JPH0319109B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a steering device for front and rear wheels of a vehicle.

(Prior art) As one of the four-wheel steering systems for vehicles, a lever that swings in conjunction with the steering wheel is provided at the front of the vehicle body, and an arm that connects and supports tie rods for the left and right rear wheels is located in the middle. It is known that the arm is pivoted and one half of the arm is connected to the lever by a link. According to this, it becomes possible to steer the rear wheels in the opposite direction to the front wheels by steering the steering wheel, thereby obtaining a small turning radius and improving maneuverability of the vehicle.

(Problem to be solved by the invention) However, because the steering system has a so-called linear characteristic, in which the rear wheels are steered in the opposite direction to the front wheels even when the steering wheel is operated at a small steering angle, it is difficult to drive in general, especially when driving straight. Because the steering wheel response in the vicinity is sharp, it becomes difficult to keep the vehicle going straight.

Therefore, an object of the present invention is to realize non-linearity of the rear wheel steering characteristics by adding some ingenuity to the above-mentioned steering system, so that when the steering wheel is operated at a small steering angle, the rear wheels can be turned almost as easily as in a normal front wheel steering vehicle. This makes it possible to either not steer the vehicle or to slightly steer it in the same direction as the front wheels, and when the steering wheel is operated at a large steering angle, the rear wheels can be relatively largely steered in the opposite direction to the front wheels to obtain a small turning radius. An object of the present invention is to provide a steering device for front and rear wheels that maintains straight running performance and also allows a vehicle to be moved diagonally left and right to easily perform width closing.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a lever 41 that is disposed at the front of the vehicle body and swings in conjunction with the handlebar.
and a half part of an arm 47 which is pivotally supported at the intermediate part and connects and supports tie rods for the left and right rear wheels.
1, a lever 41 and a link 51 are connected by a crankshaft 53, and a pinion 56 provided on a shaft portion 54 of the crankshaft 53 on the lever 41 side;
External gear 57 or internal gear 1 whose shaft center is the pivot point of lever 41 to engage with
57 and a gear fixed on the vehicle body side, and this planetary gear mechanism is arranged between the steering gear box 34 provided at the lower part of the steering wheel column 33 and the vehicle body frame 2 below the steering gear box 34. It is characterized by

(Example) Examples will be described in detail below based on the accompanying drawings.

FIG. 1 is a cutaway side view of a riding working machine, and FIG. 2 is a plan view of a steering system. In this embodiment, a riding working machine 1 such as an agricultural tractor is equipped with front and rear wheel steering systems.

The riding work machine 1 is equipped with an engine 3 with a vertical crankshaft 4 mounted on the front part of a frame 2, a transmission case 5 is arranged at the rear part of the frame 2, and a transmission input shaft 6 and a crankshaft 4 are connected to each other. They are connected by a propulsion shaft 8, a seat 9 is placed on the rear part of the vehicle body, and front wheels 11, 11 with the same diameter and a rear wheel 1 are mounted on the front, rear, left and right sides of the vehicle body.
2, 12, such a work vehicle has a handle 31
Front and rear wheel steering can be performed by operating the , and four-wheel drive is possible.

That is, reduction cases 13, 13 are disposed on both sides of the transmission case 5, and the input shaft thereof and the output shaft of the differential provided in the transmission case 5 are interlocked and connected, and the reduction output shafts 14, 14 are connected to each other.
Attach the rear wheels 12, 12 to the. and engine 3
A differential case 15 is disposed below, and connects a differential input shaft 16 and a transmission output shaft 7 with a propulsion shaft 17. Further, reduction cases 18, 18 are disposed on both sides of the differential case 15, and the input shaft and the differential output shaft, and the reduction output shaft 1
Attach the front wheels 11, 11 to 9, 19. A four-wheel drive system is thus constructed.

The four-wheel steering system is constructed as follows.

First, the reduction cases 18, 18 bearing the front wheels 11, 11 are made swingable around the king pins 21, 21, and the knuckle arms 22, which extend rearward,
22 is provided, and tie rods 23, 23 are connected to the knuckle arms 22, 22 by ball joints 24, 24. Further, the reduction cases 13, 13 bearing the rear wheels 12, 12 are also swingable around the king pins 26, 26, and the knuckle arms 2 extending inwardly.
7, 27 are provided, and tie rods 28, 28 are connected to the knuckle arms 27, 27 by ball joints 29, 29.

A gearbox 34 is provided at the bottom of the handle column 33 through which the steering shaft 32 of the handle 31 passes longitudinally, and this gearbox 34 is connected to the engine 3.
Placed at the rear. A pinion 35 that rotates in conjunction with the steering shaft 32 is disposed in the front part of the gear box 34, a sector gear 36 that meshes with the pinion 35 is provided, and a support shaft 37 integrated with the sector gear 36 hangs downwardly and protrudes below the gear box 34. let A lever 41 is integrally provided on the protrusion of this support shaft 37.

This lever 41 has a substantially bell-crank shape when viewed from above, and is fixed to the support shaft 37 at the corner of the intermediate portion, and connects the inner ends of front wheel tie rods 23, 23 with ball joints on the left and right sides of the tip of a half portion 42 extending forward. Connect and support at 45 and 45. Further, a side U-shaped portion 44 is provided at the tip of the other half portion 43 extending toward the rear side of the lever 41 .

On the other hand, the frame 2 in front of the transmission case 5
A support shaft 46 is set up on the support shaft 46, and an arm 47 having a substantially bell-crank shape in plan view is pivotally supported at the corner of the intermediate portion thereof, and a tip portion extending forward on both sides of the arm 47 is attached to the support shaft 46. The inner ends of the rear wheel tie rods 28, 28 are connected and supported by ball joints 49, 49.

In the above, the support shaft 37 of the lever 41 and the support shaft 46 of the arm 47 are both arranged on the width center line of the vehicle body, and the right half of the arm 47 has a protrusion 4 at its tip.
8 will be provided.

A linkage link 51 is pivotally connected to this arm protrusion 48 by a pin 52.

Furthermore, as shown in FIGS. 3 and 4, the lever 4
The U-shaped portion 44 and the front end of the link 51 are connected by a crankshaft 53. That is, the crankshaft 53 has upper and lower crank pins 54, 55 whose shaft centers are eccentric e.
The front end of the link 51 is pivotally supported by the lower crank pin 55, and thus the link 51
intersects with the width center line of the vehicle body, while an upper crank pin 54 is longitudinally supported in the U-shaped portion 44, and a pinion 56 is integrally provided at the middle portion of the crank pin 54 facing inside the U-shaped portion 44. .

An external gear 57 with which the pinion 56 meshes is fixed to the lower surface of the gear box 34. This external gear 57 forms a sector gear type sun gear whose axis is aligned with the axis of the support shaft 37,
This sun gear 57 is fixed to the lower surface of the gear box 34 with bolts 58. Therefore, the pinion 56 forms a planetary pinion that rotates around the outer periphery of the sun gear 57.

The above planetary gear mechanism 56, 57 and crankshaft 5
Perform the initial settings in step 3 as follows.

First, the joint pin 55 with the link 51 is placed on the straight line connecting the center point ₀₁ of the sun gear 57 and the center point ₀₂ of the planetary pinion 56 in the neutral steering state.
Match the center point P of That is, initial settings are made as shown diagrammatically in FIG. R ₁ in the diagram is sun gear 5
7, R ₂ is the standard pitch radius of the pinion 56, R ₃ is the eccentricity of the joint pin 55 with respect to the pinion 56, and α is the rotation angle of the lever 41 from the neutral position.

Then, if we take a rectangular coordinate system that intersects at 0 _{and 1} points, the 6th
As shown in the figure, according to the conditions of an epicycloid, R ₁ α=R ₂ θ ∴θ=(R ₁ /R ₂ ) α …() Therefore, the coordinates of the 0 ₂ points are x ₁ = (R ₁ + R ₂ )cosα ...() y ₁ = (R ₁ + R ₂ ) sinα ...() Next, find the relative coordinates of point P with respect to point ₀₂ .

First, if R ₃ = R ₂ , that is, point P coincides with the reference pitch circle of the pinion 56, then as is clear from Fig. 7, X = -R ₂ cos (α + θ) ... () Y = -R ₂ sin (α+θ) …() And the coordinates of point P relative to 0 ₁ point are x=x ₁ +X,
Since it is expressed as y=y ₁ +Y, x=(R ₁ +R ₂ )cosα−R ₂ cos(α+θ) y=(R ₁ +R ₂ )sinα−R ₂ sin(α+θ) Substitute the formula () into this. x = (R ₁ + R ₂ ) cos α − R ₂ cos {(R ₁ + R ₂ / R ₂ ) α} … () y = (R ₁ + R ₂ ) sin α − R ₂ sin { (R ₁ + R ₂ / R ₂ )α} …() As a result of the above, the value of y in equation () is almost lever 41
This is the control stroke of the joint pin 55 at the rotation angle α.

If the point P is not aligned with the reference pitch circle of the pinion 56, that is, if the center point of the joint pin 55 is set as the point P', the above (), (),
The formulas () and () are as follows.

X = -R ₃ cos (α + θ) ... () Y = -R ₃ sin (α + θ) ... () x = (R ₁ + R ₂ ) cos α - R ₃ cos {(R ₁ + R ₂ / R ₂ ) α} ... ()y=( _R1 + _R2 )sinα− _R3sin {( _R1 + _R2 / _R2 )α}…() And the center point P of the joint pin 55 or
The locus of P' is shown in Figure 8. here
R ₁ =76.5, R ₂ =12, and when R ₃ =17, trajectory A is drawn, when R ₃ =12, trajectory B is drawn, and when R ₃ =8, trajectory C is drawn.

Further, the steering characteristics of the rear wheels 12, 12 corresponding to each locus are shown in FIG. 9. Here lever 4
The operating angle of 1 is ±38.5°, linear characteristic L shows the conventional characteristic, and areas (A) and (B) are anti-phase steering of the front and rear wheels, and areas (C) and (D) are in-phase steering. represents.

As is clear from this characteristic diagram, R ₃ > R ₂ , that is, when the center of the joint pin 55 is set outside the reference pitch circle of the pinion 56, that is, the center point
In the case of P', the rear wheels 12, 12 can be slightly steered in the same direction as the front wheels 11, 11 within a small steering angle range of the steering wheel 31, and the vehicle can be moved diagonally left and right, and the width It is possible to easily carry out adjustments, etc.

If R ₃ ≦ R ₂ , that is, if the center of the joint pin 55 is set inside the reference pitch circle of the pinion 56 , that is, if it is the center point P, then in the small steering angle range of the handlebar 31 , the rear wheels 12 , 12 There is almost no steering required, and the vehicle can maintain straight travel in the same way as a normal front-wheel steering vehicle.

In any case, the rear wheels 12, 12 can be largely steered in the opposite direction to the front wheels 11, 11 within the large steering angle range of the handle 31, so a small turning radius can be obtained, and the maneuverability of the vehicle can be improved. It will be good.

The abduction cycloid has been explained above, but the adduction cycloid will now be explained.

In this embodiment, as shown in FIGS. 10 and 11, the internal gear 15 is engaged with the pinion 56.
7 is fixed to the lower surface of the gear box 34. This internal gear 157 forms an arcuate ring gear whose axis is aligned with the axis of the support shaft 37, and is fixed to the lower surface of the gear box 34 with bolts 158. Therefore, the pinion 56 forms a planetary pinion that rotates around the inner circumference of the internal gear 157.

The above initial settings of the planetary gear mechanisms 56, 157 and the crankshaft 53 are such that the planetary pinion 56 is placed on the straight line connecting the center point ₀₁ of the internal gear 157 and the center point P of the joint pin 55 of the link 51 in the neutral steering state. This is done by aligning the center points 0 _{and 2} .

Also, as shown in Fig. 12, the internal gear 1
It is the same as above except that the reference pitch circle radius of 57 is set to _R1 , and the above-mentioned conditional expressions also hold true with this internal rotation cycloid system.

FIG. 13 shows the trajectory of the center point of the joint pin 55, and FIG. 14 shows the steering characteristics of the rear wheels 12, 12 corresponding to each trajectory. Here, R ₁ = 88.5, and the locus and characteristic A are R ₂ = 12, R ₃ = 17,
B is the case when R ₂ =R ₃ =12, C is the case when R ₂ =12 and R ₃ =8, and D is the case when R ₂ =R ₃ =8.

In this way, even with the adduction cycloid method,
It can be seen that the same effect as the above-mentioned epicycloid system can be obtained.

It goes without saying that the above-mentioned steering device for the front and rear wheels can be applied not only to work vehicles but also to general vehicles such as passenger cars.

(Effects of the Invention) As described above, according to the present invention, the lever is disposed at the front of the vehicle body and swings in conjunction with the steering wheel, and the tie rods for the left and right rear wheels are connected and supported by being pivoted at the intermediate portion. In a steering device for front and rear wheels in which a half of an arm is connected by a link, the lever and the link are connected by a crankshaft, and a pinion provided on the shaft portion of the lever side of the crankshaft and the pinion are connected to each other by a link. The planetary gear mechanism consists of a gear fixed to the vehicle body using an external gear or an internal gear with the axis as the pivot point of the lever for meshing, making the rear wheel steering characteristics non-linear with a relatively simple structure. can be realized. Therefore, when operating the steering wheel at a small steering angle, it is possible to turn the rear wheels almost not or slightly in the same direction as the front wheels, similar to a normal front-wheel steering vehicle, whereas when operating the steering wheel at a large steering angle, the rear wheels can be steered slightly in the same direction as the front wheels. Since the wheels can be steered by a relatively large amount in the opposite direction to the front wheels, a small turning radius is obtained, which improves the maneuverability of the vehicle, and it also makes it easier to maintain straight forward movement, and it also allows the vehicle to be moved diagonally to the left or right. It also becomes possible to easily perform width adjustment, etc.

Moreover, according to the present invention, the planetary gear mechanism that provides the above-mentioned rear wheel steering characteristics is disposed between the steering gear box provided at the bottom of the steering wheel column and the vehicle body frame below the steering gear box. The space between the lower steering gear box and the vehicle body frame below it can be used effectively, and maintenance of the gear box and planetary gear mechanism from above can be performed all at once.

[Brief explanation of the drawing]

Figure 1 is a cutaway side view of the riding work machine, Figure 2 is a plan view of the steering system, Figure 3 is an enlarged side view of the main parts, Figure 4 is the same plan view, and Figure 5 is a diagrammatic representation. 6 is a diagram showing the relative coordinates of the center point of the joint pin with respect to the center point of the external gear; FIG. 7 is a diagram showing the relative coordinates of the center point of the joint pin with respect to the center point of the pinion; Figure 8 is a locus diagram of an epicycloid, Figure 9 is a rear wheel steering characteristic diagram, Figure 10 is an enlarged side view of the main part showing the second embodiment, Figure 11 is a plan view of the same, and Figure 12 is a line diagram. FIG. 13 is a trajectory diagram of an internal rotation cycloid, and FIG. 14 is a rear wheel steering characteristic diagram. In the drawing, 11 is a front wheel, 12 is a rear wheel, 23 is a tie rod for the front wheel, 28 is a tie rod for the rear wheel, and 31 is a tie rod for the rear wheel.
is a handle, 34 is a gearbox, 35 is a pinion, 36 is a sector gear, 37 is a support shaft, 41 is a lever, 46 is a support shaft, 47 is an arm, 51 is a link,
53 is a crankshaft, 54 is a shaft portion on the steering input side, 5
5 is a joint pin, 56 is a planetary pinion, 57 is an external gear, and 157 is an internal gear.

Claims (1)

[Scope of Claims] 1. A lever that swings in conjunction with the handlebar is disposed at the front of the vehicle body, and an arm that connects and supports tie rods for the left and right rear wheels is pivoted at an intermediate portion, and one half of the arm and In a vehicle steering system, the lever and the link are connected by a link, and the lever and the link are connected by a crankshaft, and the lever and the link are connected by a crankshaft, and the lever and the link are connected by a crankshaft. A planetary gear mechanism is constituted by a pinion provided on a shaft portion on the lever side, and a gear fixed on the vehicle body side by an external gear or an internal gear with the shaft center as a pivot point of the lever so that the pinion meshes with the pinion. In addition, a front and rear wheel steering device characterized in that the planetary gear mechanism is disposed between a steering gear box provided at the bottom of a steering column and a vehicle body frame below the steering gear box.