JP4013348B2 - Reach forklift rear wheel support device - Google Patents

Description

[0001]
【Technical field】
The present invention relates to a rear wheel support device that can improve the stability and comfort of a reach forklift.
[0002]
[Prior art]
As is well known, reach forklifts have driving wheels for driving and steering, and caster wheels serving as auxiliary wheels as rear wheels. As a rear wheel support device for supporting these rear wheels, a mechanical device having a link mechanism has been conventionally used.
[0003]
For example, as shown in FIG. 7, the conventional rear wheel support device 9 includes a link mechanism 90 including four links 91 to 94 between the drive wheel 2 and the caster wheel 3 and two springs 95. , 96. The mechanical rear wheel support device 9 appropriately changes the ratio of load sharing to the drive wheels 2 and caster wheels 3 in accordance with the change in the rear wheel load, so that the load necessary for exerting the driving force can be obtained. The driving wheel 2 is loaded and the vibration from the road surface is absorbed.
[0004]
[Problems to be solved]
However, the conventional mechanical rear wheel support device 9 has the following problems.
That is, in the conventional rear wheel support device 9, the link mechanism 90 is an indispensable element, and the space occupied by the link mechanism 90 presses the living space of the driver's seat 8. Specifically, the width of the driver's seat 8 installed above the caster wheel is forced to be reduced due to the presence of the link mechanism 90.
[0005]
Further, the rear wheel support device 9 gives the driver a feeling that the spring 95 is extended and the vehicle body is lifted depending on a change in the road surface condition, and causes the driver to feel unstable. There is a case.
There is also a problem that the vehicle is likely to become unstable even when the vehicle is turning.
[0006]
The present invention has been made in view of such conventional problems, and provides a rear wheel support device capable of solving the problems of the conventional mechanical type and improving the stability and comfort of the reach forklift. It is something to try.
[0007]
[Means for solving problems]
The invention according to claim 1 is a rear wheel support device for supporting drive wheels and caster wheels in a reach forklift.
A first cylinder for supporting the drive wheel, a second cylinder for supporting the caster wheel, and a hydraulic circuit for controlling them;
The hydraulic circuit has a lock means for blocking oil flow in and out of the first cylinder and the second cylinder, and controls a pressure difference between the first cylinder and the second cylinder to a predetermined value or less. Balance means for controlling the pressure, and pressure control means for maintaining the pressure of the first cylinder within the optimum load range ,
The caster wheel is supported so as to be rotatable and turnable by a support portion without providing a link mechanism with the drive wheel.
The support portion is disposed so as to be swingable in the vertical direction by connecting the base end portion to a bracket provided below the vehicle body using a pin.
The tip of the second cylinder is Yes linked via a pin to the support portion, the rear end of the second cylinder, and wherein the tear Rukoto linked via a pin to a bracket provided on the vehicle body downward Reach forklift on rear wheel support device.
[0008]
What should be noted most in the present invention is that the driving wheel and caster wheel are supported by hydraulic cylinders such as the first cylinder and the second cylinder, and that the locking means, balancing means and pressure control means are provided in the hydraulic circuit. Is provided.
[0009]
As described above, the lock means is means for blocking oil flow in and out of the first cylinder and the second cylinder. For example, the shutoff can be realized by providing an open / close valve in an oil passage connected to each cylinder and closing the open / close valve.
[0010]
Further, the balance means in the hydraulic circuit is controlled so as to reduce the pressure difference between the first cylinder and the second cylinder. For example, the pressure difference can be reduced by appropriately connecting the first cylinder and the second cylinder through an oil passage.
The pressure control means controls the pressure of the first cylinder within the optimum load range. The optimum load range here refers to a pressure range in which the driving wheel can maintain a sufficient installation pressure to transmit a driving force to the road surface.
[0011]
Next, the operation of the present invention will be described.
In the rear wheel support device of the reach forklift of the present invention, the driving wheel and the caster wheel are supported by the first cylinder and the second cylinder. Therefore, the link mechanism that is essential in the case of the conventional mechanical type can be eliminated. Therefore, the space of the driver's seat can be greatly expanded by effectively using the space occupied by the conventional link mechanism.
[0012]
The first and second cylinders can be controlled by the balance means so that the pressure difference is appropriately reduced. On the other hand, the pressure state of the first cylinder and the second cylinder can be stably maintained by the lock means. For this reason, for example, when turning or when the loaded load is large, it is possible to maintain a stable pressure state by the action of the locking means and to stabilize the work. On the other hand, during normal stable travel, the balance means can balance the pressure of the rear wheels to achieve travel stability.
[0013]
The pressure of the first cylinder can always be controlled within the optimum load range by the pressure control means. Therefore, even when the load applied changes and the load applied to the rear wheels changes, the driving force of the driving wheels can be sufficiently transmitted to the road surface.
[0014]
Furthermore, since the drive wheels and caster wheels are supported by hydraulic pressure, the effect of mitigating fine vibrations from the road surface can be improved and the ride comfort can be improved as compared with the case where they are supported by conventional springs. it can.
[0015]
Thus, according to the present invention, it is possible to provide a rear wheel support device that can solve the problems of the conventional mechanical type and can improve the stability and comfort of the reach forklift.
[0016]
According to a second aspect of the present invention, the hydraulic circuit includes a connecting oil passage connecting the first cylinder and the second cylinder, and an opening / closing valve provided in the connecting oil passage. Preferably it is. In this case, the communication state of the connecting oil passage can be controlled by opening and closing the opening and closing valve, and thereby the pressure balance between the first cylinder and the second cylinder can be easily adjusted as appropriate.
[0017]
According to a third aspect of the present invention, the open / close valve can be opened only when the lateral acceleration generated when the reach forklift is turned is less than a predetermined value and the load is less than the predetermined value. It is preferable that it is comprised so that. That is, when the lateral acceleration during turning exceeds a predetermined value and the turning stability is reduced, or when the load load exceeds a predetermined value and the stability of the load is reduced, the balance means is made to function. Instability may further increase instability. Therefore, the increase in the instability can be avoided by limiting the opening operation of the opening / closing valve only to the above condition.
[0018]
According to a fourth aspect of the present invention, the hydraulic circuit includes a pressure increasing circuit for increasing the pressure of the first cylinder and a pressure reducing circuit for reducing the pressure of the first cylinder. It is preferable to have a switching valve that switches in three stages: only the pressure increasing circuit is opened, only the pressure reducing circuit is opened, and the pressure increasing circuit and the pressure reducing circuit are closed. In this case, the effect of the pressure control means can be easily obtained by opening and closing the pressure increasing circuit or the pressure reducing circuit.
Further, when combined with the structure having the connecting oil passage and the opening / closing valve, the operation and effect of the locking means can be easily obtained by closing both the opening / closing valve and the switching valve. it can.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment A rear wheel support device for a reach forklift according to an embodiment of the present invention will be described with reference to FIGS.
As shown in FIG. 2, the rear wheel support device 1 in this example supports the drive wheel 2 and the caster wheel 3 in the reach forklift 8.
As shown in FIGS. 1 and 2, the rear wheel support device 1 includes a first cylinder 51 that supports the drive wheel 2, a second cylinder 52 that supports the caster wheel 3, and a hydraulic circuit 6 that controls them. And have.
[0020]
As shown in FIG. 1, the hydraulic circuit 6 includes a locking means for blocking oil flow in and out of the first cylinder 51 and the second cylinder 52, and a pressure difference between the first cylinder 51 and the second cylinder 52. And a pressure control means for maintaining the pressure of the first cylinder 51 within the optimum load range.
[0021]
This will be described in detail below.
As shown in FIG. 2, the drive wheel 2 in the rear wheel support device 1 of this example is supported by a motor support 22 via a gear case 21 so as to be rotatable, and is connected to an upper drive motor 23. The drive wheel 2 is fixed to the vehicle body 80 via the motor support 22 so as to be movable up and down, and is connected to the first cylinder 51.
[0022]
As shown in FIG. 3, the motor support 22 has two guide holes 220 in the vertical direction. The guide hole 220 is slidably engaged with two support shafts 25 described later via a bearing 222.
As shown in FIGS. 2 and 3, the support shaft 25 is disposed in two vertical pairs of brackets 26 provided on the vehicle body 80 with the axis in the vertical direction.
[0023]
In addition, a cylinder connecting portion 225 is provided at an upper portion of the motor support 22 between the two guide holes 220. A tip 511 of the first cylinder 51 is connected to the cylinder connecting portion 225 by a pin 519. The rear end 512 of the first cylinder 51 is fixed to a cylinder fixing portion 516 provided on the vehicle body 80 via a pin 518.
[0024]
The caster wheel 3 in the rear wheel support device 1 has a structure in which two wheels 31 are connected by an axle 32 as shown in FIG. The axle 32 is supported by the support portion 33 so as to be rotatable and turnable.
As shown in FIGS. 2, 4, and 5, the support portion 33 is a bracket in which a support shaft 333 that supports the caster wheel 3 is suspended and a base end portion 331 provided in a U shape is provided in the vehicle body 80. It is arranged so as to be swingable in the vertical direction by being connected to pin 34 using a pin 527.
[0025]
The tip 521 of the second cylinder 52 is connected to the U-shaped interior 332 of the support portion 33 via a pin 529. The rear end 522 of the second cylinder 52 is connected to a bracket 35 provided on the vehicle body 80 via a pin 528.
A driver's seat 4 surrounded by the side walls 41 a and 42 and the bottom plate 43 is provided above the caster wheel 3.
[0026]
Next, the hydraulic circuit 6 for controlling the first cylinder 51 and the second cylinder 52 includes an oil tank 60, an oil pump 61, a plurality of oil passages 62 to 67, and electromagnetic valves 68, 69 as shown in FIG. have.
That is, the hydraulic circuit 6 first has a connecting oil passage 64 connecting the first cylinder 51 and the second cylinder 52, and an open / close valve (electromagnetic valve) 68 provided in the connecting oil passage 64.
[0027]
The hydraulic circuit 6 includes a pressure increasing circuit A for increasing the pressure of the first cylinder 51 and a pressure reducing circuit B for reducing the pressure of the first cylinder 51, and only the pressure increasing circuit A is opened. , An electromagnetic valve (switching valve) 69 for switching in three stages, that is, only the pressure reducing circuit B is opened and the pressure increasing circuit A and the pressure reducing circuit B are closed.
[0028]
As shown in FIG. 1, the pressure increasing circuit A is a route for sending hydraulic oil sent from the oil pump 61 to the first cylinder 51 from the oil passage 62 via the switching valve 69 and the oil passages 63 and 64. The decompression circuit B is a route for returning the hydraulic oil in the first cylinder 51 from the oil passage 64 to the oil tank 60 through the oil passage 63, the switching valve 69, and the oil passage 67.
[0029]
The locking means is substantially composed of the opening / closing valve 68 and the switching valve 69, and the oil inflow / outflow to the first cylinder 51 is locked by closing the opening / closing valve 68 and the switching valve 69. On the other hand, the locked state is released by opening the opening / closing valve 68.
[0030]
Further, the balance means is substantially composed of the opening / closing valve 68, and by opening it, the first cylinder 51 and the second cylinder 52 are connected by the connecting oil passage 64, thereby eliminating the pressure difference between the two. It is configured.
The pressure control means substantially comprises the pressure-increasing oil passage A, the pressure-reducing oil passage B, and the switching valve 69. With the switching valve 69, only the pressure-increasing circuit A is opened and only the pressure-reducing circuit B is opened. The pressure of the first cylinder 51 is controlled by switching in three stages, ie, opening, pressure increasing circuit A and pressure reducing circuit B are closed.
[0031]
The on-off valve 68 is configured to be able to open only when the lateral acceleration G generated when the reach forklift turns is not more than a predetermined value and the load is not more than a predetermined value.
The flow of these controls will be described with reference to FIG. This figure is a flowchart showing the flow of control.
[0032]
As shown in FIG. 6, the opening and closing valve 68 closed (OFF), the switching valve 69 the state of the closed (OFF) as the initial state, first, in step S1, the lateral acceleration G is equal to or less than a predetermined value _{G 0} in cornering Determine whether or not. When the lateral acceleration G exceeds the predetermined value G _0, the sequence proceeds to step S5, balancing means not function.
On the other hand, if the lateral acceleration G is less than the predetermined value, in step S2, the cargo load K is equal to or less than a predetermined value K _0. In this case, when the cargo load K exceeds a predetermined value K _0, the sequence proceeds to step S5, balancing means not function.
[0033]
Then, when the cargo load K is less than the predetermined value K _0, at step S3, the pressure difference D of the first and second cylinders is determined whether or not a predetermined value D ₀ or more. If the pressure difference is equal to or greater than a predetermined value D ₀ is the first, achieve pressure balance of the second cylinder by the opening and closing valve 68 is opened (ON).
Next, when the pressure difference D becomes a predetermined value smaller than _{D 0,} after the opening and closing valve 68 was closed (OFF) at step S45, the procedure proceeds to step S5.
[0034]
Next, in step S5, it is determined whether or not the pressure P of the first cylinder 51 is equal to or lower than a lower limit value PL. When the pressure P of the first cylinder 51 is equal to or lower than the lower limit value PL, the switching valve 69 is operated in step S6 to open the pressure increasing circuit A.
Next, when the pressure P of the first cylinder 51 exceeds the lower limit value PL, it is determined in step S7 whether or not the pressure P of the first cylinder 51 is equal to or higher than the upper limit value PU. When the pressure P of the first cylinder is equal to or higher than the upper limit value PU, the pressure reducing circuit B is opened by operating the switching valve 69 in step S8.
[0035]
Next, when the pressure P of the first cylinder 51 becomes less than the upper limit value PU, all the valves are closed (OFF) in step S9, the locking means is functioned, and the process returns to step S1.
As described above, in the hydraulic circuit 6 of this example, the opening / closing valve 68 is opened to function the balance means only when the turning stability and the load stability are relatively stable, and in other cases, One of the locking means and the pressure control means is configured to function while the on-off valve 68 is closed.
[0036]
Next, the effect of this example will be described.
In the rear wheel support device 1 of the reach forklift 8 of this example, the driving wheel 2 and the caster wheel 3 are supported by the first cylinder 51 and the second cylinder 52. Therefore, the space occupied by the link mechanism in the case of the conventional mechanical type can be effectively used, and the size of the driver's seat can be greatly increased. Specifically, as shown in FIG. 2, the position of the side wall 41 of the driver's seat 4 can be moved from the conventional position 41a to 41b, and the width dimension can be greatly increased.
[0037]
Further, the first and second cylinders 51 and 52 can be controlled by the balance means so that the pressure difference is appropriately reduced. On the other hand, the pressure state of the first cylinder 51 and the second cylinder 52 can be stably maintained by the locking means.
For this reason, for example, when turning or when the loaded load is large, it is possible to maintain a stable pressure state by the action of the locking means and to stabilize the work. On the other hand, during normal stable travel, the balance means can balance the pressure of the rear wheels to achieve travel stability.
[0038]
The pressure of the first cylinder 51 can always be controlled within the optimum load range by the pressure control means. Therefore, even when the load applied changes and the load applied to the rear wheels changes, the driving force of the driving wheels 2 can be sufficiently transmitted to the road surface.
[0039]
Further, since the driving wheel 2 and the caster wheel are supported by the hydraulic pressure using the first cylinder 51 and the second cylinder 52, the effect of mitigating fine vibration from the road surface compared to the case of supporting by the conventional spring. Can be improved, and the ride comfort can be improved.
In the hydraulic circuit 6 of this example, by providing an accumulator on the bottom side of the first cylinder 51 and the second cylinder 52, it is possible to absorb instantaneous pressure fluctuations and further improve riding comfort.
[0040]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a rear wheel support device that can solve the problems of the conventional mechanical type and can improve the stability and comfort of the reach forklift.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a configuration of a hydraulic circuit in an embodiment.
FIG. 2 is an explanatory view showing a configuration of a rear wheel support device in the embodiment.
3 is a cross-sectional view taken along line AA in FIG.
4 is a cross-sectional view taken along line BB in FIG.
5 is a cross-sectional view taken along the line CC in FIG. 4;
FIG. 6 is a flowchart showing a flow of control of the rear wheel support device in the embodiment.
FIG. 7 is an explanatory view showing a configuration of a rear wheel support device in a conventional example.
[Explanation of symbols]
1. . . Rear wheel support device,
2. . . Driving wheel,
3. . . Caster wheel,
51. . . First cylinder,
52. . . Second cylinder,

Claims (4)

In the rear wheel support device that supports the drive wheel and caster wheel in the reach forklift,
A first cylinder for supporting the driving wheel, a second cylinder for supporting the caster wheel, and a hydraulic circuit for controlling them,
The hydraulic circuit includes a lock means for blocking oil flow in and out of the first cylinder and the second cylinder, and a pressure difference between the first cylinder and the second cylinder is controlled to a predetermined value or less. Balance means for controlling the pressure, and pressure control means for maintaining the pressure of the first cylinder within the optimum load range ,
The caster wheel is supported so as to be rotatable and turnable by a support portion without providing a link mechanism with the drive wheel.
The support portion is disposed so as to be swingable in the vertical direction by connecting the base end portion to a bracket provided below the vehicle body using a pin.
The tip of the second cylinder is Yes linked via a pin to the support portion, the rear end of the second cylinder, and wherein the tear Rukoto linked via a pin to a bracket provided on the vehicle body downward Reach forklift rear wheel support device.   2. The reach forklift according to claim 1, wherein the hydraulic circuit includes a connecting oil passage connecting the first cylinder and the second cylinder, and an open / close valve provided in the connecting oil passage. Rear wheel support device.   The open / close valve according to claim 2 is configured to be able to open only when the lateral acceleration generated when the reach forklift turns is not more than a predetermined value and the load is not more than a predetermined value. Reach forklift rear wheel support device.   4. The hydraulic circuit according to claim 1, wherein the hydraulic circuit includes a pressure increasing circuit for increasing the pressure of the first cylinder and a pressure reducing circuit for reducing the pressure of the first cylinder. A reach wheel lift rear wheel support device having a switching valve for switching in three stages: only the pressure circuit is opened, only the pressure reducing circuit is opened, and the pressure increasing circuit and the pressure reducing circuit are closed.

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