This invention relates to a control arrangement particularly, though not exclusively, for the control of a fuel supply for an internal combustion engine whereby the amount of fuel supplied to the engine is variable.

Under different circumstances the amount of fuel supplied can vary the engine speed and/or the output torque delivered by the engine.

The control arrangement of the invention is applicable to a fuel supply control comprising fuel supply means operable to vary the amount of fuel supplied in response to force transmitted to the fuel supply means by an operator controlled command means such as a cable slidably extending in a guide sheath, the cable and sheath forming a flexible coupling.

Typically in such an arrangement one end of the cable is connected with the fuel supply means and the other end of the cable is connected to an accelerator pedal or lever which moves the cable in response to driver demand. Up to a predetermined limit, the greater the cable movement the greater is the amount of fuel supplied. The control includes restoring means

acting in opposition to the force applied to move the cable, so that when the latter decreases the effect of the restoring means is to cause a decrease in the amount of fuel supplied. The restoring means is typically a spring means.

In some semi-automatic transmission control systems for vehicles it is desirable for the vehicle throttle to be operated independently of driver demand.

Such a fuel supply control for a motor vehicle having an internal combustion engine, comprises a throttle control valve, a cable connected to the control valve and which is operable to move the throttle valve in one direction to increase fuel supply to the engine, and in a return direction to decrease the fuel supply, a control unit which senses the throttle valve condition, and a hydraulic actuator responsive to the control unit to move the throttle control valve independently of the cable. The hydraulic actuator is secured to an end of the cable adjacent the throttle control valve and is operable to vary the effective length of the cable.

Such a control system is disclosed in our

co-pending application GB9304484.0.

A problem associated with such a system is that when the throttle valve is closed independantly of the accelerator pedal controlled cable, the driver will perceive a change in load at the accelerator pedal. The present invention provides a means of ensuring that the driver feels no load change at the accelerator pedal .

Accordingly there is provided a control operable to position a member and which includes a command means connected through a control path to position the member which moves against a first resilient bias, an independently signalled actuator which acts to overide the command means, a further resilient biasing means disposed between the actuator and the command means to act in concert with the first resilient bias to exert a load on the command means such that the total resilient load acting on the command means remains substantially constant when the actuator is operating to overide the command means.

Preferably the command means is a operator controlled means, such as a accelerator cable, and the actuator

means when operating overides the operator's intention.

Such a system is useful for controlling the fuel supply of a petrol or diesel engined vehicle by, for example, control of the throttle valve of a petrol engine or a fuel injection pump of a diesel engine.

The actuator is preferably signalled via a control unit which senses the throttle valve or injection pump condition and a signal indicating that a fuelling reduction is required (for example to permit a gear change), and the actuator is responsive to the control unit to operate the throttle valve or injection pump to decrease fuel supply independently of the operator controlled means.

Preferably the operator controlled means (eg a cable) is connected to the throttle control valve or injection pump through a three bar linkage, a first bar being connected with the operator controlled means, a third bar connected with the throttle control valve or injection pump, and a second bar interlinking the first and third bars.

The invention will be described by way of example and

with reference to the accompanying drawings in which:

Fig 1 is a diagramatic representation of an internal combustion engine with a semi-automatic transmission and a control arrangement according to

the invention which controls a fuel supply of the engine, and

Figs 2 to 4 are schematic drawings of a portion of the fuel supply control showing the operation of a load compensation device on an operator controlled throttle cable.

With reference to Fig 1 of the accompanying drawings, an internal combustion engine is shown at 2, attached to a semiautomatic transmission 4 of the type described in GB 088 007 and EP-A-366-665 for a motor vehicle. The transmission comprises a clutch (not shown), for example a diaphragm spring clutch, within a bell housing 6 and a change speed gearbox 8 having an output shaft 10 for supplying rotary drive to one or more road wheels, and a rotary motion input shaft (not shown) on which is mounted in known manner a clutch driven plate. Gearbox 8 comprises a plurality of individually

selectable gear ratios any one of which is selectable ( in the course of a driver making a gear change ) by a suitable predetermined manual movement of a gear shift lever 12 to disengage or deselect the currently selected ratio and then select or engage the next desired gear ratio.

A control for automatically engaging and disengaging the clutch comprises an electronic microprocessor control 14 and a clutch control 16.

The clutch is disengaged and re-engaged using a release iever or fork 18 pivoted at 20 and interacting in known manner with the clutch. A fluid pressure piston and cylinder actuator 22 acts on the lever 18 so that the rate and degree of engagement or disengagement of the clutch at any instant is controlled by the amount of fluid in the actuator 22. The amount of fluid, which may be hydraulic fluid, acting in actuator 22 is controlled by a hydraulic fluid pressure supply and control system 24, which forms the clutch control 16 with the actuator 22.

Shift lever 12 includes a shaft 26 provided with a known gear lever pivot 28 permitting the shift lever a

degree of universal movement. Shaft 26 is connected by any means 30 known per se for conveyin movement of the shift lever 12 to a selection crank arm 32 causing selection and de-selection of any desired said gear ratio when the shift lever 12 is moved according to the gear shift pattern. In addition to the shaft 26 the gear shift lever 12 also comprises a tube 34 (shown in section) surmounted by a knob 36. Tube 34 is mounted by a pivot 38 on the shaft 26. Knob 36 is intended for application of manual force directly thereto by the hand of the driver, for changing gear. When no manual force is applied the tube 34 adopts a centralised or initial position with respect to the shaft 26 under the action of resilient means (not shown) acting between the shaft and tube. On the other hand when sufficient manual force is applied to the knob 36 the tube 34 initially tilts slightly relative to the lever 26, about pivot 38, before the lever 26 is moved by further force on the tube to move the selection crank arm 32. This initial tilting of the tube 34 is taken as indicating a wish by the driver to change gear, and tilt sensor means 40 give a tilt signal on channel 42 when a tilt has occurred. In response the electronic control 14 gives an output disengage clutch signal on channel 44 to reduce

torque by closing throttle before disengaging causing clutch control 16 to automatically disengage the clutch. Thereafter, selection of any desired gear ratio is observed by sensor 46 providing a gear selection completed signal on channel 48. In response the control 14 gives an output re-engage clutch signal on channel 44 causing the control 16 to automatically re-engage the clutch.

In a modification the fluid flow control 16 may be replaced by another controllable force producing arrangement acting on the release lever 18. For example the release lever 18 may be moved by an electric control system comprising an electric motor operated in accordance with signals from the electronic control 14.

A speed sensor 50 is provided to send to the electronic control 14 a signal on channel 52 representing the instantaneous speed of the engine.

Another speed sensor 54 is provided to send a signal on channel 56 representing the instantaneous speed of the input shaft of the gearbox 8.

The engine is supplied with fuel by fuel supply means 58, for example a carburettor, having a relatively stationary structure 60 relative to which other components can move. In the arrangement shown a lever 62 is pivotable about the axis of a shaft 64 which has a throttle control valve 64a (see Figs 2 to ) fixed thereto.

Pivoting the lever 62 in direction A opens throttle valve 64a causing an increase in the amount of fuel and air supplied to engine, whereas pivoting the leλ'er 62 in direction B towards an initial rest position closes throttle valve 64a causing the amount of fuel and air supplied to decrease. Restoring means in the form of a spring means 67 acts between the stationary structure 60 and the lever 62 to automatically urge the lever 62 in direction B thereby tending to close the throttle valve.

To normally pivot the lever 62 in direction A to open throttle valve 64a, when increased engine speed or output torque is required, the driver presses on an accelerator pedal 66 which is pivoted at 68 and is connected to one end portion 70b of a wire cable slidably extending through a guide sheath 72 from which

the other end portion 7ϋa of the cable emerges and is connected to the lever 62 through a three bar linkage 100 to be described later and shown on a larger scale in Figures 2 to 4. The sheath 72 and cable 70 form a Bowden cable one end of which is located by a stationery mounting 74 and the other end is held by a ferrule 76 which is normally held stationary on structure 60. The sheath 72 has a somewhat undulatory or meandering disposition.

Now with reference to Figs 2 - 4, the cable 70a is connected to the throttle valve 64a through the three bar linkage 100 which comprises a first bar 101 pivotally connected at one end to the cable 70a pivotted to the stationary structure 60 at a point 108, and pivotally connected at its other end to one end of a second bar 102. The other end of a second bar 102 is pivotally connected to a third bar 103. The third bar 103 is pivotally connected at a point 106 to a piston 81 of an actuator 80, preferably an hydraulic actuator, and at its other end is pivotally connected to a link 65 which is in turn pivotally connected with lever 62 for operation of the throttle valve 64a. The third bar 103 is substantially parallel to the first bar 101. A second resilient means 104 acts between the first bar

101 and the third bar 103. The second resilient means is preferably an extension sprin having one end attached to the pivotal connection 106 between the piston 81 of actuator 80 and the third bar 103, and its other end is attached to point 107 on the first bar 101 located substantially mid way between said one end of the first bar and the pivotal connection 108 to the stationary structure 60.

A strong compression spring 83 acts between the casing 84 of actuator 80 and piston 81 to ensure that the actuator remains in its retracted state, unless the actuator 80 is operated. Since casing 84 is fixed relative to structure 60, spring 83 effectively holds pivot 106 in a fixed position unless actuator 80 is operated.

The three bar linkage is shown in its throttle - closed condition in Fig 2.

If the accelerator pedal 66 is pressed the movement of the cable end 7ϋa causes the first bar 101 to pivot clockwise about the stationary structure 60 causing the second bar 102 to push the third bar 103 and cause it in turn to pivot clockwise about the pivotal connection 106 to the actuator 80 so that the third bar remains

parallel to the first bar. This in turn draws link 65 to the left, as shown in Fig 3, to pivot lever 62 in direction A to open the associated throttle valve 64a.

The movement of the bar linkage 101 from one parallelogram configuration of Fig 2 to the second parallelogram configuration Fig 3 is against the bias of the throttle spring 67 and the bias in the second spring 104 which is extended to a length LI which is greater than its original length. This total return load of springs 67 and 104 is felt by the driver through the accelerator pedal 66.

Lever 62 is operably connected to a position sensor 94, for example a rotary potentiometer, which provides a signal to control 14 on a channel 96 corresponding to the angular position of lever 62 or shaft 64 which is thus representative of the amount of fuel being supplied at any instant (which in the case of a carburettor is equivalent to the percentage that the throttle is open).

The hydraulic actuator 80 is connected via conduit 116 to an hydraulic pump in the control system 24. Assuming that the control 14 causes the hydraulic actuator 80 to be operated, by outputting a signal to

control system 24 on line 150, the movement of the piston 81 therein causes the third bar 103 to pivot about its end connection 109 to the second bar 102 and causes the throttle 64a to close. This has the effect of relieving the throttle return spring 67 but further extending the spring 104 to a length L2. Thus the extra bias load in the spring 104 balances the reduction in the bias load in the spring 67 so that the driver feels no change in load at the accelerator pedal, as the throttle control temporarily passes to the control 14. Spring 83 has no effect on the pedal load felt by the operator and is only acted against by the actuator 80.

For a more through understanding of the control operation the reader is directed to the Applicant's co-pending patent application 9304484.0.

Since the above described three bar linkage does not drive open the throttle, and since it retains and uses the throttle return spring the throttle can always return to an idle position in the event of a system failure.

Although the invention has been described above in detail with respect to the control of a throttle valve of a

carburetter fed petrol engine it will be appreciated that the member which is controlled may be the throttle valve of a fuel injected petrol engine or a fuel control element of a fuel injection pump of a diesel engine. Also the throttle valve or fuel control element may be rod as opposed to cable operated.