This invention relates to a fuel supply control for an internal combustion engine whereby the amount of fuel supplied to the engine is variable.

In particular the invention is concerned with fuel supply controls in which a throttle control valve is operated by a cable from an operator controlled control member such as an accelerator pedal or lever.

In some semi-automatic transmission control systems, for example the systems described in GB-A-2088007 and EP-A-366665, it may be desirable for the throttle control valve to be operated independently of driver demand.

It is an object of the present invention to provide an improved form of fuel supply control which is suitable for use with such a semi-automatic transmission control system.

Accordingly there is provided a fuel supply control for an internal combustion engine, the supply controi comprising a throttle control valve, a cable connected to the control valve and which is operable under the control of an operator

controlled control member 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, the controi being characterised by the provision of a control unit which senses the throttle valve position, and an hydraulic actuator responsive to the control unit to move the throttle control valve to override the controi valve position currently set by the operator controlled control member. -

Preferably the hydraulic actuator is secured to an end of the cable adjacent the control valve and is operable to vary the effective length of the cable.

Alternatively the hydraulic actuator acts on one end of a shaft on which the throttle control valve is secured, and the other end of the shaft is connected to the cable through a torque limiting device, so that the actuator can rotate the shaft independently of the cable when the torque limiting device is overcome.

The invention will now be further described, by way of example, with reference to the accompanying drawings in which:-

Fig 1 is a diagrammatic representation of a fuel supply control according to the present invention used with a semi-automatic transmission for driving a motor vehicle;

Fig 2 is a view of an hydraulic actuator for operation of the throttle valve in the fuel supply control in Fig 1 ;

Fig 3 is a fragmentary section on line III-III in Fig 2 in combination with a position sensor;

Fig 4 shows a detailed section of the hydraulic actuator of Fig 2, and

Fig 5 shows a second hydraulic actuator for direct operation of a throttle control valve.

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-2088007 and EP-A-366665 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 mutually exclusively selectable gear ratios (known per se) any desired 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 said ratio currently selected and then select or engage any desired said gear ratio.

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

The clutch is disengaged and re-engaged using a release lever 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 conveying 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

including a lever in the form of a quadrant 62 which is pivotable about the axis of a rotatable pivot shaft 64 with which shaft the quadrant is fast. The shaft (64) may have a throttle control valve (butterfly valve) fixed thereto.

Pivoting the quadrant 62 in direction A causes an increase in the amount of fuel and air supplied to engine, whereas pivoting the quadrant in direction B towards an initial rest position causes the amount of fuel supplied to decrease. Restoring means in the form of a torsion spring means 65, shown in broken lines in Fig 2, acts between the stationary structure 60 and the shaft 64 to automatically urge the quadrant 62 in direction B thereby tending to return the quadrant to the initial rest position.

To normally pivot the quadrant 62 in direction A to increase the amount of fuel supplied 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 an end portion 70B of a wire cable slidably extending through a guide sheath 72 from which the other end portion 70A of the cable emerges and is connected to the quadrant 62. The sheath 72 and cable 70 constitute a Bowden cable. One end of the sheath 72 is located by a stationery mounting 74 and

the other end is held by a ferrule 76 which is normally held stationary but is moveable as will be described below. The sheath 72 has a somewhat undulatory or meandering disposition.

If desired, the aforesaid restoring means may also comprise resilient means 78 pulling on the pedal 66 so that the latter pushes the cable 70 through the sheath 72 to assist the spring 65 to pivot the quadrant 62 in direction B when the driver's foot pressure on the pedal decreases.

Ferrule 76 is held by an hydraulic actuator 80 which will be described in more detail with reference to Fig 4 and which is held in a support plate 102 bolted to structure 60. The cable portion 70A slidably emerges from the ferrule 76 and passes through a axial passage 86 in the piston 81 of the actuator 80. The piston 81 sealingiy slides in the bore 82 of an actuator cylinder body 83 and has a stem 89 passing through the end wail 84 of the body 83 and engaging the ferrule 76. The cable 70 passes through the bore 82 and through the open mouth 87 thereof and then extends in a groove 62A (Fig 4) in the quadrant to a cable nipple 88 caught in a notch in the quadrant. Secured to the quadrant 62 is a fork 90. A rotor arm 92 of a relatively stationary

position sensor 94 (Fig 4), for example a potentiometer, is engaged between the bifurcations of the fork 90. Thus the sensor 94 can provide a signal on a channel in line 96 (Fig 1) corresponding to the angular position of the quadrant 62 and thus representative of the amount of fuel being supplied at any instant (which in the case of a carburettor is in terms of the percentage that the throttle is open) .An elastomeric boot 96 extends between the- errule 76, where it locates on the piston stem 89, and the actuator body 83. The ferrule 76 could be screwed onto the piston stem 89 or otherwise secured thereto, and a piston return spring 97, which is stronger than the torsion spring 64 and therefore normally is not operable is located concentrically of the stem 89 and acts between the ferrule 76 and the actuator body 83 to bias the body 83 away from ferrule and thereby tend to reduce the length of the end portion 70A of the cable and open the throttle. The stem 89 engages a seal 98 in the end wail so that the piston 81 forms a fluid tight chamber 100 within the bore 82 between itself and the end wall 84. Fluid chamber 100 is connectable to a source of fluid pressure eg. a hydraulic pump through an inlet port 103 and conduit 116. The hydraulic pump may be part of the hydraulic fluid pressure supply and control system 24.

Assuming, say, that the accelerator pedal 66 is pressed so that the quadrant 62 has been moved in direction A (Fig 2) from the initial rest position with the result that the fuel supply means 58 is supplying an amount of fuel to the engine 2 greater than that supplied for idling, then if hydraulic pressure in the chamber 100 moves the piston 81 away from the end wall 84 in the direction b2, the end of the sheath 72 in the ferrule 76 will also be moved in direction b2. This will increase the length of the cable end portion 70A and consequently under urging by the said restoring means the quadrant 62 pivots in direction B to a new position causing the amount of fuel supplied to engine to be reduced, on the other hand if pressure in the chamber 100 is now reduced, the end of the sheath 72 in the ferrule 76 will be moved in direction a2 thereby pulling on the cable portion 70A which pivots the quadrant 62 to a new position in direction A causing the amount of fuel supplied to the engine to be increased.

The above operation allows the engine speed to be substantially matched with the speed of the input shaft of the gearbox 8 just before and as the clutch is automatically being re-engaged during a gear change once the new gear ratio has been selected. The control 14 is so programmed that,

when the clutch has been automatically disengaged and the new ratio selected, the control observes the engine speed signal and input shaft speed signal provided by the sensors 50 and 54, and if those speeds differ (or differ by more than a predetermined amount) the control issues a signal on channel 150 causing the fluid pressure supplied by control system 24 to the actuator 80 to move the piston and cause the quadrant 62 either to move in direction B to reduce the amount of fuel supplied and thus decrease the engine speed or to move in direction A to increase the amount of fuel and thus increase the engine supply means 58 is again wholly by the accelerator pedal 66.

In the case of changing up a gear, the next gear ratio selected is higher than the previous one. As a consequence, with the clutch disengaged, the momentum of the vehicle drives the input shaft of the gearbox 8 through the higher ratio and the speed of the input shaft is likely to be less than that of the engine, assuming that the driver continues to exert a constant pressure on the accelerator pedal 66. Therefore the control described above would act to decrease engine speed. In the event of the driver making a down change whilst the accelerator pedal is being pressed hard to give a large amount of fuel supplied, then when the clutch is

automatically disengaged the taking of the load off the engine, the throttle will have to close momentarily to reduce torque.

If desired the control 14 may be programmed to calculate the necessary decrease or increase in the amount of fuel supplied. The control 14 then sends a signal on channel 150 to change the volume of fluid in the chamber 100 by only a fraction (correlated to the size of the desired decrease or increase) of the possible maximum.

If required a position feedback device 104 (see Fig 4A or 4B) can be operated off the ferrule 76. The device consists of a single arm having one end pivotally fixed to a recess 105 in the ferrule and its other end connected to a potentiometer.

A second type of hydraulic actuator is shown in Fig 5 in this construction the hydraulic actuator 180 is secured adjacent the carburettor a throttle body 58 and acts directly on the end of the butterfly valve shaft 64. In this case the quadrant 62 will be located at the other end of the shaft 46 and will be operated by a throttle cable in conventional and well known manner. The quadrant 62 will be attached to shaft 64 through a torque control device 120.

The actuator 180 combines a cylindrical body 183 having a bore 182 with a piston 181 sealingly slidable in the bore 182 and forming a fluid chamber 200 therein between the piston 181 and an endwall 184 of the bore. The chamber 200 is connected to a source of fluid pressure through an inlet port 203. The piston 181 has a radial peg 190 which is slidable in an axial slot 191 in the body 183 so as to prevent rotation of the piston 181 relative to the body 183. The piston 181 is biased towards the end wall 184 by a spring 185 acting between the piston 181 and the other end wall 186 of the bore.

The piston 181 has a coaxial stepped bore 192 therein which has its larger diameter portion 193 adjacent the end wall 184, and a secondary piston 195 slidable within the larger diameter portion 193. The piston 195 acts on one end of a strut 196 which is in screw threaded engagement with the smaller diameter portion 194 of the bore 192 and is held coaxial of the bore 182 by a support 199. The strut 196 engages the end face 197 of the shaft 64 through friction. The strut 196 is biased away from the end face 197 by a spring 198.

On an initial application of hydraulic pressure the secondary

piston 195 overcomes the light return spring 198 and pushes the strut 196 into engagement with the end face 197. A further increase in pressure increases the clamp force on the end face 197 and axially displaces the other piston 181 causing the strut 196 to rotate (due to its screw-threaded engagement in bore 194) and hence the throttle shaft 64 is rotated by an amount dependent on the displacement of piston 181. The load on the torque device 120 must be overcome before the throttle shaft will turn independently of the throttle quadrant position