JPS6336422B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection timing measuring device for a diesel engine.

As a conventional fuel injection timing measuring device of this type, there is one proposed in Japanese Patent Application No. 56-45649 as shown in FIG. When high-pressure fuel from a high-pressure pump is supplied to the fuel injection valve 1 through the fuel supply passage 2, the needle valve 3 is displaced upward to open the nozzle hole 4 and inject fuel, and the spring 5 and The pressing force applied to the lift sensor 7 made of a piezoelectric element or the like via the ground plate 6 increases, and an electromotive force is generated in the lift sensor 7, and the electromotive force is transmitted to the lift sensor signal S1 (see the solid line in FIG. 2B). It is taken out from the electrode 8 as a. After slicing this lift sensor signal S1 according to the detection level S2 (see the broken line in Fig. 2B), the waveform is shaped and the shaped signal S3 (see the broken line in Fig. 2C) is sliced.
). This shaping signal S3 and the 120° angle signal S4 (see Fig. 2A) supplied from the engine crank angle sensor (not shown) are used to shift the needle valve 3 from the lift angle position TS to the engine reference angle position TF.
A signal S5 (see FIG. 2D) indicating the offset amount T1 up to is obtained. Based on this detection signal S5, the fuel injection timing of the fuel injection valve 1 is measured, and the fuel injection amount is calculated from this measurement information and the injection period to determine the difference from the target fuel injection amount, and the difference is corrected and controlled. By doing so, efforts are being made to reduce fuel consumption and harmful gas emissions.

However, in such a fuel injection timing measuring device, when the lift sensor 7 is installed in one of a plurality of cylinders, the movement of the needle valve of the fuel injection valve of the cylinder adjacent to the cylinder in which the lift sensor 7 is installed is detected. An impact force corresponding to the above is transmitted to the lift sensor 7, and the lift sensor 7 detects this impact force as a signal component S02. This abnormal signal component S02 is a normal signal component S01 indicating the displacement of the needle valve 3 of the fuel injection valve 1 in which the lift sensor 7 is installed, as shown by the solid line in FIG. 2B.
Although the voltage level is relatively lower than that of , the pressure of the pumped fuel also increases as the engine speed and load increase, so the abnormal signal component S02 and the normal signal component S01 increase the engine speed, load, etc. As the voltage increases, the voltage level also increases. However, the lift sensor signal S1
Since the detection level S2 is fixed at a predetermined voltage level, for example, a voltage level matched to the minimum rotation of the engine, as shown in FIG. 2 C and D,
As the engine speed and load increase, abnormal signal components from other cylinders are also measured. Furthermore, since this abnormal signal component is accompanied by a propagation delay, the injection timing and offset amount T2 detected by the abnormal signal component S02 deviate from the injection timing and offset amount T1 detected from the normal signal component S01. Therefore, the detection accuracy of injection timing deteriorates,
Control performance will be impaired.

An object of the present invention is to eliminate the above-mentioned drawbacks and to provide a means for making the detection level of the lift sensor signal obtained from the lift sensor variable depending on the operating state of the engine, thereby making it possible to accurately measure fuel injection timing. An object of the present invention is to provide a fuel injection timing measuring device for a diesel engine.

In order to achieve the above object, the present invention provides a lift sensor that outputs a first signal corresponding to the displacement of a needle valve of a fuel injection valve, and a lift sensor that outputs a second signal that changes according to engine operating conditions. means and said first
and means for obtaining a third signal corresponding to the opening of the fuel injector by comparing the signal with the second signal, and determining the injection time of the fuel injector based on the third signal. It is characterized by detecting.

The means for outputting the second signal is comprised of, for example, the crank angle sensor 23 and the frequency-voltage converter 24 shown in FIG. 3, which will be described later, and the means for obtaining the third signal is, for example, shown in FIG. It is composed of a comparison circuit 22.

Hereinafter, the present invention will be explained in detail based on the drawings.

Incidentally, since the fuel injection valve used in the present invention has the same configuration as that shown in FIG. 1, detailed explanation will be omitted.

FIG. 3 shows an example of a fuel injection timing measuring device to which the present invention is applied, and FIGS. 4A to 4D show waveforms of signals output from each component of this measuring device. Here, 21 is an amplifier circuit having an operational amplifier and a resistor, which amplifies the lift sensor signal S1 of the above-mentioned lift sensor 7 disposed in the fuel injection valve 1,
The amplified signal S6 (see the solid line in FIG. 4B) is supplied to one terminal of the comparison circuit 22. 23 is a crank angle sensor, which generates a pulsed crank angle signal S4 (see Fig. 4A) at a predetermined angular position of the crankshaft, and converts this signal S4 into a frequency-voltage converter (hereinafter referred to as an F-V converter). ) 24 and also to the reset terminal R of the flip-flop 25. The F-V converter 24 has an operational amplifier, a resistor, and a capacitor, and converts the crank angle signal S4 of the crank angle sensor 23 into a signal S7 (see the broken line in FIG. 4B) with a voltage level directly proportional to its frequency. Then, this signal S7 is supplied to the other terminal of the comparison circuit 22. For example, the comparison circuit 22 is
It consists of a comparator of an integrated circuit (IC) such as MC3301, and the signals S6 and F supplied from the amplifier 21
- Compares the variable voltage level signal S7 supplied from the V converter 24, and outputs the detection signal S8 (see FIG. 4C) when the signal S6 is at a higher voltage level than the signal S7. S8 is supplied to the set terminal S of the flip-flop 25. The flip-flop 25 receives the above-mentioned detection signal S8 and the crank angle signal.
S4, a signal S9 (fourth
(see Figure D).

In the fuel injection timing measuring device for a fuel injection valve configured as described above, the lift sensor signal S1 generated in response to a change in the load applied to the lift sensor 7 as the fuel injection valve 1 opens is transmitted from the lift sensor 7. taken out. This signal S1 is supplied to the amplifier circuit 21 to produce a signal as shown by the solid line in FIG. 4B.
Get S6. This signal S6 includes a normal signal component S61 indicating the displacement of the needle valve 3 of the fuel injection valve 1 equipped with the lift sensor 7 as described above, as well as the displacement of the needle valve of the fuel injection valve of the adjacent cylinder. It contains an abnormal signal component S62 caused by. on the other hand,
Angle signal output from crank angle sensor 23
S4 is supplied to an F-V converter 24 which converts it into a variable voltage level signal S7 in direct proportion to the frequency of the signal S4, which is supplied to a comparator circuit 22. Next, the comparison circuit 22 compares the amplified signal S6 and the variable voltage level signal S7 to obtain a detection signal S8 as shown in FIG. 4C.
At this time, the variable voltage level signal S7 is set so that it is always higher than the voltage level of the abnormal signal component S62.
- Since it is adjusted in advance with the V converter 24,
Abnormal signal components are removed from the detection signal S8, and only normal signal components are included.

Subsequently, the above-mentioned detection signal S8 and angle signal S4 are supplied to the flip-flop 25. The flip-flop 25 is led to the "H" level, which is one stable state, by the input of the signal S8, and the signal S4
A measurement signal S9 is obtained which is led to the "L" level, which is the other stable state, by the input of the signal S9. This signal S9 is
As shown in Fig. 4D, during the "H" level, T1 is the offset amount from the start of operation of the fuel injector 1 to the reference angular position, so by measuring the pulse width T1, the injection timing can be determined accurately. can be detected. In other words, since the F-V converter 24 is provided as a means for varying the detection level S7 of the lift sensor signal S4 or its amplified signal S6 according to the operating state of the engine, only desired normal signal components are detected. can do. This makes it possible to accurately measure injection timing and the like, and in turn, it is possible to significantly improve control performance.

FIG. 5 shows another example of a fuel injection timing measurement device to which the present invention is applied, and FIGS. 6A to 6G show waveforms of signals output from each component of the measurement device.
Here, 31 is a comparator, and this comparator 31 receives a lift sensor signal S1 (see the solid line in FIG. 6D) supplied from the lift sensor 7 to one terminal, and a predetermined signal S1 supplied to the other terminal. Comparison voltage level signal S2
(See the broken line in Figure 6D)
S11 (see FIG. 6E) is output, and this signal S11 is supplied to the set terminal S of the flip-flop 32.
The flip-flop 32 is in one stable state due to the input of the detection signal S11. Maintained at “H” level,
The signal S13 (see Fig. 6F) is returned to the other stable state "L" level by the input of the pulse-shaped angle signal S12 (see Fig. 6B) supplied from the first crank angle sensor 33 to the reset terminal R. ) and supplies this signal S13 to one terminal of the AND circuit 34. The first crank angle sensor 33 outputs a pulse signal S12 at every 120° reference angle of the crankshaft corresponding to the number of cylinders, for example, in the case of a 6-cylinder engine.
This 120° angle signal S12 is supplied to the flip-flop 32 and also to one terminal of the frequency divider circuit 35. 36 is a second crank angle sensor, and this sensor 36 is the lift sensor 7
A pulse signal S14 (see Fig. 6A) is generated every predetermined angle, for example, 720°, of the crankshaft of the cylinder in which the cylinder is disposed.
This 720° angle signal S14 is divided into 3 by frequency dividing circuit 3.
5 to the other terminal.

The 3 frequency divider circuit 35 is composed of a flip-flop IC such as CD4027, and as shown in FIG. 6C, after being reset by the 720° angle signal S14,
Open the gate with the pulse of the 120° angle signal S12 and set it to “H”
level, the gate is closed by the third pulse of the signal S12 generated from that time, and the so-called 3-frequency divided signal S15 is outputted to return to the "L" level.
S15 is supplied to the other terminal of the AND circuit 34.
The AND circuit 34 performs a logical product of the signal S13 supplied from the flip-flop 32 and the signal S15 supplied from the divide-by-3 circuit 35, and outputs a measurement signal S16 (see FIG. 6G).

With the above configuration, the lift sensor 7
lift sensor signal S1 and a predetermined voltage (e.g. 0.8V)
When the level signal S2 of is supplied to the comparator 31,
A shaped signal as shown in FIG. 6E is output from the comparator 31.
S11 is obtained. This shaped signal S11 and the 120° angle signal S12 from the first crank angle sensor 33 are supplied to the flip-flop 32 to obtain an output signal S13 as shown in FIG. 6F. Furthermore, the 120° angle signal S12 of the first crank angle sensor and the second crank angle sensor 3
6 and the 720° angle signal S14 are supplied to the frequency divider circuit 35 to obtain a signal S15 that maintains the predetermined crank angle angle range T3 at the "H" level as shown in FIG. 6C.
This signal S15 and the output signal of flip-flop 32
S13 is supplied to an AND circuit 34 to perform a logical product, thereby obtaining an output signal S16 from which abnormal signal components have been removed, as shown in FIG. 6G. That is, since the range in which the normal signal component of the pulse width T3 of the signal S15 described above is generated is determined in advance, this signal S15
By performing the logical product of the output signal S13 of the flip-flop 32 and the output signal S13 of the flip-flop 32, abnormal signal components can be removed, and only normal lift sensor signal components occurring in a predetermined section T3 within the 720° section of the crankshaft are detected. can do. Therefore, at signal S16, the reference angle is changed from the injection start timing (valve opening timing) TS.
The amount of offset T1 to TF can be accurately measured by counting the clock pulses (not shown) during that time.

As explained above, according to the present invention, the injection period can be detected by changing the comparison voltage level according to the operating conditions. It is possible to remove signal components from the injection valve and detect only the active components. Therefore, it is possible to accurately detect the fuel injection timing of the fuel injection valve of the diesel engine, and as a result, it is possible to obtain highly accurate and good control performance in injection timing control.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of a fuel injection valve with a lift sensor used in the present invention, FIGS. 2A to D are waveform diagrams showing output signals from each terminal of a conventional device, and FIG. A block diagram showing an example of a device to which the present invention is applied, FIGS. 4A to 4D are waveform diagrams showing output signals from each terminal thereof, and FIG. 5 is a block diagram showing another example of a device to which the present invention is applied. 6A to 6G are waveform diagrams showing output signals from each terminal. 1...Fuel injection valve, 2...Fuel supply passage, 3...
... Needle valve, 4 ... Nozzle hole, 5 ... Spring, 6 ... Ground plate, 7 ... Lift sensor, 8 ... Electrode, 21 ...
Amplifier circuit, 22... Comparison circuit, 23... Crank angle sensor, 24... F-V converter, 25... Flip-flop, 31... Comparator, 32... Flip-flop, 33... First crank angle sensor, 3
4...AND circuit, 35...3 frequency divider circuit, 36...
...Second crank angle sensor.

Claims (1)

[Claims] 1: a lift sensor that outputs a first signal corresponding to the displacement of the needle valve of the fuel injection valve; a means for outputting a second signal that changes in response to engine operating conditions; means for comparing the signal with a second signal to obtain a third signal corresponding to the opening of the fuel injection valve, and detecting the injection timing of the fuel injection valve based on the third signal. A diesel engine fuel injection timing measuring device characterized by: