ELECTRONIC DISTRIBUTION BACKUP APPARATUS

Abstract: An auxiliary revolution sensor (l6) is disposed for detecting a reference position signal (l6a) of each cylinders. A computer (3) outputs an auxiliary reference cylinder signal (3d) by the reference position signal (l6a). A pseudo reference position signal generator (l2, l3, l4, l5) generates a pseudo reference position signal (l5a) by the auxiliary reference cylinder signal (3d). An electronic distributor (5) outputs ignition signals (6) to ignitors (6-ll) by outputting signals of the pseudo reference position signal generator and the computer, when a revolution sensor (l) is out of order.

Description: FIELD OF THE INVENTION This invention relates to a backup apparatus to cope with trouble of a sensor outputting a signal relating to the revolution of an engine, and more particularly to an electronic distribution backup apparatus suitable for an engine controlling apparatus equipped with an electronic distributor. BACKGROUND OF THE INVENTION When a sensor for sensing the revolution of an engine is in the event of failure, a conventional engine controlling apparatus becomes inoperative for control and the engine cannot be started. However, there is an increasing trend that a minimum necessary operation to secured even when part of a system is out of order. Particularly in the case of a controlling apparatus equipped with an electronic distributor, a proposal has been made in Japanese Patent Laid-Open No. 58-2469 (l983) published on January 8, l983 in the title of "Engine ignition control circuit" to output a pseudo ignition signal when part of a revolution sensor is out of order. However, the prior art technique explained above does not at all take backup means into consideration when the revolution sensor does not at all operate. Accordingly, the engine cannot operate at all. SUMMARY OF THE INVENTION An object of the present invention is to secure minimum necessary running even when the revolution sensor is out of order. The object of the invention explained above can be accomplished by disposing an auxiliary revolution sensor for detecting a reference position signal so that an output signal of a reference cylinder can be detected by the output signal of this sensor, a pseudo reference position signal is generated by the signal of the detected reference cylinder and the resulting pseudo reference position signal is inputted to an electronic distributor. According to the present invention, the trouble of the revolution sensor is detected by comparing a reference position signal with an angle signal and the reference position signal to be input to an electronic distributor is switched to the pseudo reference position signal described above. Then, an ignition signal is distributed to each cylinder and a car does not become inoperative. BRIEF DESCRIPTION OF THE DRAWINGS FIG. l is a block diagram showing one embodiment of the present invention; FIG. 2 is a block diagram showing in detail an electronic distributor shown in FIG. l; and FIG. 3 is a flow chart for explaining the operation of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. l, reference numeral l represents as revolution sensor; 2 is an input/output device; 3 is CPU; 4 is a change-over device; 5 is an electronic distributor; 6 through ll are igniters; l2 is a delay circuit; l3 and l4 are AND circuits; l5 is an OR circuit; l6 is an auxiliary revolution sensor; 2l is a starter; 22 and 23 are data bases; 24 is ROM; and 25 is RAM. The delay circuit l2, AND circuits l3, l4, OR circuit l5, and inverters connected between AND circuit l3 and the delay circuit l2 and connected between AND circuit l4 and CPU 3 constitute a pseudo reference position signal generator. The revolution sensor l generates a reference position signal la, for instance which is output at a predetermined angle before the upper dead point of the cylinder (e.g. ll0°), for sensing the reference position of each cylinder and an angle signal lb for sensing the angle of revolution of an engine, and these two signals are input to the input/output device 2. These input data are read by CPU 3 through the data bases. CPU 3 calculates an optimum ignition timing and an optimum power feed time to an ignition coil on the basis of these data. The result of calculation is sent to the input/output device 2 through the data bus 23 so as to output an ignition signal 2a. When the system operates normally, the ignition signal 2a is input to the electronic distributor 5 as a signal 4c through the change-over device 4. The reference position signal la and the angle signal lb are input to the electronic distributor 5 as signals 4a and 4b, respectively, through the change-over device 4. The electronic distributor 4 discriminates the cylinder which is to be ignited at present in sequence from the reference position signal la and the angle signal lb, and distributes the ignition signal 2a to an igniter 6 - ll of each cylinder. The ignition signal 2a output from the input/output device 2 is output based on the reference position signal la and the angle signal lb. When the revolution sensor l is out of order, a normal ignition signal 2a can not be output. The electronic distributor 5 distributes ignition signals to each cylinder. When the revolution sensor l is in trouble, the distribution by the electronic distributor 5 to each cylinder is impossible. At this time, CPU 3 detects the trouble of the revolution sensor l and outputs a change-over signal 3a for backup to the change-over device 4. Here, the trouble of the revolution sensor l is detected in the following way. (l) When a starter 2l operates and the engine is rotated at the start, a start signal 2la is input to CPU 3. If the reference position signal la and the angle signal lb are not input to CPU 3 through the input/output device 2 from the revolution sensor l even after the passage of a predetermined period (e.g. l sec) from the application of the start signal 2la to CPU 3, the revolution sensor l is judged as being in trouble. (2) The reference position signal la produces the same number of pulses as the number of cylinders while the engine rotates twice, and the angle signal lb produces pulses in accordance with the angle of revolution of the engine (such as one pulse for the revolution of the engine by 2°). At this time, the number of revolution N of the engine can be calculated in accordance with equation (l) below by measuring the pulse period of the reference position signal la: where N: number of revolution (rpm) T: pulse period (sec) of reference position signal la n: number of cylinders of engine. On the other hand, the number of revolution can be calculated from equation (2) below the counting the number of pulses generated by the angle signal lb for a predetermined period of time: where t: counting time of angle signal lb (sec) m: number of pulses of angle signal lb counted in the time t (sec) with the proviso that equation. (2) can be established only when the pulse of the angle signal lb is one pulse per revolution of engine by 2°. The numbers of revolution obtained by equations (l) and (2) are compared with each other, and the revolution sensor l is judged as abnormal when they are remarkably different from each other. When the abnormality of the revolution sensor l is detected in the manner described above at CPU 3, the backup change-over signal or the failure judging signal 3a is applied to the change-over device 4, and the reference position signal la, the angle signal lb and the ignition signal 2a to be input to the electronic distributor 5 are switched to the pseudo reference position signal l5a, the clock signal 3b generated from CPU 3 and serving as the base of the operations of CPU 3 and the input/output device 2 and the ignition backup signal 3c, respectively. The pseudo reference position signal l5a is generated by reading the period of the output pulse l6 of the auxiliary revolution sensor l6 by CPU 3 so as to discriminate the first cylinder as the reference cylinder, for example, calculating by AND circuits l3, l4 AND between waveforms l2a and l2b obtained by delaying the auxiliary reference cylinder signal 3d, which is output when the reference cylinder is discriminated, by the delay circuit l2, and further calculating OR by the OR circuit l5. Namely, pulses are generated at the rise and fall of the auxiliary reference cylinder signal 3d. FIG. 2 is a block diagram showing in detail the electronic distribution circuit 5. The angle signal 4a generates l80 pulses, for example, per revolution of the engine, and the reference position signal 4b is generated at a predetermined angle before the upper dead point of each cylinder (e.g. ll0°). This reference position signal 4b generates the same number of pulses as the number of cylinders, but contains a pulse wider than the pulses of the other cylinders in order to judge the ignition sequence of the reference cylinder. judgment of this reference cylinder is made by calculating AND of the two signals by the AND circuit l8, counting the pulses by the counter l9 and outputting the reference cylinder signal l9a when a predetermined number, for instance l5, of pulses are counted. The counter l9 is reset by a pulse generated by a rise detection circuit l7 which detects the rise of the reference position signal 4a that has passed through the change-over device 4. The reference cylinder signal l9a is applied to a shift register 20 and the reference cylinder signals l9a are sequentially shifted using the rise of the ignition signal 4c as the clock. The shifted signal is sequentially output to each cylinder in accordance with ignition order, and the ignition signal 4c is distributed to each of the igniters disposed for the corresponding cylinders as signals 6a to lla from AND with the ignition signal 4c. FIG. 3 is a timing chart showing the operation of the present invention. The auxiliary revolution signal l6a as the output of the auxiliary revolution sensor l6 generates the pulse at a predetermined angle before the upper dead point of each cylinder, but generates continuously two pulses only at the time of the reference cylinder. As a method of judging the reference cylinder from this signal, the period between each pulse is measured by CPU 3 and is compared with the period that has been measured previously. If the change from the previous period is remarkably great (such as below l/4 of the previous data), the reference cylinder is judged. At this time, the auxiliary reference cylinder signal 3d is set to "High" and is then set to "Low" when the next pulse is input. The auxiliary reference cylinder signal 3d is shifted by the delay circuit l2 using the clock signal 3b output from CPU 3 are the clock. The delay circuit l2 generates the clock shift signal l2a obtained by shifting about 20 clock signals and the shift signal l2b obtained by shifting about 5 clock signals. OR calculation is made by the OR circuit l5 for the AND signal between the inversed signal of the clock shift signal l2a and the auxiliary reference cylinder signal 3d and the AND signal between the shift signal l2b and the inversed signal of the reference cylinder signal 3d. In this manner, there can be obtained the pseudo reference position signal l5a which is the synthetic signal obtained by combining about 20 pulses of the clock signal 3b from the rise of the auxiliary reference cylinder signal 3d and about 5 pulses of the clock signal 3b from the rise of the auxiliary reference cylinder signal. The change-over signal 3a for backup is output when abnormality of the revolution sensor l is detected, and the input to the electronic distributor 5 is changed to the clock signal 3b output from CPU 3 in place of the angle signal lb, the pseudo reference position signal l5a in place of the reference position signal la and the ignition backup signal 3c, which is equal to 4c in FIG. 3, in place of the ignition signal 2a, respectively. Inside the electronic distributor 5, the counter l9 discriminates the reference cylinder from the pseudo reference position signal l5a and the clock signal 3b. Originally, when the revolution sensor l is normal, the reference cylinder is judged when the number of pulses of the AND signal between the reference position signal la and the angle signal lb is more than l5. Accordingly, the reference cylinder is judged when the first pulse of the pseudo reference position signal l5a has a pulse width which is substantially more than l5 clock signals 3b. If the width l2b of the second pulse from the delay circuit l2 is about 5 clock signals, the reference cylinder is not judged, so that the rise detection circuit l7 detects only the rise of the signal, and the counter l9 is reset to set the reference position signal l9a to "Low". When this reference position signal l9a is shifted by the shift register 20 using the fall of the ignition backup signal 3c as the clock, the ignition backup signal 3c can be distributed to each cylinder. As can be understood from the description given above, ignition for each cylinder can be backed up even when the revolution sensor l is out of order, and minimum necessary driving operation can be secured.

Claims: 1. An electric distribution backup apparatus comprising an electronic distributor (5) for sequentially distributing an ignition signal to each of igniters disposed so as to correspond to a plurality of cylinders of an engine on a basis of a reference position signal (la) for each of said cylinders in accordance with the revolution of said engine and on the basis of a rotating angle signal (lb) of said engine, characterized in that further comprising an auxiliary revolution sensor (l6) for detecting another reference position signal (l6a) of each of said cylinders when said revolution sensor (l) for generating said two signals is out of order; a calculator (3) for outputting a failure judging signal (3a) which is output by judging the failure of said revolution sensor (l) on the basis of the two signals (la, lb) from said revolution sensor (l), for outputting an auxiliary reference cylinder signal (3d) on the basis of a signal (l6a) from said auxiliary revolution sensor (l6), for outputting a clock signal (3b) in place of said rotating angle signal (lb), and for outputting an ignition backup signal (3c); and a pseudo reference position signal generator (l2, l3, l4, l5) for generating a pseudo reference position signal (l5a) in place of said reference position signal (la) on the basis of said auxiliary reference cylinder signal (3d); wherein said clock signal (3b), said pseudo reference position signal (l5a), and said ignition backup signal (3c) are input, when said revolution sensor (l) is out of order so that each of said igniters is ignited sequentially. 2. The electric distribution backup apparatus wherein further comprising a change-over device (4) for changing-­ over said reference position signal (la), said rotating angle signal (lb), and an ignition signal to said clock signal (3b), said pseudo reference position signal (l5a), and said ignition backup signal (3c), respectively, when said failure judging signal (3a) is input thereto.

Inventors: SASAKI, SHOJI
Applicants: HITACHI, LTD.
Application year: 1987
Main classification: F02P15
IPC codes: F02P7, F02P11, F02P15, F02P3, F02P5