JPH0476002B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for diagnosing a failure in an exhaust valve of a diesel engine based on the pressure inside the cylinder.

[Prior Art] Conventionally, a device shown in FIG. 5 has been employed as a means for diagnosing a failure in an exhaust valve of a diesel engine. That is, in Fig. 5, 1 is a diesel engine, 2a to 2f are cylinders, 3a to 3f are indicator sockets, 4a is a pressure pick-up attached to the indicator socket 3a of No. 1 cylinder 2a, and 4b is an indicator of No. 2 cylinder 2b. A pressure pickup is attached to the pickup 3b, 6 is an oscilloscope, and 5a and 5b are electric wires connecting the pickups 4a and 4b to the oscilloscope 6, respectively.

FIG. 6 shows an acupressure chart recorded on the oscilloscope 6, in which the solid line is an example of a normal acupressure chart, and the broken line is an example of an abnormal acupressure chart.

If the performance value of diesel engine 1 shows 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 performance value is low, there is an abnormality in the exhaust valve. Diagnose as yes. As a method of comparison, Indicator Kotoku 3
This is done by connecting the strain gauge type pressure pickups 4a and 4b attached to the oscilloscopes 4a and 3b to a two-channel oscilloscope 6, and superimposing the images displayed on the oscilloscope 6.

In other words, the shiatsu diagram for No. 2 cylinder 2b is now No.
If the acupressure diagrams of the other cylinders 2c to 2f except for the No. 1 cylinder 2a are substantially the same, the acupressure diagram of the No. 2 cylinder 2b is diagnosed as a standard value, and this is as shown by the solid line in FIG. 6. When the acupressure diagram of the No. 1 cylinder 2a is superimposed on this acupressure diagram and they match, it is diagnosed that there is no abnormality in the exhaust valve of the No. 1 cylinder 2a. If the exhaust valve of No. 1 cylinder 2a malfunctions, the gas inside the cylinder will leak toward the exhaust pipe even when the valve is closed, so the shiatsu chart will look like a broken line, and the pressure will be lower than in a normal case. Diagnose as abnormal.

[Problems to be Solved by the Invention] However, with the above-mentioned conventional device, since the two images are compared visually, judgment is subject to subjectivity, and since the images are small, judgment cannot be made unless there is a fairly large difference. Due to temperature drift in strain gauge type pickups, accuracy is poor in low pressure areas, which is an important factor in determination.

Due to these reasons, the accuracy was low, and there was a problem that could not be determined unless it was a very large failure.

The present invention aims to eliminate subjective judgment and provide a highly accurate exhaust valve failure diagnosis device for a diesel engine.

[Means for Solving the Problems] In order to achieve the above object, the present invention is a device for diagnosing a failure of an exhaust valve of a diesel engine from the cylinder internal pressure, and the present invention is a device for diagnosing a failure in the exhaust valve of a diesel engine based on the cylinder internal pressure. a pressure-balanced pickup that opens or closes an electric circuit when the pressure drops; a signal that detects the opening/closing signal of the electric circuit from the pressure-balanced pickup; a memory device that stores the energization time in the case of a normal exhaust valve; It is characterized by comprising a computer that calculates the energization time based on the signal from the opening/closing signal detection device and compares it with the normal energization time from the storage device, and an output device that displays the result.

That is, in the present invention, a computer is used as a means for making a judgment, and a pressure-balanced pickup is used, which is highly accurate even at low pressures, and a low back pressure of, for example, 5 kgf/cm ² is applied to the pressure-balanced pickup. A computer is used to compare and judge the length of the ON-OFF electric signals obtained from this, thereby diagnosing a malfunction in the exhaust valve.

[Operation] According to the present invention, if there is an abnormality in the exhaust valve, gas will leak from the cylinder to the exhaust pipe even when the valve is closed, so the shiatsu figure will be lower than in a normal case, and therefore the pressure balance type pickup The energization (ON) time is shorter in abnormal cases than in normal cases. The computer stores in advance the energization (ON) time when it is normal, calculates the energization (O) time of the object to be diagnosed, and compares it with the normal case. If it matches, it is diagnosed as normal, and if it is shorter, it is diagnosed as abnormal. can do.

[Example] The present invention will be described below based on an example shown in FIGS. 1 to 4.

In Figure 1, 1 is a diesel engine, 2a~
2f is a cylinder, 3a to 3f (3a is omitted) is an indicator socket provided on each cylinder, 10 is a pressure balanced type pickup attached to the indicator socket 3a, 11 is a pressure reducing valve, and 12 is the pressure balanced type pickup 10. and the pressure reducing valve 11
13 is an air source; 14 is an energization detection device; 15 is an electric wire connecting the pressure balanced pickup 10 and the energization detection device 14;
16 is a computer, 17 is an input operation panel, 18 is a storage device, and 19 is an output device. The structure of the pressure-balanced pickup 10 is shown in FIG. 2, in which 20 is an air inlet that takes in the air passing through the conduit 12, and 21 is an air inlet that takes in the air that has passed through the conduit 12, and 21 is a cylinder 2a that can be opened by opening the indicator cock 3a.
a gas inlet for introducing gas into the interior; 22 is an air reservoir; 2
3 is a gas reservoir; 24 is a metal diaphragm; 25 is a rod-shaped terminal whose upper end is connected to the electric wire 15 and whose outer periphery is surrounded by an electrical insulator 26; and 27 is a circular metal plate with an insulator 28 in the center. The upper presser foot 30 is made of a circular metal plate in which the terminal 25 surrounded by the terminal 25 is embedded and a large number of small holes 29 are formed through the plate, and the upper surface is provided with a recess of about 0.5 mm in depth and has a large number of small holes 31... This is the lower presser foot that passes through. The diaphragm 24 is held between the upper and lower presser feet 27 and 30. The pressure-balanced pickup 10 is made entirely of metal except for insulators 26 and 28, a constant voltage is applied to the terminal 25, and the outer periphery is electrically grounded 32.

When the air from the air source 13 that has been reduced to a constant pressure by the pressure reducing valve 11 passes through the air conduit 12, passes through the air inlet 20 of the pressure-balanced pickup 10, and reaches the air reservoir 22, it passes through the small hole 29 of the upper presser foot 27. It acts on the upper surface of the diaphragm 24 through... If no gas pressure is applied to the gas reservoir 23, the air pressure presses the diaphragm 24 against the recess of the lower presser foot 30, and the terminal 25 and diaphragm 24 are completely separated, so that there is no electrical connection between the diaphragm 24 and the terminal 25. becomes OFF state.

If gas pressure is applied to the gas reservoir 23, the air reservoir 2
When the air pressure becomes higher than 2, the diaphragm 24
is separated from the concave side of the lower presser foot 30 and is pressed against the lower surface of the upper presser foot 27, and at this time the diaphragm 24 and the terminal 25 come into contact and become energized.

The characteristics shown in the upper part of Figure 3 are the cylinder pressure diagrams, where the solid line shows when the exhaust valve is normal and the broken line shows when the exhaust valve is abnormal. Overall it is lower than the case.

The characteristics shown in the center of FIG. 3 are the electrical signals of the pressure-balanced pickup 10 when the exhaust valve is normal, and the characteristics shown in the lower part of FIG. 3 are the electrical signals of the pressure-balanced pickup 10 when the exhaust valve is abnormal. It is.

Assuming that the pressure-balanced pick-up 10 is attached to the indicator stock 3a and the pressure reducing valve 11 is operated to apply a back pressure of P, which is slightly higher than the cylinder internal pressure when the exhaust valve is opened, to the air reservoir 22, the finger pressure diagram and the back pressure are Diaphragm 24 and terminal 25 at the point where the lines cross
Contact and separation occur in between. If the exhaust valve is normal, it will be (a) and (b), and if it is abnormal, it will be (a') and (b'). When the exhaust valve is abnormal, the shiatsu chart is lower than when it is normal, so the time (or crank angle) from (a') to (b') T ₁ is the time from (a) to (b) (or Crank angle) becomes shorter than T ₀ .

Therefore, when the exhaust valve is normal, the electric signal of the pressure balance pick-up 10 turns OFF immediately after it turns ON.
The previous time (or crank angle) T ₀ is stored in advance in the computer 16, and the time (or crank angle) from immediately after ON to immediately before OFF of the electrical signal collected from the pressure balance pickup 10 of the cylinder 2a to be diagnosed is stored in advance in the computer 16. ) T ₁ can be compared to determine whether the exhaust valve is normal or abnormal.

That is, a flowchart of the software for obtaining this is shown in FIG. The data file name of rotation speed, output, back pressure value, normal value, etc. are input from the input operation panel 17 of the computer 16, and the energization (ON) time T of the pressure balanced type pickup 10 is calculated, and the operating conditions are the same. The energization (ON) time T ₀ in the normal case is read from the storage device 18 and compared. If the comparison result is T≧T ₀ , it is determined to be normal, and if T<T ₀ , it is determined to be abnormal, and this information is displayed on the output device 19.

[Effects of the Invention] As explained above, according to the present invention, since the judgment is made by a computer, the subjectivity of the person conducting the inspection is not included, and the judgment can be made accurately and quickly, and a pressure-balanced pick-up with high accuracy even at low pressure can be realized. The accuracy is good because it is used. In addition, the pressure balanced type pickup can perform judgments at low pressures (around 5 Kgf/cm ² ), so it has the advantage that the pressure source pressure for comparison can be small and easily obtained.

[Brief explanation of the drawing]

1 to 4 show an embodiment of the present invention, FIG. 1 is a configuration diagram, FIG. 2 is a cross-sectional view explaining the structure of a pressure-balanced pickup, and FIG. 3 is a diagram illustrating the structure of a pressure-balanced pickup. 4 is a flowchart illustrating a computer processing procedure, FIG. 5 is a conventional configuration diagram, and FIG. 6 is a characteristic diagram illustrating conventional diagnosis. 1... Diesel engine, 2a to 2f... Cylinder, 3a to 3f... Indicator cock, 10...
...Pressure balanced pickup, 11...Pressure reducing valve, 1
4...Electricity detection device, 16...Computer, 1
8...Storage device, 19...Output device.

Claims (1)

[Scope of Claims] 1. In a device for diagnosing failure of exhaust valves of diesel engines based on cylinder pressure, there is provided a pressure-balanced pick-up in which an electric circuit opens or closes when the cylinder pressure decreases with respect to a set air pressure. A device that detects the opening/closing signal of the electric circuit from this pressure balanced pickup, a memory device that stores the energizing time in the case of a normal exhaust valve, and a device that calculates the energizing time based on the signal from the opening/closing signal detection device. , a computer for comparing the energization time with the normal energization time from the storage device, and an output device for displaying the results.