JPS5970880A - Detecting device for injection timing - Google Patents

Abstract

PURPOSE:To enable determination of abnormality of a vibration sensor itself and its mounting condition, by comparing a reference value for detection of the fuel injection timing of the vibration sensor with a predetermined comparing value for detection of a sensor trouble. CONSTITUTION:A filter amplifier 2 extracts the signal, on a specified frequency band, of signals S1 from a vibration sensor 1 to amplify the signal which is outputted as a detected signal S2. A detection circuit 3 outputs a half-wave signal S3, obtained through rectification of the signals S2, to a reference value generating circuit 4. The circuit 4 averages this signal by an integration circuit to produce a reference value Sr1. Thereafter, a comparator 5 compares the detected signal S2 with the reference value Sr1, and when the S2 becomes lower than Sr1, fuel injection starts and a pulse signal P1 for repetition of ''H'' and ''L'' is outputted only during a time between the fuel injection start and completion of fuel injection. Based on the pulse signal P1, a vibrator 6 outputs a signal P2 becoming ''L'' only during a period T2. A comparator 7 compares the reference value Sr1 with a predetermined comparison value Sr2, and only when the Sr1 is lower than the Sr2, the comparator outputs a signal P3 of ''L''. This permits discrimination of absence of any trouble on the vibration sensor itself and its mounting condition.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection timing detection device, and more particularly to a device capable of determining an abnormality in a vibration sensor itself or its supplement installed in the fuel system of an engine.

For example, in a diesel engine, it is important to accurately detect the fuel injection timing in dynamic fuel injection conditions during engine operation, especially in order to accurately set the timing of fuel injection from the engine's fuel injection valve. .

Therefore, various fuel injection timing detection devices have been developed in which a vibration sensor is attached to the fuel system of the engine and the fuel injection timing is detected using a detection signal based on the output of the vibration sensor.

By the way, the conventional device of this kind is, for example,
No. 42922, Japanese Patent Application Laid-open No. 117071/1983,
As is clear from the description in JP-A-56-20757, etc., it is assumed that the vibration sensor itself or its supplement is completely normal, and an abnormality detection function has been added.・Na℃・.

However, considering the structure of the vibration sensor and the environment in which it is located, it is not preferable to rely on such a premise.

In other words, vibration sensors usually have a structure in which an attachment with a piezoelectric element is screwed onto a fuel vibrator (for example, in a fuel system), and if the screw is not properly screwed on, the detection sensitivity may drop significantly. Even if the screws are completely tightened, the screws may loosen due to vibration, and the piezoelectric element itself or the joint between its output terminal and the signal line may become fatigued due to vibration, resulting in a decrease in detection function. This is because there is.

Therefore, an object of the present invention is to provide a fuel injection timing detection device that can determine an abnormality in the vibration sensor itself or its supplement.

Therefore, in the fuel injection timing detection device according to the present invention, a detection signal based on the output of a vibration sensor that probes the fuel system of the engine is compared with a reference value obtained by equalizing this detection signal by 517. In conventional devices that detect fuel injection timing by Or, it is designed to determine whether there is any abnormality in the installation.

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention.

In the figure, a vibration sensor 1 is located at a location where vibrations in the fuel system of a diesel engine can be detected, such as a spill tube of a fuel injection valve, and outputs a signal S1 in response to vibrations in the fuel system.

The filter amplifier 2 extracts and amplifies a signal in a specific frequency band from the signal S+ from the vibration sensor 1, and outputs the amplified signal S+ as a detection signal S2.

The detection circuit 3 performs, for example, half-wave detection (rectification) on the detection signal S2 from the filter amplifier 2 and outputs a resulting half-wave signal S3 to the reference value generation circuit 4.

For example, as shown in FIG. 2, the reference value generation circuit 4 includes an anacog switch AS that is turned off only while a pulse signal P2, which is also output from a monostable multivibrator (O3) 6 to be described later, is input, and a resistor. It is composed of R1, R2, a capacitor C9, and an integrating circuit including an operational amplifier OP+, and has the following functions.

That is, the pulse signal P2 from O86 is, for example, the third
As shown in the figure, since the signal is at a low level "L" only during the period T2 during which vibrations associated with fuel injection occur and the temperature rises, the signal level of the gate is low. From the analog switch AS that turns off only when it is “L”,
Of the half-wave signal S3 from the detection circuit 3, the period TI in FIG.
, T3 and the like are output.

Then, a signal indicating this background noise "/1 (
, (=/iH>1) is averaged by an integrating circuit to obtain a reference value Sr+ that is slightly larger than the amplitude value of the signal indicating background noise as shown by the dashed line in FIG.
form. Although the reference value S ]-1 is a negative value due to the circuit configuration of the reference value generating circuit 4, it is shown as a positive value in FIG.

It should be noted that this reference value generating circuit 4, during the period T+ in FIG.
During T3, the half-wave signal S3 is sampled, and the period T2 is
It is constructed with a so-called Zanople hold circuit that holds the numbering value for a period of time, but it is not always necessary to use such a construction, and depending on how the time constant is set, the anacog switch AS can be omitted. It's okay.

The first comparator 5 receives a detection signal S from the filter amplifier 2.
2 and the reference value Sr+ from the reference value generation circuit 4, and only when S2<:, Srl, that is, from the start to the end of fuel injection.
, SS , (, l/ is repeated and a pulse signal, Pl, is output.

IJ that outputs a pulse with a slightly longer pulse width
The pulse signal P2 is a mono-multiple (re-trigger type), and is at a low level "L" only during the period T2 shown in FIG. 3 based on the input pulse signal P1.
Output.

The second comparator γ is, for example, a resistor R3 as shown in FIG.
~R7 and an operational amplifier OP2, the reference value generating circuit 4 outputs the reference value Sr+ (negative value) and a predetermined comparison value Srz (negative value) as shown by the broken line in FIG. A signal P3 of low level "L" is output only when Sr+<Sr2.

By the way, the reason for making such a comparison is as follows.

That is, the small amplitude signal of the half-wave signal S3 during periods TI and T3 shown in FIG. 3 mainly indicates mechanical vibrations of the fuel injection pump, engine, etc., and is necessary if the vibration sensor 1 itself and its supplement are normal. If you check whether the reference value S1.1 obtained by averaging these small amplitude signals is larger or smaller than the predetermined comparison value Sr2, the vibration sensor 1
The presence or absence of abnormalities can be determined.

The top dead center sensor 8 is a gap sensor that detects a top dead center mark provided on the outer periphery of the engine's flywheel at a position corresponding to the second dead center of the first cylinder, and detects the top dead center mark. The signal S4 is output to the signal processing circuit 9 every time.

The signal processing circuit 9 shapes the waveform of the signal S4 from the top dead center sensor 8 and outputs the resulting signal as a top dead center signal P4.

Next, a microcomputer 1 which also serves as a determining means
The operation of 0 will be explained.

The microcomputer 10 includes an I/O Kai 7 Turf Ace ('I10) 11 and a central processing unit (CPU) 1.
2, a data memory (RAM) 13, a program memory (ROM), etc., and executes program processing as shown in the flowchart of FIG.

First, after initializing the entire circuit system in the microcomputer 10, the second comparator 7 in FIG.
Execute a sensor test routine to determine abnormalities in the vibration sensor 1 and the top dead center sensor 8 based on the comparison result of the signal P3 and the top dead center signal from the signal processing circuit 9. After that, based on the pulse signal P2 from O86 and the top dead center signal P4 in Fig. 1, a measurement diagnostic routine is executed to measure the fuel injection timing and determine whether the four measurement results are acceptable or not. do.

The sensor test routine according to the present invention will be explained below with reference to the flow diagram of FIG.

The fuel injection timing in the open side diagnosis routine is measured, for example, by measuring the time from the falling edge of the pulse signal P2 to the first top dead center signal P4 that comes after the pulse signal P3, and corresponding to the measured time. This can be done by calculating the crank angle.

In FIG. 5, 5TEP1 reads the signal P3 output from the second comparator 7 in FIG.

5TEP2 Check whether the signal P3 read in 5TEPl is low level "L", and
(If it's 5TEP3, if it's low level L, then it's 5T.
EP] Proceed to l respectively.

5TEP 3 Read the top dead center signal P4,
A read flag is set only when this top dead center signal P4 is read during a predetermined period.

5TEP4 Check whether the read flag is set in 5TEP3. If it is set, proceed to 5TEP5, and if not, proceed to 5TEPIO.

5TEP5 Since it is determined that the read flag is set in 5TEP4, the engine wants to be operated, so the signal P3 is at level ``H'' even though the engine is being operated. , it is determined that there is something wrong with the vibration sensor 1.

Therefore, first, a message should be displayed on the display 15 in FIG. 1 to prompt the user to check the installation of the vibration sensor 1.

5TEP6 The operator checks the installation condition of the vibration sensor 1 by looking at the display 15 and following the instructions, and when the check is completed, sends a signal indicating completion of the installation check to the microcomputer 10 using a temperature input means (not shown). input.

5TEP7 5TEP] and reads the signal -P3 again.

5TEP8 Check whether the signal P3 read in 5TEP7 is low level "L", and set it to low level "H".
“If it’s 5TEP9, if it’s low level” “L” then it’s 5TEP
Go to 18 respectively.

Although the signal P3 is at a high level "H" even though the vibration sensor 1 is completed, it is determined that there is an abnormality in the vibration sensor 1 itself, and the vibration sensor 1 is displayed on the display 15 in FIG. In addition to displaying that the vibration sensor 1 is defective, a display prompting repair or replacement of the vibration sensor 1 is also displayed.

5TEP, 10 Since it is determined that the reading flag is not set at 5TEP4, it can be determined that the top dead center sensor 8 has not been detected.

Therefore, at 5TEP2, the signal P3 becomes high level ももJ(/
/ Since it is also confirmed that the vibration sensor 1 is installed together with the top dead center sensor 8, a message is displayed on the display 15 in FIG.

Then, the worker follows the instructions on the display to actually check whether the sensor is installed or not, and if it is not installed,
Install the sensor.

At this time, if the engine is running and both sensors have been properly installed, but a message prompting you to install the sensor appears on the display 15, then both sensors are The worker determines that it is malfunctioning.

And, at least vibration sensor 1 will be published.
Or, if the vibration sensor 1 that was inspected and installed properly is done, the signal P3 will be determined to be low level "L" at 5TEP2, so 5TEP1
You can exit the loop of ~4,10 and proceed to 5TEP■1.

5TEP, I 1.12 5TEP3, Perform the same process as lI, and if the read flag is set, 5TE
P1. s, stand at ℃, otherwise proceed to 5TEP13 respectively.

5TEPI 3,] 4 It is determined that the read flag is not set in 5TEPI 2 (Rodame, first 5T
At EP13, a message prompting the user to check several phrases of the top dead center sensor 8 is displayed on the display 15 shown in FIG. If the dead center sensor 8 is not installed, it is installed, and then a signal indicating the completion of the work is input to the microcomputer 10.

5TEPI 5, I 6 and again 5TEPI
Perform the same processing as 1 and 12, and if the read flag is set, go to 5TEP 18, otherwise go to 5T
Proceed to EP17.

5TEPI 7 5TEPI The reading flag is raised again at 5TEPI G and it is determined that there is no °C.This time, it is determined that the top dead center sensor 8 itself is defective, and the display 15 in Fig. 1 indicates that the top dead center sensor 8 itself is defective. The repair or replacement of the top dead center sensor 8 is not prompted and is displayed together with the display.

5TEP] 8 Signal P3 is low level at 5TEP8''
If it is XL //, the read flag is set at 5TEPI 2 and I 6 and it is determined that it is °C, so both sensors can be certified as normal.For example, both sensors are normal and the sensor test is completed. After performing processing such as displaying a message indicating that the measurement has been performed on the display 15 in FIG. 1, the process proceeds to the next step routine, the measurement diagnosis routine (FIG. 4).

Although the flowchart shown in FIG. 5 describes an example in which the display prompting the vibration sensor 1 and the top dead center sensor 8 to check +1 is performed once each, it is preferable to perform each multiple times. However, even if it is determined that there is an abnormality, it is determined that the sensor is defective.

In the flowchart of FIG. 5, the case where both the vibration sensor 1 and the top dead center sensor 8 are defective is not displayed, but such a case may be determined and displayed.

Furthermore, in the block diagram of FIG.
2 is used, but it goes without saying that a half-wave signal obtained by half-wave detection of this detection signal S2 or its envelope signal may be used instead of the detection signal S2.

As mentioned above, the fuel injection timing detection device according to the present invention can detect abnormalities in the vibration sensor itself or its installation, so the reliability of the device is improved7 and it is highly practical. Become.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG.
The figure is a circuit diagram showing a specific example of the reference value generating circuit 4 and the second comparator in FIG. 1, and FIG.
．． 2 is a signal waveform diagram for explaining the operation; FIG. 4 is a flow diagram of a program executed by the microcomputer of FIG. 1; and FIG. 5 is a flow diagram showing a sensor test routine in FIG. 1... Vibration sensor 2... Filter amplifier 3...
Detection circuit 4... Reference value generation circuit 5... First comparator 6... Monostay full multivibrator 7...
second comparator

Claims (1)

[Claims] 1. A fuel injection timing detection device that detects fuel injection timing by comparing a detection signal based on the output of a vibration sensor attached to the engine's fuel system with a reference value obtained by averaging the detection signal. The fuel injection timing is characterized by comprising a comparison means for comparing the reference value and a predetermined comparison value, and a determination means for determining whether there is an abnormality in the vibration sensor based on the comparison result by the comparison means. Detection device.