JPS6079161A - Combustion diagnostic device of diesel engine - Google Patents

Abstract

PURPOSE:To widely improve the workability of diagnosis by using a sensor to detect a prominent and high-level signal for the injection end timing, using a stroboscope to determine the injection end timing during an actual operation, and obtaining whether the diagnosis result is good or bad in a binary signal. CONSTITUTION:A vibration or acoustic sensor 12 is fitted to the head of a fuel injection valve 3, a signal in response to the injection end timing is extracted in a signal processing circuit 32 from its output signals, and this signal is delayed by an optional time to trigger a stroboscope 33. In addition, the output level of a reference voltage generator 18 is set in response to the type of a diagnosed device 26, the standard crank angle information is read out from a standard value memory 35, and a delay time regulator 21 is operated so that the specific cylinder TDC mark 30 can be observed in coincidence with the reference TDC mark 29. When the injection end timing of the diagnosed device is normal, that effect is displayed on a display unit 37 via the output of a comparator 36.

Description

[Detailed description of the invention] The present invention relates to a combustion diagnostic device for a diesel engine.

The performance of a diesel engine is governed by the combustion of fuel injected into the cylinder, and the combustion state is governed by the operation of the fuel injection system. The relationship between the operation of the fuel injection system and combustion can be expressed, for example, as shown in FIG. This figure 441 is an example of idle-link operation, and when fuel is discharged from the fuel pump and the cylinder pressure reaches the opening pressure of the fuel valve, fuel injection starts, but from the discharge of the fuel pump to the fuel valve opening pressure. Before injection starts, there is a time delay corresponding to the length and volume of the high pressure fuel pipe) and the opening pressure of the fuel valve, that is, an injection delay τl. Furthermore, since the fuel has an ignition delay, combustion starts after the fuel is injected with a delay of the ignition delay τ2. Therefore, in order to achieve proper combustion in the cylinder, the discharge timing of the fuel pump must be set in consideration of the injection delay τ11 and the ignition delay B mentioned above. If the settings become incorrect due to long-term use, combustion abnormalities will occur and engine performance will deteriorate.

In this way, combustion in a Daicel engine is controlled by the fuel injection timing, so whether it is desirable to adjust the injection timing by directly measuring the injection timing and diagnosing the combustion state. Since there is no simple means to directly measure the injection delay and ignition delay times, we mainly estimate the injection delay and ignition delay times based on experimental data. A method of adjustment using cell lift is used. However, this method requires disassembling part of the fuel pump, which has a complex structure, and in the case of a diesel engine installed in a car, it is extremely difficult to adjust it while it is still installed in the car. It is a cone.

Furthermore, an excellent method has been known in the past that can detect the injection timing without modifying the engine while the engine is in operation. This method allows a sensor to be attached to the outside of the engine and can be easily measured while still in the vehicle. Next, this method will be explained in detail together with the behavior of the fuel injection system.

The fuel injection system of a diesel engine is composed of elements such as a fuel boss (1), a high pressure pipe (2), and a fuel injection valve (3), as shown in FIG. 2, for example. plunger (4) of the fuel pump (1) driven by a cam (not shown)
When the plunger chamber (5
) is rapidly compressed, pushes up the discharge valve (6), passes through the high pressure pipe (2), and reaches the fuel injection valve (3)K.

Plunge t) (4) rises further and the pressure within the system rises, and when this pressure overcomes the biasing force of the spring (7) of the fuel injection valve (3), the needle (8) moves upward! Pressurized fuel oil is ejected from the nozzle hole (9) starting at 2 in + [direction of arrow Y], and fuel injection is started. Fuel injection continues while the plunger (4) further rises, but when it reaches the notch αQ of the plunger (4) or the fuel supply hole (b), the fuel oil in the system begins to flow backwards, and the pressure within the prefecture decreases. The needle (8) drops rapidly and the fuel injection ends.

In such a fuel injection system, a rapid flow of fuel oil occurs along with a backflow just before the start of fuel injection and the end of fuel injection, and vibration and noise signals are generated from the fuel injection system. ing. In this case, the backflow just before the end of fuel injection occurs when the pressure level is suddenly released from a high pressure level to a level close to atmospheric pressure, so the flow velocity is larger than the flow velocity at the start of injection. The level of the acoustic signal is greater than at the start of injection.

Therefore, a sensor is attached to the outside of the components that make up the fuel injection system, and the signal obtained by amplifying the sensor detection signal is filtered through an appropriate high bass filter with a cutoff frequency of 20 KHz or higher, or a signal that is included in a band of 20 KHz or higher. When processed using an appropriate Basid bus filter, a signal 4j with a characteristic pattern as shown in FIG. 8 is obtained. Fig. 8 shows an example of a signal obtained by attaching a sensor to the head of the fuel injection valve (3) and the outlet pipe joint of the fuel pump (1), and also shows the fuel injection signal representative of the operation of the fuel injection system. An actual measurement example of the needle lift of valve (3) is also shown. The fuel injection timing (6) in Fig. 8 and the peak occurrence timing of both signals @
If we examine the correlation with respect to the change in the engine speed at 0, we will see the results shown in Figure 4. The timing of peak occurrence of the signal from the nine sensors attached to the head of the fuel injector (3) shows a good correlation with the end of fuel injection, and this sharp peak signal is a signal due to the sudden backflow just before the end of fuel injection. I understand. Also,
It can be seen that this sharp signal ζ occurs significantly and reliably in any range of engine speed.

From the above, it is considered most appropriate to use the injection path signal obtained from the head of the fuel injection valve (3) for diagnosis. Figure 6 shows an example of setting the injection path as described above for four representative models, Ml-M4. It is possible to understand the characteristics of Furthermore, this Figure 6 also shows the discharge timing of the fuel pump for each model Ml-M4, which was measured separately, or because these engines have an auto-timer (automatic advance device), the rotation speed As the value increases, the discharge timing becomes earlier, and we can clearly understand the operating characteristics of the automatic timer. The above-mentioned injection path 9 is obtained in accordance with such characteristics of the discharge timing, and by detecting the injection path, the injection characteristics due to the operation of the auto-timer can be well understood.

Furthermore, by establishing the correlation between the discharge timing and the injection path in advance, it is possible to determine the operating characteristics of the auto-timer from the characteristics of the injection path. In addition, as mentioned earlier, the proper combustion state in the engine cylinder can be obtained by proper injection timing (injection path), so by diagnosing the appropriateness of the injection timing, it is possible to determine whether the combustion condition in the cylinder is good or not. Can be diagnosed directly. Of course, it is possible to diagnose the suitability of the combustion state by detecting the discharge timing as described above, but it is not easy to dynamically set the discharge timing from the engine operating state.
Furthermore, in this case, the diagnosis is indirect, taking into consideration the influence of factors such as injection delay and ignition delay. On the other hand, the above-mentioned diagnosis by detecting the injection path is direct, and the signal of the injection path appears reliably and significantly under various operating conditions, and is easy to detect. It is desirable and practical to perform the diagnosis by detecting the injection path.

FIG. 6 shows a specific configuration of a detection device that detects the injection path from the output signal of the sensor (2) attached to the head of the fuel injection valve (3) of the Nol cylinder.

The output signal of the sensor (2) is amplified by an amplifier (to) and the characteristics of the signal are extracted by a filter Q4.

The signal is further amplified by an amplifier (g) and then processed by an absolute value circuit Q. and an envelope detection circuit <17) to obtain a signal as shown in FIG. 8 described above.

The steep rise of this signal represents the injection path timing B, and in order to detect this timing B, this detection device is constructed as follows.

The output signal of the envelope detection circuit (b) is compared with the constant voltage output from the reference voltage generator (to) by a comparator a, and the output signal of this comparator a triggers a monostable multi-type ibrator (e). Therefore, only the rising signal of the injection path is detected in the output of the monostable multivibrator (e). Is the binary signal of this monostable multivibrator (E) output a delay amount or a delay time adjuster? ) is applied as a trigger signal to the strobe drive circuit (2) through a variable delay circuit, and the strobe drive circuit () causes the discharge tube to emit light at the timing of the rise of the injection path. 2) is a rotating body directly connected to the crankshaft of the engine to be diagnosed in which the sensor (2) is installed.
represents the rotation direction, and the specific cylinder (here No.
A specific cylinder J TDC mark (To) is attached in advance so that it matches the reference TDC mark on the fixed side when the T series (T) reaches a predetermined angle, for example, top dead center (crank angle 0°). This particular cylinder J TDC mark (to)
When the reference TDC mark (2) and the reference TDC mark (2) are irradiated with the irradiation light 00 of the discharge tube (2) and read, if the delay amount (in the delay circuit) is zero, the specific cylinder TDC mark (2) will be a solid line passing through the reference TDC mark (2). observed in position. Then, as the delay time adjuster (E) is operated to increase the delay time of the delay circuit 4, the amount of deviation between the reference TDC mark (2) and the specific cylinder TDC mark gradually decreases and the target can be read. If the time required for one cycle of the diagnostic engine is the delay time from the top dead center of the Nol cylinder at the T1 injection end timing, t, then when the delay circuit block is delayed by (T-t), the specific cylinder will change as shown by the virtual line. The J TDC mark matches the standard TDC mark and can be read. That is, irradiation light 0])
Irradiate with specific cylinder J TDC mark (to) or reference T
It is possible to read at what crank angle from the top dead center of the Nol cylinder the injection point has come from the operation amount of the delay time adjuster q when it is read in accordance with the DC mark). However, in the past, the delay time adjuster 3
The measuring person compares the measured crank angle read from the source with the standard crank angle of the known injection timing depending on the model of the device being diagnosed to determine whether the injection timing of the device being diagnosed is good or not. The current situation is that it is not possible to improve the workability of checks and maintain a constant reliability of judgments.

Therefore, the present invention detects a remarkable high-level signal corresponding to the injection timing during actual operation by detecting a remarkable high-level signal corresponding to the injection timing using a vibration sensor or an acoustic sensor without performing any special processing on the finished product. An object of the present invention is to provide a combustion diagnostic device for a Dai-cell engine that can obtain a binary signal indicating whether the diagnosis result is good or bad when directly observed using a stroboscope, even if the measurement person makes a diagnosis. .

The combustion diagnosis device for a diesel engine of the present invention detects vibration or sound detection t'J"j- mounted on the outside of the fuel injection valve of the device to be diagnosed, and a signal corresponding to the timing of the fuel injection path from the output signal of this sensor. a signal processing circuit that detects the fuel injection timing by extracting this extracted signal at a reference level and outputting this detection signal after delaying it by an arbitrary amount of time, and triggering the output signal of this signal processing circuit. A stroboscope that outputs a signal, and a comparator that inputs a measurement signal corresponding to the arbitrary time of the signal processing circuit and a known standard value determined by the model of the device to be diagnosed and detects a match between the two is provided. The reference IDC mark and specific cylinder 4T of the device to be diagnosed by the scope
Irradiate the DC mark with the reference TDC mark and specific series:
The present invention is characterized in that the measurement signal at the time of reading a match with the TDC mark is compared with a standard value by a comparator to determine whether it is good or bad.

Hereinafter, one embodiment of the present invention will be described based on FIG. 7.

Note that the same reference numerals are given to those having the same functions as those in the wJG diagram, and the explanation thereof will be omitted. 2) extracts a signal corresponding to the end of injection from the detection signal of the sensor (6) attached to the head of the fuel injection valve (3) of a specific cylinder, and outputs this signal after delaying it by an arbitrary amount of time. Signal processing circuit, (
(to) is a strobe scope that uses the output signal of () as a trigger signal, and a time-to-angle converter that provides rotation speed information of the device to be diagnosed (e), and the delay time adjuster (eA). The delay time designation information Dt from the delay circuit to the delay circuit is inputted, and the delay time opening t by the delay circuit @ is converted into crank angle information Ds. (b) is an angle display that digitally displays crank angle information Ds as a crank angle, and (to) is a standard value meter in which the end of injection timing of each model of diesel engine is written as the crank angle difference from the standard TDC mark member. S-c! 4 is the standard crank angle information DR read out from the standard value memory (to) according to the model of the device to be diagnosed (e) and the crank angle information D obtained by measurement.
A comparator that compares s with s detects a match and inverts the logic level of the output. @ is the diagnosis result display and the comparator (to)
Detects the reversal of the logic level and displays "normal".

With this configuration, depending on the model of the device to be diagnosed (1), the output level of the reference voltage generator () can be set, and the standard crank angle information (DR) can be set from the standard value menu (to).
) and operate the delay time adjuster Q so that the specific cylinder J TDC mark (1) matches the standard TDC mark and can be observed, the device to be diagnosed (E)
If the injection path timing is normal, a match is detected by the comparator (to), and "normal" is displayed on the diagnostic result display (b). Therefore, the tester can diagnose pass/fail by simply specifying the output level of the reference voltage generator (G) and standard crank angle information (DR) according to the model of the device to be diagnosed and adjusting the delay time adjuster. The results are obtained (1) and do not require the operator to carry out an examination of the measurements himself.

In addition, by setting the standard crank angle information DR in the above embodiment to information with a certain tolerance, more practical diagnosis can be performed.

As explained above, according to the easel engine combustion diagnostic device of the present invention, the measurement result is compared with the standard value in the comparator to generate a binary signal representing the judgment result of pass/fail.
It is possible to diagnose the quality of the end of injection timing without having to examine the measured values by the operator himself as in the past, greatly improving the workability of diagnosis, and maintaining the reliability of diagnosis at a constant level. It is.

[Brief explanation of drawings]

Figure 1 is a diagram of the relationship between the operation and combustion of the fuel injection system of a diesel engine, the IP52 diagram is a schematic sectional view of the fuel injection system, Figure 8 is a diagram of the relationship between sensor detection signals and the needle lift of the fuel injection valve, and Figure 8 is a diagram of the relationship between the sensor detection signal and the needle lift of the fuel injection valve. Figure 4 is a diagram of the relationship between the peak occurrence time and the end of injection time and the engine speed, Figure 5 is a characteristic diagram of the measurement results of a specific experimental example of the GS4 diagram, Figure 6 is a diagram of the configuration of the diagnostic device for the control FIG. 7 is a configuration diagram of an embodiment of the diagnostic device of the present invention. (1)...Fuel pump, (2)...High pressure pipe, (3)
... Fuel injection valve, (4) ... Plunger, (5).
...Plunger chamber, (6)...Discharge valve, (7)...
Spring, (8)... Needle, (9)... Nozzle hole, a groan... Notch, aυ... Fuel supply hole, (2)... Sensor, (to) (g).・・Amplifier, α → ・・Filter, Q・・Absolute value circuit, αη・・Envelope detection circuit, (To) ・・Reference voltage generator, (To)・・Comparator, etc.) ... Monostable multivibrator,...
・Delay time adjuster, (2)...Delay circuit, (2)...
Strobe drive circuit, (c)...discharge tube, Q's...crankshaft, blade...reference TDC mark, (to)...specific cylinder n TDC mark, 6])...irradiation light, )
...signal processing circuit,) ...stroboscope, (
To)...Standard value, (To)...Comparator, (B)
...Diagnosis result display, (to) rank angle information agent Hiroaki Moriki - vcuv, o1p4t, <t-it

Claims (1)

[Claims] 1. Vibration or sound detection sensor 7 installed on the outside of the fuel injection valve of the device to be diagnosed, extracts a signal corresponding to the fuel injection timing from the output signal of this sensor, and uses this extracted signal as a reference to perform a comparator with a bell. A signal processing circuit that detects the fuel injection timing at a certain rate and outputs this detection signal after delaying it by an arbitrary amount of time, a stroboscope that uses the output signal of this signal processing circuit as a trigger signal, and a signal processing circuit that A comparator is provided which inputs the signal corresponding to the arbitrary time and a known standard value determined by the model of the device to be diagnosed and detects a match between the two, and uses the output signal of this comparator as a signal for determining the quality of the device to be diagnosed. Combustion diagnostic device for Toshi-9 diesel engine.