US3910241A

US3910241A - Electronically controlled fuel injection system

Info

Publication number: US3910241A
Application number: US495125A
Authority: US
Inventors: Hideya Fujisawa; Norio Omori
Original assignee: NipponDenso Co Ltd
Current assignee: Denso Corp
Priority date: 1973-08-11
Filing date: 1974-08-05
Publication date: 1975-10-07
Anticipated expiration: 1992-10-07
Also published as: JPS5226285B2; DE2431559B2; DE2431559C3; JPS5037925A; GB1482594A; DE2431559A1

Abstract

An electronically controlled fuel injection system comprising a plurality of fuel supply systems one of which is connected with a part of fuel injection valves and the other is connected with the rest of the fuel injection valves, wherein one fuel supply system supplies fuel of lower pressure than the other thereby enabling the engine to operate with lean mixture for reducing harmful components in the exhaust gas of the engine.

Description

United States Patent 1191 1 1 3,910,241 Fujisawa et al. Oct. 7, 1975 [5 ELECTRONICALLY CONTROLLED FUEL 3,738,341 6/1973 Loos .7 123/32 EA INJECTION SYSTEM 3,745,768 7/1973 Zechnall et al... l23/l40 MC u 3,827,237 8/1974 Linder et al. 60/301 Inventors: HIdeya Flulsawa; Norm both 3,851,632 12/1974 Teshirogi et al. 60/276 of Kariya, Japan [73] Assignee: Nippondenso Co., Ltd., Japan Primary Examiner-Charles J. Myhre Assistant Examiner-Paul Devinsky [22] [Med 1974 Attorney, Agent, or FirmCushman, Darby & [21] Appl. No.: 495,125 Cushman Forelgn Application Prlority Data ABSTRACT Aug. 11, 1973 Japan 48-90299 An electronically controlled fuel injection system [52] US. Cl. 123/32 EA; 123/140 MC; /276; comprising a plurality of fuel supply systems one of 60/285 which is connected with a part of fuel injection valves [51] Int. Cl. F02B 3/00; FOZD l/06; FOlN 3/00 and the other is connected with the rest of the fuel in- [58] Field of Search... 123/32 EA, 32 AE, MC, jection valves, wherein one fuel supply system supplies 123/140 MP, 140 R; 60/276, 285 fuel of lower pressure than the other thereby enabling the engine to operate with lean mixture for reducing [56] References Cited harmful components in the exhaust gas of the engine.

UNITED STATES PATENTS 4 Cl 7 D F 3,576,182 4/1971 Howland 123/140 MC r s l US. Patent Oct. 7,1975 Sheet 2 of5 3,910,241

Sheet 3 of5 3,910,241

US Patent 0m. 7,1975

US. Patent Oct. 7,1975 Sheet 4 of5 3,910,241

US. Patent Oct. 7,1975 Sheet 5 of5 3,910,241

bl w m m m m m 2 .5 3 523 t 238 6E 201530 5 3 vs 221 E L ELECTRONICALLY CONTROLLED FUEL INJECTION SYSTEM BACKGROUND OF THE INVENTION v This invention relates to an improvement of an electronically controlled fuel injection system which is equipped with an oxygen content detector in the exhaust system to control the fuel injection in accordance with the oxygen content in the exhaust system, thereby reducing harmful components in the exhaust gas. The amount of oxygen in the exhaust gas varies with the value of air-fuel ratio as shown in FIG. 1 which the oxygen content detector detects to produce an electromotive force the characteristics of which has a peculiar point, as shown in FIG. 2, at the air-fuel ratio of about 14.8 which corresponds to the begining of oxygen curve in FIG. 1. The oxygen content detector has been well known from the early days. It was developed at first as a simple oxygen detector for general use and then it was utilized in an exhaust gas purifying system to detect the oxygen content in the exhaust gas, thereby controlling the air-fuel ratio at the intake system. The detector is made of such metal oxide as Zirconium dioxide and Titanium dioxide. The metal oxide becomes electrolytic when it is heated and it generates electromotive force when there is a difference of oxygen content between one side thereof and the other by the movement of oxygen ion.

In a conventional fuel injection system mounting such oxygen content detector, the air-fuel ratio can be controlled at no other value than 14.8. Because the detector applies the control signal generated therein to a computor, which operates to modify the injection pulse in accordance with the signal. The pulse modification is made by such a way that the air-fuel ratio always meets a value of about 14.8 to increase the fuel when the ratio is above 14.8 and decrease when below 14.8, thereby holding the value of about 14.8 continuously. At the point of about 14.8, the electromotive force of the detector changes abruptly as seen from FIG. 2, enabling the electrical treatment easy, although at the other points, the change rate of the output is not big, causing complexity of treatment.-

SUMMARY OF THE INVENTION With a view to overcome the problem described above, it is the primary object of the present invention to provide an electronically controlled fuel injection system which can control total air-fuel ratio to be set in the range which is different from the range of around 14.8 thereby to reduce harmful components in the exhaust gas of the engine more effectively. For example if the ratio is set at about 18.5, lower level of CO, BC and NOx emission can be obtained. It is the further object of the invention to provide a plurality of fuel supply systems in the fuel injection system with relatively simple construction and low cost.

The above and other objects, features and advantages of the present invention will be apparent from the following detailed description of preferred embodiments taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 shows a graph representing the relation between air-fuel ratio and two typical components in the exhaust gas.

FIG. 2 shows a graph representing the relation between air-fuel ratio and electromotive force generated in the oxygen content detector.

FIG. 3 shows a schematic plan view of the electronically controlled fuel injection system of the present invention.

FIG. 4 shows an electric diagram of computer of the fuel injection system of the present invention.

FIG. 5 shows an enlarged cross sectional view of fuel pressure regulator of the fuel injection system of the present invention.

FIG. 6 shows another embodiment of fuel supply system of the fuel injection system of the present invention.

FIG. 7 shows a graph representing the relation between air-fuel ratio and fuel pressure in' the fuel supply system of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT manifold, 17 a second exhaust manifold, 19 an oxygen content detector. The computer 1 controls to energize the

fuel injection valves

2 and 3 during suitable time period to inject suitable amount of fuel into an engine 21 in response to the signals from a vacuum pressure detector 23, crankshaft turning angle detector 25 and oxygen content detector 19. The angle detector 25 closes times per 1 engine cycle to inject the fuel simultaneously into every cylinders of the engine 21 2 times per one engine cycle from the fuel injection valves 2-and 3. The first fuel pressure regulator 9 regulates the pressure of the fuel discharged from the fuel pump 7 to supply constant pressure fuel to the fuel injection valve 2 which is mounted on the leftmost cylinder of the engine 21. The oxygen content detector 19 is mounted on the first exhaust manifold 15 which is connected with the said leftmost cylinder. The first fuel pressure regulator 9 is such construction as shown in FIG. 5, in which a diaphragm 27 is installed in a casing 29 with avalve seat 32 to divide the inner chamber into an upper and a lower chambers 31 and 33, and a coil spring 35 is installed in the lower chamber 33, and a projecting pipe 37 is installed in the chamber 31 with a valve portion 39 which faces the valve seat 32. The upper chamber 31 is connected with the fuel pump 7 through a fuel pipe 41 and the fuel injection valve 2 through a fuel pipe 43 thereby to introduce the fuel discharged from the fuel pump 7 and discharge it to the fuel injection valve 2.

The projecting pipe 37 is connected with the fuel tank 5 through a fuel pipe 45 to discharge the fuel from the upper chamber 31 to the fuel tank when the fuel pressure goes up to push the diaphragm 27 downward to separate the valve seat 32 from the valve portion 39.

The lower chamber 33 is connected with an intake pipe 47 of the engine 21 through a vacuum pressure pipe 49 to lead the vacuum pressure produced in the intake pipe 47 thereto. Therefore, the diaphragm 27 together with the valve seat 32 moves in response to the fuel pressure and vacuum pressure to control the fuel amount returning to the fuel tank from the upper chamber 31, thus regulating the fuel pressure. The

pressure of the fuel depends on the characteristic of the coil spring 35 as well.

The second fuel pressure regulator l 1 is similar to the said first fuel pressure regulator 9, except that the spring constant of the coil spring of the second fuel pressure regulator 11 is selected smaller than that of first fuel pressure regulator so that the second fuel pressure regulator 11 regulates the fuel pressure at a lower value than that of the first fuel pressure regulator 9. Therefore the lower pressure fuel i.e., the less amount of the fuel is supplied by the respective fuel injection valves 3 than that supplied by the leftmost injection valve 2, through the fuel distributor l3 and fuel pipes 51 into the cylinders equipped with the fuel injection valves 3 upon energizing both of the

fuel injection valves

2 and 3 with the same time period.

As the oxygen content detector 19 transmits its signal to the computer 1, the computer keeps the air-fuel ratio of the leftmost cylinder at about 14.8, by controlling the injection time of the fuel injection valve 2. On the other hand, in the rest of the cylinders equipped with the fuel injection valves 3, less fuel is injected, thus to make the air-fuel ratio larger than that of the leftmost cylinder.

A relation between air-fuel ratio and regulated fuel pressure for a 4-cycle and 6-cylinder engine is exemplificd in FIG. 7, wherein the air-fuel ratio of the cylinder connected with the fuel injection valve 2 is controlled at 14.8, the fuel pressure in the fuel pipe 43 is regulated at 2.55 kg/cm and the rest of the five cylinders are supplied with less amount of fuel respectively. As seen from FIG. 7, the total air-fuel ratio is controlled to be almost equal to that of lean cylinders connected with the fuel injection valves 3. For example, if the total airfuel ratio of about 18.5 is expected to eliminate harmful components in the exhaust gas, the fuel injection valves 3 should be provided with the fuel of about 1.5 kg/cm making the air-fuel ratio of the cylinders connected with the valves 3 at about 19.2. Consequently, the engine 21 as a whole is operated with lean mixture, which reduces harmful components in the exhaust gas with the resultant increase of the performance of the catalytic converter as well.

FIG. 6 is another fuel supply system, which is also available. Numeral 53 designates an intermediate fuel pipe connecting a first pressure regulator 55 with a second fuel pressure regulator 57, which correspond respectively to the aforesaid first and second fuel pressure regulators 9 and 11. A fuel pipe 59 is connected with the fuel tank to return overflowing fuel thereto. A fuel pipe 61 is connected with the leftmost fuel injection valve 2 and a fuel pipe 63 is connected with the fuel injection valves 3. Numeral 65 designates a fuel pump which is exactly same to the fuel pumps 7 and 8 of the aforesaid system. A coil spring 67 of the second fuel pressure regulator 57 is smaller in the spring constant than a coil spring of the first fuel pressure regulator 55 so that the fuel injection valves 3 inject less fuel than the valve 2 in the same manner as that of shown in FIG. 3.

Next, construction and operation of the computer 1 will be explained with reference to FIG. 4. Numeral 71 designates a wave shaping circuit while is connected with the crankshaft turning angle detector 25. The wave shaping circuit comprises resistors 71a, 71b, 71c and 71d, a capacitor 71g, NAND circuits 71f, 71d, 7 1i and 71j, a transistor 7le. The NAND circuits 71i and 711' constitute a flip-flop circuit. When the crankshaft turning signal is generated, the wave shaping circuit 71 generates a rectangular signal which is syncronized with the crankshaft rotation. Numeral 73 is an integrating circuit which comprises

resistors

73a, 73b, 73d and 73f, a transistor 730, a capacitor 73e, diodes 73g and 7311 and an operational amplifier 731'. The integrating circuit 73 performs its integration when the output signal of the NAND circuit 71j is in the 0 state and is reset when the signal is in the 1 state. Numeral 75 is a voltage regulating circuit which comprises a resistor 75a and a Zener diode 75b. The voltage regulating circuit provides the constant voltage, which is integrated by the integrating circuit 73. Numeral 77 is a control circuit which comprises

resistors

77a, 77f, 77g and 77h, operational amplifiers 77b and 771'. The operational amplifier 77b amplifies the output signal of the oxygen content detector 19, while the other amplifier 77i adds the both output signals of the vacuum pressure detector 23 and the operational amplifier 77b. Numeral 79 is a comparator circuit comprising resistors 79a and 79b and a comparator 790 with the outputconnected to the input of the NAND circuit 71j. The comparator produces 1" signal as its output when the output voltage of the integrating circuit 73 is lower than the output voltage of the control circuit 77, while it produces when the former is higher than the latter. When the comparator produces 0 signal, the NAND circuit is rendered 1 state, thereby resetting the integrating circuit 73. Numeral 81 designates a driving circuit which comprises

resistors

81a, 81b, 81c, 81d, 81f, 81g and 811', and transistors 8le, 8111 and 8lj. The base of the transistor Sle is connected with the output of the NAND circuit 71 When the output of the NAND circuit 71 j is in the 1" state the transistor 81e is kept conductive and the transistors 8111 and 81j are kept nonconductive. However, once the crankshaft turning angle detector 25 generates a signal, it renders the NAND circuit 71] into 1 state, thus making the transistor 8le nonconductive and the transistors 81/1 and 81j conductive thereby to drive the

injection valves

2 and 3.

As noted above, the fuel injection is started when the crankshaft turning angle detector 25 generates a signal and interrupted when the comparator circuit produces a 0 signal, whereby the injection period is responsive to the signals of vacuum pressure detector 23 and the oxygen content detector 19, with the result that the fuel is controlled in response to'the vacuum pressure of the intake pipe 47 and the oxygen content in the first exhaust manifold 15.

In this computer, the vacuum pressure detector 23 can be replaced by an air-flow meter, which is installed in the intake pipe 47.

As described above, the fuel injection system of the present invention has two different fuel supply systems 1 each of which supplies the fuel of different pressure engine, a computor for energizing the fuel injection valves in response to oxygen content in the exhaust gas ejected from the engine and an oxygen content detector mounted in one of said exhaust manifolds of a selected number of cylinders of said engine comprising;

a first fuel pressure regulator connected with said fuel pump and a selected number of said fuel injection valves respectively mounted on said selected number of cylinders for regulating the pressure of the fuel at a predetermined value to supply the regulated fuel to said selected number of said fuel injection valves from said fuel pump and a second fuel pressure regulator connected with said fuel pump and the rest of said fuel injection valves respectively mounted on the rest of cylinders for regulating the pressure of the fuel at another predetermined value to supply the regulated fuel to said rest of said fuel injection valves from said fuel pump.

2. In combination with an internal combustion engine having first and second exhaust manifolds, an electronically controlled fuel injection system comprising;

a fuel pump for supplying the fuel to the system,

fuel injection valves mounted on cylinders of said engine for injecting the fuel into said cylinders,

a computor connected with said fuel injection valves for energizing the said valves in response to signals representing the operating conditions of said engine,

an oxygen content detector mounted in said first exhaust manifold of said engine connected with a selected number of said cylinders to supply the oxygen content signal to said computor as the signal representing the operating conditions of said engine,

a first fuel pressure regulator connected with a selected number of said fuel injection valves mounted on said selected number of said cylinders being led to said first exhaust manifold for regulating the fuel pressure at a predetermined value,

a second fuel pressure regulator connected with the rest of said fuel injection valves mounted on the rest of said cylinders being let to said second exhaust manifold which is separately mounted on said engine from said first exhaust manifold for regulating the fuel pressure at another predetermined value.

3. An electronically controlled fuel injection system as claimed in claim 2, wherein;

said first fuel pressure regulator comprises two chambers separated by a diaphragm from each other, one of which is connected with said selected number of said fuel injection valves and said fuel pump and provided with a discharge pipe for discharging the fuel therefrom and the other is connected with an intake pipe of said engine and provided with a spring for setting the pressure of the regulated fuel at said predetermined value and said second fuel regulator comprises two chambers separated by a diaphragm from each other, one of which is connected with the said rest of said fuel injection valves and said fuel pump and provided with a discharge pipe for discharging the fuel therefrom and the other is connected with said intake pipe of said engine and provided with a spring having another spring constant for setting the pressure of the regulated fuel at said different predetermined value.

4. An electronically controlled fuel injection system as claimed in claim 3, wherein;

said second fuel pressure regulator keeps the fuel pressure at lower value than that of said first fuel pressure regulator, thereby making the total airfuel ratio larger than that of said selected number of said cylinders combined with said first fuel pres sure regulator.

Claims

1. In combination with an internal combustion engine having at least two exhaust manifolds, an electronically controlled fuel injection system having a fuel pump for supplying fuel to the system from a fuel tank, fuel injection valves for injecting the fuel into cylinders of said engine, a computor for energizing the fuel injection valves in response to oxygen content in the exhaust gas ejected from the engine and an oxygen content detector mounted in one of said exhaust manifolds of a selected number of cylinders of said engine comprising; a first fuel pressure regulator connected with said fuel pump and a selected number of said fuel injection valves respectively mounted on said selected number of cylinders for regulating the pressure of the fuel at a predetermined value to supply the regulated fuel to said selected number of said fuel injection valves from said fuel pump and a second fuel pressure regulator connected with said fuel pump and the rest of said fuel injection valves respectively mounted on the rest of cylinders for regulating the pressure of the fuel at another predetermined vaLue to supply the regulated fuel to said rest of said fuel injection valves from said fuel pump.

2. In combination with an internal combustion engine having first and second exhaust manifolds, an electronically controlled fuel injection system comprising; a fuel pump for supplying the fuel to the system, fuel injection valves mounted on cylinders of said engine for injecting the fuel into said cylinders, a computor connected with said fuel injection valves for energizing the said valves in response to signals representing the operating conditions of said engine, an oxygen content detector mounted in said first exhaust manifold of said engine connected with a selected number of said cylinders to supply the oxygen content signal to said computor as the signal representing the operating conditions of said engine, a first fuel pressure regulator connected with a selected number of said fuel injection valves mounted on said selected number of said cylinders being led to said first exhaust manifold for regulating the fuel pressure at a predetermined value, a second fuel pressure regulator connected with the rest of said fuel injection valves mounted on the rest of said cylinders being let to said second exhaust manifold which is separately mounted on said engine from said first exhaust manifold for regulating the fuel pressure at another predetermined value.

3. An electronically controlled fuel injection system as claimed in claim 2, wherein; said first fuel pressure regulator comprises two chambers separated by a diaphragm from each other, one of which is connected with said selected number of said fuel injection valves and said fuel pump and provided with a discharge pipe for discharging the fuel therefrom and the other is connected with an intake pipe of said engine and provided with a spring for setting the pressure of the regulated fuel at said predetermined value and said second fuel regulator comprises two chambers separated by a diaphragm from each other, one of which is connected with the said rest of said fuel injection valves and said fuel pump and provided with a discharge pipe for discharging the fuel therefrom and the other is connected with said intake pipe of said engine and provided with a spring having another spring constant for setting the pressure of the regulated fuel at said different predetermined value.

4. An electronically controlled fuel injection system as claimed in claim 3, wherein; said second fuel pressure regulator keeps the fuel pressure at lower value than that of said first fuel pressure regulator, thereby making the total air-fuel ratio larger than that of said selected number of said cylinders combined with said first fuel pressure regulator.