JP4792005B2 - Ultrasonic measurement method such as film thickness and ultrasonic measurement system such as film thickness - Google Patents

Description

  The present invention relates to a film thickness of a lubricating film formed between a first object and a second object movable relative to the first object, mixing of bubbles into the lubricating film, the first object and the first object. The present invention relates to an ultrasonic measurement method such as a film thickness and an ultrasonic measurement system such as a film thickness for measuring the direct contact of two objects using an ultrasonic probe, and in particular, the width dimension of the second object is excessive. The present invention relates to an ultrasonic measurement method such as a film thickness and an ultrasonic measurement system such as a film thickness that are similar to the size of an acoustic probe and are useful when the influence of the side surface portion of a second object must be sufficiently taken into consideration. Is.

  A technique for measuring the film thickness of a lubricating film formed between a first object and a second object using an ultrasonic probe is known. For example, when measuring the film thickness of a lubricating film (oil film) formed between a cylinder (corresponding to a first object) and a piston ring (corresponding to a second object) provided in a bicycle engine, an ultrasonic probe is used. Tentacles are used.

By the way, in recent years, internal combustion engines mounted on automobiles have reduced CO ₂ emissions for the preservation of the global environment, and demands for further fuel savings are increasing. Therefore, a low-viscosity lubricating oil or a thin piston ring is used, and the lubricating region tends to shift to a more severe region. In order to develop a piston ring in a stable state even in such a harsh region, observation of the lubricating film formed between the piston ring and the cylinder, particularly the film thickness measurement, is an important point.

  For example, Patent Documents 1 and 2 below are known as systems that measure the state of the interface between a first object and a second object using an ultrasonic probe. In these prior arts, an ultrasonic wave is transmitted from an ultrasonic probe to a measurement location, the ultrasonic wave reflected from the measurement location is received by the same ultrasonic probe, and the received reflected wave is analyzed. Thus, the state of the measurement location is measured. That is, an ultrasonic probe that is used for both transmission and reception is used. In addition, such a measuring method measures based on a reflected wave and shall call a reflection type.

JP 2006-214905 A JP 2006-214904 A

In performing the measurement of the lubricant film formed between the cylinder and the piston ring, when measured by the reflection measuring method, paste the ultrasound probe 3 on the back side of the piston ring 2, as shown in FIG. 11, The ultrasonic wave S is irradiated toward the lubricating film L formed between the cylinder 1 and the piston ring 2. The ultrasonic wave S travels from the piston ring 2 to the inside of the lubricating film L, undergoes multiple reflections at the lubricating film L, and is then reflected again in the direction of the ultrasonic probe 3. The reflected wave is received by the ultrasonic probe 3, and the film thickness of the lubricating film L can be measured from the echo height signal of the reflected wave. That is, the film thickness information of the lubricating film can be grasped as the magnitude of the echo height. Further, the relationship between the magnitude of the echo height and the film thickness can be expressed by a theoretical formula, and the film thickness can be obtained by calculation from the echo height under the condition that the theoretical formula is satisfied.

  However, the width dimension of the piston ring is thin, and when analyzing with an ultrasonic flaw detector, it is called a drive-in area (dead zone area) within a predetermined time after transmitting the ultrasonic wave, and the received signal is not stable. There is an area. For this reason, the reflected wave from the film portion appears in the dead zone region of the ultrasonic flaw detector, and the relation between the echo height (the magnitude of the reflected wave) and the film thickness obtained here does not hold the theoretical formula. If the theoretical formula does not hold, it is necessary to obtain a calibration curve representing the relationship between the echo height and the film thickness in advance. Such a calibration curve needs to be obtained for each different condition, for example, depending on the size of the piston ring 2, the state of attachment of the ultrasonic probe 3, the temperature condition, and the like, and a rather complicated operation is required. The

  In order to cope with this, a delay material such as an acrylic column is attached to the back surface of the piston ring 2 and an ultrasonic probe 3 is attached to the back surface, thereby making it possible to increase the path and from the film portion after the dead zone region. The echo height appears, and there is a possibility that the film thickness can be estimated from the echo height by a theoretical formula.

  However, since the ultrasonic wave S emitted from the ultrasonic probe 3 is emitted in a wide state as shown in FIG. 11, the ultrasonic probe is considered in consideration of the width dimension and thickness dimension of the piston ring 2. The reflected wave received by the toucher 3 includes not only the film thickness information of the lubricating film but also the reflected wave from the side surface 2c of the piston ring 2 (information such as bubbles and direct contact not related to the film thickness information: "Information other than film thickness") is also included. Under such circumstances, it is difficult to accurately measure the film thickness when the calibration curve is obtained in advance.

  What is measured by the ultrasonic probe 3 is mainly the film thickness of the lubricating film, but in addition to this, the presence of bubbles and the direct contact state between the cylinder 1 and the piston ring 2 (information other than the film thickness described above) ) Is desired to be detected. This is because the information is also greatly related to the performance of the engine, and it is demanded that it can be individually measured. When such measurement is performed by a reflective measurement method, there is a high possibility that information such as bubbles is buried together with the film thickness information, and it is difficult to measure the bubbles and the direct contact state in a state separated from the film thickness information.

  This is because the information about the mixing of bubbles and the direct contact is mainly information obtained from the side surface portion 2c of the piston ring 2, and according to the reflective measurement method, information such as bubbles is only contained in the film thickness information. It was not possible to determine whether the change in echo height was due to a change in film thickness, whether it was due to the inclusion of bubbles, or due to direct contact.

  The present invention has been made in view of the above circumstances, and the problem is that it is possible to acquire film thickness information in a state in which information other than the film thickness is excluded as much as possible, and further, air bubbles other than the film thickness information are mixed in or directly. An object of the present invention is to provide an ultrasonic measurement method such as a film thickness and an ultrasonic measurement system such as a film thickness that can accurately measure contact information. It is another object of the present invention to provide an ultrasonic measurement method such as a film thickness and an ultrasonic measurement system such as a film thickness that can determine the film thickness from the echo height by a theoretical formula without using a calibration curve.

In order to solve the above problems, an ultrasonic measurement method such as a film thickness according to the present invention,
A lubricating film formed between the first object and a second object that is movable relative to the first object and has a size comparable to that of the ultrasonic probe to be attached. An ultrasonic measurement method for measuring film thickness, mixing of bubbles in a lubricating film, and direct contact between a first object and a second object using an ultrasonic probe,
A first ultrasonic probe using a first ultrasonic probe for transmitting ultrasonic waves attached to a first object and a second ultrasonic probe for receiving ultrasonic waves attached to a second object. Transmitting ultrasonic waves from a child toward the lubricating film; and receiving ultrasonic waves transmitted through the lubricating film by a second ultrasonic probe;
Of the waves included in the waveform signal received by the second ultrasonic probe, the wave that first passes through the lubricating film and reaches the second ultrasonic probe is defined as the first wave, and the second ultrasonic probe. The ultrasonic wave reflected at the interface between the child and the second object is re-reflected at the interface with the lubricating film, and the wave that has reached the second ultrasonic probe is changed to the second wave and travels in the same way as the second wave. The reflected ultrasonic wave is reflected again at the interface between the second ultrasonic probe and the second object, and is reflected again at the interface with the lubricating film, so that the wave that has reached the second ultrasonic probe is converted into the third wave. And measuring the film thickness based on the first wave, and measuring the mixing of bubbles and / or the direct contact based on the second wave and / or the third wave. It is what.

  The operation and effect of the ultrasonic measurement method for the film thickness and the like with such a configuration will be described. In the present invention, not only the film thickness of the lubricating film formed between the first object and the second object, but also the mixing of bubbles into the lubricating film and the direct contact between the first object and the second object (the first object and the first object). This also refers to contact with the corners and side surfaces of two objects, and so on. For that purpose, two ultrasonic probes are used, one is a transmitting ultrasonic probe attached to the first object, and the other is a receiving ultrasonic probe attached to the second object. It is a tentacle. At the time of measurement, ultrasonic waves are irradiated from the first ultrasonic probe toward the lubricating film. The ultrasonic wave passes through the lubricating film, passes through the inside of the second object, and then reaches the second ultrasonic probe. According to such a configuration, the first wave that first reaches the second ultrasonic probe does not include the influence of reflection from a portion other than the lubricating film near the center of the width of the second object, Information that is affected only by the film thickness can be acquired.

  Further, the waves received by the second ultrasonic probe are reflected by the ultrasonic waves reflected at the interface between the second ultrasonic probe and the second object and re-reflected at the interface with the lubricating film. The second wave that has reached the acoustic probe or the ultrasonic wave that has traveled in the same way as the second wave is reflected again at the interface between the second ultrasonic probe and the second object, and further at the interface with the lubricating film. There are also third waves that have reached the second ultrasonic probe due to re-reflection, but these are acquired in a state shifted in time from the first wave. In addition, the reflected wave at such an interface includes information on the mixture and direct contact of bubbles other than the lubricating film generated at the corners and side surfaces of the second object due to the diffusion of ultrasonic waves due to the long path length. It is. Therefore, the film thickness information and other information such as bubbles can be acquired individually, and the film thickness information can be acquired in a state where information other than the film thickness is excluded as much as possible. In addition, it is possible to accurately measure air bubble mixing and direct contact information other than film thickness information.

  In the present invention, it is preferable to have a step of calculating the film thickness based on the maximum echo height data obtained from the first wave and a theoretical formula representing the relationship between the echo height and the film thickness.

  According to the present invention, the first wave included in the received wave of the second ultrasonic probe appears outside the dead band of the ultrasonic flaw detector, and information other than the film thickness information near the width center is excluded as much as possible. Therefore, the film thickness can be calculated from the echo height based on the theoretical formula. Moreover, although this point is mentioned later, it became clear experimentally. Therefore, it is possible to save the trouble of obtaining the calibration curve and to measure the film thickness and the like efficiently.

  In the present invention, within the detection region of the second ultrasonic probe, the average film thickness value obtained in a state where the first object and the second object are in contact with each other, the measured echo height, and the theoretical formula It is preferable to calculate the film thickness based on this.

  The lubrication surfaces of the first object and the second object actually have surface roughness, and the lubrication surface is not a perfect plane. For example, it may be formed in a curved surface like a crowning of a piston ring. . Therefore, as described above, the average film thickness value is obtained by bringing the first object and the second object into contact with each other, and the actual film thickness can be calculated from the film thickness value, the echo height, and the theoretical formula. . Thereby, calculation with higher accuracy can be performed.

  In the present invention, it is preferable to have a step of detecting the mixing of bubbles by reducing the maximum echo height value that depends only on the film thickness obtained from the second wave and / or the third wave.

  When an experiment was performed by actually generating bubbles, it was confirmed that the maximum echo height obtained from the second wave and / or the third wave decreased from a value depending only on the film thickness. Therefore, the mixing of bubbles can be measured based on the second wave and / or the third wave.

  In the present invention, it is preferable to include the step of detecting the direct contact by increasing the maximum echo height value that depends only on the film thickness obtained from the second wave and / or the third wave.

  When an experiment was performed by actually generating direct contact, it was confirmed that the maximum echo height obtained from the second wave and / or the third wave increased from a value depending only on the film thickness. Therefore, direct contact information can be measured based on the second wave and / or the third wave.

In order to solve the above-mentioned problem, an ultrasonic measurement system such as a film thickness according to the present invention is provided.
Lubricant film formed between a first object and a second object that is movable relative to the first object and has a size comparable to that of an ultrasonic probe to be attached. An ultrasonic measurement system for measuring the thickness, mixing of bubbles into a lubricating film, and the film thickness for measuring direct contact between a first object and a second object using an ultrasonic probe,
A first ultrasonic probe for ultrasonic transmission attached to the first object;
A second ultrasonic probe for receiving ultrasonic waves attached to the second object, transmitting ultrasonic waves from the first ultrasonic probe toward the lubricating film, and transmitting the ultrasonic waves through the lubricating film Is configured to be received by the second ultrasonic probe,
Of the waves included in the waveform signal received by the second ultrasonic probe, the wave that first passes through the lubricating film and reaches the second ultrasonic probe is defined as the first wave, and the second ultrasonic probe. The ultrasonic wave reflected at the interface between the child and the second object is re-reflected at the interface with the lubricating film, and the wave that has reached the second ultrasonic probe is changed to the second wave and travels in the same way as the second wave. The reflected ultrasonic wave is reflected again at the interface between the second ultrasonic probe and the second object, and is reflected again at the interface with the lubricating film, so that the wave that has reached the second ultrasonic probe is converted into the third wave. And a waveform analysis means for measuring the film thickness based on the first wave and measuring the direct contact based on the second wave and / or the third wave. It is characterized by this.

  The operation and effect of the ultrasonic measurement system such as the film thickness by such a configuration is as described above, and the film thickness information can be acquired in a state where information other than the film thickness is excluded as much as possible. It is possible to accurately measure the air bubble contamination and direct contact information.

  A preferred embodiment of an ultrasonic measurement method and system for film thickness and the like according to the present invention will be described with reference to the drawings. The lubricating film to be measured will be described with an oil film formed between the cylinder (corresponding to the first object) and the piston ring (corresponding to the second object) as an example, but the present invention is not limited to this. It is not something. Further, the width of the piston ring is smaller than that of the cylinder, which is about the same as the size (diameter) of the ultrasonic probe. Therefore, using the reflection type measurement method as described above is useful when accurate oil film measurement cannot be performed. By using the transmission type measurement method described later, measurement of oil film and the like can be performed with high accuracy. Is something that can be done.

<Measurement principle>
First, in the present invention, the principle when the film thickness of an oil film is measured using an ultrasonic probe will be described. FIG. 1 is a conceptual diagram showing the principle of a measurement system. FIG. 2 is a diagram illustrating an example of the received echo height signal.

  An oil film F having a thickness L is formed between the cylinder 1 corresponding to the first object and the piston ring 2 corresponding to the second object. The oil film F is formed between the lubricating surface 1 a of the cylinder 1 and the lubricating surface 2 a of the piston ring 2. Although the cylinder 1 is fixed, the piston ring 2 actually reciprocates in the vertical direction.

  A mounting surface 1b is provided in parallel to the lubricating surface 1a on the opposite side of the lubricating surface 1a of the cylinder 1, and a first ultrasonic probe 11 for transmitting ultrasonic waves is mounted. A mounting surface 2b is provided in parallel to the lubricating surface 2a on the opposite side of the piston ring 2 from the lubricating surface 2a, and the receiving second ultrasonic probe 12 is mounted. That is, measurement is performed by a combination of two ultrasonic probes, and for the sake of convenience, this is referred to as a transmission measurement method in order to distinguish this from a conventional reflection measurement method.

  From the first ultrasonic probe 11, ultrasonic waves are emitted in the direction of the oil film F. The ultrasonic wave passes through the oil film as it is, or after multiple reflection within the oil film, it passes through the inside of the piston ring 2 and reaches the second ultrasonic probe 12 and is received. This is called a first transmitted wave (first wave).

Some of the ultrasonic waves propagated like the first transmitted wave are reflected at the interface M ₂₁ between the second ultrasonic probe 12 and the piston ring 2 and are directed again toward the oil film F. This wave is either re-reflected at the interface M ₂₂ between the piston ring 2 and the oil film F, or again reflected again within the oil film, and then propagates inside the piston ring 2 and reaches the second ultrasonic probe 2 and is received. Is done. This is called a second transmitted wave (second wave).

In addition, a part of the ultrasonic wave that has traveled in the same manner as the second transmitted wave is reflected again at the interface M ₂₁ between the second ultrasonic probe 12 and the piston ring 2, and goes again toward the oil film F. Further, the light is reflected again at the interface M ₂₂ between the piston ring 2 and the oil film F, so that it reaches the second ultrasonic probe 12 again and is received. This is called a third transmitted wave (third wave).

  FIG. 2 shows the magnitude of the echo height h, which is the actually measured received wave. The vertical axis indicates the magnitude of the echo height h, and the horizontal axis indicates the ultrasonic propagation distance (or time). As shown in FIG. 2, the first transmitted wave, the second transmitted wave, and the third transmitted wave can be captured in a separable state.

  Actually, the first ultrasonic probe 11 having a length sufficiently larger than the width dimension A (about 1.2 mm) of the piston ring 2 is attached to the cylinder 1. That is, the first ultrasonic probe 11 has a sufficiently large length as compared with the second ultrasonic probe 12 attached to the piston ring 2. Diffusion is not a problem.

  Therefore, what is received as the first transmitted wave is not reflected on the side surface portion 2c of the piston ring 2 and, as can be seen from the experimental results described later, near the center of the width of the piston ring 2. Oil film information can be obtained. Therefore, it is possible to acquire information that is affected only by the film thickness while excluding information other than the film thickness as much as possible.

  In addition, since the second transmitted wave and the third transmitted wave are reflected several times by the interface, the ultrasonic wave that originally propagated at an angle gradually moves to the side surface of the piston ring 2 according to the path length of the propagation path. It is received by being diffused in the direction of the part 2c and reflected from the side part 2c. That is, since the reflected wave from the side part 2c or a position close to the side part 2c is included, information in the region is included. Therefore, it can be received in a form including information on the mixing of bubbles and direct contact. Incidentally, in the stroke in which the piston ring 2 reciprocates, the edge portion of the piston ring 2 directly contacts the cylinder 1 due to the inclination of the piston ring 2. Furthermore, it is possible to measure the adhesion of oil to the side surface portion of the piston ring 2 by the third transmitted wave that is easily affected by the side surface portion 2c due to the reflection in the piston ring 2 again.

<Experimental equipment>
Next, an experiment for verifying the effect of the ultrasonic measurement system such as the film thickness according to the present invention was performed. The experimental apparatus is shown in FIG.

  First, the pseudo cylinder 10 functioning as the cylinder 1 was disposed in the lower part, and the first ultrasonic probe 11 was attached to the back side. The piston ring 2 was held by the ring holder 13 and sufficient lubricating oil was supplied between the pseudo cylinder 10 and the piston ring 2. A second ultrasonic probe 12 is affixed to the inner surface side of the piston ring 2.

  The ring holder 13 can be moved in the vertical direction by the micrometer head 14, whereby the setting of the oil film thickness can be changed. The set oil film thickness can be read by the non-contact type displacement sensor 17. Whether or not the pseudo cylinder 10 and the piston ring 2 are in direct contact with each other is determined from the feel when the micrometer head 14 is operated and the degree of decrease in the amount of fluctuation in the echo height. Of course, methods other than those described above may be used for setting the oil film thickness and setting direct contact.

  The first ultrasonic probe 11 and the second ultrasonic probe 12 are each connected to an ultrasonic flaw detector 15, and this ultrasonic flaw detector 15 is further connected to a computer 16 (personal computer). . The ultrasonic flaw detector 15 and the computer 16 can analyze a wave included in the echo height received by the second ultrasonic probe 12 (function as waveform analysis means), display a waveform, and the like.

  In addition, the ultrasonic probe used in the experiment used the first ultrasonic probe 11 based on PVDF (polyvinylidene fluoride film) and PZT (lead zirconate titanate). Although the composite type is used as the second ultrasonic probe 12, the type of the ultrasonic probe to be used is not particularly limited in the present invention.

  FIG. 4 is a graph showing actual measurement data. The direct contact between the pseudo cylinder 10 and the piston ring 2 was created in a pseudo manner by applying the metal piece 20 to the edge of the piston ring 2 as shown in FIG. The metal piece 20 was made of the same material as the piston ring 2. As for the mixing of bubbles, the bubbles 21 were intentionally generated in the vicinity of the edge of the piston ring 2 as shown in FIG. Moreover, mixing of bubbles was performed by the following method. Bubbles are generated by a microsyringe, the size is about φ0.8 mm, and the number is one.

The experimental results are shown in FIGS. 4 (a) and 4 (b), respectively. In the graph, the A wave is the first transmitted wave, B is the second transmitted wave, and C is the third transmitted wave. Since the material, dimensions, set oil film thickness, ultrasonic frequency to be used, and the like of the pseudo cylinder 10 and the piston ring 2 are known in advance, the first transmitted wave and the second transmitted wave are related to the horizontal axis (propagation distance). Waves and third transmitted waves can be identified.

In FIG. 4 (a), are compared echo height of the size of the case where there a case where there is no direct contact. As for the echo height, the maximum echo height (peak value) is compared. For the first transmitted wave, no change was seen in the echo height regardless of the presence or absence of direct contact. That is, it can be seen that the first transmitted wave is not affected by the side surface (edge) of the piston ring 2. Thereby, it is considered that the first transmitted wave includes only information depending on the oil film thickness.

  On the other hand, comparing the second transmitted wave and the third transmitted wave, it was found that the echo height increases due to the direct contact. In particular, it was confirmed that the third transmitted wave changed greatly.

In FIG. 4 (b), by comparing the echo height of the size with and without air bubbles. The echo height is similarly compared for the maximum echo height. As for the first transmitted wave, as in the case of direct contact, no change was seen in the echo height regardless of the presence or absence of bubbles. That is, it can be seen from this point that the first transmitted wave is not affected by the side surface of the piston ring 2.

  Comparing the second transmitted wave and the third transmitted wave, it was found that the echo height decreases due to the presence of bubbles. It can be seen that the second transmitted wave is slightly smaller than the third transmitted wave.

  From the above points, it is understood that oil film thickness, bubble mixing, and direct contact can be individually measured by using a transmission type measurement method. In particular, the oil film thickness can be measured by the first transmitted wave, and whether the bubble is mixed or directly contacted by the increase or decrease of the echo height by the second transmitted wave or the third transmitted wave. Identification is also possible.

この式において、Ｚ₁は擬似シリンダ１０とピストンリング２の音響インピーダンスを示す。なお、擬似シリンダ１０とピストンリング２は同じ材質のものを使用しており、実験では、鋼製のものを使用した。Ｚ₂は油膜の音響インピーダンスである。使用した潤滑油は無添加鉱油である。また、式中におけるｋは、ｋ＝２πｆ／Ｃ₂ で表される。 <Relationship with theoretical formula>
FIG. 6 is a diagram showing a comparison between the value calculated by the theoretical formula and the experimental result. The relationship between the echo height ratio and the average oil film thickness L _H is expressed by the following equation.

In this equation, Z ₁ represents the acoustic impedance of the pseudo cylinder 10 and the piston ring 2. The pseudo cylinder 10 and the piston ring 2 are made of the same material, and steel was used in the experiment. Z ₂ is the acoustic impedance of the oil film. The lubricating oil used was additive-free mineral oil. Further, k in the formula is represented by k = 2πf / C ₂ .

f is the center frequency of the ultrasonic wave, and 2 MHz was used in the experiment. C ₂ is the speed of ultrasonic waves in the lubricating oil.

Strictly speaking, L _H in the above theoretical formula should be calculated as follows. FIG. 8 is an enlarged schematic view showing the lubrication surfaces of the cylinder 1 and the piston ring 2. That is, the respective lubricated surfaces 1a and 2a are not strictly smooth surfaces but have surface roughness. The lubrication surface 2a of the piston ring 2 is not a parallel surface to the lubrication surface 1a of the cylinder 1, but is a surface having a slight curvature due to crowning.

Therefore, as shown in FIG. 8, the film thickness detection range determined by the geometric shape (d ₁ , d ₂ ) of the upper surface (piston ring) having the crowning and the flat lower surface (cylinder) (as can be seen from experimental data described later). The average distance within 0.4 mm) is defined as si. Since the shapes of the cylinder 1 and the piston ring 2 used in the experiment are known, this si can be uniquely determined.

L ₀ = si + (R _Y1 + R _Y2 ) / 2
Define The surface roughness R _Y1 + R _Y2 can be determined in advance using a roughness measuring instrument. Therefore, L _{0 is} also a known value. Incidentally, L ₀ can be defined as an average film thickness in a state where the pseudo cylinder 1 and the piston ring 2 are lightly in contact with each other. Even in such a contact state, an oil film exists due to the presence of surface roughness and crowning.

Therefore, the average oil film thickness L _H in the theoretical formula is
L _H = L + L ₀
It is represented by Here, L corresponds to the minimum distance (minimum oil film thickness) between the tips of the roughness protrusions of the cylinder 1 and the piston ring 2, and is data used when the oil film thickness is evaluated. .

The echo height ratio H in the theoretical formula is
H = h / h ₀
It is represented by. h ₀ is an echo height measured in the experimental apparatus shown in FIG. 3 in a state where the pseudo cylinder 10 and the piston ring 2 are extremely lightly in contact with each other. The echo height obtained by standardizing the echo height using this h ₀ is used. Use the ratio H.

It is a method of calculating the h _0, for example, in the apparatus shown in FIG. 3, the piston ring 2 from strongly pressing state with respect to the cylinder 1, examine the change of the echo height h while gradually lowering the contact pressure . The change in the echo height h at this time has a shape as shown in FIG. 10, and a region where the echo height is drastically reduced by changing from the solid contact state to the non-contact state and forming a thick oil film appears. The echo height at this change point can be set to h ₀ . Such a method is a very simple method, and it is not necessary to accurately know the surface pressure between the cylinder 1 and the piston ring 2 when the piston ring 2 is pushed in, and is a very practical method. This h ₀ is set to 100% (= 1).

  FIG. 6 is a graph showing the relationship between the echo height ratio H and the minimum oil film thickness L (μm) obtained by the theoretical formula, and the echo height ratio H and the minimum oil film thickness L (μm) obtained in the experiment. ) Are superimposed and displayed. The setting change of the oil film thickness can be changed by moving the ring holder 13 with a micrometer in FIG.

  As can be seen from FIG. 6, it is understood that the graph of the theoretical formula and the graph obtained experimentally coincide with each other at a problem-free level. In particular, the normal lubricating oil film thickness (about 20 μm or less) agrees well. Incidentally, the echo height h in this graph is created using the maximum echo height in the first transmitted wave. Since it fits well with the theoretical formula, it is not necessary to obtain a calibration curve in advance, and by obtaining the echo height ratio, the oil film thickness can be obtained with high accuracy based on the theoretical formula.

  FIG. 7 shows a comparison between the case where PVDF (length 30 mm × width 10 mm) is used and the case where PZT (φ10 mm) is used as the first ultrasonic probe 11 attached to the pseudo cylinder 10. It is a graph. As can be seen from this graph, similar results are obtained regardless of the type of the ultrasound probe 11.

<Detection region of the second ultrasonic probe>
Next, it was experimentally confirmed to what extent the detection region (sensitivity) of the second ultrasonic probe 12 is. FIG. 9 is a conceptual diagram showing an experimental apparatus for that purpose.

  As shown in FIG. 9A, a pseudo cylinder 10 is prepared, and a thickness gauge 22 having a thickness of 10 μm is attached to the surface thereof. The distance (oil film thickness) between the piston ring 2 and the pseudo cylinder 10 was set to 30 μm. The pseudo cylinder 10 is mounted on the linear motion stage 23 and configured to be movable in the direction of the arrow shown in the figure. FIG. 9B shows a partially enlarged view. The width of the piston ring 2 is 1.2 mm.

  By gradually moving the pseudo cylinder 10 from the left side to the right side in the figure, the oil film thickness varies, so the echo height received by the second ultrasonic probe 12 should change. In FIG. 9B, the end surface 22 a of the thickness gauge 22 is located just below the side surface portion 2 c of the piston ring 2.

The lower graph shows the change in echo height when the thickness gauge 22 is penetrated below the piston ring 2 in units of 0.1 mm. There was no change in the echo height until the approach distance of the thickness gauge 22 was 0.4 mm, and a change was seen when the echo height was 0.5 mm and 0.6 mm (just entered the center of the width of the piston ring 2). Therefore, it can be seen that the detection area by the second ultrasonic probe 12 has a center width of 0.4 mm. Accordingly, in the above theoretical formula, it is sufficient to consider the s _i in the detection region.

<Effect>
The function of the waveform analysis means in the present invention is to extract each of the first transmitted wave, the second transmitted wave, and the third transmitted wave from the echo height signal acquired by the second ultrasonic probe 12, The maximum echo height of the wave is further extracted. By analyzing the change in the maximum echo height of each wave, it is possible to individually measure the oil film thickness, mixing of bubbles, and direct contact (metal contact). Such waveform analysis means can be realized by a function of software installed in the computer 16. It also has a function of displaying the analysis result as shown in each figure in a graph or the like.

  Generally, when a reflected wave is received by an ultrasonic probe and analyzed by an ultrasonic flaw detector, there is a problem of a so-called driving area. That is, there is a region where the received signal is not stable during a predetermined time after transmitting the ultrasonic wave, which is referred to as a driving region (dead zone). This depends on the characteristics of the ultrasonic flaw detector, and the theoretical formulas for the echo height and the oil film thickness cannot be applied in this driving area.

  When the reflection type measurement method is performed with the ultrasonic probe of the piston ring 2 attached, there is a possibility that the reflected wave is received in the driving area due to the relationship with the thickness dimension of the piston ring. Such a point is also a problem of the reflection type measurement method. However, when the transmission type measurement method is used as in the present invention, the first ultrasonic probe 11 is obtained from the relationship between the thickness dimensions of the cylinder 1 and the piston ring 2. And the distance between the second ultrasonic probe 12 and the second ultrasonic probe 12 are sufficient to avoid the follow-up region, and accurate measurement can be performed.

<Another embodiment>
In the present embodiment, an example in which the first object is a cylinder and the second object is a piston ring 2 has been described. However, the present invention is not limited to this, and is applicable to various cases where a lubricating film is formed. It can be done.

Conceptual diagram showing the principle of an ultrasonic measurement system such as film thickness The figure which shows an example of the echo height signal received by an ultrasonic probe Diagram showing the configuration of the experimental apparatus Figure showing measured data The figure which shows the state which created the direct contact and the mixture of bubbles in a pseudo manner Graph showing comparison between theoretical formula and experimental results Graph showing comparison of experimental results obtained when changing the ultrasound probe Enlarged view showing the surface condition of the lubricated surface Conceptual diagram showing an experimental apparatus for confirming the detection region of the second ultrasonic probe Graph showing the change in echo height h when the contact surface pressure is gradually lowered from the state where the piston ring is strongly pressed against the cylinder A diagram showing a method for measuring the thickness of a lubricating film according to the prior art

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cylinder 1a Lubrication surface 1b Attachment surface 2 Piston ring 2a Lubrication surface 2b Attachment surface 2c Side surface part 10 Pseudo cylinder 11 1st ultrasonic probe 12 2nd ultrasonic probe 13 Ring holder 14 Micrometer head 15 Ultrasonic Flaw detector 16 Computer 22 Thickness gauge F Lubricant film

Claims (6)

And thickness of the lubricating film formed between the second object Ru relatively movable der respect to the first object of the first object Toko, and mixed and / or the first object of the bubble into the lubricating film An ultrasonic measurement method such as a film thickness for measuring a direct contact of a second object using an ultrasonic probe,
A first ultrasonic probe using a first ultrasonic probe for transmitting ultrasonic waves attached to a first object and a second ultrasonic probe for receiving ultrasonic waves attached to a second object. Transmitting ultrasonic waves from a child toward the lubricating film; and receiving ultrasonic waves transmitted through the lubricating film by a second ultrasonic probe;
Of the waves included in the waveform signal received by the second ultrasonic probe, the wave that first passes through the lubricating film and reaches the second ultrasonic probe is defined as the first wave, and the second ultrasonic probe. The ultrasonic wave reflected at the interface between the child and the second object is re-reflected at the interface with the lubricating film, and the wave that has reached the second ultrasonic probe is changed to the second wave and travels in the same way as the second wave. The reflected ultrasonic wave is reflected again at the interface between the second ultrasonic probe and the second object, and is reflected again at the interface with the lubricating film, so that the wave that has reached the second ultrasonic probe is converted into the third wave. And measuring the film thickness based on the first wave, and measuring the mixing of bubbles and / or the direct contact based on the second wave and / or the third wave. An ultrasonic measurement method for film thickness and the like. 2. The film according to claim 1, further comprising a step of calculating a film thickness based on maximum echo height data obtained from the first wave and a theoretical expression representing a relationship between the echo height and the film thickness. Ultrasonic measurement method such as thickness. The first object and a second in the state in which the first and second objects obtained from the shape information and the shape information of the second object in our Keru first object in the detection region of the second ultrasonic probe is in contact The method for measuring an ultrasonic wave thickness according to claim 2, wherein the film thickness is calculated based on an average distance between two objects , a measured echo height, and the theoretical formula. Second wave, and / or any one of claims 1 to 3, characterized by the step of detecting the entry of air bubbles by the maximum echo height value obtained from the third wave is reduced An ultrasonic measurement method such as the film thickness described in 1. Second wave, and / or any one of claims 1 to 4, characterized in that it comprises the step of detecting the direct contact by the maximum echo height value obtained from the third wave is increased 1 An ultrasonic measurement method for the film thickness or the like according to the item. And thickness of the lubricating film formed between the second object Ru relatively movable der respect to the first object of the first object Toko, and mixed and / or the first object of the bubble into the lubricating film An ultrasonic measurement system such as a film thickness for measuring a direct contact of a second object with an ultrasonic probe,
A first ultrasonic probe for ultrasonic transmission attached to the first object;
A second ultrasonic probe for receiving ultrasonic waves attached to the second object, transmitting ultrasonic waves from the first ultrasonic probe toward the lubricating film, and transmitting the ultrasonic waves through the lubricating film Is configured to be received by the second ultrasonic probe,
Of the waves included in the waveform signal received by the second ultrasonic probe, the wave that first passes through the lubricating film and reaches the second ultrasonic probe is defined as the first wave, and the second ultrasonic probe. The ultrasonic wave reflected at the interface between the child and the second object is re-reflected at the interface with the lubricating film, and the wave that has reached the second ultrasonic probe is changed to the second wave and travels in the same way as the second wave. The reflected ultrasonic wave is reflected again at the interface between the second ultrasonic probe and the second object, and is reflected again at the interface with the lubricating film, so that the wave that has reached the second ultrasonic probe is converted into the third wave. And a waveform analysis means for measuring the film thickness based on the first wave and measuring the direct contact based on the second wave and / or the third wave. An ultrasonic measurement system for film thickness, etc.

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