GB2092081A

GB2092081A - Tilt mechanism for steering column of vehicle

Info

Publication number: GB2092081A
Application number: GB8134417A
Authority: GB
Original assignee: Nissan Motor Co Ltd
Current assignee: Nissan Motor Co Ltd
Priority date: 1980-12-04
Filing date: 1981-11-16
Publication date: 1982-08-11
Also published as: JPS5796069U; GB2092081B; JPS6346296Y2

Abstract

A steering shaft (2) which transmits rotational movement from a steering wheel (1) to a steering gear (3) comprises an upper shaft (2a) and a lower shaft (2b) connected together by a joint (4) such as a universal joint. The upper shaft is pivotally supported by supporting means (11) on a pivot axis or a tilt axis (T) which is fixed to a vehicle body (7) at a position more remote from the steering wheel than an intersection point between the upper shaft and the lower shaft so that a change of an angle between both shafts is maintained smaller than a change of a tilt angle of the upper shaft. There is further provided coupling means such as a spline coupling (13) for compensating for axial movement of the lower shaft owing to the tilt of the upper shaft. Preferably, the tilt axis is placed on a downward extension of the longitudinal axis of the upper shaft. <IMAGE>

Description

SPECIFICATION Tilt mechanism for steering column of vehicle The present invention relates to a tilt mechanism for tilting a steering column of a vehicle to offer the advantage of angular adjustment of a steering wheel.

In a conventional tilt mechanism, an upper steering shaft on the steering wheel side and a lower steering shaft on the steering gear side are swingably connected with each other by a joint, so that the upper shaft can be tilted on a joint axis.

Accordingly, when the upper shaft is tilted, a joint angle between the upper shaft and the lower shaft is changed by the same degree as a tilt angle by which the upper shaft is tilted. Therefore, an increase in the tilt angle of the upper shaft directly leads to a change of the joint angle between the upper shaft and the lower shaft, which eventually increases undesirable torque loss between both the shafts and amplifies harmful torque variation.

It is therefore an object of the present invention to provide a tilt mechanism for a steering column of a vehicle which is arranged to offer enough tilt angle of the upper shaft while a corresponding change of the joint angle between the upper shaft and the lower shaft is restricted within moderate limits.

According to the present invention, a tilt mechanism for a steering column of a vehicle comprises: an upper steering shaft the top end of which fixedly supports a steering wheel, a lower steering shaft, a first joint connecting said upper shaft with said lower shaft so as to transmit rotational movement therebetween while allowing both said shafts angular movement so that the angle between both said shafts can be changed, a second joint swingably connecting the bottom of said lower shaft with an input shaft of a steering gear, supporting means for swingably supporting said upper shaft in such a manner that said upper shaft is swingable on a supporting axis fixed to a vehicle body at a position more remote from the top end of said upper shaft than an intersection axis between both said shafts, and coupling means interposed between said upper shaft and said input shaft of the steering gear for allowing axial movement of said lower shaft while transmitting rotational movement.

Therefore, a change of the joint angle between both the upper shaft and the lower shaft is kept smaller than a change of the tilt angle of the upper shaft, so that the joint angle change is restricted within moderate limits even though the upper shaft is tilted considerably. Accordingiy, the tilt mechanism of the present invention reduces torque loss between the upper shaft and the lower shaft, restrains torque variation, and always provides good feeling of the steering operation.

In the accompanying drawings: Fig. 1 is a partially cutaway side view of the tilt mechanism according to the present invention; Fig. 2 is a schematic illustration showing changes of the joint angle between the upper shaft and the lower shaft; and Fig. 3 is a schematic illustration showing another embodiment of the present invention.

In the embodiment shown in Fig. 1. the present invention is applied to an industrial truck such as a fork lift truck. A steering wheel 1 comprises a rim 18 having a knob 1 d, spokes ibanda hub 1 c. The hub 1 C is fixed to the top end of a steering shaft 2, so that the steering wheel 1 is rotatable solidly with the steering shaft 2. The bottom end of the steering shaft 2 is connected with a steering gear3.

The steering shaft 2 is divided into two parts.

that is, an upper steering shaft 2a on the steering wheel side and a lower steering shaft 2b on the steering gear side. The upper shaft 2a and the lower shaft 2b are connected by a first joint such as a universal joint. The upper shaft 2a is disposed in a column tube 5 by means of bearing (not shown). There are provided a column tube bracket 6 fixed to the column tube 5 and a vehicle body bracket 8 fixed to the column tube 5 and a vehicle body bracket 8 fixed to the vehicle body 7, such as an instrument pansl. The vehicle body bracket 8 has a slot 8a, and the column bracket 6 has a pin 9 which is inserted through the column tube bracket 6 and slidably received in the slot 68. The pin 9 has at one end a lock handle 10 which, when turned, locks the pin 9 at a desired position within the slot 8a.

There is provided an arm 11 fixed at one end region thereof to the column tube 5 and extending downwardly along the axial direction of the column tube. The other end of the arm 11 is pivotally connected to the vehicle body 7 by a pin 1 1 a. Thus, the upper shaft 2a can be tilted solidly with the arm 11 on a tilt axis or a supporting axis T defined by the pin 1 lea and transmit torque from the steering wheel 1 to the lower shaft 2b via the first joint 4 defining a joint axis or an intersection axis J, as shown in Flg. 1. It is noted that, in this case, the tilt axis T is located on a downward extension of the longitudinal axis of the upper shaft 2a.

The bottom end of the lower shaft 2b is connected with an input shaft 3a of the steering gear 3 by a second joint 12 such as a universal joint. There is further provided, between the second joint 1 2 and the lower shaft 2b, a spline coupling 13. Reference numeral 3b denotes a steering gear housing of the steering gear 3, and 4a and 1 2a a dust boot respectively for the first joint 4 and the second joint 12. A coil spring 14 is provided between the first joint 4 and the column tube 5 for urging the column tube 5 toward the steering wheel 1. It is optional to employ a coupling using serrations instead of the spline coupling 13. When torque applied to the steering shaft 2 is not so large as in a power steering system, it is possible to employ a coupling using a sliding key.

The operation of the tilt mechanism of the present invention is as follows: The drivefs efforts to turn the steering wheel 1 through the rim 18 or the knob 1 d causes the upper shaft 2a, the first joint 4, the lower shaft 2b, the second joint 1 2 and the input shaft 3a of the steering gear 3 to rotate together. This rotational movement actuates the steering gear 3, by which the steerable wheels of the vehicle are controlled.

When the upper shaft 2a is tilted in order to lower the steering wheel 1 , the upper shaft 2a turns on the tilt axis T and comes into an angular position shown by a two-dot chain line in Fig. 2. In this case, the joint axis J simultaneously shifts rightwards to an axis J' as shown in Fig. 2, and the lower shaft 2b also tilts and takes an angular position shown by a two-dot chain line. It is noted that the tilt of the upper shaft 2a causes the joint point J to slightly lower, resulting in a slight lowering of the bottom end of the lower shaft 2b from an original point a to a point b in Fig. 2. This position change from a to b is compensated for by the spline coupling 13.

When, on the other hand, the upper shaft 2a is tilted to an angular position shown by a one-dot chain line of Fig. 2 in order to raise the steering wheel 1 ,the joint point J shifts to a lefthand axis J" in Fig. 2, and accordingly the lower shaft 2b takes an angular position shown by an one-dot chain line. This m'ovement causes the lower shaft 2b to move to a lightly higher position, so that its bottom end reaches a position c. This movement zf the lower shaft 2b is also compensated for by the spline coupling 13.

Thus, when the upper shaft 2a changes its angular position, the lower shaft also changes its angular position in the same direction, so that a change of the angle between the upper shaft and the lower shaft is kept smaller than the angular change of the upper shaft 2a.

In the embodiment mentioned above, the spline coupling 13 or other coupling means is provided between the lower shaft 12 and the second joint 12. However, this is not limitative, but such a coupling may be provided between the second joint 12 and the input shaft 3a of the steering gear 3, between two parts of the lower shaft 2b when it is divided into these two parts, between the lower shaft 2b and the first joint 4, or between the first joint 4 and the upper shaft 2a.

Fig. 3 schematically shows another embodiment of the present invention, in which the tilt axis T is not on the downward extension 2c of the longitudinal axis of the upper shaft 2a, but is placed at a position more remote from the top end of the upper shaft 2a or an intersection point between the longitudinal axis of the upper shaft 2a and a plane containing the steering wheel 1. In this embodiment, too, a change of the angle between the upper shaft 2a and the lower shaft 2b is kept smaller than the tilt angle of the upper shaft 2a, and thus, restricted within moderate limits even if the tilt angle of the upper shaft 2a increases considerably.

Claims

1. A tilt mechanism for a steering column of a vehicle, said mechanism comprising: an upper steering shaft the top end of which supports a steering wheel, a lower steering shaft, a first joint connecting said upper shaft with said lower shaft so as to transmit rotational movement therebetween while allowing both said shafts angular movement so that the angle between both said shafts can be changed, a second joint swingably connecting the bottom end of said lower shaft with an input shaft of a steering gear, supporting means for swingably supporting said upper shaft in such a manner that said upper shaft is swingable on a supporting axis fixed to a vehicle body at a position more remote from the top end of said upper shaft than an intersection axis between said upper shaft and said lower shaft, and coupling means for allowing axial movement of said lower shaft while transmitting rotational movement.

2. A tilt mechanism according to Claim 1, wherein said supporting point is placed on an extension of the axis of said upper shaft.

3. A tilt mechanism according to Claim 1, wherein said supporting axis is placed ahead of said lower shaft with respect to the forward direction of the vehicle.

4. A tilt mechanism according to Claim 3, wherein said supporting axis is placed above a straight line containing the longitudinal axis of said upper shaft in a vertical plane containing said straight line.

5. A tilt mechanism according to any of the preceding claims, wherein said coupling means is disposed between said lower shaft and said second joint for connecting both with each other.

6. A tilt mechanism according to any of Claims 1 to 4, wherein said coupling means is disposed between said second joint and said input shafts of the steering gear.

7. A tilt mechanism according to any of the preceding claims, wherein said coupling means is a coupling using splines.

8. A tilt mechanism according to any of Claims 1 to 6, wherein said coupling means is a coupling using serrations.

9. A tilt mechanism according to any of Claims 1 to 6, wherein said coupling means is a coupling using a sliding key.

10. A tilt mechanism according to any of the preceding claims substantially as herein described with reference to Figs. 1 and 2, or Fig. 3 of the accompanying drawings.