JP2833278B2 - Rear wheel steering device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rear wheel steering system,
More specifically, the present invention relates to a rear wheel steering device used for a forklift truck.

[0002]

2. Description of the Related Art As a conventional rear wheel steering device, for example, FIG.
9 to 11 are known. 9 to 1
The rear wheel steering device shown in FIG. 1 is a so-called semi-integral type steering device, which is a general example of a four-wheel type.
Reference numeral 1 denotes a rear axle, and a knuckle spindle 3 is connected to the rear axle 1 via a kingpin 2.
A rear wheel 4 is supported on the knuckle spindle 3. Further, a bell crank 5 is rotatably supported on the rear axle 1, and a steering operation force is transmitted to the bell crank 5 via a drag link 6 and is rotated about a bell crank shaft 7. Due to the rotation of the bell crank 5, the king pin 2 is rotated via the tie rod 8, and the rear wheel 4 is rotated about the axis of the king pin 2, that is, the turning axis L.
The turning axis L is in the same vertical plane as the axis of the rear wheel 4 and extends in the vehicle width direction. Therefore, the caster amount indicating the distance in the vehicle front-rear direction between the intersection of the turning axis L and the ground and the contact point of the rear wheel 4 is set to zero.

[0003] On the other hand, the rear wheel steering apparatus of the three-wheel type, are known those described in JP Sho 59-117881, it is shown as in Figure 12. In FIG. 12 , reference numeral 11 denotes a rotatable steer axle unit, and the steer axle unit 11 supports a rear wheel 12. The axis of the steering axle unit 11, that is, the turning axis, extends in the vertical direction and passes through the ground point of the rear wheel 12. Therefore, the caster amount is set to zero as described above.

[0004]

However, in these conventional rear wheel steering devices, the caster amount is set to zero, so that the steering force is applied to the steering wheel when the vehicle moves forward, so that the operability of driving is improved. However, there was a problem such that the number of samples decreased. That is, in the case of four wheels, as shown in FIG. 13 , due to the centrifugal force F generated by turning, the contact load on the outside of the rear wheel increases and the contact load on the inside decreases. For this reason, the rolling force T1 of the outer rear wheel 4 generated by the running resistance increases, and the restoring force T2 of the inner rear wheel 4 decreases, and as a result, the force in the rolling direction is transmitted to the steering wheel as a whole. Will be. A point A in FIG. 13 indicates an intersection point between the turning axis L and the ground.

In the case of three wheels, as shown in FIG.
The center Y of the ground contact load of the rear wheel 12 shifts outward due to the centrifugal force F generated by the turning. For this reason, a rolling force T1 is generated on the rear wheels 12 when the vehicle is moving forward due to running rolling resistance. FIG.
Point A of 4 also indicates the position of the intersection between the turning axis and the ground. Further, in any of the above cases, the restoring force does not act on the steering wheel when the vehicle is moving forward, and the entanglement force acts on the steering wheel. Therefore, for a driver accustomed to driving an automobile, the operability is uncomfortable, and Operability will be reduced. In addition, straightness is reduced, and high-speed traveling becomes difficult. Therefore, operability is poor for an inexperienced driver, and it becomes a major obstacle when recruiting elderly or female drivers to make up for a shortage of work and to make up for the labor shortage.

In any of the above cases, a slight restoring force acts on the steering wheel during forward movement. In the case of an all-hydraulic power steering, a non-road reaction type power steering unit has been proposed for the power steering unit from the viewpoint of preventing the above-described entrainment when the vehicle is moving forward. There is no restoring effect, and the operability of driving is reduced in any case. Further, conventionally, only the so-called king pin angle is provided (to reduce the scrub radius and make it less susceptible to disturbance), and the caster amount e is zero as described above. In the case of all-hydraulic power steering, some do not even have a kingpin angle.

[0007] Therefore, an object of the present invention is to improve the operability of driving by setting the intersection of the turning axis and the ground behind the vehicle with respect to the ground point of the rear wheels.

[0008]

In order to solve the above-mentioned problems, the invention according to claim 1 is provided with a swing shaft on a vehicle body.
A steering axle swingably supported through
Around the turning axis of the king pin provided on the left and right ends of the axle
Rear wheel steering by turning the rear wheel
In the device, the swing shaft is connected to the steering axle.
The upper side of the kingpin is located in front of the vehicle
In a tilting direction, the kingpin is inclined against the vertical direction
It is characterized by having.

Further , the invention according to claim 2 has the above configuration.
To be able to rotate around a predetermined axis.
Steering axle supported by steering axle
To apply steering force to the rear wheel via the rod
A bell crank is provided, and the predetermined axis is defined as the turning axis.
Install the bell crank on the steering axle so that it is almost parallel.
It is characterized by being attached.

The invention according to claim 3 is the invention according to claim 1.
In addition to the above configuration, the turning axis is orthogonal to the vehicle width direction.
It is characterized by.

[0011]

According to the present invention, the swing with respect to the steer axle is performed.
Set the caster amount by tilting the shaft.
The steering wheel is
Holes can be made orthogonal to each other,
Workability can be significantly improved. Also the kingpin
Even if the angle is zero, straight running performance can be maintained
In comparison with the conventional one with a kingpin angle,
Work can be facilitated.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. Figure
1 to 7 show an embodiment of a rear wheel steering device according to the present invention.
It is a figure and is the example applied to the four-wheeled vehicle. First, the composition
I will tell.

1 to 7, reference numeral 31 denotes a rear wheel, and the rear wheel 31 is turned around the turning axis L, that is, about the axis of the king pin 32, and is steered. Specifically, the king pin 32 is inserted into a knuckle spindle 33, and the rear wheel 31 is supported by the knuckle spindle 33. Also the kingpin
Numeral 32 is rotatably supported by a steer axle (rear axle) 34, and a knuckle spindle 33 is connected to a tie rod 35 (a connecting portion is not shown). The tie rod 35 indicated by a virtual line indicates the position on the opposite rear wheel. The tie rod 35 is connected to a bell crank 36, and the bell crank 36 is supported by a steering axle 34 so as to be able to rotate around a bell crank shaft 37. The bell crank 36 is rotated via a rod 50 by operating a handle (not shown), and the operating force of the handle rotates the knuckle spindle 33 around the king pin 32 via the bell crank 36 and the tie rod 35 to steer the rear wheel 31. I do. Since the left and right tie rods 35 are connected to the upper and lower sides of the bell crank 36, respectively, the connection between the tie rod 35 and the knuckle spindle 33 is upside down. Are symmetric.

The contact point of the rear wheel 31 is defined as a first point A ₁ , and the turning axis L
And when an intersection between a second point A ₂ with the ground, the second point A ₂ as shown in FIG. 3 is positioned rearward than the first point A _1. Here, μ, h, s ₂ and a are: μ: rolling resistance coefficient of the rear wheel 31 h: height from the ground of the centrifugal force applied to the steering axle 34 from the vehicle body side (roll center height) S _2: the first point a ₁ and the distance of the second point a ₂ in the vehicle width direction (scrub radius) a: when the tread of the rear wheels 31, e, μ, h, s 2 and a are, e> 2μ · h · s ₂ / a (1) is satisfied.

[0015] To place the second point A2 rearward of the vehicle than the first point A _1, in the present embodiment, as shown in FIG N3, in the direction of the upper side of換向axis L falls down the front of the vehicle, conversion Direction axis L
Are inclined with respect to the vertical direction. In order to arrange the turning axis L in this manner, in this embodiment, the steering axle 34 is provided.
Is attached to the vehicle body frame 38 while being inclined with respect to the vertical direction. Specifically, the swing shaft 39 to be attached to the steering axle 34 is attached to the box body 34a of the steering axle 34.
The steering axle 34 is attached to the vehicle body frame 38 so that the swing shaft 39 is in a horizontal direction. That is, by attaching the box body 34a of the steering axle 34 to the vehicle body while being inclined with respect to the vertical direction,
The king pin 32 is inclined with respect to the vertical direction so that the upper side of the king pin 32 falls forward of the vehicle.

The bell crank 36 is attached to the steering axle 34 such that the axis K of the bell crank shaft 37, which is the center of rotation of the bell crank 36, is also substantially parallel to the turning axis L. On the other hand, the turning axis L is orthogonal to the vehicle width direction,
The so-called kingpin angle is reduced to zero and only a negative caster angle is provided by eliminating the inclination component of the kingpin 32 in the vehicle width direction.

Here, a method for assembling the box body 34a of the steering axle 34 and the swing shaft 39 will be described. It is important that the coaxiality of the swing shaft 39 is ensured. After welding the member corresponding to the swing shaft 39 to the box 34a, there is no problem if the member is machined to form the swing shaft 39, but large equipment is required to rotate and cut such a large component. Will be needed. Therefore, it is desirable to provide a certain degree of accuracy by welding after machining in a single piece state.

First, as shown in FIG. 4, through-holes are formed in the swing shaft 39 and the box body 34a in a single piece state, and the swing shaft 39 is attached to the box body 34a in a state where the guide shaft 61 is passed through these through-holes. To weld. Note that a so-called pipe material may be used for the swing shaft 39. Also,
As shown in FIG. 5, the swing shaft 39 may be inserted into the through hole of the box 34a and welded.

Reference numerals 51 and 52 denote pipe members welded to the steering axle 34, 53 and 54 denote needle bearings, 55 and 56 denote seals, and 57 denotes a thrust ball bearing. In the present embodiment configured as described above, the following effects can be obtained. First, since the point second A ₂ is offset rearwardly from the first point A _1, as shown in FIG. 6, the reaction force P acting on the rear wheel with respect to the centrifugal force and the second point A Acts as _two rounds of torque, the direction of which is the restoration direction. This relationship holds both when the vehicle is moving forward and when the vehicle is moving backward.

Therefore, it is possible to prevent the rear wheel 31 from being caught up not only when the vehicle is moving backward but also when the vehicle is moving forward, and the operability of driving can be improved. Second, the above (1)
Since the expression is satisfied, it is possible to more reliably prevent the rear wheel 31 from being caught when the vehicle is moving forward, and it is possible to more reliably improve the operability of driving. Hereinafter, the principle will be described.

FIG. 7 shows a case where the turning radius R in which straightness becomes a problem is sufficiently large, and R >> a, b, c,
d and e. In this case, the second point A ₂ about the torque is produced by the road surface reaction force to the rear wheel 31. Assuming that the case of acting in the restoration direction is positive, the following is obtained. (B) a by centrifugal force _{(T c) f o = f} i = F · c / 2b ···· (2), T c = (f o + f i) e = F · c · e / b (restoring force) ... (3) (b) by the running resistance (T _r) vertical load on the rear wheel outside the W _o, if the inner and _{W i, W o = M ·} g · c / (2b) + F · h · c / (a · b) (4) Similarly, W _i = M · g · c / (2b) −F · h · c / (a · b) ··· ·· (5) _o the outside of the rolling resistance μ, and the inside of the rolling resistance and _{μ i, T r = -μ o} · W o · s 2 + μ i · W i · s 2 Tr = -2μ · F · h · c · s ₂ / (a · b) (entanglement force) (6) In order for the restoring force to act on the rear wheel 31 according to the equations (3) and (6), T _c + T _r > 0 ... (7) is required. That is, it is necessary that e> 2 μ · h · s ₂ / a (8) . Therefore, if the expression (8), that is, the expression (1) is satisfied, a restoring force can be reliably generated in the steering wheel when the vehicle advances.

Third, the kingpin 32 is orthogonal to the vehicle width direction, and the kingpin angle is necessarily zero. The kingpin angle is set to reduce the scrub radius to make it difficult for the steering wheel to be picked up by disturbance, but by setting the kingpin angle to zero, even if the scrub radius increases, the disturbance can be sufficiently canceled out By setting the caster amount e in such a way as to make it possible to cope with disturbances. Further, by forming the knuckle pindle 33 symmetrical with respect to the center line of the rear wheel, the knuckle spindle 33 can be shared by the left and right.

Fourth, since the king pin 32 and the bell crankshaft 37 are parallel, that is, the diverting axis L and the axis K are parallel, it is not necessary to change the angle of the work when drilling the steer axle 34. , Making production easier. Fifth, since the caster amount e is set by inclining the swing shaft 39 with respect to the box body 34a of the steering axle 34, the king pin 32 and the bell crankshaft 37 are provided on the upper and lower surfaces of the box pair 34a. Can be made orthogonal to each other, and workability in drilling holes can be significantly improved.

Sixth, since the bell crankshaft 37 and the left and right kingpins 32 are parallel to each other, the axial movement of each link point with respect to the shaft, that is, the vertical movement, can be eliminated, and only the movement in the rotational direction can be eliminated. Can be used. Therefore, the expensive ball joint conventionally required can be eliminated.

Seventh, since straight running performance can be maintained even when the kingpin angle is reduced to zero, machining can be facilitated as compared with the conventional one having a kingpin angle. Eighth, the pipe materials 51 and 52 are
Since the upper and lower plate portions 34b are welded to the inside, the kingpin hole can be finished in a welded state, and the plate portion 34b of the steer axle 34 and the pipe material 51,
By directly inserting the needle into 52, cost can be reduced and strength can be improved.

Although this embodiment is an example in which the invention is applied to a semi-integral type rear wheel steering device using a bell crank, it is also applicable to an all hydraulic type in which left and right tie rods are driven by hydraulic cylinders. it can. FIG.
Shows an example in which the plate portion 34a of the steer axle 34 is thickened and the upper pipe material is omitted. The one shown in this figure can also improve the operability of driving as described above.

[0027]

According to the first aspect of the present invention, steer is achieved.
By tilting the swing shaft with respect to the
The caster amount is set so that the steering axle
The kingpin hole can be orthogonal to the upper and lower surfaces.
Workability when drilling holes can be significantly improved.
Wear. In addition, even if the kingpin angle is set to zero, straight running performance is maintained.
So you can hold it with the traditional kingpin angle
Processing can be easier than
You.

Also, according to a second aspect of the present invention,
To the rear wheel through the rod by the steering operation force
A bell crank that gives wheel steering force is supported, and the
So that the rotation axis of the rank is substantially parallel to the conversion axis
Then, the kingpin angle is reduced to zero as described in claim 3.
Even if the scrub radius increases due to
Set the caster amount so that disturbance can be sufficiently canceled.
By setting, it is possible to cope with disturbance. I
The bell crankshaft and the left and right kingpins
Because of the parallelism, the axial movement of each link point with respect to the axis
That is, vertical movement can be eliminated,
A pinge that can only absorb movement in the turning direction
Can be used. Therefore, conventionally required
An expensive ball joint is possible to eliminate the need was
There is an effect that can be cut.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a main part of an embodiment of a rear wheel steering device according to the present invention.

FIG. 2 is a top view of the steering axle of FIG . 1;

FIG. 3 is a schematic side view of the rear wheel steering device in FIG. 1;
You.

FIG. 4 is a set of a steering axle and a swing shaft shown in FIG . 2;
FIG. 4 is a diagram for explaining a setting method.

FIG. 5 is a view for explaining another method of the assembling method of FIG . 4;
FIG.

FIG. 6 is an operation explanatory view of the rear wheel steering device in FIG . 1;
You.

FIG. 7 is an operation explanatory diagram for explaining FIG . 6 in more detail;
(A) is a schematic top view of the rear wheel steering device, and (b) is
It is the schematic rear view.

FIG. 8 is a schematic sectional view showing another embodiment of the embodiment of FIG . 1;
You.

FIG. 9 is a perspective view of a conventional rear wheel steering device.

10 is a main part top view of the rear wheel steering device in FIG . 9;
You.

11 is a schematic side view of the rear wheel steering device in FIG.
You.

FIG. 12 is a schematic top view of another conventional rear wheel steering device.
You.

FIG. 13 is an operation explanatory view of the rear wheel steering device in FIG . 9;
(A) is a schematic top view thereof, and (b) is a schematic side view thereof.
It is.

FIG. 14 is a diagram illustrating the operation of the rear wheel steering device in FIG . 12;
(A) is a schematic top view thereof, and (b) is a schematic rear view thereof.
FIG. 3C is a schematic enlarged top view of the rear wheel.

[Explanation of symbols]

31 Rear wheel 32 King pin 33 Knuckle spindle 34 Steer axle (rear axle) 35 Tie rod (rod) 36 Bell crank 38 Body frame 39 Swing shaft L Converting axis K axis (predetermined axis) A1 First point A2 Second point

Claims (3)

(57) [Claims] 1. The vehicle body can swing through a swing shaft.
Axle supported by the steering axle, and a turning shaft of a kingpin provided on the left and right ends of the steer axle
After steering the rear wheel by rotating the rear wheel around the line
In a wheel steering system, the swing shaft is inclined with respect to the steering axle.
Direction in which the upper side of the kingpin falls to the front of the vehicle
A rear wheel steering device wherein the kingpin is inclined with respect to the vertical direction . 2. It can rotate around a predetermined axis.
The steering axle supports the steering
It is turned by the operation force to apply steering force to the rear wheel via the rod
A bell crank is provided so that the predetermined axis is substantially parallel to the conversion axis.
Note that the crank was attached to the steer axle.
The rear wheel steering device according to claim 1, wherein 3. The vehicle according to claim 1, wherein the turning axis is orthogonal to the vehicle width direction.
The rear wheel steering device according to claim 1, wherein