Stroke identification system for internal combustion engine

Abstract: A system comprising: a fuel supply member; first sensor means (107) for detecting predetermined angular positions of a drive shaft (111); second sensor means (112) for detecting predetermined angular positions of the shaft of an electronic ignition system distributor (113); means (104) for defining a sequence of signals (S, C) from the sensor means (107, 112); means (173) for memorising the sequence of signals (S, C); means (174, 175, 177, 185) for comparing the sequence of signals (S, C) in the current cycle with that of the previous cycle; means (177) for determining non-reception of a signal (C) from the second sensor (112) in accordance with the previous cycle sequence; means (178) for updating the current cycle sequence according to that of the previous cycle, in the event of non-reception of the signal (C) from the second sensor means (112); and processing means (102) for receiving signals relative to the updated sequence of signals (S, C) from the sensor means (107, 112); identifying the strokes of the engine (101); and enabling the electronic ignition system.

Description: The present invention relates to a system for identifying the strokes of an internal combustion engine. Internal combustion engine electronic ignition systems are known to feature an electronic control system for determining spark advance on the basis of signals received from various sensors (principally engine speed and stroke sensors). If said systems are also electronic injection types, on the basis of further signals (intake air pressure and temperature), the control system determines, for example, air density inside the manifold and engine speed, and calculates, via interpolation on respective memorised maps, the stroke of the engine and fuel injection time to the injectors. Said electronic ignition system employs angle references fitted on to the drive and distributor shafts to enable the control system to identify the stroke of each cylinder on the engine (intake, compression, expansion, exhaust). Current stroke identification systems employ angle references on the drive shaft, equal in number to the cylinders on the engine, and consisting, for example, of equally spaced projecting teeth. Said references are detected by a first sensor arranged facing them and which, every two references, and via the control system, enables an ignition command. Said system also requires a further stroke sensor for detecting the angle of an auxiliary shaft turning at half the speed of, but in strict time with, the drive shaft, and consisting, for example, of the camshaft or similar. In the event of a fault on the stroke sensor, the electronic ignition system becomes totally ineffective, thus resulting in stoppage of the engine, which can only be restarted by repairing the stroke sensor. The aim of the present invention is to provide an internal combustion engine stroke identification system designed to overcome the above drawback, i.e. which enables the engine to be operated even in the event of a fault on the stroke sensor. An internal combustion engine stroke identification system, comprising : a fuel supply member; an electronic ignition system featuring a distributor; first sensor means for detecting predetermined angular positions of a drive shaft; second sensor means for detecting predetermined angular positions of the shaft of said distributor; means for defining a sequence of signals from said first and second sensor means; and means for memorising said sequence of said signals is known from EP-A-204 221. According to the present invention, such a stroke identification system is provided with means for comparing said sequence of said signals in the current cycle with that of a previous cycle; means for determining non-reception of a said signal from said second sensor means in accordance with said sequence in the previous cycle; means for updating said sequence in the current cycle according to said sequence in the previous cycle, in the event of non-reception of said signal from said second sensor means; and processing means for receiving signals corresponding to said updated sequence of said signals from said first and second sensor means; identifying the strokes of said engine; and enabling said electronic ignition system. A preferred, non-limiting embodiment of the present invention will be described by way of example with reference to the accompanying drawings, in which: Fig.1 shows a schematic view of an electronic injection system for an internal combustion engine featuring the engine stroke identification system according to the present invention; Fig.2 shows a schematic view of certain components on the Fig.1 system; Fig.3 shows an operating block diagram of the system according to the present invention; Fig.4 shows a schematic view of a number of signals on the system according to the present invention. The system according to the present invention may be used on engines featuring an electronic ignition system with or without an electronic injection system. In the example shown, the engine also features an electronic injection system, i.e. a certain type of fuel supply, but, as will become apparent in the following description, the system according to the present invention also applies in the case of fuel supplied by an ordinary carburetor, providing, of course, provision is made for an electronic ignition system. Fig.1 shows a schematic view of an electronic injection system for an internal combustion engine 101, conveniently a four-cylinder engine, shown partially in cross section. Said system comprises an electronic control system 102 in turn comprising, in substantially known manner, a microprocessor 103 and memories containing maps relative to various operating conditions of engine 101. Control system 102 also comprises a counter 104; an updatable memory register 105; and an addressable-cell memory register 106. Control system 102 receives signals from: a sensor 107 for detecting the speed of engine 101 and located opposite a pulley 108 fitted on to a drive shaft 111; a sensor 112 for detecting the stroke of engine 101 and located inside a distributor 113; a sensor 114 for detecting the absolute pressure in the intake manifold 115 of engine 101; a sensor 116 for detecting the air temperature inside manifold 115; a sensor 117 for detecting the water temperature inside the cooling jacket of engine 101; and a sensor 118 consisting substantially of a potentiometer, for detecting the setting of a throttle valve 121 located inside intake manifold 115 and controlled by the accelerator pedal 122. An extra air supply valve 123 is provided parallel to throttle valve 121. Control system 102 is grounded and connected to a supply battery 124. On the basis of signals supplied to control system 102, engine speed and air density are used for determining fuel supply as a function of the required mixture strength. Control system 102 controls the opening time of electroinjectors 127 located inside manifold 115, close to the intake valve of each cylinder, for controlling fuel supply to the various cylinders on engine 101, and controls fuel injection timing for commencing fuel supply in relation to the stroke (intake, compression, expansion, exhaust) of engine 101. Electroinjector 127 is supplied with fuel via a pressure regulator 128 sensitive to the pressure inside intake manifold 115, and having a fuel inlet conduit 131 connected to a pump (not shown), and a return conduit 132 to a tank (not shown). Finally, control system 102 is connected to an ignition pulse control unit 133 connected to distributor 113. With reference to Fig.2, pulley 108 presents four projecting teeth 134 equally spaced at 90° intervals, and sensor 107 is arranged facing the passage of teeth 134, at such an angle as to detect passage, for example, +10° and +100° in advance of the top dead center position of each cylinder. Pulley 108 may be fitted so that said angles range respectively from +20° to +0° and from +110° to +90°, one pair of teeth 134 being square with the other. The sequence of signals (S) supplied by sensor 107 as drive shaft 111 rotates is shown in Fig.4a. Again with reference to Fig. 2, sensor 112 is arranged facing a disc 135 secured angularly to the shaft of distributor 113, and having two projecting teeth 136 ninety degrees apart. In particular, sensor 112 is located within the cylinder 3 range of distributor 113, and at such an angle that, when one tooth 134 is arranged facing speed sensor 107, the first tooth 136 on disc 135 lags 27.5° in relation to the axis of sensor 112. The sequence of signals (C) supplied by sensor 112 (Fig.4b) for each complete cycle of engine 101 presents a first signal 55° behind the foregoing signal from sensor 107 and, in the example shown, 135° ahead of the top dead center position of cylinder 3. The second signal supplied by sensor 112 as the second tooth 136 moves past it is 135° ahead of the top dead center position of cylinder 4, and 180° behind the first signal from sensor 112, in that, each complete turn of disc 135 corresponds to two turns of drive shaft 11 and, consequently, pulley 108. Operation of the system for identifying the strokes of engine 101 is described in the aforementioned EP-A-204 221, corresponding to Italian Patent n.1184958 entitled "Internal combustion engine stroke identification system" filed by the present Applicant on 4.6.1985, issued on 28.10.1987. As already stated, in the event of a fault on stroke sensor 112, the electronic ignition system becomes totally ineffective and engine 101 stops, and can only be restarted by repairing sensor 112. As explained in more detail later on, in the event of a fault developing on sensor 112 during operation of engine 101, the system according to the present invention enables operation of engine 101 to be continued on the basis of the operating cycle preceding that in which the fault is developed on sensor 112. Operation of the system for identifying the strokes of engine 101 will be described with reference to Fig.3. As shown in Fig.3, a repeat cycle starting block 170 goes on to a block 171 for enabling the S and C signal observation channels, and which goes on to a block 172 relative to an S and C signal identification routine. In the event of an S signal, block 172 goes on to block 173 and, in the event of a C signal, to block 174. Block 173 provides for updating counter 104 and memorising the S signal (Fig.4c), after which it goes on to block 175, which checks whether the signal received and certified in block 171 conforms with what has been updated on counter 104. For example (Fig.4c), if counter 104 starts from 0, the signal which should now be received is a C type. If an S type is received, this indicates non-conformance with counter 104. In the event of conformance with counter 104, block 175 goes on to block 176 and, conversely, to block 177. Block 176 provides for sequentially supplying the ignition pulses via unit 133 and, in the case of electronic injection systems, for also controlling fuel supply, after which it goes back to start block 170 for the next cycle. Block 177 checks whether a C signal should have been received and, in the event of a positive response, goes on to block 178. In the event of a negative response, block 177 goes on to block 181, which memorises the S signal error, which may be caused, for example, by a spurious signal. Block 178 provides for updating counter 104 as though a C signal had been received, after which it goes on to block 182 and, from there, to block 176. Block 182 provides for memorising the C signal error, i.e. the fact that a C signal has not been received. Block 174 checks the existence of a C signal error and, in the event of a positive response, goes on to block 183. In the event of a negative response, block 174 goes on to block 184, which provides for updating counter 104 and memorising the C signal. In other words, blocks 173 and 184 provide for mapping and memorising the S and C signal sequence in counter 104, so that block 178 in effect provides for taking and updating the reference map preceding the C signal error and defined in blocks 173 and 184. In the event of a fault developing on sensor 112 during operation of engine 101, this is therefore allowed to continue operating, thus enabling the user to arrive at his or her destination. Block 184 goes on to block 185 which, like block 175, determines whether the incoming signal conforms with the content of counter 104. If it does, block 185 goes on to block 176 and, if it does not, to block 186. Block 183 provides for deleting the C signal error in block 182, and block 186 for memorising the sequence error. Blocks 181, 183 and 186 go on to a resynchronizing routine which, on the basis of a predetermined number of S and C signals, identifies the various strokes of the cylinders. Said routine is shown in Fig.3 of EP-A-204 221. Blocks 181, 183 and 186 therefore go back to the start block shown in Fig.3 of EP-A-204 221. In the example shown of a four-cylinder engine, a number of teeth 134 equal to the number of cylinders, two teeth 136, a predetermined angular position of sensors 107 and 112, and a rotation speed of disc 135 equal to half that of pulley 108, counter 104 can count from 0 to 9. The time sequence of the output value from counter 104 is shown in Fig.4c. Counter 104 is incremented one unit for each signal received from sensors 107 and 112, and, when the maximum value (9) is reached, the next signal from sensor 107 sends the counter back to 0 in that the same signal cycle from sensors 107 and 112 and the same stroke cycle of engine 101 is repeated. The output value of 0 to 9 on counter 104 therefore identifies the strokes of engine 101, as described in EP-A- 204 220, corresponding to Italian Patent n.1184957 entitled "Startup fuel supply system for an internal combustion engine comprising an electronic injection system" filed on 4.6.1985 by the present Applicant, issued on 28.10.1987. Once the strokes of engine 101 have been identified, block 176 provides for sequentially supplying the ignition pulses via unit 133, while distribution to the various cylinders is performed by distributor 113. The advantages of the present invention will be clear from the foregoing description. In particular, it provides for overcoming malfunctioning of the stroke sensor during normal operation of the engine. In the absence of information relative to the engine stroke, this is ignored by the system according to the present invention, which continues operating, unlike known systems which suspend all outward activity and remain locked in a predetermined sync search cycle. In other words, the system according to the present invention assumes said information to be already verified, and therefore controls engine 101 on the basis of the map memorised prior to development of the fault on sensor 112. The system, however, keeps a close watch on operation of sensor 112 and, when this is restored, is once more synchronized with engine 101. To those skilled in the art it will be clear that changes may be made to the identification system as described and illustrated herein without, however, departing from the scope of the present invention as defined in the appended claims.

Claims: A system for identifying the strokes of an internal combustion engine (101), comprising : a fuel supply member; an electronic ignition system featuring a distributor (113); first sensor means (107) for detecting predetermined angular positions of a drive shaft (111); second sensor means (112) for detecting predetermined angular positions of the shaft of said distributor (113); means (104) for defining a sequence of signals (S, C) from said first (107) and second (112) sensor means, respectively ; means (173) for memorising said sequence of said signals (S, C); characterized by the fact that it comprises : means (174, 175, 177, 185) for comparing said sequence of said signals (S, C) in the current cycle with that of a previous cycle; means (177) for determining non-reception of a said signal (C) from said second sensor means (112) in accordance with said sequence in the previous cycle; means (178) for updating said sequence in the current cycle according to said sequence in the previous cycle, in the event of non-reception of said signal (C) from said second sensor means (112); and processing means (102) for receiving signals corresponding to said updated sequence of said signals (S, C) from said first (107) and second (112) sensor means; identifying the strokes of said engine (101); and enabling said electronic ignition system. A system as claimed in Claim 1, characterised by the fact that said means for defining said sequence of said signals (S, C) comprise a counter (104) incremented one unit for each said signal (S or C) from said first (107) and second (112) sensor means received by said processing means (102), and designed, for each increment, to supply said processing means (102) with a corresponding signal for defining said sequence of said signals (S, C) from said first (107) and second (112) sensor means; the content of said counter (104) being reset by each repetition of the cycle of said signals (S, C) from said first (107) and second (112) sensor means. A system as claimed in Claim 1 and/or 2, characterised by the fact that it comprises means (182, 183, 186) for memorising a possible error in the current cycle sequence of said signals (S, C) from said first (107) and second (112) sensor means as compared with the previous cycle sequence. A system as claimed in any one of the previous Claims, characterised by the fact that it is applied to a timed, sequential electronic injection system of an internal combustion engine.

Inventors: CONTICELLI CARLO, SERRA GABRIELE, CONTICELLI, CARLO, SERRA, GABRIELE
Applicants: MAGNETI MARELLI SPA, MAGNETI MARELLI S.p.A.
Application year: 1991
Main classification: F02P17
IPC codes: F02P7, F02P15, F02D41