GB2278935A

GB2278935A - Electronic control system

Info

Publication number: GB2278935A
Application number: GB9312040A
Authority: GB
Inventors: John Stamford
Original assignee: Perkins Ltd
Current assignee: Perkins Ltd
Priority date: 1993-06-11
Filing date: 1993-06-11
Publication date: 1994-12-14
Anticipated expiration: 2013-06-11
Also published as: GB9312040D0; GB2278935B

Abstract

An electronic control system particularly for use in an internal combustion engine comprises an electronic control unit (ECU) 19 for controlling actuation of peripheral devices, such as fuel injector solenoids. Low power control signals are sent over the wires 34 and command power device circuits 28, which are separately supplied with power from the power source 22, to energise the peripheral device 26. With this arrangement, the wires 34 need only conduct low power signals, the power device circuits 28 are located with the peripheral devices 26 instead of with the ECU 19, for better materials and heat management, and the ECU power supply 36 can be smaller and located outside the ECU housing. <IMAGE>

Description

AN IMPROVED ELECTRONIC CONTROL SYSTEM The present invention relates to an improved electronic control system and, in particular, an improved electronic control system for an internal combustion (i.c.) engine.

In the case of i.c. engines, ECU's are being increasingly employed in replacement of mechanical, electro-mechanical, hydraulic and pneumatic control systems to provide more reliable and faster control of engine performance and to provide interactive control which takes rapid account of variations in detected engine parameters.

Electronic control systems including a central electronic control unit (ECU) which is connected to a power supply means and has signal processing and control circuit means and power drive circuit means for controlling and actuating remote peripheral devices are known.

At present, it is normal to find that an electronic control system for an i.c. engine comprises a central ECU mounted on a side of an engine or within the engine compartment of a vehicle. The ECU includes processing and control circuit means for generating control signals in accordance with pre-programmed software and in response to detected engine parameters, and power drive circuit means responsive to said control signals for actuating, for example, fuel injector or pressure regulator solenoids connected to the ECU by power supply lines.

Whilst the known electronic control systems allow the power drive circuit means to be manufactured on the same printed circuit board (PCB) as the processing and control circuit means for mounting within a single housing, since the power drive circuit means are the single biggest generator of heat within the ECU, both the PCB and the ECU housing must be designed to have good heat dissipating characteristics which, of course, complicates their design and makes them more expensive to manufacture.

The known control systems may comprise different connection configurations depending upon the arrangement of the power drive circuit means and earthing considerations. The two most common configurations are a two-wire system comprising a battery voltage power supply line and ground return line between the ECU and each solenoid and a onewire system comprising a ground return line between the ECU and each solenoid and a common battery voltage power supply line connecting all of said solenoids. In each case, the power required to actuate a solenoid passes along the power supply line to ground via the ground return line connecting it to the ECU.

Another problem with the known systems is that due to the relatively high voltage high power operation of the power drive circuit means and the high power signals passing between the ECU and the solenoids, these components of the system can be extremely electrically noisy. This can lead to electro-magnetic compatibility problems affecting other electronic components mounted on the engine or within the engine compartment or even within the ECU itself, particularly the low voltage processing and control circuit means.

In addition, the main ECU input power supply connection and the power supply lines to the solenoids must be capable of handling the high voltage and current spikes inherent when controlling the actuation of high speed solenoids.

The length of the power supply and ground return lines between the ECU and the solenoids is dependent upon their relative locations on the engine but are, in any event, relatively long. This can lead to voltage drops along the lengths of these lines which must be taken into account when designing the control system for installation on a chosen design of i.c. engine.

Since the power supply and ground return lines between the ECU and their respective solenoids carry the high power waveforms required to actuate the solenoids, these lines must be well protected from short circuiting and from accidental damage that might occur during maintenance of the engine.

Design considerations such as these add to the overall cost of the system.

It is common for a manufacturer of i.c. engines to design an electronic control system for use with a variety of their engine designs. Suitable modifications can be made to the system for installation on a specific engine design. A control system designed to have general application to a number of engine designs must have a sufficient number of drive circuit means for any of the engine designs. When the system is installed on an engine having fewer devices to be actuated than the maximum number of drive circuit means available, this results in some drive circuit means being made redundant. Since the drive circuit means constitute a significant portion of the cost of the system, it is desirable to have as few redundant drive circuit means as possible.

It is an object of the present invention to obviate and mitigate the aforesaid disadvantages.

According to the present invention there is provided an electronic control system comprising an electronic control unit (ECU) connected to an input power supply means, said ECU including processing and control circuit means capable of generating control signals in accordance with predetermined control sequences and including a number of outputs respectively connected to remote peripheral devices, wherein each peripheral device is actuable by a power drive circuit means adjacent thereto in response to a control signal received from the ECU.

Preferably, each peripheral device and its adjacent power drive circuit means is connected directly to the input power supply means.

In the case where the control system is employed to control fuel injector solenoids in an i.c.

engine, each injector solenoid and its adjacent power drive circuit means may be mounted to a fuel cooled injector such that the fuel injector acts as a heatsink for the power drive circuit means.

The foregoing and further features of the present invention will be more readily understood from the following description of preferred embodiments, by way of example thereof, and with reference to the accompanying drawings of which: Figure 1 is a schematic block diagram of a first configuration of a known electronic control system; Figure 2 is a schematic block diagram of a second configuration of a known electronic control system; Figure 3 is a schematic block diagram of a first embodiment of an electronic control system according to the present invention; Figure 4 is a schematic block diagram of a second embodiment of the present invention; Figure 5 is a schematic block diagram of a third embodiment of the present invention; and Figure 6 is a schematic block diagram of a fourth embodiment of the present invention.

Referring to the drawings, figures 1 and 2 respectively show a two-wire configuration and a one-wire configuration for a known electronic control system 10 for an i.c. engine. The system 10 comprises an ECU 12 including processing and control circuit means (not shown) for generating control signals in accordance with predetermined control sequences and power drive circuit means (not shown) responsive to said control signals for actuating remote peripheral devices 14 such as pressure regulator or fuel injector solenoids connected to respective power supply lines 18. Both configurations are essentially the same with the exception that in the one-wire system the peripheral devices 14 are linked by a common battery voltage power supply line 18 rather than separately connected to the battery supply via the ECU 12.

In use, in response to a control signal, a selected power drive circuit means of the ECU 12 generates a power signal (as a high power high voltage waveform) which is communicated to a solenoid to actuate said solenoid, the power signal passing to ground via a ground line 20 connecting the solenoid to the ECU 12. This method of controlling actuation of solenoids has several disadvantages as aforementioned.

Figure 3 shows a schematic block diagram of a first embodiment of the present invention. This embodiment comprises an ECU 19 having an input 22 connected to a vehicle battery power supply (not shown) and a number of outputs 24 respectively connecting with a number of remotely located pressure regulator or fuel injector solenoids 26 and their adjacent power drive circuit means 28. The connection between each output 24 of the ECU 19 and a respective drive circuit means 28 of a solenoid 26 comprises a battery power supply line 30, a ground return 32 and an ECU control signal line 34.

The ECU 19 contains processing and control circuit means which generates control signals in accordance with predetermined control sequences whereby, in use, a selected solenoid 26 is actuated by its adjacent power drive circuit means 28 upon receipt of a low voltage control signal from the EQ. . The power drive circuit means 28 generates a high voltage high power voltage waveform to actuate the solenoid and draws its power from the battery supply line 30 connecting it with its respective output 24 from the ECU 19. Accordingly, the power voltage waveform required for actuating the solenoid does not come from the ECU 19 but is generated by the power drive circuit means 28 adjacent the solenoid 26 with the ECU 19 only generating a low voltage digital control signal.

Figure 4 shows a schematic block diagram of a second embodiment of the invention. Like numerals have been used to denote like parts. This embodiment differs from the first embodiment only insofar that the battery power supply to the power drive circuit means 28 adjacent each solenoid 26 is taken directly from the main battery supply line 22 into the ECU 19 rather than via the ECU.

Similarly, figure 5 shows a further embodiment of the invention in which the power drive circuit means 28 of each solenoid 26 is grounded directly from the battery ground rather than via the ECU 19.

The only connection between the power drive circuit means 28 of each solenoid 26 and the ECU 19 is a low voltage control signal line 34.

The various embodiments of the invention as aforementioned have a number of advantages over known electronic control systems.

Since the power drive circuit means 28 for each solenoid 26 has been effectively removed from the ECU 19, the ECU housing (not shown) does not need to be so large to house the processing and control circuit means. Also, since the processing and control circuit means has a low voltage operation and does not therefore generate much heat, the housing does not need to be specifically designed to have good heat dissipating characteristics and can therefore comprise a simple design.

A further advantage of the various embodiments of the present invention is that the number of power drive circuit means 28 is identical to the number of solenoids 26 requiring separate actuation, and therefore there are no redundant power drive circuit means 28, thus reducing the cost of the system. In fact, since the processing and control circuit means is relatively inexpensive in comparison to the power drive circuit means, it is possible to design an ECU 19 which includes processing and control circuit means 28 for a large number of solenoids 26, even though, when installed with engines of various designs, parts of the control circuit means and ECU outputs 24 may be redundant.

Due to the short connecting leads between each solenoid 28 and its respective drive circuit means 26, it is possible to more easily electromagnetically shield the solenoid 26 and the drive circuit means 28 thus reducing problems encountered with electrical noise. In addition, the main ECU input power supply connector 22 and the solenoid power supply lines 30 do not have to handle the high current and high voltage spikes inherent when switching high speed solenoids and so do not have to be of such heavy guage. It is also simpler to protect the low current signal lines 34 extending between the ECU outputs 24 and solenoids 26 against short circuits and accidental damage.

The embodiment of figure 5 makes it possible to reduce to one the number of connecting wires between the ECU 19 and each solenoid 26 and, since the connecting wire is not required to carry high currents, it can be made of substantially narrower gauge wire.

Also, with the embodiment of figure 5, the ECU 19 no longer requires a high current power input and this allows the power supply module normally incorporated in the ECU 19 to be removed and placed elsewhere on the engine or in an engine compartment, as illustrated in the embodiment of figure 6. The power supply module 36 generates heat which must be dissipated and normally employs efficient, and therefore expensive, electronic components in its construction in order to minimise heat generation.

The power supply module 36 can be connected close to the vehicle battery, converting battery voltage to digital power supply levels, for example, 5 volts, to supply the ECU 19. The advantage of this would be that cheap, less efficient components could be used in the power supply module 36. Also power supply modules 36 could be separately supplied to suit nominal battery voltages for different vehicles thus allowing a degree of flexibility in the design of an electronic i.c. engine control system.

Claims

1. An electronic control system comprising an electronic control unit (ECU) connected to an input power supply means, said ECU including processing and control circuit means capable of generating control signals in accordance with predetermined control sequences and including a number of outputs respectively connected to remote peripheral devices, wherein each peripheral device is actuable by a power drive circuit means adjacent thereto in response to a control signal received from the ECU.

2. An electronic control system as claimed in claim 1, wherein each peripheral device and its adjacent power drive circuit means is connected directly to the input power supply means.

3. An electronic control system as claimed in claim 2, wherein the ECU is connected to an input power supply means via a power supply module which converts input power voltage to direct current voltage levels suitable for operation of the ECU.

4. An electronic control system as claimed in any preceding claim for use in an internal combustion engine, wherein the input power supply means is the vehicle battery power supply.

5. An electronic control system as claimed in claim 4, wherein the peripheral devices controlled by the ECU are fuel injector solenoids.

6. An electronic control system as claimed in claim 5, wherein each injector solenoid and its adjacent power drive circuit means is mounted to a fuel cooled injector such that the fuel injector acts as a heatsink for the power drive circuit means.

7. An electronic control system substantially as hereinbefore described with reference to figure 3 of the accompanying drawings.

8. An electronic control system substantially as hereinbefore described with reference to figure 4 of the accompanying drawings.

9. An electronic control system substantially as hereinbefore described with reference to figure 6 of the accompanying drawings.

9. An electronic control system substantially as hereinbefore described with reference to figure 5 of the accompanying drawings.

10. An electronic control system substantially as hereinbefore described with reference to figure 6 of the accompanying drawings.

Amendments to the claims have been filed as follows

1. An electronic control system for an internal combustion engine comprising an electronic control unit (ECU) connected to a vehicle battery power supply, said ECU including processing and control circuit means capable of generating control signals in accordance with predetermined control sequences and including a number of outputs respectively connected to remote peripheral devices, wherein each peripheral device is actuable by a power drive circuit means adjacent thereto in response to a control signal received from the ECU.

2. An electronic control system as claimed in claim 1, wherein each peripheral device and its adjacent power drive circuit means is connected directly to the vehicle battery power supply.

3. An electronic control system as claimed in claim 1, wherein the ECU is connected to the vehicle battery power supply via a power supply module which converts vehicle battery voltage to direct current voltage levels suitable for operation of the ECU.

4. An electronic control system as claimed in any preceding claim, wherein the peripheral devices controlled by the ECU are fuel injector solenoids.

5. An electronic control system as claimed in claim 4, wherein each injector solenoid and its adjacent power drive circuit means is mounted to a fuel cooled inj ector such that the fuel inj ector acts as a heats ink for the power drive circuit means.

6. An electronic control system substantially as hereinbefore described with reference to figure 3 of the accompanying drawings.

7. An electronic control system substantially as hereinbefore described with reference to figure 4 of the accompanying drawings.

8. An electronic control system substantially as hereinbefore described with reference to figure 5 of the accompanying drawings.