US3724431A - Electromagnetic fuel injection device for internal combustion engines - Google Patents

Abstract

An electromagnetic fuel injection device for internal combustion engines comprising electric circuit so arranged that the number of cylinders which undergo simultaneous injection in one cycle of the engine is lessened at low rotational speeds where the control time of the amount of fuel injected is relatively long so as to operate all the fuel injection valves through several stages thereby the period of each fuel injection will not correspond to an overlapping period, while for high speed rotation the number of cylinders related to simultaneous injection is increased to equivalently extend said control time.

Description

O United SiiiiGS Patent 1 1 1 1 3,7 24,431

Inoue et al. [451 Apr. 3, 1973 54| ELECTROMAGNETIC FUEL 3,483,851 12/196) Rcichardt ..|23 32 EA INJECTION DEVICE FOR INTERNAL 2,992,640 7/1961 Knapp ..l23/32 EA 3,181,520 5/1965 .....l23/32 EA COMBUSTION ENGINES 3,521,606 7/1970 .....l23/32 EA [75] lnventors: Takashi Inoue; Takao Masuda; 2,867,200 1/1959 Gryder et al. ..l23l32 EA Takeshi Harada, all of Higashi-Matsuyama, Japan Primary Examiner-Laurence M. Goodridge [73] Assignee: Diesel Kike Kabushiki Kaisha, Au0mey Larson Taylor & Hinds Japan 57 ABSTRACT [22] Flled: July 1970 An electromagnetic fuel injection device for internal [21] Appl. No.: 54,228 combustion engines comprising electric circuit so arranged that the number of cylinders which undergo simultaneous injection in one cycle of the engine is 2% y' 'g 123/119 39 1 23 lessened at low rotational speeds where the control d 32 H 9 time of the amount of fuel injected is relatively long so 1 0 can l 139 5 as to operate all the fuel injection valves through several stages thereby the period of each fuel injection will not correspond to an overlapping period, while for [56] References cued high speed rotation the number of cylinders related to UNITED STATES PATENTS simultaneous injection is increased to equivalently extend said control time. 3,522,794 8/1970 Reichardt ..l23/32 EA 3,587,536 6/1971 lnoue et al. ..l23/32 EA 4 Claims, 7 Drawing Figures NO N PATENTEDAPR 3 1975 SHEET 1 BF {1 PATENTEDAPR3 1975 3,724,431

SHEET 2 [IF 4 PATENTED APR 3 1975 SHEET 3 BF 4 PATENTEDAPR3 1975 3,724,431

I SHEET u m 4 FIG.6

INVENTOR ATTORNEY ELECTROMAGNETIC FUEL INJECTION DEVICE FOR INTERNAL COMBUSTION ENGINES This invention relates to an electromagnetic fuel injection device for multi-cylinder type internal combustion engines.

Heretofore, a fuel injection device of this type pro vided controlled fuel injection in an amount in accordance with the duration T of the voltage applied to an electromagnetic fuel injection valve. With the rise of engine rotation speed N, the controllable time of the engine I (t (60/N sec) will be decreased. When the controllable time is reduced to a value smaller than the duration T of the voltage applied to the electromagnetic valve, control of the amount of fuel injected has been impossible. It is also known in the prior art that an engine equipped with this sort of device is constructed to perform all cylinder simultaneous fuel injection for each cylinder of four cycle multi-cylinder engine and that during the injection period in certain cylinders suction valves thereof are opened while their exhaust valves are insufficiently closed (valve overlap) so that the gas mixture is blown offwastefully. This effect was particularly apparent at the low speed rotation consequent on the bad fuel consumption rate. The present invention provides an electromagnetic fuel injection system for an internal combustion engine comprising a rotational speed to voltage converter circuit for producing voltage output pulses in accordance with the rotational speed of the engine, a mono-stable multivibrator circuit for receiving the pulses produced by the converter and producing an output in accordance therewith and a control circuit for controlling energization of a plurality of sets of controlcoils to thereby control actuation of a corresponding plurality of fuel injection valves. At low speed operation, the outputs of the multivibrator circuit and converter are connected to the control circuit so as to provide alternate energization of the sets of control coils and hence provide simultaneous minority-cylinder injection. A speed responsive switch suppresses the output pulses from the converter when the engines reaches a predetermined speed so as to provide simultaneous energization of the sets of coils and hence provides simultaneous majoritycylinder injection.

In order that the invention may be more clearly understood, reference will now be made to the accompanying drawings in which:

FIG. 1 is a graph showing the fuel requirement characteristics as a function of rotation speed of an internal combustion engine;

FIG. 2 is a block diagram showing a fuel injection device according to the invention;

F IG. 3 is an electrical circuit diagram of the fuel injection device;

FIG. 4 is a diagram showing pulse waveforms of potentials at various junctions of an injection amount correcting circuit;

FIGS. 5 and 6 are diagrams showing pulse waveforms at each part of the circuit, in each of which (i) represents a set of waveforms relating to simultaneous fuel injection for two cylinders, and (ii) represents a set of waveforms relating to simultaneous fuel injection for four cylinders; and

FIG. 7 is a graph showing a modification of the characteristics of the duration T of pulse.

Referring now to the schematic block diagram of FIG. 2, block A denotes a known rotation speed-voltage converting circuit for producing a voltage pulse related to the rotation speed of the engine. Block B denotes a known monostable multivibrator circuit which generates a rectangular pulse whose frequency varies with the rotation speed of the engine and whose pulse length changes with variations in the vacuum of the suction pipe of the engine. Block D designates an output amplifier circuit for controlling the fuel injec tion valves of the engine E. Block C designates an injection amount correcting circuit which corrects the fuel injection amount relative to the rotation speed of engine. The construction of these circuits is now shown in particulars in FIG. 3. In the figure, section A includes intermittent contacts S1, S2 of the engine, capacitors C1, C2, etc, and generates two pulse trains alternately produced by frequencies proportioned to the engine speed through alternate closing of the contacts S1 and S2. Section B includes a multivibrator circuit having transistors Trl and Tr2, and a timing element having transformer L and resistors R0 and R1. The iron core of transformer L moves in proportion to the vacuum of a suction pipe P of the engine and can change the inductance of a secondary coil of the transformer L so that the duration of the pulses produced varies with the variation in the vacuum of the suction pipe of the engine. Section C is formed of transistors Tr3 Tr7, capacitor C3 C7, resistors R3 R5, variable resistors VRl VR6, diodes D1 D3 and a rotation responsive switch S3, and is arranged to satisfy characteristics of fuel requirements. Section D is formed of transistors Tr8 Trll, control coils Ll L4 of electromagnetic fuel injection valves divided into two groups each consisting of two coils and diodes D4 and D5.

Application of the device of the invention to a four cylinder engine is now illustrated in detail. In reference to FIG. 3, the rotation responsive switch S3 is opened during the low speed rotation (3,500 r.p.m. or less in an experimental engine). The base of the transistor Tr8 becomes negative only when the intermittent contact S1 of the rotation speed-voltage converter circuit is closed. The contact W of the monostable multivibrator circuit B is supplied with a negative trigger pulse through the circuit of the capacitor C1 and diode.

Accordingly, the base of transistor Trl becomes negative and non-conductive and the transistor Tr2 conductive. Current flows in the primary coil of the transformer L and a voltage is induced in the secondary coil. In consequence, current produced by the induced voltage flows in the resistor R1 causing a drop in the terminal voltage of the resistor R1 generated from a power source voltage and turns the base of the transistor Trl negative. The current of the induced voltage is exponentially reduced but it still maintains the base of the transistor Trl negative until the current drops below a predetermined value. Therefore, the transistor Tr2 is retained in conductive state and generates on a junction U1 a pulse T0 related to the induced voltage of the transformer L. In FIG. 4, the pulse T0 is shown at waveform U1. In the same figure, the ordinate denotes the amplitude and the abscissa denotes the time t.

Hence, the bases of the transistors Tr8 and Trll connected to the terminal U1 becomes negative through the pulse TO. As the intermittent contact S2 is opened the base of the transistor T11 is retained in positive. The base of the transistor Tr8 turns negative and nonconducting and the transistor Tr9 becomes conducting. The electromagnetic coils of the fuel injection valves L1 and L2 are excited and fuel is injected. On the other hand, the base of the transistor Trl 1 is fed positive and negative pulses so that the base thereof becomes conducting.

Thus, the transistor TrlI) turns non-conducting. Therefore, the fuel injection valves L3 and L4 will not inject fuel. When the intermittent contact S1 is opened and the contact S2 is closed, then the trigger pulse passing through the capacitor C2 and diode is fed to a junction W. Said pulse generates the pulse T thereby providing anegative pulse to the bases of transistors Tr9 and Trll. As the contact S1 is opened the base of transistor Tr8 turns positive and the transistor Tr9 turns non-conducting. Therefore, the valves L1 and L2 will not inject fuel but the valves L3 and L4 will inject fuel. Accordingly, at a low speed rotation of the engine, each of the two cylinders undergo simultaneous injection alternately (hereinafter referred to as simultaneous injection for two cylinders).

In the subsequent high speed rotation of the engine, the rotation responsive switch S3 is closed so that a positive pulse is supplied via intermittent contacts S1 and S2 to the fuel injection valves Ll-L4 and shortcircuited through diodes D4 and D5. At the same time, the pulse from the intermittent contact S2 passing through the capacitor C2 will disappear. The pulse T0 is generated only through the intermittent contact S1. Hence, assuming that the period of the pulse T0 is t before shortcircuiting of S3 this period becomes 2: after shortcircuiting. Thus the fuel injection valves Ll-L4 will make simultaneous injection by the pulse T0 (hereinafter referred to as simultaneous injection in four cylinders). This is shown in FIG. 5, in which the ordinate denotes the pulse and the absicissa denotes the time, (i) shows simultaneous injection in two cylinders, and (ii) simultaneous injection in four cylinders. According to the invention, therefore, each two cylinders alternately undergo fuel injection at the low speed of the engine and each four cylinders simultaneous injection at the high speed of the engine. Furthermore, the period at the time of the four cylinder simultaneous injection is double the period of two cylinder simultaneous injection. There is caused no variation in the injection amount of fuel before and after switching over of the injection.

In accordance with the present invention, moreover, the correction of the fuel injection amount responsive to the engine r.p.m. is effectively performed. Generally, the air suction amount of the internal combustion engine initially increases with the rise of rotation speed due to resistance of the suction air pipe etc. and subsequently it decreases as has been well known. Thus it is required to vary the amount of fuel supply in conformity with this circumstance. The relation of the fuel supply and the rotation speed of engine is shown in FIG. 1, in which the ordinate shows an injection amount of and the abscissa shows the rotation speed N of the engine. The correction of the fuel injection amount is realized in the circuit of section C. The pulse T0 generated in the collector of the transistor Tr2 of circuit B is also supplied to the fuel injection amount correcting circuit C. The transistor Tr3 produces on junction U2 a pulse Tl which is shown in FIG. 4 at waveform U2 as and is determined by the capacitor C3.

and the resistor R3. The transistor Tr4 produces on junction U3 a pulse T2 which is shown in FIG. 4 at waveform U3 and is determined by the capacitor C4 and the variable resistors VRl and VR2.

The transistor Tr5 produces on junction U4 a pulse T3 which is shown at waveform U4 in FIG. 4 and is determined by the capacitor C5 and the variable resistors VR3,VR4. The transistor Tr6 produces on point US a pulse T4 which is shown in FIG. 4 at waveform US in an inverted form of the pulse T3. Under this condition, the transistor Tr6 is in conducting state so that the capacitor C6 is discharged with the discharge characteristics as determined by the variable resistor VRS. When the pulse T4 disappears then the transistor Tr6 becomes non-conducting and the capacitor C7 is charged. The charging process is performed with the characteristics as determined by the variable resistor VR6. The pulse of the transistor T2 is applied in the charge through the diode D3 to make constant the initial condition of the discharge potential. Accordingly, the potential of the connection U6 will vary as shown in FIG. 4 at waveform U6. In FIG. 4, the portion or part a of the waveform U6 designates the discharge process of the capacitor C6 and the portion or part B denotes the charge process thereof. This potential is amplified by the transistor Tr7 and the amplified potential is supplied to a junction U7 of secondary coil of the transformer L through the variable resistor VR7.

If the potential is high in the junction U7 the time is shortened to retain the point W in the negative by the transformer L. The pulse length of the pulse T0 will then become small, and if the potential is low the pulse length of the pulse T0 becomes large. As the rotation speed of the engine is raised the pulses T0-T4 move to v the left as shown by dotted lines in FIG. 4. As the potential of the junction U7 will vary as shown in the dotted waveform since the pulse T2 is applied therein earlier. This pulse T2 is supplied at point Z, corresponding to the engine r.p.m. No of FIG. 1, from part B of the low speed rotation area with the rise of speed and applied in part a in the high speed rotation area. Thus, the potential of the junction U7 decreases by increase of rotation speed at the low speed rotation side and increases at the high speed rotation side with Z as a turning point as shown in FIG. 4. As the result, a voltage characteristic of a chevron-shape may be obtained as shown in FIG. 1.

As hereinbefore described, the injection period in the four cylinder simultaneous injection is double the period of the two cylinder simultaneous injection. If the charge and discharge circuit including the capacitor C6 in the four cylinder simultaneous injection is same as in the two cylinder simultaneous injection, the position of point Z corresponding to the engine rotation speed No will be displaced. Since it is provided that the injection period is doubled, or the time abscissa is double the previous length, the time constant of the charge and discharge circuit is required to be doubled. This adjustment may be performed in the following way. Simultaneously as the switch S3 is closed in response to the high speed rotation of the engine the negative sides of longer and the pulse length of the pulses T2, T3 is doui bled. As the capacitor C7, which was formerly open circuited, is connectedv in parallel with the capacitor C6, and assuming that the capacitance of the capacitor C6 is equal to that of the capacitor C7, then the gradients of the portions a and ,8 of the waveform U6 of FIG. 4 are respectively turned to half due to the consequent change in rise time. In FIG. 6, curves Ul-U7 respectively represent voltage waveforms at various junctions, the ordinate denoting an amplitude and the abscissa denoting time. In the same figure, (i) shows simultaneous injection for two cylinders and (ii) simultaneous injection for four cylinders. As will be apparent from this figure, the period of each pulse in case (ii) is double that of each pulse of (i). The potentials X3 Z0: of the waveform U7 will have a gradient of characteristics as in XlBlZlal. Thus the potential e at the termination of second pulse T0 affecting the multivibrator circuit B is common to both cases (i) and (ii). Even though the potential is changed over the pulse length of the second pulse T0 is not changed and accordingly the injection characteristics will not become non-continuous. Comparison of the potential e must be attempted at the high speed rotation side but now it has been made at the low speed rotation side for convenience of description.

Characteristics of the continued time T of applied voltage may be modified, as shown at dotted line a in FIG. 7, by adjusting the variable resistors VRl-VR4 to desirably define the pulse lengths of the pulses T2, T3, and adjusting the variable resistors VRS, VR6 to change the discharge time of the capacitor C6 and the curve XBYZoz of the waveforms U6, U7 shown in FIG. 4.

It is apparent that another transistor circuit for generating pulses T5, T6 may be provided between the pulses T3 and T4 with the pulses T3 and T6 applied to the base of the added transistor to form an OR-circuit and change the discharge waveform of the capacitor thereby providing irregular characteristics thereto as shown in dotted curve b of FIG. 7. Change of the rotation speed of engine may be obtained by changing the turn of the throttle valve by the accelerator pedal to change the vacuum of the suction air pipe P, the induced voltage of the transformer L responsive to the vacuum, and the pulse length of the pulse TO, thereby adjusting the injection amount.

In accordance with, the invention, as described above, the device may be switched over to the four cylinder simultaneous injection at the high speed rotation of the engine at which the fuel injection amount may be fairly controlled. At the same time, the device will be switched over to the four cylinder injection and thereby period of injection may be doubled. As the result, there will not be produced any difference in the injection amount of fuel before and after switchover from the two cylinder to the four cylinder operation. The fuel amount adjusting means may have a characteristic as desired adapted for the engine so as to elevate the consumption of fuel. The duration of the pulse in the switchover operation will not have discontinuity so that stable control may be obtained over the whole area of rotation speed of the engine.

It is of course to be noted that the switchover operation is not limited only to the two-to-four cylinder fuel injection but it may also be applied to the fuel injection in the ratio of 1:2.

While the invention has been described in detail with respect to a particular preferred embodiment of the invention it will be understood that various changes and modifications may be made without departing from the spirit and scope of the invention.

What is claimed is:

1. An electromagnetic fuel injection system for an internal combustion engine, comprising rotational speed to voltage converter means for producing voltage output pulses in accordance with the rotational speed of the engine, monostable multivibrator circuit means for receiving said pulses and producing an output in accordance therewith, control circuit means for controlling energization of a plurality of sets of control coils for controlling actuation of a corresponding plurality of fuel injection valves, means for connecting the output of said converter means and the output of said multivibrator circuit means to the input of said control circuit means so as to provide alternate energization of at least two sets of said sets of control coils and hence provide simultaneous minority-cylinder injection, and speed responsive switching means for suppressing output pulses from said converter means when the engine reaches a predetermined speed so as to provide simultaneous energization of said at least two sets of coils and hence provide simultaneous majority-cylinder injection, said system further comprising timing circuit means connected to the input of said control circuit means for controlling the fuel injection control voltage in accordance with the fuel supply versus rotational speed characteristic of the engine, said timing circuit including a discharge circuit and said speed responsive switching means including means for varying the discharge time of said discharge circuit when the engine reaches said predetermined speed, said timing circuit including a plurality of RC components for determining the time constant of said timing circuit and said speed responsive switching means including a switch means for switching selective ones of said RC components in and out of said timing circuit to control charging and discharging of said timing circuit so as to maintain the rotational speed-fuel injection characteristic of the system.

2. A system as claimed in claim 1 wherein the time constant of said timing circuit is doubled when the system switches from simultaneous minority-cylinder injection to simultaneous majority-cylinder injection.

3. A system as claimed in claim 1 wherein said control circuit means includes at least first and second switching transistors for controlling energization of said coils and said means for connecting the output of said converter means to said control circuit means comprises alternately operable switches for controlling the period during which said transistors conduct, said speed responsive switching means including a switch for, when actuated, substantially short-circuiting one of said alternately operable switches to thereby increase the period during which at least one of said first and second switching transistors conducts.

4. A system as claimed in claim 1 wherein said monostable multivibrator circuit means includes means for varying the duration of the output pulses produced 5 thereby in accordance with the suction forces exerted by the engine suction pipe.

Claims (4)

1. An electromagnetic fuel injection system for an internal combustion engine, comprising rotational speed to voltage converter means for producing voltage output pulses in accordance with the rotational speed of the engine, monostable multivibrator circuit means for receiving said pulses and producing an output in accordance therewith, control circuit means for controlling energization of a plurality of sets of control coils for controlling actuAtion of a corresponding plurality of fuel injection valves, means for connecting the output of said converter means and the output of said multivibrator circuit means to the input of said control circuit means so as to provide alternate energization of at least two sets of said sets of control coils and hence provide simultaneous minority-cylinder injection, and speed responsive switching means for suppressing output pulses from said converter means when the engine reaches a predetermined speed so as to provide simultaneous energization of said at least two sets of coils and hence provide simultaneous majority-cylinder injection, said system further comprising timing circuit means connected to the input of said control circuit means for controlling the fuel injection control voltage in accordance with the fuel supply versus rotational speed characteristic of the engine, said timing circuit including a discharge circuit and said speed responsive switching means including means for varying the discharge time of said discharge circuit when the engine reaches said predetermined speed, said timing circuit including a plurality of RC components for determining the time constant of said timing circuit and said speed responsive switching means including a switch means for switching selective ones of said RC components in and out of said timing circuit to control charging and discharging of said timing circuit so as to maintain the rotational speed-fuel injection characteristic of the system.

2. A system as claimed in claim 1 wherein the time constant of said timing circuit is doubled when the system switches from simultaneous minority-cylinder injection to simultaneous majority-cylinder injection.

3. A system as claimed in claim 1 wherein said control circuit means includes at least first and second switching transistors for controlling energization of said coils and said means for connecting the output of said converter means to said control circuit means comprises alternately operable switches for controlling the period during which said transistors conduct, said speed responsive switching means including a switch for, when actuated, substantially short-circuiting one of said alternately operable switches to thereby increase the period during which at least one of said first and second switching transistors conducts.

4. A system as claimed in claim 1 wherein said monostable multivibrator circuit means includes means for varying the duration of the output pulses produced thereby in accordance with the suction forces exerted by the engine suction pipe.

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