GB2123768A

GB2123768A - Vehicle steering mechanisms

Info

Publication number: GB2123768A
Application number: GB08314734A
Authority: GB
Inventors: Shoichi Sano; Yoshimi Furukawa
Original assignee: Honda Motor Co Ltd
Current assignee: Honda Motor Co Ltd
Priority date: 1982-06-01
Filing date: 1983-05-27
Publication date: 1984-02-08
Also published as: FR2527538B1; DE3319958C2; GB2123768B; GB8314734D0; FR2527538A1; DE3319958A1

Abstract

A steering mechanism in a vehicle having front and rear wheels capable of being steered, comprises: an input shaft (12) that rotates interlockedly with the vehicle steering wheel; a crank pin (14) attached to the input shaft; a joint member (20) freely supported on the crank pin; a link mechanism (26/27) pivoted at one end thereof to the vehicle body and fast at the other end thereof with the joint member; and rear wheel steering tie rods (23/23) connected to laterally spaced parts of the joint member, said link mechanism including a first link (26) pivotally connected through a rubber bushing to the vehicle body and a second link (27) fast with the joint member (20), the first and second links being pivotally connected to each other through a rubber bushing, and the first link member (26) having a larger inter- core distance (l) than the inter-core distance (???) between the input shaft and the crank pin. In this mechanism size of components associated with rear wheel steering are minimized, and also vibration in operation is minimised. For small steering wheel angles, the rear wheels are steered in the same direction as the front wheels; for larger steering wheel angles, the rear wheels are steered in the opposite direction to the front wheels. <IMAGE>

Description

SPECIFICATION Vehicle steering mechanisms This invention relates to vehicle steering mechanisms and is particularly concerned with steering mechanisms in which both front and rear road wheels are steerable through steering operation of a steering wheel. Throughout, description will be made with reference to the front and rear of a vehicle as determined by the intended direction of forward running of the vehicle.

It has already been proposed that in a vehicle both the front and the rear wheels are steered by operating the vehicle steering wheel. In one particular proposal the rear wheels are steered in the same direction as the front wheels within a relatively small steering angle range on either side of straight ahead, this being the range that is used in general during high speed running of the vehicle, whereas upon rotation of the steering wheel beyond this small steering angle range to a large steering angle such as used during low speed running of the vehicle, the rear wheels are steered in the opposite direction to the front wheels.As a result not only is a good steering attained while the vehicle is running at high speed, but also since a small radius of gyration is obtained at a large turning angle of the steering wheel when executing a U-turn or during vehicle movement into or out of a parking space, operation of the vehicle in general is enhanced.

According to the present invention there is provided a steering mechanism in a vehicle having front and rear wheels capable of being steered, comprising: an input shaft that rotates interlockedly with the vehicle steeering wheel; a crank pin attached to the input shaft; a joint member freely supported on the crank pin; a link mechanism pivoted at one end thereof to the vehicle body and fast at the other end thereof with the joint member; and rear wheel steering tie rods connected to laterally spaced parts of the joint member, said link mechanism including a first link pivotally connected to the vehicle body and a second link fast with the joint member, the first and second links being pivotally connected to each other through a rubber bushing, the first link being pivoted to the vehicle body through a rubber bushing, and the first link member having a larger inter-core distance between a pivot shaft pivotally connecting the first and second link members and a pivot shaft pivotally connecting the first link with the vehicle body than the intercore distance between the input shaft and the crank pin.In this mechanism size of the components associated with rear steering is minimised, particularly in the vertical direction and also vibration in operation is minimised along with prolongation of the life of the vibration deadening structure. A symmetrical steering amount for the rear wheels is obtained.

For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is an explanatory plan view of a vehicle equipped with a steering mechanism in which the front and rear wheels are steered; Figure 2 is a rear view of the vehicle showing its rear wheel steering mechanism; Figure 3 is a perspective view on a larger scale of a detail of the rear wheel steering mechanism; Figure 4 is a sectional side view of a further detail; Figure 5 is partly broken-away side view of yet another detail; Figure 6 is a sectional view taken on line VI VI in Figure 3; Figure 7 is a diagrammatic rear view of part of the detail of Figure 3; and Figure 8 is a perspective view on a larger scale of a detail.

Referring first to Figures 1 and 2, a steering motion of a steering wheel 1 is converted to transverse motion of two tie rods 4 for steering two front wheels 3 through a rack and pinion type steering arrangement 2 which, for example, is provided internalry with a power cylinder, the front wheels 3 being steering by a resulting pivotal movement of two knuckle arms 5 connected to the outer ends of the tie rods 4.

A linkage 6 is connected to an approximately central part of the steering arrangement 2. To this end, a shaft 9 of the linkage 6 is connected through a universal joint 8 to a shaft 7 of a driven pinion, the shaft 9 extending rearwardly from the joint 8. The driven pinion is in mesh through an idler gear (not shown) with the rack (also not shown) of the steering arrangement 2. A shaft 12 (Figure 3) which constitutes an input portion of the steering mechanism for two rear wheels 11 is connected to the shaft 9 through a universal joint 10.

The shaft 12 is disposed on the longitudinal centre line of the vehicle body inclined downwardly to the rear. A crank 13 is provided at the rear end of the shaft 12 with the crank pin 14 thereof projecting rearwards. The shaft 12 is disposed in and supported by a sleeve 1 6 which is fast with a lower arm bracket 1 5 for the rear wheels, the bracket 1 5 being attached to a cross member of a body frame (not shown) of the vehicle.

As shown in Figure 5, two front and rear rubber bushings 1 8 and 1 9 are interposed between the sleeve 1 6 fixed to the bracket 1 5 (as shown in Figure 4) and a shaft holder 1 7 for the shaft 12 supported within the sleeve 16, the shaft holder 17 being press-fitted in the sleeve 1 6 through the rubber bushings 18 and 1 9. Thus, the shaft 12 is rubber-mounted on the vehicle body and hence supported in a floating state.

Figures 4 and 5 are reverse to each other with respect to right and left in the direction showing the section of the sleeve 1 6.

As shown in Figure 3, a joint member 20, which is generally of inverted T-shape in front view, is loosely mounted at its upper portion 21 on the crank pin 14 of the crank 13 attached to the shaft 12. Two rear wheel steering tie rods 23 are connected and supported respectively through right and left ball joints 24 to upper surfaces 22a of projecting portions 22 which constitute right and left lower portions of the joint member 20.

A link bracket 25 is fixedly suspended from one side of a vehicle floor panel (not shown) in a position rearer than the joint member 20. A first link 26 is pivotally suspended from the bracket 25 through a bolt and nut 34. To the lower portion of the first link 26 is pivoted, by a bolt and nut 37, an arm member 27 which functions as a second link. The arm member 27 is formed sufficiently long beyond a centre line N with respect to the right and left of the vehicle body, and a fore portion 27a of the arm member 27 is fixed fast by bolts 28 to rear face portions 22b of the right and left projecting portions 22 of the joint member 20, whereby the joint member 20 is allowed to perform a composite pivoting motion involving vertical and transverse motions along with motion of the crank pin 14.

The first link 26 and the link bracket 25 are pivoted to each other through a rubber bushing 30, and the first link 26 and the arm 27 which functions as a second link are pivoted to each other also through a rubber bushing 31.

More specifically, as shown in Figure 6, the upper portion of the first link 26 is disposed between front and rear depending pieces 25a and 25b of the link bracket 25. The first link 26 is pivoted to the link bracket 25 with the bolt and nut 34 through the rubber bushing 30 which has been press-fitted and baked between large and small-diameter tubes 32 and 33. Thus the first link 26 is pivotally suspended in an elastically supported state with respect to the vehicle body.

In this case, by tightening of the bolt and nut 34, the small and large-diameter tubes 33 and 32 are rendered fast with the bracket 25 and the first link 26, respectively.

The lower portion of the first link 26 is disposed between front and rear pieces 27b and 27c which constitute one end portion of the arm 27 which functions as a second link. The arm 27 is pivoted to the first link 26 with the bolt and nut 37 through the rubber bushing 31 which has been press-fitted and baked between large and small-diameter tubes 35 and 36 in the same manner as above, and thus the arm 27 also assumes an elastically supported state. Also in this case, by tightening of the bolt and nut 37, the small and large-diameter tubes 36 and 35 are rendered fast with the arm 27 and the first link member 26 respectively.

In operation, the rubber bushings 30 and 31 are twisted in the circumferential directions by relative pivoting motions in reverse directions between the large diameter tubes 32, 35 and the small-diameter tubes 33, 36 induced by pivotal motions of the first link 26 and the arm 27.

Referring to Figure 7, the inter-core distance between the core 0, 1 of the pivot shaft 34 pivoting the first link 26 to the link bracket 25 and the core O2of the pivot shaft 37 pivoting the arm 27 to the link 26 is made larger than an intercore distance E between the core C, of the shaft 12 and the core C2 of the crank pin 14 which is offset with respect to the shaft 12 (l > E).

Moreover, and as also shown in Figure 7, the first link member 26 is suspended coincidently with a vertical line n which is parallel to the centre line N with respect to the right and left of the vehicle body in an unsteered state of the rear wheels 11, namely, in a neutral state. As a result, the first link 26 pivots symmetrically equiangularly in response to steering operation, and therefore the amounts of pivotal motion to the right and to the left of the joint member 20 connected to the arm 27 which is pivoted to the lower portion of the first link member 26, become symmetrical.

Further, as shown in detail in Figure 8, a longitudinally extending large-diameter hole 41 is formed in the central, upright, upper portion 21 of the inverted T-shape of the joint member 20 having a generally inverted T-shape in front view, while in the projecting portions 22 which constitute right and left lower portions of the inverted T-shape are formed vertically extending small-diameter holes 42, and in positions closer to the centre of the projecting portions 22 are formed longitudinally extending small-diameter holes 43.In the large-diameter hole 41 is loosed fitted the crank pin 14 through a bearing 44 as shown in Figure 5, while into the vertically extending small-diameter holes 42 are inserted and fixed pins 24a of the ball joints 24, and in the longitudinally extending small-diameter holes 43 are threadedly fitted the bolts 28 to fix the arm 27 to the projecting portions 22.

In Figures 1 and 2 the reference numerals 1 9 denote knuckle arms connected to the outer ends of the rear wheel steering tie rods, and the numerals 29 denote lower arms for the rear wheels.

Operation of the complete steering mechanism is as follows.

When the vehicle is travelling straight ahead, that is, when the steering wheel 1 is in a neutral or straight ahead running position, the crank 13 is in a perpendicular state with its crank pin 14 located in an upper position. In this state, if the steering wheel 1 is turned, for example, to the left, the front wheels 3 are also steered to the left, and at the same time the shaft 12 is rotated clockwise (as viewed from the rear of the vehicle) through the linkage 6 consisting of the pinion shaft 7 operated from the steering arrangement 2 through an idler gear (not shown) and the shaft 9, so that the crank pin 14 of the crank portion 13 also moves clockwise and the joint member 20 loosely fitted on the crank pin 14 pivots, at first, to the right. Consequently, the rear wheel steering tie rods 23 connected to the right and left projecting portions 22 of the joint member 20 move, at first, to the right in response to the pivotal movement of the joint member 20, and the knuckle arms 29 at first pivot counterclockwise in plan view, whereby the rear wheels 11 are steered to the left together with the front wheels 3.

The left-hand steering amount of the rear wheels 11 becomes maximum when the crank pin 14 assumes a horizontal state to the right, and thereafter until the crank pin 14 assumes a perpendicular state in its lower position, the left-hand steering amount of the rear wheels 11 is decreased gradually to zero by the left-hand pivotal motion of the joint member 20.

As the crank pin 14 moves further clockwise, from its lower position, the joint member 20 further pivots to the left, and until the crank pin 14 assumes a horizontal state to the left, the rear wheels 11 are steered in a steering amount which gradually increases to the right, that is in the direction opposite to the front wheels 3. Then, until the crank pin 14 again assumes a perpendicular state in its upper position beyond the maximum state of right-hand steering amount of the rear wheels 11 , just mentioned, the righthand steering amount of the rear wheels 11 is gradually decreased to zero by the right-hand pivotal motion of the joint member 20.

Operation of the steering mechanism when the steering wheel 1 is turned to the right is performed in the same manner.

Thus, there is constituted a turning angle function generating mechanism whereby the rear wheels 11 are steered in the same direction as the front wheels 11 through a small turning angle operation of the steering wheel 1 (up to 1800 movement of the crank pin 14 from the neutral position of the crank pin 14 which is assumed to be 0 ) and in the reverse direction through turning angle operation of the steering wheel larger than the small turning angle operation (from 1 800 to 3600 movement of the crank pin 14).

Since the vehicle steering mechanism capable of generating such turning angle functions is constructed as follows, there are brought about advantages as will be described hereinafter. That is, the joint member 20 loosely mounted and supported on the crank pin 14 is constituted by a generally inverted T-shaped part in front view which is a small-sized part, and in its upper portion 21 it is loosely fitted and supported on the crank pin 14; the rear wheel steering tie rods 23 are connected to and supported by, the upper surfaces 22a of the projecting portions 22 which constitute right and left lower portions of the joint member 20; and the arm 27 is fast with the rear faces 22b of the projecting portions 22 which constitute right and left lower portions of the joint member 20; and the arm 27 is fast with the rear faces 22b of the projecting portions 22, and is pivotally connected to the link 26 which is suspended in a position rearer than the joint member 20 on one side of the vehicle floor panel.

The provision of these constructional features has the result that it is possible to make longer each lower arm 30 as a constituent member of the rear wheel suspension mechanism according to desired suspension characteristics, it thus being possible to dispose the bearings of the right and left lower arms 30 in positions near the centre line with respect to the right and left of the vehicle body, and consequently to dispose the rear wheel steering tie rods 23 compactly in opposed manner in the vicinity of this centre line, whereby reduction in size in the vertical direction, which is considered extremely desirable from the aspect of vehicle body structure. can be attained.

Moreover, since the shaft 12 supported by the vehicle body, the first link 26 as a constituent member of the restraining mechanism or link mechanism, and the arm 27 which functions as a second link are mounted or pivoted through the rubber bushings 18 as well as the rubber bushings 30 and 31, transmission of vibrations applied to the rear wheels 11 to the vehicle body through the rear wheel steering mechanism is minimised. Thus, an anti-vibration structure is provided.

Moreover, as in the link mechanism which constitutes the restraining mechanism of the rear wheel steering mechanism, the inter-core distance I between the pivot shaft 34 of the first link 26 connected with the vehicle body and the pivot shaft 37 connected with the arm 27 which functions as a second link is set larger than the intercore distance E between the shaft member 12 and the crank pin 14 (l > E), the following features can be attained.

Because l > E, as compared with the case of l=E, the pivoting angles of the first link 26 and the arm 27 functioning as a second link respectively about the pivot shafts 34 and 37 relative to the pivoting angle of the crank pin 14 about the shaft 12 becomes smaller, thus making it possible to diminish the twisting angles of the rubber bushings 30 and 31 as anti-vibration structures respectively mounted on the pivot shafts 34 and 37. Consequently, it is possible to prolong the life of the rubber bushings 30 and 31.

The maximum value of I is set to an appropriate value in consideration of the foregoing reduction of size.

Since the link bracket 25 is fixedly suspended from the vehicle floor panel, it is desirable from the aspect of vehicle body structure that the rubber bushings 30 and 31 respectively mounted on the pivot shafts 34 and 37 of the first link 26 pivoted to such portion and the arm 27 which functions as a second link be formed of a soft rubber. In this connection, it is possible to set small the pivoting angle of the first link 26 and that of the arm 27, so even low spring constants of the rubber bushings 30 and 31 do not cause any deterioration of strength and durability, thus permitting the adoption of rubber bushings 30 and 31 having sufficiently low spring constants to give the desired insulation of vibration.

In general, moreover, if the rigidity about the king pin of the rear wheels 11 is not sufficiently high, the actual steering angle becomes smaller than the turning angle of the steering wheel, thus making it impossible to achieve a stable steering.

However, in the present construction, even if the spring constants of the rubber bushings 30 and 31 are sufficiently low, only small loads are imposed on the first link 26 and the arm 27, so even when pivotal displacements about the pivot shafts 34 and 37 are large, this will scarcely affect the displacement of the joint member 20, particularly transverse pivoting of the joint member which directly affects the steering angle about the king pin of the rear wheels 11.

Furthermore, since the first link 26 is pivotally suspended from the vehicle body so that it is substantially perpendicular in the neutral state (free of steering) of the rear wheels, the first link 26 ensures the pivotal motion of the joint member 20 at a symmetrical pivoting angle with respect to the vertical line n of the link 26 through the arm 27 which is pivotally connected to the link 26. Consequently, the steering amount of the rear wheels 11 can be made symmetrical.

In addition, as previously noted, the joint member 20 is formed in a generally inverted Tshape in front view, and the crank pin 14, rear wheel steering tie rods 23 and arm 27 are mounted thereto. Therefore it is possible to attain ,seduction in both size and weight of the joint member 20 which requires a high strength, and particularly it is possible to realise reduction in height of the joint member 20, thus greatly contributing to a further promotion of the more compact structure previously referred to.

Although in the described embodiment the arm 27 is secured to the rear faces 22b of the right and left projecting portions 22 of the joint member 20, the arm 27 and the link 26 may be disposed in positions ahead of the joint member 20, the arm 27 being secured to front faces 22c of the right and left projecting portions of 22 of the joint member 20.

Furthermore, since the arm 27 as a second link which constitutes the restraining mechanism or link mechanism for restraining the pivotal motion of the joint member 20 is pivoted to the first link 26 which is suspended from the vehicle body in a longitudinally biased position at one side with respect to the joint member 20, the arm 27 which is a large-sized component will not be subjected to large loads and hence can be reduced in its wall thickness without the need of being strengthened, thus contributing to reduction in weight of the entire mechanism in addition to reduction in weight of the joint member 20.

It will be apparent from the above description, that various characteristic features are attainable.

For example, the constituent members of the rear wheel steering mechanism can be disposed compactly without requiring a large space in the vertical direction, and a superior vibration deadening effect can be obtained. Particulariy since the intercore distance between the pivot shaft of the first link as a constituent member of the link mechanism for connection with the vehicle body and the pivot shaft thereof for connection with the arm which functions as a second link is set larger than the intercore distance between the input shaft and the crank pin, there can be attained a significant contribution to the prolongation of life of the rubber bushings as anti-vibration structures mounted on these pivot shafts.

Claims

1. A steering mechanism in a vehicle having front and rear wheels capable of being steered, comprising: an input shaft that rotates interlockedly with the vehicle steering wheel; a crank pin attached to the input shaft; a joint member freely supported on the crank pin; a link mechanism pivoted at one end thereof to the vehicle body and fast at the other end thereof with the joint member; and rear wheel steering tie rods connected to laterally spaced parts of the joint member, said link mechanism including a first link pivotally connected to the vehicle body and a second link fast with the joint member, the first and second links being pivotally connected to each other through a rubber bushing, the first link being pivoted to the vehicle body through a rubber bushing, and the first link member having a larger inter-core distance between a pivot shaft pivotally connecting the first and second link members and a pivot shaft pivotally connecting the first link with the vehicle body than the intercore distance between the input shaft and the crank pin.

2. A steering mechanism as claimed in claim 1, wherein the first link is pivoted to the vehicle body so that it is substantially perpendicular in a neutral state in which the rear wheels are not steered.

3. A steering mechanism as claimed in claim 1 or 2, wherein the joint member is formed in a generally inverted T-shape in front view having right and left projecting portions, the rear wheel steering tie rods being respectively connected to upper surfaces of these projecting portions, and the second link being secured to front or rear faces of these projecting portions.

4. A steering mechanism substantially as hereinbefore described with reference to the accompanying drawings.