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United States Patent (19) 11 United States Patent (19) 11. Patent Number: 4,503,479 Otsuka et al. 45 Date of Patent: Mar. 5, 1985 54 ELECTRONIC CIRCUIT FOR VEHICLES, 4,244,050 1/1981 Weber et al. .............. 364/431.11 X HAVING A FAIL SAFE FUNCTION FOR 4,245,150 1/1981 Driscoll et al. ................... 361/92 X ABNORMALITY IN SUPPLY VOLTAGE 4,306,270 12/1981 Miller et al. ...... ... 361/90 X 4,327,397 4/1982 McCleery ............................. 361/90 75) Inventors: Kazuo Otsuka, Higashikurume; Shin 4,348,727 9/1982 Kobayashi et al.............. 123/480 X Narasaka, Yono; Shumpei Hasegawa, Niiza, all of Japan OTHER PUBLICATIONS 73 Assignee: Honda Motor Co., Ltd., Tokyo, #18414, Res. Disclosure, Great Britain, No. 184, Aug. Japan 1979. Electronic Design; "Simple Circuit Checks Power-S- 21 Appl. No.: 528,236 upply Faults'; Lindberg, pp. 57-63, Aug. 2, 1980. (22 Filed: Aug. 31, 1983 Primary Examiner-Reinhard J. Eisenzopf Attorney, Agent, or Firm-Arthur L. Lessler Related U.S. Application Data (57) ABSTRACT 63 Continuation of Ser. No. 297,998, Aug. 31, 1981, aban doned. An electronic circuit for use in a vehicle equipped with an internal combustion engine. The electronic circuit (30) Foreign Application Priority Data comprises a constant-voltage regulated power-supply Sep. 4, 1980 (JP) Japan ................................ 55.122594 circuit, a control circuit having a central processing unit 51) Int. Cl. ......................... H02H 3/20; HO2H 3/24 for controlling electrical apparatus installed in the vehi 52 U.S. Cl. ...................................... 361/90; 123/480; cle, and a detecting circuit for detecting variations in 340/661; 364/431.11 supply voltage supplied from the power-supply circuit. 58) Field of Search ................................... 361/90, 18; The detecting circuit is adapted to generate an output 340/660-663; 323/276; 320/48; 123/479, 480; signal when the supply voltage of the power-supply 364/431.11, 431.05, 431.06 circuit is out of a predetermined range. The electronic circuit further includes circuitry responsive to the out 56) References Cited put signal of the detecting circuit to render the central U.S. PATENT DOCUMENTS processing unit inoperative and an alarm responsive to 3,506,967 4/1970 Foley ................................ 361/90 X the same output signal to give warnings. 3,663,958 5/1972 Crane ................................ 361/90 X 4,054,830 10/1977 Harrel ............................... 36/18 X 5 Clains, 3 Drawing Figures CARBURATOR 11 ENGINE CATALYST 02 SENSOR PRESSURE SENSOR SWITCH PRESSURE SENSOR ELECTRONIC 10 CONTROL UNIT U.S. Patent Mar. 5, 1985 4,503,479 EN19NE U.S. Patent Mar. 5, 1985 Sheet 2 of 3 4,503,479 (JENNOCH (JOHTOS U.S. Patent Mar. 5, 1985 Sheet 3 of 3 4,503,479 FIG 3 (i) (ii) (iii) (iv) CJBJW77][193B]}} (A)39VITOA TIME-- 4,503,479 1. 2 increased amounts of exhaust gas ingredients emitted ELECTRONICCIRCUIT FORVEHICLES, HAVING from the engine. A FAIL SAFE FUNCTION FOR ABNORMALITY IN SUPPLY VOLTAGE OBJECTS AND SUMMARY OF THE INVENTION This application is a continuation of application Ser. It is an object of the invention to provide an elec No. 297,998, filed Aug. 31, 1981 and now abandoned. tronic circuit for use in a vehicle, which is provided with a fail safe function for abnormality in the supply BACKGROUND OF THE INVENTION voltage, which comprises detecting deviation of the This invention relates to an electronic circuit for 10 supply voltage of the power-supply circuit from a pre controlling various electrical apparatus installed in a determined voltage range within which the component vehicle equipped with an internal combustion engine, devices can operate properly, and immediately render and more particularly to an electronic circuit of this ing the central processing unit of the electronic circuit kind which is provided with a fail safe function which is inoperative, and if necessary, performing an alarm ac executed in the event of the occurrence of abnormality is tion. The electronic circuit having the above function in the supply voltage. according to the invention, if applied to an air/fuel ratio Conventionally, there have been proposed a variety control system, can eliminate the possibility that the of control systems for controlling internal combustion air/fuel ratio is controlled to an abnormal value due to engines for vehicles, such as air/fuel ratio control sys malfunction of the central processing unit. tems, fuel injection systems, automatic transmission 20 It is a further object of the invention to provide an systems, and exhaust emission control systems. electronic circuit for use in a vehicle, which is con These control systems are each provided with an structed such that the central processing unit automati electronic control circuit, such as an electronic control cally resumes its normal operation upon the supply unit (ECU), which includes a central processing unit voltage returning to its normal value after the central (CPU). The electronic control circuit is arranged to 25 processing unit has been rendered inoperative due to control electrical apparatus which are installed in a abnormality in the supply voltage. Thus, abnormality in vehicle for performing their respective intended opera the supply voltage can be positively detected with no tions, in response to operating condition of an engine influence of mere power source noise or other disturb installed in the vehicle. 30 ances, to thereby allow continuation of the operation of For instance, according to an air/fuel ratio control a control system associated with the electronic circuit system, which has been proposed by the assignee of the even with the occurrence of such disturbances. present application, an air/fuel ratio control valve is According to the invention, there is provided an arranged in connection with fuel quantity adjusting electronic circuit for use in a vehicle which is equipped means such as a carburetor, for controlling the quantity 35 with an internal combustion engine and a power source, of air or fuel to be present in an air/fuel mixture being the electronic circuit comprising: a power-supply cir supplied to an internal combustion engine. An elec cuit for controlling a voltage supplied from the power tronic control unit (ECU) is used to drive the air/fuel source to a predetermined voltage; at least one electri ratio control valve by means of an actuator such as a cal apparatus installed in the vehicle; a control circuit pulse motor which forms one of the above-mentioned 40 arranged to be supplied with power from the power electrical apparatus, to perform feedback control of the supply circuit and having a central processing unit for air/fuel ratio of the mixture to a predetermined value in controlling the operation of the electrical apparatus; a response to an output signal produced by a sensor for detecting circuit arranged to detect voltage variations detecting the concentration of an exhaust gas ingredient in the power supplied from the power-supply circuit emitted from the engine. 45 and produce an output signal when the power has a Electronic control circuits used in or with various voltage lying out of a predetermined range; and means control systems inclusive of the above air/fuel ratio responsive to the output signal of the detecting circuit control system are usually formed of microcomputers. to render the central processing unit inoperative. The However, microcomputers in general are apt to have electronic circuit may further include means responsive their operations affected by variations in the supply 50 to the output of the detecting circuit to perform an voltage. To cope with this, a microcomputer is con alarming action. nected to a voltage regulated power-supply circuit for The above and other objects, features and advantages supplying the same with a regulated supply voltage, to of the invention will be more apparent from the ensuing ensure normal operation of the component devices of detailed description taken in connection with the ac the microcomputer so that the microcomputer can 55 companying drawings in which: properly perform its required control operation. Even with the above voltage regulated power-supply BRIEF DESCRIPTION OF THE DRAWINGS circuit, the possibility still exists that the supply voltage FIG. 1 is a block diagram illustrating the whole ar of the power-supply circuit becomes out of a predeter rangement of an air/fuel ratio control system for inter mined tolerable range at the low-temperature start of 60 nal combustion engines, to which is applicable the elec the engine or in the event of a failure in the power-sup tronic circuit according to the invention; ply circuit per se or a break in the related wiring. On FIG. 2 is a circuit diagram illustrating one embodi such occasion, the component devices of the electronic ment of the electronic circuit according to the invention control circuit do not normally operate. If the control which is provided with a fail safe function for abnormal operation is then continued without taking any emer- 65 ity in the supply voltage supplied to the electronic con gency measures, there can occur abnormality in the trol unit (ECU) in FIG. 1; and control operation, which can result in various disadvan FIG. 3 is a graph showing the operation of the elec tages such as inferior driveability of the vehicle and tronic circuit in FIG. 2. 4,503,479 3 4. Details of the air/fuel ratio control which can be DETAILED DESCRIPTION performed by the air/fuel ratio control system outlined Details of the invention will now be described with above will now be described. reference to the drawings which illustrate an embodi At the start of the engine, ECU 6 once moves the ment of the invention. 5 pulse motor to its reference position and then moves it Referring first to FIG.
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