JP2553222B2 - Auxiliary wheel lifting device for three-wheel reach type forklift - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lifting device for auxiliary wheels arranged on both sides of drive wheels of a three-wheel reach type forklift.

2. Description of the Related Art Generally, a three-wheel reach type forklift truck, as shown in FIGS. 6 and 7, is provided with a straddle arm 17 which is disposed in front of the forklift body 10 and which guides an outer mount 21 which moves in the front-rear direction. At least one driven wheel 1a (1
b), and one drive wheel 3 disposed near the center line in the vehicle width direction behind the forklift body 10,
A load is supported by these three wheels (henceforth called a three-wheel type), and a pair of auxiliary wheels 5a and 5b are provided at both ends of the drive wheel 3 in the vehicle width direction.

The drive wheels 3 are pivotally supported by a support member 7 and steered by a steering mechanism 11 linked to a steering wheel 9. The auxiliary wheels 5a, 5b are rotatably supported by brackets 15a, 15b fixed to the lower surfaces of the strength members 13a, 13b on the vehicle body side.

Reference numeral 19 denotes a reach cylinder arranged in front of the forklift body 10, and a rod 19a of the reach cylinder 19 is provided.
The outer mout 21 is movable in the front-rear direction in accordance with the operation of.

Further, an inner mast 23, on which a fork 30 is supported, is slidably arranged on the inner surface of the outer mout 21. twenty five
a and 25b are lift cylinders.
The inner mast 23 is movable in the vertical direction along the outer mast 21 in accordance with the operations of a and 25b.

That is, the reach type forklift is an outer mount that moves in the front-rear direction while being guided by the straddle arm 17.
An inner mast 23, on which a fork 30 is supported, is mounted so as to be movable up and down with respect to 21, and has a characteristic that it is particularly suitable for cargo handling and transportation work in a narrow passage.

In such a three-wheel reach type forklift truck, since only one drive wheel 3 is arranged in the lower rear portion of the forklift body 10, the vehicle is stabilized in the vehicle width direction as the center of gravity moves when the inner mast 23 rises. In order to deal with this, the pair of auxiliary wheels 5a and 5b are provided at both ends of the drive wheel 3 in the vehicle width direction as described above, and the vehicle width when the inner mast 23 is lifted is increased. We are trying to ensure directional stability.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in such a conventional three-wheel reach type forklift truck, the pair of auxiliary wheels 5a, 5b are mounted on the vehicle body side member via the brackets 15a, 15b and the strength members 13a, 13b. Since it is fixedly mounted, there is a problem that the traveling of the vehicle may become unstable due to a change in the load applied to the drive wheels 3 depending on the loading state of the heavy object on the fork.

That is, as shown in FIG. 7, a minute clearance α is set in advance between the auxiliary wheels 5a, 5b and the ground surface E, and the load of the forklift main body 10 on the drive wheel 3 is normal during normal running. Although it is considered to be large,
Reduce the clearance α, that is, the auxiliary wheels 5a, 5b
If the ground clearance of the vehicle is lowered, the auxiliary wheels 5a and 5b frequently come into contact with the ground when the vehicle sharply turns or travels on an uneven road surface. There is Particularly, when the drive wheel 3 itself is worn, the auxiliary wheels 5a and 5b are always in contact with the ground, and there is a problem that a sufficient load cannot be secured for the drive wheel.

On the other hand, if the clearance α is increased, that is, the ground height of the auxiliary wheels 5a and 5b is increased, the inner mast 2
With the upward movement of the center of gravity when 3 rises, the stability in the vehicle width direction deteriorates, which causes a problem that the original function of the auxiliary wheels 5a and 5b cannot be fulfilled.

Further, when the outer mast 21 itself, which is a unique action of the reach type forklift, moves in the front-rear direction, the load applied to the drive wheel 3 decreases due to the center of gravity moving forward, so the drive wheel is started and stopped. Three
There is a problem in that the vehicle may slip and the start-up acceleration performance and braking performance are reduced accordingly.

Therefore, the present invention solves the problem of such a conventional three-wheel reach type forklift truck, and can secure the load applied to the drive wheels even if the center of gravity moves forward and move the center of gravity upward. It is also an object of the present invention to provide a device capable of ensuring stability in the vehicle width direction.

Means for Solving the Problems In order to achieve the above-mentioned object, the present invention is arranged in front of a forklift body, guides an outer mast that moves in the front-rear direction in accordance with the operation of a reach cylinder, and near the front end thereof, respectively. A straddle arm in which at least one driven wheel is disposed, one drive wheel disposed in the lower rear of the forklift body and near the center line in the vehicle width direction, and both end portions in the vehicle width direction of the drive wheel. A pair of auxiliary wheels, an inner mast that is slidably arranged on the inner surface of the outer mast and moves up and down according to the operation of the lift cylinder, and a fork supported by the inner mast. In the three-wheel reach type forklift, the first aspect of the present invention is that, according to claim 1, the pair of auxiliary wheels are linked to the operation of the reach cylinder and the lift cylinder. An auxiliary drive mechanism is provided in which the auxiliary wheel rises from the ground surface or presses against the ground surface.

Further, according to claim 2, the raising / lowering drive mechanism is provided with a control means for raising the pair of auxiliary wheels from the ground surface when the reach cylinder extends and the center of gravity of the vehicle body moves forward. According to a third aspect of the present invention, the lifting drive mechanism is provided with a control means for pressing the pair of auxiliary wheels against the ground surface when the lift cylinder extends and the center of gravity of the vehicle body moves upward.

According to this structure, the outer mast arranged in front of the forklift body normally moves in the front-rear direction with the straddle arm as a guide along with the operation of the reach cylinder, and the inner mast moves along the outer mout along with the operation of the lift cylinder. Although it moves in the vertical direction, when the reach cylinder extends and the center of gravity of the forklift moves forward in such an operation, the pair of auxiliary wheels are drive-controlled by the control means so as to rise from the ground surface. It Therefore, the load on the rear wheel side of the forklift body is all applied to one drive wheel, so that the load on the drive wheel increases, slippage of the drive wheel at the time of starting and stopping is prevented, and the starting acceleration and braking performance are improved. The effect of improving is obtained.

Further, when the lift cylinder extends and the center of gravity of the forklift body moves upward, the control means drives and controls the pair of auxiliary wheels so as to press-contact the ground surface.
Therefore, it is possible to prevent the posture of the forklift body from becoming unstable due to the upward movement of the center of gravity.

Embodiment Hereinafter, an embodiment of an auxiliary wheel lifting device for a three-wheel forklift according to the present invention will be described in detail by assigning the same reference numerals to the same components as those of the conventional configuration.

In the configuration shown in FIGS. 1 and 2, 10 is a forklift body, and in front of the forklift body 10, a straddle arm 17 and an outer mast 21 movable in the front-rear direction with the straddle arm 17 as a guide are provided. And 1 near the front end of the straddle arm 17, respectively.
Individual driven wheels 1a (1b) are arranged. Reference numeral 3 denotes a single drive wheel which is disposed in the lower rear portion of the forklift body 10 and in the vicinity of the center line in the vehicle width direction. A pair of auxiliary wheels 5a and 5b are provided at both ends of the drive wheel 3 in the vehicle width direction. It is equipped so that it can be lifted up and down from the ground surface E by the lifting drive mechanism 20.

The drive wheel 3 is pivotally supported by a support member 7 and steered by a steering mechanism 11 linked to a steering wheel 9.

On the other hand, 19 is a reach cylinder arranged in the straddle arm 17, and a rod 19a of the reach cylinder 19 is provided.
The outer mout 21 is movable in the front-rear direction in accordance with the operation of.

An inner mast 23, on which a fork 30 is supported, is slidably arranged on the inner surface of the outer mast 21.

Reference numerals 25a and 25b denote lift cylinders, and the inner mast 23 is vertically movable along the outer mout 21 in accordance with the operation of the lift cylinders 25a and 25b.

Since the mounting structure of the auxiliary wheels 5a and 5b is the same on the left and right, the mounting structure of the auxiliary wheel 5a will be described below with reference to FIG.

In the configuration of the lifting drive mechanism 20 shown as a whole, 13a, 13a
Reference numeral c is a strength member on the vehicle body side, and a bracket 15a is fixed to the lower surface of the strength member 13a. The center point P ₁ of the link 27, which is substantially L-shaped in side view, is pivotally attached to the bracket 15a. Has been done.

Also, a bracket 29 is fixed to the strength member 13c, one end 31a of the auxiliary wheel cylinder 31 is pivotally supported by the bracket 29, and a rod protruding from the auxiliary wheel cylinder 31.
The other end 31c of 31b is pivotally supported at a point P ₂ above the link 27.

The auxiliary wheel 5a is rotatably attached to a point located at the rear R side end of the link 27.

The auxiliary wheel cylinder 31 is divided into left and right liquid chambers by a piston 33, and a spring 35 is built in one liquid chamber, and the other liquid chamber is described in detail later. A supply / discharge port 37 for receiving the hydraulic pressure supplied from the hydraulic pressure source is provided.

Further, a first limit switch 41 is arranged at a proper position above the outer mout 21, and a second limit switch 43 is further arranged at a proper position in front of the straddle arm 17.

The first limit switch 41 makes “contact” when the projection 23a provided on the inner mast 23 comes into contact with the second limit switch 41, while
The limit switch 43 is fixed to the inner surface of the straddle arm 17, and is set so that the protrusion 21a provided on the outer mout 21 protrudes forward and becomes "contact" when the outer mout 21 moves.

An example of driving the auxiliary wheel lifting device for such a three-wheel reach type forklift will be described with reference to the schematic diagrams shown in FIGS. 3 and 4.

FIG. 3 shows a first embodiment of the control means of the elevating and lowering drive mechanism 20, and this example is a drive example when the second limit switch 43 is connected and disconnected.

Reference numeral 45 is a motor, 47 is a hydraulic pump, and a 49-micron filter.
Is configured.

Reference numeral 58 is a control valve for the reach cylinder 19, and this reach cylinder 19 is moved by the piston 53 to the liquid chamber 55.
And the liquid chamber 57, the outer mout 21 is moved in the front-rear direction based on the operation of the lot 19a fixed to the piston 53.

59 is a control valve for the lift cylinders 25a and 25b,
59a is a relief valve, and the pair of left and right lift cylinders 25a, 25b are divided into liquid chambers 63a, 63b and liquid chambers 65a, 65b by pistons 61a, 61b, and a rod 67a fixed to the pistons 61a, 61b. , 67b are connected to the inner mast 23.

Control valve 59 and lift cylinders 25a, 25b above
A flow regulator valve 69 is provided between the and.

Reference numerals 31 and 31 are a pair of auxiliary wheel cylinders provided at both ends of the drive wheel 3 in the vehicle width direction, and reference numeral 71 is a two-way solenoid valve that drives and controls the auxiliary wheel cylinders 31 and 31.

Reference numeral 43 is a second limit switch that is opened and closed by the movement of the rod 19a of the reach cylinder 19. The lead wires 73 and 75 connected to the second limit switch 43 are connected to the solenoid 71a of the two-way solenoid valve 71, and the battery 77 is arranged in the middle of the lead wire 73.

According to the first embodiment, the control valves 58 and 59 are both in the neutral position when the forklift is running without load, and the reach cylinder 19 and the lift cylinders 25a and 25b are in the neutral position.
Are not working together and the pair of auxiliary wheel cylinders 31,31
Is not supplied with hydraulic fluid. Therefore, the rods 31b and 31b project outward due to the elastic force of the spring 23 arranged in the auxiliary wheel cylinders 31 and 31 shown in FIG. 1, and the link 27 moves clockwise in the figure around the point P ₁ as a center. Is applied to the auxiliary wheels 5a and 5b, the ground surface E
Is in contact with a moderate elastic force.

Next, when the operation lever 58a of the control valve 58 is operated in the direction of A in the figure to operate the reach cylinder 19, the hydraulic fluid sent from the hydraulic pressure source 51 is supplied from the hydraulic passage T ₁ to the control valve 58 and the hydraulic passage T. Reach cylinder 19 through ₂
Since supplied to the liquid chamber 55, hydraulic fluid control valve 58 from the fluid path T ₃ in the liquid chamber 57 of the reach cylinder 41 together with the rod 19a is extended in the reach cylinder 19, liquid path T ₄ and micron filter Return to tank T via 49.

With the extension of the rod 19a, the outer mast 21 moves to the front of the vehicle, and the second limit switch 43 is set to "contact".

When operating the lift cylinders 25a and 25b separately from the above operation, the operation lever 59 of the control valve 59
When a is operated in the B direction shown in the drawing, the working fluid sent from the hydraulic pressure source 51 is also discharged from the fluid passage T ₁ to the control valve.
59, liquid channels T _5, the lift cylinders 25a through a flow regulator valve 69 and the fluid path T _6, 25b of the liquid chamber 63a, since it is supplied to 65a, the lift cylinder 25a, 25b of the rod 67a, 67b is extended The inner mast 23 is lifted up.

During the above operation, since the second limit switch 43 is in the “contact” state, the current obtained from the battery 77 is supplied to the solenoid 71a of the two-way solenoid valve 71 through the lead wires 73 and 75. The two-way solenoid valve 71 is switched to the C direction shown in the figure by the driving force of the solenoid 71a, and a part of the hydraulic fluid supplied to the liquid chambers 63a and 65a of the lift cylinders 25a and 25b flows to the flow regulator valve 69 and It is supplied to the liquid chamber on the rod 31b side from the supply / discharge ports 37, 37 of the auxiliary wheel cylinders 31, 31 via the two-way solenoid valve 71. Then the elastic force against the piston 33 and the rod 31b of the spring 35, 35, because 31b is moved in the shortening direction, the link 27 shown in FIG. 1, dihedral shown around the point P ₁ Rotational force in the clockwise direction is applied, and the auxiliary wheels 5a and 5b rise from the ground surface E.

When the auxiliary wheels 5a and 5b are driven to rise in this way, the load on the rear wheel side of the forklift body 10 is applied to the single drive wheel 3, so that the load on the drive wheel 3 increases and the start and start It is possible to prevent the drive wheels 3 from slipping when the vehicle is stopped.

FIG. 4 shows a second embodiment of the control means of the elevating and lowering drive mechanism 20, and this embodiment is a drive example when the first limit switch 41 is connected and disconnected. The same components are designated by the same reference numerals, and the reach cylinder 19 and the control valve 58 are omitted. In the case of this example, the liquid passage led from the two-way solenoid valve 71 is supplied to the liquid chamber on the left side of the auxiliary wheel cylinders 31, 31 in the figure via the supply / discharge ports 37, 37.

In the case of this example, if the operating lever 59a of the control valve 59 is operated in the B direction shown in the same manner as in the above example, the hydraulic pressure source 51
The hydraulic fluid sent out from the liquid passage T ₁ comes from the control valve 59, the liquid passage T ₅ , the flow regulator valve 69 and the liquid passage.
A pair of lift cylinders 25a via the T _6, 25b of the liquid chamber 63a, 65a
The rods 67a and 67b of the lift cylinders 25a and 25b extend and the inner mast 23 lifts up along the outer mast 21. Then the inner mast
Since the projection 23a (shown in FIG. 1) provided on the 23 makes the first limit switch 41 "contact", the current obtained from the battery 77 is transferred to the two-way solenoid valve 71 via the lead wires 73 and 75. When the solenoid 71a is energized and the driving force of the solenoid 71a switches the two-way solenoid valve 71 in the C direction, a part of the hydraulic fluid supplied to the liquid chambers 63a, 65a of the lift cylinders 25a, 25b is partially flow regulator valve. 69, the two-way solenoid valve 71, and the supply / discharge ports 37, 37 through the auxiliary wheel cylinders 31, 31.
Is supplied to the liquid chamber on the left side of. Then, the pistons 33, 33 and the rods 31b, 31b move in the extension direction, so that the link 27 shown in FIG. ₁ is given a rotational force in the clockwise direction in the figure around the point P ₁ to assist the auxiliary wheels. 5a and 5b are pressed against the ground surface E.

Therefore, when the lift cylinders 25a, 25b are lifted up, both auxiliary wheels 5a, 5b strongly contact the ground surface E,
The original function of the auxiliary wheels 5a, 5b is sufficiently exerted, and the posture of the forklift body 10 is prevented from becoming unstable due to the upward movement of the center of gravity.

FIG. 5 shows another example of mounting the auxiliary wheels 5a (5b),
In this example, the bracket 15a supporting the auxiliary wheel cylinder 31
Is rotatably suspended by a boss 87 fixed on the strength member 13a and a support shaft 89. Other configurations are substantially the same as those shown in FIG. 1 and are designated by the same reference numerals.

According to such a configuration, the auxiliary wheel 5a is supported by the support shaft 89.
Since (5b) freely rotates according to the traveling direction of the forklift main body 10, the movement of the auxiliary wheels 5a (5b) itself becomes smooth, and there is an advantage that the forklift main body 10 can be easily operated in the workplace. is there.

Effects of the Invention According to the present invention described in detail above, it is possible to control the grounding state of the auxiliary wheel according to the state of the vehicle, and it is possible to maintain the running property and stability of the vehicle in an optimum state. For example, when the reach cylinder extends and the center of gravity of the forklift body moves forward, the pair of auxiliary wheels are drive-controlled so as to rise from the ground surface. It is possible to increase the load on the drive wheel by applying the force to the drive wheel and prevent the drive wheel from slipping during transmission and stopping.
Further, the transmission acceleration and braking performance are improved, and the durability of the drive wheels is enhanced.

Also, when the lift cylinder extends and the center of gravity of the forklift body moves upward, the drive control is performed so that the pair of auxiliary wheels come into pressure contact with the ground surface, so the original function of the auxiliary wheels is fully exerted. As a result, the effect that the stability in the vehicle width direction is ensured even when the center of gravity moves upward is obtained.

[Brief description of drawings]

FIG. 1 is a side view of a three-wheel reach type forklift truck to which the present invention is applied, FIG. 2 is a rear view of the same, and FIG. 3 is a schematic view showing a first embodiment for controlling a lifting drive mechanism for auxiliary wheels. Four
FIG. 7 is a schematic view showing the second embodiment of the present invention, FIG. 5 is a side view showing another example of mounting the auxiliary wheels, FIG. 6 is a side view of a conventional three-wheel reach type forklift, and FIG. It is a figure. 1a, 1b …… driven wheel, 3 …… driving wheel, 5a, 5b …… auxiliary wheel, 10
...... Forklift body, 17 …… Straddle arm, 19
...... Reach cylinder, 21 …… Outer mast, 23 …… Inner mast, 25a, 25b …… Lift cylinder, 27 …… Link, 31 …… Auxiliary wheel cylinder, 33 …… Piston, 35 …… Spring, 37 …… Supply and discharge Ports, 41 …… first limit switch, 43 …… second limit switch, 51 …… hydraulic pressure source, 58,59 …… control valve, 69 …… flow regulator valve, 71 …… two-way solenoid valve.

Claims (3)

(57) [Claims] 1. A forklift body is disposed in front of the main body,
A straddle arm that guides the outer mast that moves in the front-rear direction according to the operation of the reach cylinder and at least one driven wheel is disposed near the front end, and a center line in the vehicle width direction at the lower rear of the forklift body. One drive wheel arranged in the vicinity, a pair of auxiliary wheels provided at both ends of the drive wheel in the vehicle width direction, and a slide cylinder are slidably arranged on the inner surface of the outer mast to operate the lift cylinder. A three-wheel reach-type forklift truck including an inner mast that moves in the up-and-down direction and a fork supported by the inner mast, wherein the pair of auxiliary wheels is provided with the auxiliary cylinder in conjunction with the operation of the reach cylinder and the lift cylinder. The ring rises above the ground,
Alternatively, an auxiliary wheel lifting device for a three-wheel reach-type forklift, which is equipped with a lifting drive mechanism that presses against the ground surface. 2. A control means for raising the pair of auxiliary wheels from the ground surface when the reach cylinder is extended and the center of gravity of the vehicle body is moved forward in the lifting drive mechanism. Item 3. An auxiliary wheel lifting device for a three-wheel reach type forklift according to Item 1. 3. The elevating and lowering drive mechanism is provided with control means for bringing the pair of auxiliary wheels into pressure contact with the ground surface when the lift cylinder extends and the center of gravity of the vehicle body moves upward. Item 3. An auxiliary wheel lifting device for a three-wheel reach type forklift according to Item 1.