JPS633145B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a signal discrimination device used in a fuel injection timing detection device in a multi-cylinder engine.

In engines such as diesel engines that are injected with fuel by a fuel injection valve, the sound (vibration) generated by the fuel injection valve is used as a method to detect when the fuel injection valve actually starts injecting fuel. There is a known method of detecting the fuel injection timing using a piezoelectric sensor and based on the detection. The sounds generated by a fuel injection valve include the injection sound that occurs when the valve element opens and fuel is injected, the collision sound that occurs when the valve element fully opens and collides with the stopper, and the valve element. The collision noise that occurs when the valve closes and collides with the stopper can be roughly divided into three types:
In order to accurately detect the fuel injection start timing, it is necessary to detect the injection sound. This injection sound is an ultrasonic wave with a frequency of 100kHz to 200kHz, and the sound pressure level is extremely low compared to other sounds, making it difficult to detect. Regarding this issue, please refer to the patent application No. 54-97943 filed by the same applicant as the applicant.
This problem can be solved by combining a piezoelectric element and a filter damper device of a parallel resonant circuit, as proposed in No.

If only one fuel injection valve is provided for one engine, the fuel can be injected by feeding the voltage signal from the piezoelectric element that has passed through the filter damper device to a signal processing circuit including a comparator, monostable circuit, etc. The injection start timing can be detected, but if multiple fuel injection valves are installed in one engine, such as in a multi-cylinder engine, the piezoelectric sensor attached to one fuel injection valve will detect the injection start timing. A voltage signal is generated based on the sound generated in the engine, and a voltage signal is also generated based on the sound generated inside the engine, and as a result, unnecessary voltage signals are generated relative to the voltage signal that should be detected. In other words, the magnitude of the noise was approximately 1,000 times greater, making it difficult and nearly impossible for the filter device to distinguish between the voltage signal to be detected and the noise.

In view of the above-mentioned points, the present invention detects the fuel injection timing of a multi-cylinder engine, especially the fuel injection start timing, even if the level of the voltage signal from the piezoelectric sensor is very small compared to the noise. The object of the present invention is to provide a signal discriminator that can perform the following steps.

According to the present invention, this purpose is to compare the voltage of a voltage signal from a piezoelectric sensor sensitive to vibration of a fuel injection valve of a multi-cylinder engine with a first comparison voltage, and generate a signal in accordance with the comparison result. a monostable circuit operated by a signal from the first comparator; a delay circuit to which a voltage signal from the voltage signal generation source is applied; and a monostable circuit to which a voltage signal is applied from the delay circuit. and a second comparison voltage different from the first comparison voltage, and generates a signal according to the comparison result, and has a strobe terminal to which a signal is applied from the monostable circuit. This is achieved by a signal discriminator for detecting fuel injection timing of a multi-cylinder engine having a comparator.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing one embodiment of a signal discrimination device for detecting fuel injection timing for a multi-cylinder engine according to the present invention. In the figure, 1 is a piezoelectric sensor, 2 is a filter device, 3 is a first comparator, 4 is a monostable circuit, 5 is a delay circuit, 6 is a second comparator, and 7 is a Each monostable circuit is shown.

The piezoelectric sensor 1 is attached to one fuel injection valve of a multi-cylinder engine (not shown), and generates a voltage signal in response to detected vibrations (sound). This voltage signal is input to the filter device 2. The filter device 2 may be a parallel resonant circuit filter damper device as proposed in Japanese Patent Application No. 54-97943 as mentioned above, or a combination with other general band pass filters. outputs a signal as shown in FIG. 2a.
In this signal, ~ indicates a signal generated based on the opening/closing of the fuel injection valve of each cylinder of the engine. In this case, the piezoelectric sensor 1 is
It is assumed that it is installed in the number cylinder. Furthermore, in the above-mentioned signals, the symbol X is the voltage signal generated based on the injection sound, the symbol Y is the voltage signal generated based on the collision sound when the valve element is fully opened, and the symbol Z is the voltage signal generated based on the collision sound when the valve element is fully opened. It shows the voltage signal generated based on the collision sound of time. Code X in detecting fuel injection start timing
All voltage signals other than those shown are noise. The sound pressure level of the voltage signal The injection noise generated by the fuel injection valve is not detected. The filter device 2 is of course configured to have a resonance frequency or center frequency and a bandwidth matching the frequency of the voltage signal to be detected, that is, the voltage signal X generated based on the injection sound.

The voltage signal that has passed through the filter device 2 is input to a first comparator 3 and a delay circuit 5. The first comparator 3 may be a masking comparator;
A comparison voltage V _cf having a value greater than the voltage of the voltage signal X based on the injection sound and smaller than the voltage of the voltage signal Y based on the collision sound is compared with the voltage signal that has passed through the filter device 2, and the voltage signal is determined. An ON signal is output to the monostable circuit 4 only when the voltage is greater than the comparison voltage V _cf. monostable circuit 4
operates based on the ON signal from the first comparator 3,
As shown in FIG. 2b, a pulse signal with a pulse width t ₁ is generated. monostable circuit 4
The pulse width t ₁ of the pulse signal generated by is smaller than the pulse width corresponding to the time T ₁ between one fuel injector injecting fuel and then another fuel injector injecting fuel. , and is larger than the pulse width corresponding to the time T ₂ from when a voltage signal is generated in the valve element of one injection valve based on the impact sound until it disappears. For example, in a four-cylinder engine, the maximum engine speed used is 1500 rpm.
Then, the time _T1 corresponds to 20 msec. In addition, since the collision sound of the injection valve is generated and the time for it to disappear is usually about 5 m to 8 seconds, the pulse width
It is sufficient that t ₁ is larger than the pulse width equivalent to 8 msec. The pulse signal of the monostable circuit 4 is input to the strobe terminal 8 of the second comparator 6 as a strobe signal.

The delay circuit 5 is an analog signal delay circuit,
The delay time T ₃ is shorter than the duration time T ₄ of the injection sound, and may be about 1 μsec to 2 μsec. The delay circuit 5 outputs a voltage signal as shown in FIG. 2c to the second comparator 6.

The second comparator 6 is constituted by a select comparator having a strobe terminal 8. This second comparator 8 compares the comparison voltage V _cs , which is smaller than the voltage of the voltage signal X based on the injection sound, with the voltage of the voltage signal from the delay circuit 5, as shown in FIG. 2d. The ON signal is generated only when the voltage of the voltage signal is higher than the comparison voltage V _cs , and the ON signal is output only when the ON signal is not applied to the strobe terminal 8.

Only when the fuel injection valve to which the piezoelectric sensor 1 is attached (in this embodiment, the fuel injection valve attached to the first cylinder) injects fuel, the piezoelectric sensor 1 outputs voltage signals Y and Z. First, a voltage signal X is generated based on the injection sound. Therefore, the second comparator 6 has a voltage higher than the comparison voltage before the ON signal is input to the strobe terminal 8 only when fuel is injected by the fuel injection valve to which the piezoelectric sensor 1 is attached. When given a voltage signal, it generates a pulse wave as shown in FIG. 2e. The pulse width of this pulse wave corresponds to the duration of the injection sound minus the delay time of the delay circuit 5.

The pulse signal output from the second comparator 6 is given to a monostable circuit 7, where it is shaped into a pulse signal with an appropriate pulse width t ₂ in consideration of the interface with other electric circuits. be done.

As is clear from the above description, the signal discrimination device according to the present invention discriminates signals by considering the magnitude of the voltage level of the voltage signal and the periodic order of generation of the voltage signal. Signal pattern recognition can be easily performed without using .

In the above, the present invention has been described in detail with respect to specific embodiments, but it will be understood by those skilled in the art that the present invention is not limited thereto and that various embodiments can be made within the scope of the present invention. It should be obvious.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of a signal discriminator for detecting fuel injection timing for a multi-cylinder engine according to the present invention, and FIG. 2 is a waveform diagram of signals at various parts of FIG. 1...Piezoelectric sensor, 2...Filter device, 3...
...First comparator, 4... Monostable circuit, 5... Delay circuit, 6... Second comparator, 7... Monostable circuit,
8...Strobe terminal.

Claims (1)

[Claims] 1 a first comparator that compares a voltage signal from a piezoelectric sensor sensitive to vibrations of a fuel injection valve of a multi-cylinder engine with a first comparison voltage and generates a signal according to the comparison result; a monostable circuit operated by a signal from a first comparator; a delay circuit to which a voltage signal from the voltage signal generation source is applied; and a delay circuit to which a voltage signal from the delay circuit is applied; and a second comparator that compares the voltage with a second comparison voltage different from the voltage, generates a signal according to the comparison result, and has a strobe terminal to which the signal is applied from the monostable circuit. A signal discriminator for detecting fuel injection timing for a multi-cylinder engine, characterized in that: