JP2001097254A - Steering mechanism for trailer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steering mechanism for a trailer which can reconcile steering easiness in a low speed region and rectilinear stability in a high speed region in a higher grade. SOLUTION: This steering mechanism of a trailer 1 connected to the rear part of a tractor 2 has a wheel steered by balance between the moment around a king pin 13 acting on a wheel 12 at the time of turning by a caster trail and the holding force for the steering angle neutral position by a spring means 16, and a caster trail varying device 21 for varying the caster trail in relation to the car speed, wherein in a high speed region, the caster trail is reduced to relatively heighten the holding force for the steering angle neutral position. Accordingly, when the load of a spring means for energizing to the steering angle neutral position is constant, the caster trail is enlarged so that the restoring force to the apparent neutral position is reduced to heighten the steering easiness and on the contrary, the caster trail is reduced so that the storing force to the apparent neutral position is enlarged to heighten the steering stability.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steering mechanism for a trailer (towing vehicle) connected to a rear portion of a tractor (self-propelled vehicle).

[0002]

2. Description of the Related Art A lateral force applied to a king pin through an axle is applied to a wheel around a king pin by attaching a caster trail, that is, by shifting a point of application of a wheel load on a ground contact surface of a tire and a landing point of an extension of the king pin in a front-rear direction. It is well known that it acts as a moment to turn

On the other hand, in order to shorten the total length of the trailer when it is connected, it is preferable to rigidly couple the tractor and the trailer. However, if a trailer having no steering function is rigidly connected to the tractor, the rear wheels of the tractor and the right and left wheels of the trailer both go straight, and the turning performance is reduced. Therefore, the technology disclosed in Japanese Patent Publication No. 60-47123 is applied, and the turning force acting on the wheels at the time of turning by the caster trail and the holding force at the steering angle neutral position by the spring means are balanced. It is conceivable to configure so that the wheels of the trailer are steered.

[0004]

However, in order to increase the ease of turning the trailer wheels in a low speed range, it is better to set the caster trail large (the steering angle neutral position holding force is small), but excessively large. The caster trail (inadequate steering angle neutral position holding force) impairs steering stability at high speeds. That is, in the relationship between one caster trail and the steering angle neutral position holding force, it is not possible to achieve both easy steering in a low speed range and steering stability in a high speed range.

[0005] The present invention has been devised to solve such problems of the prior art, and its main objects are as follows.
In order to further shorten the overall length of the trailer when connected, a trailer steering mechanism capable of achieving both higher ease of steering in a low speed range and higher steering stability in a high speed range. is there.

[0006]

According to the present invention, the steering mechanism of the trailer 1 connected to the rear of the tractor 2 is provided with a king pin 13 acting on the wheels 12 when turning by the caster trail. A wheel that is steered by balancing a turning moment and a holding force of the rudder angle neutral position by the spring means 16; and a caster trail varying device 21 that changes a caster trail in relation to the vehicle speed. Then, the caster rail was made smaller to relatively increase the holding force at the neutral position of the steering angle.

With this arrangement, when the load of the spring means for biasing the steering angle to the neutral position is constant, increasing the caster trail reduces the apparent restoring force to the neutral steering angle position. If the caster trail is smaller, the restoring force to the apparent neutral position of the steering angle increases. Therefore, in the low speed range, the turning ease can be increased by increasing the caster trail, and by reducing the caster trail in the high speed range, turning of the wheels can be suppressed and steering stability can be improved. .

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a steering mechanism for a trailer according to the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIGS. 1 and 2, this trailer 1 is used by being connected to the rear end of a tractor 2 as necessary, and is attached to the rear end of the body frame of the tractor 2 in the vehicle width direction. A connecting bar 4 connected to the rear surface of the extended fixed bar 3, a loading frame 6 whose front end is connected to a swing joint 5 provided at the center of the connecting bar 4, an upper link 7 and a lower link 8. And an axle beam 9 connected to the connecting bar 4 through the connecting bar 4.

The axle beam 9 is suspended below the carrier frame 6 via a pair of left and right compression coil springs 10. Left and right wheels 12 are rotatably supported at left and right ends of the axle beam 9 via a hub carrier 11. Further, each end of the axle beam 9 and the hub carrier 11 are connected via a kingpin 13 so that the wheel 12 can be steered around the kingpin 13 as a center of rotation.

The left and right hub carriers 11 are connected via a tie rod 14 and a steering rod 15. A steering angle neutral position holding device 18 for generating a restoring force to a steering angle neutral position using a compression coil spring 16 is connected to an intermediate portion of the steering rod 15. The steering angle neutral position holding device 18 has a pair of compression coil springs 16 attached to face each other so as to generate an extension force toward the neutral position.
When one of the compression coil springs 16 starts contracting beyond the neutral position of the steering angle, the other compression coil springs 16 are provided with respective extension dimension restricting means so that they do not expand any further. Only the compression coil spring 16 contributes to the restoring force to the neutral position.

The steering rod 15 is provided with an oil damper 19 for preventing the wheels 12 from swinging when an impacting external force is applied, such as when riding on a one-wheel step.

At each of the left and right ends of the axle beam 9, caster trail variable devices 21 are provided. As shown in FIG. 3, the caster trail variable device 21 includes a kingpin holder 22 that supports the kingpin 13 and an actuator 23 that swings and drives the kingpin holder 22.
It consists of

The kingpin holder 22 is provided with a ball bearing 25 placed coaxially with the center of the wheel, with respect to a bracket 24 fixed to each end of the axle beam 9 connected to the rear ends of the upper and lower links 7, 8. It is rotatably supported via. An actuator 23 is swingably attached to the bracket 24.

The actuator 23 is composed of a motor with a speed reducer having an output shaft integrally connected to a screw bar 26, and the screw bar 26 has a slider 27 rotatably attached to the lower end of the kingpin holder 22. It is screwed. When the screw rod 26 is rotated, the slider 27 advances and retreats in the axial direction of the screw rod 26 in accordance with the rotation, and accordingly, the kingpin holder 22 swings about the ball bearing 25, and the kingpin holder 22 Thus, the inclination angle of the king pin 13 that is integral with the king pin 13 changes between the rearwardly inclined side Kf and the forwardly inclined side Kr.

As a result, the caster trail Ct, that is, the wheel load application point P on the ground contact surface of the wheel 12 and the king pin 13
Of the extension line from the landing point Q in the front-rear direction can be changed, and the moment around the kingpin acting on the wheel 12 during turning can be varied. The point of application of the wheel 12 is statically the same as the point of application of the wheel load P. However, during running, the wheel 12 moves rearward from the point P in the traveling direction due to deformation of the tire. Caster Trail Ct
It is better to determine the optimal value of.

According to the above configuration, when the tractor 2 makes a left turn, for example, when moving forward, the lower link 8 is supported at two points by the connecting bar 4 so that the axle beam 9 moves outside the turning circle, that is, to the right. Get dumped. On the other hand, the caster trail Ct is located forward with respect to the point of application of the wheel 12, so that
When a rightward lateral force acting on the axle beam 9 is input to the kingpin 13, the wheels 12 are steered to the right, that is, in the opposite direction to the tractor 2.

Next, the control procedure of the variable caster trail device 21 will be described with reference to FIG.

A vehicle speed signal V from a vehicle speed sensor 31, a reverse signal R of a reverse sensor 32 branched from, for example, a power supply line to a backlight, and a caster trail signal from a caster trail sensor 33 for detecting the position of the slider 27 and the like. Ct is input to the cast trail setting machine 34.

In the caster trail setting machine 34, the vehicle speed V
From the table of the caster trail target value Ctr (see FIG. 5) corresponding to the above, the optimum caster trail target value Ctr for the vehicle speed V at that time is obtained, and the actuator drive circuit 35 is determined based on the comparison value with the actual caster trail value Ct at that time.
To output a control signal D of the actuator 23.

This control may be one in which the kingpin angle is continuously changed steplessly. For example, the range of the vehicle speed is divided into three stages of low / medium / high so that the caster trail value suitable for each of them can be obtained. Alternatively, the angle of the kingpin may be changed stepwise.

When a reverse signal R, which may be a backlight lighting signal interlocked with the shift lever position, is input, the king pin 13 is tilted forward to caster rail C
By setting t to be opposite to the above and corresponding to the backward movement, the wheels 12 of the trailer 1 can be steered in the opposite direction to the steered direction of the tractor 2 as in the case of forward movement.

Now, assuming that the applied lateral force is constant, the steering moment M due to the lateral force acting on the kingpin increases as the caster trail Ct increases, as shown in FIG. When the spring force for holding the neutral position of the steering angle is constant, the larger the caster trail Ct, the smaller the restoring force to the apparent neutral position. Conversely, the smaller the caster trail Ct, the smaller the apparent restoring force. The restoring force to the neutral position increases. Therefore, by increasing the caster trail Ct in the low speed range and decreasing the caster trail Ct in the high speed range without changing the compression coil spring 16 of the steering angle neutral position holding device 18 as shown in FIG. In a low-speed range, the steering force for giving a trailing angle opposite to that of the tractor to the trailer side so that the lateral force applied to the axle beam 9 easily exceeds the restoring force applied to the wheels 13 to the neutral position. In the high-speed range, the steering force can be increased by suppressing the steering force so that the restoring force applied to the wheels 13 to the neutral position always exceeds the lateral force applied to the axle beam 9. In the medium speed range, the restoring force to the neutral position applied to the wheels 13 only when a large lateral force is input to the axle beam 9 such as when a large rudder angle steering is performed is made to exceed the lateral force. Door can be.

[0024]

As described above, according to the steering apparatus of the present invention, by changing the caster trail according to the vehicle speed, it is easy to steer in a low speed range and the steering stability in a high speed range. Can be compatible with higher dimensions. Therefore, according to the present invention, the mobility in the connected state of the trailer can be made equal to that in the non-connected state, so that a great effect can be obtained in further facilitating the operation when the trailer is connected.

[Brief description of the drawings]

FIG. 1 is a conceptual side view showing a state in which a trailer to which the present invention is applied is connected to a tractor.

FIG. 2 is a perspective view of a trailer to which the present invention is applied.

FIG. 3 is a conceptual side view of a caster trail variable mechanism.

FIG. 4 is a control block diagram of a variable caster trail mechanism.

FIG. 5 is a relationship diagram between a cast trail and a vehicle speed.

FIG. 6 is a relationship diagram between a steering moment and a cast trail.

FIG. 7 is a graph showing a relationship between a lateral force and a restoring force.

[Description of Signs] 1 Trailer 2 Tractor 12 Wheel 13 Kingpin 14 Tie rod 15 Steering rod 16 Compression coil spring 18 Steering angle neutral position holding device 21 Caster trail variable device

Claims (1)

[Claims] 1. A steering mechanism for a trailer connected to a rear part of a tractor, wherein the steering mechanism is steered by balancing a moment around a king pin acting on a wheel when turning by a caster trail and a holding force of a steering angle neutral position by a spring means. And a caster trail variable device that changes the caster trail in relation to the vehicle speed, and in a high-speed range, the caster trail becomes smaller in order to relatively increase the holding force of the steering angle neutral position. A steering mechanism for a trailer, comprising: