JPH0313837A - Fault diagnosis method for exhaust valve - Google Patents

Abstract

PURPOSE:To perform fault diagnosis objectively and highly accurately by detecting vibration when an exhaust valve comes into contact with a valve seat, detecting a crank angle when the exhaust valve comes into contact, analyzing the vibrating frequency at this time, comparing the frequency with the analyzed value of the vibration frequency obtained at the normal time beforehand, and judging the presence or absence of the fault of the exhaust valve. CONSTITUTION:Vibration when an exhaust valve 104 comes into contact with an exhaust valve seat 105 is picked up by a vibration sensor at good timing, and the frequency is analyzed. The rate of the high frequency spectrum occupied in the entire spectrums is computed. Whether the valve is normal or abnormal is judged based on the magnitude of the value. Since the high frequency vibration tends to attenuate quickly, a powerful magnet 111 is mounted in the sensor 110 so that the searching point for the vibration source can be freely changed. A rotary-angle detecting sensor 119 is used for detecting the seating timing of the exhaust valve 104. The movement of a pin 118 which is provided at a flywheel 108 and the like is detected, and a crank angle is computed. In this way, the fault diagnosis of the exhaust valve 104 can be performed objectively and highly accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to fault diagnosis of exhaust valves of diesel engines.

[Conventional technology]

FIG. 3 shows an example of a conventional exhaust valve failure diagnosis device for a diesel engine.

01 is a diesel engine, 02 is a cylinder, 03 is an indicator cock, 04 is a pressure pickup attached to the indicator cock of cylinder height 1, 04' is a pressure pickup attached to the indicator cock of cylinder class 2, 06 is an oscilloscope, 05 and 05' are the cords connecting the pressure start-up 04.04' to the oscilloscope 06.

FIG. 4 shows an acupressure chart recorded on the oscilloscope 06, in which the solid line is a normal acupressure chart, and the dotted line is an example of an abnormal acupressure chart.

If the performance values of the diesel engine show an abnormality, for example if the exhaust temperature rises or the fuel efficiency worsens, collect a shiatsu chart and compare it with the standard value. If the overall value is low, there is an abnormality in the exhaust valve. Diagnose. As a method of comparison, two strain gauge type pressure pickups 04 and 04' are connected to the indicator cock 0 on a 2-channel oscilloscope 06.
3, and the images displayed on the oscilloscope 06 are superimposed on each other.

Now, the acupressure diagram of cylinder &2 is in y agreement with the acupressure diagram of other cylinders except for cylinder 1, and it is diagnosed as a standard value, and it becomes like the solid line in Figure 4, and on top of that, the acupressure diagram of cylinder 1 is When the shiatsu diagrams are superimposed, if they match, it is diagnosed that there is no abnormality in the exhaust valve of the first cylinder.If the exhaust valve fails, the gas in the cylinder will leak toward the exhaust pipe even when the valve is closed, so the dotted line indicates Since the value is lower than normal, it is diagnosed that there is an abnormality.

[Problem to be solved by the invention]

The prior art as described above has the following bottle problems.

(1) Since the two images are visually inspected, subjectivity is involved in the judgment, and since the images are small, judgment cannot be made unless there is a fairly large difference.

(2) Since the strength pickup has a temperature bias, the accuracy of the pressure in the low part, which is important for judgment, is poor.

(3) Due to the poor accuracy due to the reasons stated in (1) and (21) above, it cannot be determined unless there is a fairly major failure.

An object of the present invention is to provide a method for objectively and highly accurately diagnosing exhaust valve failures.

[Means to solve the problem]

When the exhaust valve is seated on the exhaust valve seat, vibrations are generated.

Experiments have revealed that if the exhaust valve is damaged, such as by cracks, vibrations will be diffusely reflected at that part, producing high-frequency imaging (approximately IQKHz or higher).

Therefore, we collect the vibrations with an acceleration sensor or a vibration sensor at the right time, perform frequency analysis, calculate the proportion of high-frequency vectors in the total vector, and judge whether it is normal or abnormal based on the level of the value. do.

Furthermore, since high-frequency vibrations are easily attenuated, the sensor is equipped with a strong magnet so that the detection point of the vibration source can be changed freely.

In order to detect the seating timing of the exhaust valve, a rotation angle detection sensor is used to calculate the crank angle by detecting the movement of a pin or mark provided on a flywheel or the like.

[Effect]

If we detect the vibration when the exhaust valve sits on the valve seat and analyze it with a frequency analyzer, we will find that if the exhaust valve has cracks or other damage, there will be a lot of vibration with high frequency components.
It is possible to determine whether or not the exhaust valve is malfunctioning.

By detecting the crank angle, a comparison is made with normal vibration.

〔Example〕

FIG. 1 shows an embodiment of the invention.

02 is a cylinder, 101 is a piston, 102 is a combustion chamber,
103 is a fuel valve, 104 is an exhaust valve, 105 is an exhaust valve 10
4 is the valve seat, 106 is the cylinder outlet, 107 is the exhaust valve 10
4 is the valve box, 108 is the flywheel attached to the engine shaft, 1
10 is a vibration sensor (acceleration sensor) attached to the wall of the valve box 107, 111 is a magnet for fixing the imaging sensor 110, 112 is a charge amplifier, and 113 is a high-speed A-D.
Converter, 114 is a CPU (central processing unit), 115 is an auxiliary storage device, 116 is a display device, 117 is an input device,
118 is a pin or mark provided on the flywheel 108;
119 is a rotation angle detection sensor, and 120 is an amplifier for the rotation angle detection sensor 119.

Fuel is injected from the fuel valve 103 into the combustion chamber 102 to cause combustion, and when that is finished, the exhaust valve 104 opens and the combustion chamber 10
When the combustion gas of No. 2 is exhausted and fresh air is sucked in by the action of the piston 101, the exhaust valve 104 is closed. that time,
The exhaust valve 104 hits the valve seat 105 to generate vibration.

If the exhaust valve 104 is damaged or cracked,
The vibrations are diffusely reflected at that part, creating new complex vibrations.
In particular, it generates high-frequency vibrations.

Therefore, the vibrations of the exhaust valve 104 are collected by a vibration detector 110, amplified by a charge amplifier 112, and then transferred to the A-D converter 1.
Send to 13th.

The AD converter 113 converts the vibration analog data into digital data at a sampling rate Δ every second, and sends the data to the CPU (Central Processing Unit) 114 .

On the other hand, if a pin 118 is provided on the flywheel 108 to detect the time when the exhaust valve 104 is seated, and the crank angle at which the rotation angle detection sensor 119 generates a signal is checked in advance, it is possible to detect the time when the exhaust valve 104 is seated. Since the crank angle is known, vibration data when the valve is seated can be obtained.

A CPU (Central Processing Unit) 114 performs frequency analysis on the vibration data when the exhaust valve 104 is seated, and compares it with the frequency analysis value of normal vibration data saved in the auxiliary storage device 115. An example is shown in FIG.

If the output of the high frequency part is higher (Figure 2 (b)) compared to the normal case (Figure 2 (a)), it is determined to be abnormal, and if there is little change, it is determined to be normal. The results are then displayed on the display device 116.

Since the exhaust valve 104 is damaged and cracked over a wide area and has large vibration damping, a strong magnet 111 is installed at the tip of the vibration sensor 110 so that the surroundings of the exhaust valve box 107 can be freely explored.

〔Effect of the invention〕

The exhaust valve failure diagnosis method according to the present invention detects the vibration when the exhaust valve seats on the valve seat, detects the crank angle at which the exhaust valve seats, and analyzes the vibration with a frequency analyzer to determine whether the exhaust valve is normal or not. By comparing the frequency analysis value of the vibration obtained during the inspection, we can determine whether or not there is a failure in the exhaust valve.
It produces the following effects.

(1) Fault diagnosis can be performed objectively and quickly.

(2) Even if the damage to the exhaust valve is small, it can be detected and it can be detected before a serious accident occurs, which has a large economic effect.

(3) Since the detection position of the vibration sensor can be easily changed, damage or cracks in a wide range of exhaust valves can be detected.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention, and FIG. 2 is a frequency analysis diagram according to the embodiment of the present invention, in which (a) shows a normal case and (b) shows an abnormal case. FIG. 3 is a block diagram of a conventional device, and FIG. 4 is a graph explaining the principle of the conventional device. 104...Exhaust valve 107...Exhaust valve box 1
10... Vibration sensor 111... Magnet 1
13...A-D converter 114...Central processing unit 115...Auxiliary storage device 116...Display device 117...Input device 119...Rotation angle detection sensor bar 2 flash M''XtK (KH2) 11'j-A・D branch outside 11'/- once @, corner skin first time tnsa

Claims (1)

[Claims] Detects the vibration when the exhaust valve seats on the valve seat, detects the crank angle at which the exhaust valve seats, analyzes the vibration with a frequency analyzer, and compares it with the frequency analysis value of vibration obtained in advance under normal conditions. A method for diagnosing an exhaust valve failure, characterized by determining whether or not the exhaust valve is malfunctioning.