Ultrasonic machining device

Abstract

To provide an ultrasonic machining device capable of forming a microtexture with high formation efficiency without transferring a dedicated machining device.SOLUTION: This ultrasonic machining device comprises: an ultrasonic vibration body; a moving mechanism; and a flexible support part. The ultrasonic vibration body includes an ultrasonic vibrator, a vibration horn, and a tool. A surface to be machined is machined while pushing-in the tool to the surface to be machined by the moving mechanism and exciting the ultrasonic vibration body. The flexible support part is disposed at a position where a machining reaction force of a time average by the machining of the surface to be machined and a spring force of a time average of the flexible support part balance. A low-frequency unique vibration number of a system including a mass of the ultrasonic vibration body and a spring constant of the flexible support part is 1 / 10 or smaller.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an ultrasonic processing apparatus.

Background Art

[0002] There are cases where fine depressions (hereinafter referred to as "microtextures") are formed on the surface of a workpiece. By forming microtextures, functionality can be imparted to the surface, such as improving lubricity and the effect of collecting wear powder. From these characteristics, there have been attempts to form microtextures on the sliding surfaces of sliding parts, for example, to improve sliding characteristics by adjusting the coefficient of friction. Microtextures may be formed by shot blasting, etching, electrical discharge machining, etc. These texture formation (texturing) methods require a mask with a formed texture pattern and are likely to have variations in depth and shape. Alternatively, microtextures may also be formed by a method of perforating the surface of the workpiece by laser processing. In addition, these texturing operations involve a transfer from the forming process by machining with a processing apparatus called a machine tool (e.g., a lathe or a milling machine) for processing the shape of the product to a dedicated processing (e.g., shot blasting, etching, electrical discharge machining, laser processing) apparatus for texturing.

[0003] Texturing that requires a dedicated processing apparatus has a problem that the work process becomes complicated due to the transfer. For example, Patent Document 1 discloses a technique that can perform texturing without transfer after machining by using a rotary tool. This is a technique in which a rotating cutting edge forms one texture in one cutting. However, since the rotational speed of the cutting edge is about several thousand times per minute, there is a problem that the number of textures that can be created per unit time (hereinafter referred to as "creation efficiency") is small.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In texturing, a technique that can be formed with high productivity is desired, but the transfer of dedicated processing equipment and the low creation efficiency have been problems. The present invention has been made in view of the above problems, and an object thereof is to provide an ultrasonic processing apparatus that creates a microtexture with high creation efficiency without transferring a dedicated processing apparatus.

Means for Solving the Problems

[0006] As a result of intensive studies by the present inventors, it has been found that the above problems can be solved by having the following configuration, leading to the completion of the present invention.

[0007] (1) An ultrasonic processing apparatus for forming a microtexture on a work surface, comprising an ultrasonic vibrator, a moving mechanism, and a flexible support portion connecting the ultrasonic vibrator and the moving mechanism, the ultrasonic vibrator having an ultrasonic vibrator, a vibration horn, and a tool, while the tool is pushed into the work surface by the moving mechanism and the work surface is processed while the ultrasonic vibrator is excited, the flexible support portion is disposed at a position where the time-average processing reaction force due to the processing of the work surface and the time-average spring force of the flexible support portion are balanced, and the low-frequency natural vibration frequency fp of a system composed of the mass m1 of the ultrasonic vibrator and the spring constant k of the flexible support portion is 1 / 10 or less of the ultrasonic resonance frequency fs of the ultrasonic vibrator. An ultrasonic processing apparatus characterized by the above. (2) The ultrasonic processing apparatus according to (1), characterized in that the low-frequency natural vibration frequency fp is 160 Hz or more, the ultrasonic resonance frequency fs is 20 kHz or more and 30 kHz or less, and the spring constant k of the flexible support portion is 5,000,000 N / m or more. (3) The total amplitude of vibration of the tool is 0.8 μm or more and 25 μm or less along the excitation axis of the ultrasonic vibrator, and the moving mechanism can adjust the time-averaged relative speed of the tool with respect to the surface to be machined to 100 m / min or less, and the ultrasonic machining apparatus according to (1), characterized in that the shape of the tool is transferred to the surface to be machined to form a microtexture. (4) The vibration phase angle of the tool can be adjusted within 18 degrees according to the relative position between the surface to be machined and the tool, and the arrangement of the microtexture formed on the surface to be machined can be adjusted to 0 degrees or 180 degrees with respect to the moving direction of the moving mechanism. The ultrasonic machining apparatus according to any one of (1) to (3).

Advantages of the Invention

[0008] One feature of the present invention having such a configuration is to create a microtexture with high efficiency by scanning a cutting tool that ultrasonically vibrates (more than 20,000 times per second) in a plane direction with respect to a surface on which a texture is desired in a single machining apparatus called a machine tool such as a lathe or a milling machine.

[0009] As described above, according to the present invention, it is possible to provide an ultrasonic machining apparatus that can create a microtexture with high creation efficiency without transferring a dedicated machining apparatus.

Brief Description of the Drawings

[0010]

Figure 1

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Figure 8

Mode for Carrying Out the Invention

[0011] Hereinafter, a mode for carrying out the present invention (hereinafter referred to as "this embodiment") will be described in detail with reference to the drawings. Note that the present invention is not limited only to the specific examples described in this embodiment.

[0012] (Ultrasonic machining device) One ultrasonic machining device according to an embodiment of the present invention includes at least an ultrasonic vibrator, a moving mechanism, and a flexible support portion in order to form microtextures on a work surface.

[0013] (Work surface) The object to be processed in this embodiment is any material that can be cut, and the work surface includes the surface of the machined material, that is, a plane or a free-form surface. Specifically, for example, there are a sliding surface machined by milling, a mold, and a cylinder outer peripheral surface and an end surface machined by turning.

[0014] (Microtexture) A microtexture is a fine depression formed on the surface of a workpiece. In this embodiment, it refers to a shape in which the tool tip shape is transferred to the work surface by the tool being pushed into the work surface by a moving mechanism or the like with ultrasonic vibration. For example, the microtexture is formed in the shape illustrated in FIGS. 2 to 6. The pitch interval p of the texture is defined by the following formula.

[0015] p = V / fs Here, fs is the ultrasonic resonance frequency, and V is the moving speed of the moving mechanism.

[0016] The shape and pattern of the microtexture are not limited to those illustrated in FIGS. 2 to 6. For example, p can be reduced by slowing down the moving speed of the moving mechanism or increasing the period of the ultrasonic resonance frequency fs. As a result, if the tool shape is continuously transferred in a continuous form, a groove-shaped microtexture can be formed. Also, a groove-shaped microtexture can be formed in the same manner by reducing the scanning pitch of the moving mechanism.

[0017] (Ultrasonic vibrator) The ultrasonic vibrator has at least an ultrasonic vibrator, a vibration horn, and a tool. In this embodiment, it is preferable that the shape or structural configuration is determined so as to resonate and vibrate at a specific frequency.

[0018] (Ultrasonic vibrator) The ultrasonic vibrator is, for example, one in which a piezoelectric element is sandwiched between electrode plates, and the tip portion thereof is used as an output portion of ultrasonic vibration. In this case, the piezoelectric element operates by applying an alternating voltage in the ultrasonic band to the electrode plates, and ultrasonic vibration is excited. The ultrasonic resonance frequency fs applied to such an ultrasonic vibrator is preferably 20 kHz or more and 30 kHz or less, and more preferably 20 kHz or more and 28 kHz or less. If the ultrasonic resonance frequency fs is less than 20 kHz, it is necessary to extremely slow down the moving speed of the moving mechanism in order to obtain a microtexture with a fine pitch, resulting in a decrease in the creation efficiency.

[0019] (Vibration horn) The vibration horn amplifies the vibration amplitude of the ultrasonic vibrator and also has a function of connecting the ultrasonic vibrator and the tool and transmitting the vibration of the vibrator to the tool.

[0020] (Tool) In this embodiment, the tool refers to a portion or component of the ultrasonic vibrator that interferes with the work material, and the work material is removed or plastically deformed by the interference. Specifically, examples of tools suitable for this embodiment include indenters having a hardness higher than that of the work material.

[0021] The ultrasonic processing apparatus according to this embodiment can transfer the tool shape to the work surface to form a microtexture. Therefore, the texture shape can be determined by the shape of the tool. Also, the total vibration amplitude of the tool is preferably 0.8 μm or more and 25 μm or less, more preferably 0.8 μm or more and 10 μm or less, and most preferably 0.8 μm or more and 3 μm or less along the excitation axis of the ultrasonic vibrator. If the total vibration amplitude is less than 0.8 μm, it becomes impossible to form a microtexture on the surface having a surface roughness Rz of 0.8 μm or more of the work surface, and it becomes impossible to carry out as a post-process of machining.

[0022] (Moving mechanism) In this embodiment, the moving mechanism has a function of enabling adjustment of the relative position of the tool with respect to the work surface. To realize this, the moving mechanism includes at least a drive system that linearly moves or rotates and a detector that reads the relative position. Specifically, as a moving mechanism suitable for this embodiment, for example, a machining center or a lathe can be used.

[0023] The moving mechanism preferably has a function of being able to adjust the time-average relative speed of the tool with respect to the work surface to 100 m / min or less, and more preferably has a function of being able to adjust it to 5 m / min or less. By processing the work surface while pushing the tool into the work surface with this moving mechanism and while the ultrasonic vibrator is excited, a microtexture can be formed on the work surface.

[0024] Furthermore, by making it possible to adjust the vibration phase angle of the tool within 18 degrees according to the relative position between the work surface and the tool, the arrangement of the microtextures formed on the work surface can be adjusted to 0 degrees or 180 degrees with respect to the moving direction of the moving mechanism. The friction coefficient of the work surface can be changed by the arrangement of the microtextures obtained by the linear motion or rotational motion of the moving mechanism in this way.

[0025] The drive system constituting the moving mechanism may be composed of any components as long as it can adjust the relative speed. Also, the detector constituting the moving mechanism may be composed of any components as long as it can detect the time-averaged relative position of the tool with respect to the surface to be machined.

[0026] (Flexible support part) The flexible support part is a member having a function of connecting the ultrasonic vibrator and the moving mechanism. Specifically, it is preferable that the flexible support part of the present embodiment is disposed at a position where the time-averaged machining reaction force due to the machining of the surface to be machined and the time-averaged spring force of the flexible support part are balanced. "Time-averaged" means an average value (hereinafter referred to as "time-averaged value") for a time approximately 10 times or more longer than the natural period of the system composed of the ultrasonic vibrator and the flexible support part. And, the "time-averaged machining reaction force" is the time-averaged value of the impact force generated when the tool vibrating ultrasonically is pushed into the surface to be machined, and the "time-averaged spring force" is the product of the sum of the time-averaged values of the pushing displacement by the moving mechanism and the displacement by the ultrasonic vibration and the spring constant of the flexible support part.

[0027] By providing the flexible support part at such a position, the machining reaction force due to the machining of the surface to be machined is prevented from propagating from the ultrasonic vibrator to the moving mechanism. The spring constant k of the flexible support part of the present embodiment only needs to prevent the machining reaction force from propagating to the moving mechanism, and is preferably 5,000,000 N / m or more to support the self-weight of the ultrasonic vibrator.

[0028] (Low-frequency natural vibration frequency) Here, the low-frequency natural vibration frequency fp will be described. The low-frequency natural vibration frequency fp is defined by the following formula.

[0029] fp = 1 / (2π)√(k / M) Here, k is the spring constant of the flexible support part, and M is the mass of the ultrasonic vibrator.

[0030] In this embodiment, the time-averaged displacement of the ultrasonic vibrator due to the time-averaged machining reaction force needs to be sufficiently smaller than the amplitude of the tool vibrating ultrasonically. Therefore, it is preferable that the low-frequency natural vibration frequency fp of the system consisting of the mass M of the ultrasonic vibrator and the spring constant k of the flexible support portion is 1 / 10 or less of the ultrasonic resonance frequency fs of the ultrasonic vibrator described later. If fp is greater than 1 / 10 of fs, the tool may detach from the work surface, or vibrations at frequencies lower than the ultrasonic vibration, so-called chatter vibrations, may occur, and machining marks due to the ultrasonic vibration cannot be obtained. That the fp is sufficiently smaller than fs means that it is within the range limited by the value of k that can support the mass of the ultrasonic vibrator.

[0031] In this embodiment, it is preferable that fp is 160 Hz or more. If it is less than 160 Hz, a spring constant sufficient to support the mass of the ultrasonic vibrator is not satisfied.

[0032] (Ultrasonic resonance frequency) Here, the ultrasonic resonance frequency fs will be described. The ultrasonic resonance frequency fs generated from the ultrasonic vibrator and the vibration horn is preferably 20 kHz or more and 30 kHz or less, and more preferably 20 kHz or more and 28 kHz or less. If the resonance frequency fs is less than 20 kHz, the ultrasonic range is not reached, and the creation efficiency is significantly reduced. Further, if the resonance frequency fs is greater than 30 kHz, it becomes difficult to form a microtexture at an arbitrary p due to the limitation of the moving speed by the moving mechanism.

[0033] As described above, according to this embodiment, an arbitrary microtexture can be formed on the work surface, and the microtexture can be formed with high creation efficiency compared to the conventional texturing method without transfer, and functionality can be imparted to the material surface, for example, the friction coefficient of the work surface can be changed to a desired value.

Example

[0034] Here, the ultrasonic processing apparatus of the above-described embodiment will be specifically described, and as an example, an example in which a microtexture is actually processed and a change in the coefficient of friction is confirmed will be described.

[0035] In the example, a microtexture was formed using a turning tool that vibrates ultrasonically in the cutting direction. Table 1 shows the processing conditions, and FIGS. 7 and 8 show the processed surface shapes of the comparative example and the example, respectively. In this example, the surface machined under the conditions of the example in Table 1 is denoted as "with texture". In the comparative example, turning was performed with the ultrasonic vibration amplitude set to 0 μm among the processing conditions as shown in Table 1. This processed surface is denoted as "without texture". Comparing the two, the "without texture" of the comparative example has a periodic cusp shape with a pitch interval of 90 μm in the feed direction (FIG. 7). The "with texture" of the example has periodic irregularities with a pitch interval of 40 μm in the cutting direction in addition to the cusp shape in the feed direction (FIG. 8). As a result of performing a ball-on-disk friction test on the processed surface of the example, the average value of the coefficient of friction of "with texture" was reduced by 16% compared to "without texture". p-p As a result of performing a ball-on-disk friction test on the processed surface of the example, the average value of the coefficient of friction of "with texture" was reduced by 16% compared to "without texture".

[0036]

Table 1

Industrial Applicability

[0037] According to the present invention, it becomes possible to create a microtexture with high production efficiency, and the present invention can be applied to many sliding parts.

Explanation of Signs

[0038] 1 Ultrasonic vibrator 1a Ultrasonic vibrator 1b Vibration horn 1c Tool 2 Moving mechanism 3 Flexible support part 10 Workpiece surface 11 Microtexture 11a Texture pitch interval 11b Texture pitch interval 12 Tool vibration locus

Claims

1. An ultrasonic processing device for forming a microtexture on a processing surface, comprising: An ultrasonic vibrator; A moving mechanism; a flexible support portion that connects the ultrasonic vibrator and the moving mechanism, The ultrasonic vibrator has an ultrasonic vibrator, a vibration horn, and a tool, The workpiece surface is machined while the tool is pressed against the workpiece surface by the moving mechanism and the ultrasonic vibrator is excited to vibrate; the flexible support portion is disposed at a position where a time-averaged processing reaction force due to processing of the work surface and a time-averaged spring force of the flexible support portion are balanced; The low-frequency natural frequency fp of a system consisting of the mass m1 of the ultrasonic vibrator and the spring constant k of the flexible support portion is 1 / 10 or less of the ultrasonic resonance frequency fs of the ultrasonic vibrator. An ultrasonic processing device characterized by:

2. The low-frequency natural frequency fp is 160 Hz or more, The ultrasonic resonance frequency fs is 20 kHz or more and 30 kHz or less, 2. The ultrasonic processing device according to claim 1, wherein the spring constant k of the flexible support portion is 5,000,000 N / m or more.

3. The total vibration amplitude of the tool is 0.8 μm or more and 25 μm or less along the excitation axis of the ultrasonic vibrator, The moving mechanism is capable of adjusting a time-averaged relative speed of the tool with respect to the work surface to 100 m / min or less, The shape of the tool is transferred to the workpiece surface to form a microtexture.

2. The ultrasonic processing device according to claim 1 .

4. The vibration phase angle of the tool is adjustable within 18 degrees according to the relative position of the workpiece surface and the tool; The arrangement of the micro-textures formed on the surface to be processed can be adjusted to 0 degrees or 180 degrees with respect to the moving direction of the moving mechanism.

4. The ultrasonic processing device according to claim 1, wherein the ultrasonic processing device is a ultrasonic processing device.

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