FUEL SUPPLY CONTROL SYSTEM FOR AN ENGINE

Abstract: A fuel control system for an engine has an engine speed sensor (13, 31) for producing an engine speed signal, a sensor (18) for sensing the amount of lubricating oil in an oil pan of the engine and for producing an oil signal dependent on the amount of the oil. In response to the engine speed signal and oil signal, a means (35) produces a fuel supply cut-off signal when the engine speed exceeds a pred­ etermined engine speed above which bouncing of intake and exhaust valves of the engine would occur.

Description: FUEL SUPPLY CONTROL SYSTEM FOR AN ENGINE The present invention relates to a fuel supply control system for an internal combustion engine. A system in which the amount of fuel supplied to an internal combustion engine is calculated based on the amount of inducted air, speed of engine, and other parameters is known. When the engine speed exceeds a predetermined value, intake and exhaust valves begin to bounce, which will cause misfire and/or breakdown of the engine. In order to prevent such disadvantages, a fuel control system has a fuel cut-off system which operates when the engine speed exceeds a predetermined value which is slightly lower than the bounce beginning speed. However, in an automotive engine having a valve system provided with a hydraulic lash adjuster, the bounce beginning speed varies in accordance with the amount of lubricating oil. Especially, when the amount of oil in an oil pan reduces, bubbles caused by blowing gas enter into the oil for lubricating the valve system, which will cause malfunction of the valve system and lowers the bounce beginning speed. Consequently, in the conventional system, when the amount of oil reduces, the bouncing occurs before the fuel is cut off. In other words, the conventional system cannot prevent the bouncing when the amount of oil is reduced. The present invention seeks to provide a system which may prevent the bouncing of valves, even if amount of oil is reduced. Oil pressure for detecting apparatus for an internal combustion engine is known from US-A-4059087. In this specification, the engine speed and the oil pressure are determined and the engine is stopped if the oil pressure drops below a critical value. This value is not constant but depends on the speed of the engine. US-A-2023936 discloses a mechanical arrangement whereby, in the event of a drop in oil pressure, the speed of the engine is reduced considerably but not completely stopped. The purpose of this is to enable the engine to be operated at low speed for a limited time. According to the present invention, there is provided a fuel supply control system for an internal combustion engine having a fuel supply means and intake and exhaust valves provided with a hydraulic lash adjuster comprising means arranged to produce a speed signal proportional to the speed of the engine; sensing means arranged to produce an oil signal dependent on the amount of lubricating oil in the engine; and characterised in the provision of means storing data of maximum permitted engine speed as a function of the amount of lubricating oil in the engine and to which the speed signal and the oil signal are applied, said means producing a fuel cut-off signal when the engine speed as a function of the oil signal exceeds said permitted engine speed; and means responsive to the fuel cut-off signal to cut off the supply of fuel to the fuel supply means. In an aspect of the invention, the sensing means senses the amount of lubricating oil in the oil pan of the engine, and the predetermined engine speed for producing the fuel cut-off signal decreases with decrease of the amount of lubricating oil. A preferred embodiment of the invention will now be described, by way of example, and with reference to the accompanying drawings, wherein:­ Fig. 1 is a schematic diagram showing a system of the present invention; Fig. 2 is a block diagram of a control system of the present invention; Fig. 3 is a graph showing the relationship between amount of oil and engine speed for cutting off fuel; and Fig. 4 is a graph showing the relationship between engine speed and degree of bounce with respect to amount of oil. Referring to Fig. 1, an engine E has a throttle body 1 having a throttle valve 2 communicated with an intake pipe 3. In the intake system, an air cleaner 4, air flow meter 5, and compressor 20 of a turbocharger T are provided. In an exhaust pipe 21, an exhaust gas turbine 22 and a catalytic converter 23 are provided. Fuel is supplied to fuel injectors 8 from a fuel tank 9 by a fuel pump 10, and returned to the tank 9 through a passage 12 and a pressure regulator 11 which is opened by intake manifold vacuum applied through a pipe 12a. The engine E is provided with a throttle position sensor 14, coolant temperature sensor 16, and oil amount sensor 18 provided in an oil pan 17 for detecting the amount of lubricating oil in the oil pan. Output signals of the sensors 14, 16 and 18 are supplied to a control unit 15. The control unit 15 is further supplied with a signal from the air flow meter 5 and with a signal from an ignition coil 13. Referring to Fig. 2, the output signal of the ignition coil 13 is fed to an engine speed calculator 31 which produces an output signal dependent on engine speed, and the output signal of the air flow meter 5 is fed to an air flow calculator 30. Output signals of both calculators 31 and 30 are fed to a basic pulse width calculator 32 the output signal of which is applied to a fuel injection pulse width calculator 33. Output signals of throttle position sensor 14 and coolant temperature sensor 16 are also supplied to the calculator 33. The output signal of the oil amount sensor 18 and the output signal of the engine speed calculator 31 are fed to a look-up table 35 for fuel cutoff engine speed. The look-up table 35 stores data of maximum engine speeds with respect to amount of oil and produces a signal for cutting off the fuel supply. Fig. 3 shows an example of data, in which maximum engine speed increases from n2 to n4 with increase of amount of oil in the oil pan 17 from ℓ 2 to ℓ 4. Each maximum engine speed is decided to a value slightly lower than a value which causes the bounce of valves. Fig. 4 shows relationship between degree of the bounce and engine speed with respect to the amount of oil. The fuel cutoff engine speed is decided to a value which will cause the bounce larger than a predetermined value, for example 1mm. In operation, the calculator 32 produces a basic pulse width signal which is fed to the calculator 33. The calculator 33 corrects the basic pulse width in accordance with output signals of throttle position sensor 14 and coolant temperature sensor 16. The corrected fuel injection pulse width signal from the calculator 33 is applied to fuel injectors 8 through a driver 34 to inject the fuel to operate the engine. When engine speed exceeds a predetermined fuel cutoff speed dependent on the amount of oil in the oil pan 17, the look-up table produces a fuel cutoff signal. In response to the fuel cutoff signal, the calculator 33 produces a signal which represents that the fuel injection pulse width is zero. Thus, the fuel injectors stop injecting. Accordingly, the bouncing of valves can be prevented. Although the above described system is provided with fuel injectors, the invention can be applied to an engine having a carburetor. Further, the look-up table 35 may be replaced with a calculator for producing a fuel cutoff signal in accordance with the calculation of the amount of oil and engine speed. While the presently referred embodiment of the present invention has been shown and described, it is to be understood that this disclosure is for the purpose of illustration and that various changes and modifications may be made without departing from the scope of the invention as set forth in the appended claims.

Claims: 1. A fuel supply control system for an internal combustion engine having a fuel supply means (8, 32) and intake and exhaust valves provided with a hydraulic lash adjuster comprising means (13, 31) arranged to produce a speed signal proportional to the speed of the engine; sensing means (18) arranged to produce an oil signal dependent on the amount of lubricating oil in the engine; and characterised in the provision of means (35) storing data of maximum permitted engine speed as a function of the amount of lubricating oil in the engine and to which the speed signal and the oil signal are applied, said means producing a fuel cut-off signal when the engine speed as a function of the oil signal exceeds said permitted engine speed; and means (33, 34) responsive to the fuel cut-off signal to cut off the supply of fuel to the fuel supply means. 2. A fuel supply control system as claimed in claim 1, characterised in that the sensing means senses the amount of oil in the oil pan of the engine. 3. A fuel supply control system as claimed in claim 1, characterised in that the permitted engine speed for producing the fuel cut-off signal decreases with decrease of the amount of the lubricating oil.

Inventors: KOBAYASHI, TOMOYA
Applicants: FUJI JUKOGYO KABUSHIKI KAISHA
Application year: 1987
Main classification: F02D41
IPC codes: F02D41, F01M1, F01M11