JPH0930790A - Suspension system of reach type forklift truck - Google Patents

Abstract

PROBLEM TO BE SOLVED: To curtail assembling operation steps as well as to reduce production cost by retrenching the number of part items of a mechanism supporting a caster. SOLUTION: A driving tire and a caster 6 are suspended separately, and a caster link 13 being shiftable within the regulating range in an interval between both the grounding and counter-grounding directions of this caster 6 is installed there. A compression coil spring 15 capable of pressing the caster to the road surface is installed in the caster link 6. A dog 27 being displaced according to an amount of travel of a mast is pressably installed in this compression coil spring 15. According to this constitution, if the mast is shifted to the rear of a car body, the coil spring 15 is forcibly pressed by the dog 27, and thereby the caster 6 is pressed toward the grounding direction via the caster link 13. Therefore, the caster 6 is forcibly pressed and driven in a simple structure without using any expensive actuators, sensors and suchlike.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reach type forklift having a drive wheel and an auxiliary wheel, and more particularly to a suspension device for supporting the auxiliary wheel with respect to a vehicle body.

[0002]

2. Description of the Related Art Conventionally, as a suspension device of this type, for example, one shown in FIG. 9 has been proposed. That is, the drive tire 52 is rotatably attached to the lower portion of the vehicle body frame 50 via the gear box 51. An upper link 53 is rotatably supported by a shaft 54 at a lower portion of the vehicle body frame 50, and a left end of the upper link 53 is rotatably supported by the gear box 51 via a shaft 55. The upper portion of the interlocking link 56 is rotatably supported by the shaft 55, and the interlocking link 56 and the upper link 53 are relatively rotatable. A mounting member 57 is provided on the vehicle body frame 50 above the interlocking link 56, and a suspension spring 59 is interposed between the two members 56, 57.

A lower link 60 is rotatably supported by a shaft 58 below the vehicle body frame 50, and a predetermined clearance is provided between the lower link 60 and the floor 50a of the vehicle body frame 50. . The left end of the lower link 60 is rotatably connected to the lower end of the interlocking link 56 by a shaft 61, and the lower link 60 is centered around the shaft 61.
And the interlocking link 56 are relatively rotatable. A swing link 62 is rotatably supported on the shaft 58, and a caster spring 63 is interposed between the swing link 62 and a support plate 60a fixed to the right end of the lower link 60. A caster 64 for stabilizing the posture of the driving tire 52 is rotatably attached to the lower surface of the swing link 62.

When the mast (not shown) moves to the front of the vehicle body 65 and the center of gravity of the vehicle body 65 moves to the front, the load on the rear axle of the machine base decreases, and the springs 59 and 63 raise the vehicle body frame 50. Then, both shafts 54 and 58 also rise. Then, the upper link 53 is rotated counterclockwise about the shaft 54, and the lower link 60 is rotated counterclockwise about the shaft 58 via the interlocking link 56. By this operation, as the load on the rear axle decreases, the load is reduced almost equally from the drive tire 52 and the caster 64 having different load distribution rates. Therefore, the load distribution ratio between the drive tire 52 and the casters 64 changes, and almost all of the rear axle load is distributed to the drive tire 52. As a result, slippage of the driving tire 52 is prevented.

On the contrary, when the mast moves to the rear of the vehicle body and the center of gravity of the vehicle body 65 moves to the rear, the vehicle body frame 50 is lowered, and the upper body is moved in the opposite direction to that when the center of gravity of the vehicle body 65 moves to the front. The link 53 and the lower link 60 are rotated. By this operation, the drive tire 52 is slightly lifted upward and the casters 64 are pressed against the road surface, so that an increase in wheel pressure applied to the drive tire 52 is prevented. As a result, an excessive change in the wheel pressure of the drive tire 52 with respect to the road surface is prevented.

Further, the vehicle body frame 5 is caused by a sudden turn of the vehicle body.
When an excessive lateral force acts in the right direction (direction of arrow A) with respect to 0, the body frame 50 tilts to the right due to centrifugal force. Then, the upper link 53 is rotated counterclockwise about the shaft 54, and the lower link 6 is moved via the interlocking link 56.
0 and the support plate 60a are rotated counterclockwise about the shaft 58. Then, the right side of the shaft 58 of the lower link 60 comes into contact with the floor 50a, whereby the rotation of the lower link 60 is restricted, and then the caster 64 is attached to the road surface.
Is flexibly pressed against the elastic force of the caster spring 63.

On the other hand, when an excessive lateral force acts on the body frame 50 in the left direction (direction of arrow B), the swing link 62, the lower link 60, and the lower link 60 move in the opposite direction to the case where the lateral force acts from the direction of arrow A. The upper link 53 is rotated, and the drive tire 52 is flexibly pressed against the road surface against the elastic force of the suspension spring 59. At this time, the left side of the shaft 58 of the lower link 60 is brought into contact with the floor 50a of the vehicle body frame 50, and rotation of the lower link 60 is restricted.

[0008]

However, the former suspension shown in the prior art requires many links such as the upper link 53, the interlocking link 56, and the lower link 60. As a result, the entire suspension system becomes large in size, the mounting space for the suspension system must be widened, and the number of parts is increased to increase the manufacturing cost.

Further, to the right of the body frame 50 (see FIG.
When an excessive lateral force is exerted in the direction of arrow A shown in Fig. 5, there is a clearance between the floor 50a of the vehicle body frame 50 and the lower link 60, so that the lower link 60 contacts the floor 50a of the vehicle body frame 50. Until the contact is made, the caster 64 does not generate a reaction force due to the elastic force of the caster spring 63. Therefore, there is a problem that the body frame 50 suddenly inclines due to the clearance.
Note that when an excessive lateral force acts on the vehicle body frame 50 in the left direction, the reaction force due to the suspension spring 59 is immediately generated, so there is no such problem. Of course, if the caster spring 63 is independently fixed to the vehicle body 65 in the same manner as the suspension spring 63, the abrupt inclination described above is eliminated. However, with that alone, the above-described action of the links 56, 60 and the like cannot be obtained, and the drive tire 52 is likely to slip when the mast moves forward.

Therefore, the links 56 and 60 are eliminated and the casters 64 are made independent, and at the same time, the longitudinal movement of the mast is detected by a sensor, and the casters 6 are forcibly forced by an actuator.
Driving 4 up and down solves both of the above problems. However, according to this method, an actuator, a sensor, and the like are newly required, an installation space is required, and there is a problem that cost is increased. Also, casters 6
There is a method of deleting 4 but driving tire 5
The load of 2 increases and an expensive tire must be used, which leads to an increase in cost.

The present invention has been made to solve the above problems. A first object of the present invention is to reduce the number of parts of a mechanism for supporting auxiliary wheels to a vehicle body and reduce the assembly work steps. It is to reduce the manufacturing cost.

A second object is to allow the spring to directly receive the reaction force due to the inclination of the vehicle body frame even if the vehicle body is inclined, and to alleviate the behavior when the vehicle body is inclined. Needless to say, in any case, it is necessary to inexpensively and easily perform slip prevention at the time of reach-out.

[0013]

According to a first aspect of the present invention, a mast that is movable in the front-rear direction of a vehicle body, drive wheels and auxiliary wheels for stabilizing the attitude of the vehicle body are provided at lower portions on both sides of the vehicle body frame. In a reach type forklift equipped with the drive wheel and the auxiliary wheel, the suspension is independently suspended, and the displacement when the mast is moved in the rearward direction is converted into a pressing drive force of the auxiliary wheel in the ground contact direction to perform a pressing drive. The gist is to have a pressing means for According to this configuration, when the mast moves to the rear of the vehicle body, the displacement thereof is converted into the pressing driving force, and the auxiliary wheels are pressed and driven in the ground contact direction.

The invention according to claim 2 is characterized in that the pressing means has means for releasing the pressing drive of the auxiliary wheel in the ground contact direction when the mast moves in the front direction. To do. According to this structure, when the mast moves in the front direction, the pressing drive of the auxiliary wheel in the ground contact direction is released.

A third aspect of the invention is characterized in that the pressing means has an elastic member that resists the pressing of the auxiliary wheel in the anti-grounding direction. When the auxiliary wheel is pressed in the anti-grounding direction, the elastic member resists the pressing force.

According to a fourth aspect of the present invention, the pressing means is provided on the vehicle body such that the moving member is movable in conjunction with the mast and the auxiliary wheel is movable within a certain range between the ground contact direction and the anti-ground contact direction. And a conversion drive mechanism that converts the displacement of the moving member into a driving force of the supporting member that pushes the auxiliary wheel toward the ground when the mast moves in the rearward direction and drives the conversion driving mechanism. What is being done is the summary. According to this configuration, when the mast moves in the front direction, the moving member moves in conjunction with the mast, and the displacement is converted into a driving force that presses the auxiliary wheel in the ground contact direction to drive the support member. .

The invention according to claim 5 is characterized in that the pressing means has means for varying the pressing drive force of the auxiliary wheel in the ground contact direction according to the amount of displacement of the mast. Is. According to this configuration, the pressing driving force of the auxiliary wheel in the ground contact direction changes according to the displacement amount of the mast.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a three-wheel reach type forklift 1, which has a reach leg 3 extending forward from the lower side of a vehicle body 2 and a mast 4 moving back and forth along the reach leg 3. Further, a drive tire 5 as a drive wheel and a caster 6 as an auxiliary wheel are provided in the lower rear part of the vehicle body 2 so as to face each other, and a pair of driven tires 7 are provided in the lower front part so as to face each other.

As shown in FIG. 2, the driving tire 5 and the casters 6 are independently suspended. The driving tire 5 is installed on the vehicle body frame 8 via an elastic member so as to be vertically movable. In this embodiment, rubber cushions (four in this embodiment) 9 are provided on the mounting portion of the vehicle body frame 8, and the rubber cushion 9 has a drive unit 10
The drive tire 5 is attached via the. The rubber cushion 9 is not limited as long as it has an elastic function, and may be another member.

The caster 6 side is also mounted on the vehicle body frame 8 via an elastic body so as to be vertically movable. In the present embodiment, as shown in FIGS. 3 and 4, a support portion 11 is provided on the inner side surface of the vehicle body frame 8, and a caster link 13 as a support member is provided on the support portion 11 via a fixed shaft 12. Has been. The caster 6 is fixed to the rear end of the caster link 13 via a caster unit 14.
The caster link 13 has the fixed shaft 12 within a range described later between the grounding direction and the anti-grounding direction of the caster 6.
It is possible to rotate around. In addition, casters 6
The ground contact direction means a direction in which the caster 6 is pressed against the road surface by the elastic force of the compression coil spring 15 as an elastic member described later, and the anti-ground direction of the caster 6 is a direction in which the caster 6 is pressed against the road surface. Means the opposite direction.

A contact portion 13a is provided at the center of the caster link 13 so as to project downward. The contact portion 13a can contact the inner surface of the vehicle body frame 8. or,
A front support laterally U-shaped support 16 is fixed to the vehicle body frame 8 in front of the caster link 13 by welding, and a stopper bolt 17 is screwed onto the rear end upper surface of the support 16. The upper surface of the caster link 13 can come into contact with the lower end of the stopper bolt 17.

That is, the rotation range of the caster link 13 is restricted by the stopper bolt 17 and the contact portion 13a. In other words, the rotation range of the caster 6 in the ground contact direction and the anti-ground contact direction is set. The screwing of the stopper bolt 17 is adjustable and can be changed to a suitable range each time.

As shown in FIGS. 3 to 5, a connecting rod 19 is connected to the front end of the caster link 13 by a pin 20 so as to be relatively rotatable. A moving body 21 having a U-shape on the front is loosely inserted in the connecting rod 19. Also, the connecting rod 1
A support plate 22 is inserted into the upper end of the member 9, and a double nut 24 is screwed through a spring washer 23. This support plate 2
A compression coil spring 15 is interposed between the moving body 21 and the moving body 21 in the vertical direction of the vehicle body. The elastic force of the compression coil spring 15 can be adjusted by adjusting the screwing position of the double nut 24.

Rollers 26 are rotatably provided on both outer side surfaces of the moving body 21 via shafts 25. In front of each roller 26, a dog 27 as a moving member capable of interlocking with the mast 4 is arranged oppositely. The movement amount of the dog 27 is displaced according to the movement amount of the mast 4. Of course, an offset that does not move within a certain range even if the mast 4 moves may be provided. In addition,
The compression coil spring 15, the support body 16, the connecting rod 19, the moving body 21, the support plate 22, and the roller 26 constitute a conversion drive mechanism. The caster link 13, the compression coil spring 15, the support 16, the connecting rod 19, the moving body 21, the support plate 22, the roller 26, the dog 27, and the like constitute a pressing mechanism.

An inclined surface 27a is formed at the tip of the dog 27 so as to be thicker toward the front side of the vehicle body 2. Then, as the dog 27 moves rearward, the dog 27
The outer peripheral surface of the roller 26 is pressed against the elastic surface of the compression coil spring 15 by the inclined surface 27a. The position of the dog 27 shown in FIG. 3 shows the mast 4 located at the foremost end.

The inclined surface 27a has a function of easily contacting the outer peripheral surface of the roller 26 without being caught, and the pressure contact force of the roller 26 can be changed according to the moving amount of the dog 27. Of course, it is also possible to adjust the variation state of the pressure contact force of the roller 26 by adjusting the inclination state of the inclined surface 27a.

Next, the operation and effect of the suspension system of the reach type forklift configured as described above will be described. When the dog 27 moves rearward as the mast 4 moves rearward, the inclined surface 27 a of the dog 27 is pressed against the roller 26. Then, the moving body 21 is moved upward, and the support plate 22 is also moved upward against the elastic force of the compression coil spring 15. Then, the caster link 13 shown in FIG. 3 is slightly rotated counterclockwise around the fixed shaft 12 and is pressed and driven in the ground contact direction. That is, the caster 6 is pressed against the road surface by the elastic force of the compression coil spring 15. As a result, when the center of gravity of the vehicle body 2 moves rearward, the increase in the wheel pressure applied to the drive tire 5 is reduced by the wheel pressure applied to the casters 6.

On the contrary, the dog 27 is moved along with the forward movement of the mast 4.
3 moves forward, the caster link 13 shown in FIG.
The wheel pressure of the caster 6 is released by rotating the caster 6 slightly in the clockwise direction with respect to. As a result, when the center of gravity of the vehicle body 2 moves forward, the wheel pressure applied to the drive tire 5 takes almost all of the rear axle load, and slip is prevented.

When an excessive lateral force acts on the vehicle body 2 due to a sudden turn and the vehicle body 2 shown in FIG. 2 leans to the left, a reaction force based on the elastic force of the rubber cushion 9 is generated. On the contrary, car body 2
When is tilted to the right, a reaction force based on the elastic force of the compression coil spring 15 is generated. The compression coil spring 15 is the body frame 8
However, since the lower end thereof is in contact with the support 16 via the moving body 21, there is no clearance as in the prior art. Therefore, the vehicle body 2 does not tilt rapidly but tilts gradually.

As described above, in the present embodiment, the drive tire 5 and the casters 6 are independently suspended,
A caster link 13 that can move between the grounding direction and the anti-grounding direction of the caster 6 within a regulation range is provided, and the caster link 13 is provided with a compression coil spring 15 that can press the caster 6 against the road surface. Therefore, the link connecting the drive tire 5 and the caster 6 can be omitted, so that the suspension device can be downsized, the mounting space of the suspension device can be narrowed, and the number of parts can be reduced to reduce the cost.

At the same time, since the caster link 13 is pressed against the road surface in conjunction with the rearward movement of the mast 4, the increase in the wheel pressure applied to the drive tire 5 against the road surface can be reduced by the wheel pressure applied to the casters 6. Therefore, since it is not necessary to use the expensive driving tire 5, it is possible to avoid an increase in manufacturing cost.

Further, the dog 27 is made movable in conjunction with the mast 4, and the dog 27 is provided with an inclined surface 27a. Therefore, the load on the drive tire 5 can be reduced and the life of the drive tire 5 can be extended.

Further, since the driving tire 5 and the casters 6 are independently suspended and the connecting rod 19 is provided with the double nut 24, the wheel pressure of the casters 6 with respect to the road surface can be arbitrarily adjusted according to the specifications of the forklift. Moreover, the wheel pressure of the casters 6 can be arbitrarily adjusted independently of the drive tires 5.

Further, since the caster link 13 is formed with the contact portion 13a capable of contacting the vehicle body frame 8, when the caster link 13 is rotated by a predetermined amount or more in the wheel pressure released state, the contact portion 13a is formed. The body frame 8 is contacted. Therefore, excessive rotation of the caster link 13 can be prevented. Further, since the stopper bolt 17 is screwed onto the rear end upper surface of the support body 16 in front of the caster link 13, when the caster link 13 rotates more than a predetermined amount in the wheel pressure applied state, the upper surface of the caster link 13 stops. The bolt 17 is brought into contact with the lower end of the bolt 17. Therefore, excessive rotation of the caster link 13 can be prevented.

Furthermore, since the caster 6 is pressed in the grounding direction by a simple mechanism that utilizes the displacement of the mast 4 without using an actuator or the like, the cost is extremely low and the size can be reduced. it can.

The respective configurations are not limited to the embodiments, and may be replaced with others without departing from the spirit of the invention. (1) In the above-described embodiment, the caster 6 is pressed against the road surface by bringing the inclined surface 27a formed on the dog 27 into contact with the roller 26, but the support 16, the moving body 21, the roller 26, etc. It is also possible to omit the parts and press the caster 6 on the road surface. That is, FIG.
As shown in (a) to (c), the caster link 13a is formed in an L shape, and its bent portion is rotatably supported by the fixed shaft 12 with respect to the vehicle body frame 8. A connecting rod 19 is loosely inserted in the vehicle body frame 8, and its tip is rotatably connected to the upper end of the caster link 13a by a pin 20. Connecting rod 1
A pressing plate 28 is movably inserted in the shaft 9 along the axial direction of the connecting rod 19, and a compression coil spring 15 is interposed between the pressing plate 28 and the support plate 22. Further, a pair of through holes 29 are formed in the body frame 8 corresponding to the vicinity of both ends of the pressing plate 28.

With the above arrangement, when the mast 4 moves rearward, the tip of the dog 27 presses the pressing plate 28 through the through hole 29. Then, the compression coil spring 15 is compressed, and the caster 6 is pressed against the road surface by its elastic force. Therefore, the support 16 shown in the above embodiment,
Since parts such as the moving body 21 and the roller 26 can be omitted, the structure of the suspension device can be further simplified, and the manufacturing cost can be further reduced.

(2) In the above-described embodiment, the casters 6 are pressed against the road surface by using the pair of compression coil springs 15. However, the number of the compression coil springs 15 is reduced and the support 16 is omitted so that the casters 6 can be cast on the road surface. It is also possible to hold down 6. That is, as shown in FIGS. 7A to 7C, the front end of the caster link 13 b is rotatably supported by the fixed shaft 12 with respect to the vehicle body frame 8. The tip of a connecting rod 19 fixed to the vehicle body frame 8 is loosely inserted into the center of the caster link 13b. Further, the moving body 21 is inserted into the base end of the connecting rod 19 so as to be movable along the axial direction of the connecting rod 19, and one compression coil spring 15 is interposed between the moving body 21 and the caster link 13b. .

With the above construction, when the mast 4 moves rearward, the inclined surface 27a of the dog 27 causes the compression coil spring 1 to move.
The roller 26 is pressed against the elastic force of 5. Then, the compression coil spring 15 is compressed, and the caster 6 is pressed against the road surface by its elastic force. Therefore, the number of the compression coil springs 15 shown in the above-described embodiment can be reduced by one, and parts such as the support 16 can be omitted, so that the structure of the suspension device can be further simplified and the manufacturing cost can be further improved. It can be reduced. In addition, the front and rear direction of the caster link 13b (see FIG.
Since the length in (a) 's left-right direction) can be shortened, the suspension device can be made compact and its mounting space can be further narrowed.

(3) Although the compression coil spring 15 is used in the above embodiment, an elastic body such as a leaf spring or a rubber cushion may be used instead. (4) In the above embodiment, the contact portion 13a capable of contacting the vehicle body frame 8 is formed in the lower center of the caster link 13, but the caster link 1 facing the contact portion 13a is formed.
An abutting portion 13 capable of abutting on the body frame 8 at the upper center of
a may be provided. With this configuration, it is possible to prevent the caster link 13 from rotating more than a predetermined amount in the wheel pressure applied state. At the same time, since the stopper bolt 17 can be omitted, the manufacturing cost of the suspension device can be reduced.

(5) The operation of the caster link does not necessarily have to be rotatable but may be vertically slidable. (6) Other than the embodiment described above, the configuration shown in FIG. 8 may be used. That is, the cam 30 and the lever 31 are provided on the vehicle body frame 8 such that the cam 30 is located on the front side of the vehicle body and can rotate integrally with each other at a constant angle.
A roller 26 is rotatably provided at the tip of 1. The caster link 13c is rotatably provided on the vehicle body frame 8 about the shaft 32. A bolt 33 is screwed vertically on the vehicle body front side end of the caster link 13c, and a caster 6 is rotatably provided on the vehicle body rear side end through a rubber 34 in a horizontal plane and a vertical plane. When the mast 4 moves backward,
The roller 31 contacts the roller 26, and the lever 31 and the cam 30 rotate integrally. Then, the cam 30 abuts against the lower end of the bolt 33 and is pressed, and the caster link 13c is rotated clockwise. As a result, the casters 6 are pressed toward the ground, and the wheel load increases. Further, the cam 30 and the lever 31 are urged counterclockwise by a spring (not shown) or the like, and when the mast 4 and the dog 27 move forward, the cam 30 and the lever 31 rotate counterclockwise and the cam 30 The pressing of the caster 6 on the bolt 33 is released, and the pressing of the caster 6 in the ground contact direction is also released. With this configuration, the floor can be made even lower.

[0042]

According to the invention described in claim 1, it is possible to easily drive the auxiliary wheels without adding a new expensive actuator or the like, and at the same time, it is possible to save space and reduce cost. It is possible to reduce the friction of the drive wheels at the time of reach-in. Moreover, since the auxiliary wheels are suspended independently of the drive wheels, the behavior of the leaning of the vehicle body does not become abrupt even if the vehicle body leans.

According to the invention described in claim 2, according to claim 1
In addition to the effects of the invention described in (1), since the pressing drive of the auxiliary wheel is released at the time of reach-out, the wheel weight of the drive wheel increases,
Slip can be prevented.

According to the invention of claim 3, claim 1
Alternatively, in addition to the effect of the invention described in claim 2, even when the vehicle body is tilted, the reaction force of the elastic member can slow and stabilize the tilting behavior of the vehicle body.

According to the fourth aspect of the present invention, the first aspect is provided.
In addition to the effects of the invention described in any one of claims 3 to 3,
With an extremely simple mechanism, the wheel weight of the drive wheel can be increased at the time of reach-out, and the wheel weight of the drive wheel can be reduced at the time of reach-in. It is possible to prevent slipping at the time.

According to the invention of claim 5, claim 1
In addition to the effects of the invention described in any one of claims 4 to 4,
According to the amount of displacement of the mast, the optimum wheel weight of the drive wheel at that time can be obtained.

[Brief description of drawings]

FIG. 1 is a side view of a forklift showing an embodiment of the present invention.

FIG. 2 is a back sectional view showing the rear of the forklift.

FIG. 3 is a rear side view showing the inside of the forklift in the same manner.

FIG. 4 is a sectional view taken along line XX of FIG. 3;

FIG. 5 is a front view of essential parts showing a state where the casters are pressed.

FIG. 6 shows a suspension device according to another embodiment (a) is a side view, (b) is a front view, and (c) is a plan view.

7A and 7B show a suspension device according to another embodiment, FIG. 7A is a side view, FIG. 7B is a front view, and FIG. 7C is a side view showing a state in which the casters are released.

FIG. 8 is a side view of the suspension device according to another embodiment.

FIG. 9 is a back cross-sectional view of a forklift truck showing a conventional technique.

[Explanation of symbols]

2 ... vehicle body, 4 ... mast, 5 ... driving tire (driving wheel), 6
... casters (auxiliary wheels), 8 ... vehicle body frame, 13 ... caster links (supporting members), 15 ... compression coil springs (elastic members), 27 ... dogs (moving members).

Claims (5)

[Claims] 1. A reach-type forklift having a mast that is movable in the front-rear direction of a vehicle body, and drive wheels and auxiliary wheels for stabilizing the posture of the vehicle body on both lower sides of a vehicle body frame, wherein the drive wheel and the auxiliary wheel are provided. Suspension of a reach type forklift having a pressing means for independently driving the auxiliary wheel and converting the displacement when the mast is moved in the rearward direction into a pressing driving force in the ground contact direction of the auxiliary wheel. apparatus. 2. The suspension of a reach-type forklift according to claim 1, wherein the pressing means has means for releasing the pressing drive of the auxiliary wheel in the ground contact direction when the mast moves in the front direction. apparatus. 3. The suspension device for a reach type forklift according to claim 1, wherein the pressing means has an elastic member that resists the pressing of the auxiliary wheel in the anti-grounding direction. 4. A pressing member is a moving member that can move in conjunction with a mast, a supporting member that supports the auxiliary wheel so that it can move within a certain range between a grounding direction and an anti-grounding direction, and a mast. 2. A conversion drive mechanism for converting and displacing the displacement of the moving member into a driving force of the support member that presses the auxiliary wheel in the ground contact direction when the rearward movement is performed. The suspension device for a reach type forklift according to claim 3. 5. The pressing means has means for changing the pressing drive force of the auxiliary wheel in the ground contact direction according to the amount of displacement of the mast. Reach forklift suspension system.