JP5883616B2 - Electric motor control device - Google Patents

Description

  The present invention relates to an electric motor control device.

  Japanese Patent Application Laid-Open No. 2004-228561 discloses a fixed displacement pump that supplies hydraulic oil to an actuator that moves a fork of a forklift up and down or tilts forward and backward by an electric motor.

Japanese Patent Laid-Open No. 8-1333697

  However, in Patent Document 1, the amount of hydraulic oil supplied to the actuator is controlled by controlling the rotation speed of the electric motor in accordance with the amount of operation of the lever that switches the position of the spool (control valve). For this reason, for example, when the viscosity changes due to the temperature change of the hydraulic oil and the volumetric efficiency of the pump changes, there is a problem that the actuator cannot be driven at a speed corresponding to the operation amount of the lever.

  The present invention has been made paying attention to such problems, and an object of the present invention is to drive an actuator at a speed corresponding to an operation amount of a lever while using a fixed displacement pump.

The present invention is an electric motor control device that controls the rotational speed of an electric motor mounted on an industrial vehicle, and is a pump that is driven by the electric motor and discharges a working fluid at a flow rate corresponding to the rotational speed of the electric motor. , At least one actuator driven by the working fluid discharged from the pump, a cut-off control valve for switching supply / discharge of the working fluid to / from the actuator, and the highest one of the load pressures of the actuator that guides the highest load pressure as the highest load pressure A load pressure detection circuit. The electric motor control device is driven by the working fluid discharged from the pump, and controls a steering actuator that controls the steering angle of the wheels of the industrial vehicle, and steering control that switches between supply and discharge of the working fluid to the steering actuator according to the steering operation. A valve, a discharge pressure detection means for detecting the discharge pressure of the pump, a maximum load pressure detection means for detecting the load pressure of the maximum load pressure detection circuit, and a steering operation amount detection means for detecting a steering operation amount. . Further, the electric motor control device is a temporary target rotational speed calculating means for calculating a temporary target rotational speed of the electric motor based on the maximum load pressure so that the discharge pressure of the pump is higher than the maximum load pressure by a predetermined set pressure. And an upper limit rotational speed calculation means for calculating, as the upper limit rotational speed, the rotational speed of the electric motor that is the maximum torque that can be output when the output torque of the electric motor is the discharge pressure based on the pump discharge pressure, Correction rotational speed calculating means for calculating, as a corrected rotational speed, a rotational speed of a motor capable of discharging a flow rate required for steering operation based on the amount. Further, the electric motor control device includes a target rotational speed calculation means for calculating a lower one of the provisional target rotational speed plus the corrected rotational speed and the upper limit rotational speed as the target rotational speed of the electric motor; And a rotation speed control means for controlling the rotation speed of the electric motor so that the rotation speed of the motor becomes a target rotation speed .

  According to the present invention, it is possible to control the rotation speed of the electric motor that drives the fixed displacement pump in accordance with the load of the actuator. As a result, the rotational speed of the motor can be controlled so that the flow rate of the hydraulic oil supplied to the actuator becomes an optimal flow rate corresponding to the load of the actuator without being affected by the temperature change of the hydraulic oil. Therefore, the actuator can be driven at a speed corresponding to the operation amount of the lever while using a fixed displacement pump.

1 is a schematic configuration diagram of a motor control device for a battery-type forklift according to a first embodiment of the present invention. It is a flowchart explaining the rotational speed control of the motor by 1st Embodiment of this invention. It is a flowchart explaining the load sensing control process by 1st Embodiment of this invention. It is a table which calculates correction motor rotation speed based on load sensing control pressure. It is a table which calculates an upper limit motor rotation speed based on pump discharge pressure. It is a schematic block diagram of the motor control apparatus of the battery-type forklift by 2nd Embodiment of this invention. It is a schematic block diagram of the motor control apparatus of the battery-type forklift by 3rd Embodiment of this invention. It is a flowchart explaining the load sensing control process by 3rd Embodiment of this invention. 3 is a table for calculating a steering correction motor rotation speed based on a steering operation amount. It is a schematic block diagram of the motor control apparatus of the battery-type forklift by 4th Embodiment of this invention. It is a flowchart explaining the rotational speed control of the motor by 4th Embodiment of this invention. It is a flowchart explaining the setting pressure calculation process by 4th Embodiment of this invention. It is a schematic block diagram of the motor control apparatus of the battery-type forklift by other embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic configuration diagram of a motor control device 100 for a battery-type forklift according to a first embodiment of the present invention.

  A battery-type forklift motor control device 100 according to this embodiment includes a battery 1, an inverter 2, a motor 3, a hydraulic pump 4, a cargo handling device control unit 5, a maximum load pressure detection circuit 6, and a relief valve 7. A discharge pressure sensor 8 and a controller 9.

  The battery 1 stores electric power for driving the battery-type forklift, and supplies the stored electric power to various electrical components as necessary. As the battery 1, a lithium ion secondary battery or a high-capacity capacitor that can be charged from the outside can be used.

  The inverter 2 includes a plurality of semiconductor switches such as IGBTs (Insulated Gate Bipolar Transistors). The semiconductor switch of the inverter 2 is controlled to be opened and closed by the controller 9, whereby the DC power from the battery 1 is converted into three-phase AC power and supplied to the motor 3.

  The motor 3 is a three-phase AC synchronous motor 3 in which a permanent magnet is embedded in a rotor and a stator coil is wound around a stator.

  The hydraulic pump 4 is a fixed displacement pump. The hydraulic pump 4 is driven by the motor 3 and discharges hydraulic oil at a flow rate corresponding to the rotational speed of the motor 3.

  The cargo handling device control unit 5 includes a lift cylinder 51, a lift control valve 52, a tilt cylinder 53, and a tilt control valve 54, and controls the lifting / lowering operation and the forward / backward tilting operation of the fork that supports the load.

  The lift cylinder 51 is divided into a rod-side fluid chamber 512 and a bottom-side fluid chamber 513 by a piston rod 511 that moves slidably in the lift cylinder 51. The lift cylinder 51 is a single-action cylinder that supplies and discharges hydraulic oil only to the bottom side fluid chamber 513 (hereinafter referred to as “supply / discharge”), and functions as a hydraulic actuator for moving the fork up and down. .

  The lift control valve 52 is a three-port direction switching valve operated by a manual lever 521. The lift control valve 52 controls the raising and lowering operation of the fork by controlling the supply amount and discharge amount of hydraulic oil to the bottom side fluid chamber 513 of the lift cylinder 51 (hereinafter referred to as “supply / discharge amount”).

  Specifically, when the lift control valve 52 is switched to the lift control position (a), the hydraulic oil discharged from the hydraulic pump 4 is supplied to the bottom fluid chamber 513 of the lift cylinder 51, and the fork rises together with the piston rod. .

  When the lift control valve 52 is switched to the lowering control position (b), the piston rod 511 is lowered together with the fork by the weight of the load and the fork, and the hydraulic oil discharged from the bottom side fluid chamber 513 of the lift cylinder 51 is transferred to the oil tank 10. Is returned.

  When the lift control valve 52 is switched to the holding control position (c), the supply and discharge of the hydraulic oil to the bottom fluid chamber 513 of the lift cylinder 51 is stopped, and the fork is held at an arbitrary height.

  The tilt cylinder 53 is divided into a rod-side fluid chamber 532 and a bottom-side fluid chamber 533 by a piston rod 531 that moves slidably in the tilt cylinder 53. The tilt cylinder 53 is a double-action cylinder in which hydraulic oil is supplied to and discharged from both the rod-side fluid chamber 532 and the bottom-side fluid chamber 533, and functions as a hydraulic actuator for tilting the fork forward and backward.

  The tilt control valve 54 is a four-port direction switching valve operated by a manual lever 541. The tilt control valve 54 controls the forward / backward tilting operation of the fork by controlling the amount of hydraulic oil supplied to and discharged from the rod side fluid chamber 532 and the bottom side fluid chamber 533 of the tilt cylinder 53.

  Specifically, when the tilt control valve 54 is switched to the forward tilt control position (d), the hydraulic oil discharged from the hydraulic pump 4 is supplied to the bottom side fluid chamber 533 of the tilt cylinder 53 and the rod side fluid chamber 532. The hydraulic oil is discharged from the oil tank 10 and returned to the oil tank 10. As a result, the piston rod moves in the upper right direction in the figure, and the fork is tilted forward.

  When the tilt control valve 54 is switched to the backward tilt control position (e), the hydraulic oil discharged from the hydraulic pump 4 is supplied to the rod-side fluid chamber 532 of the tilt cylinder 53 and the hydraulic oil is supplied from the bottom-side fluid chamber 533. It is discharged and returned to the oil tank 10. Thereby, the piston rod 531 moves in the lower left direction in the figure, and the fork is tilted backward.

  When the tilt control valve 54 is switched to the holding control position (f), the supply and discharge of the hydraulic oil to and from the rod side fluid chamber 532 and the bottom side fluid chamber 533 of the tilt cylinder 53 are stopped, and the fork is held at an arbitrary angle.

  The maximum load pressure detection circuit 6 is a circuit for detecting the largest load pressure among the load pressures acting on the cargo handling device control unit 5, and includes a first load pressure line 61, a second load pressure line 62, The shuttle valve 63, the third load pressure line 64, and the load pressure detection sensor 65 are provided.

  The first load pressure line 61 is a line on which a load pressure acting on the lift control valve 52 (hereinafter referred to as “lift load pressure”) acts, and one end is connected to the lift control valve 52 and the other end will be described later. Connected to the first inlet port 631 of the shuttle valve 63. The lift load pressure is a load applied to the lift cylinder 51 when raising and lowering the fork, and becomes the hydraulic pressure of the bottom side fluid chamber 513 of the lift cylinder 51.

  The second load pressure line 62 is a line on which a load pressure acting on the tilt control valve 54 (hereinafter referred to as “tilt load pressure”) acts. One end of the second load pressure line 62 is connected to the tilt control valve 54 and the other end will be described later. Connected to the second inlet port 632 of the shuttle valve 63. The tilt load pressure is a load applied to the tilt cylinder 53 when the fork is tilted back and forth. When the fork is tilted forward, the hydraulic pressure of the bottom side fluid chamber 533 is obtained, and when the fork is tilted rearward. The hydraulic pressure of the rod side fluid chamber 632 is obtained.

  The shuttle valve 63 is a three-port valve including two inlet ports, a first inlet port 631 and a second inlet port 632, and one outlet port 633. A lift load pressure acts on the first inlet port 631 of the shuttle valve 63 via the first load pressure line 61, and a tilt load pressure acts on the second inlet port 632 via the second load pressure line 62. To do. The shuttle valve 63 communicates the inlet port and the outlet port 633, which have a larger load pressure among the load pressures (lift load pressure and tilt load pressure) acting on the two inlet ports, respectively.

  The third load pressure line 64 has one end connected to the outlet port 633 of the shuttle valve 63 and the other end connected to a pressure receiving portion 71 of the relief valve 7 described later. As a result, the load pressure selected by the shuttle valve 63, that is, the larger load pressure of the lift load pressure and the tilt load pressure acts on the third load pressure line 64. In the present embodiment, the larger load pressure of the lift load pressure and the tilt load pressure is referred to as “maximum load pressure”.

  The load pressure sensor 65 is provided in the third load pressure line 64 and detects the load pressure acting on the third load pressure line 64, that is, the maximum load pressure.

  In the relief valve 7, the pressure of the supply line 11 that distributes the hydraulic oil discharged from the hydraulic pump 4 to the lift cylinder 51 and the tilt cylinder 53 (hereinafter referred to as “pump discharge pressure”) is the pressing force of the spring 72 and the maximum load. It is opened when it becomes larger than the sum of the pressure and the excess hydraulic oil discharged from the hydraulic pump 4 is returned to the oil tank 10. Note that the pressing force of the spring 72 is set to be equal to a set pressure described later.

  The discharge pressure sensor 8 is provided in the supply line 11 and detects the pump discharge pressure.

  The controller 9 includes a microcomputer having a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface).

  In addition to the detection signals of the load pressure sensor 65 and the discharge pressure sensor 8 described above, the controller 9 includes a rotation speed sensor 91 that detects the rotation speed of the motor 3 (hereinafter referred to as “motor rotation speed”) and an operator. Detection signals from various sensors such as a seating sensor 92 that detects whether or not the user is sitting in the driver's seat are input. Based on these input signals, the controller 9 performs load sensing control for controlling the rotational speed of the motor 3 so that the pump discharge pressure is higher than the maximum load pressure by a predetermined set pressure. Thereby, the discharge flow rate of the hydraulic pump 4 is controlled to an optimum flow rate according to the load applied to the lift cylinder 51 and the tilt cylinder 53 when the fork is lifted and tilted forward and backward. Hereinafter, the rotational speed control of the motor 3 according to this embodiment will be described.

  FIG. 2 is a flowchart illustrating the rotational speed control of the motor 3 according to the present embodiment. The controller 9 executes this routine at a predetermined calculation cycle (for example, 10 ms) during operation of the battery-type forklift.

  In step S <b> 1, the controller 9 determines whether an operator is sitting in the driver's seat based on the detection signal from the seating sensor 92. If the operator is not sitting in the driver's seat, the controller 9 performs the process of step S2. On the other hand, if an operator is sitting in the driver's seat, the process of step S3 is performed.

  In step S2, the controller 9 sets the seating flag to 0. The seating flag is a flag that is set to 0 if an operator is not sitting in the driver's seat, and is set to 1 if an operator is sitting in the driver's seat.

  In step S <b> 3, the controller 9 controls the inverter 2 to stop power supply to the motor 3 and stop the motor 3 in order to ensure safety.

  In step S4, the controller 9 determines whether or not the seating flag is set to 1. If the seating flag is set to 0, the controller 9 performs the process of step S5. On the other hand, if the seating flag is already set to 1, the process of step S7 is performed.

  In step S5, the controller 9 sets the seating flag to 1.

  In step S <b> 6, the controller 9 controls the inverter 2 so that the rotational speed of the motor 3 becomes a predetermined starting rotational speed, supplies necessary power to the motor 3, and drives the motor 3.

  In step S7, the controller 9 performs a load sensing control process. Details of the load sensing control process will be described later with reference to FIG.

  FIG. 3 is a flowchart illustrating the load sensing control process according to the present embodiment.

  In step S71, the controller 9 calculates the target pump discharge pressure Pt by adding the maximum load pressure Plmax and a predetermined set pressure Pset that is set in advance. The set pressure Pset is appropriately set in consideration of the pressure loss of the oil passage such as the supply line 11.

  In step S72, the controller 9 calculates the load sensing control pressure Pls by subtracting the target pump discharge pressure Pt from the pump discharge pressure P detected by the discharge pressure sensor 8.

  In step S73, the controller 9 refers to the table of FIG. 4 and, based on the load sensing control pressure Pls, the correction value of the motor rotational speed (hereinafter referred to as “the pump discharge pressure Pt to be the target pump discharge pressure Pt”). It is referred to as “corrected motor rotation speed.”) Nc is calculated.

  As shown in FIG. 4, when the load sensing control pressure Pls is a positive value, that is, when the pump discharge pressure P is larger than the target pump pressure Pt, the correction motor rotation speed Nc is set to the target pump pressure. In order to lower it to Pt, it becomes a negative value. As the load sensing control pressure Pls increases, the correction motor rotation speed Nc increases toward the negative side.

  On the other hand, when the load sensing control pressure Pls is a negative value, that is, when the pump discharge pressure P is smaller than the target pump pressure Pt, the correction motor rotation speed Nc increases the pump discharge pressure P to the target pump pressure Pt. It becomes a positive value. As the load sensing control pressure Pls decreases, the correction motor rotation speed Nc increases toward the positive side.

  In step S74, the controller 9 calculates the provisional target motor rotation speed Nit by adding the motor rotation speed N detected by the rotation speed sensor 91 and the correction motor rotation speed Nc.

  In step S75, the controller 9 refers to the table of FIG. 5 and, based on the pump discharge pressure P detected by the discharge pressure sensor 8, the maximum torque that can be output when the output torque of the motor 3 is the pump discharge pressure P. The motor rotation speed (hereinafter referred to as “upper limit motor rotation speed”) Nhl is calculated.

  In step S76, the controller 9 compares the provisional target motor rotation speed Nit with the upper limit motor rotation speed Nhl, and sets the smaller one as the target motor rotation speed Nt.

  In step S <b> 77, the controller 9 controls the inverter 2 so that the motor rotation speed N becomes the target motor rotation speed Nt, and supplies necessary power to the motor 3.

  Hereinafter, the effect of the rotational speed control of the motor 3 according to the present embodiment will be described.

  The viscosity of the hydraulic oil changes according to the temperature of the hydraulic oil. Therefore, the volumetric efficiency of the hydraulic pump 4 changes according to the temperature of the hydraulic oil. Therefore, when the fixed displacement type hydraulic pump 4 is used as in the prior art, the rotational speed of the motor 3 that drives the hydraulic pump 4 is controlled according to the operation amount of the manual levers 521 and 541. When the viscosity of the hydraulic oil is high, the discharge flow rate of the hydraulic pump 4 may be insufficient. As a result, there is a problem that the hydraulic actuator cannot be driven at a speed corresponding to the amount of operation of the manual levers 521 and 541 by the operator. In other words, there has been a problem that the fork can not be lifted and tilted back and forth at a speed required by the worker.

  On the other hand, according to the present embodiment, the rotational speed of the motor 3 that drives the fixed displacement hydraulic pump 4 is controlled according to the loads of the lift cylinder 51 and the tilt cylinder 53 as hydraulic actuators. Specifically, the pump discharge pressure was set in consideration of the pressure loss of the oil passage such as the supply line 11 rather than the larger one of the lift load pressure and the tilt load pressure (maximum load pressure). Load sensing control for controlling the rotation speed of the motor 3 was performed so as to be increased by a predetermined set pressure.

  As a result, regardless of the temperature of the hydraulic fluid, the flow rate of the hydraulic fluid discharged from the fixed displacement hydraulic pump 4 becomes an optimum flow rate according to the loads of the lift cylinder 51 and the tilt cylinder 53 as hydraulic actuators. In addition, the rotational speed of the motor 3 that drives the hydraulic pump 4 can be controlled.

  That is, the motor 3 that drives the hydraulic pump 4 according to the loads of the lift cylinder 51 and the tilt cylinder 53 as hydraulic actuators so that the fork can be moved up and down and tilted back and forth at a speed required by the operator. The rotation speed can be controlled.

  Further, since the motor 3 can be driven at the minimum motor rotation speed at which the fork can be lifted and tilted back and forth at the speed required by the operator, the amount of power supplied to the motor 3 is optimized. Power consumption can be improved.

  In addition, since the fixed displacement hydraulic pump 4 that is smaller and less expensive than the variable displacement hydraulic pump can be used, the mountability can be improved and the cost can be reduced.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIG. The present embodiment is different from the first embodiment in that the hydraulic oil discharged from the hydraulic pump 4 is also supplied to the steering control unit. Hereinafter, the difference will be mainly described. In each of the following embodiments, the same reference numerals are used for portions that perform the same functions as those of the first embodiment described above, and repeated descriptions are omitted as appropriate.

  FIG. 6 is a schematic configuration diagram of a motor control device 100 for a battery-type forklift according to a second embodiment of the present invention.

  The battery-type forklift motor control device 100 according to the present embodiment further includes a steering control unit 20 and a priority valve 30, and the configuration of the maximum load pressure detection circuit 6 is different from that of the first embodiment.

  The steering control unit 20 includes a steering cylinder 21, a steering control valve 22, and a gerotor 23, and controls the steering angle of the wheel of the battery-type forklift.

  The steering cylinder 21 is partitioned into a first rod side fluid chamber 212 and a second rod side fluid chamber 213 by a double rod type piston rod 211 that slidably moves in the steering cylinder 21. The steering cylinder 21 is a double acting cylinder in which hydraulic oil is supplied to and discharged from both the first rod side fluid chamber 212 and the second rod side fluid chamber 213, and drives a link that gives a steering angle to the wheels. To function as a hydraulic actuator.

  The steering control valve 22 is switched from the neutral position (g) to the left or right operating position (h) or (i) by operating the steering 221 that adjusts the traveling direction of the battery-type forklift. It is a valve. The steering control valve 22 drives the steering cylinder 21 by controlling the supply and discharge amount of hydraulic oil to and from the first rod side fluid chamber 212 and the second rod side fluid chamber 213 of the steering cylinder 21 via the gerotor 23, Control the steering angle.

  The gerotor 23 is rotated by the hydraulic oil supplied from the steering control valve 22 and discharges hydraulic oil at a flow rate corresponding to the operation amount of the steering 221. The hydraulic oil discharged from the gerotor 23 is supplied to the steering cylinder 21 via the steering control valve 22. The rotational torque of the gerotor 23 is fed back to the steering control valve 22, and when the gerotor 23 measures a flow rate of hydraulic oil corresponding to the operation amount of the steering 221 (displacement amount of the steering control valve 22) and rotates a predetermined amount, the steering control valve 22 is returned to the neutral position.

  The maximum load pressure detection circuit 6 is a circuit for detecting the largest load pressure among the load pressure acting on the cargo handling device control unit 5 and the load pressure acting on the steering control unit 20, and is a fourth load. A pressure line 66, a second shuttle valve 67, and a fifth load pressure line 68 are further provided.

  The fourth load pressure line 66 is a line on which a load pressure acting on the steering control valve 22 (hereinafter referred to as “steering load pressure”) acts, and one end is connected to the steering control valve 22 and the other end is described later. Connected to the first pressure receiving portion 31 of the priority valve 30. The steering load pressure is a load applied to the steering cylinder 21 at the time of steering operation. When the steering wheel 221 is rotated to the left, the hydraulic pressure of the first rod side fluid chamber 212 is obtained, and when the steering wheel 221 is rotated to the right. The hydraulic pressure of the second rod side fluid chamber 213 is obtained.

  The second shuttle valve 67 is a three-port valve including two inlet ports, a first inlet port 671 and a second inlet port 672, and one outlet port 673. The steering load pressure acts on the first inlet port 671 of the second shuttle valve 67 via the fourth load pressure line 66, and the lift load pressure acts on the second inlet port 672 via the third load pressure line 64. The larger load pressure of the tilt load pressure acts. The second shuttle valve 67 communicates the inlet port and the outlet port 673, which have a larger load pressure among the load pressures acting on the two inlet ports, respectively.

  One end of the fifth load pressure line 68 is connected to the outlet port 633 of the second shuttle valve 67, and the other end is a closed end. As a result, the load pressure selected by the second shuttle valve 67, that is, the largest load pressure among the lift load pressure, the tilt load pressure, and the steering load pressure acts on the fifth load pressure line 68. In the present embodiment, the highest load pressure among the lift load pressure, the tilt load pressure, and the steering load pressure is referred to as a “maximum load pressure”.

  The load pressure sensor 65 according to the present embodiment is provided in the fifth load pressure line 68 and detects the load pressure of the fifth load pressure line 68, that is, the maximum load pressure.

  The priority valve 30 is a three-port direction switching valve, and includes a first pressure receiving portion 31 and a spring 32 that press the priority valve 30 toward the right side in the figure, and a second that presses the priority valve 30 toward the left side in the figure. Pressure receiving portion 33. A pressure (steering load pressure) in the fourth load pressure line 66 is guided to the first pressure receiving portion 31 as a pilot pressure. The pressure of the oil passage 34 connecting the priority valve 30 and the steering control valve 22 (hereinafter referred to as “steering supply pressure”) is guided to the second pressure receiving portion 33 as a pilot pressure. With this configuration, the priority valve 30 controls the flow rate of the hydraulic oil supplied to the steering control unit 20 so that the differential pressure between the steering supply pressure and the steering load pressure is equal to the pressing force of the spring 32. Accordingly, the priority valve 30 preferentially supplies the hydraulic oil discharged from the hydraulic pump 4 to the steering control unit 20 side, and supplies the surplus to the cargo handling control unit 5 side.

  In the present embodiment, load sensing control similar to that in the first embodiment is performed so that the pump discharge pressure P is higher than the maximum load pressure Plmax detected by the load pressure sensor 65 by a predetermined pressure Pset.

  As a result, the flow rate of the hydraulic oil supplied to the two control units of the cargo handling device control unit 5 and the steering control unit 20 is adjusted using the hydraulic actuators of the respective control units while using one fixed displacement hydraulic pump 4. It can be controlled to an optimum flow rate according to the load.

(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to FIG. This embodiment is different from the first embodiment in that the provisional target motor rotation speed Nit is corrected based on the operation amount of the steering wheel 221. Hereinafter, the difference will be mainly described.

  FIG. 7 is a schematic configuration diagram of a motor control device 100 for a battery-type forklift according to a third embodiment of the present invention.

  The battery-type forklift motor control device 100 according to the present embodiment is different from that of the first embodiment in that the steering control unit 20, the priority valve 30, the fourth load pressure line 66, the steering operation angle detection sensor 93, Are newly provided.

  The steering operation angle detection sensor 93 detects the operation angle of the steering wheel 221, that is, how much the steering wheel 221 is operated.

  In the present embodiment, the provisional target motor rotation speed is corrected based on the operation angle of the steering wheel 221 during the load sensing control process. Hereinafter, the load sensing control process according to the present embodiment will be described.

  FIG. 8 is a flowchart illustrating the load sensing control process according to the present embodiment.

  Since the processing from step S71 to step S77 is the same as that in the first embodiment, description thereof is omitted here.

  In step S <b> 371, the controller 9 calculates the steering operation amount θ by integrating the steering operation angle detected by the steering operation angle detection sensor 93.

  In step S372, the controller 9 refers to the table of FIG. 9, and based on the steering operation amount θ, the motor rotational speed correction value (hereinafter referred to as “steering correction motor rotation” required for discharging the flow rate required for the steering operation). "Speed")) Ns is calculated.

  In step S373, the controller 9 corrects the provisional target motor rotation speed Nit by adding the steering correction motor rotation speed Ns to the provisional target motor rotation speed Nit.

  According to this embodiment described above, as in the first embodiment, the rotational speed of the motor 3 that drives the fixed displacement hydraulic pump 4 according to the loads of the lift cylinder 51 and the tilt cylinder 53 as hydraulic actuators. And the rotational speed of the motor 3 is corrected according to the steering operation amount.

  As a result, the same effects as in the first embodiment can be obtained, and even if the steering load pressure changes suddenly when the wheel hits an obstacle such as a curb stone, the motor rotation speed does not change based on the steering load pressure. The speed does not change suddenly. Therefore, the operability of the steering wheel 221 can be improved.

(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described with reference to FIG. The present embodiment is different from the third embodiment in that the set pressure Pset is changed according to the operating state of the hydraulic actuator. Hereinafter, the difference will be mainly described.

  FIG. 10 is a schematic configuration diagram of a motor control device 100 for a battery-type forklift according to a fourth embodiment of the present invention.

  The motor control device 100 for a battery-type forklift according to the present embodiment is provided with a lift lever operation detection sensor 94 and a tilt lever operation detection sensor 95 in addition to the third embodiment.

  The lift lever operation detection sensor 94 is a sensor that detects whether the manual lever 521 of the lift control valve 52 is operated, and indicates that the lift control valve 52 has been switched to a position other than the holding control position (c). Detect.

  The tilt lever operation detection sensor 95 is a sensor that detects whether the manual lever 541 of the tilt control valve 54 is operated, and indicates that the tilt control valve 54 has been switched to a position other than the holding control position (f). Detect.

  In the present embodiment, the value of the set pressure Pset is changed based on detection signals from the lift lever operation detection sensor 94, the tilt lever operation detection sensor 95, and the steering operation angle detection sensor 93.

  FIG. 11 is a flowchart illustrating the rotational speed control of the motor 3 according to the present embodiment.

  Since the processing from step S1 to step S7 is the same as that of the first embodiment, description thereof is omitted here.

  In step S41, the controller 9 performs a set pressure calculation process. The set pressure calculation process will be described later with reference to FIG.

  FIG. 12 is a flowchart for explaining the set pressure calculation process.

  In step S411, the controller 9 determines whether the manual lever 521 of the lift control valve 52 is operated based on the detection signal of the lift lever operation detection sensor 94, that is, the lift control valve 52 is other than the holding control position (c). Determine if it has been switched to a position. The controller 9 performs the process of step S414 if the manual lever 521 of the lift control valve 52 is operated, and performs the process of step S412 if it is not operated.

  In step S412, the controller 9 determines whether the manual lever 541 of the tilt control valve 54 is operated based on the detection signal of the tilt lever operation detection sensor 95, that is, the tilt control valve 54 is in a position other than the holding control position (f). Determine if it has been switched to a position. The controller 9 performs the process of step S414 if the manual lever 541 of the tilt control valve 54 is operated, and performs the process of step S413 if it is not operated.

  In step S413, the controller 9 determines, based on the detection signal of the steering operation angle detection sensor 93, whether the steering 221 is operated, that is, whether the steering 221 is rotated to the left or right. If the steering wheel 221 is operated, the controller 9 performs the process of step S414, and if not operated, the controller 9 performs the process of step S415.

  As described above, the controller 9 performs the process of step S414 if any one of the manual lever 521 of the lift control valve 52, the manual lever 541 of the tilt control valve 54, and the steering 221 is operated. The process of step S415 is performed.

  In step S414, the controller 9 sets the value of the set pressure Pset to the first predetermined value Pnormal.

  In step S415, the controller 9 sets the value of the set pressure Pset to a second predetermined value Plow that is smaller than the first predetermined value.

  According to the present embodiment described above, when none of the manual lever 421 of the lift control valve 52, the manual lever 541 of the tilt control valve 54, and the steering 221 are operated, the set pressure Pset is normally set. The first predetermined value Plow is set to be smaller than the first predetermined value Pnormal.

  Thereby, the target pump discharge pressure Pt can be lowered when the manual lever 521 of the lift control valve 52, the manual lever 541 of the tilt control valve 54, and the steering 221 are not operated. As a result, the motor rotation speed can be reduced, and the power consumption can be further improved.

  Note that the present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.

  For example, in each of the above embodiments, the lift control valve 52 and the tilt control valve 54 are mechanically operated by the manual levers 421 and 541. However, as shown in FIG. 13, the control valves 52 and 54 are electromagnetic valves. It may be operated electrically. In this case, the operation signals of the manual levers 521 and 541 may be input to the controller 9 as electrical signals, and the control valves 52 and 54 may be controlled by the controller 9 in accordance with the input signals.

  Moreover, in each said embodiment, although the rotational speed control of the motor 3 is applied to a battery-type forklift, you may apply not only to a battery-type forklift but to various industrial vehicles which use a hydraulic actuator.

3 Motor (electric motor)
4 Hydraulic pump (pump)
6 Maximum load pressure detection circuit 8 Discharge pressure sensor (Discharge pressure detection means)
21 Steering cylinder (steering actuator)
22 Steering control valve 51 Lift cylinder (actuator)
52 Lift control valve (control valve)
53 Tilt cylinder (actuator)
54 Tilt control valve (control valve)
65 Load pressure sensor (maximum load pressure detection means)
S1 Seating detection means S3 Stopping means S74 Temporary target rotational speed calculation means S75 Upper limit rotational speed calculation means S76 Target rotational speed calculation means S77 Rotational speed control means S371 Steering operation amount detection means S373 Correction rotational speed calculation means S411 Operation detection means S412 Operation detection Means S413 Operation detection means S415 Setting pressure variable means

Claims (3)

An electric motor control device for controlling the rotation speed of an electric motor mounted on an industrial vehicle,
A pump that is driven by the electric motor and discharges a working fluid at a flow rate according to the rotational speed of the electric motor;
At least one actuator driven by the working fluid discharged from the pump;
A cut-off control valve for switching supply and discharge of the working fluid to and from the actuator;
Among the load pressures of the actuator, a maximum load pressure detection circuit for guiding the highest load pressure as the maximum load pressure,
A steering actuator that is driven by the working fluid discharged from the pump and controls the steering angle of the wheels of the industrial vehicle;
A steering control valve that switches supply and discharge of the working fluid to and from the steering actuator in accordance with a steering operation;
A discharge pressure detecting means for detecting a discharge pressure of the pump;
A maximum load pressure detecting means for detecting a load pressure of the maximum load pressure detecting circuit;
Steering operation amount detection means for detecting the operation amount of the steering;
Provisional target rotation speed calculation means for calculating a provisional target rotation speed of the electric motor based on the maximum load pressure so that the discharge pressure of the pump is higher than the maximum load pressure by a predetermined set pressure;
Based on the discharge pressure of the pump, upper limit rotation speed calculation means for calculating the rotation speed of the electric motor that is the maximum torque that can be output when the output torque of the electric motor is the discharge pressure;
A correction rotation speed calculation means for calculating, as a correction rotation speed, a rotation speed of the motor capable of discharging a flow rate required for the steering operation based on the steering operation amount;
A target rotational speed calculating means for calculating a lower one of the provisional target rotational speed plus a corrected rotational speed and the upper limit rotational speed as a target rotational speed of the electric motor;
Rotational speed control means for controlling the rotational speed of the electric motor so that the rotational speed of the electric motor becomes the target rotational speed;
An electric motor control device comprising: Operation detecting means for detecting whether or not the actuator and the steering actuator are operating;
When all of the actuator and the steering actuator are not operated, a set pressure variable means for making the set pressure smaller than when at least one is operated;
The electric motor control device according to claim 1, comprising: Seating detection means for detecting whether an operator is seated in the seat of the industrial vehicle;
An electric motor stopping means for stopping the driving of the electric motor when it is determined that an operator is not seated on the seat;
The electric motor control device according to claim 1, further comprising:

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