GB2318771A

GB2318771A - Roll control actuator

Info

Publication number: GB2318771A
Application number: GB9722180A
Authority: GB
Inventors: David Burke; Eric Charleux; Guillaume Dazin
Original assignee: Delphi Automotive Systems France
Current assignee: Delphi Automotive Systems France
Priority date: 1996-11-02
Filing date: 1997-10-22
Publication date: 1998-05-06
Anticipated expiration: 2017-10-22
Also published as: GB9722180D0; GB2318771B

Abstract

A roll control actuator (34) for installation between first and second axially aligned parts (14,16) of a torsion bar comprises a cylindrical housing (36) connectable at one end (38) to the first part of the torsion bar; a rod (40) positioned inside the housing, rotatable about its longitudinal axis relative the housing, extending out of the other end (42) of the housing, and connectable to the second part of the torsion bar; an external screw thread (48) on the rod inside the housing; at least one ball (50) rotatably mounted on the housing and extending into and engaging the screw thread on the rod; and control means (60,62) associated with the rod and the housing to control relative movement therebetween.

Description

ROLL CONTROL ACTUATOR Technical Field This invention relates to a roll control actuator for a roll control system of a motor vehicle.

Background of the Invention It is known to provide a roll control system for a motor vehicle which comprises a torsion bar which is formed in two parts, with an actuator positioned between the two parts. The actuator is controllably actuated to either allow free relative rotational movement of the two parts of the torsion bar about their longitudinal axes (for example, during straight line motion of the motor vehicle), or to lock the two parts together (for example, during cornering of the motor vehicle). Known roll control actuators, as, for example, described in GB-A-2212770 and GB-A-2220625, are complicated.

Summary of the Invention It is an object of the present invention to provide a roll control actuator which overcomes the above mentioned disadvantage.

A roll control actuator in accordance with the present invention for installation between first and second axially aligned parts of a torsion bar comprises a cylindrical housing connectable at one end to the first part of the torsion bar; a rod positioned inside the housing, rotatable about its longitudinal axis relative the housing, extending out of the other end of the housing, and connectable to the second part of the torsion bar; an external screw thread on the rod inside the housing; at least one ball rotatably mounted on the housing and extending into and engaging the screw thread on the rod; and control means associated with the rod and the housing to control relative movement therebetween.

The roll control actuator in accordance with the present invention is much simpler, and hence easier to assembly, then previously known actuators.

Bnef Descrlptlon of the Drawings The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic presentation of a roll control system of a motor vehicle including a roll control actuator in accordance with the present invention; Figure 2 is a cross-sectional view of the roll control actuator of Figure 1; Figure 3 is a cross-sectional view of a second embodiment of roll control actuator in accordance with the present invention; Figure 4 is a cross-sectional view of a third embodiment of roll control actuator in accordance with the present invention; and Figure 5 is a cross-sectional view of a fourth embodiment of roll control actuator in accordance with the present invention.

Description of the Preferred Embodiment Referring to Figure 1 of the drawings, the roll control system 10 comprises a torsion bar 12 which is split into first and second parts 14,16, respectively. Each end of the torsion bar 12 is connected to a wheel axle 18, 20 on which a wheel 22, 24 is rotatably mounted. The wheel axles 18, 20 are attached to the vehicle body (not shown) by way of suspension units 26, 28.

The first and second parts 14,16 of the torsion bar 12 have portions 30, 32 which are axially aligned. The axially aligned portions 30, 32 are connected by a roll control actuator 34.

The roll control actuator 34, as shown in Figure 2, comprises a cylindrical housing 35 including an outer part 36 connected at one end 38 to the portion 30 of the first part 14 of the torsion bar 12. The actuator 34 further comprises a rod 40 positioned inside the housing 35, extending out of the other end 42 of the housing, and connectable to the portion 32 of the second part 16 of the torsion bar 12. The housing 35 further includes a cylindrical sleeve 44 which is positioned inside the outer part 36 between the outer part and the rod 40. A spline connection 46 between the sleeve 44 and the outer part 36 allows the sleeve to slide in an axial direction A relative to the outer part. The rod 40 has an external screw thread 48 adjacent the sleeve 44. Balls 50 are rotatably positioned in hemispherical indentations 52 in the inner surface 54 of the sleeve 44 adjacent the screw thread 48. The balls 50 extend into the screw thread 48. The rod 40 is rotatably mounted in the housing 35 by way of bearings 56, 58 positioned in each end 38, 42, respectively, of the outer part 36 of the housing. This arrangement allows the rod 40 to rotate about its longitudinal axis relative to the sleeve 44. Control means in the form of a pair of fluid chambers 60, 62 are associated with the sleeve 44 and the outer part 36. The fluid chambers 60, 62 are positioned either side of a rib 64 which extends radially from the sleeve 44 towards the outer part 36. Seals 66, 68 at either end of the fluid chambers 60, 62 and a seal 70 on the rib 64 substantially isolate the fluid chambers from one another and from the rest of the inner area of the outer part 36. The fluid chambers 60, 62 are connected to a fluid pump 72 by way of inlets 74, 76 in the outer part 36 and pipes 78,80. The pump 72 is actuated by a sensor (not shown) which monitors the steering angle of the wheels 22, 24. The control means controls the relative axial movement between the sleeve 44 and the outer part 36 as will be explained below.

During straight line driving of the motor vehicle, the pump 72 is not operational, and no fluid pressure is applied to the fluid chambers 60, 62.

Should the portion 30 of the first part 14 of the torsion bar 12 rotate about its longitudinal axis relative to the portion 32 of the second part 16 of the torsion bar, the rod 40 will rotate about its longitudinal axis relative to the housing 35. Such relative rotation will cause the sleeve 44 to move in the axial direction A relative to the outer part 36 because of the interaction of the screw thread 48 and the balls 50. As a consequence, the torsion bar will have substantially no effect on the motor vehicle.

During cornering of the motor vehicle, the pump 72 is operated, and pressurised fluid is applied to the fluid chambers 60, 62. The pressurised fluid acts on the rib 64 to substantially prevent the sleeve 44 from moving in the axial direction A relative to the outer part 36. Because of the interaction of the screw thread 48 and the balls 50, the rod 40 will be substantially prevented from rotating about its longitudinal axis relative to the housing 36.

As a consequence, the portion 30 of the first part 14 of the torsion bar 12 will be substantially prevented from rotating about its longitudinal axis relative to the portion 32 of the second part 16 of the torsion bar, and the torsion bar will provide an anti-roll effect on the motor vehicle.

Referring to the second embodiment of roll control actuator 134 shown in Figure 3, the actuator comprises a cylindrical housing 135 which is connected at one end 138 to the portion 30 of the first part 14 of the torsion bar 12. The actuator 134 further comprises a rod 140 positioned inside the housing 135, extending out of the other end 142 of the housing, and connectable to the portion 32 of the second part 16 of the torsion bar 12. The rod 140 has an external screw thread 148 adjacent the housing 135. Balls 150 are rotatably positioned in hemispherical indentations 152 in the inner surface 154 of the housing 135 adjacent the screw thread 148. The balls 150 extend into the screw thread 148. The rod 140 is slidably and rotatably mounted in the housing 135 at the other end 142 by way of a bearing 158 positioned in the other end 142. This arrangement allows the rod 140 to rotate about its longitudinal axis relative to the housing 135, and to slide in an axial direction A relative to the housing. Control means in the form of a fluid chamber 161 is defined inside the housing 135. The rod 140 sealing extends into the chamber 161, and a piston 164 is secured to the end of the rod inside the chamber. The piston 164 makes a sealing sliding fit with the housing 135 and divides the chamber 161 into a first part 160 and a second part 162. The first and second parts 160,162 are connected to the fluid pump 72 by way of inlets 174,176 in the housing 135 and the pipes 78,80. Operation of this second embodiment of actuator 134, and the effect on the motor vehicle, is substantially the same as that described above for actuator 34. When no cornering is detected, no fluid pressure is generated in the parts 160,162 of the chamber 161, and the rod 140 is free to move relative to the housing 135.

If cornering is sensed, fluid pressure is generated in the fluid in the parts 160,162 of the chamber 161 to substantially prevent any axial sliding of the piston 164 relative to the housing 135. Such locking of the piston 164 substantially prevents the rod 140 moving rotatably or axially relative to the housing 135.

Referring to the third embodiment of roll control actuator 234 shown in Figure 4, the actuator comprises a cylindrical housing 235 which is connected at one end 238 to the portion 30 of the first part 14 of the torsion bar 12. The actuator 234 further comprises a rod 240 positioned inside the housing 235, extending out of the other end 242 of the housing, and connectable to the portion 32 of the second part 16 of the torsion bar 12. The rod 240 has an external screw thread 248 adjacent the housing 235. Balls 250 are rotatably positioned in hemispherical indentations 252 in the inner surface 254 of the housing 235 adjacent the screw thread 248. The balls 250 extend into the screw thread 248. The rod 240 is slidably and rotatably mounted in the housing 235 at the other end 242 of the housing by way of a bearing 258 positioned in the other end. The rod 242 makes a sliding guiding fit with the inner surface 254 of the housing at its end 241 remote from the second part 16 of the torsion bar 12. This arrangement allows the rod 240 to rotate about its longitudinal axis relative to the housing 235, and to slide in an axial direction A relative to the housing. Control means in the form of a pair of fluid chambers 260,262 is defined inside the housing 235. The rod 240 makes a sealing fit with the inner surface 254 of the housing 235 by way of seal 270 to define a piston 264. One fluid chamber 260 is positioned on one side of the piston 264, and the other fluid chamber 262 is positioned on the other side of the piston. A seal 268 is positioned adjacent the bearing 258. The chambers 260,262 are connected to the fluid pump 72 by way of inlets 274,276 in the housing 235 and the pipes 78,80. Operation of this second embodiment of actuator 234, and the effect on the motor vehicle, is substantially the same as that described above for actuator 34. When no cornering is detected, no fluid pressure is generated in the chambers 260,262, and the rod 240 is free to move relative to the housing 235. If cornering is sensed, fluid pressure is generated in the fluid in the chambers 260,262 to substantially prevent any axial sliding of the piston 264 relative to the housing 235. Such locking of the piston 264 substantially prevents the rod 240 moving rotatably or axially relative to the housing 235.

Referring to the fourth embodiment of roll control actuator 234' shown in Figure 5, the actuator is substantially the same as the third embodiment shown in Figure 4, and like parts have been given the same reference, but without the sliding guiding fit of the free end 241 of the rod 240 with the housing 235.

Alternative forms of control means may be used besides the pressurised fluid arrangement described above. For example, a solenoid arrangement may be used. As a further alternative, the pump may be replaced by a piston arrangement. Although the operation of the above described embodiments is directed towards having no anti-roll effect during straight line motion of the motor vehicle, it will be appreciated that an antiroll effect could also be generated during straight line motion if so desired.

Claims

1. A roll control actuator for installation between first and second axially aligned parts of a torsion bar comprises a cylindrical housing connectable at one end to the first part of the torsion bar; a rod positioned inside the housing, rotatable about its longitudinal axis relative the housing, extending out of the other end of the housing, and connectable to the second part of the torsion bar; an external screw thread on the rod inside the housing; at least one ball rotatably mounted on the housing and extending into and engaging the screw thread on the rod; and control means associated with the rod and the housing to control relative movement therebetween.

2. A roll control actuator as claimed in Claim 1, wherein the housing comprises an outer part and a cylindrical sleeve positioned between the outer part and the rod with a spline connection between the sleeve and the outer part such that the sleeve can slide in an axial direction relative to the outer part; and wherein the or each ball is rotatably mounted in a corresponding hemispherical indentation in the sleeve.

3. A roll control actuator as claimed in Claim 2, wherein the control means comprises fluid acting on either side of a rib extending radially outwards from the sleeve, the fluid being pressurisable to substantially prevent relative axial movement between the sleeve and the outer part of the housing.

4. A roll control actuator as claimed in Claim 3, wherein the fluid is held in a pair of fluid chambers positioned between the sleeve and the outer part of the housing and separated by the rib which makes a sealing fit with the outer part.

5. A roll control actuator as claimed in Claim 1, wherein the or each ball is rotatably mounted in a corresponding hemispherical indentation in the housing; and wherein the control means comprises fluid acting directly or indirectly on the rod inside the housing; the fluid being pressurisable to substantially prevent relative axial movement between the housing and the rod.

6. A roll control actuator as claimed in Claim 5, wherein the rod defines a piston which makes a sealing sliding fit with the housing to define a chamber for the fluid inside the housing on either side of the piston, the fluid acting on both sides of the piston.

7. A roll control actuator as claimed in Claim 5, wherein the rod sealingly extends into a chamber for the fluid inside the housing; and wherein a piston is secured to the end of the rod inside the chamber and makes a sealing sliding fit with the housing inside the chamber, the fluid acting on both sides of the piston.

8. A roll control actuator as claimed in any one of Claims 3 to 7, wherein the fluid is pressurised by a pump.

9. A roll control actuator substantially as herein described with reference to, and as shown in, the accompanying drawings.