JP2016130581A - Slide component and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a slide component and its manufacturing method having high abrasion resistance, low sliding resistance, and an excellent sliding property.SOLUTION: In a slide component 10 having a curved sliding face on its outer periphery, the sliding face 11 is composed of a processed face by lathe cutting processing while superposing ultrasonic wave to a cutting tool. A spiral continuous belt-like cutting mark is formed on the sliding face 11, and on the cutting mark, concavo-convex parts are repeatedly formed in a circumferential direction, that is, a cutting direction. By the ultrasonic lathe cutting method, even a material having high abrasion resistance but hard to be processed, can be comparatively easily processed with high accuracy, surface hardening processing by post-processing becomes unnecessary, and texture as an oil reservoir for reducing sliding resistance simultaneously with processing, can be formed with high controllability.SELECTED DRAWING: Figure 1

Description

  The present invention provides a machine product having a sliding mechanism such as a hydraulic valve, which is processed into a desired shape by a cutting method in which ultrasonic waves are superimposed, and at the same time has a fine regularity peculiar to ultrasonic processing on a processed surface. The present invention relates to a sliding component and a method for manufacturing the same, in which a texture is formed, the texture forms an oil submergence, reduces the frictional force of the sliding portion, and improves the wear resistance.

  In order to reduce frictional force and prevent wear of sliding parts, generally harden the sliding surface and supply lubricating oil to the sliding surface so that the sliding part contacts through the oil film. The method is taken. As a method for hardening the surface, heat treatment methods such as quenching, carburizing, and nitriding are frequently used. On the other hand, if the oil film breaks, the frictional force and wear increase at a stretch, so it is important to always form an oil film on the sliding surface.Therefore, there are various methods for forming an uneven oil reservoir on the sliding surface. Has been tried.

  For example, a method of improving the surface roughness of a metal product by machining, such as cutting, grinding, polishing, etc. with a machine tool such as a lathe or a milling machine, a scraping method of scraping the surface of a sliding part little by little, a metal processing surface A method of forming concave dimples on the surface by processing such as sandblasting or shot peening (see, for example, Patent Document 1), and a method of forming controlled dimples by irradiating a pulsed YAG laser (for example, Patent Documents) 2)) is a typical example.

  On the other hand, a grinding method in which a microwave is superimposed during grinding has been studied (for example, see Non-Patent Document 1). By superimposing the vibration, the texture of the unevenness is formed on the processed surface by the abrasive grains buried in the grinding wheel, and an oil sump effect is expected on this texture. In the case of grinding, a grindstone is used, but abrasive grains such as CBN (cubic boron nitride) and diamond grains are embedded in the grindstone.

Japanese Patent No. 3212433 Japanese Patent No. 3890495

FY2010-2012 Strategic Fundamental Technology Advancement Support Project “Development of Micro Ultrasonic / Electrolytic Hybrid Internal Machining System” Research and Development Results Report (March 2013)

However, hard materials with high wear resistance are difficult to process. In addition, after processing into a desired shape with an easy-to-process material, the surface is hardened by post-processing, and unevenness that becomes a reservoir of lubricating oil is formed by post-processing. It will drop to.
In the case of processing such as sand blasting or shot peening, it is difficult to form dent dimples whose shape and distribution are controlled.
For grinding, abrasive grains embedded with CBN (Cubic Boron Nitride) or diamond grains are used, but abrasive grains that are distributed in shape and size are irregularly embedded, and the shape and distribution of the texture. It is difficult to control. Since the sliding characteristics greatly depend on the texture shape and distribution of the sliding surface, a texture forming technique with high controllability in accordance with the sliding member and the sliding mechanism is required.

  The present invention has been made based on such problems, and an object of the present invention is to provide a sliding component exhibiting excellent sliding characteristics with high wear resistance and low sliding resistance, and a method for manufacturing the same. .

  The sliding component of the present invention has a curved sliding surface on the outer periphery, and the sliding surface is a machining surface obtained by lathe cutting by superposing ultrasonic waves on a cutting tool.

  The manufacturing method of the sliding component of the present invention is to manufacture a sliding component having a curved sliding surface on the outer periphery, and the sliding surface is processed by lathe cutting with superposition of ultrasonic waves on a cutting tool. To do.

  According to the present invention, since the sliding surface is subjected to lathe cutting by superimposing ultrasonic waves on the cutting tool, it is relatively easy to achieve high accuracy even for materials that are hard but difficult to machine. Can be processed. Therefore, a texture that becomes an oil reservoir can be formed with high controllability, and a sliding component that exhibits excellent sliding characteristics with high wear resistance and low sliding resistance can be easily obtained. Further, the surface hardening treatment by post-treatment is not necessary, and the texture that becomes the oil reservoir for reducing the sliding resistance simultaneously with the processing can be formed with high controllability, so that the productivity can be greatly improved. .

It is a figure showing the structure of the sliding component which concerns on one embodiment of this invention. It is the optical microscope photograph of the sliding surface processed by the conventional cutting method and the ultrasonic cutting method. It is a characteristic view showing the measurement result of the surface roughness in the cutting direction of the sliding surface processed by the conventional cutting method and the ultrasonic cutting method. It is a figure explaining the measurement principle of frictional force. It is a characteristic view which shows the measurement data of the coefficient of friction for test time to 55 second-75 second. It is a characteristic view which shows the measurement data of a friction coefficient from 470 seconds to 490 seconds for a test time. It is a characteristic view showing the change of the friction coefficient in the frequency | count of reciprocating sliding. It is a characteristic view showing the variation rate of the friction coefficient in the number of reciprocating sliding. It is a characteristic view showing the standard deviation of the friction coefficient in the number of reciprocating sliding.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a configuration of a sliding component according to an embodiment of the present invention. This sliding component 10 has a curved sliding surface 11 on the outer periphery, and this sliding surface 11 is constituted by a machining surface obtained by lathe cutting by superposing ultrasonic waves on a cutting tool. The sliding surface 11 is, for example, a cylindrical surface, and may have a plurality of cylindrical surfaces having different diameters. Moreover, at least a part may be tapered like a conical surface or a side surface of a truncated cone.

  As described above, a machining method in which ultrasonic waves are superimposed on a machining tool at the time of cutting is known as an ultrasonic cutting method. In the ultrasonic cutting method, the machining blade is ultrasonically vibrated, and machining is performed by the machining blade periodically acting on the workpiece. Therefore, compared with the conventional cutting method in which machining is performed while the cutting edge is always in contact with the workpiece, heat generation at the machining site is suppressed, the load on the cutting tool is reduced, and stress during cutting is concentrated on the cutting edge. It has an excellent feature that the damage to the cut object is low, and it is suitable for processing difficult-to-cut materials with high hardness.

  However, in the ultrasonic cutting method, when the cutting speed is slowed down to about 30 m / min, an excellent effect can be obtained as described above, but a general cutting speed of general-purpose lathe processing, for example, 150 m / min. If the speed is as fast as ˜250 m / min, the machining blade does not move away from the workpiece, so the cutting method is not different from the conventional cutting method in which machining always proceeds while the cutting edge is in contact with the workpiece, and the effect of superimposing ultrasonic waves is not exhibited. I have been told. For this reason, the ultrasonic cutting method cannot increase the cutting speed, has low production efficiency, and has not been used for production in which many machinings are performed.

  However, the research results of the inventors etc. (Yusuke Hara, Hiroshi Isobe, Takuro Sato, Moriho Sato “Study on Ultrasonic Vibration Assisted High Speed Cutting (4th Report) —High Speed Vibration Cutting of Electromagnetic Stainless Steel”) According to the Academic Conference Autumn Meeting Annual Conference Proceedings, p. 625-626 (2014)), for the sliding component 10 having the curved sliding surface 11 on the outer periphery, the sliding surface 11 is superposed on the cutting tool. When turning a lathe, the cutting speed is increased to, for example, 150 m / min to 250 m / min, and the ultrasonic vibration force is increased even at the cutting speed at which the processing blade is said not to be separated from the workpiece. Thus, the same effect as that obtained when superposing ultrasonic waves at a low cutting speed can be obtained. Thus, according to the ultrasonic cutting method, regardless of the cutting speed, since the cutting tool periodically acts on the workpiece by ultrasonic vibration, a periodic texture is inevitably formed on the processed surface. I found out that

  FIG. 2 shows a micrograph of a processed surface of SUS304, a cylindrical member having a diameter of 11 mm, which is cut by a conventional lathe cutting method without superimposing ultrasonic waves, and when the same material is cut by an ultrasonic lathe cutting method. The micrographs of the processed surfaces are compared and shown. FIG. 3 shows the result of measuring the unevenness of the machined surface in the cutting direction. As shown in FIG. 2, the conventional method has a continuous cutting trace that is almost flat, but the ultrasonic lathe cutting method forms a beautiful texture with a controlled shape and pitch. Specifically, a strip-shaped cutting trace that is continuous in a spiral shape is formed on the sliding surface 11 by an ultrasonic lathe cutting method, and the cutting trace is repeatedly uneven in the circumferential direction, that is, the cutting direction. Is formed.

  This texture is formed at the same time as processing if processed by an ultrasonic lathe cutting method. Further, it is considered that the texture formed by this ultrasonic lathe cutting method acts as an oil sump, thereby reducing the friction coefficient of the sliding surface 11 and improving the wear resistance. By changing the amplitude and depth of cut for the height and depth of the texture, the pitch can be easily controlled and formed to an optimum value by a combination of the ultrasonic frequency and cutting speed. When the textured surface thus formed is an oil-lubricated sliding surface, the texture functions as a good oil reservoir and greatly contributes to reducing the frictional force. The frictional force can be measured as follows, for example.

The frictional force can be measured by, for example, the apparatus shown in FIG. Specifically, for example, the measurement container 22 in which the stage 21 is disposed is filled with the lubricating oil 23, the sliding component 10 is fixed to the stage, and the measuring element 24 is applied to the sliding surface 11 to the measuring element 24. A vertical static load (N) is applied, and the stage 21 that can be said to be fixed while the sliding component 10 is fixed in this state is reciprocated to obtain the frictional force (F) by the load cell. In addition, the friction coefficient (μ) representing the magnitude of friction is obtained by the following formula 1 from the vertical static load (N) and the friction force (F).
(Formula 1) μ = F ÷ N

  The sliding component 10 is preferably made of, for example, a metal material and is made of a hard material having high wear resistance. For example, in the sliding part 10 such as a solenoid valve core, iron-cobalt electromagnetic stainless steels KM-38 and KM-45 (Tohoku Special Steel Co., Ltd.) are used as hard materials having high wear resistance. The Hard materials are difficult to process, but according to the ultrasonic lathe cutting method, it can be processed into a desired shape relatively easily.

The effects of machining sliding parts by the ultrasonic lathe cutting method are summarized as follows.
(1) Since difficult-to-cut materials with high wear resistance can be used, post-treatment for surface hardening becomes unnecessary.
(2) It is possible to form a texture that functions as an oil reservoir simultaneously with shape processing.
(3) The texture which becomes an oil sump can be formed regularly, and the sliding resistance reduction effect is large.
(4) The texture pitch, height and depth can be easily controlled to optimum values.
As described above, according to the present embodiment, it is possible to provide a high-performance sliding component having high precision processing, high wear resistance, and low sliding resistance with high productivity. Therefore, if a material to be a sliding part is processed into a desired shape by an ultrasonic lathe cutting method, it can be put to practical use as a sliding part having excellent sliding characteristics.

  A cylindrical member having a diameter of SUS304 and a diameter of 11 mm was prepared, and a cutting part 10 was obtained by cutting each of the normal and conventional lathe cutting methods without superimposing ultrasonic waves. Table 1 shows the conditions in each cutting method.

  The optical micrograph of the sliding surface 11 of the obtained sliding component 10 is as shown in FIG. 2, and the measurement result of the surface roughness in the cutting direction of the sliding surface 11 is as shown in FIG. As shown in FIGS. 2 and 3, a unique regular texture was formed on the sliding surface 11 processed by the ultrasonic lathe cutting method.

  Further, the frictional force of the obtained sliding component 10 was measured as shown in FIG. As the measuring device, a tribomaster Type μV1000 is used, the sliding part 10 is immersed in the lubricating oil 23 with the sliding part 10 on its side, both ends are fixed to the stage 21, and the measuring element 24 has a diameter of 4 mm made of SUS303 whose end face is polished. The columnar bar was used, the end face was placed vertically against the sliding surface 11, a vertical static load of 4.9 N was applied, and the stage was reciprocated at a speed of 10 mm / sec. The frictional force was obtained with the load cell when moving the stage. In addition, the friction coefficient was obtained from the vertical load and the obtained friction force.

  The results obtained are shown in FIGS. FIG. 5 shows the friction coefficient measurement data for the test time from 55 seconds to 75 seconds, and FIG. 6 shows the friction coefficient measurement data for the test time from 470 seconds to 490 seconds. The sign of the friction coefficient corresponds to the direction of the frictional force in the reciprocating sliding motion. FIG. 7 shows the change of the friction coefficient with the number of reciprocating slides, FIG. 8 shows the variation rate of the friction coefficient with the number of reciprocating slides, and FIG. 9 shows the friction coefficient with the number of reciprocating slides. The standard deviation is shown. In addition, the friction coefficient shown in FIG. 7 is an average friction coefficient at each sliding.

  As can be seen from FIGS. 5 and 6, according to the sliding component 10 machined by the ultrasonic lathe cutting method, the variation of the friction coefficient during the sliding motion is small and the frictional force is smaller than that of the normal cutting method. The coefficient average value was also small. In addition, the sliding component 10 machined by the ultrasonic lathe cutting method had a friction coefficient of 50% or more smaller than that of the normal conventional cutting method.

  Furthermore, as shown in FIG. 7, according to the sliding component 10 machined by the ultrasonic lathe cutting method, the friction coefficient is stable and very small as 0.15 or less in the number of reciprocating sliding up to 200 times. Value. On the other hand, in the normal cutting method, the coefficient of friction increases as the number of reciprocating slides increases, and the coefficient of friction exceeds 0.2 when the number of reciprocating slidings exceeds 30. As the frictional force increased, the friction coefficient tended to decrease after increasing further, but was a value larger than 0.2.

  In addition, as shown in FIG. 8, according to the sliding part 10 processed by the ultrasonic lathe cutting method, the fluctuation of the friction coefficient is small in the number of reciprocating sliding up to 200 times, and both are 50% or less. On the other hand, the usual cutting method often exceeds 60% as a whole and sometimes exceeds 100%. Furthermore, as shown in FIG. 9, according to the sliding component 10 machined by the ultrasonic lathe cutting method, the standard deviation of the friction coefficient is small in the number of reciprocating sliding operations up to 200 times, both of which are 0.011. In contrast, the conventional cutting method often exceeded 0.03 and sometimes exceeded 0.05.

  From the above results, it was found that the friction coefficient can be stably reduced by the ultrasonic lathe cutting method. That is, according to the ultrasonic lathe cutting method, it was found that excellent sliding characteristics with high wear resistance and low sliding resistance can be obtained.

  The present invention has been described with reference to the embodiment. However, the present invention is not limited to the above embodiment, and various modifications can be made.

  It can be used for sliding parts that rotate or linearly move.

  DESCRIPTION OF SYMBOLS 10 ... Sliding component, 11 ... Sliding surface, 21 ... Stage, 22 ... Measuring container, 23 ... Lubricating oil, 24 ... Measuring element

Claims (3)

A sliding component having a curved sliding surface on the outer periphery,
The sliding part according to claim 1, wherein the sliding surface is a machined surface obtained by lathe cutting by superposing ultrasonic waves on a cutting tool.   The sliding surface according to claim 1, wherein the sliding surface has a strip-shaped cutting trace that is continuous in a spiral shape, and irregularities are repeatedly formed in the circumferential direction on the cutting trace. parts. A manufacturing method of a sliding component having a curved sliding surface on the outer periphery,
A method of manufacturing an oscillating component, characterized in that the sliding surface is machined by a lathe cutting process with ultrasonic waves superimposed on a cutting tool.