WO1996002397A1

WO1996002397A1 - Vehicle suspensions

Info

Publication number: WO1996002397A1
Application number: PCT/GB1995/001655
Authority: WO
Inventors: Martin Woolston
Original assignee: MG Rover Group Ltd
Current assignee: MG Rover Group Ltd
Priority date: 1994-07-15
Filing date: 1995-07-13
Publication date: 1996-02-01
Anticipated expiration: 1997-01-15
Also published as: GB9622834D0; AU2896495A; GB9414356D0; GB2302066A; GB2302066B

Abstract

A suspension is arranged to support wheels (20) on both sides of a vehicle for movement in the vertical direction. The suspension includes two suspension arms (16) mounted, in use, on a body or chassis (10) of the vehicle and arranged to move vertically in sympathy with the wheel movement. A transmission unit (24) is supported by the arms (16). The transmission unit (24) transmits drive to the wheels (20) through driving shafts (22). In use, vertical movement of the wheels (20) is transmitted through the arms (16) to produce a smaller vertical movement of the transmission unit (24) relative to the body or chassis (10). Such a suspension is shown in Fig. 1 of the drawings.

Description

VEHICLE SUSPENSIONS

The invention relates to vehicle suspensions and in particular to arrangements for supporting differentials on suspension systems for driven wheels.

The mass of a vehicle can be sub-divided into two categories: sprung mass and unsprung mass. Sprung mass is that part of the vehicle mass which is carried by the suspension and includes the vehicle body and engine. Unsprung mass is that part of the vehicle mass which is carried by the wheels but not through the suspension and includes the wheels themselves and their axles. It is generally thought that reducing the unsprung mass of a vehicle improves ride comfort.

Generally, known live axle non-independent suspensions carry the final drive transmission unit, i.e. the crown wheel and pinion and differential gears, on the axle, as unsprung mass. In that configuration, the transmission unit is allowed to move vertically in unison with the wheels.

Independent suspensions carry the final drive transmission unit as sprung mass by mounting it on, for example, the chassis. As the assembly is fixed to the chassis, wheel movements do not cause corresponding movements in the transmission unit assembly and the wheels are driven by shafts from the transmission unit which are connected to the wheels through a series of universal joints. Vertical wheel travel is limited in independent suspensions by the maximum angle through which power can be transmitted through a universal joint.

Non-independent suspensions may allow more vertical wheel travel than independent suspensions but suffer from the drawback of higher unsprung mass whilst independent suspensions have lower unsprung mass but more restricted wheel travel .

It is an object of the present invention to provide an improved form of vehicle suspension.

According to the invention, there is provided a vehicle having a suspension system arranged to support a wheel on each side of a vehicle for movement in the vertical direction, the suspension including suspension means for each wheel, each suspension means being connected to a sprung part of the vehicle and to an unsprung part of the vehicle associated with one of said wheels, and a transmission unit through which drive can be transmitted to driving shafts for said wheels, the transmission unit being connected to each suspension means such that, in use, vertical movement of either of said wheels will be transmitted through the respective suspension means to produce a smaller vertical movement of the transmission unit relative to the sprung part of the vehicle. In that way, at least part of the mass of the transmission unit is supported as sprung mass by the body, while vertical movement of the transmission unit in sympathy with the vertical movement of the wheels is allowed. The latter feature is most advantageous as the wheels will be able to travel vertically for a greater distance before any universal joints, through which drive is typically transmitted to the wheels, reach their angular limit .

The suspension means may each comprise a single member, and the members may comprise guide members in that they guide the movement of the wheels relative to the sprung part of the vehicle. Alternatively, or in addition, they may comprise support members in that they support the wheels.

The transmission unit may include a housing which is connected directly to each of the suspension means.

Alternatively the transmission unit may be supported on a support member which is connected to the said suspension means.

Each member preferably has one end arranged to move vertically with the sprung part of the vehicle and another end arranged to move vertically with one of said wheels and the transmission unit is connected to each member at a point between its two ends. In a preferred embodiment the transmission unit is pivo ally connected to each member. The pivotal connection may be effected by means of a link or links and the or each link may extend upwardly between a pivot on its associated member and a pivot on the transmission unit.

Preferably four members are provided, the members being arranged two each side of the vehicle, the transmission unit being connected to all four members.

Location means may be provided to effect sideways location for the transmission unit. The location means may be pivotally connected between the sprung part of the vehicle and the transmission unit or an element which is associated with the transmission unit. In a preferred embodiment the location means is pivotally connected between the sprung part of the vehicle and at least one of the aforementioned links. The location means may be connected to two said links on the same side of the vehicle. In the most preferred embodiment, the location means is T-shaped having its main limb connected to the sprung part of the vehicle and its transverse limb connected to said two links. The location means may extend in use between one side of the vehicle and the other, and may traverse the transmission unit.

In an alternative arrangement, the transmission unit is connected to the members by resilient means which permits relative lateral movement between the transmission unit and the members.

The transmission unit may be connected to a point on the or each member where, for a given vertical movement of the wheels, there is a smaller vertical movement of the transmission unit. In such a case, the transmission unit may be connected to the or each member at a point spaced from a mid-point of the or each member, preferably further from the wheel supporting outer end than from the inner end. In that way, most of the mass of the transmission unit is carried by the sprung part of the vehicle, as sprung mass.

The transmission unit may be positioned above the or each member.

Each said member may be arranged beneath a further member.

Each member preferably takes the form of a suspension arm such as a wishbone.

The suspension may be a de Dion type wherein a beam for interconnecting the wheels is pivotally connected to the body by said members.

Vehicle suspensions in accordance with the invention will now be described in detail by way of example and with reference to the accompanying drawings in which: Fig 1 is an elevation of a vehicle suspension in accordance with the invention viewed longitudinally of ι_he vehicle and in a static position;

Fig 2 is a similar view to Fig 1 showing the suspension of Fig 1 in a bump position and in a rebound position (in chain dotted lines) ;

Fig 3 is a plan view of the suspension of Fig 1;

Fig 4 is a side elevation of the suspension of Fig 1 looking in the direction of arrow IV in Fig 1, with the right hand wheel removed,

Fig 5 is an elevation of part of the vehicle suspension as viewed in Fig 1 showing one wheel in bump and the other in rebound.

Fig 6, 7 and 8 are elevations of a different form of suspension in accordance with the invention viewed longitudinally of the vehicle and showing the suspension in static, bump and rebound positions respectively,

Fig 9 is a plan view of the suspension shown in Fig 6,

Fig 10 is a cross-section of part of the suspension shown in Fig 6 on the line X- X in Fig 6,

Fig 11 is an elevation of the suspension of Fig 6 showing one wheel in bump and the other in rebound, Fig 12 is a plan view of yet another suspension in accordance with the invention for use on steerable wheels,

Figs 13a, 13b and 13c are elevations of the suspension of Fig 12 in different positions looking in the direction of arrow XIII in Fig 12,

Figs 14a, 14b and 14c are cross-sections of part of the suspension of Fig 12, in different positions, on the line

XIV - XIV in Fig 12,

Figs 15a, 15b and 15c are cross-sections of part of the suspension of Fig 12, in different positions, on the line

XV - XV in Fig 12,

Fig 16 is a plan view of a suspension in accordance with the invention on a de Dion suspension arrangement,

Fig 17 is an elevation of the suspension of Fig 16 looking in the direction of arrow XVII in Fig 16,

Figs 18a, 18b and 18c are cross-sections of part of the suspension of Fig 16, in different positions, on the line

XVIII XVIII on Fig 16 and

Figs 19a, 19b and 19c are cross-sections of part of the suspension of Fig 16, in different positions, on the line

XIX - XIX in Fig 16. In Fig 1, a vehicle has a body 10 (shown dotted) supported by a suspension generally indicated at 12. The suspension 12 comprises left and right upper wishbones 14 and left and right lower wishbones 16 all connected by pivots Pi at their inner ends to the body 10 and by pivots Po via stub axle carriers 18 to wheels 20 at their outer ends. Each wheel 20 is drivably connected via drive shafts 22 to a transmission unit 24 comprising a crown and pinion final drive unit and differential (not shown) . The transmission unit 24 receives drive from a propeller shaft 21. The shafts 22 are connected to the transmission unit 24 and wheel 20 by means of universal joints 23.

The transmission unit 24 is mounted on the lower wishbones 16 (constituting the aforesaid suspension means) by means of links 26 which are pivotally connected between the wishbones 16 and outwardly extending arms 25 on the transmission unit 24. The links 26 are connected to the respective lower wishbones 16 at points Pw spaced outwardly from their respective inner pivots Pi by a distance X which is approximately one third of the length L of the lower wishbones between the inner and outer pivots Pi, Po.

A T-shaped sideways location member 28 traverses the transmission unit 24 and has a main limb 30 pivotally connected at its right hand end 30a, as shown in Figs 1 and 3, to the body 10 and a transverse limb 32 pivotally connected at each end to the top of links 26 attached to the left hand lower wishbone 16 (see Fig 3) . The main limb 30 has a raised central portion 31 to provide clearance for the transmission unit 24. The limb 32 has a raised portion 32a to clear the adjacent shaft 22.

Fig 2 shows the suspension of Fig 1 in bump and rebound positions. The bump position is shown in solid lines, the roaά surface being indicated at 34. The rebound position of the suspension is shown in dotted lines, the sideways location member 28 being omitted for clarity. The road surface in rebound is indicated at 36.

In bump, the wheels 20 move simultaneously upwardly relative to the body 10 of the vehicle and the wishbones 14, 16 pivot upwardly about their inner ends. The links 26 are moved upwardly by the wishbones 16 and the links 26, in turn, move the transmission unit 24 upwardly. The sideways location member 28 also moves upwardly about the right hand end of its main limb 30 to remain clear of the transmission unit 24.

The position of the links 26 on the lower wishbones 16 causes the transmission unit 24 to be moved upwardly in sympathy with the wheels 20 but by a smaller amount. The upward displacement of the transmission unit 24 keeps the angle through which the drive shafts 22 move to a minimum, the angular movement being less than that which would be experienced if the transmission unit 24 were mounted directly on to the body 10. When the suspension rebounds, the wheels 20 drop simultaneously, causing the wishbones 14, 16 and sideways location member 28 to pivot downwardly. The downward movement of the wheels causes the transmission unit 24 to move downwardly but by a smaller distance. Again, the drive shafts 22 pivot through a smaller angle than that which would be experienced if the transmission unit 24 were fixed to the body 10.

The positioning of the pivots Pw for links 26 at distance X which is less than half the distance L between the inner and outer lower wishbone pivots Pi, Po, ensures that the majority of the mass of the transmission unit 24 is carried by the body 10 as sprung mass, while the vertical movement of the transmission unit 24 reduces the angle of movement experienced by the drive shafts 22 allowing greater vertical wheel travel than that which can be achieved with conventional independent suspension systems. Such an arrangement is particularly useful in off-road vehicles designed to ride over rough and uneven terrain.

The distance X can be selected to provide different ride characteristics. For example, if a vehicle is required primarily to give good ride comfort, the distance X can be shortened to locate the links 26 closer to the inner pivots Pi of the lower wishbones 16. In that way, the majority of the mass of the transmission unit 24 is supported by the body as sprung mass but movement of the transmission unit 24 will be minimal. If maximum vertical wheel travel is a priority, then the distance X can be increased to position the links 26 closer to the wheels 20. In that way the travel of transmission unit 24 will be increased and the pivotal movement of drive shafts 22 reduced. However, unsprung mass will be increased.

The suspension in accordance with the invention will also accommodate simultaneous movement of one wheel 20 towards its bump position and the other wheel towards its rebound position, which occurs during vehicle roll. Such positioning is shown in Fig 5. In Fig 5, the sideways location member 28 is omitted for clarity.

The use of the links 26 ensures that the roll centre of the transmission unit 24 (the roll centre being indicated at RC in Fig 5) remains at a fixed vertical position in a vertical plane P midway between the wheels 20 during the wheel movement shown in Fig 5. Slight variation in length of the drive shafts 22 is accommodated by a slidable splined engagement with the universal joints 23. With this arrangement the centre of mass of the transmission unit 24 can be arranged to lie on the axis, or "roll centre", about which the transmission will rotate when the vehicle body rolls relative to the surface on which it is travelling. If the centre of mass and the roll centre are in the same place, rolling movements of the vehicle will not result in any vertical, or horizontal, movement of the centre of mass of the transmission unit. This minimises the resistance to such rolling.

Also if only one of the wheels 20 moves vertically the transmission unit 24 will also move vertically but by a lesser amount, in this case about half the amount, that it moves if both wheels 20 mover vertically by the same amount.

Reference is now made to Figs 6 to 11 which show an alternative suspension in accordance with the invention. Parts in Figs 6 to 11 which correspond to parts in Figs 1 to 5 carry the same reference numerals and are not described in detail.

Whereas in Figs 1 to 5 the arms 25 of the transmission unit 24 are connected to the lower wishbones 16 by links 26, the arms 25 in Figs 6 to 11 are pivotally connected to the lower wishbones 16 through intermediate resilient bushes 40 (Fig 10) which accommodate the angular movement of the wishbones 16.

In Fig 10 the arm 25 and the lower wishbone 16 have coaxial bores 39, 41 which receive a resilient annular bush 40. The bush 40 is held in place by a bolt 42 which extends axially through the bush 40 and defines pivot Pi. The bolt 42 is held in position by a nut 44. Washers 46, beneath the bolt head and nut 44 respectively, retain the bush and bolt assembly in the bores 39, 41. The wheels are supported by MacPherson struts 48, 49 which are shown only in Fig. 6.

As the wheels move into a bump position, illustrated in Fig 7, the horizontal distance X between the inner pivot Pi and the axis of bolt 42 is reduced, the reduction and relative lateral movement between the arms 25 and lower wishbones 16 being accommodated by the compressibility of the bushes 40. When the wheels 20 return to the static (Fig 6) position, the wishbones 16 return to a horizontal position releasing the bush 40 from compression. A similar co pressive action occurs in the bush 40 when the suspension moves into the rebound position (Fig 8) .

As shown in Fig 11, the bushes 40 will accommodate movement of one of the wheels 20 into its bump position and simultaneous movement of the other wheel 20 into its rebound position. However, unlike the suspension of Figs 1 to 5, such wheel movement shown in Fig 11 will cause the roll centre RC of the transmission unit 24 to be displaced sideways as indicated by distance D in Fig 11. The drive shafts 22 need to be sufficiently extensible to accommodate such movement.

The arrangement shown in Figs 6 to 11 will not require a sideways location member 28 for the transmission units

24 as the transmission unit is mounted directly on the wishbones 16 instead of via links as in the earlier ficr res. The positioning of the pivot point Pw at distance X which is less than half the distance L between the inner and outer lower wishbone pivots Pi, Po, ensures that the majority of the mass of the transmission unit 24 is carried by the body 10 as sprung mass, while the vertical movement of the transmission unit 24 reduces the angle of movement experienced by the drive shafts 22 allowing greater vertical wheel travel than that which can be achieved with conventional independent suspension systems. Such an arrangement is particularly useful in off-road vehicles designed to ride over rough and uneven terrain.

As in the suspension of Figs 1 to 5, the distance X can be selected to provide different ride characteristics. For example, if a vehicle is required primarily to give good ride comfort, the distance X can be shortened to locate the pivots Pw closer to the inner pivots Pi of the lower wishbones 16. In that way, the majority of the mass of the transmission unit 24 is supported by the body as sprung mass but movement of the transmission unit 24 will be minimal. If maximum vertical wheel travel is a priority, then the distance X can be increased to position the pivots Pw closer to the wheels 20. In that way the travel of transmission unit 24 will be increased and the pivotal movement of drive shafts 22 reduced. However, unsprung mass will be increased.

If desired, the suspension of Figs 6 to 11 could include upper wishbones. Figs 12 to 15 show another suspension in accordance with the invention which carries steerable wheels. The suspension of Figs 12 to 15 is similar in many respects to the suspensions of Figs 1 to 11 and parts corresponding to parts in those figures bear the same reference numerals.

In Fig 12 a suspension 12 comprises left and right upper and lower wishbones 14, 16 respectively. The wishbones 14, 16 are connected to a vehicle body 10 at their inner ends by pivots Pi. Unlike the suspension of Figs 1 to 11, the axes about which the wishbones 14,16 pivot are not parallel to the longitudinal axis of the vehicle. The wishbones 14,16 are connected at their outer ends through stub axle carriers 18 to wheels 20. The wheels 20 are connected to drive shafts 22 and transmission 24 substantially as described in the suspension of Figs 1 to 11. As mentioned above, in the embodiment of Figs 12 to 15 the wheels 20 are steerable. The extent of steering movement of each wheel is shown in broken lines in Fig 12.

The transmission unit 24 is supported on the lower wishbones 16 by means of links 26 which are pivotally connected between the wishbones 16 and outwardly extending arms 25 on the transmission unit 24. Whereas in the suspension units of Figs 1 to 11 the links 26 are connected to the lower wishbones at points Pw spaced one third of the length of the wishbones 16 outwardly from Pi, the points Pw of the suspension of Figs 12 to 15 are connected at different distances from Pi on the arms of the wishbones 16. The points Pw₁₍ on the wishbone arms 16a in Figs 12 and 13 are spaced almost half of the way along the arm 16a from point Pi while points Pw₂ on the wishbone arms 16b are spaced only a quarter of the way along the arms 16b from points Pi. Accordingly when the wheels 20 encounter a bump, vertical movement of the wheels 20 will produce a smaller vertical movement of the transmission unit 24. The vertical movement of the transmission unit 24 will not be uniform along its length due to the positioning of points Pw₁₍ Pw₂. The part of the transmission unit 24 remote from the propeller shaft 21 will move vertically by approximately half of the vertical distance travelled by the wheels. On the other hand, the part of the transmission unit 24 closest to the propeller shaft 21 will move vertically by approximately one quarter of the vertical distance moved by the wheels. Thus the transmission unit 24 will tilt in a vertical plane containing the propeller shaft 21 during vertical displacement of the wheels 20. The suspension is configured in that way so that the propeller shaft 21 transmits drive to the transmission unit 24 through the optimum angle, regardless of wheel position.

Although the suspension of the present invention has been described in relation to independent suspension systems, it can also be applied to a non-independent suspension such as a "de Dion" system. Figs 16 to 19 show such a suspension in accordance with the invention. In Figs 16 to 19, parts corresponding to parts in Figs 1 to 15 carry the same reference numerals.

In Fig 16 a de Dion suspension arrangement comprises two lower suspension arms 50, one each side of a vehicle, each arm 50 being pivotally mounted at one end at a pivot point Pa on the vehicle chassis 10 and at its opposite end at a pivot point Pb on a vertical link 54. The vertical links 54 carry wheels 20 and are interconnected by a typical de Dion cross beam 52. Two upper suspension arms 51 are arranged one each side of the vehicle, each arm 51 being pivotally mounted at one end at a pivot point Pc on the vehicle chassis 10 and at its opposite end at a pivot point Pd on the vertical link 54. A propeller shaft 21 is enclosed in a torque tube that is pivotally connected to the chassis 10 and supports a transmission unit 24 in association with outwardly extending arms 25 supported by pivotal links 26 mounted on the lower suspension arms. The transmission unit 24 is substantially similar to those of Figs 1 to 15 and has drive shafts 22 extending therefrom, each drive shaft being drivably connected via universal joints 23 to its associated wheel 20. The transmission unit 24 is supported by means of pivotal links 26 extending upwardly from pivot points Pw on the lower suspension arms 50 to outwardly extending arms 25 on the transmission unit 24. Thus, the mass of the transmission unit 24 is shared between the sprung chassis 10 and the unsprung cross beam 52. The pivot points Pw lie approximately one-third of the way along the lower suspension arms 50 from the pivot points Pa. Lateral location of the transmission unit 24 is effected by means of light compression coil springs (not shown) mounted in the drive shafts 22 and acting towards each other.

When the wheels 20 are vertically displaced, the transmission unit 24 is displaced by the links 26 connected to the suspension arms 50. The transmission unit 24 is displaced vertically by a smaller amount than the wheels 20.

The suspensions in accordance with the invention can be used on a front-wheel drive or rear wheel-drive vehicle or on a four-wheel drive vehicle.

Claims

1. A vehicle having a suspension system arranged to support a wheel on each side of a vehicle for movement in the vertical direction, the suspension including suspension means for each wheel, each suspension means being connected to a sprung part of the vehicle and to an unsprung part of the vehicle associated with one of said wheels, and a transmission unit through which drive can be transmitted to driving shafts for said wheels, the transmission unit being connected to each suspension means such that, in use, vertical movement of either of said wheels will be transmitted through the respective suspension means to produce a smaller vertical movement of the transmission unit relative to the sprung part of the vehicle.

2. A vehicle suspension according to claim 1 wherein the transmission unit is connected to each suspension means such that, in use, simultaneous vertical movement of both of said wheels will be transmitted through the suspension means to produce a smaller vertical movement of the transmission unit relative to the sprung part of the vehicle.

3. A vehicle suspension according to claim 1 or claim 2 wherein each suspension means comprises a member having one end arranged to move vertically with the sprung part of the vehicle and another end arranged to move vertically with one of said wheels and the transmission unit is connected to each member at a point between its two ends.

4. A vehicle suspension according to claim3 wherein each member is connected at one end to the sprung part of the vehicle and at another end to one of said wheels and the transmission unit is connected to each member at a point between its two ends.

5. A vehicle suspension according to any foregoing claim in which the transmission unit is pivotally connected to the suspension means.

6. A vehicle suspension according to claim 5 in which the transmission unit is pivotally connected to the suspension means by means of links.

7. A vehicle suspension according to claim 6 in which each link extends upwardly between a pivot on its associated suspension means and a pivot on the transmission unit.

8. A vehicle according to any preceding claim including location means providing sideways location for the transmission unit.

9. A vehicle according to claim 8 in which the location means is pivotally connected between the sprung part of the vehicle and the transmission unit or an element which is associated with the transmission unit.

10. A vehicle according to claim 9 when appendant to claim 6 or claim 7 in which the location means is pivotally connected between the sprung part of the vehicle and at least one of the links.

11. A vehicle according to claim 10 in which the location means is connected to two said links on the same side of the vehicle.

12. A vehicle suspension according to claim 11 in which the location means is T-shaped having its main limb connected to the sprung part of the vehicle and its transverse limb connected to the two links.

13. A vehicle according to any of claims 8 to 12 in which the location means extends between one side of the vehicle and the other and traverses the transmission unit.

14. A vehicle according to any foregoing claim in which the transmission unit is connected to at least one of the suspension means by resilient means which permits relative lateral movement between the transmission unit and said at least one suspension means.

15. A vehicle according to claim 14 in which the resilient means comprises a resilient bush.

16. A vehicle according to claim 14 or claim 15 in which pivot means for connecting the transmission unit to the suspension means passes through the resilient means.

17. A vehicle according to claim 3 or any claim dependent thereon, in which the transmission unit is connected to the members at a point on the or each member spaced from a mid point of the member.

18. A vehicle according to claim 17 in which the transmission unit is connected to the members at a point on each member which is further from the wheel supporting outer end of the member than from the inner end.

19. A vehicle suspension according to any preceding claim in which the transmission unit is positioned above the suspension means.

20. A vehicle according to claim 3 or any claim dependent thereon in which each said member is arranged beneath a further member.

21. A vehicle according to claim 20 in which four members are provided and are mounted two each side of the vehicle and the transmission unit is connected to all four members.

22. A vehicle suspension according to any preceding claim in which the or each suspension means comprises a suspension arm.

23. A vehicle according to claim 3 or any claim dependent thereon, in which the suspension is a de Dion type wherein a beam for interconnecting the wheels is pivotally connected to the sprung part of the vehicle by said members.

24. A vehicle according to Claim 23 in which the wheels are carried by respective vertical links connected to the member or members each side of the vehicle, the beam interconnecting with said vertical links.

25. A vehicle according to any foregoing claim wherein the transmission unit is supported by the suspension means.

26. A suspension for a vehicle constructed and arranged substantially as described herein with reference to Figs 1-5, Figs 6 to 11, Figs 12 to 15 or Figs 16 to 19 of the accompanying drawings.