JPH0112933B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electronic fuel injection device for an internal combustion engine, and more specifically, a transmitter that generates a signal indicating an operating characteristic quantity (an operating parameter indicating an operating characteristic such as the rotation speed or load of the internal combustion engine), and at least an injector. The present invention relates to an electronic fuel injection device for an internal combustion engine, which has a timing element (timing element that generates a signal with a predetermined variable pulse width) that generates a signal. In such a device, the ignition pulse is applied to a pulse shaper, after which a frequency divider is connected, the output of which is used as the input signal of a control multivibrator, which acts as a timing element for the injection pulse. It has been known. In such a controlled multivibrator, the injection pulse is determined as a function of the air flow rate in the suction pipe and, if necessary, is further corrected by a multiplication circuit connected later. The task of the frequency divider connected before the control multivibrator is to carry out the injection process only while the crankshaft is rotating. This is particularly valuable when determining the injection period accurately, since frequency division provides a large margin for determining the injection period. In fact, in automobiles equipped with electronic fuel injection devices (for example, the fuel injection devices described in Japanese Patent Publication No. 47-27063, Japanese Patent Publication No. 47-40225, etc.), the injection signal is output based on the rotational speed signal. It has been found that, as a result, the injection amount fluctuates in accordance with rapid fluctuations occurring in the rotational speed signal, resulting in torque fluctuations and an unstable state (rattling). To avoid this, a dynamic rotation speed damping device (variation prevention circuit) is provided. When the ignition signal is used as a speed signal, the time intervals are different, especially if fluctuations occur from spark to spark in the ignition distributor device, which leads to speed changes and inaccurate injection durations. I get used to it. SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an electronic fuel injection system for an internal combustion engine that can overcome the above-mentioned drawbacks and can operate stably even when the rotational speed changes rapidly. To achieve this objective, the invention provides a signal indicative of an operating characteristic quantity, the frequency of which varies between an oscillator that generates a signal whose frequency varies, and a timing element that generates a signal that controls the fuel injector. A frequency control circuit or a phase control circuit is placed to attenuate the
A configuration is adopted in which the frequency control circuit or the phase control circuit attenuates the frequency fluctuation of the output signal from the oscillator and inputs it to the timing element to start fuel injection. According to such a configuration, the frequency control circuit or the phase control circuit prevents sudden fluctuations in the frequency of the oscillator output signal from being directly transmitted to the timing element, and even if the rotational speed signal changes suddenly, the injection is not affected to a great extent, and therefore an electronic fuel injection system can be obtained in which the torque is stable and the unstable state of rattling can be eliminated. Preferably, the frequency control circuit or the phase control circuit is driven at a frequency that has a selectable ratio to the frequency of the oscillator output signal, thereby controlling the required oscillator front minutes according to the type of injector. The oscillator before the frequency and timer elements can be omitted. Furthermore, embodiments of the invention provide this advantage in future central injection systems with only one injection valve. In order to ensure dynamic characteristics, such devices require twice the injection frequency (i.e. two injections per revolution of the crankshaft) compared to conventional ones; Doubling can be achieved by simple means by using a frequency control circuit or a phase control circuit. Further, in the case of an internal combustion engine having a large number of cylinders, particularly a five-cylinder internal combustion engine, the injection frequency can be obtained without any problem via a frequency control circuit or a phase control circuit. Next, the apparatus of the present invention will be explained in detail with reference to the accompanying drawings. FIG. 1 is a block diagram of an electronic fuel injection system for an internal combustion engine in which the injection period of at least an injector is determined on the basis of operating characteristics, 10 designating a pulse generator responsive to an ignition signal. A pulse shaper 11 is connected after the pulse generator, the output 12 of which is connected to a frequency divider 13. Furthermore, a frequency control circuit or a phase control circuit 14 is connected. The type of control circuit used depends, inter alia, on economic considerations and the required accuracy or design of the circuit arrangement. The output of the frequency or phase control circuit (hereinafter referred to as control circuit) is the timer element 1.
7, the timing element 17 has a further input 18 as well as an output 19. A second input 18 of the timing element 17 is applied with a signal that is related to the air flow rate in the suction pipe. If necessary, a correction circuit for varying the injection period as a function of other operating variables (not shown) may also be connected. Finally, at least an electromagnetically actuated injection valve 20 is connected, the winding of which is applied with the pulse generated by the timing element 17, so that fuel injection is initiated or carried out. The pulse generator 10 generates pulses according to the firing frequency and generates a signal indicating the rotational speed. Therefore,
The pulse generator constitutes a transmitter which generates a signal indicating an operating variable of the internal combustion engine. Pulse generator 10
The pulses from the pulse generator 11 are shaped in the next pulse shaper 11 and then subjected to processing. A control circuit 14 connected after the frequency divider adjusts for large fluctuations in the output signal of the pulse generator, so that a signal without sudden changes in frequency is applied to the first input 16 of the timing element 17. be done. The timing element 17 itself determines the injection period from this indirect rotational speed signal and a signal related to the air flow rate in the suction pipe. If necessary, this injection period can be further corrected via further circuits. Depending on what kind of control circuit 14 is used, the frequency divider circuit 13 having a frequency division ratio of n:1 (not specifically shown) can be omitted. FIG. 2 shows a phase control circuit utilized in the block diagram of FIG. 1. In this case, the control circuit 14 is designed as a phase control circuit. The phase control circuit is composed of, for example, a phase locked loop known as a PLL (phase locked loop).
It essentially consists of a phase detector 30, a low-pass filter 31, a voltage controlled oscillator 32, and a control loop 33. In the simplest case, the frequency of the voltage-controlled oscillator and the input signal of the phase-controlled circuit coincide. A phase detector 30 determines the deviation in phase of the input and output signals, and a signal representative of this phase difference is applied to a low pass filter. The frequency of the voltage controlled oscillator 32 is influenced by this output signal, thereby allowing a frequency change in the output signal of the phase control circuit. As the phase detector 30, a conventional exclusive-or gate can be used. As is well known, the output signal of such a phase control circuit does not show sudden fluctuations, and therefore, a signal with no drastic change in frequency is applied to the time-limiting element. Frequency control circuits as well as phase control circuits are well known (e.g. U.S. Pat.
3716794 or Japanese Patent Publication No. 60-7416), which will not be described in detail here, can provide the same effects as the phase control circuit. Various relationships occur between the ignition signal and the injection signal depending on the type of internal combustion engine. This is particularly true in the case of a five-cylinder internal combustion engine, in which case ignition occurs five times per two revolutions of the crankshaft, but it is desired that injection occurs only once per one revolution of the crankshaft. The frequency divider 13 and control circuit 14 shown in FIG. 1 are designed in response to such a frequency relationship. Relationships for arbitrary frequencies can be realized using the generalized circuit of FIG. The block diagram of FIG. 3 includes a total of three frequency dividers. In this case, the first frequency divider 13 has a frequency division ratio of n:1, and the frequency divider 4 connected after the control circuit
0 has a frequency division ratio of p:1, and the frequency divider 41 arranged in the control loop has a frequency division ratio of m:1. The output frequency of the pulse shaper 11 is f ₀ , the output frequency of the frequency divider 13 is f ₁ , the output frequency of the voltage controlled oscillator 32 is f ₂ , the frequency of the signal fed back to the phase detector is f ₃ , the frequency divider 40 output signal frequencies are respectively denoted by f ₄ . If f ₁ and f ₃ have the same value, the frequency f ₄ has a value of f ₄ =m/m·p·f ₀ . Since the frequency of the signal of the pulse generator and the frequency of the input signal of the timer 17 have a relationship according to this formula, the frequency division ratios n:1 and p:1 of the frequency dividers 13 and 40 can be replaced. It becomes clear what is possible. Frequency divider 13 or 40 depending on how the individual frequency division ratio is determined
can be omitted. In this case, the selection is determined according to various criteria, such as the type of control circuit and the frequency range of the signal from the pulse generator. The frequency division ratio m:1 of the frequency divider 41 allows the frequency of oscillation of the voltage controlled oscillator to be further increased. By choosing the values of m and n,
In each case (for each number of cylinders and each type of injection, for a normal injection frequency or for a double injection frequency) the required ratio of injection frequency to ignition frequency can be realized. If you increase the division value of m, the division value of p will increase for the same output frequency,
This allows the voltage-controlled oscillator to turn on and off in individual cases.
The asymmetric off-time allows the oscillator frequency to be increased or the on-off time of frequency divider 40 to be symmetrical. By using the device shown, not only is an anti-fluctuation function achieved and irregular ignition periods compensated for, but a uniform frequency divider is obtained for all cylinder numbers and injection methods. The following table shows the necessary and possible frequency division ratios for the frequency divider of FIG. In this table, ZEI indicates an intermittent central injection system. In other words, only one injection station is provided in an intermittently operating injection device. A feature of such a concentrated injection device is that the number of injections per revolution of the crankshaft is doubled.
FT1 to FT3 indicate frequency dividers 13, 41, and 40, respectively. Also, KW indicates crankshaft rotation.

[Table] In the embodiment shown above, the control circuit 14 was connected between the pulse generator 10 for the rotational speed signal and the timing element 17 for the injection pulse, but the invention is not limited to this. If other operating characteristic quantities, such as air flow rate, are present or processed in a frequency-related manner, the transmitter indicating the operating characteristic quantity is also equipped with a corresponding control circuit to suppress frequency fluctuations. It is preferable to provide For example, when processing a signal such as a rotational speed signal, it is preferable to process other signals, such as a signal indicating the ignition time, by means of the control circuit and to use an operating characteristic quantity signal whose fluctuations are thereby reduced. As described above, in the present invention, a frequency control or phase control circuit is arranged between the transmitter that generates the signal indicating the operating characteristic amount and the timing element that performs fuel injection to attenuate sudden frequency fluctuations in the output signal from the transmitter. In this way, rapid frequency fluctuations in the output signal from the oscillator are attenuated, and the output signal from the frequency control or phase control circuit with the frequency fluctuations attenuated is input to the timing element to generate a signal with the frequency fluctuations attenuated. Since the fuel injection is performed according to the frequency control or phase control circuit, the fuel injection can be started in synchronization with the output signal whose frequency fluctuation is attenuated by the frequency control or phase control circuit. Therefore, even if the signal that starts fuel injection fluctuates rapidly, the injection is performed in synchronization with the signal whose frequency fluctuations have been attenuated, so stable fuel injection can be performed at all times, and irregular fluctuations in the internal combustion engine can be avoided. An excellent effect can be obtained in that fluctuations can be reliably prevented.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an outline of the electronic fuel injection device of the present invention, FIG. 2 is a block diagram of a phase control circuit used in the present invention, and FIG. 3 is another embodiment of the electronic fuel injection device of the present invention. FIG. 2 is a schematic block diagram illustrating an example. 10... Pulse generator, 11... Pulse shaper, 13... Frequency divider, 14... Phase control circuit, 1
7... Timing element, 20... Injection valve, 30... Phase detector, 31... Low pass filter, 32... Voltage controlled oscillator, 40, 41... Frequency divider.

Claims (1)

[Scope of Claims] 1. A transmitter 10 that generates a signal indicating an operating characteristic quantity whose frequency changes; a timer 19 that generates a signal that drives a fuel injection valve and performs fuel injection; placed between the transmitter and the timing element;
It has a frequency control or phase control circuit 14 that attenuates sudden frequency fluctuations in the output signal from the oscillator, and the output signal from the frequency control or phase control circuit 14 is input to the time element, and the frequency control or phase control circuit 14 An electronic fuel injection device for an internal combustion engine, characterized in that fuel injection is started in accordance with an output signal from a phase control circuit in which frequency fluctuations are attenuated. 2. The electronic fuel injection device according to claim 1, wherein the transmitter 10 is a pulse generator that generates a signal corresponding to a rotational speed signal. 3. The electronic fuel injection device according to claim 1, wherein a frequency divider is connected before and/or after the frequency control or phase control circuit. 4. The electronic fuel injection device according to claim 1 or 3, wherein a frequency divider 41 is connected to the control loop of the frequency control or phase control circuit. 5. In any one of claims 1 to 4, the frequency control or phase control circuit 14 includes a voltage controlled oscillator 32,
The electronic fuel injection system as described above, the frequency of which is selectably multiplied by the input frequency. 6. In any one of claims 1 to 5, the voltage controlled oscillator 32
The input signal or output signal of the electronic fuel injection device is used as a control signal for other circuit devices.