve 50. Therefore, the hydraulic drive device 16 can be configured at low cost.

  FIG. 13 is a block diagram showing a control system of the second embodiment of the hydraulic drive apparatus according to the present invention. In the figure, the hydraulic drive device 16 of this embodiment further includes a direction sensor 75 in addition to the configuration shown in FIG.

  The direction sensor 75 is a sensor that detects the traveling direction (forward / reverse / neutral) of the forklift 1 selected and operated by the direction switch (described above). When the direction switch is switched forward or backward, the direction sensor 75 is turned on. When the direction switch is switched to neutral, the direction sensor 75 is turned off.

  The controller 60 inputs the detection values of the operation lever operation amount sensors 61 to 63, the steering operation speed sensor 64 and the rotation speed sensor 65, and the detection signal of the direction sensor 75, performs predetermined processing, and performs the electric motor 18, electromagnetic proportionality. The valves 23, 26, 31, 36, 48 and the pilot electromagnetic switching valve 56 are controlled. The controller 60 executes control processing of operations including lift lowering according to steps S101 to S109 shown in FIG. The processing in steps S101 to S104 is the same as that in the first embodiment.

  The motor command rotation speed (motor rotation speed command value) set in step S105 is as shown in FIG. Specifically, when the direction sensor 75 is OFF, the motor command rotational speed is the same as that in the above embodiment for all lift lowering modes. When the direction sensor 75 is ON and the lift lowering single operation is performed, the motor command rotation speed is set to the maximum value of the lift required motor rotation speed N_lift and the PS idle rotation speed N_psi. Note that the idle speed N_psi for PS is obtained in advance through experiments or the like. When the direction sensor 75 is ON and in another lift lowering mode, the motor command rotational speed is the same as that in the first embodiment.

  Subsequently, the power running torque limit value of the electric motor 18 set in step S106 is set by binary control as shown in FIG. FIG. 15 shows details of the procedure for setting the power running torque limit value of the electric motor 18.

  In FIG. 15, it is first determined whether or not the lift lowering mode is a lift lowering single operation (step S121). When it is determined that the lift lowering mode is the lift lowering single operation, it is determined whether or not the direction sensor 75 is ON (step S122). When it is determined that the direction sensor 75 is ON, the actual motor rotation speed detected by the rotation speed sensor 65 is acquired (step S123).

Subsequently, it is determined whether the actual motor rotation speed is equal to or higher than the idle rotation speed (step S124). When it is determined that the actual motor speed is equal to or higher than the idle speed, the power running torque limit value of the electric motor 18 is set to the minimum set value S _L (see FIG. 16) (step S125). At this time, the minimum set value S _L (first set value) is a value (torque) that maintains the rotational speed of the hydraulic pump motor 17 at the idle rotational speed even when the hydraulic oil temperature is sufficiently high, for example. It is required by experiments.

When it is determined that the actual motor speed is not equal to or higher than the idle speed, the power running torque limit value of the electric motor 18 is set to the maximum set value S _U (see FIG. 16) (step S126). At this time, the maximum set value S _U (second set value) is larger than the minimum set value S _L , and is obtained through experiments or the like. The maximum set value _SU is a value (torque) necessary for rotating the hydraulic pump motor 17 at the idle rotational speed even when the hydraulic oil temperature is sufficiently low, for example.

  When it is determined in step S122 that the direction sensor 75 is not ON but OFF, the power running torque limit is turned ON as in the first embodiment (step S127). When it is determined in step S121 that the lift lowering mode is not the lift lowering single operation, the power running torque limit is turned off as in the first embodiment (step S128).

In this way, in the present process, when the actual motor rotation speed is an idle rotational speed or more, by setting the power running torque limit value of the electric motor 18 to the minimum set value S _L, the electric motor 18 permits power torque the small, when the actual motor speed is not idle speed or more, the power running torque limit value of the electric motor 18 by setting the maximum set value S _U, to increase the power torque of the electric motor 18 is permitted. As a result, as shown in FIG. 16, when the actual motor speed P cannot follow the motor command speed Q as in the case of a light load with a light load, the motor actual speed P becomes the idle speed. Get closer.

  The subsequent processes in steps S107 to S109 are the same as those in the first embodiment.

  In the above, the procedure S127 shown in FIG. 15 determines that the lowering operation of the lifting operation means has been performed alone by the determination means while the traveling direction detection means 75 detects that the traveling direction of the cargo handling vehicle 1 is neutral. In this case, it functions as first power running torque limit value setting means for setting the power running torque limit value of the electric motor 18 to a predetermined value. In steps S123 to S126, when the traveling direction detection unit 75 detects that the traveling direction of the cargo handling vehicle 1 is moving forward or backward, the determination unit determines that the lowering operation of the lifting operation unit is performed alone. In this case, the power running torque limit value of the electric motor 18 is based on the actual rotational speed detected by the rotational speed detection means 65 and the idle rotational speed of the hydraulic pump 17 or the target rotational speed corresponding to the rotational speed higher than the idle rotational speed. It functions as a second power running torque limit value setting means for setting.

  By the way, when the direction switch (described above) is in a forward or reverse state, it is necessary to rotate the hydraulic pump motor 17 at a rotational speed equal to or higher than the idle rotational speed in preparation for the operation (steering) of the steering wheel 13. On the other hand, as the oil temperature of the hydraulic oil decreases, the viscosity of the hydraulic oil increases and the pressure loss increases. Therefore, the power running torque necessary to rotate the hydraulic pump motor 17 at the number of revolutions equal to or higher than the idle number of revolutions is increased. growing. Therefore, it is necessary to set the power running torque limit value so that the rotational speed of the hydraulic pump motor 17 can be ensured to be equal to or higher than the idle rotational speed when the hydraulic oil temperature is low. However, in this case, since the hydraulic pump motor 17 allows a large power running torque even when the temperature of the hydraulic oil is normal temperature, the rotational speed of the hydraulic pump motor 17 increases more than necessary, and as a result. Power consumption increases.

On the other hand, in the present embodiment, when the direction switch is in the forward or reverse state and the lift lowering single operation is performed, the actual motor rotational speed is compared with the idle rotational speed, and the electric motor 18 is operated according to the comparison result. Since the power running torque limit value is set to the minimum set value S _L or the maximum set value S _U , the rotation speed of the hydraulic pump motor 17 can be brought close to the idle rotation speed regardless of the oil temperature of the hydraulic oil. Thereby, smooth steering can be performed during the lift lowering single operation.

  Further, in a state where the load is light, the hydraulic pump motor 17 rotates at a necessary minimum number of revolutions, i.e., an idling number of revolutions, so that an increase in power consumption can be suppressed. On the other hand, when the load is sufficiently heavy, the hydraulic pump motor 17 rotates at a motor command rotational speed higher than the idle rotational speed, so that cargo handling regeneration can be performed with high efficiency.

  FIG. 17 is a flowchart showing a modification of the powering torque limit value setting processing procedure shown in FIG. This flowchart is different from the flowchart shown in FIG. 15 only in the process of step S124.

In step S124, it is determined whether the actual motor speed is equal to or higher than (idle speed + α). α is a predetermined number of rotations. When it is determined that the actual motor speed is equal to or greater than (idle speed + α), the power running torque limit value of the electric motor 18 is set to the minimum set value S _L (see FIG. 18) (step S125). When it is determined that the rotational speed is not equal to or higher than (idle rotational speed + α), the power running torque limit value of the electric motor 18 is set to the maximum set value S _U (see FIG. 18) (step S126).

  In this modification, the threshold value for switching the power running torque limit value is set to the idle rotation speed + α. Therefore, in the state where the actual motor rotation speed P cannot follow the motor command rotation speed Q as shown in FIG. The rotational speed P approaches the target rotational speed (idle rotational speed + α). Thereby, even if the actual motor rotation speed P pulsates somewhat near the idle rotation speed, the rotation speed of the hydraulic pump motor 17 can be reliably ensured to be equal to or higher than the idle rotation speed.

  FIG. 19 is a block diagram showing a configuration of a part of the controller 60 in the third embodiment of the hydraulic drive apparatus according to the present invention. This embodiment is different from the second embodiment only in the process of step S106 in the flowchart shown in FIG. The process of step S106 is executed by the torque limit value setting unit 80 included in the controller 60. FIG. 19 shows only processing when the direction sensor 75 is ON and the lift lowering mode is the lift lowering single operation, and the other processing is the same as in the second embodiment (FIG. 19). 20).

  The torque limit value setting unit 80 includes a comparison unit 81 and a PID calculation unit 82. The comparison unit 81 calculates a rotational speed deviation between the idle rotational speed and the actual motor rotational speed detected by the rotational speed sensor 65. The PID calculation unit 82 performs a PID calculation of a rotation speed deviation between the idle rotation speed and the actual motor rotation speed, and obtains a power running torque limit value of the electric motor 18 such that the rotation speed deviation becomes zero. The power running torque limit value is sent to the output torque determination unit 69 of the motor torque output unit 66 that executes step S109 shown in FIG.

  Here, the torque limit value setting unit 80 performs the descent operation of the elevating operation unit independently by the determination unit in a state where the traveling direction detection unit 75 detects that the traveling direction of the cargo handling vehicle 1 is forward or backward. When it is determined that the motor 18 is in the engine 18 based on the actual rotational speed detected by the rotational speed detection means 65 and the idle rotational speed of the hydraulic pump 17 or a target rotational speed corresponding to a rotational speed higher than the idle rotational speed. Second power running torque limit value setting means for setting the power running torque limit value is configured.

  Thus, in the present embodiment, when the direction switch is in the forward or reverse state and the lift lowering single operation is performed, the power running torque limit value of the electric motor 18 is set by PID control, as shown in FIG. In a state where the motor actual rotation speed P cannot follow the motor command rotation speed Q, the motor actual rotation speed P is smoothly pulsated to the idle rotation speed without almost pulsating near the idle rotation speed. Follows stably. Therefore, the rotational speed of the hydraulic pump motor 17 can be ensured at the idle rotational speed regardless of the oil temperature of the hydraulic oil. Thereby, smooth steering can be performed during the lift lowering single operation. Further, in a state where the load load is light, the hydraulic pump motor 17 rotates at the minimum necessary number of revolutions, which is the idling number of revolutions, so that an increase in power consumption can be suppressed.

  In this embodiment, the power running torque limit value of the electric motor 18 is PID controlled. However, the present invention is not limited to PID control, and the rotational speed deviation between the idle rotational speed and the actual motor rotational speed is zero. In addition, feedback control such as PI control may be performed.

  FIG. 22 is a hydraulic circuit diagram showing a fourth embodiment of the hydraulic drive apparatus according to the present invention. In the same figure, the hydraulic drive device 16 of this embodiment is provided with an electromagnetic proportional valve 90 for controlling the flow rate of hydraulic oil returning from the lift cylinder 4 to the tank 19 in place of the flow rate control valve 50 in the first embodiment. . The electromagnetic proportional valve 90 is an electromagnetic proportional flow control valve that opens at an opening degree corresponding to the control signal.

  The electromagnetic proportional valve 90 is switched between an open position 90 a that allows the flow of hydraulic oil from the lift cylinder 4 to the tank 19 and a closed position 90 b that blocks the flow of hydraulic oil from the lift cylinder 4 to the tank 19. . The electromagnetic proportional valve 90 is normally in a closed position 90b (illustrated), and when an operation signal (control signal) is input to the solenoid operation unit 90c, the electromagnetic proportional valve 90 is switched to the open position 90a. When the electromagnetic proportional valve 90 is in the open position 90a, the electromagnetic proportional valve 90 is opened at an opening corresponding to the operation signal. The pilot check valve 54 is disposed on the upstream side of the electromagnetic proportional valve 90 in the hydraulic piping 49. The pilot flow path 55 connects the pilot check valve 54 and the downstream side of the electromagnetic proportional valve 90 in the hydraulic piping 49. On the pilot flow path 55, a pilot electromagnetic switching valve 56 is disposed.

  The hydraulic drive device 16 further includes a pressure sensor 91 that detects the pressure in the bottom chamber 4 b of the lift cylinder 4, and a controller 92 that is connected to the pressure sensor 91. The controller 92 controls the electromagnetic proportional valve 90 based on the detection value of the pressure sensor 91. Details of the control processing procedure of the electromagnetic proportional valve 90 by the controller 92 are shown in FIG.

  In FIG. 23, first, the detection value of the pressure sensor 91 is input (step S131). Subsequently, the load (load) of the fork 6 is obtained based on the detected value of the pressure sensor 91 and the diameter of the lift cylinder 4 (step S132). Subsequently, an operation signal corresponding to the loaded load of the fork 6 is output to the solenoid operation unit 90c of the electromagnetic proportional valve 90 (step S133). At this time, the controller 92 sets an operation signal such that the opening degree of the electromagnetic proportional valve 90 increases as the load on the fork 6 decreases (the load decreases).

  Thus, in this embodiment, the valve opening differential pressure of the pilot check valve 54 is determined by the differential pressure between the pressure on the upstream side of the electromagnetic proportional valve 90 and the pressure on the downstream side of the electromagnetic proportional valve 90 (corresponding to the tank pressure). Will be obtained. Accordingly, as in the first embodiment, the opening degree of the pilot check valve 54 is increased, and the pressure loss of the hydraulic oil flowing through the hydraulic piping 49 is reduced. As a result, when the lift lowering operation is performed at a light load, the flow rate of the working oil returning to the tank 19 increases, so that the lift lowering speed can be increased. Moreover, the lift lowering speed can be smoothly controlled by using the electromagnetic proportional valve 90 as a flow control valve.

  In this embodiment, the controller 92 different from the controller 60 is used. However, the electromagnetic proportional valve 90 may be controlled by the controller 60 as a matter of course. In this embodiment, the electromagnetic proportional valve 90 is used. However, as the flow control valve, a mechanical proportional valve capable of mechanically changing the opening degree may be used instead of the electromagnetic proportional valve 90. .

  Although several embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. For example, in the above 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 ... Forklift (loading vehicle), 4 ... Lift cylinder (hydraulic cylinder), 4b ... Bottom chamber, 6 ... Fork (lifting object), 16 ... Hydraulic drive device, 17 ... Hydraulic pump motor (hydraulic pump), 17a ... Suction port , 19 ... Tank, 47 ... Hydraulic piping (first hydraulic fluid passage), 49 ... Hydraulic piping (second hydraulic fluid passage), 50 ... Flow control valve, 54 ... Pilot check valve, 55 ... Pilot passage, 56 ... Electromagnetic switching valve for pilot (open / close valve), 90 ... Electromagnetic proportional valve (flow control valve).

Claims (6)

In a hydraulic drive device for a cargo handling vehicle having a plurality of hydraulic cylinders including a lift cylinder that raises and lowers a lift by supplying and discharging hydraulic oil,
A tank for storing the hydraulic oil;
A hydraulic pump that sucks the hydraulic oil from the tank and supplies the hydraulic oil to the hydraulic cylinder;
A first hydraulic oil passage for connecting the suction port of the hydraulic pump and a bottom chamber of the lift cylinder, and for sending the hydraulic oil from the lift cylinder to the hydraulic pump;
An electromagnetic proportional valve disposed on the first hydraulic fluid passage;
A second hydraulic oil passage for connecting the downstream side of the electromagnetic proportional valve in the first hydraulic oil passage and the tank, and returning the hydraulic oil from the lift cylinder to the tank;
A flow rate control valve that is disposed on the second hydraulic oil flow path and controls the flow rate of the hydraulic oil returning from the lift cylinder to the tank;
A pilot check valve disposed on the upstream side of the flow rate control valve on the second hydraulic oil flow path and allowing the hydraulic oil to pass only in a direction returning to the tank;
A pilot flow path connecting the pilot check valve and the downstream side of the flow rate control valve in the second hydraulic oil flow path;
An on-off valve disposed on the pilot flow path ;
A valve opening / closing control means for controlling the valve to open when the lifting object is lowered in a light load state where the load load of the lifting object is smaller than a predetermined value ;
The opening of the pilot check valve is upstream of the pilot check valve in the second hydraulic fluid passage corresponding to a differential pressure between the pressure upstream of the flow control valve and the pressure downstream of the flow control valve. A hydraulic drive apparatus for a cargo handling vehicle, wherein the pressure difference increases as the differential pressure between the pressure in the pilot flow path and the pressure in the pilot flow path increases . The pilot check valve includes a plunger that opens and closes a flow path between the electromagnetic proportional valve and the flow control valve, and a plunger that closes the flow path between the electromagnetic proportional valve and the flow control valve. And a spring
  The plunger is formed with an orifice for supplying hydraulic oil from the lift cylinder to the pilot flow path,
  2. The hydraulic drive system for a cargo handling vehicle according to claim 1, wherein the opening degree of the pilot check valve increases as the differential pressure between the pressure upstream of the orifice and the pressure downstream of the orifice increases. A plurality of manual operation means for operating each of the plurality of hydraulic cylinders; and having a lift operation means for operating the lift cylinder to raise and lower the lift.
  An electric motor for driving the hydraulic pump;
  Setting means for setting a command rotational speed of the electric motor based on an operation state of the plurality of manual operation means;
  A rotational speed detection means for detecting the actual rotational speed of the electric motor;
  The valve opening / closing control means is detected by the commanded rotational speed of the electric motor set by the setting means and the rotational speed detection means when the lifting / lowering operation means is operated alone to lower the lifted object. 3. The hydraulic drive apparatus for a cargo handling vehicle according to claim 1, wherein the on-off valve is controlled to open when a difference from an actual rotational speed of the electric motor is not less than a predetermined value. 4. . The valve opening / closing control means controls to open the opening / closing valve unconditionally when the operations of the plurality of manual operation means including the operation of lowering the lifted object by the elevating operation means are performed simultaneously. The hydraulic drive apparatus for a cargo handling vehicle according to claim 3, wherein: The hydraulic drive apparatus for a cargo handling vehicle according to any one of claims 1 to 4, wherein the flow control valve is a pilot-type flow control valve that opens at an opening degree corresponding to a pilot pressure. The hydraulic drive apparatus for a cargo handling vehicle according to any one of claims 1 to 4, wherein the flow control valve is an electromagnetic proportional flow control valve that opens at an opening degree corresponding to a control signal.

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