GB2251887A

GB2251887A - A rotary valve actuator mechanism

Info

Publication number: GB2251887A
Application number: GB9100629A
Authority: GB
Inventors: Richard Curzons; Paul David Jolliffe
Original assignee: MG Rover Group Ltd
Current assignee: MG Rover Group Ltd
Priority date: 1991-01-11
Filing date: 1991-01-11
Publication date: 1992-07-22
Also published as: GB9100629D0

Abstract

A rotary valve member 12 for switching between intake manifold passages of different lengths is operable by a vacuum actuator 13 acting through a multi-strand cable 34 located in a groove 36 in the valve member. A coiled torsion return spring 24 biases the valve member in the opposition to the rotational movement imparted by the cable. The groove radius about the valve member axis may increase in a direction towards the securing nipple 35. <IMAGE>

Description

A ROTARY VALVE ACTUATOR MECHANISM This invention relates to rotary valve actuator mechanisms.

In EP-A-0 355 960 there is described a rotary valve incorporated in an internal combustion engine inlet manifold. This valve is required to have quite a large angular travel and in EP-A-0 355 960 the limited travel of a linear actuator is converted into a relatively large rotary action by a mechanism which uses an overcentre spring and a lost-motion connection between the actuator and a crank arm. This arrangement is not entirely satisfactory in use because the overcentre spring does not exert much torque until the valve is close to either end of its extremes of travel.

A simpler mechanism of linear actuator and crank arm is also less than satisfactory in use since at the extremes of rotary travel the crank arm and the actuator line of action become very close and little torque is generated. Moreover, given normal engineering tolerances and wear, the mechanism may go overcentre and not work at all.

According to the present invention a rotary valve actuator mechanism comprises a rotary member having a curved peripheral guide surface, a tension link anchored to the rotary member and having a flexible portion to overlie the guide surface, a linear actuator adapted to provide a tensile actuating force to the tension link to move the rotary member in one direction of rotary movement and a return spring to bias the rotary member in the other direction of rotary movement.

The invention will now be described by way of example with reference to the accompanying drawings, of which Fig 1 is an end elevation of part of an internal combustion engine inlet manifold showing a rotary valve actuator mechanism according to the invention; and Fig 2 is a cross section of an end part of the inlet manifold shown in Fig 1 on the line II-II.

The inlet manifold shown in Figs 1 and 2 is generally similar to that shown in EP-A-0 355 960.

Only the lower part of the manifold is shown, namely a lower casting 11 which has two passages (not shown) for each of the cylinders of an internal combustion engine to which the manifold is to be fitted. One passage is very short and the other is longer, a rotary valve member 12 switching from one passage to the other to provide each cylinder with a relatively short inlet tract and a relatively long inlet tract, depending upon the angular position of the rotary valve member.

To effect angular movements of the rotary valve member 12, an actuator mechanism includes a vacuum operated linear actuator 13 mounted on a housing 14 which is secured to the manifold lower casting 11 by three studs 15. A stop plate 16 is secured by the same studs 15 and has a window having stop faces 17 and 18. The housing 14 has a cover 20, omitted from Fig 1 for clarity.

The rotary valve member 12 has a projection 19 which is cylindrical where it is journalled in a bearing bush 21 in the housing 14. Beyond the bush 21 the projection has a portion of C section which has radial stop faces 22 and 23 disposed at 180 degrees to each other. In use these stop faces 22 and 23 abut the stop faces 17 and 18 on the stop plate 16 to limit the range of angular movement of the valve member 12.

A coiled torsion return spring 24 is nested in the C section portion of the projection 19 and is supported on a tubular spacer 25 secured to the projection 19 by a stud 26. Flanged bushes 27 retain the spring 24 in place and help to prevent any binding. At one end the spring 24 has a tang 28 which projects into a recess 29 in the end face of the cylindrical portion of the projection 19 and at the other end another tang 31 abuts a lug 32 on the housing 14.

The return spring 24 is installed with a preload which biasses the rotary valve member 12 in the anticlockwise direction (as seen in Fig 1), stop face 17 being in abutment with stop face 22. To move the valve member 12 against the return spring 24 there is a tension link 33 comprising a flexible portion in the form of a multi-strand wire cable 34 which is connected to a diaphragm or piston in the actuator 13 and anchored to the projection 19 on the valve member 12 by a barrel nipple 35.

The cable 34 overlies the base of a V groove 36 in the C shaped portion of the projection 19, the base of the V groove 35 forming a curved peripheral guide surface. The barrel nipple 35 is secured in a cylindrical recess in the projection 19, installation being facilitated by a radial slot 37 which allows entry of the cable 34.

As shown in Fig 1, the guide surface provided by the V groove 36 is an arc of constant radius. The actuator 13 has a connection 38 for a controlled source of vacuum so that when vacuum is supplied the actuator exerts a tensile actuating force on the cable 34 tangential to the V groove 36. This force is in opposition to the return spring load and rotates the valve member 12 until the stop face 23 on the projection 19 contacts the stop force 18 on the stop plate 16.

The angular travel of the valve member 12 can be judged in Fig 1 from the angle between stop face 23 and stop face 18. The tensile force which can be exerted by the actuator 13 is substantially constant over its working stroke so that the torque available to rotate the valve member 12 is also substantially constant.

The return spring 24 has several turns to give a relatively low spring rate. This spring rate, or a higher one, can be compensated by making the base of the V groove an arc of variable radius, for example progressively increasing towards the anchor for the barrel nipple. In this way the increasing spring load is met by an increasing lever arm radius.

Claims

1. A rotary valve actuator mechanism comprising a rotary member having a curved peripheral guide surface, a tension link anchored to the rotary member and having a flexible portion to overlie the guide surface, a linear actuator adapted to provide a tensile actuating force to the tension link to move the rotary member in one direction of rotary movement and a return spring to bias the rotary member in the other direction of rotary movement.

2. A mechanism according to Claim 1 wherein the tensile actuating force is tangential to the guide surface.

3. A mechanism according to Claim 1 or Claim 2 wherein the guide surface is an arc of constant radius.

4. A mechanism according to Claim 1 or Claim 2 wherein the guide surface is an arc of variable radius.

5. A mechanism according to Claim 4 wherein the arc is of progressively increasing radius towards the anchor.

6. A mechanism according to any preceding claim wherein the return spring is a coiled torsion spring.

7. A mechanism according to any preceding claim wherein the guide surface is provided by the base of a V groove.

8. A mechanism according to Claim 7 wherein the V groove is in a C section portion of the rotary member.

9. A mechanism according to Claim 8 wherein the return spring is nested within the C section.

10. A mechanism according to Claim 8 or Claim 9 wherein the C section has radial stop faces to limit angular movement of the rotary member.

11. A rotary valve actuator mechanism substantially as described herein with reference to the accompanying drawings.