JPH0219301B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a failure diagnosis device for a fuel injection pump of a diesel engine. A diesel engine fuel injection pump (hereinafter abbreviated as injection pump) has the function of increasing the pressure of fuel oil and delivering the required amount at a set time. To perform this function, an injection pump mainly consists of a camshaft that rotates, a tapepet that reciprocates, a plunger that rotates and reciprocates, gears and control racks that control the amount of oil discharged, a plunger seat, a spring, and a spring seat. It consists of parts such as , bearings, and delivery valves. These components undergo mechanical deterioration such as wear and breakage over time. If the parts deteriorate, the engine's fuel system may malfunction, resulting in poor engine startability, knocking, insufficient output, unstable output, or the maximum rotational speed cannot be achieved or is too high.
Phenomena such as unstable idling speed and abnormal exhaust color appear. In the case of an engine with multiple cylinders, there are parts such as tappets, plungers, springs, etc. for each cylinder, so even if mechanical deterioration occurs in one cylinder, the engine as a whole will operate (move) almost normally. There is. If the overall function of the engine deteriorates (the rated output cannot be obtained), which system is causing the problem?
It was also necessary to investigate which part of the system was causing the problem, and to what extent which parts of that part were contributing to the decline in function. Traditionally, this injection pump function test has been conducted based on the experience of service personnel to check the startability of the diesel engine,
This is done by determining the level of output, idling condition, diesel engine knocking noise, etc.
However, according to this judgment based on experience, each judgment factor includes malfunction phenomena from sources other than the injection pump, so it is difficult to judge the injection pump net.
Due to the experience of service personnel, subjectivity is included, leading to errors, and the number of cylinders (4 cylinders, 6 cylinders)
(cylinders, etc.), the injection pump has multiple pump parts, and it is difficult to determine which pump has degraded in function. There is a drawback that it is not possible to quantitatively determine whether or not it has decreased. Additionally, in order to accurately determine the degree of functional decline, it is necessary to temporarily remove the injection pump from the engine body and examine it using a bench test device, which also has the disadvantage of requiring a long period of time for inspection. SUMMARY OF THE INVENTION In view of the above-mentioned points, an object of the present invention is to provide a device that can quantitatively and easily determine the degree of functional decline of an injection pump. To achieve this objective, the device of the present invention detects vibrations as electrical signals by gluing and fixing an accelerometer to the case of the injection pump, and from the electrical signals generates individual electrical signals corresponding to the vibrations generated by each component. and a reference electrical signal that is not affected by changes in the injection pump over time, respectively, are extracted by a transducer,
A representative voltage value is determined from each of these electrical signals, a ratio between the representative voltage value of each individual electrical signal and a representative electrical value of the reference electrical signal is determined by a calculation device, and the ratio is displayed on a display device. This is what I did. The details of the present invention will be explained below with reference to embodiments shown in the drawings. In FIG. 1, 1 is an injection pump, and 2 is a failure diagnosis device. The device 2 diagnoses failures by quantitatively evaluating the degree of mechanical deterioration of components of the injection pump. In other words, when the injection pump is operating, the camshaft rotates and the tappet and plunger reciprocate, and these parts hit and slide, generating waves (sound, vibration, etc.) associated with the operation. , the wave changes when mechanical deterioration of the internal parts of the injection pump occurs. Therefore, the present invention displays the degree of deterioration by detecting the degree of change in the wave, and since the frequency of the wave differs depending on each part, the wave of the frequency corresponding to each part is This allows the degree of deterioration of each component to be evaluated. The failure diagnosis device 2 includes an accelerometer 3 that is adhesively fixed to the case of the injection pump 1 with instant adhesive or the like.
and a main body 5 connected to the accelerometer 3 via a signal line 4. Accelerometer 3 is injection pump 1
It is a shear type accelerometer that converts vibrations during operation into electrical signals, and the frequency range is several Hz.
to 20KHz, sensitivity is 20 to 40mV/G (2.0 to 4.0m
A material having linearity in V/mS ² ) was used. In the main unit 5, 6 is an amplifier that amplifies the detected voltage signal of the accelerometer 3 to a level suitable for processing in the signal processing unit described below since it is a minute voltage, and has a gain of about 20 to 40 dB. was used. 7a to 7d are wave generators that extract signals in a specific range of frequencies corresponding to components from the output signal of the amplifier 6, and 7h is a wave generator that extracts signals in a specific range of frequencies corresponding to components from the output signal of the amplifier 6. Signal in a frequency band that does not change (This signal is not affected by the natural vibration component of the injection pump, and exhibits a characteristic that the amount of change in signal potential changes little over time during the operation of the injection pump. This signal is described below. This is a bandpass wave generator that extracts a reference electrical signal (referred to as a reference electrical signal A). The signals extracted by each of the wave generators 7a to 7d correspond to vibrations generated from components as shown in the table below.

[Table] Each of the signals B to E listed in the above table will be explained below. Signal B is generated due to a phenomenon in which the cam part of the camshaft and the roller part of the tappet collide with each other due to the gap between them.The vibration becomes large due to rattling, indentation, wear, and seizure, and the frequency exceeds the set frequency for signal extraction. A high-pass wave filter is used to pass the signal. ” Signal C is generated by a signal accompanying the revolution and rotation of the bearing part of the camshaft, and vibration increases due to deterioration phenomena such as mechanical deterioration, wear, electrolytic corrosion, seizure, flaking, cracking, and compression. For signal extraction, a low-pass transducer is used that allows signals below a certain set frequency to pass through the outer ring, rolling elements, and inner ring. Regarding signal D, the tappet, plunger seat, and plunger are pushed in one direction by a push spring, and the plunger seat may suffer mechanical deterioration, dents, or cracks, and the tappet may suffer from mechanical deterioration, dents, or cracks. Phenomena such as abrasion, dents, and cracks occur in the spring, and the free length of the push spring changes. In addition, the push spring itself also causes changes in the eyelids, such as becoming sagging or breaking. The tappet, plunger seat, and plunger are pressed by a push spring, and when the injection pump operates, each part knocks against each other, causing deterioration phenomena such as changes in the free length of the spring, dents, and cracks. The vibration increases, and a bandpass filter 7c that passes a certain set frequency band is used to extract the signal. The signal E generated by the delivery valve increases due to deterioration phenomena such as damage to the piston, seizure, and change in the free length of the push spring, and a bandpass wave generator 3d is used to extract this signal. The delivery valve, tappet, plunger seat, and wave device used to detect the vibration of the plunger are band wave devices and have the same type, but their masses and dimensions (sizes) are different, and their natural frequencies are different. This can be determined by changing the frequency band. 8 is a wave device 7 as shown in FIGS. 2 to 5.
This is a signal shaper that obtains gentle rectified signal envelope signals as shown in FIGS. 6 to 8 from the output signals of a to 7h, respectively, and it is determined by the control device 11 which waveform generator's output is to be shaped. selected. This input circuit also includes a circuit 15 into which the output signal of the amplifier 6 is directly input. This circuit 15
is used to pass the original signal when observing waveforms using a display or the like as described later. Reference numeral 9 denotes a signal converter that converts the peak voltage of the voltage that is the output signal of the signal shaper 8 into a digital value. Reference numeral 10 denotes an arithmetic unit that determines a representative value by sampling the digitized peak voltage and calculates the ratio between the representative value of the reference electrical signal and the representative value of the individual electrical signal. Reference numeral 12 denotes a reproducible recording device such as a magnetic soot body or paper tape for recording the calculation results of the calculation device 10. Reference numeral 13 has a function of displaying the calculation results numerically or writing them on recording paper, and, if necessary, a function of displaying the functional limit with a lamp or generating an alarm sound. 14 is a battery provided as a power source for the failure diagnosis device. Next, the operation of this device will be described for the case where vibrations of the camshaft and tappet, indicated by signal name B, are detected. In normal operation, the electrical signals obtained from the accelerometer 3 and amplifier 6 are as shown in Figure 2, and the impact vibrations caused by the camshaft and tappet hitting each other appear in the form of primary damping. . On the other hand, if deterioration phenomena such as rattling, dents, and wear occur,
The result is a random waveform as shown in FIG. The reference electric signal A, which is not affected by the aging of the injection pump, has a waveform as shown in FIG. The signals B and A are extracted by waveformers 7a and 7h, respectively, and input to a signal shaper 8. The signal shaper 8 smoothes and rectifies the output signals of the waveforms 7a, 7b, . . . , 7h in this order to obtain signals as shown in FIGS. The signal converter 9 has a peak voltage as shown in FIG.
B ₁ , B ₂ …B _o (or the peak voltage shown in Figure 6)
B ₁ ′, B ₂ ′…B _o ′) and the peak voltage shown in Figure 7.
A ₁ , A ₂ . . . A _o are converted into digital values and input to the arithmetic unit 10. The control device 11 controls the signal shaper 8, the signal converter 9, and the arithmetic device 10 so that their operations and signal exchange can be performed synchronously for each signal. The arithmetic device processes the peak voltage value as follows. 1 Temporarily store n peak voltage samples in the signal converter 9. 2 Find the frequency distribution of voltage-number of samples from the stored peak voltage. FIGS. 8 to 10 show examples of frequency distributions of the peak voltages shown in FIGS. 5 to 7, respectively. 3 Find the representative voltages of the A and B signals from the frequency distribution. As for the representative voltages, the voltages with the maximum number of samples of the frequency distribution are the representative voltages Ag and Bg. Further, when the maximum voltage of the frequency distribution is 100%, the voltage corresponding to 95% is defined as the representative voltages Ah and Bh. Bg is the effective value component of the voltage, and Bh is the peak value component of the voltage. For example, in the case of a voltage that changes sinusoidally between +1.414 and -1.414, Bg is 1.0V and Bh is
It becomes 1.414×0.95V. 4 Perform the following calculation from the representative voltage. Voltage ratio Rg=Bg/Ag・C Voltage ratio Rh=Bh/Ah・C However, C represents a proportionality coefficient for reducing the influence of an invalid signal (noise) from among the voltage signals. 5. Determine the degree of deterioration of the B signal for which diagnosis was performed from the correlation diagram (Fig. 11) between Rg, Rh, and mechanical deterioration determined in advance. Then, depending on the mechanical deterioration content, the voltage ratio
Distinguish between Rg or Rh. In the case of rattling, denting, abrasion, settling, or bending, judge based on the voltage ratio Rg and check for seizure,
In case of damage, judgment is made based on the voltage ratio Rh. The reason why Rg and Rh are determined based on Bg and Bh is as follows. The oscillating voltage generated when the injection pump is operating,
When signs of failure begin to appear, Bg changes (increases) depending on the nature of the failure, only Bh changes, or both change. When the performance deteriorates during the normal aging process (that is, the injection pump deteriorates due to the rattling, compression, etc.), Bg increases first. In addition, if an abnormality occurs in some of the internal parts of the injection pump (sudden symptoms such as seizure, etc.),
Bh increases rapidly. Therefore, both Bg and Bh are obtained to check whether the limit voltage ratios RgS and RhS are reached or not. 6. The result of the quantitative deterioration degree of the B signal subjected to the diagnosis is outputted to the display device 12 as a signal. Further, a signal is also output to the display device when the result of the diagnosis corresponds to the limit voltage ratios RgS and RhS at which mechanical deterioration progresses and the function is about to be lost. The same method is applied to the C, D, and E signals in the table above to quantitatively evaluate deterioration and functional limits, and perform failure diagnosis. A display device 12 receives the output of the arithmetic device 10 and displays the diagnosis result numerically or on a recording paper, and in the case of a functional limit, displays such as lighting a lamp or generating an alarm sound. Further, the calculation results by the calculation device 10 are stored in a recording device 13 having a reproducible storage function, such as a magnetic medium or paper tape. Next, in the case of an engine with multiple cylinders, there are as many injection pump parts as there are, and which pump part is determined can be determined by the position where the accelerometer is installed. That is, by installing an accelerometer closest to the pump part to be diagnosed, diagnosis can be made because the vibration transfer function and mechanical impedance are different. As described above, according to the present invention, the degree of deterioration of each part of the injection pump can be quantitatively known as the voltage ratio, and even a person without experience can easily and quickly determine a failure. can do.
Also, if the injection pump has multiple pump parts,
By providing multiple accelerometers, it is possible to easily determine which pump is malfunctioning.
Further, if the failure diagnosis device of the present invention is constantly used (if it is a vehicle system, it is mounted on the vehicle), it is useful for preventive maintenance against failures and losses can be minimized.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the failure diagnosis device according to the present invention, FIGS. 2 to 7 are waveform diagrams showing examples of waveforms in the signal processing process of the embodiment, and FIGS. 8 to 11. FIG. 2 is a diagram illustrating the signal processing contents of the arithmetic device of the embodiment. 1... Injection pump, 3... Accelerometer, 7a-7
h...Wave device, 10...Arithmetic device, 12...Display device.

Claims (1)

[Claims] 1. A device for diagnosing failures by inspecting the function of a fuel injection pump in a diesel engine, which includes an accelerometer that is adhesively fixed to the case of the fuel injection pump to detect vibrations, and an electrical signal obtained from the accelerometer to detect fuel injection. a plurality of wave transducers each extracting individual electrical signals corresponding to vibrations generated by each component of the pump; and a wave transducer extracting a reference electrical signal unaffected by aging of the fuel injection pump from the electrical signals. , an arithmetic device that samples the output signal of each of these wave generators to determine a representative voltage value, and calculates a ratio between the representative voltage value of the individual electrical signal and the representative voltage value of the reference electrical signal; A failure diagnosis device for a fuel injection pump, comprising a display device that displays results.