GB2393695A

GB2393695A - Vehicle suspensions

Info

Publication number: GB2393695A
Application number: GB0222882A
Authority: GB
Inventors: William Richard Hutchins
Original assignee: Land Rover UK Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2002-10-03
Filing date: 2002-10-03
Publication date: 2004-04-07
Anticipated expiration: 2022-10-03
Also published as: GB2393695B; GB0222882D0

Abstract

A vehicle suspension comprises a control unit 16, 16a connected between the two hydraulic suspension units 12, 14, 12a, 14a at each end of the vehicle. Each control unit includes two shuttles 24, 26 which together with dividing walls 20, 22 in the units define control chambers 40, 42, 44, 46, 40a, 42a, 44a, 46a. These control chambers are interconnected via roll and pitch control units 64, 70 so that the spring rate of the suspension in roll, pitch, bounce and cross articulation can be controlled.

Description

Vehicle Suspensions The present Invention relates to vehicle suspension

systems.

It IS known to be advantageous m vehicle suspension systems to be able to control pitch, roll, bounce and cross articulation independently, so that the suspension provides dlffermg degrees of resistance to each of at least two of these 5 types of wheel movement.

Accordingly the present invention provides suspension system for connecting first and second wheels to opposite sides of a vehicle body, the system comprising first and second fluid piston units each arranged to control vertical movement of a respective one of the wheels relative to the body and a fluid control means 10 comprising housing means having two shuttles slidably mounted therein each shuttle defining, in cooperation with the housing means, an actuation chamber connected to the respective piston unit and an up control chamber and a down control chamber each of which is arranged to increase in volume as the other decreases in response to movement of the shuttle, wherein the up control chamber 15 associated with each shuttle is connected to the down control chamber associated with the other so that simultaneous movement of the first and second wheels in the same vertical direction can be accommodated by flow of fluid between the connected pairs of chambers.

Preferably the system further comprises biasing means arranged to bias both 20 the shuttles in a direction to resist flow of fluid into the actuation chambers. The biasing means can comprise a spring acting directly on the shuttles. Alternatively it could comprise a chamber defined between the shuttles and an accumulator arranged to resist the flow of fluid out of, or into, the chamber.

( - 2 Convemently at least one of the shuttles comprises a pair of pistons rigidly Interconnected and arranged on opposite sides of a dividing wall in the housing means so that the control chambers associated with that shuttle are each formed between a respective one of the pistons and the dividing wall.

5 The actuation chamber associated with said one of the shuttles Is preferably formed between one of the pistons and an end wall of the housing means.

Preferably the system further comprises interconnection means interconnecting the first pair of connected chambers with the second pair and control means arranged to control the flow of fluid through the interconnection 10 means thereby to control roll of the vehicle.

Preferably the system comprises two further fluid piston units each arranged to control vertical movement of a respective one of third and fourth wheels relative to the body, said third and fourth wheels being on opposite sides of the vehicle at an opposite end to the first and second wheels, and a further fluid control means 15 comprsmg housing means having two shuttles slidably mounted therein each shuttle defining, in cooperation with the housing means, an actuation chamber connected to the respective piston umt and an up control chamber and a down control chamber each of which is arranged to increase in volume as the other decreases m response to movement of the shuttle, wherein the up control chamber 20 associated with each shuttle IS connected to the down control chamber associated with the other so that simultaneous movement of the second and third wheels in the same vertical direction can be accommodated by flow of fluid between the connected pairs of chambers.

More preferably each connected pair of chambers in each fluid control means 25 IS interconnected with a corresponding pair of chambers in the other fluid control

( - 3 means so that cross articulation of the wheels relative to the body can be accommodated by flow of fluid between the two fluid control means.

Desirably each fluid control means includes a bounce control chamber defined between the two shuttles and the bounce control chambers of the two fluid control 5 means are interconnected. Pitch control means may then also be provided in the mterconnecton between the bounce control chambers to control vehicle pitch.

Preferred embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 IS a diagrammatic representation of a suspension system according 10 to a first embodiment of the invention, and Figure 2 is a diagrammatic representation of a suspension system according to a second embodiment of the invention.

Referring to Figure 1, in a first embodiment of the invention, a vehicle has a passive front suspension system (not shown) and rear suspension system 10 15 arranged to connect the rear wheels of the vehicle to the vehicle body, either directly or through a chassis. The system comprises two hydraulic suspension umts 12, 14 each comprising a piston arranged to move vertically with the respective wheel and a cylinder mounted on the body and arranged to move vertically with the body. The working chambers of the suspension units 12, 14 are 20 hydraulically connected to opposite ends of a control umt 16. The control unit 16 comprises a cylindrical housing 18 with two dividing walls 20, 22 perpendicular to the cylinder axis dividing it into three sections. Two shuttles 24, 26 are located inside the housing 18. Each of these comprises two pistons 28, 30, 32, 34 of circular cross section which fit slidably inside of the housing 18 and are spaced apart, being

( - 4 rlpldlv interconnected by a connectlne rod 36, 38. Each connecting rod 36, 38 extends through a hole In a respective one of the dividing walls 20, 22 and is slidable though it so that the two pistons 28, 30, 32, 34 attached to it are on opposite sides of the dividing wall and define therewith respective control 5 chambers 40, 42, 44, 46 which will be referred to as left up chamber 40, left down chamber 42, right up chamber 44 and right down chamber 46 on the basis of the direction of travel of the part of the vehicle body close to the relevant wheel when fluid enters the chamber and it increases In volume. In terms of 'rice height' fluid flowing into the left up chamber Increases the ride height at the left wheel etc. The 10 chambers 46, 48 formed between the shuttles 24, 26 and the end walls 50, 52 of the housing 18 comprise actuation chambers which are connected to the suspension units 12, 14. The chamber 54 between the shuttles 24, 26 forms a pitch control chamber which Is connected to a hydraulic accumulator 56 which allows fluid to leave and enter the pitch control chamber against a controlled resistance.

15 The left up chamber 40 and the right down chamber 46 are hydraulically interconnected by a right roll mterconnectlon pipe 58 and the right up chamber 44 and left down chamber 42 are interconnected by a left roll interconnection pipe 60.

The left and right roll interconnection pipes are themselves interconnected by a roll control pipe 62 with a roll control unit 64 in it. This roll control unit 64 could 20 just comprise a valve to control the flow of fluid between the two roll Interconnection pipes 58, 60, but in this embodiment also includes a pump to actively control vehicle roll. The working chambers of the left and right suspension umts 12, 14 are also directly connected to left wheel and right wheel accumulators 66, 68 respectively. These allow a certain amount of fluid to leave and enter the 25 suspension units without passing through the control unit 16.

In operation, if the two rear wheel tend to move in the same direction relative to the vehicle body e.g. under bounce or pitch, the shuttles 26, 26 will either move

( - 5 towards each other or away from each other. Fluid will therefore be able to flow through the two roll Interconnection pipes 58. GO without passing through the roll control unit 64. The resistance to this movement will therefore be determined by the spring rates of the accumulator 56 and of the wheel accumulators 66, 68.

5 Typically the wheel accumulators might be set up to have a relatively low volume and a low spring rate so as to absorb high frequency vibrations, and the accumulator 56 might have a larger volume and a higher spring rate so as to determine the spring rate of the suspension In pitch and bounce.

Under vehicle roll, 1.e. when the two sides of the vehicle are moving in 10 opposite directions, the two shuttles will tend to move m the same direction, and fluid will tend to flow from one of the roll interconnection pipes 58, 60 to the other, depending on the direction of roll. This flow IS controlled by the roll control unit.

Also the pump in the roll control unit is operated so as to pump the fluid in the opposite direction to that in which it tends to flow. This provides an active 15 resistance to vehicle roll which can be used, for example, to keep the vehicle level under cornering, provided the control unit receives input from suitable sensors measuring the relevant vehicle parameters such as vehicle speed and steering angle. In an alternative arrangement the roll control unit could comprise a simple 20 passive two- way piston which would provide controlled resistance to the flow of fluid between the two roll interconnection pipes 58, 60. It would even be possible to provide no Interconnection between the roll interconnection pipes 58, 60, so that the wheel accumulators 66, 68 would accommodate all vehicle roll.

Referring to Figure 2 In a second embodiment of the invention a vehicle 25 suspension comprises a rear suspension as in the first embodiment, corresponding features of which are indicated by corresponding reference numerals, and a front

( l - 6 suspension lea which connects the two front wheels of the vehicle to the body.

This Is Identical to the rear suspension unit and corresponding features are educated by the same reference numerals followed by an 'a'. In addition the front and rear right roll interconnection pipes 58, 58a are connected together and both 5 connected to the same side of the roll control umt 64 and the front and rear left roll Interconnection pipes 60, 60a are connected together and both connected to the other side of the roll control unit 64. Also the pitch control chambers 54, 54a of the two control umts 16, 16a are connected together through a pitch control unit 70.

This, like the roll control unit 64, can take a number of forms so as to passive or 10 active control of vehicle pitch. Finally the pitch control accumulator 56 has been replaced by a simple spring In the pitch control chamber of each control unit. The rate of these springs determines the spring rate of the suspension in bounce.

A beneficial result of this interconnection is that in cross articulation fluid can flow between the roll interconnection pipe 58, 60 at the rear of the vehicle and the 15 opposite roll Interconnection pipe 60a, 58a at the front of the vehicle without passing through the roll control umt 64. This enables a high degree of cross articulation In the system.

It will be appreciated that the embodiments described can be tuned in various ways for various types of vehicle so as to give spring rates for the suspension in 20 bounce, pitch, roll and cross articulation suitable which are suitable for each.

Claims

( - - CL31MS

1. A suspension system for connecting first and second wheels to opposite sides of a vehicle body, the system comprising first and second fluid piston units each arranged to control vertical movement of a respective one of the wheels relative to the body and a fluid control means comprising housing means having two shuttles shdably mounted therein each shuttle defining, in cooperation with the housing means, an actuation chamber connected to the respective piston unit and an up control chamber and a down control chamber each of which is arranged to increase In volume as the other decreases in response to movement of the shuttle, wherein the up control chamber associated with each shuttle is connected to the down control chamber associated with the other so that simultaneous movement of the first and second wheels In the same vertical direction can be accommodated by flow of fluid between the connected pairs of chambers.

2. A system according to claim I further comprising biasing means arranged to bias both the shuttles In a direction to resist flow of fluid into the actuation chambers.

3. A system according to claim 2 wherein the biasing means comprises a spring acting directly on the shuttles.

4. A system according to any foregoing claim wherein one of the shuttles comprises a pair of pistons rigidly interconnected and arranged on opposite sides of a dividing wall in the housing means so that the control chambers associated with that shuttle are each formed between a respective one of the pistons and the dividing wall.

(

5. A system according to claim 4 wherem the actuation chamber associated with said one of the shuttles is formed between one of the pistons and an end wall of the housing means.

6. A system according to any foregoing claim further comprising interconnection means interconnecting the first pair of connected chambers with the second pair and control means arranged to control the flow of fluid through the Interconnection means thereby to control roll of the vehicle.

A system according to any foregoing claim comprising two further fluid piston units each arranged to control vertical movement of a respective one of third and fourth wheels relative to the body, said third and fourth wheels being on opposite sides of the vehicle at an opposite end to the first and second wheels, and a further fluid control means comprising housing means having two shuttles slidably mounted therein each shuttle defining, in cooperation with the housing means, an actuation chamber connected to the respective piston unit and an up control chamber and a down control chamber each of which is arranged to increase m volume as the other decreases in response to movement of the shuttle, wherein the up control chamber associated with each shuttle Is connected to the down control chamber associated with the other so that simultaneous movement of the second and third wheels in the same vertical direction can be accommodated by flow of fluid between the connected pairs of chambers.

8. A system according to claim 7 wherem each connected pair of chambers in each fluid control means is interconnected with a corresponding pair of chambers In the other fluid control means so that cross articulation of the wheels relative to the body can be accommodated by flow of fluid between the two fluid control means.

9. A system according to claim or claim 8 wherein each fluid control means includes a bounce control chamber defined between the two shuttles and the bounce control chambers of the two fluid control means are interconnected.

10. A system according to claim 9 wherein pitch control means Is provided In the Interconnection between the bounce control chambers to control vehicle pitch.

11. A vehicle suspension system substantially as herenbefore described with reference to the accompanying drawings.