GB2217390A

GB2217390A - I.c. engine throttle valve actuation

Info

Publication number: GB2217390A
Application number: GB8907910A
Authority: GB
Inventors: Walter Schauer
Original assignee: Pierburg GmbH
Current assignee: Pierburg GmbH
Priority date: 1988-04-19
Filing date: 1989-04-07
Publication date: 1989-10-25
Anticipated expiration: 2009-04-07
Also published as: FR2630163B1; GB8907910D0; IT8947720A0; IT1231147B; DE3813046A1; FR2630163A1; GB2217390B

Description

1 k 1 DEWC1 FOR ACTUATING THE MOTTLE VALVE IN MIXTURE-FORMER OF AN

INTERNAL COMBUSTION EN

The invention relates to a device of the kind described in the preamble to Claim 1, for actuating the throttle valve in the mixture-former of an internal combustion engine.

2217390 Devices of this kind are known, for example from the German Patent Specification PS 28 21874 and OS 32 33 418, in which the throttle valve is actuated by a suction capsule equipped with a flexible diaphragm which has a venting valve cooperating with a lever which swings into the path of movement of the venting valve and vents the working chamber of the suction capsule to the external atmosphere.

The known devices are suitable for actuating the throttle valve indirectly, i.e. not by direct mechanical linkage between the accelerator pedal and the throttle valve. The movements of the accelerator pedal can be applied, for example, to a potentiometer, whose changing electrical resistance determines the position of the throttle valve. This may be achieved, for example, by the electrical resistance of the potentiometer being arranged to determine the degree of suction (i.e. the difference between atmospheric pressure and the pressure here) applied to the working chamber of the suction capsule from the intake passage of the engine, downstream of the throttle valve, or from a suction storage tank, rhythmic control valves being usually used for this purpose.

But if a fault occurs in the command signals applied to the rhythmic valve, or m some other portion of the electrical or mechanical system, which controls throttle-valve movements, a dangerous situation can arise, particularly if the internal combustion engine is powering a motor vehicle.

The intention in the present invention is therefore to equip a device of this kind with a safety arrangement which comes into action when a fault occurs.

2 This invention provides a device for actuating the throttle valve in the mixture-former of an internal combustion engine, with a throttle-control cable anchored to a throttle-cable anchor plate which cooperates with a potentiometer whose electrical resistance determines the position of the throttle valve; and with a suction chamber equipped with a moving rod drive-comected to the throttle valve; the working diaphragm in the suction chamber having a venting valve which cooperates with a lever capable of swinging into the path of movement of the diaphragm, or of the venting valve, for venting the suction chamber to the atmosphere, and in which, during normal operation of the device the lever is retained by a lock, against the influence of a return-spring, in a position where it is out of the path of movement of the diaphragm, whereas when the lock is opened this couples the lever to the throttle-cable anchor plate so that the lever now moves, with the movements of the throttle-cable anchor plate, within the path of movement of the diaphragm.

In further development of the invention the flexible working diaphragm has, fixed to it, a mechanical stop which, when the lever has swung into the path of movement of the flexible diaphragm, limits its return movement relative to the diaphragm.

Further developments are described in the subsidiary claims.

The advantages obtained will now be described with the help of the examples represented in the drawing, in which:

Figure 1 shows a longitudinal section of the device.

Fig-ure 2 is a partly sectioned view from above.

The device 1 of Figure 1 comprises a suction capsule (shown at the right of the drawing) mounted on the internal combustion engine (not shown), with a housing 2 in which is clamped by its edge a flexible diaphsagm 3 dividing the housing 2 into two chambers, a working chamber 4 on the right and an atmospheric charnber 5 on the left.

1 h 1 v 9 V 3 Fixed to the outer diaphragm plate 8 and projecting outwards from the atmospheric chamber 5 there is a rod 6 pivoted to a link 7 which actuates the throttle valve (not shown) of the engine. The two diaphragm plates contain a venting valve 9 which has a valve-rod 10 projecting inwards into the working chamber 4 of the suction capsule. The venting valve 9 controls a passage 11 connecting the two chambers 4 and 5 together. A spring 12 tends to close the venting valve 9.

Near the bottom of Figure 1 a suction connection 13 applies controlled suction to the working chamber 4 from the intake passage of the engine, downstream of the throttle valve, or from a suction tank. When the device is in normal operation the degree of suction applied to the working chamber 4, acting through the diaphragm 3, the rod 6 and the link 7, determines the position of the throttle valve.

Referring now to Figure 2, a bearing support 14, projecting sideways from the housing 2, contains a bearing in which rotates a shaft 15. Fixed to the outer end of the shaft 15 is the throttle-cable anchor plate 16, to which is anchored a throttle control cable 24 actuated by the throttle pedal of the driver. A return spring 17 tends to rotate the throttlecable anchor plate 16 anti-clockwise (as represented in Figure 1) in returning the throttle valve towards its closed position.

Fixed to the shaft 15, within the housing 2, there is a rotary potentiometer 18 which is electrically connected, over electric leads (not shown) to an electronic control computer which, when the device is operating normally, varies the degree of suction applied to the working chamber 4 in dependence on potentiometer resistance, to the effect that the existing potentiometer resistance, at each instant, determines the position of the throttle valve.

As described so far, the device is suitable for normal operation, i.e. movements of the accelerator pedal vary the degree of suction applied to the working chamber 4 and this actuates the throttle valve of the engine.

4 The arrangements for ensuring safe operation of the engine when a fault in the normal control system occurs will now be described.

Mounted rotatable on the shaft 15 is a lever 19 influenced to rotate anticlockwise (as represented in Figure 1) by a return-spring 20, whose other end is anchored to the housing 2. When the device is in normal operation the lever 19 is locked in a clockwise-rotated position (Figure 1), against the influence of the return-spring 20, by a lock 21 equipped with a locking pin 22 whose nose engages in a notch 23 of the lever 19. In this position the lever 19 stands clear out of the path of movement of the flexible diaphragm 3 and of its valve-rod 10. Anchored to the rotary throttle-cable anchor plate 16 is the throttle-control cable 24 whose other end is fixed to the accelerator pedal of the engine.

When a fault occurs in the control system which normally controls the movements of the throttle valve, this fact is recognised by a recognition device (not shown). The recognition signal, after processing if necessary in a computer, is applied as a command signal to the lock 21, which retracts the locking pin 22 from the notch 23 of the lever 19, setting the lever 19 free to rotate anti-clockwise, under the influence of its retum-spring 20, into the position shown in broken lines in Figure 1. Under these circumstances an arm 25 of the lever 19 rests against a pin 26 fixed to the shaft 15 of the throttle-cable anchor plate 16. If the lever 19 swings anti-clockwise far enough, its nose pushes the valve-rod 10 inwards, towards the left in Figure 1, against the influence of the spring 12, opening the venting valve 9 and venting the working chamber 4 through the connecting passage 11 to the atmosphere. If the diaphragm 3 was, at that time, in a position corresponding to a more open throttle valve than is demanded by the position of the accelerator pedal, the venting of the working chamber 4 to the atmosphere closes the throttle valve.

-X In these circumstances when the lock 21 has been opened to allow the lever 19 to swing anti-clockwise, all movements of the accelerator pedal, acting through the throttle-cable anchor plate 16, the shaft 15, the pin 26 and the lever 19, keep the diaphragm 3 balanced, by responsive venting of the working chamber 4, in a position determined directly by the existing position of the accelerator pedal.

As a further safety measure for the case where the diaphragm 3 is defective, or if some other defect has occured in the suction-regulating system, the diaphragm can have a backwards extension 27 equipped with a back-stop 28. Clockwise rotation of the lever 19 from the position shown in broken lines in ' Figure 1 takes the diaphragm 3 backwards with it, shifting the rod 6, the link 7 and rotating the throttle valve correspondingly.

The back-stop 28 may be hinged at 29 so that it can move from the position shown in Figure 1 only in the direction of the arrow and back again to the position shown, so as to allow the lever 19 to pass, moving anticlockwise when the lever is first released by the stop 22.

It should be observed that the invention provides, alternatively, either indirect actuation of the throttle valve, via the potentiometer 18 which controls the degree of suction applied to the working chamber 4 from the intake passage of the engine, downstream of the throttle valve, or from a suction tank, or direct actuation via the lever 19. In the indirect method of actuation a rhythmic valve can be used.

When an electronic, electrical or mechanical fault occurs in the indirect method of actuation, the device changes over to direct actuation.

A further advantage is that when the device has changed over to direct actuation of the throttle valve, each time the driver of the vehicle opens the throttle valve, by depressing his accelerator pedal, he encounters, in addition to the spring force of the usual return-spring 17, the extra resistance of the return-spring 20 of the lever 19, alerting him to the fact that the indirect throttle-valve actuating system has developed a malfunction.

6

Claims

1. A device for actuating the throttle valve in the mixture-former of an internal combustion engine, with a throttle-control cable anchored to a throttle-cable anchor plate which cooperates with a potentiometer whose electrical resistance determines the position of the throttle valve; and with a suction chamber equipped with a moving rod drive-connected to the throttle valve; the working diaphragm in the suction chamber having a venting valve which cooperates with a lever capable of swinging into the path of movement of the diaphragm, or of the venting valve, for venting the suction chamber to the atmosphere, characterised in that during normal operation of the device the lever (19) is retained by a lock (21), against the influence of a return-spring (20), in a position where it is out of the path of movement of the diaphragm (3), whereas when the lock (21) is opened this couples the lever (19) to the throttle-cable anchor plate (16) so that the lever (19) now moves, with the movements of the throttle-cable anchor plate (16), within the path of movement of the diaphragm (3).

2. Device as claimed in Claim 1, characterised by a back-stop (28) fixed to the diaphragm (3) for preventing the lever (19), once it has swung into the path of the diaphragm (3), from swinging back out of its path.

3. Device as claimed in Claims 1 or 2, characterised by a recognition device for detecting a fault in the system for actuating the throttle valve indirectly, the recognition device unlocking the lock (21) under these circumstances.

4. Device as claimed in Claim 3, characterised in that the recognition device is a portion of an electronic engine-control system which controls the degree of suction applied to the working chamber (4) of the suction capsule.

5. A device for actuating the throttle valve in the mixture-former of an internal combustion engine, substantially as hereinbefore described with reference to the accompanying drawings.

Published 1989 atThePatent Office. State House. Go-,! High Holborn. LondonWCIR4TP, Further copies maybe obtainedfrom. The Patent Office. Sales Branch, St Mary Cray. Orpiigton, Kent BR5 3RD. Printed by Xultiplex techniques ltd. St Mary Cray,]Kent, Con. V87 1 z