JPH0798493B2 - Four-wheel steering vehicle - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a four-wheel steering vehicle capable of switching between a four-wheel steering mode in which front and rear wheels are simultaneously steered and a two-wheel steering mode in which only front wheels or rear wheels are steered.

[0002]

2. Description of the Related Art In a work vehicle such as a wheel crane or a wheel type hydraulic excavator, a four-wheel steering mode in which front and rear wheels can be simultaneously steered in order to improve a narrow turn at a work site and improve running performance in a narrow place For safety, the two-wheel steering mode in which only one of the front and rear wheels (usually the front wheels) can be steered is selected.

In this two-wheel steering mode,
The non-steered wheels (hereinafter referred to as non-steered wheels) are locked in a neutral state by a lock device so that the unsteered wheels do not move during traveling.

Conventionally, in such a four-wheel steering vehicle, as the locking means, a knuckle arm in a neutral state of a non-steering wheel includes a lock pin (manual insertion / removal method and an automatic extraction / removal method using a hydraulic or pneumatic cylinder). There is a means of fixing to the housing of the axle.

[0005]

However, according to such a locking means, the pin holes of both the knuckle arm and the housing are not completely aligned with each other in the manual system, and the lock pin and the pin hole of the knuckle arm are not completely aligned in the automatic system. Since it is impossible to insert the lock pin, it takes time to align the pin hole, and in the automatic method, there is a problem that the pin operation is performed in a mismatched state and the lock device parts such as the pin are damaged.

In the case of the automatic system, there is a system in which the neutral detection of the non-steered wheels is performed by a limit switch or the like, but since there is a detection error by any means, the above problem cannot be fundamentally solved. Further, if the pin hole is formed to be larger than the lock pin, play occurs in the lock pin and the non-steered wheels move during traveling, so that the intended purpose is not achieved.

Therefore, the present invention eliminates the problems caused by the lock pin system, makes it easy to lock the non-steering wheels in the two-wheel steering mode, and does not damage the lock device parts. A four-wheel steering vehicle capable of obtaining a reliable locked state.

[0008]

According to the invention of claim 1, the front wheels and the rear wheels are steered by front and rear wheel steering drive mechanisms each having a steering cylinder.
A four-wheel steering mode in which the front and rear steering cylinders are both controlled by a mode switching valve to steer the front and rear wheels at the same time, and one of the front and rear steering drive mechanisms is deactivated and the front wheels or In a four-wheel steering vehicle configured to be switched to a two-wheel steering mode in which only the rear wheels can be steered, a steering drive mechanism that stops operating in the two-wheel steering mode is operated during steering among the constituent members of the mechanism. A lock device for restraining the member at a position in a wheel neutral state by a frictional force is provided.

According to a second aspect of the present invention, in the structure of the first aspect, the lock device includes a pair of friction members that face the knuckle arm in a wheel neutral state from both sides in a direction perpendicular to the rotation direction of the arm. The lock cylinder is operated between a lock position where the friction members are pressed against the knuckle arm to restrain the arms and a lock release position where the restraint is released.

On the other hand, according to the invention of claim 3, in the structure of claim 1, a cylindrical lock sleeve which is elastically expandable and contractible in the radial direction is provided on the outer circumference of the piston rod in the steering cylinder. Thus, the locking device is configured in such a manner that the piston rod is provided in a state in which it can be deformed into a contracted state in which the stroke cannot be operated, and an expanded state in which the constraint is released.

[0011]

According to the above construction, since the operating member of the steering drive mechanism on the non-steering side is neutrally locked by the frictional force, troublesome work such as alignment of the pin holes or the position of the lock pin and the pin hole as in the conventional lock pin system is performed. Is unnecessary, and there is no risk of damage to the lock device components due to the displacement of the position.

Moreover, the locking force is only required to prevent the non-steered wheels from moving, and this force can be sufficiently secured by friction, so that a reliable locked state can be obtained.

Further, according to the structure of claim 2 in which the knuckle arm is restrained by the pair of friction members, the position of the lock device can be relatively freely selected in the peripheral portion of the knuckle arm, so that the lock device is limited in space. It can be installed in the most suitable position inside, which is advantageous in design.

On the other hand, according to the structure of claim 3 in which the piston rod of the steering cylinder is restrained by the lock sleeve, the structure of the lock device is simple, it is hard to break down, and the reliability of the lock operation is high.

[0015]

Embodiments of the present invention will be described with reference to the drawings.

First Embodiment (See FIGS. 1 to 5) In FIG. 1, 1 is a vehicle body frame, 2 is a front axle, 3 is a rear axle, 4 and 4 are front wheels, and 5 and 5 are rear wheels. The front wheels 4, 4 and the rear wheels 5, 5 are connected to the front wheel steering cylinders 6, 6 and the rear wheel steering cylinders 7, 7 for the front wheel knuckle arms 8, 8, the rear wheel knuckle arms 9, 8, respectively.
Steered via 9.

On the other hand, in FIG. 2, the steering cylinder 6,
7 shows a hydraulic circuit including a control system of No. 7. In the figure, 10 is a mode switching valve (electromagnetic switching valve) for controlling the operation of the front and rear wheel steering cylinders 6, 7.

This mode switching valve 10 is operated by switching a mode selection switch (not shown), and the neutral front wheel steering mode position a and the four-wheel steering mode positions b and c on both sides (the front and rear wheels 4 and 5 are reversed at the same time). In the clamp mode in which the front and rear wheels 4 and 5 are simultaneously steered in the same direction, the clamp mode is switched to operate, and the pressure from the pump P is set in the four-wheel tearing mode positions B and C. Oil is simultaneously supplied to the front and rear steering cylinders 6 and 7, and in the front wheel steering mode position a, the supply of pressure oil to the rear steering cylinder 7 is stopped and only the front wheels 6 can be steered.

Reference numeral 11 is a steering handle, and reference numeral 12 is a steering operation valve for controlling the passage amount and the flow direction of the pressure oil from the pump P by operating the steering handle 11.

Further, in the pump circuit, a lock cylinder 1 of the lock device is provided via a lock switching valve (electromagnetic switching valve) 13.
4 is connected.

The lock cylinder 14 is urged in the extension direction by the spring 15, and when the front wheel steering mode is selected by the mode selection switch, the lock switching valve 13 switches from the position a to the position b. Pressure oil is supplied to the reduction side oil chamber to perform reduction operation.

When the lock cylinder 14 is contracted, the disc brake type lock mechanism 17 is operated via the link mechanism 16 shown in FIGS.
One knuckle arm 9 of 5 is restrained in the neutral position, and the rear wheels 5, 5 are neutrally locked.

The structure of the lock device including the link mechanism 16 and the lock mechanism 17 will be described with reference to FIGS.

A knuckle arm 9 of one rear wheel 7 is integrally provided with a lock arm 18, and a rear axle 3
Locking mechanism 1 via bracket 19 to (housing)
7 is provided.

The lock mechanism 17 includes a pair of friction members 20 and 21 which are vertically opposed to each other and both friction members 20 and 2.
1, a pin 22 inserted between the two, an operating lever 23 rotatably attached to the upper friction member 20 about a horizontal axis, and a return spring 24 provided between the operating lever 23 and the upper friction member 20. The lock arm 18 is located between the friction members 20 and 21 in the neutral state of the rear wheel 5.

Both friction members 20, 21 have a pad 2 on the inner surface.
0a, 21a and the pads 20a, 21a can rotate in a direction in which the pads 20a, 21a approach and separate from each other.
Installed on.

The lower end of the pin 22 is connected to the lower friction member 21 and the upper end thereof is connected to the operating lever 23. When the pin 22 is pulled up by the rotation of the operating lever 23 as shown in FIG. The lock arms 18 move in the direction in which the members 20 and 21 approach each other, and the lock arms 18 move to the pads 20a and
It is sandwiched between a. As a result, the lock arm 18,
That is, the knuckle arm 9 is restrained in the neutral position and the rear wheel 5 is locked so that it cannot be steered.

The link mechanism 16 is driven by the lock cylinder 14 and rotates about a horizontal axis.
The second link 26 transmits the rotational force of the first link 25 to the operation lever 23 of the lock mechanism 17, and when the lock cylinder 14 is contracted, the operation lever 23 moves from the state of FIG. When the lock mechanism 17 is driven to the state of No. 5, the lock mechanism 17 enters the locked state.

In this way, when switching to the front wheel steering mode, the knuckle arm 9 (lock arm 18) is sandwiched between the friction members 20 and 21 and restrained by the friction force.
As a result, since the rear wheels 5, 5 are neutrally locked, compared to the conventional lock pin system, (a) the troublesome pin hole alignment work becomes unnecessary, and the rear wheels 5, 5
It is possible to easily and quickly lock 5 by setting the mode selection switch to the front wheel steering mode after setting 5 to the neutral state.

(B) As in the case of the automatic system in which the lock pin is driven by a cylinder, the lock pin is driven to be locked in a state where the lock pin is not aligned and the lock device parts are damaged, or the plating of the lock pin is peeled off and rusted. There is no fear of occurrence.

Moreover, the rear wheel locking force in the front wheel steering mode may be large enough to withstand the side force acting on the rear wheels 5 and 5 during traveling, and this force locks the friction members 20 and 21. Since it can be sufficiently secured by the frictional force of the arm 18, a reliable locked state can be obtained.

The neutral state of the rear wheel 5 may be detected by a limit switch or the like, and the lock cylinder 14 may be locked by ANDing the detection signal and the front wheel steering mode selection signal of the mode selection switch.

Second Embodiment (see FIGS. 6 to 8) Only differences from the first embodiment will be described.

In the second embodiment, a known mechanical lock mechanism called a bare lock is adopted as the lock device.

That is, in one rear wheel steering cylinder 7, a metal lock sleeve 27 which is elastically expandable and contractible in the radial direction is axially extended to the rod-side end cap 7a of the cylinder tube, and It is provided integrally with the piston rod 7b while being fitted onto the piston rod 7b.

This lock sleeve 27 is in a tightly fitted state with respect to the rod 7b in the non-pressure state to prevent the stroke movement of the rod 7b (the state shown in FIG. 7), and the hydraulic pressure is supplied from the hydraulic port 28 provided in the end cap 7a. When the rod 7b is supplied, the rod 7b is released in the radial direction as shown in FIG. Reference numeral 29 is a seal member.

Therefore, when the four-wheel steering mode is selected, hydraulic pressure is supplied to the lock sleeve 27, and hydraulic pressure is supplied when switching to the front wheel steering mode, whereby the rear wheel steering cylinder 7 is restrained in the neutral position. The rear wheels 5, 5 can be neutrally locked.

According to this structure, basically, like the first embodiment, the lock is performed by the frictional force, so that the same effect as that of the first embodiment can be obtained.

Moreover, since the steering cylinder 7 itself is locked in a simple structure, the structure is far more than the structure in which the lock cylinder 14, the link mechanism 16 and the lock mechanism 17 are combined as in the first embodiment. It is simple, has no risk of failure, and is highly reliable in operation.

By the way, in this bare lock mechanism,
The lock sleeve 27 may have a double structure so that the lock action is performed at the time of pressurization.

In the first and second embodiments, only one rear wheel 5 is locked, but both left and right wheels may be locked.

Further, depending on the vehicle, the front wheels 4 may be locked instead of the rear wheels 5 in the two-wheel steering mode.

[0043]

As described above, according to the present invention, since the operating member of the steering drive mechanism on the non-steering side is neutrally locked by the frictional force in the two-wheel steering mode, the pin like the conventional lock pin system is used. The troublesome work of aligning the holes or the position of the lock pin and the pin hole is not necessary, and the risk of damage to the lock device components due to the displacement of the positions is eliminated.

Moreover, the lock force may be large enough to prevent the non-steered wheels from moving freely (withstand the side force acting on the non-steered wheels), and this force can be sufficiently secured by friction. It is possible to obtain a reliable locked state.

Further, according to the invention of claim 2 in which the knuckle arm is restrained by the pair of friction members, the position of the lock device can be relatively freely selected in the peripheral portion of the knuckle arm, so that the lock device is limited in space. It can be installed in the most suitable position inside, which is advantageous in design.

On the other hand, according to the invention of claim 3 in which the piston rod of the steering cylinder is restrained by the lock sleeve, the structure of the lock device is simple, it is hard to break down, and the reliability of the lock operation is high.

[Brief description of drawings]

FIG. 1 is a partially cutaway plan view of a vehicle body showing a first embodiment of the present invention.

FIG. 2 is a hydraulic circuit configuration diagram of a steering system and a lock system in the same embodiment.

FIG. 3 is a partially enlarged view of FIG.

FIG. 4 is a sectional view taken along the line EE of FIG.

FIG. 5 is a view corresponding to FIG. 4 showing a rear wheel lock state in a front wheel steering mode in the embodiment.

FIG. 6 is a view, corresponding to FIG. 3, showing a second embodiment of the present invention.

FIG. 7 is a partially enlarged sectional view of the steering cylinder showing a locked state in the embodiment.

FIG. 8 is a view corresponding to FIG. 7 showing an unlocked state in the embodiment.

[Explanation of symbols]

 4 front wheels 5 rear wheels (non-steered wheels in the two-wheel steering mode) 6 front wheel steering cylinder 7 rear wheel steering cylinder 8 front wheel knuckle arm 9 rear wheel knuckle arm 10 mode switching valve 14 lock cylinder 16 lock mechanism 16 same link mechanism 17 same lock Mechanism 18 Locking arm of rear knuckle arm 20,21 Pair of friction members 27 Locking sleeve of locking device

Claims (3)

[Claims] 1. A front wheel and a rear wheel are steered by a front wheel and a rear wheel steering drive mechanism having a steering cylinder, respectively, and both the front wheel and the rear wheel steering cylinders are controlled by a mode switching valve so that the front wheel and the rear wheel are simultaneously operated. A four-wheel steering mode configured to be switched between a steered four-wheel steering mode and a two-wheel steering mode in which one of the front and rear wheel steering drive mechanisms is deactivated and only the front or rear wheels can be steered. In a vehicle, a steering drive mechanism that is deactivated in the two-wheel steering mode is provided with a lock device that constrains a member that operates during steering among the constituent members of the mechanism to a position in a wheel neutral state by a frictional force. A characteristic four-wheel steering vehicle. 2. The four-wheel steering vehicle according to claim 1, wherein the lock device includes a pair of friction members facing the knuckle arm from both sides in a direction perpendicular to the rotation direction of the knuckle arm in a wheel neutral state, and both of them. A four-wheel steering vehicle comprising: a lock cylinder that is operated between a lock position for pressing a friction member against a knuckle arm to restrain the arm and a lock release position for releasing the restraint. 3. The four-wheel steering vehicle according to claim 1, wherein a cylindrical lock sleeve elastically expandable and contractible in the radial direction is provided on the outer circumference of the piston rod of the steering cylinder by supplying and discharging the fluid pressure to the piston. A four-wheel steering vehicle characterized in that a lock device is provided so as to be provided in a state in which the rod can be deformed into a contracted state in which the stroke is inoperable and is constrained to an expanded state in which the constraint is released.