Engine Control Systems

Abstract

An engine control system, particularly for a road vehicle, includes two transducers for producing two signals representing any two of the parameters engine speed, manifold pressure and throttle angle. These signals provide input to a matrix which gives an n-bit output determined by both input signals, where n is at least two. This output controls an engine characteristic. This invention relates to engine control systems generally, but is particularly concerned with engines used in road vehicles, where it is often required that the engine should be controlled to obtain some desideratum, for example minimum exhaust emission, maximum fuel economy or peak performance. The control will in most cases be of the injection of fuel to the engine, but can, in the case of an engine having a spark ignition system, be of the ignition timing, or even a combination of timing and fuel injection. In essence, the invention uses any combination of two parameters chosen from a group of three engine parameters, namely engine speed, manifold pressure (which of course can be a negative pressure) and through angle, to provide two signals. These signals provide inputs to a matrix, which can be a diode matrix or can use suitable semi-conductor devices other than diodes. The matrix is designed to give an n-bit output determined by both input signals, n being at least two, and this output is used to control an engine characteristic.

Description

The accompanying drawing is a schematic circuit diagram illustrating one example of the invention as applied to a spark ignition fuel injection internal combustion engine for a road vehicle.

Referring to the drawing, a signal is produced by any convenient transducer 8 representing one of the three variables, engine speed, throttle angle and manifold depression, the signal being produced in the form of a three bit binary word. Transducers are commercially available which will sense engine speed and produce an electrical output which can be provided in the form of a three bit binary word, and similar transducers are available for giving a three bit binary word representing throttle angle and manifold depression. The exact details of these transducers are not important to an understanding of the invention. Another three bit binary word is produced by another transducer 9 which responds to another of the three parameters, and the two words are fed respectively to a pair of decoders 11 and 12. There are 8 combinations of each digital signal, and for each input signal, the decoder 11 energizes one of eight input lines 13 of a diode matrix. The decoder 12 energizes one of eight output lines 14 depending on its input signal, and the lines 14 control a switching device 15 which can energize any one of eight groups of five lines 16 each of which crosses each line 13, with connections made where required by diodes which for simplicity are shown as dots. One output line 21 is connectible to the first line 16 in each group and four further output lines 21 are connectible to the other four lines 16 in each group, the lines 21 being coupled to a device 22 for controlling the supply of fuel to the engine 23. The dotted connections within the device 15 do not of course represent diodes.

The drawing shows only the diodes associated with the lines 13 and the first two groups of input lines 16, but by way of example it will be seen that, assuming 1 represents the interconnection of two lines 13, 16, then if the first group of lines 16 are energized and the eight lines 13 are energized in turn, the following output signals will be obtained: 10000, 00100, 01001, 01100, 10100, 10010, 11111, and 01000. Similarly, if the second group is energized, the output as the lines 13 are energized in turn will be 01100, 11001, 10101, 10000, 11001, 01101, 01111and 11000. It will of course be appreciated that the term "energized" as applied to a group of lines 16 means simply that the group of lines is in operation, that is to say is connected to the device 22. This can be achieved in numerous ways; for example, the switching device 15 can, on receipt of an input on a line 14, provide base current to five transistors serving through their collector-emitter paths to connect the appropriate group of five lines 16 to the lines 21. It is convenient to use metal oxide silicon (M.O.S.) transistor for this purpose, because they are readily integrated.

It will be appreciated that although a five bit output is obtained in the example, the value n in the claims can be from two upwards, depending on the accuracy required. Some outputs may be the same, indicating that the same fuel requirement is necessary for different operating conditions. The exact determination of the output for different inputs is made experimentally for a given engine, after which the same matrix can be used for all such engines. The signal, or a separately obtained signal, can be used to control the ignition timing, and in some instances the ignition timing alone can be controlled using as parameters engine speed and throttle angle. The way in which the quantity of fuel and/or the timing is controlled depends on the purpose of the control system, but the arrangement is particularly intended for minimizing exhaust emission.

The decoders 11 and 12 can take a variety of forms, and could for example include transistors of n-p-n and p-n-p varieties arranged so that a 1 signal turns on an n-p-n transistor and an 0 signal turns on a p-n-p transistor. The transistors are connected in sets of three in different n-p-n and p-n-p combinations with the collector-emitter paths of a set of three transistors between a voltage source and one of the lines 13 and 14, and the three bit words are fed to the bases of the transistors, so that for example the word 101 will cause conduction of the line 13 or 14 to which is connected in series with three transistors having the combination n-p-n, p-n-p, n-p-n. Conveniently, M.O.S. transistors are employed.

The diode matrix can be produced in integrated form starting with an n-type slice and diffusing into it p-type parallel rows which represent the lines 13. At the crossing points of the lines 13, 16, n-type zones are diffused into the strips to define diodes. Pair of conductive strips are then produced extending across the parallel rows and constituting the lines 16, and where a diode connection between a line 16 and a line 13 is needed, the appropriate strip is connected electrically to the n-type zone at the junction. It is, however, preferred to use M.O.S. transistors in the matrix to simplify production. Such a matrix conveniently has the rows 16 connected to a supply source through resistors respectively which block unwanted conduction paths. A connection is made where required from a line 13 to the drain of a M.O.S. transistor having both its source and gate connected to the line 16 to which the line 13 is to be connected. Such an arrangement can be made in a single diffusion starting with an n-type slice and diffusing parallel rows of p-type material for the lines 13, together with pairs of rows of eight separate p-type regions between the rows to constitute the lines 16. The slice is metallized so that each row is capable of constituting with its adjacent separate p-type regions M.O.S. transistors with interconnected gates and sources. The electrical connections are, however, only completed where a M.O.S. transistor is actually required to interconnect a line 14 and a line 16. The resistors can also be M.O.S. transistors, and so can the transistors used to interconnect the lines 16 and 21 as described earlier, so that the arrangement can be produced very simply in integrated form, particularly where as described earlier the decoders are constituted by M.O.S. transistors. It has been assumed that the system voltage allows p-type M.O.S. transistors to be employed, but if necessary n-type M.O.S. transistors can be used, or if a p-type diffusion is preferable to an n-type diffusion in manufacture, but the circuit requires n-type M.O.S. transistors, then a phase inverter can be used to allow p-type M.O.S. transistors to be employed. The phase inverter can itself be formed by pairs of p-type M.O.S. transistors, which are integrated with the rest of the circuit at very small cost and minimum inconvenience.

It will of course be appreciated that other known techniques can be employed to form the various circuits shown.

Claims

Having thus described our invention what we claim as new and desire to

1. An engine control system for controlling an engine characteristic comprising in combination a matrix unit having a first set of input lines and a second set of input lines arranged in groups of n lines, where n is at least two, with each line in the second set crossing each line in the first set, and connections being made between lines in the first and second sets in accordance with the engine characteristic being controlled and the nature of the required control, a first transducer producing a signal representing a first engine parameter, means whereby the output from the first transducer energizes one of the lines in the first set, depending on the value of the parameter, a second transducer producing a signal representing a second engine parameter, means whereby the output from the second transducer energizes one of the groups of n lines in the second set of input lines, and control means having n input connections the first of which is connectible to the first line in each group of n lines, the second of which is connectible to the second line in each group of n lines and so on, the arrangement being such that at any instant the energized group of n lines is connected to the control means so that for given values of the two engine parameters the control means receives a n-bit digital input signal, dependent on the interconnections between the energized line in the first set and the energized group of lines in the second set, the control means serving to control the engine characteristic in accordance with said input signal, and wherein the two engine

2. An engine control system for controlling an engine characteristic comprising in combination a matrix unit having a first set of input lines and a second set of input lines arranged in groups of n lines, where n is at least two, with each line in the second set crossing each line in the first set, and connections being made between lines in the first and second sets in accordance with the engine characteristic being controlled and the nature of the required control, a first transducer producing a signal representing a first engine parameter, means whereby the output from the first transducer energizes one of the lines in the first set, depending on the value of the parameter, a second transducer producing a signal representing a second engine parameter, means whereby the output from the second transducer energizes one of the groups of n lines in the second set of input lines, and control means having n input connections the first of which is connectible to the first line in each group of n lines, the second of which is connectible to the second line in each group of n lines, and so on, the arrangement being such that at any instant the energized group of n lines is connected to the control means so that for given values of the two engine parameters the control means receives a n-bit digital input signal, dependent on the interconnections between the energized line in the first set and the energized group of lines in the second set, the control means serving to control the engine characteristic in accordance with said input signal, and wherein the two engine

3. An engine control system for controlling an engine characteristic comprising in combination a matrix unit having a first set of input lines and a second set of input lines arranged in groups of n lines, where n is at least two, with each line in the second set crossing each line in the first set, and connections being made between lines in the first and second sets in accordance with the engine characteristic being controlled and the nature of the required control, a first transducer producing a signal representing a first engine parameter, means whereby the output from the first transducer energizes one of the lines in the first set, depending on the value of the parameter, a second transducer producing a signal representing a second engine parameter, means whereby the output from the second transducer energizes one of the groups of n lines in the second set of input lines, and control means having n input connections the first of which is connectible to the first line in each group of n lines, the second of which is connectible to the second line in each group of n lines and so on, the arrangement being such that at any instant the energized group of n lines is connected to the control means so that for given values of the two engine parameters the control means receives a n-bit digital input signal, dependent on the interconnections between the energized line in the first set and the energized group of lines in the second set, the control means serving to control the engine characteristic in accordance with said input signal, and wherein the two engine

4. An engine control system as defined in claim 1, wherein the engine

5. An engine control system as defined in claim 1, wherein the engine

6. An engine control system as defined in claim 2, wherein the engine

7. An engine control system as defined in claim 2, wherein the engine

8. An engine control system as defined in claim 3, wherein the engine

9. An engine control system as defined in claim 3, wherein the engine characteristic is the ignition timing of the engine.