Series of fork lift and fork lift

Abstract

To provide a series of a fork lift which can reduce a manufacturing cost of an auxiliary mechanism of a steering, and a fork lift.SOLUTION: A series of a fork lift includes: a first fork lift including a first steering, a first auxiliary mechanism having a first auxiliary motor assisting the operation of the first steering by a liquid pressure, and a first control part for controlling the first auxiliary motor; and a second fork lift including a second steering, a second auxiliary mechanism having a second auxiliary motor assisting the operation of the second steering by transmitting mechanical power thereto, and a second control part for controlling the second auxiliary motor. A first substrate (802A) mounted with a first control circuit (810A) of the first control part and a second substrate mounted with a second control circuit of the second control part are used in common.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a forklift series and to a forklift. [Background technology]

[0002] Patent Document 1 describes a forklift equipped with an electric power steering device that assists steering operations. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2003-118606 A Summary of the Invention [Problem to be solved by the invention]

[0004] There are two types of steering assist mechanisms for forklifts: the first type, in which an electric pump motor drives a hydraulic pump and assists steering operation with hydraulic pressure, and the second type, in which an electric assist motor directly assists steering operation. In the first type, a chopper circuit that passes a unidirectional current is used to drive the pump motor. In the second type, a bridge circuit that passes forward and reverse currents through the electric motor is used.

[0005] In conventional forklifts, when the first type of auxiliary mechanism is installed and when the second type of auxiliary mechanism is installed, a dedicated circuit board is provided for mounting the motor control circuit.

[0006] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a series of forklift trucks and a forklift truck capable of reducing the manufacturing cost of a steering assist mechanism. [Means for solving the problem]

[0007] The series of forklift trucks according to the present invention are A first forklift including a first steering mechanism, a first auxiliary motor that assists the operation of the first steering mechanism, and a first control unit that controls the first auxiliary motor; A second forklift including a second steering mechanism, a second auxiliary motor that assists the operation of the second steering mechanism, and a second control unit that controls the second auxiliary motor; A series of forklift trucks comprising: the first assist mechanism is a mechanism that assists the operation of the first steering wheel by hydraulic pressure, the first auxiliary motor is a pump motor that drives a hydraulic pump, the first control unit has a first control circuit disposed on a first substrate; the first control circuit has a first switching element and a second switching element connected in series between a pair of terminals to which a voltage is applied, the pump motor is connected between an intermediate node between the first switching element and the second switching element and one of the pair of terminals, the second assist mechanism is a mechanism that assists an operation of the second steering wheel by the second assist motor, The second control unit includes a second control circuit disposed on a second substrate; the second control circuit has a third switching element and a fourth switching element connected in series between a pair of terminals to which a voltage is applied, and a fifth switching element and a sixth switching element connected in series between the terminals and in parallel with the third switching element and the fourth switching element, the second auxiliary motor is connected between an intermediate node between the third switching element and the fourth switching element and an intermediate node between the fifth switching element and the sixth switching element, The first substrate and the second substrate are common to each other, The first switching element and the second switching element, and the third switching element and the fourth switching element are common to each other and are mounted at a common position on the first substrate and the second substrate.

[0008] The forklift according to the present invention comprises: A forklift including a steering mechanism, an auxiliary motor for assisting the steering operation, and a control unit for controlling the auxiliary motor, the assist mechanism is a mechanism that assists the steering operation by hydraulic pressure, the auxiliary motor is a pump motor that drives a hydraulic pump, The control unit has a control circuit disposed on a substrate, The control circuit has a first switching element and a second switching element connected in series between a pair of terminals to which a voltage is applied, and the pump motor is connected between an intermediate node between the first switching element and the second switching element and one of the pair of terminals. Effect of the Invention

[0009] According to the present invention, it is possible to obtain an effect of reducing the manufacturing cost of the steering assist mechanism. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing a forklift according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing a configuration of an operation unit of the forklift shown in FIG. [Diagram 3] FIG. 2 is a block diagram showing the configuration of an electrical system and a mechanical system of the first forklift. [Figure 4] FIG. 2 is a diagram showing a first substrate and a first control circuit. [Diagram 5] FIG. 2 is a block diagram showing the configuration of an electrical system and a mechanical system of the second forklift. [Figure 6] FIG. 4 is a diagram showing a second substrate and a second control circuit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Fig. 1 is a diagram showing a first forklift 300A according to an embodiment of the present invention. Fig. 2 is a diagram showing the configuration of an operation unit of the first forklift 300A.

[0012] The forklift series of this embodiment includes a first forklift 300A and a second forklift 300B. The first forklift 300A and the second forklift 300B are two forklifts that employ different assist mechanisms to assist the operation of steering wheels 704A and 704B.

[0013] As shown in Fig. 1, the first forklift 300A is equipped with a vehicle body 302 including wheels 610, 612 and a driver's seat 301, a fork 303 extending forward of the vehicle body 302, a backrest 304 located behind the fork 303, and a fork drive unit 201 for driving the fork 303. As shown in Fig. 2, the driver's seat 301 is equipped with a steering wheel 704A for steering, a forward / reverse lever 712 for switching between forward and reverse, a lift lever 706 for raising and lowering the fork 303, an accelerator pedal 708 for accelerating the vehicle, a brake pedal 710 for braking the vehicle, and an ignition switch 702 for switching between supplying and cutting off power supply voltage to each drive unit.

[0014] The second forklift 300B similarly has the above-mentioned components. Hereinafter, the steering 704A of the first forklift 300A will be referred to as the "first steering 704A," and the steering 704B of the second forklift 300B will be referred to as the "second steering 704B."

[0015] <First forklift> 3 is a block diagram showing the configuration of the electrical system and the mechanical system of the first forklift 300A. The first forklift 300A includes a first steering 704A, a first assist mechanism 118A having a first assist motor M3A that assists the operation of the first steering 704A, and a first control unit 800A that controls the first assist motor M3A. The first assist mechanism 118A is a mechanism that assists the operation of the first steering 704A by hydraulic pressure (e.g., hydraulic pressure), and the first assist motor M3A is a pump motor that drives a hydraulic pump PM.

[0016] Specifically, the first assist mechanism 118A is a hydraulic actuator that applies a rotational force to the first steering wheel 704A as an assist force for steering operation. The first assist mechanism 118A changes the magnitude of the rotational force by the pressure of a liquid (e.g., hydraulic oil). Furthermore, the first assist mechanism 118A can switch the direction in which the assist force is applied by mechanically interlocking with the rotation direction of the steering wheel 704A. In other words, it can switch between applying a left rotation assist force and applying a right rotation assist force.

[0017] The first auxiliary motor M3A is an electric motor that is driven in one direction by a direct current flowing in the same direction. When a large torque is output from the first auxiliary motor M3A, the hydraulic pressure output from the hydraulic pump PM increases, and the assist force of the steering operation of the first auxiliary mechanism 118A increases.

[0018] The first control unit 800A has a first control circuit 810A arranged on the first substrate 802A. The first control unit 800A further includes a controller 110 and an encoder 122 that detects the rotational position and rotational speed of the first steering wheel 704A. The controller 110 is a microcomputer and operates according to a control program. The controller 110 receives a detection signal from the encoder 122 and controls the first control circuit 810A so as to generate an assist force whose magnitude changes according to the rotational speed of the first steering wheel 704A, etc.

[0019] The fork driving device 201 has a lifting mechanism 606 that supports the fork 303 so that it can be raised and lowered, a hydraulic actuator 116 that provides power to the lifting mechanism 606, a hydraulic motor M2 that supplies hydraulic pressure to the hydraulic actuator 116, and a control circuit 102 that drives the hydraulic motor M2. The controller 110 drives the hydraulic motor M2 via the control circuit 102 based on operation information of the lift lever 706, and raises and lowers the fork 303. The control circuit 102 is mounted on a circuit board 900.

[0020] The first forklift 300A further includes a traveling motor M1, a gear box 112 and a drive shaft 114 for transmitting the power of the traveling motor M1 to the wheels 610, and a control circuit 200 for driving the traveling motor M1. The controller 110 drives the traveling motor M1 via the control circuit 200 based on operation information of the forward / reverse lever 712 and the accelerator pedal 708 to drive the vehicle body 302. The control circuit 200 is mounted on a circuit board 900.

[0021] The first forklift 300A further includes a battery 100 that supplies a DC power supply voltage. The battery 100 is connected to the first board 802A and the circuit board 900 via power lines, and supplies the power supply voltage to the first control circuit 810A and the control circuits 102 and 200.

[0022] <Second forklift> 5 is a block diagram showing the configuration of the electrical system and the mechanical system of the second forklift 300B. The second forklift 300B includes a second steering 704B, a second assist mechanism 118B having a second assist motor M3B that assists the operation of the second steering 704B, and a second control unit 800B that controls the second assist motor M3B.

[0023] The second assist mechanism 118B is a mechanism that assists the operation of the second steering wheel 704B by the second assist motor M3B. That is, the second assist mechanism 118B directly assists the operation of the second steering wheel 704B by the second assist motor M3B (that is, by transmitting the mechanical power as it is).

[0024] Specifically, the second assist mechanism 118B is a mechanical transmission mechanism that applies a force to rotate the second steering wheel 704B as an assist force for steering operation. The second assist motor M3B is an electric motor that can be rotated in the forward and reverse directions by passing a direct current in the forward and reverse directions. When the second assist motor M3B is driven in the forward direction, the second assist mechanism 118B applies an assist force in the forward direction to the second steering wheel 704B. When the second assist motor M3B is driven in the reverse direction, the second assist mechanism 118B applies an assist force in the reverse direction to the second steering wheel 704B.

[0025] The second control unit 800B has a second control circuit 810B arranged on the second substrate 802B. The second control unit 800B further includes a controller 110 and an encoder 122 that detects the rotational position and rotational speed of the second steering wheel 704B. The controller 110 is a microcomputer and operates according to a control program. The controller 110 receives a detection signal from the encoder 122 and controls the second control circuit 810B so that an assist force is generated in a direction corresponding to the rotational direction of the second steering wheel 704B and of a magnitude corresponding to the rotational speed, etc. of the second steering wheel 704B.

[0026] The second forklift 300B further includes a fork drive device 201, a traveling motor M1, a gear box 112, a drive shaft 114, control circuits 102, 200, a circuit board 900, and a battery 100, similar to the first forklift 300A.

[0027] <First Substrate 802A and Second Substrate 802B> The first board 802A of the first forklift 300A and the second board 802B of the second forklift 300B have different circuits mounted thereon, but the boards themselves are the same. More specifically, the first board 802A and the second board 802B are provided with the same patterns (holes and lands for solder connection, pattern wiring, etc.). In other words, if the elements mounted on the boards and the conductors such as power lines and signal lines connected to the boards are removed, the first board 802A and the second board 802B will have the same configuration.

[0028] <First Substrate 802A and First Control Circuit 810A> 4 is a diagram showing the first substrate 802A and the first control circuit 810A. The first control circuit 810A has a first switching element Q1 and a second switching element Q2 connected in series between a pair of terminals t1, t2 to which a voltage is applied. A first auxiliary motor M3A, which is a pump motor, is connected between an intermediate node n1 between the first switching element Q1 and the second switching element Q2 and one terminal t2 of the pair of terminals t1, t2.

[0029] Specifically, the voltage applied to terminals t1 and t2 is the power supply voltage of the battery 100, and terminal t2 is a ground terminal. The first switching element Q1 and the second switching element Q2 are FETs (Field Effect Transistors) that are turned on / off by controlling a control terminal (gate terminal), but similar switching elements such as bipolar transistors may also be used. Hereinafter, the terminal to which a control signal that switches the open / closed state of the switching element is input is referred to as the "control terminal," and both ends of the current path opened / closed by the switching element are referred to as the "current terminals."

[0030] The first control circuit 810A also includes an input capacitor C1 that stabilizes the voltage input to terminals t1 and t2, and drive circuits D1 and D2 that receive control signals from the controller 110 and drive the control terminals of the first switching element Q1 and the second switching element Q2, respectively.

[0031] The first substrate 802A has terminals t1 and t2, connection parts v1a to v4a, v1b to b4b capable of connecting two terminals of each of the four elements constituting a bridge circuit, and motor connection parts v5a and v5b to which the wiring of the first auxiliary motor M3A is connected. The pair of motor connection parts v5a and v5b are provided at two intermediate nodes n1 and n2 of the bridge circuit, respectively. The connection parts include terminals of elements via a bonding material such as solder, lands, pads or through holes to which a conductor or bus bar can be connected, or terminals of a socket into which an element can be fitted.

[0032] The first substrate 802A further has a pair of jumper connecting parts v6a, v6b that conduct between two points of the bridge circuit. One jumper connecting part v6a is short-circuited to one of the fourth connecting parts v4a, v4b, and the other jumper connecting part v6b is short-circuited to the other of the fourth connecting parts v4a, v4b. The fourth connecting parts v4a, v4b may also serve as the jumper connecting parts v6a, v6b, respectively. The two points of the bridge circuit correspond to two points on a circuit opened and closed by a sixth switching element Q6 on the second substrate 802B described later, and specifically correspond to the pair of connecting parts v4a, v4b.

[0033] The current terminals of the first switching element Q1 are connected to the first connecting parts v1a and v1b, and the current terminals of the second switching element Q2 are connected to the second connecting parts v2a and v2b. Furthermore, the third connecting parts v3a and v3b are open, and a jumper J1 is connected to the jumper connecting parts v6a and v6b. The jumper J1 is an element including an electric wire, a pin, or a short-circuiting conductor that short-circuits two points of an electric circuit. The jumper J1 shorts a pair of fourth connecting parts v4a and v4b.

[0034] Furthermore, power supply lines Lp and Ln from the battery 100 are connected to terminals t1 and t2, respectively, and wiring of the first auxiliary motor M3A is connected to motor connection parts v5a and v5b.

[0035] With this configuration, the controller 110 drives and controls the first auxiliary motor M3A by operating the first switching element Q1 and the second switching element Q2 as follows. That is, the controller 110 alternately repeats a first state in which the first switching element Q1 is ON and the second switching element Q2 is OFF, and a second state in which the first switching element Q1 is OFF and the second switching element Q2 is ON. As a result, in the first state, the power supply voltage is applied to the coil of the first auxiliary motor M3A, and torque is generated in the first auxiliary motor M3A. Subsequently, in the second state, a current path is formed that passes through the ground point, the second switching element Q2, the first auxiliary motor M3A, the jumper J1, and the ground point in this order, and the current flowing through the coil of the first auxiliary motor M3A is not interrupted. The controller 110 controls the torque generated by the first auxiliary motor M3A by changing the time ratio between the first state and the second state.

[0036] Then, the controller 110 operates the first control circuit 810A so that the torque of the first auxiliary motor M3A becomes large when a large assist force is required for the operation of the first steering wheel 704A, for example, at a high rotation speed, based on the output of the encoder 122 representing the rotation speed of the first steering wheel 704A. On the other hand, the controller 110 operates the first control circuit 810A so that the torque of the first auxiliary motor M3A becomes small when a small assist force is required for the operation of the first steering wheel 704A, for example, at a low rotation speed. Furthermore, the direction of the assist force is switched by mechanical interlocking based on the rotation direction of the first steering wheel 704A. Through such control and operation, a force that appropriately assists the operation of the first steering wheel 704A by the driver can be generated.

[0037] Furthermore, according to the control method of the first control circuit 810A as described above, the first switching element Q1 and the second switching element Q2 switch states in synchronization with each other, so that the above-mentioned first state current and second state current can flow. That is, synchronous rectification can be realized. The above-mentioned first state current and second state current can also be generated by replacing the second switching element Q2 with a diode. However, the second switching element Q2 in the on state can pass a current with less loss than a diode. Therefore, the above-mentioned synchronous rectification can reduce the loss of the first control circuit 810A and improve the efficiency of the first control circuit 810A.

[0038] <Second Substrate 802B and Second Control Circuit 810B> The second control circuit 810B has a third switching element Q3 and a fourth switching element Q4 connected in series between a pair of terminals t1 and t2 to which a voltage is applied, and a fifth switching element Q5 and a sixth switching element Q6 connected in series between the terminals t1 and t2 and in parallel with the third switching element Q3 and the fourth switching element Q4. A second auxiliary motor M3B is connected between an intermediate node n1 between the third switching element Q3 and the fourth switching element Q4 and an intermediate node n2 between the fifth switching element Q5 and the sixth switching element Q6.

[0039] The third switching element Q3 and the fourth switching element Q4 mounted on the second substrate 802B are common to the first switching element Q1 and the second switching element Q2 mounted on the first substrate 802A described above, and are mounted at a common position on the first substrate 802A and the second substrate 802B.

[0040] Specifically, the voltage applied to terminals t1 and t2 is the power supply voltage of the battery 100, and terminal t2 is a ground terminal. The third switching element Q3 to the sixth switching element Q6 can be elements similar to the first switching element Q1 and the second switching element Q2 described above.

[0041] The second control circuit 810B also includes an input capacitor C1 that stabilizes the voltage input to terminals t1 and t2, and drive circuits D3 to D6 that receive control signals from the controller 110 and drive the control terminals of the third switching element Q3 to the sixth switching element Q6, respectively.

[0042] As described above, the second board 802B has a common configuration with the first board 802A, and has connection portions v1a-v4a, v1b-v4b to which element terminals can be connected, motor connection portions v5a, v5b, and jumper connection portions v6a, v6b.

[0043] The current terminals of the third switching element Q3 are connected to the first connecting parts v1a and v1b, and the current terminals of the fourth switching element Q4 are connected to the second connecting parts v2a and v2b. Furthermore, the current terminals of the fifth switching element Q5 are connected to the third connecting parts v3a and v3b, and the current terminals of the sixth switching element Q6 are connected to the fourth connecting parts v4a and v4b. The jumper J1 connected to the first board 802A described above is not attached to the second board 802B.

[0044] Furthermore, power supply lines Lp, Ln from the battery 100 are connected to terminals t1, t2, respectively, and wiring of the second auxiliary motor M3B is connected to motor connection parts v5a, v5b.

[0045] With this configuration, the controller 110 drives and controls the second auxiliary motor M3B by operating the third switching element Q3 to the sixth switching element Q6 as follows. That is, when the generation of forward torque of the second auxiliary motor M3B is requested, the controller 110 alternately repeats a first state in which the third switching element Q3 is turned on, the fourth switching element Q4 is turned off, the fifth switching element Q5 is turned off, and the sixth switching element Q6 is turned on, and a second state in which the third switching element Q3 is turned off, the fourth switching element Q4 is turned on, the fifth switching element Q5 is turned on, and the sixth switching element Q6 is turned off. As a result, in the first state, the power supply voltage is applied to the coil of the second auxiliary motor M3B, and forward torque is generated in the second auxiliary motor M3B. Subsequently, in the second state, a current path is formed that returns from the ground point to the battery 100 via the fourth switching element Q4, the second auxiliary motor M3B, and the fifth switching element Q5, and the current flowing through the coil of the second auxiliary motor M3B is not interrupted. The controller 110 controls the forward torque generated by the second auxiliary motor M3B by changing the time ratio between the first state and the second state.

[0046] Furthermore, when the controller 110 is requested to generate torque in the reverse direction of the second auxiliary motor M3B, the controller 110 alternately repeats a third state in which the third switching element Q3 is turned off, the fourth switching element Q4 is turned on, the fifth switching element Q5 is turned on, and the sixth switching element Q6 is turned off, and a fourth state in which the third switching element Q3 is turned on, the fourth switching element Q4 is turned off, the fifth switching element Q5 is turned off, and the sixth switching element Q6 is turned on. As a result, in the third state, the power supply voltage is applied in the reverse direction to the coil of the second auxiliary motor M3B, and a torque in the reverse direction is generated in the second auxiliary motor M3B. Subsequently, in the fourth state, a current path is formed that returns from the ground point to the battery 100 via the sixth switching element Q6, the second auxiliary motor M3B, and the third switching element Q3, and the current flowing through the coil of the second auxiliary motor M3B is not interrupted. The controller 110 controls the torque in the reverse direction generated by the second auxiliary motor M3B by changing the time ratio between the third state and the fourth state.

[0047] Then, the controller 110 operates the second control circuit 810B so that the torque of the second auxiliary motor M3B becomes larger when a large assist force is required for the operation of the second steering wheel 704B, for example, at a high rotation speed, based on the output of the encoder 122 representing the rotation direction and rotation speed of the second steering wheel 704B. On the other hand, the controller 110 operates the second control circuit 810B so that the torque of the second auxiliary motor M3B becomes smaller as the assist force applied to the operation of the second steering wheel 704B becomes smaller, for example, at a low rotation speed. Furthermore, the controller 110 controls the direction of the torque generated by the second auxiliary motor M3B based on the rotation direction of the second steering wheel 704B. By such control, a force that appropriately assists the operation of the second steering wheel 704B by the driver can be generated.

[0048] <Relationship with other circuit boards> As shown in Fig. 3, the first substrate 802A is configured separately from the circuit substrate 900 on which the control circuits 102, 200 that control the other drive devices are mounted. Similarly, as shown in Fig. 5, the second substrate 802B is configured separately from the circuit substrate 900 on which the control circuits 102, 200 that control the other drive devices are mounted. Separate means that the substrates themselves are not connected, and one substrate can be moved while the other substrate is fixed. Even if the substrates are electrically connected to each other via conductors or bus bars, if the one substrate can be moved while the other substrate is fixed by disconnecting the conductors or bus bars, these substrates are separate.

[0049] The circuit board 900 is a board on which the control circuit 102 that raises and lowers the forks 303 and the control circuit 200 that controls travel are mounted, but the circuit board 900 may also be mounted with a control circuit that controls other drive devices. Alternatively, the circuit board 900 may be two circuit boards on which the control circuit 102 and the control circuit 200 are mounted, respectively.

[0050] Since the first board 802A and the second board 802B are separate from the other circuit board 900, when changing the method of assisting the steering operation, modifying the control circuit (first control circuit 810A, second control circuit 810B, etc.) that assists the steering operation, or repairing it, it is possible to deal with this by removing the first board 802A or the second board 802B from the vehicle body 302 while leaving the circuit board 900 on which the other control circuits 102, 200 are mounted. Therefore, it is possible to reduce the maintenance cost of the configuration that assists the steering operation and to shorten the maintenance period.

[0051] As described above, the series of forklifts according to this embodiment includes a first forklift 300A having a first assist mechanism 118A that assists steering operation by hydraulic pressure, and a second forklift 300B having a second assist mechanism 118B that directly assists steering operation by the power of a second assist motor M3B. Furthermore, the first forklift 300A and the second forklift 300B share a first board 802A that mounts a first control circuit 810A that assists steering operation, and a second board 802B that mounts a second control circuit 810B. This reduces the manufacturing cost and shortens the manufacturing time of the first board 802A and the second board 802B.

[0052] Furthermore, the first switching element Q1 and the second switching element Q2 mounted on the first substrate 802A and the third switching element Q3 and the fourth switching element Q4 mounted on the second substrate 802B are common and are mounted at the same position on the substrate. Therefore, when the first control circuit 810A is mounted and when the second control circuit 810B is mounted, a part or all of the mounting location of the circuit is made common. Therefore, compared with the case where each control circuit is provided at a different location on one substrate, it is possible to reduce the size of the substrate. Therefore, it is possible to reduce the size of the first substrate 802A and the second substrate 802B, and to save space in the substrate housing location of the vehicle body 302 that houses the first substrate 802A or the second substrate 802B of the vehicle body 302.

[0053] Furthermore, according to the forklift series of this embodiment, the jumper J1 of the first control circuit 810A can be arranged at the location where the sixth switching element Q6 of the second control circuit 810B is mounted on the first board 802A and the second board 802B. Therefore, the wiring pattern on the board to which the sixth switching element Q6 is connected on the second board 802B can be made common to the wiring pattern on the board to which the jumper J1 is connected on the first board 802A. Therefore, the first board 802A and the second board 802B can be made more compact.

[0054] Furthermore, according to the series of forklifts of this embodiment, the first board 802A and the second board 802B are configured separately from the other circuit boards 900. Therefore, when changing the method of assisting steering operation, modifying the control circuits (the first control circuit 810A, the second control circuit 810B, etc.) that assist steering operation, or repairing them, it is possible to deal with the situation by removing only the first board 802A or the second board 802B from the vehicle body 302. Therefore, it is possible to reduce the maintenance cost of the configuration that assists steering operation and shorten the maintenance period.

[0055] Furthermore, according to the first forklift 300A of this embodiment, the first auxiliary mechanism 118A is provided to assist the operation of the first steering 704A by the hydraulic pressure generated by driving the first auxiliary motor M3A. The first control circuit 810A of the first control unit 800A, which controls the first auxiliary motor M3A, has the above-mentioned first switching element Q1 and second switching element Q2, and the first auxiliary motor M3A is connected between the intermediate node n1 and the terminal t2. With this configuration, the second board 802B, which mounts the second control circuit 810B of a different method, and the first board 802A can be made common, and further, the first switching element Q1 and the second switching element Q2, and their mounting locations can be made common with the second board 802B. Therefore, it is possible to reduce the manufacturing cost of the first board 802A and shorten the manufacturing period. In addition, it is possible to reduce the size of the first board 802A and save the space of the mounting location of the first board 802A on the vehicle body 302. Furthermore, since the chopper circuit enables synchronous rectification in the first control circuit 810A that controls the first auxiliary motor M3A, loss in the first control circuit 810A can be reduced.

[0056] The above describes the embodiments of the present invention. However, the present invention is not limited to the above embodiments. For example, in the above embodiment, the power supply voltage output from the battery 100 is applied in series as the voltage applied to the terminals t1 and t2 of the first board 802A and the second board 802B. However, the power supply voltage output from the battery 100 via other circuits such as a filter circuit or a voltage conversion circuit may be applied. In the above embodiment, the third switching element Q3 and the fourth switching element Q4 mounted on the second board 802B are common to the first switching element Q1 and the second switching element Q2 mounted on the first board 802A. However, the fifth switching element Q5 and the sixth switching element Q6 mounted on the second board 802B may be common to the first switching element Q1 and the second switching element Q2 mounted on the first board 802A. In this case, the jumper J1 of the first board 802A may be configured to be provided at the location of the fourth switching element Q4 of the second board 802B. In the present invention, the third and fourth switching elements and the fifth and sixth switching elements are configured symmetrically. Therefore, the third and fourth switching elements according to the present invention may be considered to correspond to the fifth and sixth switching elements Q5 and Q6 of the embodiments, and the fifth and sixth switching elements according to the present invention may be considered to correspond to the third and fourth switching elements Q3 and Q4 of the embodiments. Other details shown in the embodiments may be modified as appropriate without departing from the spirit of the invention. [Explanation of symbols]

[0057] 100 batteries 102, 200 Control circuit 110 Controller 116 Hydraulic Actuator 118A 1st auxiliary mechanism 118B 2nd auxiliary mechanism 201 Fork drive unit 300A No.1 Forklift 300B No. 2 Forklift 301 Driver's seat 302 Body 303 Fork 606 Lifting mechanism 610, 612 wheels 712 Forward / reverse lever 702 Ignition Switch 704A No. 1 steering 704B 2nd steering 706 Lift Lever 708 Accelerator Pedal 710 Brake pedal 800A First control section 802A 1st board 810A First control circuit 800B Second control section 802B 2nd board 810B Second control circuit 900 Circuit Board M1 Drive motor M2 Hydraulic Motor M3A 1st Auxiliary Motor M3B 2nd Auxiliary Motor PM hydraulic pump Q1 First switching element Q2 Second switching element Q3 Third switching element Q4 Fourth switching element Q5 Fifth switching element Q6 6th switching element J1 Jumper t1, t2 terminals v1a~v4a, v1b~b4b connection v5a, v5b motor connections Connections for v6a, v6b jumpers n1, n2 intermediate nodes

Claims

1. A first forklift including a first steering mechanism, a first auxiliary motor that assists the operation of the first steering mechanism, and a first control unit that controls the first auxiliary motor; a second forklift including a second steering mechanism, a second auxiliary motor that assists the operation of the second steering mechanism, and a second control unit that controls the second auxiliary motor; A series of forklift trucks comprising: the first assist mechanism is a mechanism that assists an operation of the first steering wheel by hydraulic pressure, the first auxiliary motor is a pump motor that drives a hydraulic pump, The first control unit has a first control circuit disposed on a first substrate, the first control circuit has a first switching element and a second switching element connected in series between a pair of terminals to which a voltage is applied, the pump motor is connected between an intermediate node between the first switching element and the second switching element and one of the pair of terminals, the second assist mechanism is a mechanism that assists an operation of the second steering wheel by the second assist motor, The second control unit includes a second control circuit disposed on a second substrate; the second control circuit has a third switching element and a fourth switching element connected in series between a pair of terminals to which a voltage is applied, and a fifth switching element and a sixth switching element connected in series between the terminals and in parallel with the third switching element and the fourth switching element, the second auxiliary motor is connected between an intermediate node between the third switching element and the fourth switching element and an intermediate node between the fifth switching element and the sixth switching element, The first substrate and the second substrate are common to each other, the first switching element and the second switching element, and the third switching element and the fourth switching element are common to each other and are mounted at a common position on the first substrate and the second substrate; Forklift series.

2. a jumper can be disposed in a location on the first substrate and the second substrate where the sixth switching element is disposed when the second control circuit is configured, when the first control circuit is configured; A series of forklift trucks according to claim 1.

3. The first board and the second board are configured separately from a circuit board on which a control circuit for controlling other driving devices is mounted. A series of forklift trucks according to claim 1.

4. A forklift including a steering mechanism, an auxiliary motor for assisting the steering operation, and a control unit for controlling the auxiliary motor, the assist mechanism is a mechanism that assists the steering operation by hydraulic pressure, the auxiliary motor is a pump motor that drives a hydraulic pump, The control unit has a control circuit disposed on a substrate, the control circuit has a first switching element and a second switching element connected in series between a pair of terminals to which a voltage is applied, and the pump motor is connected between an intermediate node between the first switching element and the second switching element and one of the pair of terminals. forklift.

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