GB2394073A

GB2394073A - Engine management system

Info

Publication number: GB2394073A
Application number: GB0310538A
Authority: GB
Inventors: Michael Howes
Original assignee: DESCO RES Ltd
Current assignee: DESCO RES Ltd
Priority date: 2002-05-09
Filing date: 2003-05-08
Publication date: 2004-04-14
Also published as: GB0210591D0; GB0310538D0

Abstract

An engine management system comprises a control unit 18 arranged to receive signals indicative of the engine load from an engine load sensor 20 and of engine position from an engine position sensor 16 and to produce control signals, the system further comprising a fuel supply control unit 22 operable under the control of control signals produced by the control unit 18, and an ignition voltage generator 14 operable under the control of control signals produced by the control unit 18. Said ignition voltage generator may be an ignition coil. Said engine position sensor may comprise a contact breaker. Said fuel supply device may comprise a valve arrangement operable to control the supply of fuel to a carburettor. Said valves may be solenoid valves or driven by a stepper motor. Further disclosed is a carburettor comprising a float chamber defining a primary and secondary fuel flow path and a valve arrangement to control the flow of fuel along the secondary fuel flow path.

Description

Engine Management System This invention relates to an engine management

system, and in particular to an engine management system suitable for use with an internal combustion engine of 5 the type in which the fuel mixture is controlled using a carburettor and ignition timing is controlled by a contact breaker and a distributor.

Older style internal combustion engines in which Quelling and ignition are controlled using carburettors, contact breakers and distributors are in widespread use in a number of countries. Unfortunately, unless regularly serviced by a skilled 10 technician, such engines tend to operate relatively inefficiently due to the use of a poor fuel mixture and/or inappropriate ignition timing and can thus be uneconomic to run and produce unacceptably high levels of emissions. Even when serviced by a skilled technician, changes which occur between services may result in inefficient operation. It is an object of the invention to provide an engine management system 15 suitable for use with such engines. Another object ofthe invention is to provide an engine management system suitable for retrofitting to engines of this type.

According to the present invention there is provided an engine management system comprising a control unit arranged to receive signals indicative ofthe engine load from an engine load sensor and of engine position from an engine position 20 sensor and to produce control signals, the system further comprising a fuel supply control unit operable under the control of control signals produced by the control

unit, and an ignition voltage generator operable under the control of control signals produced by the control unit.

The engine position sensor conveniently comprises a contact breaker device driven by the engine. The ignition voltage generator may comprise an ignition coil.

5 The fuel supply control device preferably comprises a valve arrangement operable to control the supply of fuel to a carburettor.

The valve arrangement may comprise a solenoid operated valve arrangement, and may include a primary fuel flow path and a secondary fuel flow path, the solenoid operated valve arrangement including a solenoid operated valve located to lo control the flow of fuel along the secondary fuel flow path. A second solenoid operated valve may be provided to allow the flow of fuel along the secondary fuel flow path to be inhibited. The solenoid operated valve may be of the type in which the position of a valve member is controlled by a solenoid, or may be of the on/off type. Where the valve is of the on/off type, it is conveniently controlled so that the 15 ratio ofthe duration over which the solenoid is on to the duration it is off allows the fuel to be delivered at the desired rate.

lo. Rather than controlling fuel flow using an on/off type valve, a valve controlled using a small stepping motor may be used. Such a valve controls the fuel flow rate by controlling the degree by which the valve is opened at any given time.

20 The control unit may further be arranged to receive at least one additional signal from at least one other sensor, for example a sensor, eg a Lambda sensor,

arranged to monitor the level of at least one substance present in the exhaust emissions of the engine, and to control the ignition timing and/or Quelling of the engine using the additional signal.

The invention also relates to an engine including an engine driven contact 5 breaker, and a control unit operable using a signal produced by the contact breaker to control the operation of an ignition voltage generator.

The invention further relates to an engine including an engine load sensor and a control unit operable using a signal produced by the engine load sensor to control the operation of a fuel supply control device.

l o The invention will further be described, by way of example, with reference to the accompanying drawing (Figure 1) which is a diagrammatic view of an internal combustion engine incorporating an engine management system in accordance with one embodiment of the invention.

The engine illustrated diagrammatically in Figure 1 comprises an engine 15 block 10 defining a number of cylinders with pistons slidable therein in the usual manner. The engine is a petrol driven engine, thus each cylinder of the engine has *. associated therewith an ignition device in the form of a spark plug or the like. Each spark plug is connected to an output of a rotary distributor 12 which is driven by the engine, the distributor 12 being electrically connected to the spark plugs and an 20 ignition coil 14 or other ignition voltage generator such that, in use, the electrical discharge from the ignition coil 14 or other ignition voltage generator is supplied to

the spark plugs in turn to cause ignition of the fuel in the respective cylinders of the engine in the correct sequence for the correct operation of the engine. In a traditional engine of this type, a contact breaker device or similar device is used to control the exact timing of the operation of the ignition coil 14 to supply the 5 electrical current to the spark plugs, in turn, and hence to control the ignition timing.

In the arrangement illustrated in Figure 1, a contact breaker device 16 or similar device is still present, but rather than controlling the timing of ignition directly, the output ofthe contact breaker 16 is supplied to an electronic control unit 18. The control unit 18 is operable, as described hereinafter, to produce a control 10 signal which is supplied to the ignition coil 14 to control the operation thereof and hence to control the ignition timing. The contact breaker device l 6 is thus being used as an engine position sensor.

As well as receiving signals from the contact breaker 16, the electronic control unit 18 further receives a signal from a sensor 20 which is responsive to the 15 loading upon the engine. The sensor 20 may take the form of an intake manifold pressure sensor. It will be appreciated, however, that other types of sensor could be used to monitor the engine load at any given time, and the output of any such sensor could be supplied to the control unit 18 in accordance with the invention.

As well as controlling the ignition timing, the control unit 18 further supplies 20 output signals to a fuel supply control device 22 which is used to control the rate at which fuel is supplied to a fuel mixture supply device. Typically, the fuel mixture

supply device will take the form of one or more carburettors 24, although it will be appreciated that other forms of device for controlling the fuel air mixture may be used, if desired.

In one embodiment, the fuel supply control device 22 takes the form of two 5 valves controlled independently by separate control signals supplied from the control unit 18. A first one ofthe valves is a position controlled solenoid valve, the position of which is controlled by the control unit 18 to control the supply of fuel flowing to the main jet of the carburettor 24. Rather than supplying all of the fuel to the carburettor 24 through the valve, most ofthe required fuel is supplied directly to the 10 carburettor 24 in the usual way along a primary fuel flow path, the valve being used to provide a fine control over the quantity of fuel supplied by controlling the flow of fuel through a secondary flow path. The second valve takes the form of a cut off valve again operable by the control unit 18 to completely cut off the supply of fuel to the engine through the first of the valves, for example when a suitable sensor 15 indicates that the throttle is closed.

In normal use of the engine and engine control system, the control unit 18 e. holds the second, fuel cut off, valve of the fuel supply control device 22 in an open condition such that fuel can be supplied to the carburettor 24 and engine lo. The rate offuel supply is controlled by operation ofthe first valve ofthe device 22 under 20 the control ofthe control unit 18 using information derived from the intake manifold pressure sensor 20 or similar device, in combination with, for example, the throttle

of the engine. Signals from the contact breaker device 16 are used to provide the control unit 18 with signals indicative of the engine position. The control unit]8 determines, using information stored within the control unit 18, a desired ignition timing which may be dependent upon the load upon the engine and other factors.

5 The control unit 18 uses the output ofthe contact breaker 16 to determine the actual engine position at any given time and controls the operation ofthe ignition coil 14 to ensure that ignition occurs at the desired time. It will be appreciated, therefore, that if desired ignition timing may be advanced or retarded compared to what would otherwise be the case if the management system had not been present. The 10 information stored within the control unit 18 may take the form of a mapping of engine position against ideal ignition timing for a range of engine operating conditions, the control unit 18 selecting the most appropriate mapping using the engine load signal, and then using engine position information derived using the output ofthe contact breaker to control the ignition coil to cause ignition et the ideal 1 5 time.

Should there be a fault in the operation ofthe engine control system, then the control unit 18 will operate the fuel supply control unit to close the second, cut off, valve thereby terminating the supply of additional fuel to the engine under the control of the engine management system, operation of the engine reverting to its 20 normal operating mode, ie as if the engine management system were not present. It will be appreciated, therefore, that the engine management system is fail-safe.

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it will be appreciated that the system described hereinbefore may be modified in a number of ways. One way in which the system may be modified is to provide one or more additional sensors, the output signals of which are used by the control unit 18 in determining how the ignition timing and Quelling of the engine should be 5 controlled. For example, one or more of the additional sensors may be located to monitor the content ofthe exhaust emissions ofthe engine such that the control unit 18 can modify the ignition timing or fuel supply to the engine in response to the emission of particular substances exceeding certain predetermined levels. By way of example, a Lambda sensor may be used to monitor the oxygen content of the 10 exhaust gases, thereby allowing closed loop control over quelling levels.

Another way in which the system could be modified is to use a single solenoid operated valve in the fuel supply control device 22 to perform both the function of the first valve which controls the rate of supply of additional fuel and the second valve which serves to cut off the supply of additional fuel.

15 Although the system described hereinbefore makes use of a position controlled solenoid operated valve, an on/off type solenoid controlled valve may it. alternatively be used, if desired, the fuel flow rate being controlled by controlling the ratio of the time the valve is open to the time over which it is closed.

Another possibility is to use a valve the position of which is controlled using, 20 for example, a small stepping motor. it is thought that the use of a valve controlled in this manner permits an improvement in the consistent performance of the system.

As briefly mentioned hereinbefore, closed loop control may be achieved by monitoring the exhaust emissions, for example using a Lambda sensor, and using signals representative of the values of parameters associated with the exhaust gases in controlling fuelling and/or ignition timing. The invention may also be used in 5 conjunction with three-way catalyst technology to further enhance or improve the exhaust emissions of the engine.

it will be appreciated that with the system described hereinbefore, an existing internal combustion engine fitted within a vehicle may be retrofitted with the engine management system thereby perrnithng improved control over the efficiency of lo operation of existing internal combustion engines. Where used with an engine incorporating a carburettor, the valve arrangement may be located within a modified float chamber which can simply be substituted for that provided on a standard carburettor, the modified float chamber also defining the separate flow paths, fuel flow along one of which is controlled by the valve arrangement. Although the IS system is suitable for retrofitting to existing engines, it will also be appreciated that the system could be fitted to new engines of the type described, if desired.

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Claims

1. An engine management system comprising a control unit arranged to receive signals indicative of the engine load from an engine load sensor and of 5 engine position from an engine position sensor and to produce control signals, the system further comprising a fuel supply control unit operable under the control of control signals produced by the control unit, and an ignition voltage generator operable under the control of control signals produced by the control unit.

2. A system according to Claim 1, wherein the engine position sensor

l o comprises a contact breaker device driven by the engine.

3. A system according to Claim 1 or Claim 2, wherein the ignition voltage generator comprises an ignition coil.

4. A system according to any one of the preceding claims, wherein the fuel supply control device comprises a valve arrangement operable to control the 15 supply of fuel to a carburettor.

5. A system according to any one of the preceding claims, wherein the fuel supply control device includes a primary fuel flow path and a secondary fuel flow path, a valve arrangement being provided to control the supply offucl along the secondary fuel flow path, the valve arrangement being controllable by the control 20 unit.

6. A system according to Claim 5, wherein the valve arrangement

includes a solenoid operated valve located to control the flow of fuel along the secondary fuel flow path.

7. A system according to Claim 5, wherein the valve arrangement comprises a valve controlled using a small stepping motor.

5

8. A system according the any one of Claims 5 to 7, wherein the primary and secondary fuel flow paths are defined within a float chamber, the valve arrangement being located at least in part within the float chamber.

9. A system according to any one of the preceding claims, wherein the control unit is farther arranged to receive at least one additional signal from at least lo one other sensor and to control the ignition timing and/or Quelling of the engine using the additional signal.

10. An engine including an engine driven contact DreaKer, gnu UllUUl unit operable using a signal produced by the contact breaker to control the operation of an ignition voltage generator.

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11. An engine including an engine load sensor and a control unit operable using a signal produced by the engine load sensor to control the operation of a fuel supply control device.

12. A carburettor composing a float chamber defining a primary fuel flow path and a secondary fuel flow path, and a valve arrangement arranged to control the zo flow of fuel along the secondary fuel flow path.

13. A carburettor according to Claim 1z, wnerem Ine VillV Hill

14. A carburettor according to Claim 12, wherein the valve arrangement comprises a valve controlled using a small stepping motor.

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