Fuel supply systems for internal combustion engines

Abstract

A fuel supply system for an internal combustion engine comprises a pump feeding fuel to one or more injector nozzles. A digital electronic fuel control unit controls the flow of fuel to the nozzles in response to signals from a digital encoder whose output is dependent upon the angle of a vane controlling the admission of combustion air into the engine. The digital encoder includes an arm mounted on a spindle carrying the vane. The arm has a series of contacts thereon which move relative to fixed contact areas as the vane pivots with the spindle so that a digital output is obtained in accordance with the angle of the vane.

Description

This invention relates to fuel supply systems for internal combustion engines.

A fuel supply system in accordance with the invention includes a throttle valve for controlling the admission of combustion air to an engine and having an angularly movable spindle, a digital encoder for said throttle valve for producing a digital output corresponding to the angular position of the spindle, and a digital electronic fuel control unit responsive to the output of the digital encoder for controlling the rate at which fuel is supplied to the engine in accordance with the output of the digital encoder.

In the accompanying drawings

FIGS. 1 and 2 are diagrammatic representations of two examples of fuel supply systems in accordance with the invention, for an internal combustion engine, and

FIGS. 3 and 4 are mutually perpendicular sections through a throttle valve which can be employed in either system.

The system shown in FIG. 1 includes a digital electronic fuel control device 10 which controls the supply of fuel, pressurised by a pump 11, to injection nozzles 12 in an air intake manifold 13 of the engine. The digital control device 10 has inputs from a speed sensing device 14 and from a digital encoder 15 associated with a throttle 16 which controls admission of combustion air to the manifold 13 under the control of a pedal 17. The timing of the injections is controlled by a timing device 18. The quantity injected in each cycle is controlled by the device 10.

In the system shown in FIG. 2, a single spray nozzle 19 is used which sprays fuel into air intake downstream of the throttle. In this case, digital control device 20 is used to drive a variable speed electric motor 21 which drives a pump 22 supplying the nozzle 19. The rate of injection is controlled by the device 20.

In each case, the throttle valve 16 has a spindle 23 which is turned to move a vane 24 within a passage through the throttle valve body. An electrically insulating arm 25 is mounted on the spindle 23 and a row of contacts 26 on this arm 25 engage a printed circuit board 27 mounted on the body. One of these contacts is permanently in contact with an arcuate conductive area 27a on this board. The remaining contacts 26 run over arcuate rows of alternately conductive and non-conductive areas on the board 27, the conductive areas of each arcuate row being connected together and thereby to an associated one of a plurality of terminals 27b on the board. Thus, for any position of the spindle a predetermined number of the terminals 27b are connected to the area 27a and the remainder are isolated from the area 27a. Preferably the conductive areas on the board are arranged to give a Gray, coded digital output, as is already known in shaft encoders, so that only one output changes at any time as the spindle is turned.

The encoder 15 provides a digital input into the digital control device 10 or 20, which, taken in combination with the signal from the speed sensing device 14 determines the output of the device 10 to control the rate of fuel input.

Details concerning the digital fuel control circuits 10 and 20, speed centers 14, and timing device 18 may be found, for example, in U.S. Pat. No. 3,689,753, issued Sept. 5, 1972, to Williams et al and assigned to the same assignee as the present application, said patent being expressly incorporated herein by reference.

Claims

I claim:

1. A fuel supply system including a throttle valve for controlling the admissions of combustion air to an engine and having an angularly movable spindle, a digital encoder for said throttle valve for producing a digital output signal corresponding to the angular position of the spindle, and a digital electronic fuel control unit responsive to said output signal of the digital encoder for controlling the rate at which fuel is supplied to an engine in accordance with said output signal of the digital encoder, said encoder including an arm mounted for angular movement with the spindle, a plurality of contacts mounted on said arm, the number of said contacts corresponding to the number of bits of said digital output signal, and a plurality of fixed digitally coded contact paths equal in number to and arranged in a one-to-one contacting relationship with said contacts on said arm and relative to which the contacts on the arm are movable upon angular movement of the spindle so as to generate a plurality of different digitally coded output signals.

2. A fuel supply system as claimed in claim 1, including at least one fuel injector nozzle for supplying fuel to the engine, and wherein the fuel control unit is arranged to control the flow of fuel to the said at least one nozzle.

3. A fuel supply system as claimed in claim 2, wherein a pump is arranged to supply fuel to the control unit which controls flow of fuel therefrom to the said at least one nozzle.

4. A fuel supply system as claimed in claim 2, wherein a pump is provided for supplying fuel, and a variable speed motor controlled by the fuel control unit drives the pump.

5. A fuel supply system as claimed in claim 1, wherein one of the contacts on the arm is permanently in contact with an arcuate conductive area and other contacts on the arm are movable over arcuate rows of alternately conductive and non-conductive areas, the conductive areas of each arcuate row being connected to a terminal so that for any position of the spindle a predetermined number of the terminals are connected to the said arcuate conductive area and the remainder are isolated from the said arcuate conductive area.

6. A fuel supply system as claimed in claim 5, wherein the conductive areas are arranged so that only one output changes at any time as the spindle is turned.