JPS59198340A - Evaluation of cavitation between cylinder liner and piston of internal combustion engine - Google Patents

Abstract

PURPOSE:To enable sharp cost-down by dispensing with a long-time durability test, by mounting a high frequency vibration detector to the wall part of a cylinder block while passing the output signal thereof through a bypass filter to block the low frequency component thereof. CONSTITUTION:A piezoelectric element 10 as a high frequency vibration detector is directly mounted to the outer wall part 4a of a cylinder block and connected to a bypass filter 11 which is, in turn, further connected to an amplifier 12. The bypass filter 11 is constituted so as to pass only a high frequency component among vibrations detected by the piezoelectric element 10. In this case, because vibration with blocking frequency of 250-300kHz or more is used with respect to the bypass filter, only ultrasonic wave of cavitation is enabled to pass and a long-time durability test is dispensed with and cost-down can be achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for evaluating cavitation between a cylinder liner and a piston of an internal combustion engine, and particularly to a method that allows the intensity of cavitation to be directly determined in an actual engine.

Generally, in a liquid-cooled internal combustion engine, a cylinder liner and a piston inside the cylinder liner have a structure as shown in FIG. 1 (longitudinal cross-sectional view). is the cooling water passage, 4 is the cylinder block,
5 indicates a connecting rod.

Piston 1 slides up and down inside cylinder liner 2 together with connecting rod 5, but since there is a slight gap between piston 1 and cylinder liner 2, it also moves horizontally and rotates at the same time, so piston 5 l and cylinder liner 2
A collision occurs between the cylinder liner 2 and the cylinder liner 2, causing it to vibrate. If this vibration is large, cavitation occurs around the cylinder liner 2, cavitation erosion occurs in the cylinder liner 2, etc., which leads to cracks in the cylinder liner 2 and deterioration of engine performance.

Therefore, a simple detection and judgment method for this cavitation phenomenon is desired, but conventionally, the strength of cavitation has been determined and evaluated through durability tests. The extent of the outbreak is being confirmed.

However, the conventional method as described above requires long-term durable operation, resulting in a large amount of cost and a long time required for five rounds.

The present invention aims to solve these problems, and evaluates the cavitation between the cylinder and piston of an actual internal combustion engine without the need for long-term durability tests. The purpose is to provide a method that allows you to do this.

For this reason, the cavitation evaluation method of the present invention.

In an internal combustion engine, in order to evaluate the cavitation that occurs between the cylinder liner inside the cylinder block and the piston inside the cylinder liner, a high-frequency vibration detector is attached to the wall of the cylinder block. The output signal of the detection object is set to a cutoff frequency of 250 to 30
0KH2 or more and damping characteristics 35-40 ab10ct
Pass it through a bypass filter having the above characteristics to cut off its low-frequency components, and compare the output signal that has passed through the bypass filter with the evaluation value for the output signal determined in advance by experiment. , is characterized in that the intensity of the cavitation is determined.

Hereinafter, a method for evaluating cavitation between a cylinder liner and a piston of an internal combustion engine as an embodiment of the present invention will be explained with reference to the drawings. FIG. 2 shows a system for evaluating cavitation between a cylinder liner and a piston. The system diagram, FIG. 3, is a graph showing an experimental example. In FIG. 2, the same reference numerals as in FIG. 1 indicate almost the same parts.

As shown in FIG. 2, in a liquid-cooled internal combustion engine, a cylinder liner 2 is installed inside the cylinder block 4.
A piezoelectric element 1O as a high-frequency vibration detector is directly attached to the outer wall 4a of the cylinder block 4 so that cavitation occurring in the gap 6 between the cylinder liner 2 and the piston 1 therein can be evaluated. . Furthermore, the natural frequency of the piezoelectric element 10 is about IMH2.

The piezoelectric element IO serving as a high-frequency vibration detector is connected to a bypass filter 11, and the bypass filter 11 is in turn connected to an amplifier 12.

The bypass filter 11 is a filter for passing only high frequency components of the vibrations detected by the piezoelectric element 10, and the bypass filter 11 is designed to have a cutoff frequency of 250 to 300 KH2 or higher, and to reduce its attenuation. A material having a characteristic of 35 to 40 db10ct or more is used.

Further, as the amplifier 12, an amplifier whose frequency range is IMH2 or more is used so as to match the frequency characteristics of the piezoelectric element 10 and the bypass filter 11.

Then, a comparison is made between the output signal transmitted via the amplifier 12 and the evaluation value for the above-mentioned output signal, which has been determined in advance through experiments. In addition, the reference numeral 3 in FIG. 2 indicates a cooling water passage, and the reference numeral 5 indicates a connecting rod.

The cavitation evaluation method between the cylinder liner and piston of an internal combustion engine according to the present invention is performed as described above, so that cavitation occurs in the gap 6 between the cylinder liner 2 and the piston 1 during operation of the internal combustion engine. Then, ultrasonic waves are generated by the impact force and transmitted to the cylinder block 4.

This ultrasonic wave is transmitted as an elastic wave within the cylinder block 4, and is further transmitted to the piezoelectric element 10 as a vibration detector. Contains mechanical vibrations caused by

However, since the ultrasonic phenomenon generated from cavitation is impulsive, it has extremely high frequency components, whereas mechanical vibrations (150-200K)
It has a low frequency range called IZ.

Therefore, a piezoelectric element 10 that receives ultrasonic waves and mechanical vibrations
outputs the received signal to the bypass filter 11, and the signal is transmitted to the bypass filter 11 at a frequency of 3 Q 0
Mechanical vibrations below KHz (150 to 200 KHz) are greatly attenuated and removed, and the bypass filter 1
1, only the cavitation ultrasonic waves are allowed to pass through.

The signal passing through the bypass filter 11 is sent to the amplifier 1
After being amplified in Step 2, it is compared with an evaluation value determined from the relationship between cavitation and ultrasonic output through a durability test in advance, and the strength of the cavitation simulator is determined from this.

When the above-mentioned measurement system was applied to an actual internal combustion engine, the broken line in Figure 3 shows that cavitation erosion did not occur during the durability test without using the bypass filter 11. The state was measured and the results were frequency-analyzed, and the output was quite high at frequencies below about 200KH2.In this case, cavitation did not occur, so this output could be caused by mechanical noise. Wow.

In addition, the graph of solid line B is for the case where cavitation erosion occurs at a young age, and the graph of the bypass filter 11
It was measured without using the oscillator, and frequency analysis was performed.

The graph of the dashed-dotted line C is obtained under the same conditions as the graph of the solid line B above, and at a cut-off frequency of 30.
．． 0KHz and the attenuation characteristic is 24db10at +7) using the bypass filter 11. and a bypass filter with an attenuation characteristic of 48 abloc.
This is for the case of Woyo Vs.

According to graph C and graph D above, the damping characteristic is 24
In graph C of abloct, the mechanical noise increases at a frequency of 200KI (the output at Z
The output is at the same level as the cavitation output of 500KH2, and it can be seen that the influence of mechanical noise is considerable. Also, in graph D of damping characteristic 48 abloct, 1
It can be seen that the output at a frequency of 200 KH2 is sufficiently small, and the influence of mechanical noise is reduced.

Therefore, when the level of mechanical noise in graph A is at a frequency of 150KH2, the output is 300 mV, so it is necessary to lower this output level by about 115o to 1/100, and the cutoff frequency of the bypass filter 11 is set to 300K)1.
2 and the attenuation characteristic is 35-40db10ct,
The output level of the mechanical noise at a frequency of 150 KH2 in graph A decreases to the output level at a frequency of 300 to 500 KH2, which also shows that the above experiment is reliable.

Furthermore, even if the cutoff frequency of the bypass filter 11 is set to 250 KH2, which slightly increases the mechanical noise, the accuracy will only slightly decrease. If a material having a characteristic of ~40 db10 ct or more is used, only the ultrasonic waves of cavitation can be captured extremely efficiently.

That is, the outer wall portion 4a of the cylinder block 4 of the internal combustion engine
The gap 6 between the cylinder liner 2 and the piston 1 is
The cavitation ultrasonic waves are detected and sent to the bypass filter 11, and the output signal of the piezoelectric element 10 that has passed through the bypass filter 11 is compared with the evaluation value T for the output signal of the piezoelectric element 10, which has been determined in advance by experiment. ,
The intensity of cavitation in the gap 6 between the cylinder liner 2 and the piston 1 can be determined.

Note that if a bandpass filter having a high-frequency cutoff characteristic for removing electrical noise is used as the high-noise filter I, the reliability of the evaluation output described above can be further improved.

Further, in the above embodiment, the piezoelectric element 10 is used as a high frequency vibration detector, but as another means for detecting elastic vibration, it is also possible to use something such as a semiconductor strain gauge that can be used in a high frequency range.

4 to 6 are cross-sectional views showing examples of mounting a high-frequency vibration detector on a cylinder block in the cavitation evaluation method of the present invention.

In the example shown in Fig. 4, a piezoelectric element is used as a high-frequency vibration detector]
0 is attached to the cylinder block 4 via the vibration propagation member 20. In this example as well, compared to the case where the piezoelectric element 10 is directly attached to the cylinder block 4 as in the previous embodiment, it is almost the same. Effects can be obtained.

Further, in the example shown in FIG. 5, a part of the cylinder block 4 on which the piezoelectric element 10 is mounted is vibrationally insulated by being blocked by a vibration insulator 30 such as rubber. In the example of FIG. 6, the piezoelectric element 10 is
1, and the side wall of the case 31 and the cylinder block 4
A vibration insulator 30 is installed between the cylinder block 4 and the piezoelectric element 10 so that the piezoelectric element 10 is vibrationally isolated from the cylinder block 4.

In the example of FIGS. 4 and 5, among the ultrasonic waves from cavitation, the ultrasonic waves are transmitted to the piezoelectric element 10 mounted on the insulated cylinder block 4, or the ultrasonic waves are transmitted to the piezoelectric element 10 housed in the case 31. Since only the ultrasonic waves transmitted to other parts of the cylinder block 4 are detected, local cavitation can be detected, further improving the reliability of the cavitation evaluation output. can be done.

As detailed above, according to the method for evaluating cavitation between a cylinder liner and a piston of an internal combustion engine according to the present invention, a high-frequency vibration detector and a bypass filter mounted on the wall of the cylinder block are used to detect cavitation in an internal combustion engine. Vibration due to cavitation between the cylinder liner and piston was detected, and by comparing the output signal of the vibration detector and the evaluation value determined in advance through experiments, it was possible to evaluate the strength of cavitation. This eliminates the need for long-term durability tests that were conventionally done, resulting in significant cost reductions, and has the advantage of being able to evaluate cavitation in an extremely short amount of time. This will enable the development of internal combustion engines to be carried out more efficiently.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing the cylinder and piston portions of a conventional internal combustion engine, and FIGS. 2 and 3 show a method for evaluating cavitation between the cylinder liner and piston of an internal combustion engine as an embodiment of the present invention. Fig. 2 is a system diagram showing a cavitation evaluation system between the cylinder liner and piston, Fig. 3 is a graph showing an experimental example thereof, and Figs. FIG. 3 is a cross-sectional view showing an example of mounting a high-frequency vibration detector on a cylinder block in a cavitation evaluation method. 1... Piston, 2... Cylinder liner, 3... Cooling water passage % 4... Cylinder block, 4a... Outer wall of cylinder block, 5... Connecting rod, 6... Between cylinder liner and piston Gap, 10...Piezoelectric element as a high frequency vibration detector, 11...Bypass filter. 12...Amplifier, 20...Vibration propagation member, 30...Vibration insulator, 31...Case. Sub-Agent Patent Attorney Yoshihiko Iinuma Figure 1 Figure 2 Figure 3 Frequency & (kH2) - Figure 4

Claims (1)

[Claims] In an internal combustion engine, in order to evaluate the cavitation that occurs between the cylinder liner installed in the cylinder block and the piston inside the cylinder liner, a high-frequency vibration detector is attached to the wall of the cylinder block. The output signal of the detection object is set to a cutoff frequency of 250 to 30
0KHz or higher and attenuation characteristic 35-40 db10at
The cavitation signal is passed through a bypass filter having the above characteristics to cut off its low frequency components, and the output signal that has passed through the bypass filter is compared with an evaluation value for the output signal determined in advance by an experiment. 5. A cavitation evaluation method between a cylinder liner and a piston of an internal combustion engine, which is characterized by determining the strength of the .