JP2013203490A - Motor drive device for forklift and forklift using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce power consumption while suppressing reduction of an operation feeling.SOLUTION: A motor drive device 300 drives a plurality of motors mounted on a forklift 600. A plurality of power conversion devices 100, 102 and 104 are provided for each of motors M1, M2 and M3, and supply power to the corresponding motors. An output limit part 302 gives priority to the plurality of motors M1-M3 and limits output of the power conversion devices 100, 102 and 104 supplying power to the motor M1-M3 with low priority.

Description

  The present invention relates to a motor drive device for a forklift.

  One of the industrial vehicles is an electric forklift that uses a battery as a power source. An electric forklift (hereinafter simply referred to as a forklift) is a traveling motor that transmits power to a front wheel that is a traveling wheel (driving wheel) and a hydraulic pump that controls a turning angle (steering angle) of a rear wheel that is a steered wheel. Hydraulic actuator motor (steering motor) that transmits power, hydraulic actuator motor (loading motor) that transmits power to the hydraulic pump that controls the lifting body, and power conversion that drives each of the travel motor, steering motor, and cargo handling motor Equipment.

JP 2001-113989 A

  While the capacity of the battery is finite, the forklift requires a long operable time. In order to realize long-time operation within a limited battery capacity, it is necessary to suppress power consumption in the traveling motor and the cargo handling motor.

  The DC voltage (battery voltage) generated by the battery decreases with time. When the battery voltage decreases, the voltage amplitude applied to the motor coil decreases, so the current required to supply the same power to the motor increases. When the circuit current increases, there is a problem that power loss at the wiring resistance increases and efficiency decreases. Therefore, it is preferable to reduce the power consumption of the power conversion device even when the battery voltage decreases.

  In order to limit the power consumption of the travel motor, the cargo handling motor, and the power conversion device that drives them, it is necessary to limit the current, that is, the torque. Here, in order to reduce the power consumption of the motor and the power converter, regardless of whether it is a traveling motor, a cargo handling motor, or a steering motor, if the output of the power converter that drives each motor is uniformly limited, it will not accelerate when it wants to accelerate A problem arises that the user feels stressed because the comfortable operation feeling is impaired, such as when it is difficult to climb a hill or when it is necessary to lift a heavy load.

  The present invention has been made in view of the problems, and one of the exemplary purposes of an aspect thereof is to provide a forklift capable of reducing power consumption while suppressing a decrease in operational feeling.

  One embodiment of the present invention relates to a motor drive device that drives a plurality of motors mounted on a forklift. A motor drive device is provided for each motor, and a plurality of power conversion devices that supply power to the corresponding motor and a priority order are assigned to the plurality of power conversion devices. An output limiting unit that limits power.

  According to this aspect, the power conversion device, in other words, prioritizing the motor, supplying sufficient power to the motor to be prioritized, and limiting the power supply to the other motors, reduces the operational feeling. While suppressing, power consumption can be reduced. In this specification, “power consumption of the power conversion device” includes power consumption of a load driven by the power conversion device.

The plurality of motors may include a traveling motor and a cargo handling motor. The output restriction unit may set the priority of the power converter that drives the traveling motor higher than the power converter that drives the cargo handling motor.
According to this aspect, even if the luggage cannot be carried, the minimum traveling ability can be secured.

  The plurality of motors may include a travel motor, a cargo handling motor, and a steering motor. The output limiting unit sets the power converter that drives the cargo handling motor to the lowest priority, sets the power converter that drives the traveling motor to the next lowest priority, and sets the power converter that drives the steering motor to the highest priority. May be.

The output restriction unit may switch the priority order of the plurality of power conversion devices according to the state of the forklift.
Forklifts may sometimes prioritize traveling when priority should be given to cargo handling. In this case, by switching the priority according to the state of the forklift, it is possible to reduce power consumption while suppressing a decrease in operational feeling.

  The output restriction unit may set the priority of the power conversion device driven first among the plurality of motors to be high and set the priority of the power conversion device not being driven low.

  The power limitation by the output limiting unit is any one of torque limitation, speed limitation, acceleration limitation, current limitation, carrier frequency reduction, switching from three-phase modulation to two-phase modulation, and carrier frequency reduction. , Or any combination thereof.

  Another aspect of the present invention relates to a forklift. A forklift is a vehicle body, wheels that support the vehicle body, a traveling motor that transmits power to the wheels, a lifting body provided at the front of the vehicle body, a hydraulic actuator that drives the lifting body, and power transmission to the hydraulic actuator. And a motor for driving the traveling motor and the cargo handling motor.

  Note that any combination of the above-described constituent elements and the constituent elements and expressions of the present invention replaced with each other among methods, apparatuses, systems, and the like are also effective as an aspect of the present invention.

  According to the present invention, power consumption can be reduced.

It is a perspective view which shows the external view of a forklift. It is a figure which shows an example of the control panel of a forklift. It is a block diagram which shows the structure of the electric system of a forklift, and a mechanical system. It is a wave form diagram which shows an example of operation | movement of the motor drive device which concerns on embodiment. It is a wave form diagram which shows another example of operation | movement of the motor drive device which concerns on embodiment.

  The present invention will be described below based on preferred embodiments with reference to the drawings. The same or equivalent components, members, and processes shown in the drawings are denoted by the same reference numerals, and repeated descriptions are omitted as appropriate. The embodiments do not limit the invention but are exemplifications, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention.

In this specification, “the state in which the member A is connected to the member B” means that the member A and the member B are electrically connected to each other in addition to the case where the member A and the member B are physically directly connected. It includes cases where the connection is indirectly made through other members that do not substantially affect the general connection state, or that do not impair the functions and effects achieved by their combination.
Similarly, “the state in which the member C is provided between the member A and the member B” refers to the case where the member A and the member C or the member B and the member C are directly connected, as well as their electric It includes cases where the connection is indirectly made through other members that do not substantially affect the general connection state, or that do not impair the functions and effects achieved by their combination.

  FIG. 1 is a perspective view showing an external view of a forklift. The forklift 600 includes a vehicle body (chassis) 602, a fork 604, a lifting body (lift) 606, a mast 608, and wheels 610 and 612. The mast 608 is provided in front of the vehicle body 602. The elevating body 606 is driven by a power source such as a hydraulic actuator (not shown in FIG. 1A, 116 in FIG. 3) and moves up and down along the mast 608. A fork 604 for supporting a load is attached to the elevating body 606.

  FIG. 2 is a view showing an example of a control panel 700 of a forklift. The control panel 700 includes an ignition switch 702, a steering wheel 704, a lift lever 706, an accelerator pedal 708, a brake pedal 710, a dashboard 714, and a forward / reverse lever 712.

  The ignition switch 702 is a switch for starting the forklift 600. The steering wheel 704 is an operation means for steering the forklift 600. The lift lever 706 is an operation means for moving the elevating body 606 up and down. The accelerator pedal 708 is an operating means that controls the rotation of the traveling wheels, and the travel of the forklift 600 is controlled by the user adjusting the amount of depression. When the user depresses the brake pedal 710, the brake is applied. The forward / reverse lever 712 is a lever for switching the traveling direction of the forklift 600 between forward and reverse. In addition, an inching pedal (not shown) may be provided.

  Next, the configuration of the forklift 600 will be described for traveling, cargo handling, and steering. FIG. 3 is a block diagram showing the configuration of the electrical system and the mechanical system of the forklift 600. The ECU (electronic control controller) 110 is a processor for controlling the forklift 600 as a whole.

Battery 106 outputs battery voltage V _BAT between P line and N line.
The first power conversion device 100, the second power conversion device 102, the third power conversion device 104, and the output control unit 302 constitute a motor drive device 300. The motor driving device 300 drives each of the traveling motor M1, the cargo handling motor M2, and the steering motor M3 based on the first control command value S1 to the third control command value S3 from the ECU 110. The first power conversion device 100, the second power conversion device 102, and the third power conversion device 104 each receive the battery voltage V _BAT and convert it into a three-phase AC signal, which is then transferred to the corresponding motors M1, M2, and M3. Supply.

(Running)
The ECU 110 receives a signal for instructing forward and backward from the forward / reverse lever 712 and a signal indicating a travel operation amount corresponding to the depression amount from the accelerator pedal 708, and receives a first control command value S1 corresponding to the first control command value S1 as a first value. It outputs to the power converter 100. The first power conversion device 100 controls the power supplied to the travel motor M1 according to the first control command value S1. The first control command value S1 has a correlation with a speed command value that indicates the target rotational speed of the traveling motor M1. The front wheels 610 that are drive wheels are connected to the drive shaft 114. The gear box 112 and the drive shaft 114 transmit power from the travel motor M1 to the front wheels 610.

(Handling)
The vertical movement of the elevating body 606 is controlled by the inclination of the lift lever 706. The ECU 110 detects the tilt of the lift lever 706 and outputs a second control command value S <b> 2 indicating a cargo handling operation amount corresponding to the tilt to the second power conversion device 102. The second power converter 102 supplies power corresponding to the second control command value S2 to the cargo handling motor M2, and controls its rotation. The elevating body 606 is connected to the hydraulic actuator 116. The hydraulic actuator 116 converts the rotary motion generated by the cargo handling motor M2 into a linear motion and controls the lifting body 606.

(steering)
The resolver 122 detects the rotation angle of the steering wheel 704 and outputs a signal indicating the rotation angle to the ECU 110. ECU 110 outputs third control command value S3 corresponding to the rotation angle to third power conversion device 104. The third power converter 104 supplies power corresponding to the third control command value S3 to the steering motor M3, and controls the number of rotations thereof. A rear wheel 612 that is a steered wheel is connected to a gear box 124 via a tie rod 126. The rotational motion of the steering motor M3 is transmitted to the tie rod 126 via the hydraulic actuator 118 and the gear box 124, and the steering is controlled.

The output control unit 302 monitors the battery voltage V _BAT, and decreases the allowable output power P _TOTAL of the entire motor driving device 300 as the V _BAT decreases. The allowable output power P _TOTAL is the total power consumption P1 of the first power conversion device 100 and the traveling motor M1, the total power consumption P2 of the second power conversion device 102 and the cargo handling motor M2, the third power conversion device 104, and the steering motor. This is the sum of the total power consumption P3 of M3. Thereby, it is possible to prevent the circuit current from increasing due to the decrease in the battery voltage _VBAT , and to reduce the power loss in the resistance of the current path.

Alternatively, the output control unit 302 is configured to be able to switch between a plurality of predetermined modes (for example, an energy saving mode, a normal mode, and a power mode). A different allowable output power P _TOTAL is determined for each mode. Specifically, the allowable output power is the maximum value P _MAX in the power mode, the minimum value P _MIN in the energy saving mode, and the value P _NORM between them in the normal mode.

  The output control unit 302 gives priority to the first power conversion device 100, the second power conversion device 102, and the third power conversion device 104, and limits power consumption in order from the power conversion device with the lowest priority. In other words, the traveling motor M1, the cargo handling motor M2, and the steering motor M3 are ranked.

  The power consumption here is the sum of the power consumption of the power conversion device itself and the power input to the motor as a load. Hereinafter, the power consumption of the first power conversion device 100 is denoted as P1, the power consumption of the second power conversion device 102 as P2, and the power consumption of the third power conversion device 104 as P3.

  The power consumption limit is any one of torque limit, speed limit, acceleration limit, current limit, carrier frequency decrease, switching from three-phase modulation to two-phase modulation, carrier frequency decrease, or those Any combination of the above may be included. In the present invention, the method for limiting the output of a certain power converter is not limited, and as a result, the total power consumption of the power converter itself and the motor driven by the power converter may be reduced.

  Further, the means for limiting the power consumption may be different for each of the first power conversion device 100, the second power conversion device 102, and the third power conversion device 104. For example, the first power conversion device 100 may limit torque, the second power conversion device 102 may switch between three-phase modulation and two-phase modulation, and the third power conversion device 104 may change the carrier frequency.

  In this Embodiment, the priority of the 1st power converter device 100, the 2nd power converter device 102, and the 3rd power converter device 104 is predetermined. Specifically, the priority order of the first power conversion device 100 that drives the traveling motor M1 is set higher than that of the power conversion device 102 that drives the cargo handling motor M2. The priority order of the power conversion device 104 that drives the steering motor M3 may be set higher than that of the power conversion device 100 that drives the travel motor M1.

  The above is the configuration of the forklift 600. Next, the operation will be described.

FIG. 4 is a waveform diagram showing an example of the operation of the motor drive device 300 according to the embodiment. FIG. 4 shows how the battery voltage _VBAT decreases with time. At this time, the output control unit 302 decreases the allowable output power P _TOTAL as the battery voltage V _BAT decreases. When the allowable output power P _TOTAL is larger than a certain threshold value, the total power consumption P2 of the second power conversion device 102 having the lowest priority is limited first and gradually decreases. The power consumptions P1 and P3 of the first power converter 100 and the third power converter 104 are not limited.

When the allowable output power P _TOTAL becomes smaller than a certain threshold (time t1), thereafter, the total power consumption P1 of the first power conversion device 100 with the second priority is limited and gradually decreases. . In the example of FIG. 4, no limitation is imposed on the third power conversion device 104 having the highest priority.

  FIG. 5 is a waveform diagram showing another example of the operation of the motor drive device 300 according to the embodiment. The output control unit 302 switches between the normal mode, the energy saving mode, and the power mode in accordance with a user instruction. Alternatively, the output control unit 302 monitors the state of the forklift 600 and autonomously switches the mode according to the detected state.

FIG. 5 shows a state in which the mode is switched in the order of the power mode, the normal mode, and the energy saving mode. At this time, the allowable output power P _TOTAL decreases in the order of P _MAX , P _NORM , P _MIN in accordance with the mode switching. When the allowable output power P _TOTAL is the maximum value P _MAX , none of the power consumptions P1 to P3 is limited.

When the allowable output power P _TOTAL decreases to the intermediate value _PNORM , the power consumption P2 of the second power conversion device 102 having a low priority is limited. When the allowable output power P _TOTAL decreases to the minimum value P _MIN , the power consumption P1 of the first power conversion device 100 with the next lowest priority is limited. In the example of FIG. 5 as well, no limitation is imposed on the third power converter 104 having the highest priority.

The above is the operation of the motor driving device 300.
As described above, according to the motor drive device 300 according to the embodiment, the power conversion device, that is, the motor is prioritized, sufficient power is supplied to the motor to be prioritized, and power is supplied to the other motors. By limiting, it is possible to reduce power consumption while suppressing a decrease in operational feeling.

In the embodiment, the priority order of the traveling motor M1 is set higher than that of the cargo handling motor M2. In this case, when the allowable output power P _TOTAL decreases, the load that can be loaded first is limited, and then the output of the travel motor M1 is gradually limited.

For example, in many use sites, it is desirable that the forklift 600 can travel even when a load cannot be loaded in consideration of safety. Therefore, in a region where the allowable output power P _TOTAL is small, it is desirable to secure the minimum driving ability by limiting the power consumption P2 to zero and assigning it to the power consumption P1. According to the motor driving device 300, such control can be performed by determining the priority order.

  In the above, this invention was demonstrated based on the Example. It will be understood by those skilled in the art that the present invention is not limited to the above-described embodiment, and various design changes are possible, various modifications are possible, and such modifications are within the scope of the present invention. By the way. Hereinafter, such modifications will be described.

  In the embodiment, the case has been described in which the priorities of the first power conversion device 100, the second power conversion device 102, and the third power conversion device 104 are determined in advance, but the present invention is not limited thereto. For example, the output control unit 302 may determine the priority order of the power converter according to the state of the forklift 600.

The output control unit 302 may increase the priority of the power converter that has been driven first and decrease the priority of the remaining unused power converters. For example, assume that the user stops traveling of the forklift 600 and tries to load a load on the fork 604. In this case, the second power converter 102 that drives the cargo handling motor M2 is used while the first power converter 100 and the third power converter 104 are not used. At this time, the output control unit 302 sets the priority of the second power converter 102 to the highest priority, and all or most of the allowable output power P _TOTAL at that time is allocated to the power consumption P2 of the second power converter 102. The remaining power may be allocated to the power consumption P1 and P3 of the first power conversion device 100 and the third power conversion device 104.

Alternatively, the output control unit 302 assigns a predetermined minimum value to each of the first power conversion device 100 and the third power conversion device 104 that are not in use, out of the allowable output power P _TOTAL at that time, and all the rest You may allocate to the power consumption P2 of the 2nd power converter device 102. FIG.

600 ... Forklift, 602 ... Car body, 604 ... Fork, 606 ... Elevator, 608 ... Mast, 610 ... Front wheel, 612 ... Rear wheel, 100 ... First power converter, 102 ... Second power converter, 104 ... Third Power converter 106, battery, 110, ECU, 112, gear box, 114, drive shaft, 116, 118 ... hydraulic actuator, 120 ... steering shaft, 122 ... resolver, 124 ... gear box, 126 ... tie rod, M1 ... traveling Motor, M2 ... cargo handling motor, M3 ... steering motor, 700 ... steering panel, 702 ... ignition switch, 704 ... steering wheel, 706 ... lift lever, 708 ... accelerator pedal, 710 ... brake pedal, 712 ... forward / reverse lever, 714 ... Dashboard.

Claims (7)

A motor driving device for driving a plurality of motors mounted on a forklift,
A plurality of power converters each provided for each motor and supplying power to the corresponding motor;
An output limiting unit that gives priority to the plurality of power converters and limits power in order from the power converters with the lowest priority,
A motor drive device for a forklift, comprising: The plurality of motors includes a traveling motor and a cargo handling motor,
2. The motor drive device according to claim 1, wherein the output restriction unit sets a priority of the power conversion device that drives the traveling motor higher than the power conversion device that drives the cargo handling motor. The plurality of motors includes a travel motor, a cargo handling motor, and a steering motor,
The output restriction unit has the lowest priority of the power converter that drives the cargo handling motor, the lowest priority of the power converter that drives the traveling motor, and the priority of the power converter that drives the steering motor. The motor driving device according to claim 1, wherein the motor driving device is set to the highest value.   2. The motor drive device according to claim 1, wherein the output restriction unit switches priority of the plurality of power conversion devices according to a state of the forklift.   5. The output limiting unit sets a priority order of a power converter that is driven first among the plurality of motors and sets a priority order of a non-driven motor to a low level. The motor drive device described.   The power limiting of the power conversion device by the output limiting unit includes torque limitation, speed limitation, acceleration limitation, current limitation, carrier frequency reduction, switching from three-phase modulation to two-phase modulation, carrier frequency 6. The motor drive device according to claim 1, comprising any one of the reductions in any of the above, or any combination thereof. The car body,
Wheels for supporting the vehicle body;
A travel motor for transmitting power to the wheels;
An elevating body provided at the front of the vehicle body;
A hydraulic actuator for driving the lifting body;
A cargo handling motor for transmitting power to the hydraulic actuator;
The motor driving device according to any one of claims 1 to 6, which drives the traveling motor and the cargo handling motor;
A forklift characterized by comprising:

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