JPH0577549B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in a front and rear wheel steering device for a vehicle, which is configured so that the rear wheels are also steered following the steering of the front wheels.

[Conventional technology]

In the case of work vehicles such as trucks, the rear wheels are also steered to follow the front wheels in order to quickly and efficiently turn when driving at low speeds and slant to change course. A wheel steering system has been proposed.

For example, according to a proposal in Japanese Patent Application Laid-open No. 59-143769, the device has a controller and is equipped with various sensors such as a vehicle speed sensor and a steering wheel operation angle sensor, and the detection signals from the various sensors are The actuation signals that are input to the controller and processed by the controller are output to various valves, and the valve control enables steering of the rear wheels when the vehicle is running at low speed.

Therefore, desired rear wheel steering can be achieved by equipping the vehicle with a variety of sensors and a controller with processing capability for adjusting the operation of various valves over many branches.

[Problem that the invention seeks to solve]

However, the conventional proposal has the disadvantage of increasing the cost of the device itself.

That is, in the above conventional proposal, the rear wheel steering that follows the front wheel steering when the vehicle is running at low speed is
Although it must always be reproduced as desired, there is a risk that the steering situation of the rear wheels will change due to changes in the characteristics of the valve, and there is a risk that this risk will not occur at all. In order to prevent this, further maintenance of the controller is required, which inconveniently increases the cost of the device.

SUMMARY OF THE INVENTION In view of the above-mentioned circumstances, it is an object of the present invention to provide a new front and rear wheel steering device for a vehicle that does not increase costs.

[Means for solving problems]

In order to solve the above-mentioned problems, the configuration of the present invention is applied to a vehicle configured to supply hydraulic oil from an oil supply mechanism to a rear wheel cylinder so that the rear wheels can be steered to follow the front wheels. In a front and rear wheel steering system, the oil supply mechanism enables the supply of hydraulic oil to the rear wheel cylinder in conjunction with the rotation of the steering wheel rotation shaft for steering the front wheels, and also when the vehicle speed exceeds a set vehicle speed. Alternatively, the oil supply mechanism is formed so as to be insulated from the rotation of the handle rotation shaft by manual operation.

〔Example〕

The present invention will be described below based on illustrated embodiments.

FIG. 1 shows a front and rear wheel steering device for a vehicle according to an embodiment of the present invention, which has a power steering mechanism PS on the front wheel Tf side and a rear wheel steering device on the rear wheel Tr side. has a cylinder Cr, and the power steering mechanism PS
The oil supply mechanism 1 is formed to be selectively interlocked with the operation of the oil supply mechanism 1.

The above power steering mechanism PS includes front wheel Tf
A pitman arm a that swings when the steering handle is operated is connected to the pitman arm a, and a drag rod r ₁ is also connected to the pitman arm a, and the movement of the drag rod r ₁ causes the drag rod r 1 to rotate at both ends of the front wheel axle F. The provided front wheel Tr is formed to turn in a predetermined manner. In addition, the power steering mechanism PS mentioned above has a tank when it is activated.
The hydraulic oil from T ₀ flows into the front wheel swing pump Pf and is returned to the tank T ₀ .

During its operation, the oil supply mechanism 1 supplies hydraulic oil from the rear wheel swing pump Pr to the main supply/discharge path L ₁ or
It is configured to be supplied to the rear wheel cylinder Cr via _L2 and returned to the tank _T0 , and its operation is selectively performed with the rotational operation of the handle H performed to operate the power steering mechanism PS. It is designed to be performed in conjunction with each other.

That is, the base end is connected to the power steering mechanism PS.
A gear G is formed on the handle rotation shaft h that engages with the gear G, and a gear 10 that enables the operation of the oil supply mechanism 1 is selectively engaged with the gear G by, for example, manual operation. It is formed in
In this embodiment, the oil supply mechanism 1 is configured to be movable by swinging of an operating arm 11 connected to the oil supply mechanism 1. Note that the structure of the oil supply mechanism 1 is not particularly specified as long as it can supply a desired amount of hydraulic oil to the rear wheel cylinder Cr in conjunction with the operation of the handle H, but in this embodiment It consists of a fully hydraulic power steering system called HPS.

The above-mentioned rear wheel cylinder Cr is formed into a so-called double rod type, in which both ends of the rod body protruding from the cylinder body are connected to a rod _r2 connected to the rear wheel Tr, and is not shown in the figure. However, it is possible to supply hydraulic oil from the oil supply mechanism 1 to the two oil chambers partitioned on the left and right inside the cylinder body, or to operate the oil supply mechanism 1 from the two oil chambers. It is configured to allow oil to drain. In addition, the above rear wheel cylinder Cr
In this embodiment, the rod is of a so-called double rod type, but it may be of a single rod type instead.

As described above, if hydraulic oil is supplied to the rear wheel cylinder Cr, the rear wheel Tr can be steered freely left and right, but the rear wheel Tr can be returned to the neutral position and maintained. To do this, we will use the following rear wheel centering mechanism 2.

That is, as shown in FIG. 1, the rear wheel centering mechanism 2 is disposed adjacent to the left and right rear wheels Tr, and as shown in FIG.
Appropriately, the housing 20 includes a spring 21 and a push rod 22 energized by the spring 21.
has a piston-like base 23 that slides within the housing 20, and has an air chamber 24 defined by the piston-like base 23. The tip of the push rod 22 is
When the pressure inside the air chamber 24 is released, the rear wheel
It is formed so as to be in contact with the side surface of a knuckle arm N extending parallel to the neutral direction of the Tr. That is, in the present embodiment, the knuckle arm N has a guide rod n protruding in a direction perpendicular to the extending direction of the knuckle arm N, that is, in a direction parallel to the rear wheel axle R (see FIG. 1). The guide rod n is inserted through the central axis of the push rod 22, thereby allowing the push rod 22 to
will slide along the guide rod n.

Therefore, when pressurized air is supplied into the air chamber 24 from the external air tank Ta (see FIG. 1) through the supply/discharge path La and the port 25, the piston-shaped base 23 is affected by the repulsive force of the spring 21. The push rod 22 moves backward inside the housing 20, and at that time, the tip of the push rod 22 is unseated from the side surface of the knuckle arm N, and the knuckle arm N swings upward in the circumferential direction with the center at the bottom in FIG. In other words, the rear wheel Tr can be steered.

Then, when the supply of pressurized air is released, the push rod 22 is slid to the right in FIG. , the rocking of the knuckle arm N,
In other words, steering of the rear wheel Tr is stopped.
At this time, a gap δ is formed between the piston-like base 23 of the push rod 22 and the housing 20, that is, between the sliding direction of the push rod 22, and the tip of the push rod 22 is in contact with the side surface of the knuckle arm N. Before the piston-like base 2
3 and the housing 20 are brought into contact with each other, so that the so-called steer lock for the knuckle arm N will not become incomplete.

Note that one end of the housing 20 is connected to the other part b.
The other end of the housing 20, that is, the side on which the push rod 22 is disposed, can swing freely around the pivot portion (for example, the vehicle body).

The air chamber 24 of the rear wheel centering mechanism 2 is communicated with an external air tank Ta. That is,
As shown in FIG. 1, the vehicle is equipped with an air tank Ta for, for example, an exhaust brake (not shown). Pressurized air is supplied into the air chamber 24 through a blowout prevention valve V and a switching valve 3, which will be described later. If there is a failure in either the La part or the 3rd part of the switching valve, the air tank
It is arranged to prevent pressure air from being blown out unnecessarily from Ta.

As shown in FIG. 1, the switching valve 3 has a supply/discharge path La that allows pressurized air to flow from an air tank Ta that is a source of pressurized air to the rear wheel centering mechanism 2.
a pneumatic valve part 3a that enables communication and isolation of the oil supply mechanism 1, and a bypass of the hydraulic oil in the main supply and discharge passages L1 and _L2 that allows the flow of hydraulic oil from the oil supply mechanism ₁ to the rear wheel cylinder Cr. Hydraulic valve section 3b that is prohibited
The pneumatic valve portion 3a and the hydraulic valve portion 3b are integrally formed.

That is, it is assumed that the switching valve 3 has a spool 31 within a housing 30, and a spring 32 disposed between the spool 31 and the housing 30 is in contact with one end of the spool 31. A rod 33 is provided at the other end of the spool 31 to protrude in the axial direction of the spool 31. When the actuating arm 11 is raised up and comes into contact with the rod 33, the spool 31 overcomes the repulsive force of the spring 32 and moves into the housing 33.
0, regulates the air flow by land portions 31a and 31b, and supplies pressurized air from the air tank Ta to the rear wheel centering mechanism 2.
The main supply/discharge path is formed by the land portions 31c and 31d.
The bypass state of L ₁ and L ₂ is disabled, and the oil supply mechanism 1
Hydraulic oil is supplied to and discharged from the rear wheel cylinder Cr.

Note that when the switching valve 3 is not activated, the air chamber 2 of the rear wheel centering mechanism 2 is closed by the pneumatic valve portion 3a.
The pressurized air in 4 is passed through the pneumatic valve part 3a to the throttle t.
The oil is gradually discharged to the outside, and the main supply/discharge path is
L ₁ and L ₂ are in communication, and one main supply/discharge path
The hydraulic oil from L ₁ (or L ₂ ) is bypassed to the other main oil supply path L ₂ (or L ₁ ), and cannot be supplied to the rear wheel cylinder Cr.

In the present invention, the operating state of the switching valve 3 is determined by the operating arm 1 as shown in FIG.
1, and maintenance of the above-mentioned operating state is made possible by a stopper device 4 shown in FIG. 4 in the present invention.

That is, the actuating arm 11 is provided with a protruding guide portion 12 (see FIG. 3).
In the pin hole 12a (see Fig. 3),
A pin 41, which is inserted into a yoke 40 formed to guide the guide portion 12 inside, is inserted through the yoke 40 so as to be freely removable and removable. And the above pin 4
1 is biased in the so-called pulling direction by a spring 42, and is slid in the so-called insertion direction by energizing a solenoid 43 disposed near the pin 41. It is formed.

The solenoid 43 has a manual switch Sm in the ON state and an automatic switch Sm in the ON state.
When the operating arm 11 is raised, the bracket 1
The magnet is formed so that the above-mentioned excitation is performed when it is brought into the ON state by contact of the magnets 2 and 2. Furthermore, the excitation of the solenoid 43 is configured such that it is released when the speed of the vehicle exceeds a certain value (for example, 35 km/h) on the speedometer M. , it is also supposed to be canceled by turning off the manual switch Sm. When the solenoid 43 is de-energized, the pin 41 is activated by the spring 4.
Due to the repulsive force of 2, it moves backward in the so-called pulling direction, releases the engagement with the bracket 12, and swings the operating arm 11, that is, the gear G of the handle rotation axis h of the gear 10 in the oil supply mechanism 1. This will cause the mesh to be released.

Therefore, in the device of the present invention, when operating the front wheel T, if the operating arm 11 in the refueling mechanism 1 is raised and its operating gear 10 is meshed with the gear G of the handle rotation axis h, on the one hand, Switching valve 3
is activated, the pneumatic valve part 3a releases the rear wheel lock by the rear wheel centering mechanism 2, and on the other hand, the desired amount of hydraulic oil from the oil supply mechanism 1 is metered by the oil supply mechanism 1. The hydraulic oil thus generated is supplied to the rear wheel cylinder Cr, and desired rear wheel steering becomes possible.

Then, in the above operating state, the manual switch
If Sm is kept in the ON state, the solenoid 43 in the stopper device 4 is energized and the pin 41 is inserted into the pin hole 12a of the bracket 12 of the manual arm 11, that is, the manual arm 11 is maintained in the upright state. It will be done.

Also, when you do not wish to steer the rear wheel Tr,
For example, when the vehicle shifts to high-speed driving, the excitation to the solenoid 43 is automatically released, and the pin 41 is pulled out from the pin hole 12a of the bracket 12 by the repulsive force of the spring 42. , the manual arm 11 falls down and the gear 1
0, the engagement of the handle rotation axis h with the gear G is released, the oil supply mechanism 1 is inactive, and the rear wheel cylinder
It becomes impossible to steer the rear wheel Tr using Cr.

At this time, the switching valve 3 also becomes inoperative, the pressure from the rear wheel centering mechanism 2 is discharged to the outside, and the push rod 22 is seated on the knuckle arm N by the repulsive force of the spring 21, so that the so-called rear wheel Tr steering lock becomes possible.

〔Effect of the invention〕

As described above, according to the present invention, when a work vehicle such as a truck turns or travels diagonally while traveling at a constant speed,
Not only is it possible to steer the rear wheels to follow the front wheels, but when the vehicle is traveling at a speed higher than the set speed, steering of the rear wheels is automatically stopped. This has the advantage of allowing the vehicle to run stably, that is, to run at high speed.

Further, according to the present invention, even when the vehicle is traveling at a low speed lower than the set vehicle speed, the steering of the rear wheels can be stopped by manual operation. There is an advantage in that it is possible to realize stable running of the vehicle by completely stopping steering of the rear wheels at the request of the person or depending on the condition of the driving road surface such as a snowy road.

[Brief explanation of drawings]

FIG. 1 is a partial cross-sectional circuit diagram showing a front and rear wheel steering device according to an embodiment of the present invention, FIG. 2 is a cross-sectional view showing a rear wheel neutralization device according to the present invention, and FIG. FIG. 4 is a schematic diagram showing a swinging state, and FIG. 4 is a schematic partial cross-sectional view showing a stopper device that maintains the operating arm in an upright state. DESCRIPTION OF SYMBOLS 1... Oil supply mechanism, 2... Rear wheel centering mechanism, 3... Switching valve, 3a... Pneumatic valve part, 3b...
Hydraulic valve section, 4... Stopper device, Cr... Rear wheel cylinder, H... Handle, h... Handle rotating shaft, G, 10... Gear, L ₁ , L ₂ ... Main supply/discharge path, La... ...Supply/exhaust path, PS...power steering mechanism, Tf...front wheel, Tr...rear wheel.

Claims (1)

[Claims] 1. In a front and rear wheel steering device for a vehicle configured to supply hydraulic oil from an oil supply mechanism to a rear wheel cylinder to enable steering of the rear wheels that follow the front wheels, the oil supply mechanism supplies hydraulic oil to the front wheels. The oil supply mechanism enables the supply of hydraulic oil to the rear wheel cylinders in conjunction with the rotation of the handle rotation shaft, and when the vehicle speed exceeds the set vehicle speed or by manual operation, the oil supply mechanism A front and rear wheel steering device for a vehicle, characterized in that it is formed so as to be insulated from rotation.