JPS63195307A - Fault diagnostic device for exhaust valve of diesel engine - Google Patents

Abstract

PURPOSE:To perform fault diagnostic quickly and exactly by detecting the time when pressure in a cylinder has lowered in a comparison with fixed air pressure, and performing fault diagnostic by making a comparison between turning on times. CONSTITUTION:A pressure balance type pickup 10 is fixed to a left end one 3a of indicator cocks 3a-3f, and turns off an electric circuit when pressure in cylinders 2a-2f has lowered in comparison with fixed air pressure. A detecting device 14 detects a turning off signal issued from the pickup 10, and then fault diagnostic is performed by comparing turning on time for a normal exhaust valve in a memory 18 with the turning on time calculated on a signal issued from the detecting device 14. The fault diagnostic can thereby be performed quickly and exactly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an apparatus 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 cocks, and 4a is NQ1.
The pressure pickup attached to the indicator cock 3a of the cylinder 2a, 4b is the pressure pickup attached to the indicator cock 3b of the cylinder 2b, 6 is an oscilloscope, and 5a and 5b are the pickup 4a.
and 4b to the oscilloscope 6, respectively.

Figure 6 is an acupressure chart recorded on the oscilloscope 6.
The solid line in the figure is an example of a normal acupressure chart, and the broken line is an example of an abnormal acupressure chart.

If the performance values of diesel engine 1 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, and if the overall value is low, there is an abnormality in the exhaust valve. Diagnose as yes. As a method of comparison, use the indicator cock 3a.

This is done by connecting the strain gauge type pressure pickups 4a and ib attached to the oscilloscope 3b to a two-channel oscilloscope 6, and superimposing the images displayed on the oscilloscope 6.

That is, if the acupressure diagram of the Na2 cylinder 2b is almost the same as the acupressure diagrams of the other cylinders 2c to 2f except the first cylinder 2a, then the acupressure diagram of the second cylinder 2b is diagnosed as the standard value, and this is the It will look like the solid line in Figure 6. When the acupressure diagram of the first cylinder 2a is superimposed on this acupressure diagram and they match, it is diagnosed that the exhaust valve of the first cylinder 2a is normal. If the exhaust valve of Kou 1 cylinder 2a is malfunctioning, 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 will be lower than it would normally be, so in that case it is abnormal. Diagnose as yes.

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

Due to these reasons, the accuracy is low, and there has been a problem in that it is difficult to determine unless the failure is a very large one.

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 the present invention, a computer is used as a means for making a judgment, and a pressure balanced type pickup is used which has high accuracy even at low pressure. A low back pressure is applied to the exhaust valve, and a computer compares and determines the length of the ON-OFF electric signal obtained from the back pressure, thereby diagnosing the failure of 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 energization in the pressure balanced pickup will be reduced. (ON) time is shorter in abnormal cases than in normal cases. Pre-memorize the normal (ON) time in the computer, and set the time to be diagnosed.
The (ON) time can be calculated and compared with the normal case, and if they match, it can be diagnosed as normal, and if it is shorter, it can be diagnosed as abnormal.

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

In FIG. 1, 1 is a diesel engine, 2a to 2f are cylinders, 38 to 3f (3a is omitted) are indicator cocks provided in each cylinder, 10 is a pressure balanced pickup attached to the indicator cock 3a, and 11
1 is a pressure reducing valve; 12 is an air conduit connecting the pressure balanced pickup 10 and the pressure reducing valve 11; 13 is an air source;
4 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, 1
9 is an output device. The pressure balanced pickup 10 is
Its structure is shown in FIG. 2, in which reference numeral 20 denotes an air inlet that takes in air passing through the conduit 12;
21 is a gas inlet for introducing gas into the cylinder 2a by opening the indicator cock 3a; 22 is an air reservoir;
23 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 in the center. an upper presser foot in which the terminal 25 surrounded by 28 is embedded and a large number of small holes 29 are formed therethrough;
Reference numeral 30 denotes a lower presser foot made of a circular metal plate having a recess of about 0.5N in depth on the upper surface and passing through a large number of small holes 31.

The diaphragm 24 is held between the upper and lower presser feet 27 and 30. The pressure balanced type big up 20 has an insulator 26
．． All of them except for 28 are made of metal, a constant voltage is applied to the terminal 25, and the outer periphery is electrically grounded 32.

Air that has been reduced to a constant pressure from the air source 13 by the pressure reducing valve 11 passes through the air conduit 12 to the pressure balanced pickup 2.
When the air reaches the air reservoir 22 through the air inlet 20 of 0, the diaphragm 24
acts on the top surface of If no gas pressure is applied to the gas reservoir 23, the air pressure will cause the diaphragm 24 to move against the lower presser foot 30.
The terminal 25 and the diaphragm 24 are completely separated from each other, so that the diaphragm 24 and the terminal 25 are electrically turned off.

If gas pressure is applied to the gas reservoir 23 and becomes higher than the air pressure in the air reservoir 22, the diaphragm 24
0 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.

The pressure balanced pickup 10 is connected to the indicator cock 3a.
If the pressure reducing valve 11 is operated to apply back pressure P to the air reservoir 22, which is slightly higher than the cylinder internal pressure when the exhaust valve is opened, the diaphragm 24 and Contact and separation are made between the terminals 25.

If the exhaust valve is normal, it will be (a) and (b), and if it is abnormal, it will be (a') and (gu'). When the exhaust valve is abnormal, the shiatsu figure is lower than when it is normal, so the time (or crank angle) from (a') to (mouth') T is the time from (a) to (b) (or crank angle) becomes shorter than To.

Therefore, the time (or crank angle) To from immediately after ON to immediately before OFF of the electric signal of the pressure balance pickup 10 when the exhaust valve is normal is stored in the computer 16 in advance, and the pressure balance pickup 10 of the cylinder 2a to be diagnosed is stored in advance. OFF immediately after ON of the electrical signal collected from
By comparing the time (or crank angle) T□ just before F, it can be determined whether the exhaust valve is normal or abnormal.

That is, a flowchart of software for obtaining this is shown in FIG. Enter the data file name such as rotation speed, output, back pressure value, normal value, etc. from the input operation panel 17 of the computer 16 and turn on the pressure balanced pickup 10.
) The time T is calculated, and the normal fit (ON) time To under the same operating conditions is read from the storage device 18 and compared.

If the comparison result is T≧To, it is determined to be normal, and T<T
In the case of o, it is determined that there is an abnormality, and this information is displayed on the output device 19.

〔Effect of the invention〕

As explained above, according to the present invention, since the judgment is made by a computer, the subjectivity of the person inspecting is not included, and the judgment can be made accurately and quickly.In addition, since the pressure-balanced pickup is used, which is highly accurate even at low pressures, the accuracy is improved. good. Moreover, the pressure balanced type pickup has a low pressure judgment (5 to 9f/
CD (inside and outside), which has the advantage that the pressure source pressure to be compared is also small and can be easily obtained.

[Brief explanation of the drawing]

1 to 4 show one embodiment of the present invention, FIG. 1 is a configuration diagram, FIG. 2 is a sectional view explaining the structure of a pressure balanced pickup, and FIG. 3 is a diagram obtained from a pressure balanced pickup. 4 is a flowchart illustrating the processing procedure of a combination machine, FIG. 5 is a conventional configuration diagram, and FIG. 6 is a characteristic diagram illustrating conventional diagnosis. 14...Electricity detection device, 16...Computer, 1
8...Storage device, 19...Output device #4゜Applicant's agent Patent attorney Takehiko Suzue Figure 12, Figure 4

Claims (1)

[Scope of Claim] A device for diagnosing failure of exhaust valves of diesel engines based on cylinder pressure, comprising: a pressure balanced pickup that opens or closes an electric circuit when cylinder pressure decreases with respect to a set air pressure; A device that detects the opening/closing signal of the electric circuit from the pressure balanced pickup, a storage 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 and stores the energizing time in the above memory. A device for diagnosing exhaust valve failure in a diesel engine, comprising: a computer for comparing the time with normal energization time from the device; and an output device for displaying the results.