JP2013203114A - Industrial vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an industrial vehicle capable of suppressing slippage of wheels during turning.SOLUTION: A steering mechanism 20 is provided within a vehicle body of a forklift which is traveled with four wheels comprising a pair of left and right steering wheels 14L and 14R and drive wheels, and turns the steering wheels 14L, 14R in accordance with a steering manipulation direction and a manipulation amount of an operator. Together with the steering mechanism 20, a turning angle adjusting means (e.g., a steering arm 31 as an elastic member) is provided for adjusting turning angles in the left-side steering wheel 14L and the right-side steering wheel 14R, such that turning centers of the steering wheels turned by the steering mechanism become closer on rotary shafts of the pair of drive wheels. Thus, slippage of wheels during turning of the forklift can be suppressed and as a result, a wearing amount of tires can be suppressed or operability by the operator can be improved.

Description

  The present invention relates to an industrial vehicle that travels on four wheels including a pair of left and right steering wheels and drive wheels.

Conventionally, as this type of industrial vehicle, a forklift having a pair of left and right rear wheels as steering wheels and a pair of left and right front wheels as driving wheels is known.
Further, such a forklift steering mechanism is generally configured such that the piston rod of the steering cylinder expands / contracts in the vehicle width direction by an amount of movement corresponding to the steering operation direction and operation amount of the operator. A driving force required for turning is transmitted to a pair of left and right steering wheels connected to the piston rod via a link portion such as an arm.

  In such a steering mechanism, in order to make the turning radius of the forklift as small as possible, both steered wheels are in a C-shaped state at the maximum turning angle (a C-shaped state opened on the rotating shaft side of the drive wheel). A link mechanism is employed in which the turning amount of the steering wheel located on the extension side of the piston rod is increased by a predetermined percentage in advance from the turning amount of the steering wheel located on the contraction side so that the turning is possible.

  In the steering mechanism having such a configuration, the turning angle of the steering wheel on the turning direction side according to the steering operation direction is always larger by a predetermined ratio than the turning angle of the steering wheel on the opposite side. Even if the angle exceeds 90 degrees with respect to the straight-ahead position, the opposite steering wheel does not reach 90 degrees with respect to the straight-ahead position, so that both steered wheels are in a C shape at the maximum turning angle. (For example, refer to Patent Document 1).

Japanese Patent Laid-Open No. 11-001179

  However, as in the forklift described in Patent Document 1, when both steered wheels are in a U shape at the maximum turning angle, the turning center of both steered wheels (rear wheels) is on the rotation axis of the drive wheels (on the front wheel axis). However, in the state where the maximum turning angle is not reached, there is a possibility that the turning center of the rear wheel is displaced from the front wheel axis because the movement amount of the left and right piston rods is different by a predetermined ratio.

  As a result, if the turning center of the rear wheel deviates from the front wheel axis, the front wheel slips in the direction of deviation of the turning center or the rear wheel slides sideways. There is a risk that the operability by the operator may be reduced.

  In order to solve the above-described problems, an object of the present invention is to provide an industrial vehicle capable of suppressing wheel slippage during turning.

  The industrial vehicle according to claim 1, which is an invention made to achieve the above object, is an industrial vehicle that travels on four wheels including a pair of left and right steering wheels and a drive wheel. A steering mechanism for turning a pair of steering wheels according to the amount is provided.

  In the present invention, with such a configuration, the turning angle adjusting means causes the steering wheel on the left side and the steering on the right side so that the turning center of the steering wheel turned by the steering mechanism approaches the rotation axis of the pair of drive wheels. Adjust each turning angle in the wheel.

  Therefore, according to the present invention, the turning angle adjusting means brings the turning center of the steering wheel closer to the rotation axis of the driving wheel (if the steering wheel is the rear wheel and the driving wheel is the front wheel, the front wheel axis). The slippage of the wheel during turning can be suppressed. Thereby, the abrasion amount of a tire can be suppressed or the operativity by an operator can be improved.

  The industrial vehicle of the present invention includes a drive mechanism that rotates a pair of drive wheels according to an accelerator operation amount of an operator, a left drive wheel that is rotated by the drive mechanism according to a steering operation direction and an operation amount, and a right drive wheel. You may provide the rotation difference setting means which sets the rotation difference with a driving wheel. In other words, when attention is paid only to the drive wheels, a turning center is generated on the rotation axis of the drive wheels due to the rotation difference.

  In this case, as described in claim 2, the turning angle adjusting means sets each turning angle so that the turning center of the steering wheel approaches the turning center of the drive wheel based on the rotation difference set by the rotation difference setting means. It is desirable to adjust.

  According to such a configuration, the turning center of the steered wheel approaches the turning center of the drive wheel (on the rotation axis of the drive wheel), so that wheel slippage during turning can be suppressed, and the turning of the industrial vehicle The radius can be made smaller.

  In the present invention, as described in claim 3, the steering mechanism is disposed between the left steering wheel and the right steering wheel, and the vehicle width is set by the amount of movement corresponding to the steering operation direction and the operation amount. It may be configured by a steering cylinder having a piston rod that extends and contracts in the direction, and the turning angle adjusting means may be provided in a link portion that connects both ends of the piston rod and a pair of steering wheels.

According to such a configuration, it is possible to suppress the slipping of the wheel during turning without adding a complicated design change to the configuration of the steering cylinder.
In addition, in the industrial vehicle according to claim 3, as described in claim 4, the turning angle adjusting means is provided on the left side by a propulsive force applied in a direction propelled by the industrial vehicle based on the rotation difference of the drive wheels. A configuration may be made of an elastic member that autonomously adjusts each turning angle of the steering wheel and the right steering wheel.

  In such a configuration, due to the elastic force of the elastic member provided in the link portion, the traveling direction of the vehicle body by the steering wheel coincides with the direction propelled by the industrial vehicle based on the rotation difference of the drive wheel, Thereby, the slip of the wheel at the time of turning can be suppressed, and control by a microcomputer or the like for adjusting the turning angle can be omitted.

  Furthermore, in the industrial vehicle according to claim 4, as described in claim 5, the elastic member may be configured by a plate-like or coil-like spring. In this case, by changing the thickness, wire diameter, number of turns, etc. of the spring, the amount of deviation between the direction propelled by the industrial vehicle and the traveling direction of the vehicle body by the steered wheel is absorbed based on the rotational difference of the drive wheel Therefore, it is possible to easily manufacture an elastic member according to the elastic force required by, for example, simulation or experiment.

  Further, in the industrial vehicle according to claim 3, the link portion includes a tie rod connected to both ends of the piston rod, and a steering arm that connects the end portion of the tie rod and each steered wheel. May be. In this case, as described in claim 6, the elastic member is preferably formed as a tie rod or a steering arm.

According to such a configuration, it is possible to suppress slipping of the wheels during turning without increasing the components of the steering mechanism.
By the way, in the industrial vehicle according to the third aspect, instead of the configuration in which the elastic member is provided at the link portion in the steering mechanism, the turning by the steering mechanism according to the steering operation direction and the operation amount as described in the seventh aspect. Under the configuration comprising turning angle setting means for setting the turning angles of the left steering wheel and the right steering wheel so that the turning center of the steering wheel is positioned on the rotation axis of the pair of driving wheels, An aspect may be sufficient.

  That is, the turning angle adjusting means is an auxiliary actuator for individually adjusting the turning angles of the left steering wheel and the right steering wheel so as to be the respective turning angles set by the turning angle setting means. May be adopted.

  According to such a configuration, the turning angle of each steered wheel can be actively adjusted by the auxiliary actuator provided in the link portion of the steering mechanism, so that the adjustment accuracy can be improved.

  Alternatively, in the industrial vehicle according to the present invention, as described in claim 8, the left side of the left steering wheel and the right side steering wheel are individually turned based on the configuration including the turning angle setting means. The left steering wheel and the right steering mechanism are the left steering wheel and the right steering mechanism so that the left steering mechanism and the right steering mechanism have the respective turning angles set by the turning angle setting means as the turning angle adjusting means. You may employ | adopt the structure which adjusts each turning angle in a steering wheel, respectively.

According to such a configuration, the turning angle of each steered wheel can be actively adjusted without providing an auxiliary actuator in the link portion, and the adjustment accuracy can be improved.
Further, in the industrial vehicle according to claim 8, for example, as described in claim 9, the left steering mechanism and the right steering mechanism are provided with electric motors respectively provided for the left steering wheel and the right steering wheel. Alternatively, a configuration having a hydraulic cylinder may be employed.

  The industrial vehicle of the present invention may be an industrial vehicle that travels with four wheels including a pair of left and right steering wheels and drive wheels, and may be applied to an agricultural vehicle such as a combine, or a luggage such as a forklift. You may apply to the special vehicle which conveys. In the latter case, the present invention can be suitably used for a counterbalance forklift.

(A) is a side view which shows the whole structure of the forklift which concerns on 1st Embodiment of this invention, (b) is a block diagram which shows the internal structure of a vehicle main body. (A) is a schematic diagram for demonstrating the rotation difference of a driving wheel and the turning angle of a steering wheel, (b) is a schematic diagram for demonstrating the turning center of a driving wheel based on a rotation difference. (A) is a front view which shows the structure of a steering mechanism, (b) is the top view. (A) is a schematic diagram for demonstrating the state of the steering wheel at the time of the maximum turning angle, (b) is a schematic diagram for demonstrating an example of a turning angle adjustment means. (A) is a block diagram which shows the internal structure of the vehicle main body in 2nd Embodiment, (b) is a schematic diagram which shows the structure of the steering mechanism in 2nd Embodiment, (c) is 2nd. It is a schematic diagram which shows the modification which concerns on the structure of the steering mechanism in embodiment.

A counterbalance forklift as an industrial vehicle according to an embodiment to which the present invention is applied will be described below with reference to the drawings.
[First Embodiment / Overall Configuration]
A counterbalance forklift 1 according to the first embodiment shown in FIG. 1A is used for transporting goods (for example, cargo handling work in factories, warehouses, cargo stations, harbors, etc.) and is installed in front of the vehicle body. This is a four-wheel type forklift provided with a counterweight (not shown) at the rear of the vehicle body in order to balance the cargo handling unit 3. Hereinafter, the counterbalance forklift 1 is simply referred to as a forklift 1.

  The forklift 1 mainly includes a vehicle main body 2, a cargo handling unit 3 that handles luggage, front wheels 13 and rear wheels 14 that are used for traveling the forklift 1, and a driver seat 15 in which a driver gets.

  The vehicle body 2 is provided with a cargo handling section 3 on the front surface and a driver's seat 15 on the center of the upper surface. A pair of front wheels 13 is provided in front of the lower portion, and a pair of rear wheels 14 is provided in the lower rear portion. It is what has been. Further, as shown in FIG. 1B, drive mechanisms 21 </ b> L and 21 </ b> R that run the forklift 1, a battery (not shown), a steering mechanism 20 that turns the forklift 1, and a steering mechanism 20 are disposed inside the vehicle body 2. (See FIG. 1B)) and a hydraulic pressure generating unit (not shown) for supplying high-pressure oil used in the cargo handling unit 3, a control unit 30 for controlling these devices, and the like are housed.

  The driver's seat 15 is a part where a driver of the forklift 1, in other words, an operator (operator) who performs a cargo handling operation, gets on, a steering 16 used for steering the forklift 1, an accelerator 18 used for traveling the forklift 1, cargo handling. A lever 17 or the like used for the operation of the unit 3 is provided.

  The cargo handling unit 3 is mainly provided with a fork 11 that supports the load, an inner mast 7 to which the fork 11 is attached, an outer mast 8 that extends in the vertical direction, and a lift cylinder 9.

The inner mast 7 is disposed inside the outer mast 8 and is configured to be movable in the vertical direction along the outer mast 8.
The lift cylinder 9 is supplied with oil whose pressure has been increased from a hydraulic pressure generator housed in the vehicle main body 2 and performs an operation (extension / contraction operation) to expand and contract by the high-pressure oil. The lift cylinder 9 moves the inner mast 7 and the fork 11 up and down along the outer mast 8 by performing an expansion / contraction operation according to the operation direction and operation amount of the lever 17.

The front wheel 13 is a drive wheel that causes the forklift 1 to travel by being driven to rotate about the vehicle width direction by the drive mechanisms 21L and 21R.
The drive mechanisms 21L and 21R are a left drive mechanism 21L that rotates the left front wheel 13L as the left drive wheel and a right drive mechanism 21R that rotates the right front wheel 13R as the right drive wheel in accordance with a command from the control unit 30. Consists of. These drive mechanisms 21L and 21R are travel motors that cause the forklift 1 to travel with electric power supplied from a battery, and one travel motor is disposed on one front wheel 13. Note that the front wheel 13 and the traveling motor do not necessarily have to be arranged so that the rotation axis is coaxial, but the motor shaft of the traveling motor is offset to drive the traveling motor via a gear or the like, for example. It may be configured to transmit to the rotation shaft of the front wheel 13.

  The rear wheel 14 is a steering wheel that rotates the forklift 1 by being rotated about the vehicle height direction by the steering mechanism 20, and is a driven wheel that rotates in the vehicle width direction as the forklift 1 travels.

  The control unit 30 is mainly configured by a microcomputer including a CPU, a memory, and the like, and the CPU executes a drive control process for controlling the drive mechanisms 21L and 21R, for example, based on programs and data stored in the memory. .

  The memory of the control unit 30 stores a drive control map indicating the correlation between the amount of depression of the accelerator 18 (operation amount) and the rotation amounts (rotational speed) of the left front wheel 13L and the right front wheel 13R. The drive control map also shows the correlation between the operation direction and operation amount of the steering wheel 16 and the correction values for the rotational speeds of the left front wheel 13L and the right front wheel 13R. As shown in FIG. 2 (a), this correction value is obtained when the rotational speed Vα of the front wheel 13 (13R in the figure) located on the turning direction side of the rear wheel 14 is the front wheel 13 (13L in the figure) located on the opposite side. ) Is set to be smaller than the rotation speed Vβ.

  In the drive control process performed by the CPU of the control unit 30, the operation amount of the accelerator 18, the operation direction and the operation amount of the steering wheel 16 are input parameters, and the rotational speeds corresponding to these input parameters are stored in the memory. A command for rotating the left front wheel 13L and the right front wheel 13R to the read rotation speeds is output to the left drive mechanism 21L and the right drive mechanism 21R.

  As a result, when the rear wheel 14 turns, the front wheels 13L and 13R are driven to rotate at different rotational speeds Vα and Vβ. Therefore, as shown in FIG. 2B, the front wheels 13L and 13R based on this rotational difference are used. The turning center P is generated.

[Configuration of steering mechanism]
The steering mechanism 20 includes a steering cylinder 25 (see FIG. 3) that performs an expansion / contraction operation in the vehicle width direction in accordance with the operation direction and operation amount of the steering wheel 16. The steering cylinder 25 is supplied with oil whose pressure has been increased from a hydraulic pressure generator housed in the vehicle body 2, and performs an operation (extension / contraction operation) to expand and contract by the high-pressure oil.

  The steering cylinder 25 is a double-acting, double-sided rod-type hydraulic cylinder, as shown in FIG. 3, a piston rod 27 disposed between the left rear wheel 14L and the right rear wheel 14R, and a piston Link portions 28 are mainly provided to connect the distal ends of the rods 27 to the left rear wheel 14L and the right rear wheel 14R, respectively.

  The steering cylinder 25 extends and contracts the piston rod 27 in the vehicle width direction (left-right direction), thereby turning the rear wheel 14 attached to the link portion 28 around the vehicle height direction (vertical direction) axis. .

  The link portion 28 is fitted to the steering arm 31, the tie rod 29 connected to the tip portion of the piston rod 27, the steering arm 31 connected to the tip portion of the tie rod 29 opposite to the piston rod 27 side. A pivot shaft 33 is mainly provided.

  The tie rod 29 is a member formed in a curved shape. One end of the tie rod 29 is rotatably connected to the piston rod 27 via a connecting pin 35a, and the other end of the steering arm 29 is rotatable via a connecting pin 35b. 31 is connected.

  The turning shaft portion 33 supports the hub 37 to which the rear wheel 14 is attached so as to be rotatable about a shaft in the vehicle height direction through a bearing or the like (not shown). The turning shaft portion 33 is also configured as a part of a suspension (axle beam) 39 for positioning the axle of the rear wheel 14 and the like. The axle beam 39 is disposed above and parallel to the steering cylinder 25.

  The steering arm 31 is a plate-shaped member that transmits the expansion / contraction operation of the piston rod 27 together with the tie rod 29 to the turning shaft portion 33 and rotates the rear wheel 14 around the axis of the turning shaft portion 33. It is.

  Then, the tie rod 29 and the steering arm 31 are arranged such that the rear wheels 14 (right rear in the figure) are arranged on the extension side of the piston rod 27 as shown in FIG. The turning angle α of the wheel 14R is displaced so as to be larger by a predetermined ratio than the turning angle β of the rear wheel 14 (left rear wheel 14L in the figure) disposed on the contraction side of the piston rod 27. As a result, at the maximum turning angle of the rear wheel 14, as shown in FIG. 4A, the rear wheel 14 (the right rear wheel 14R in the drawing) disposed on the extension side exceeds 90 degrees with respect to the straight traveling position. The rear wheel 14 (left rear wheel 14L in the figure) arranged on the contraction side turns without turning 90 degrees, that is, the left and right rear wheels 14L, 14R are opened to the rotating shaft side of the front wheel 13. It turns in the state of the character.

  Further, the steering arm 31 of the present embodiment is an elastic member made of a leaf spring, and the elastic force of the steering arm 31 partially absorbs the expansion / contraction operation of the piston rod 27, as shown in FIG. The turning center of the rear wheel 14 is adjusted to the turning center P based on the rotational difference 13.

  More specifically, for example, when the driver operates the steering wheel 16 while the forklift 1 is traveling, the left front wheel 13L and the right front wheel 13R are rotationally driven at different speeds according to the operation direction and operation amount. At the turning center P of the front wheels 13L and 13R based on this rotation difference, the forklift 1 tries to turn in the direction shown by the solid line in FIG.

  At this time, on the other hand, both ends of the piston rod 27 are expanded and contracted at different rates in the vehicle width direction according to the operation direction and operation amount of the steering wheel 16, and the left rear wheel 14L and the right rear wheel Since the wheel 14R has a different turning angle, the turning center of the rear wheels 14L and 14R does not necessarily coincide with the turning center P, and is in the direction shown by the broken line deviated from the solid line in FIG. The forklift 1 may turn.

  The steering arm 31 according to the present embodiment uses the turning driving force transmitted to the turning shaft portion 33 (and consequently the rear wheels 14L and 14R) by the expansion and contraction of the piston rod 27 based on the rotational difference between the front wheels 13L and 13R. By partially absorbing the propulsion force applied by the vehicle body 2 in the direction propelled by the forklift 1, the turning direction of the forklift 1 is autonomously adjusted from the direction indicated by the broken line in FIG. 4B to the direction indicated by the solid line. Is.

  In other words, the steering arm 31 of the present embodiment uses the propulsive force generated when the forklift 1 propels due to the rotational difference between the front wheels 13L and 13R, and determines the turning center of the rear wheels 14L and 14R determined by the expansion and contraction of the piston rod 27. It has an elastic force that absorbs an error with respect to the center P. As a result, the steering arm 31 of the present embodiment is configured so that the turning of the rear wheels 14L and 14R is such that the turning center of the rear wheels 14L and 14R turning by the steering mechanism 20 is located on the rotation axis of the front wheels 13L and 13R. It is configured to adjust the corners.

  Note that the steering arm 31 of the present embodiment can obtain the elastic force necessary to absorb the error by changing the thickness of the spring and the like. It is manufactured after the thickness and the like are set in advance.

[effect]
As described above, in the forklift 1 of the present embodiment, the turning center of the rear wheels 14L and 14R is not deviated from the rotation axis of the front wheel 13, so that the slipping of the wheels 13 and 14 during turning can be suppressed. The amount of tire wear can be reduced, and the operability by the operator can be improved.

Further, in the forklift 1, since a rotation difference is generated between the front wheels 13L and 14R during turning, the turning radius of the forklift 1 can be further reduced.
Further, in the forklift 1, the turning direction of the forklift 1 by the rear wheels 14L and 14R passively matches the turning direction of the forklift 1 by the front wheels 13L and 14R by the elastic force of the steering arm 31, so that the forklift 1 is actively matched. Therefore, it is possible to reduce the cost because the necessary components can be omitted.

[Correspondence with Invention]
In the present embodiment, the steering arm 31 corresponds to an example of an elastic member and a turning angle adjusting unit, and the control unit 30 that performs drive control processing corresponds to an example of a rotation difference setting unit.

[Modification]
In the present embodiment, the configuration in which the steering arm 31 is made of a leaf spring has been exemplified. However, the present invention is not limited to this, and the steering arm 31 may be made up of a coiled spring, a synthetic rubber, or the like. Good. Such an elastic member may form a tie rod 29, for example, instead of the steering arm 31. Furthermore, such an elastic member may be provided as a separate component from the steering arm 31 and the tie rod 29 in the link portion 28.

  Further, in this embodiment, the steering arm 31 as such an elastic member makes the turning center of the rear wheel 14 coincide with the turning center P based on the rotation difference of the front wheel 13 by the elastic force (rear wheel 14 The example of matching the turning center of the rear wheel 14 with the rotation axis of the front wheel 13 has been described. However, the turning center of the rear wheel 14 does not necessarily coincide with the turning center P. If the configuration is such that the turning center of 14 approaches (the turning center of the rear wheel 14 approaches the rotational axis of the front wheel 13), as described above, it is possible to suppress the slipping of the wheels 13 and 14 during the turning. . Thereby, the amount of wear of the tire can be reduced, and the operability by the operator can be improved.

[Second Embodiment]
Next, a forklift 1 as an industrial vehicle according to a second embodiment to which the present invention is applied will be described with reference to the drawings. Since the forklift 1 of this embodiment has many parts in common with the first embodiment, description of these common parts will be omitted as much as possible, and different parts will be mainly described.

  As shown in FIG. 5A, the steering mechanism 20 of the forklift 1 of the present embodiment turns the left steering mechanism 20L for turning the left rear wheel 14L and the right rear wheel 14R according to a command from the control unit 30. And a right steering mechanism 20R.

  The left steering mechanism 20L and the right steering mechanism 20R have hydraulic steering cylinders 25L and 25R that perform expansion and contraction operations in the vehicle width direction, as shown in FIG. 5B, according to the operation direction and operation amount of the steering wheel 16, respectively. Each has. The steering cylinder 25L is provided with a piston rod 27L, and the steering cylinder 25R is provided with a piston rod 27R.

  The steering cylinder 25L extends and contracts the piston rod 27L, thereby turning the rear wheel 14L attached to the link portion 28 about the vertical axis, and the steering cylinder 25R extends and contracts the piston rod 27R. By doing so, the rear wheel 14R attached to the link portion 28 is turned about the vertical axis.

That is, the steering mechanism 20 of the present embodiment includes two steering mechanisms 20L and 20R that individually drive the left rear wheel 14L and the right rear wheel 14R to turn.
The control unit 30 of the forklift 1 according to the present embodiment inputs the operation amount of the accelerator 18, the operation direction and the operation amount of the steering 16, performs the above-described drive control process, and sets the front wheel 13L set by this process. , 13R is performed so that the turning angles of the left rear wheel 14L and the right rear wheel 14R are individually set so that the turning center of the rear wheel 14 coincides with the turning center P of the rear wheel 14R.

  In the turning angle setting process, a command for rotating the left rear wheel 14L and the right rear wheel 14R at the set turning angles is output to the left steering mechanism 20L and the right steering mechanism 20R. Thus, when the rear wheel 14 is turning, the left rear wheel 14L and the right rear wheel 14R are individually driven to turn by the left steering mechanism 20L and the right steering mechanism 20R, so that the turning center of the rear wheels 14L and 14R becomes the front wheel. It is set to the turning center P of 13L and 13R.

[effect]
As described above, in the forklift 1 of the present embodiment, the turning angles of the rear wheels 14L and 14R are individually controlled by the two steering mechanisms 20L and 20R, so that the turning center of the rear wheels 14L and 14R is accurately controlled at the front wheel 13L. , 13R can coincide with the turning center P, and as a result, slipping of the wheels 13, 14 during turning can be further suppressed.

[Modification]
In the present embodiment, on the assumption that the front wheels 13L and 13R have the turning center P by the drive control process, the turning centers of the rear wheels 14L and 14R are made to coincide with the turning center P of the front wheels 13L and 13R by the turning angle setting process. However, the present invention is not limited to this.

  Specifically, in the turning angle setting process, the operation direction and the operation amount of the steering wheel 16 are input, and at least the turning center of the rear wheels 14L and 14R is positioned on the rotation axis of the front wheels 13L and 13R. 14L and the right rear wheel 14R are set individually for each turning angle, and commands for rotating the left rear wheel 14L and the right rear wheel 14R at the set turning angles are sent to the left steering mechanism 20L and the right steering mechanism 20R. It may be output. In this case, a configuration for causing a rotation difference between the front wheels 13L and 13R can be eliminated.

  Further, in the present embodiment, the left steering mechanism 20L and the right steering mechanism 20R are exemplified as having the hydraulic steering cylinders 25L and 25R, respectively, but the present invention is not limited to this.

  For example, the left steering mechanism 20L and the right steering mechanism 20R may each include an electric motor that turns the left rear wheel 14L and the right rear wheel 14R, as shown in FIG. In this case, for example, it is possible to adopt a configuration in which each electric motor is fitted coaxially with each turning shaft portion 33 and the rear wheels 14L and 14R are rotated about the same axis via a turning type wheel bracket.

[Other Embodiments]
As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, In the range which does not deviate from the summary of this invention, it is possible to implement in various aspects.

  In the first embodiment, the elastic member as the turning angle adjusting means is provided in the link portion 28 connected to the piston rod 27 of the steering mechanism 20, and in the second embodiment, the left steering mechanism 20L as the turning angle adjusting means. Although the right steering mechanism 20R and the right steering mechanism are configured, the present invention is not limited to these.

  For example, in a configuration in which the number of steering mechanisms 20 is one, an actuator for adjusting the turning driving force transmitted to the turning shaft portion 33 (and thus the rear wheels 14L and 14R) by the expansion and contraction operation of the piston rod 27 is a link portion. 28, the control unit 30 may perform a correction control for driving the actuator so that the respective turning angles are set by the turning angle setting process.

  In the first embodiment and the second embodiment, the pair of left and right front wheels 13 are driving wheels and the pair of left and right rear wheels 14 are steering wheels. However, the present invention is not limited to this. A configuration in which the pair of rear wheels 14 are drive wheels and the pair of left and right front wheels 13 may be steering wheels.

  In the first and second embodiments, the counterbalance forklift 1 is exemplified as an industrial vehicle. However, the present invention is not limited to this, and the configuration of the above embodiment includes a pair of left and right steering wheels and a drive. It can be applied to all industrial vehicles that run on four-wheeled wheels.

  DESCRIPTION OF SYMBOLS 1 ... Forklift, 2 ... Vehicle main body, 3 ... Cargo handling part, 7 ... Inner mast, 8 ... Outer mast, 9 ... Lift cylinder, 11 ... Fork, 13 ... Front wheel, 14 ... Rear wheel, 15 ... Driver's seat, 16 ... Steering, 17 ... Lever, 18 ... Accelerator, 20 ... Steering mechanism, 21L ... Left drive mechanism, 21R ... Right drive mechanism, 25 ... Steering cylinder, 27 ... Piston rod, 28 ... Link part, 29 ... Tie rod, 30 ... Control part, 31 ... Steering arm, 33, turning shaft, 35a, 35b, connecting pin, 37, hub, 39, axle beam.

Claims (9)

An industrial vehicle that runs on four wheels consisting of a pair of left and right steering wheels and drive wheels,
A steering mechanism for turning the pair of steered wheels according to the steering operation direction and operation amount of the operator;
Turning angle adjusting means for adjusting turning angles of the left steering wheel and the right steering wheel so that the turning center of the steering wheel turning by the steering mechanism approaches the rotation axis of the pair of drive wheels;
An industrial vehicle comprising: A drive mechanism for rotating the pair of drive wheels according to an accelerator operation amount of an operator;
A rotation difference setting means for setting a rotation difference between the left drive wheel and the right drive wheel rotated by the drive mechanism in accordance with the steering operation direction and the operation amount;
The turning angle adjusting means adjusts each turning angle so that the turning center of the steering wheel approaches the turning center of the driving wheel based on the rotation difference set by the rotation difference setting means. The industrial vehicle according to claim 1. The steering mechanism is disposed between the left steering wheel and the right steering wheel, and has a piston rod that extends and contracts in the vehicle width direction by a movement amount corresponding to the steering operation direction and the operation amount. Composed of cylinders,
The industrial vehicle according to claim 1 or 2, wherein the turning angle adjusting means is provided in a link portion that connects both ends of the piston rod and the pair of steering wheels.   The turning angle adjusting means autonomously adjusts each turning angle of the left steering wheel and the right steering wheel by a propulsive force applied in a direction propelled by the industrial vehicle based on a rotation difference of the driving wheel. The industrial vehicle according to claim 3, comprising an elastic member.   The industrial vehicle according to claim 4, wherein the elastic member is a plate-like or coil-like spring. The link portion includes a tie rod connected to both ends of the piston rod, and a steering arm that connects the end portion of the tie rod and the respective steered wheels, respectively.
The industrial vehicle according to any one of claims 3 to 5, wherein the elastic member is formed as the tie rod or the steering arm. Depending on the steering operation direction and the operation amount, the steering wheel on the left side and the steering wheel on the right side of the steering wheel that is turned by the steering mechanism are positioned on the rotation axis of the pair of drive wheels. A turning angle setting means for setting each turning angle;
The turning angle adjusting means is an auxiliary actuator for individually adjusting the turning angles of the left steering wheel and the right steering wheel so that the turning angles are set by the turning angle setting means. The industrial vehicle according to claim 3, wherein: Depending on the steering operation direction and the operation amount, the steering wheel on the left side and the steering wheel on the right side of the steering wheel that is turned by the steering mechanism are positioned on the rotation axis of the pair of drive wheels. A turning angle setting means for setting each turning angle;
The steering mechanism includes a left steering mechanism and a right steering mechanism that individually turn the left steering wheel and the right steering wheel, respectively.
The left steering mechanism and the right steering mechanism each turn on the left steered wheel and the right steered wheel so as to have the respective turning angles set by the turning angle setting means as the turning angle adjusting means. The industrial vehicle according to claim 1 or 2, wherein each of the corners is adjusted.   The industrial vehicle according to claim 8, wherein the left steering mechanism and the right steering mechanism include an electric motor or a hydraulic cylinder respectively provided for the left steering wheel and the right steering wheel.

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