JP2003079165A - Manufacturing method for oscillatory wave drive unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a metal elastic body that is one of the components of an oscillatory wave drive unit with accuracy, and especially improve the flatness of the metal elastic body. SOLUTION: Annular metal elastic bodies 1 are sandwiched between flat plates 2 and 3, and are squeezed and molded. At this time, heat is applied. In this method, the deformation resistance of the material is lowered as compared with a method of straightening at room temperature, and spring back is also reduced, which enhance the effect of straightening. Further, residual stress is reduced, and the aged deterioration of the metal elastic body is reduced as well, which enhances the reliability of the oscillatory wave drive unit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses an electro-mechanical energy conversion element as a driving source to generate vibration in a metal elastic body,
The present invention relates to a method of manufacturing a vibration wave driving device in which a driving force is taken out by a moving body that is pressed against the metal elastic body.

[0002]

2. Description of the Related Art Conventionally, as a method of manufacturing a metal elastic body which constitutes a vibrating body in a vibration wave driving device, Japanese Patent Laid-Open No. 09-02
Some are disclosed in Japanese Patent No. 3665. In this method, a powder-sintered molded product is pressed at room temperature for sizing.

[0003]

In this case, the annular metal elastic body that causes bending vibration forms a so-called comb tooth by providing a large number of grooves in the radial direction. Although a metallic elastic body having no comb teeth can be used as a vibration wave driving device, it may not be possible to obtain a vibration displacement of a practically necessary size. When the metal elastic body has the same thickness, the deeper the groove,
That is, the higher the comb tooth, the larger the displacement of the tip of the comb tooth due to the constant deformation of the electromechanical energy conversion element. In reality, the depth of this groove is adjusted to obtain the required force and displacement.

In such a vibration wave driving device, the performance and life of the vibration wave driving device can be stably improved by increasing the dimensional accuracy of the metal elastic body.

In this case, the precision of the metallic elastic body is the variation in the flatness of both end faces and the depth of each groove. The relationship between these and the performance of the vibration wave driving device will be described later.

By the way, the groove is formed by various processing methods. First, there is so-called removal processing for removing the material of the groove portion. For example, cutting such as milling,
Grinding using a grindstone, electric discharge machining, wire cutting, etc. Even in such a processing method, if the material such as a metal round bar has residual stress, the residual stress is often released at the time of groove processing to cause deformation. Hereinafter, a product manufactured by such a processing method is referred to as a removed processed product.

However, if it is attempted to form the groove by cutting or grinding, the processing time becomes extremely long. Therefore, forging molding method, powder sintering molding method, sheet metal press molding method, shell molding method, casting molding method by lost wax method,
It may be molded by a die casting molding method, a metal powder injection sintering molding method, or the like, or may be formed by combining these molding methods. In addition, in the present specification, a product manufactured by these molding methods is referred to as a molded product. The molded product refers to a state before the cutting process or the grinding process which is the subsequent removal process, and hereinafter, the removal processed product and the molded product are collectively referred to as a molded product.

The term "metal elastic body" has a broad meaning including not only molded articles but also those that have been further subjected to cutting, grinding, heat treatment and surface treatment. As the metal elastic body of the vibration wave drive device, the required accuracy is often not obtained only by such a forming process, and therefore, a cutting process, a grinding process, or a lapping process is usually added after the forming process. In particular, the flatness and surface roughness of the attachment surface of the electro-mechanical energy conversion element, the flatness and surface roughness of the end surface of the comb tooth, and the thickness unevenness and parallelism between the comb tooth surface and the attachment surface. In most cases, the above post-processing is added to improve the above.

However, even if such a complicated post-processing is added, the variation in the depth of the groove, that is, the height of the comb teeth cannot be corrected by the post-processing.
This is because, as described above, the molded product or the like is warped. The warpage is displayed as flatness of the attachment surface of the electro-mechanical energy conversion element. As a result of correcting the flatness of both end faces by post-processing such as the above-mentioned grinding process, the depth of the groove on the circumference varies.

The cause of the warpage is largely due to the release of the internal stress of the material in the removal processing as described above. Further, in forging forming and sheet metal press forming, it is largely due to anisotropy of mechanical properties of the material. In casting, unevenness of volume contraction in the process of transformation from metal melt to solid also causes warpage. On the other hand, in powder sinter molding, it may be deformed by its own weight during sintering.

If the groove depth varies, the bending rigidity changes on the circumference, and a difference in displacement occurs at each tip of the comb teeth having the friction member. As a result, the efficiency of transmission of the moving body to the rotational movement is reduced,
Uneven rotation of the moving body may occur. Further, a large load is applied to a specific friction member provided at the tips of the comb teeth, and only the friction member is prematurely worn, and as a result, the life itself of the vibration wave driving device is shortened.

As a means for improving warpage deformation before post-processing, as in the above-mentioned conventional example, a method of pressing the both ends of a powder-sintered molded product with a press machine to correct the flatness, or a sintered product is used. A method is known in which the accuracy is partially corrected by inserting the mold again and pressing it. That is, these are generally called sizing. This method can be said to be a conventional means for improving the dimensional accuracy of a powder sintered product, which is one of the molded products, and many parts have conventionally incorporated this process.

However, since this sizing is performed at room temperature, sufficient correction cannot be often performed due to recovery of elastic strain of the material, that is, a phenomenon usually called springback. Unfortunately, it is easy to select a material having a large elastic limit strain value as the material used for the metal elastic body of the vibration wave driving device. That is,
It is a material that is difficult to correct at room temperature.

The reason why a material having a large elastic limit strain value is selected is related to the vibration damping capability of the vibration wave driving device. A material having a small vibration damping ability is selected for the metal elastic body which is a component of the vibration wave driving device. This is because it is difficult for the vibration to be converted into heat energy inside the metallic elastic body, and a highly efficient vibration driving device can be obtained. Such metals are generally hard. This is because dislocation movement and proliferation, which are one of the causes of the change of vibrational energy into irreversible heat energy, are unlikely to occur. Hard materials, like springs, generally have high elastic limit strain values. In other words, it is difficult to correct a material suitable for the metallic elastic body of the vibration wave driving device at room temperature.

More unfavorably, when sizing at room temperature, residual stress is imparted to a molded product and the like, so that the residual stress is partially removed and deformed in the subsequent cutting and grinding processes. There are many. Alternatively, the step of applying heat to the molded article such as heat treatment may release the residual stress and cause deformation.

If the flatness of the metal elastic body is poor, the following problems occur. First, when the electro-mechanical energy conversion element is bonded to the plane, the electro-mechanical energy conversion element may be damaged. Even if the electro-mechanical energy conversion element can be adhered without being damaged, the electric power may be increased due to a temperature rise due to heat generation during driving of the vibration wave drive device or a decrease in adhesive force in a high humidity environment. -Peeling of the mechanical energy conversion element may occur. As a result, the function itself of the vibration wave drive device is deteriorated, and the reliability is significantly reduced.

Furthermore, when the residual stress still remains in the metallic elastic body, various adverse effects are caused. For example, in the case of a metallic elastic body having a melting point that is not too high, the residual stress may act as a driving force and cause deformation with time due to a kind of creep. Further, when the metal elastic body is made of a material such as brass, it may cause time cracking. Further, austenitic stainless steel and high strength aluminum alloy cause stress corrosion cracking. These are changes with time of the metallic material, and have a direct adverse effect on the performance of the vibration wave driving device.

On the other hand, in the case of a metal elastic body having a comb tooth on the surface and asymmetrical to the front and back, warpage is likely to occur in any of the above-mentioned molded products by any molding method. This is because the molding conditions given to the material in the above-described molding process differ between the front and back of the molded product. In addition to the above-mentioned causes, for example, in the case of forging, since the degree of plastic working of the front comb teeth is higher than that of the back surface, the stress balance between the front and back surfaces collapses,
It transforms into a mortar. Further, in the case of casting and molding, the cooling rate of the comb tooth portion becomes high, and due to the relationship between the deformation resistance of the material and the heat shrinkage, deformation tends to occur when the whole reaches room temperature.

Molded articles having grooves are difficult to straighten at room temperature. The reason is that even if you try to correct a molded product by sandwiching it with two parallel planes, there is a groove in the thickness direction of the molded product, so the strain is small near the surface where the electro-mechanical energy conversion element is attached, and the plastic region This is because it often reaches only a small amount. Therefore, most of them cause springback, and the correction effect is not so remarkable.

In addition, since the deformation resistance of the material is large at room temperature, a large force is required for straightening, and it is also a disadvantage that a large-scale device such as a hydraulic press or a mechanical press is required.

[0021]

In order to solve the above-mentioned problems, it is preferable to correct the warp of the metal elastic body in the molded article and the like so that the residual stress is small, that is, the state is close to the equilibrium state. . As a concrete means, we propose to use a so-called press temper. That is, the flatness of the molded product is corrected while being held at a temperature higher than room temperature. Molded products whose both end surfaces are parallel flat can be corrected with a relatively simple jig.

The reason why the effect of straightening is increased by raising the temperature is that the mechanical properties of the metal material are different at a higher temperature than at room temperature.

More specifically, firstly, there is a decrease in the elastic limit strain of the material. That is, most of the molded products and the like reach the plastic region and the elastically returned strain is reduced by merely giving a displacement such that they are pressed against the flat plate.

Second, the change in work hardening coefficient is increased.
At high temperatures, most metals tend to have less stress increase with increasing strain. With respect to the true stress-true strain curve measured in the material tensile test, the curve tends to be parallel to the strain axis. Due to this tendency, the difference in the stress value generated in each part of the molded product during correction becomes small, the difference in the amount of springback in each part decreases, and as a result the correction effect increases. And, thirdly, it is considered that the diffusion of the element becomes rapid and the creep deformation progresses.

When the second and third phenomena effectively act on the correction of flatness, the magnitude of flatness before correction becomes almost independent of that after correction. In particular, when the diffusion of elements is sufficiently advanced, theoretically the flatness of a molded article or the like follows a flat plate, and there is no residual stress.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION (First Embodiment) FIG. 1 shows a first embodiment. 6 shows a state in which six molded products 1 which are metallic elastic materials are stacked on a flat plate 2 made of stainless steel, and a disc-shaped weight 3 is further placed thereon. Molded product 1
Is a powder sintered product containing iron as a main component. Its shape is Figure 2
Is shown as a perspective view. Since many grooves are cut on one side, warpage is likely to occur during molding.

When powder-sintering, when the compact before sintering is placed on a graphite plate and sintered, the carbon of the graphite plate is likely to diffuse into iron at high temperature. When diffusion occurs, the graphite plate is worn away where it was in contact with the sintered product and the flatness deteriorates. Therefore, it is necessary to frequently control the flatness of the graphite plate.

Since the surface of the powder sintered product is carburized,
The surface is likely to harden, which may affect subsequent cutting and the like. Therefore, boron nitride (BN)
It is convenient to spray such a ceramic powder onto the surface of a graphite plate or a sintered product because diffusion is unlikely to occur. This is because the elemental bond of BN itself is stable even at high temperature, and since the fine particles of BN are sandwiched between irons, it is possible to avoid contact between irons or between iron and a graphite plate.

In the present embodiment, a powder sintered product having a diameter of about 80 mm was used, but the warp was about 0.2 mm in the molded product after powder sintering. It is about 1k at the top as shown in Fig. 1.
A stainless steel weight (g) was placed thereon, and the sample was kept in a reducing furnace at 1060 ° C. for about 30 minutes, and then cooled to room temperature by air cooling.
As a result, even the largest warpage was improved to 0.03 mm. Since the flatness of the flat plate and the weight was about 0.01 mm, it seems that the flatness was corrected in accordance with them. Ten
At 60 ° C, the elastic limit of carbon steel is 1/10 of that at room temperature.
Since it becomes the following, it seems that the molded product was sufficiently adhered to the surface of the graphite plate. Conversely, the thickness of the molded product was also measured,
Crushing did not occur even in the lowermost molded article, which was the most loaded.

Since BN was applied to the surface of the powder sintered product, the stainless weight and the stainless flat plate this time, there was no sticking between the molded products. As the material of the flat plate,
In addition to stainless steel, which is a kind of inexpensive heat-resistant alloy, graphite, alumina, silicon nitride, or Ni-based heat-resistant alloy such as Inconel or Hastelloy is suitable. However, since it is exposed to the temperature at the time of straightening many times, it is desirable to grind the flat surface of the flat plate after releasing the internal stress at that temperature or higher in advance.

The BN powder on the surface is removed by shot blasting with a steel ball. Originally, powder sinter products were blasted for the purpose of removing burrs and foreign substances, so that no extra man-hours were required. In addition to the blasting treatment, barrel polishing treatment may be performed. On the other hand, when the surface of the sintered product was not subjected to any treatment, it was also tested. As a result, sticking occurred in some parts, and it was necessary to separate the sintered products from each other.

Although the temperature of 1060 ° C. is lower than the sintering temperature, it may be corrected at the same temperature as the sintering temperature. Then, the sintering furnace can be used as it is, and it is not necessary to introduce new equipment.

Further, since the correction is performed at a temperature below the sintering temperature, there is almost no change in the metal structure. Therefore, the mechanical
Since there is no change in chemical or physical properties, there is no need to perform heat treatment again.

In powder sinter molding, the flatness of parts often varies widely. This is partly due to the large number of molding steps.

Therefore, if the straightening method as carried out here is adopted, it is possible to select and repair the sintered products whose flatness exceeds the standard value. In particular, a large number of thin-walled parts can be processed by stacking them because both end surfaces are parallel. FIG. 5 shows a state in which the case is opened in the vibration wave driving device using the metal elastic body manufactured in this way.

(Second Embodiment) FIG. 3 shows a second embodiment. An alumina ceramic plate 5 is inserted between the molded products 1. In the first embodiment, the BN powder was applied to the surface of the molded product 1. However, when a large amount of treatment is performed, it is more efficient to repeatedly use the ceramic plate, although the initial investment is large, but it is more efficient.

(Third Embodiment) FIG. 4 shows a third embodiment.

In the present embodiment, as shown in FIG. 4, a coil spring 8 is passed through a disk washer 3, a flat plate 2 and a molded product 1 and a bolt 5 fastened by a nut 7 through a flat washer 6 and a flat washer 6.
And the coil spring 8 is used to apply a pressing force to the molded product.

In this embodiment, as will be described later, since the heating temperature is relatively low, a large force is required for pressing pressure. Therefore, if the weight is used as in the first and second embodiments, the work efficiency is not good, so the coil spring 8 is used. The spring 8 may be a disc spring or a leaf spring. Further, the material of the spring is stainless steel, but if a heat-resistant metal material such as Inconel or a ceramic material such as silicon nitride is used, the material will not be plastically deformed even at a temperature of 550 ° C. or higher described below and can be repeatedly used. It can be used.

As a corrosion-resistant treatment for iron-made sintered products, steam rust prevention treatment is often performed. This is a treatment in which an iron-made sintered product is placed in steam at about 550 ° C and an oxide film is formed on the surface thereof. This oxide film is ferrosoferric oxide or magnetite. It is also called so-called black rust, and since it is a relatively dense film, it has a corrosion resistance effect. This is an effective means for a porous product such as a sintered product having a large actual surface because a film is formed even inside the pores.

In the present embodiment, straightening was attempted at 550 ° C., which is the temperature reached by the sintered product in this treatment. 550 ° C for carbon steel
Since the elastic limit is about 1/3 of that at room temperature, the straightening effect is small compared to around 1000 ° C, but jigs do not require particularly excellent heat resistance, and stainless steel is sufficient.

Further, both end faces of the sintered product are removed by a later grinding process, and the piezoelectric element and the friction material are adhered to the end faces, so that it is necessary that the above-mentioned oxide film is formed on both end faces. Absent. Therefore, as shown in FIG. 4, there is no problem even if the rustproof treatment is performed while the sintered products are in close contact with each other.

Further, at a temperature of 550 ° C., since the diffusion is small, it is difficult for the sintered products to adhere to each other. Since a kind of heat application process called rust prevention treatment was also used for straightening, it does not increase special man-hours.

(Fourth Embodiment) The fourth embodiment has the same configuration as that of the third embodiment. However,
The metal elastic body is formed by pressing a JIS standard aluminum alloy 2218. After press working, this is subjected to solution treatment at 510 ° C. and then arranged as shown in FIG. 200 this
Place in an electric furnace at ℃ and age for 1 hour in air. Of course, it may take 5 to 10 hours at a temperature of about 170 ° C.

This is a method of straightening by utilizing the artificial age hardening process of the aluminum alloy as it is. The material used for the metal elastic body is not only duralumin as in the embodiment but also J
It may be an IS standard 6000 series aluminum alloy or the like. Further, beryllium copper, high speed steel, precipitation hardening stainless steel, austenitic stainless steel and the like are suitable.

These are materials that can be hardened by raising the temperature and utilizing precipitation hardening and strain age hardening. The process of raising the temperature can be used for correction. In the precipitation hardening process and strain aging process in which the diffusion of elements occurs, if the process is passed through while being straightened, residual stress is also reduced and strain is unlikely to occur in the subsequent cutting process.

Further, the structure shown in FIG. 4 may be used in the solution treatment step. That is, in the example of the aluminum alloy described above, the temperature is raised to 510 ° C. while being pressed by a spring to correct the flatness, and the water is cooled as it is. After that, artificial aging increases the hardness.

The above steps are desirable because the hardness of the final material does not decrease.

(Fifth Embodiment) The fifth embodiment also
The configuration is the same as that of the third embodiment. For the metal elastic body, a hollow bar of martensitic stainless steel was cut into a ring shape, and then its cross-sectional shape was crushed into a trapezoid by forging.

After fixing the back side with an electromagnetic chuck,
A large number of grooves were formed on the surface of the thin disc-shaped grindstone. This was heated to 1050 ° C. in vacuum, cooled with nitrogen gas, and quenched. An iron alloy containing an element having a high ability to form a carbide such as chromium can sufficiently undergo martensitic transformation and increase in hardness even if the cooling rate is low. Therefore, a high cooling rate such as water cooling or oil cooling is not necessary. During the martensitic transformation, the volume of the metal expands by several percent, so deformation often occurs due to the nonuniformity. However, if the front and back surfaces of the metal elastic body are restrained as in this embodiment, the deformation can be suppressed.

In order to recover the toughness of an iron-based material that has normally been quenched, it is tempered after quenching.

A tempering temperature of 150 to 550 ° C. is then selected, depending on the mechanical properties required of the material. In this tempering step, the front and back surfaces of the metal elastic body may be constrained.

As described above, if the hardening or tempering process of the iron-based material is used as it is for straightening, the flatness of the front and back surfaces is improved and the subsequent lapping time is greatly shortened. Further, as a result of the variation in the depth being reduced by each groove, the performance as the vibration wave driving device is also improved.

[0054]

As described above, according to the present invention, the mechanical properties of the material at room temperature change if the temperature is raised while the flat surface of the molded article or the like that becomes the metal elastic body is corrected. The so-called springback amount becomes small, and the difference in the amount becomes small in each part such as the molded product, so that the correction effect is increased.

Compared to the case of sizing at room temperature,
The flatness is remarkably improved.

Since the residual stress of the molded product is also reduced,
Deformation is less likely to occur in subsequent cutting or grinding.

As a result, when this molded product or the like is used as a metal elastic body of a vibration wave driving device, variations in vibration displacement on the circumference are reduced. As a result, uneven rotation is small,
A vibration wave driving device with high efficiency and long life can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

2 is a perspective view of the elastic metal body of FIG.

FIG. 3 is a diagram showing a second embodiment of the present invention.

FIG. 4 is a diagram showing third and fourth embodiments of the present invention.

FIG. 5 is a diagram showing a vibration wave driving device manufactured by the manufacturing method of the present invention.

[Explanation of symbols]

1… Molded product or metal elastic body 2 ... Heat-resistant flat substrate 3 ... Flat weight 4 ... Heat-resistant flat plate 5 ... bolt 6 ... Plain washer 7 ... nuts 8 ... spring 9 ... Electric-mechanical energy conversion element 10 ... Mobile 11 ... Friction material 12 ... Output shaft 13, 14 ... Bearings 15 ... Case

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 5H680 AA12 BB01 BB16 BC01 CC01                       DD02 DD13 DD23 DD53 DD65                       DD66 DD74 DD85 DD92 EE03                       FF04 GG11

Claims (23)

[Claims] 1. A method of manufacturing a vibration wave driving device for correcting a molded product of the metal elastic body in a vibration wave driving device having a vibration body for exciting an annular metal elastic body by an electro-mechanical energy conversion element, The method for manufacturing an oscillatory wave drive device, wherein the metallic elastic body is pressed at a temperature exceeding room temperature during pressing to press both end surfaces of the ring with flat plates. 2. A vibration wave for correcting a molded article of the metal elastic body in a vibration wave driving device having a vibrating body which excites a metal elastic body having an annular shape and a large number of grooves on one surface thereof by an electromechanical energy conversion element. The method for manufacturing a driving device according to claim 1, wherein the metal elastic body has a temperature above room temperature during pressing and presses both end faces of the ring with flat plates. 3. A molding of the metal elastic body in a vibration wave driving device having a vibrating body which excites by a electro-mechanical energy conversion element a metal elastic body which is formed by molding and has a large number of grooves on one surface thereof. In the method of manufacturing a vibration wave driving device for straightening an article, the molded metal elastic body has a temperature exceeding room temperature during straightening and presses both end faces of the ring with flat plates to drive the vibration wave. Device manufacturing method. 4. The method for manufacturing a vibration wave driving device according to claim 1, wherein the pressing means is a spring. 5. The reaction force generated by the spring is received by a member penetrating an inner diameter portion of the annular ring.
A method for manufacturing a vibration drive device according to item 1. 6. The method for manufacturing an oscillatory wave drive device according to claim 4, wherein the spring is made of ceramic. 7. The method of manufacturing an oscillatory wave drive device according to claim 4, wherein the spring is a coil spring. 8. The method for manufacturing a vibration wave driving device according to claim 1, wherein the pressing means is a weight. 9. The method for manufacturing an oscillatory wave drive device according to claim 1, wherein the flat plate is a graphite plate, a ceramic plate, or a heat-resistant alloy. 10. The method of manufacturing a vibration wave driving device according to claim 1, wherein a plurality of the annular metal elastic bodies are stacked and pressed. 11. The method of manufacturing a vibration wave driving device according to claim 1, wherein inorganic particles are applied to the surface of the metal elastic body. 12. The method for manufacturing a vibration wave driving device according to claim 11, wherein the inorganic particles are boron nitride. 13. The method for manufacturing a vibration wave driving device according to claim 10, wherein a flat plate is arranged between the plurality of metal elastic bodies that are stacked. 14. The method of manufacturing an oscillatory wave driving device according to claim 13, wherein the flat plate is a graphite plate or a ceramic plate. 15. The method for manufacturing a vibration wave driving device according to claim 1, wherein inorganic particles are applied to the surface of the flat plate or the weight. 16. The method for manufacturing a vibration wave driving device according to claim 15, wherein the inorganic particles are boron nitride. 17. The method according to claim 11, 12, 15 or 16, wherein the inorganic particles coated on the metallic elastic body are removed by shot blasting or barrel treatment. 18. The thickness of the metal elastic body is not changed even after the metal elastic body is pressed and then a temperature exceeding room temperature is applied. Method for manufacturing vibration wave drive device. 19. The temperature above room temperature is the temperature at which the material of the metal elastic body is formed by powder sintering and is the sintering temperature. A method for manufacturing the vibration wave driving device described. 20. The temperature above room temperature is a metal whose material of the metal elastic body age-hardens by heat treatment, and is the heat treatment temperature.
3. The method for manufacturing an oscillatory wave drive device as described in 3. 21. The temperature above room temperature is a temperature at which the material of the metal elastic body is solution-treated, or a quenching temperature for producing martensite.
4. A method for manufacturing an oscillatory wave drive device according to 1, 2, or 3. 22. The method for manufacturing a vibration wave driving device according to claim 1, wherein the temperature exceeding the room temperature is a temperature at which the iron-based material is tempered. 23. The method for manufacturing a vibration wave driving device according to claim 1, wherein the temperature exceeding the room temperature is a temperature at which the iron-based powder sintered material is subjected to steam rust prevention treatment. .