JPS6157937B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection control device for a fuel injection type engine, and particularly to one that prevents knocking caused by an increase in intake air temperature.

Generally, when the temperature of intake air supplied to an engine becomes high, the fuel tends to ignite, and knocking is likely to occur due to abnormal combustion, which is particularly noticeable at low engine speeds and high loads.

For this reason, knocking has been detected in conventional fuel injection engines in which fuel injection from a fuel injection valve is controlled based on the intake air amount of the engine, as shown in Japanese Patent Application Laid-Open No. 56-20763. It is known to prevent knocking from occurring by controlling the ignition timing, exhaust recirculation amount, fuel injection amount, or fuel injection timing of the engine.

However, if, for example, the amount of fuel injection is increased in order to prevent the occurrence of knocking due to a rise in intake air temperature, the intake air temperature will decrease by utilizing the heat of vaporization of the increased amount of fuel, and it is possible to prevent the occurrence of knocking. However, on the other hand, there is a drawback that the air-fuel ratio becomes overbalanced, resulting in poor combustibility and poor fuel efficiency. Further, even if other fuel injection timing or the like is controlled, it does not contribute to lowering the intake air temperature and is not very effective in preventing knocking caused by an increase in the intake air temperature.

In view of this, the present invention improves the vaporization of the injected fuel by increasing the number of injections of the fuel injector compared to the normal number of injections during knocking in the fuel injection type engine as described above. It is an object of the present invention to provide a fuel injection control device for a fuel injection type engine, which effectively utilizes the heat of vaporization to lower the intake air temperature, thereby preventing the occurrence of knocking caused by an increase in the intake air temperature. It is something to do.

That is, the present invention provides a fuel injection engine in which fuel injection from a fuel injection valve is controlled based on the intake air amount of the engine, in which knocking of the engine is prevented due to pressure fluctuations in the combustion chamber or engine vibrations caused by the pressure fluctuations. The present invention is characterized by comprising a detection means for detecting the state, and a fuel injection number control means for increasing the number of injections of the fuel injection valve from the normal number of injections in accordance with the output signal of the detection means.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 1 shows a fuel injection control device for a fuel injection type engine, which is an embodiment of the present invention. In FIG. 2 is a bandpass filter that extracts a vibration signal of a predetermined frequency as an output A from the vibration signal of the knocking sensor 1, and 3 is a reference based on the output A of the bandpass filter 2. A first reference level setting circuit 4 sets the output B of the level by comparing the output A of the bandpass filter 2 and the output B of the first reference level setting circuit 3 and determining whether the output A is larger than the reference output B. a first comparison circuit that sometimes outputs an output C;
5 is an output D obtained by integrating the output C of the first comparison circuit 4.
6 is a second reference level setting circuit that sets the reference level output E; 7 is a comparison circuit that compares the output D of the integrating circuit 5 with the output E of the second reference level setting circuit 6 and sets the output D. a second comparator circuit that outputs an output F when is greater than the reference output E, and 8 a first comparator circuit that passes or blocks the output F of the second comparator circuit 7;
The first gate circuit 8 receives an output from an engine speed detection circuit 9 that detects the engine speed, and when the engine speed is below a set value (when the engine is running at low speed), the first gate circuit 8 receives an output from an engine speed detection circuit 9 that detects the engine speed. The output F from the second comparison circuit 7 is passed through and added to the second gate circuit 14, which will be described later.
This prevents the output F of the comparator circuit 7 from passing through. The circuits from the knocking sensor 1 to the first gate circuit 8 constitute a detection means 10 for detecting a knocking state of the engine.

Further, 11 is a measuring plate type flow meter that detects the intake air amount of the engine, and 12 is a measuring plate type flow meter that detects the rotation of the distributor and outputs one pulse signal per one revolution of the distributor (per two revolutions of the engine). The first rotation pick-up to output,
13 similarly detects the rotation of the distributor, and has a phase difference of 180 degrees in the distributor angle with respect to the first rotating pickup 12, and generates a signal of 1 per revolution of the distributor (per 2 revolutions of the engine). 14 is a second gate circuit that passes or blocks the output of the second rotary pickup 13, and the second gate circuit 14 receives the output from the first gate circuit 8. When received, the output of the second rotary pickup 13 is passed through, while the first gate circuit 8
When the output from the second rotary pickup 13 is not received, the output from the second rotary pickup 13 is prevented from passing through. Furthermore, 15 is a fuel calculation circuit that controls fuel injection of the fuel injection valve 16 in response to outputs from the flow meter 11, the first rotary pickup 12, and the second gate circuit 14; , outputs an injection pulse signal corresponding to a predetermined fuel injection amount based on the output of the flow meter 11, and outputs an injection pulse signal corresponding to a predetermined fuel injection amount, and
When receiving the output from the rotary pickup 12 (normally when knocking does not occur), the injection pulse signal is converted into a pulse having a regular number of injection pulses and a pulse width corresponding to the number of pulses of the first rotary pickup 12. On the other hand, when the output from the second gate circuit 14 is further added (during knocking), the injection pulse signal is converted to the sum of the number of pulses of the first rotary pickup 12 and the second rotary pickup 13. The number of pulses is twice the number of normal injection pulses corresponding to the number of normal injection pulses, and the pulse width is 1/2 of the width of the normal injection pulse. By means of the circuit from the first rotary pickup 12 to the fuel calculation circuit 15, the number of injections of the fuel injection valve 16 is changed from the normal number of injections according to the output signal of the detection means 10 without increasing the fuel injection amount. Also constitutes a fuel injection frequency control means 17 for increasing the number of fuel injections by, for example, two times.

Further, 18 is an adder circuit that adds the output D of the integration circuit 5 and the output of the engine speed detection circuit 9, and 19 is a retard amount control circuit that controls the amount of retardation of the ignition timing based on the output of the adder circuit 18. , 20 is a signal generator that generates a synchronizing pulse according to the rotation of the engine, and 21 is a signal generator that retards the output pulse of the signal generator 20 by the output of the retard amount control circuit 19 to ignite the ignition circuit 22. The circuit from the addition circuit 12 to the igniter 21 constitutes an ignition timing control means 23 that controls the ignition timing of the engine.

Next, the operation of the above embodiment will be explained with reference to FIGS. 2 and 3.

First, in normal times when engine knocking is not occurring, the second gate circuit 1
4 is in a state in which passage of the output of the second rotary pickup 13 is blocked. As a result, the output of the flow meter 11 and the output of the first rotary pickup 12 shown in FIG. A regular injection pulse signal having a number of pulses corresponding to the number of pulses of the first rotary pickup 12 is output. Therefore, fuel is injected from the fuel injection valve 16 in an injection amount based on the intake air amount even at the regular number of injections, and good combustion is performed at an appropriate air-fuel ratio.

On the other hand, when the engine knocks due to a rise in intake air temperature, the knocking sensor 1 detects this knocking condition as pressure fluctuation in the combustion chamber or engine vibration, and outputs a vibration signal as shown in Figure 2a. A, and when the amplitude thereof is larger than the reference level output B of the first reference level setting circuit 3, the first comparator circuit 4 outputs an output C as shown in FIG. 2b. Then, this output C is integrated by the integrating circuit 5 to become an output D as shown in FIG. 2 comparison circuit 7 outputs an output F as shown in FIG. 2d, and it is detected that knocking has occurred.

At that time, if the engine rotation speed is in a low rotation range below the set value, the first gate circuit 8 receives the output of the engine rotation speed detection circuit 9 that detects this, and enters a state in which the signal is allowed to pass. Therefore, the output F from the second comparison circuit 7 is inputted to the second gate circuit 14 via this first gate circuit 8. As a result, the output of the second rotary pickup 13 shown in FIG.
As a result, the fuel calculation circuit 15 generates a number of pulses that is twice the normal injection pulse number, which corresponds to the sum of the number of pulses of the first rotary pickup 12 and the second rotary pickup 13, as shown in FIG. 3d. , and an injection pulse signal having a pulse width of 1/2 of the normal injection pulse width is output, and therefore, the fuel injection valve 16 is capable of injecting intake air even if the number of injections is twice as large as the normal number of injections. The same amount of fuel will be injected as in normal times based on the amount of fuel.

Therefore, when knocking of the engine is detected in this way, the number of injections by the fuel injection valve 16 is increased to, for example, twice the normal number of injections, so that the amount of fuel injection remains the same as normal. Coupled with the small injection amount per injection, fuel atomization is promoted and vaporization is improved, so the heat of vaporization can be effectively used to significantly lower the intake air temperature. Therefore, it is possible to reliably prevent knocking from occurring due to a rise in intake air temperature. Note that when the engine speed is high, exceeding a set value, the output F of the second comparator circuit 7 is input to the second gate circuit 14 by the first gate circuit 8 that receives the output from the engine speed detection circuit 9. However, in this case, since the engine is running at high speed, knocking is unlikely to occur, and the fuel injection valve 16 When the number of injections is increased, the fuel injection valve 1
This is due to the following factors: the follow-up performance of No. 6 deteriorates, the air-fuel ratio changes from the appropriate value, and the combustibility deteriorates.

Furthermore, when detecting knocking, the integrating circuit 5
The output D is input to the addition circuit 18 and added to the output of the engine rotation speed detection circuit 9, and the output is input to the retard amount control circuit 19, which changes the output of the igniter 21. By controlling the amount of retardation, the ignition timing of the ignition circuit 22 is determined by the amount of retardation determined by the engine speed;
The output D is additionally retarded by the amount shown in FIG. 2c, thereby making it possible to more reliably prevent the knocking from occurring.

Incidentally, in the above embodiment, a case was described in which a measuring type flowmeter was used as the flowmeter 11.
A Karman vortex flowmeter may be used, and in this case, the fuel injection number control means 17 is the detection means 10.
A frequency division rate control circuit that increases the frequency division rate of the Karman vortex flowmeter according to the output of the fuel calculation circuit 15 may be provided, and the output of the frequency division rate control circuit may be input to the fuel calculation circuit 15.

Further, in the above embodiment, when knocking is detected, the number of injections of the fuel injector 16 is twice the normal number of injections, but the point is that if the number of injections is increased more than the normal number, the present invention can be applied. This objective can be fully achieved.

As explained above, according to the present invention, in a fuel injection engine, the number of injections of the fuel injector is increased compared to the normal number of injections when knocking, so that the combustibility and fuel efficiency of the engine are improved. The intake air temperature can be effectively lowered without adversely affecting the intake air temperature, etc., and thus the occurrence of knocking due to an increase in the intake air temperature can be prevented in advance.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram showing an embodiment of the present invention, FIGS. 2 a to d are signal waveform diagrams of each part of the detection means in FIG. 1, and FIGS. 3 a to d are fuel injection frequency control as shown in FIG. 1. It is a signal waveform diagram of each part of a means. DESCRIPTION OF SYMBOLS 1...Knocking sensor, 4...First comparison circuit, 5...Integrator circuit, 7...Second comparison circuit, 8...
...First gate circuit, 9... Engine rotation speed detection circuit, 10... Detection means, 11... Flow meter, 12...
...first rotation pick-up, 13...second rotation pick-up, 14...second gate circuit, 15...fuel calculation circuit, 16...fuel injection valve, 17...fuel injection frequency control circuit.

Claims (1)

[Claims] 1 Detection of a knocking state of the engine due to pressure fluctuations in the combustion chamber or engine vibrations caused by the pressure fluctuations in a fuel injection engine in which fuel injection from a fuel injection valve is controlled based on the intake air amount of the engine. 1. A fuel injection control device for a fuel injection type engine, comprising: means for controlling the number of injections of a fuel injection valve than the normal number of injections according to an output signal of the detection means. .