JP2014104906A - Forklift - Google Patents

Abstract

PROBLEM TO BE SOLVED: To limit stroke of a cylinder for oscillating a drive wheel and an auxiliary wheel vertically in a proper range.SOLUTION: The suspension mechanism 3 for supporting a drive wheel 10 and an auxiliary wheel 20 has a stroke limit mechanism 6 for limiting stroke of a drive cylinder 4 and a caster cylinder 5. The stroke limit mechanism 6 has a piston 61 disposed in a cylinder tube 60 so as to freely slide, energization members 62a and 62b for applying energy to the piston 61 from both sides, regulation members 63a and 63b for regulating movement range of the piston 61, and a switching valve 67 for opening and closing a passage 65 for connecting first and second chambers 6a and 6b in the cylinder tube 60. When the switching valve 67 becomes closing state, the drive cylinder 4 and the caster cylinder 5 are limited so as to stretch by regulated stroke amount by movement range of the piston 61 according to a stroke position when the switching valve 67 becomes closing state.

Description

  The present invention relates to a forklift provided with a suspension mechanism that supports drive wheels and auxiliary wheels.

  Conventionally, a forklift has a driving wheel and an auxiliary wheel as rear wheels. Further, the forklift has a suspension mechanism that supports the driving wheel and the auxiliary wheel on the vehicle body, absorbs vibration from the road surface, and applies a load (axial weight) necessary to transmit the driving force to the road surface to the driving wheel. It aims at the stability of the car body.

  As for the suspension mechanism of a forklift, a driving wheel and an auxiliary wheel are linked by a mechanical link mechanism as in Patent Document 1, and a driving wheel and an auxiliary wheel are linked by a hydraulic circuit as in Patent Document 2. There is something that I let you do.

  FIG. 6 shows a conventional suspension mechanism. This suspension mechanism has the same configuration as the suspension mechanism disclosed in Patent Document 2, and supports the drive wheels 10 and auxiliary wheels 20 on the left and right sides of the vehicle body. The suspension mechanism includes a drive cylinder 4 for swinging the drive wheel 10 up and down, a caster cylinder 5 for swinging the auxiliary wheel 20 up and down, and a hydraulic circuit for controlling both cylinders 4 and 5. Prepare.

  The drive cylinder 4 includes a piston portion 40 and a lot portion 41, and the interior thereof is partitioned into a first chamber 4 a and a second chamber 4 b by the piston portion 40. Similarly, the caster cylinder 5 includes a piston portion 50 and a rod portion 51, and the interior thereof is partitioned into a first chamber 5 a and a second chamber 5 b by the lot portion 50. The first chamber 4 a of the drive cylinder 4 and the first chamber 5 a of the caster cylinder 5 are connected by a pipe line 38. The conduit 38 is provided with a switching valve 39 that opens and closes the conduit 38. The second chamber 4 b of the drive cylinder 4 and the second chamber 5 b of the caster cylinder 5 are connected by a pipe line 37.

  Furthermore, pipelines 30 and 31 for supplying hydraulic oil to both cylinders 4 and 5 from a pump (not shown) and discharging hydraulic oil from both cylinders 4 and 5 to a tank (not shown), and hydraulic oil There are provided a switching valve 32 for switching the supply direction and pilot check valves 33, 34 for preventing backflow of hydraulic oil.

  In the above configuration, both cylinders 4 and 5 can be extended and contracted in the same direction by supplying hydraulic oil from the pump to both cylinders 4 and 5 and switching the supply direction of hydraulic oil by the switching valve 32. Thereby, the vehicle height H of the vehicle body 7 can be adjusted.

  When the supply of hydraulic oil from the pump is stopped, the pilot check valves 33 and 34 are closed, and the hydraulic circuit is closed. As shown in FIG. 6, when the switching valve 39 is opened, the hydraulic oil flows between the first chamber 4 a of the drive cylinder 4 and the first chamber 5 a of the caster cylinder 5, and further, the second chamber of the drive cylinder 4. 4b and the second chamber 5b of the caster cylinder 5 can flow. Therefore, when one of the cylinders 4 and 5 contracts, the other cylinder 5 and 4 expands. As a result, the drive wheel 10 and the auxiliary wheel 20 swing up and down in opposite directions like a seesaw. To do. As a result, vibration from the road surface during traveling can be absorbed.

  When the switching valve 39 is switched to the closed state, the hydraulic oil cannot move between the cylinders 4 and 5, so the cylinders 4 and 5 are locked and cannot expand and contract, and the drive wheel 10 and the auxiliary wheel 20 do not swing. As a result, vibration from the road surface cannot be absorbed and stable running cannot be performed, but the vehicle body 7 does not tilt left and right, so that cargo handling work can be performed with a stable vehicle body posture. That is, in this forklift, the cylinders 4 and 5 are unlocked during traveling, and the cylinders 4 and 5 are locked during cargo handling work.

  By the way, forklifts include a three-way stacking truck type forklift that can load not only loads in front of the vehicle body 7 but also loads on the left and right. It is assumed that the forklift includes the suspension mechanism shown in FIG. 6, the switching valve 39 is closed, the cylinders 4 and 5 are locked, and a fork is loaded from the right side of the vehicle body 7. At this time, since an offset load is applied to the auxiliary wheel 20 side, the pressure increases only in the first chamber 5a of the caster cylinder 5.

  When the pressure is not balanced between the cylinders 4 and 5 as described above, when the switching valve 39 is switched to the open state for traveling, the cylinders 4 and 5 are unlocked. The vehicle body expands and contracts instantaneously until the pressures are equal to each other. As a result, the vehicle body 7 suddenly tilts greatly, which is very dangerous.

  In order to solve the above problem, it is only necessary to use a cylinder with a short stroke for both the cylinders 4 and 5 so that the driving wheel 10 and the auxiliary wheel 20 swing only about several millimeters. In this way, the relatively flat road surface in the warehouse can run sufficiently stably, and further, even if the cylinders 4 and 5 are not locked as described above, the vehicle body 7 hardly tilts so that the vehicle body posture is stable. The cargo handling work can be done at. However, if a cylinder with a short stroke is employed, for example, problems as shown in FIGS. 7A and 7B occur.

  When traveling on a rough road outside the warehouse as shown in FIG. 7A, if the stroke of the drive cylinder 4 is short, the drive cylinder 4 cannot be extended until a sufficient axle load is applied to the drive wheel 10, and as a result, the drive wheel 10 slips. End up. Further, when the stroke of the caster cylinder 5 is short, the caster cylinder 5 cannot be contracted until the road surface level can be absorbed, and as a result, the vehicle body 7 is pushed up.

  Further, as shown in FIG. 7B, when the drive wheel 10 is worn, the drive cylinder 4 reaches the extension side stroke end when the stroke is short, and cannot extend further. Therefore, the vehicle height H cannot be raised. If the stroke of the caster cylinder 5 is short, the caster cylinder 5 reaches the contraction side stroke end and cannot contract any more. Therefore, the vehicle height H cannot be lowered until the driving wheel 10 is firmly in contact with the road surface.

  As described above, in the suspension mechanism that switches both cylinders 4 and 5 between locking and unlocking, if the strokes of both cylinders 4 and 5 are lengthened, there is a risk that the vehicle body 7 is greatly inclined at the moment of unlocking for traveling. On the other hand, if the strokes of the cylinders 4 and 5 are shortened, there is an adverse effect on rough road traveling and vehicle height adjustment.

Japanese Patent Laid-Open No. 10-45395 JP 2011-240837 A

  An object of the present invention is to provide a forklift provided with a suspension mechanism that can limit the stroke of a cylinder for swinging a drive wheel and an auxiliary wheel up and down to an appropriate range.

In order to solve the above-described problem, a forklift according to the present invention includes a drive wheel that travels a vehicle body, an auxiliary wheel that assists traveling, and a suspension mechanism that supports the drive wheel and the auxiliary wheel. A drive cylinder for swinging the drive wheel up and down, and a caster cylinder for swinging the auxiliary wheel up and down, and hydraulic oil flows between the drive cylinder and the caster cylinder so that the drive wheel and the auxiliary wheel Are forklifts that swing up and down in opposite directions,
The suspension mechanism includes a stroke limiting mechanism that limits the stroke of the drive cylinder and the caster cylinder.
The stroke limiting mechanism is provided with a cylinder tube filled with hydraulic oil, a slidable inside the cylinder tube, a first chamber communicating with the drive cylinder, and a second chamber communicating with the caster cylinder. Provided in each of the first chamber and the second chamber, and provided in each of the first chamber and the second chamber, and provided in each of the first chamber and the second chamber, A restriction member that restricts, a passage that connects the first chamber and the second chamber, and a switching valve that opens and closes the passage to open and shut off the flow of hydraulic oil between the first chamber and the second chamber. When the switching valve is closed, the drive cylinder and caster cylinder are controlled so as to expand and contract by the stroke amount defined by the piston movement range with reference to the stroke position when the switching valve is closed. It is, that the switching valve in the open state, the drive cylinder and the caster cylinder is characterized in that the limit of the stroke is canceled.

  Preferably, the stroke limiting mechanism includes stroke adjusting means for adjusting a stroke amount by adjusting a moving range of the piston.

  In the forklift according to the present invention, the stroke limiting mechanism configured as described above allows the drive cylinder for the drive wheel and the caster cylinder for the auxiliary wheel to be expanded and contracted using a stroke limited state in which only a small stroke amount can be expanded and contracted, and the entire stroke. It is possible to switch to the stroke limit release state.

  In the stroke limit state, the swinging of the drive wheels and auxiliary wheels is greatly suppressed. Thereby, since the vehicle body hardly tilts to the left and right, it is possible to load and unload loads with a stable vehicle body posture. Further, if the floor surface is relatively flat in the warehouse, even if the swing is suppressed, the vibration from the road surface is absorbed and the vehicle can travel sufficiently stably. Therefore, a series of operations in the warehouse can be performed without any problems. On the other hand, in the stroke limit release state, both cylinders can be expanded and contracted using the entire stroke, so that it is possible to travel on a rough road outside the warehouse and adjust the vehicle height.

  The stroke limiting unit limits the stroke based on the stroke position of both cylinders when the stroke is limited (the switching valve is closed). Even if the stroke positions of both cylinders change due to wear of the drive wheels or due to vehicle height adjustment, both cylinders can be expanded and contracted up and down within a slight stroke amount centering on the changed stroke position. As a result, it is possible to avoid the driving wheels from being worn or the stroke position from being changed due to the adjustment of the vehicle height, so that proper swinging of the driving wheels and the auxiliary wheels cannot be obtained.

It is a side view of the forklift concerning the present invention. It is a top view of the forklift concerning the present invention. It is a schematic diagram of a suspension mechanism concerning the present invention. It is a figure of a stroke limiting unit, Drawing A is a fragmentary front sectional view, and Drawing B is a side view. It is a schematic diagram of a suspension mechanism concerning the present invention. It is the schematic of the conventional sprinkling mechanism. It is a figure for demonstrating a problem when a short stroke cylinder is employ | adopted with the conventional suspension mechanism.

  Hereinafter, a forklift according to the present invention will be described with reference to the drawings.

  As shown in FIGS. 1 and 2, the forklift according to the present embodiment is a three-way stacking truck type forklift. The forklift includes a vehicle body 7, a mast device 70 erected in front of the vehicle body 7, and a cargo handling device 71 supported so as to be movable up and down along the mast device 70.

  The cargo handling device 71 supports a pair of forks 72. The cargo handling device 71 is movable along a pair of side shift rails 73 extending in the left-right direction, and thereby the fork 72 can be shifted in the left-right direction. In addition, the cargo handling device 71 can turn the fork 72 around the rotation shaft 74 extending in the vertical direction.

  The forklift can be protruded in three directions of the running direction and the left-right direction by shifting the fork 72 in the left-right direction and turning as shown by the one-dot chain line in FIG. The load on the left and right of the vehicle body 7 can also be loaded.

  The forklift includes a driver's seat 75 on which the operator gets on the vehicle body 7 and controls the forklift. The forklift includes a front wheel 76 (FIG. 1) and, as a rear wheel, a driving wheel 10 that causes the vehicle body 7 to travel on the left rear portion of the vehicle body 7 and a driving wheel 10 that follows the driving wheel 10 on the right rear portion of the vehicle body 7 assists traveling Auxiliary wheel 20 to be provided.

  Further, as shown in FIG. 3, the forklift includes a drive unit 1 having drive wheels 10, a caster unit 2 having auxiliary wheels 20, and a suspension mechanism 3 that supports the drive wheels 10 and auxiliary wheels 20 on the vehicle body 7. The drive unit 1 includes a drive motor (not shown) for driving the drive wheels 10, a gear unit 11 for transmitting the power of the drive motor to the drive wheels 10, a drive support 12 for supporting these, and the like. The caster unit 2 includes a caster support 21 that supports the auxiliary wheel 20 and a spring 22 that presses and biases the auxiliary wheel 20.

  The suspension mechanism 3 includes a drive cylinder 4 for swinging the drive wheel 10 up and down, and a caster cylinder 5 for swinging the auxiliary wheel 20 up and down. Both cylinders 4 and 5 are cylinders having a stroke of, for example, about several tens of mm. The drive cylinder 4 includes a piston part 40 and a rod part 41. The inside of the drive cylinder 4 is partitioned into a first chamber 4 a on the piston portion 40 side and a second chamber 4 b on the rod portion 41 side through the piston portion 40. The first chamber 4a and the second chamber 4b are filled with hydraulic oil. The rod portion 41 is connected to the drive support 12. Thus, the drive wheel 10 is configured to swing up and down when the drive cylinder 4 expands and contracts.

  Similarly, the caster cylinder 5 includes a piston part 50 and a rod part 51. The caster cylinder 5 is partitioned through a piston portion 50 into a first chamber 5a on the piston portion 50 side and a second chamber 5b on the rod portion 51 side. The first chamber 5a and the second chamber 5b are filled with hydraulic oil. The rod portion 51 of the caster cylinder 5 is connected to the caster support 21 via the spring 22. Thus, when the caster cylinder 5 expands and contracts, the auxiliary wheel 20 is configured to swing up and down.

  Furthermore, the suspension mechanism 3 includes a hydraulic circuit for controlling both cylinders 4 and 5. In the hydraulic circuit, pipelines 30 and 31 for supplying and discharging hydraulic oil from a pump (not shown) to both cylinders 4 and 5 and from both cylinders 4 and 5 to a tank (not shown) are provided. Furthermore, an electromagnetic switching valve 32 for switching the supply direction of hydraulic oil and pilot check valves 33 and 34 for preventing backflow of hydraulic oil are provided.

  Furthermore, the suspension mechanism 3 includes a stroke limiting unit 6 (stroke limiting mechanism) for limiting the strokes of both cylinders 4 and 5 in the hydraulic circuit.

  As shown in FIG. 4A, the stroke limiting unit 6 includes a cylinder tube 60 filled with hydraulic oil and a piston 61 without a rod that is slidably provided in the cylinder tube 60. The inside of the cylinder tube 60 is partitioned into a first chamber 6a and a second chamber 6b by a piston 61.

  Each of the first chamber 6a and the second chamber 6b is provided with springs 62a and 62b (urging members), and the urging force urges the piston 61 from both sides. Thus, the piston 61 is held at the neutral position C when the pressures on both sides of the first chamber 6a and the second chamber 6b are balanced.

  Furthermore, adjustment bolts 63a and 63b (regulating members) for limiting the movement range L of the piston 61 in the cylinder tube 60 are provided in each of the first chamber 6a and the second chamber 6b. The adjustment bolts 63a and 63b are provided so as to penetrate the covers 64a and 64b on both sides of the cylinder tube 60, and their tips are located in the first chamber 6a and the second chamber 6b, respectively. Thus, the piston 61 moves only within the movement range L between the adjusting bolts 63a and 63b. The movement range L includes a movement range La from the center position C to the tip of the adjustment bolt 63a, and a movement range Lb from the center position C to the tip of the adjustment bolt 63b. The moving ranges La and Lb are set in accordance with the configuration of the suspension mechanism 3 such as the drive cylinder 4 and the caster cylinder 5, but are about several millimeters.

  On the upper side of the cylinder tube 60, a spacer 66 is provided in which a passage 65 is formed for connecting and communicating the first chamber 6a and the second chamber 6b. Further, a switching valve 67 is provided above the spacer 66 to open and close the passage 65 to open and close the flow of hydraulic oil between the first chamber 6a and the second chamber 6b.

  As shown in FIG. 4B, the cylinder tube 60 is provided with a piping port 68a for the first chamber 6a and a piping port 68b for the second chamber 6b. A pipeline 35 (FIG. 3) is connected to the piping port 68a for the first chamber 6a, and the first chamber 6a of the stroke limiting unit 6 and the first chamber of the drive cylinder 4 are connected via the pipeline 35 as shown in FIG. 4a communicates. Similarly, a pipeline 36 (FIG. 3) is connected to the piping port 68b for the second chamber 6b, and the second chamber 6b of the stroke limiting unit 6 and the caster cylinder 5 are connected via the pipeline 36 as shown in FIG. The first chamber 5a communicates. Further, the second chamber 4 b of the drive cylinder 4 and the second chamber 5 b of the caster cylinder 5 communicate with each other via a pipe line 37.

  Next, the operation of the suspension mechanism 3 configured as described above will be described. As shown in FIG. 3, when the switching valve 67 of the stroke limiting unit 6 is in the open state (ON), the hydraulic oil can flow between the first chamber 6 a and the second chamber 6 b through the passage 65. At this time, both cylinders 4 and 5 can be expanded and contracted using the full stroke without being restricted by a stroke restriction unit 6 as described later.

  If the switching valve 67 is in the open state, the hydraulic oil from the pump can be supplied to the first chambers 4a and 5a of the cylinders 4 and 5 so that the cylinders 4 and 5 can be extended at the same time. it can. If the switching valve 32 is switched from the state shown in FIG. 3, the hydraulic oil from the pump can be supplied to the second chambers 4b and 5b of the cylinders 4 and 5 so that the cylinders 4 and 5 can be contracted simultaneously. H can be lowered. Thus, the vehicle height can be adjusted.

  When the supply of hydraulic oil from the pump is stopped, the pilot check valves 33 and 34 are closed, and the hydraulic circuit is closed. If the switching valve 67 is in the open state, the hydraulic oil flows between the cylinders 4 and 5, so that the cylinders 4 and 5 expand and contract in the opposite directions using the entire stroke. The auxiliary wheels 20 swing up and down in opposite directions.

  For example, when an upward load is applied to the drive wheel 10, the hydraulic oil is discharged from the first chamber 4 a of the drive cylinder 4, and the pipeline 35, the stroke limiting unit 6 (first chamber 6 a, passage 65, second chamber). 6b), and the pipe 36 is supplied to the first chamber 5a of the caster cylinder 5. Further, the hydraulic oil is discharged from the second chamber 5 b of the caster cylinder 5 and supplied to the second chamber 4 b of the drive cylinder 4 through the pipe line 37. That is, when an upward load is applied to the drive wheel 10, the drive cylinder 4 contracts, the caster cylinder 5 extends, and a downward load is applied to the auxiliary wheel 20.

  Similarly, when an upward load is applied to the auxiliary wheel 20, the hydraulic oil is discharged from the first chamber 5 a of the caster cylinder 5, and the pipeline 36, the stroke limiting unit 6 (second chamber 6 b, the passage 65, the first It is supplied to the first chamber 4a of the drive cylinder 4 through the chamber 6a) and the conduit 35. Further, the hydraulic oil is discharged from the second chamber 4 b of the drive cylinder 4 and supplied to the second chamber 5 b of the caster cylinder 5 through the pipe 37. That is, when an upward load is applied to the auxiliary wheel 20, the caster cylinder 5 contracts, the drive cylinder 4 extends, and a downward load is applied to the drive wheel 10.

  Thus, when the switching valve 67 is opened, the cylinders 4 and 5 can be expanded and contracted using the entire stroke, so that the drive wheel 10 and the auxiliary wheel 20 can be swung up and down greatly. Accordingly, it is possible to travel on a rough road as shown in FIG. 7A.

  As described above, when the switching valve 67 is in the open state, vehicle height adjustment and rough road traveling are possible. However, in this state, when an unbalanced load is applied to either the left or right side of the vehicle body 7, the vehicle body 7 is greatly tilted to the left and right, so that the cargo handling operation cannot be performed with a stable vehicle body posture.

  When the switching valve 67 of the stroke limiting unit 6 is closed (OFF), the hydraulic oil cannot flow between the first chamber 6 a and the second chamber 6 b through the passage 65. As a result, both cylinders 4 and 5 are subjected to stroke limitations as follows.

  For example, when an upward load is applied to the drive wheel 10, the hydraulic oil is discharged from the first chamber 4 a of the drive cylinder 4 and supplied to the first chamber 6 a of the stroke limiting unit 6 through the pipe 35. Since the switching valve 67 is closed, the hydraulic oil supplied to the first chamber 6a does not flow to the second chamber 6b through the passage 65. As a result, the hydraulic oil supplied to the first chamber 6a pushes the piston 61 and moves from the center position C (FIG. 4A) to the second chamber 6b side. As a result, the hydraulic oil is discharged from the second chamber 6 b and supplied to the first chamber 5 a of the caster cylinder 5 through the conduit 36. Further, the hydraulic oil is discharged from the second chamber 5 b of the caster cylinder 5 and supplied to the second chamber 4 b of the drive cylinder 4 through the conduit 37.

  That is, when an upward load is applied to the drive wheel 10, the drive cylinder 4 contracts, the caster cylinder 5 extends, and a downward load is applied to the auxiliary wheel 20. However, as shown in FIG. 4A, when the piston 61 moves from the center position C to the second chamber 6b side, it directly hits the adjustment bolt 63b and stops, and the hydraulic oil in the second chamber 6b cannot be pushed any further. Therefore, only a small amount of hydraulic oil is discharged from the second chamber 6b. Therefore, the drive cylinder 4 contracts only slightly and cannot contract further, and the caster cylinder 5 expands only slightly and cannot extend further.

  Similarly, when an upward load is applied to the auxiliary wheel 20, the hydraulic oil is discharged from the first chamber 5 a of the caster cylinder 5 and supplied to the second chamber 6 b of the stroke limiting unit 6 through the conduit 36. And the hydraulic oil supplied to the 2nd chamber 6b pushes the piston 61, and moves it from the center position C to the 1st chamber 6a side. As a result, the hydraulic oil is discharged from the first chamber 6 a and supplied to the first chamber 4 a of the drive cylinder 4 through the conduit 35. Further, the hydraulic oil is discharged from the second chamber 4 b of the drive cylinder 4 and supplied to the second chamber 5 b of the caster cylinder 5 through the pipe line 37.

  That is, when an upward load is applied to the auxiliary wheel 20, the caster cylinder 5 contracts, the drive cylinder 4 extends, and a downward load is applied to the drive wheel 10. However, as shown in FIG. 4A, when the piston 61 moves from the center position C to the first chamber 6a side, it directly hits the adjustment bolt 63a and stops, and the hydraulic oil in the first chamber 6a cannot be pushed any further. Therefore, only a small amount of hydraulic oil is discharged from the first chamber 6a. Accordingly, the caster cylinder 5 contracts only slightly and cannot further contract, and the drive cylinder 4 extends only slightly and cannot extend any more.

  Thus, when the switching valve 67 is closed, both the cylinders 4 and 5 can expand and contract, but the stroke range is limited by the stroke limiting unit 6 and cannot be expanded and contracted using the entire stroke. As a result, the swinging of the drive wheel 10 and the auxiliary wheel 20 is suppressed.

  As described above, both cylinders 4 and 5 can expand and contract only until the piston 61 hits the adjusting bolts 63a and 63b. That is, the stroke amount when both cylinders 4 and 5 are limited is defined by the movement ranges La and Lb of the piston 61. When the movement ranges La and Lb are small, the stroke amount is small, and when the movement ranges La and Lb are large, the stroke amount is large.

  In this embodiment, as shown in FIG. 4A, the adjusting bolts 63a and 63b (regulating members) respectively rotate by gripping portions protruding outward from the covers 64a and 64b, thereby reducing the amount of insertion into the cylinder tube 60. The moving ranges La and Lb of the piston 61 can be adjusted respectively. That is, the adjusting bolts 63a and 63b function as stroke adjusting means for adjusting the movement ranges La and Lb of the piston 61 to adjust the stroke amount at the time of restriction. The adjustment bolts 63a and 63b can freely set the swing amount of the drive wheel 10 and the auxiliary wheel 20 at the time of restriction.

  The movement ranges La and Lb are appropriately adjusted to suppress the swinging of the driving wheel 10 and the auxiliary wheel 20 to about several mm. As a result, a stable vehicle body posture in which the vehicle body 7 hardly tilts to the left and right can be obtained, so that the forklift can safely carry out cargo handling work. Furthermore, since vibration from a relatively flat road surface in the warehouse can be absorbed, the forklift can travel in the warehouse sufficiently safely.

  Furthermore, the stroke limiting unit 6 limits the strokes of the cylinders 4 and 5 with reference to the stroke position (positions of the rod portions 40 and 50 and the piston portions 41 and 51) when the switching valve 67 is closed. That is, both cylinders 4 and 5 expand and contract up and down within a stroke amount range defined by the movement ranges La and Lb of the piston 61 around the stroke position when the switching valve 67 is closed.

  For example, as shown in FIG. 5, when the driving wheel 10 is worn, the switching valve 67 is once opened to release the stroke restriction, and the stroke positions of both cylinders 4 and 5 are changed to drive. The vehicle body 7 is stabilized so that a sufficient axial load is applied to the wheel 10. When the vehicle body 7 is stabilized, the pressures of the cylinders 4 and 5 are balanced, so that the piston 61 is held at the center position C by the springs 62a and 62b. In this way, even if the stroke positions of both cylinders 4 and 5 change, if the switching valve 67 is closed again, both cylinders 4 and 5 will have the above stroke amount based on the stroke position after the change. The auxiliary wheel 10 and the drive wheel 20 swing up and down as the range extends and contracts.

  Similarly, even if the vehicle height is adjusted and the stroke position of both cylinders 4 and 5 changes, when the switching valve 67 is closed again thereafter, the strokes of both cylinders 4 and 5 are based on the changed stroke position. Furthermore, it is limited to the range of the stroke amount.

  Therefore, even if the driving wheel 10 is worn or the vehicle height is adjusted, the driving wheel 10 and the auxiliary wheel 20 can be appropriately swung up and down even if the stroke position changes.

  As described above, even if the suspension mechanism 3 employs a cylinder having a long stroke of about several tens of millimeters for both cylinders 4 and 5, the stroke limiting unit 6 allows the strokes of both cylinders 4 and 5 to be within an appropriate range. Limiting and restraining the drive wheel 10 and auxiliary wheel 20 from swinging to about a few millimeters enables both a cargo handling operation with a stable vehicle body posture and a stable running on a relatively flat road surface in a warehouse. . That is, a series of operations in the warehouse can be performed without any problems. Furthermore, the suspension mechanism 3 releases the restriction of the strokes of the cylinders 4 and 5 by the stroke restriction unit 6 and releases the suppression of the swinging of the drive wheels 10 and the auxiliary wheels 20, thereby driving on a rough road and adjusting the vehicle height. Is possible.

  Note that the stroke restriction unit 6 switches between stroke restriction and restriction release by, for example, operating operation switches such as “bad road running mode” and “vehicle height adjustment mode” provided in the driver's seat 75. When the operator travels on a rough road or needs to adjust the vehicle height, by pressing this operation switch, the switching valve 67 is opened, and the stroke restriction is released.

  Further, the stroke restriction unit 6 and the restriction release may be switched automatically by the stroke restriction unit 6. For example, in FIG. 3, a pressure sensor (not shown) that detects the pressure in the first chamber 4 a of the drive cylinder 4 is provided in the pipe 35. When traveling on a rough road as shown in FIG. 7A in a stroke-limited state, the driving wheel 10 is not sufficiently loaded with the axle load, so the pressure in the first chamber 4a detected by the pressure sensor becomes low. Therefore, when the pressure detected by the pressure sensor becomes a predetermined value or less, the changeover valve 67 is opened to cancel the stroke restriction of both cylinders 4 and 5 so that it can automatically cope with rough road traveling. It may be.

  As mentioned above, although preferred embodiment of this invention was described, the structure of this invention is not limited to this embodiment naturally.

1 Drive Unit 10 Drive Wheel 2 Caster Unit 20 Auxiliary Wheel 3 Suspension Mechanism 4 Drive Linder 5 Castor Cylinder 6 Stroke Limit Unit (Stroke Limit Mechanism)
6a 1st chamber 6b 2nd chamber 60 Cylinder tube 61 Piston 62a, 62b Spring (biasing member)
63a, 63b Adjustment bolt (regulating member / stroke adjusting means)
65 Passage 67 Switching valve 7 Body L (La, Lb) Piston movement range

In order to solve the above problems, the forklift according to the present invention is a suspension that supports the vehicle body 7, the front wheels 76 and the rear wheels 10 and 20, and the driving wheels 10 and the auxiliary wheels 20 as the rear wheels 10 and 20. a mechanism 3, comprising a suspension mechanism 3 comprises a drive cylinder 4 for swinging the drive wheels 10 up and down, the caster cylinder 5 to swing the auxiliary wheel 20 up and down, the drive cylinder 4 Includes a piston portion 40 and a rod portion 41, and is partitioned by the piston portion 40 into a first chamber 4 a on the piston portion 40 side and a second chamber 4 b on the rod portion 41 side. It comprises a section 51, partitioned by the piston portion 50 into the second chamber 5b of the first chamber 5a and the rod portion 51 side of the piston 50 side, hydraulic fluid, the drive cylinder 4 With flow between first chamber 4a and the first chamber 5a of the caster cylinder 5, by flowing between the second chamber 5b of the second chamber 4b and the caster cylinder 5 of the drive cylinder 4, the drive wheel 10 and auxiliary wheel 20 is Forklifts that swing up and down in opposite directions,
The suspension mechanism 3 includes a stroke limiting mechanism 6 that limits the strokes of the drive cylinder 4 and the caster cylinder 5 .
Stroke limiting mechanism 6 includes a cylinder tube 60 the hydraulic oil is filled, a piston rod 61 which is slidably in the cylinder tube 60, comprises a, the interior of the cylinder tube 60, partitioning the piston rod 61 The first chamber 6a that communicates with the first chamber 4a of the drive cylinder 4 and the second chamber 6b that communicates with the first chamber 5a of the caster cylinder 5,
Provided in each of the first chamber 6a and a second chamber 6b of the cylinder tube 60, biasing member 62a for biasing the piston 61 from both sides, and 62b, a first chamber 6a and a second chamber 6b of the cylinder tube 60 Each of which is provided with a restriction member 63a, 63b for restricting the movement range L of the piston 61 , a passage 65 connecting the first chamber 6a and the second chamber 6b of the cylinder tube 60 , and opening and closing the passage 65 , A switching valve 67 for opening and shutting off the flow of hydraulic oil between the first chamber 6a and the second chamber 6b of the cylinder tube 60 ,
When the switching valve 67 is closed, the drive cylinder 4 and the caster cylinder 5 have a stroke amount defined by the movement range L of the piston 61 with reference to the stroke position when the switching valve 67 is closed. Stroke is limited to expand and contract,
When the switching valve 67 is opened, the drive cylinder 4 and the caster cylinder 5 are released from the stroke restriction.

Preferably, the regulating members 63a and 63b are provided so as to penetrate the covers 64a and 64b on both sides of the cylinder tube 60, and the amount of insertion of the regulating members 63a and 63b into the cylinder tube 60 is changed to move the piston 61 . By adjusting the range L , the stroke amounts of the drive cylinder 4 and the caster cylinder 5 when the stroke is limited can be adjusted .

Claims (2)

A driving wheel for traveling on the vehicle body; an auxiliary wheel for assisting traveling; and a suspension mechanism for supporting the driving wheel and the auxiliary wheel, wherein the suspension mechanism is a drive for swinging the driving wheel up and down. A cylinder and a caster cylinder for swinging the auxiliary wheel up and down, and the hydraulic oil flows between the drive cylinder and the caster cylinder so that the driving wheel and the auxiliary wheel are in opposite directions, respectively. A forklift that swings up and down,
The suspension mechanism includes a stroke limiting mechanism that limits a stroke of the drive cylinder and the caster cylinder;
The stroke limiting mechanism is
A cylinder tube filled with the hydraulic oil;
A piston which is slidably provided in the cylinder tube, and divides the cylinder tube into a first chamber communicating with the drive cylinder and a second chamber communicating with the caster cylinder;
A biasing member that is provided in each of the first chamber and the second chamber and biases the piston from both sides;
A regulating member that is provided in each of the first chamber and the second chamber and restricts a moving range of the piston;
A passage connecting the first chamber and the second chamber;
A switching valve that opens and closes the passage to open and shut off the flow of the hydraulic oil between the first chamber and the second chamber;
When the switching valve is closed, the drive cylinder and the caster cylinder have a stroke amount defined by the movement range of the piston with reference to a stroke position when the switching valve is closed. Restricted to stretch,
A forklift in which the restriction of the stroke of the drive cylinder and the caster cylinder is released when the switching valve is opened.   The forklift according to claim 1, wherein the stroke limiting mechanism includes a stroke adjusting unit that adjusts the moving range of the piston to adjust the stroke amount.

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