JP6938218B2 - Friction material, method of manufacturing friction material, vibration type actuator and electronic equipment - Google Patents

Description

The present invention relates to a friction material that comes into contact with a mating material, a method for producing the friction material, a vibration type actuator using the friction material, and an electronic device.

The vibrating body and the driven body are brought into pressure contact with the vibrating body provided with the electric-mechanical energy conversion element, and a predetermined vibration is excited by the vibrating body to give a friction driving force from the vibrating body to the driven body. A vibrating actuator that moves relative to a driving body is known. For example, since the rotary drive type vibrating actuator has a large holding torque (the linear drive type vibrating actuator has a large holding force), the position of the vibrating body and the driven body in a non-energized state even when an external force is applied. The relationship can be maintained. That is, immediately after driving the vibrating actuator, a holding torque or holding force equivalent to the maximum generated torque generated during driving can be obtained.

However, the vibrating actuator has a problem that when it is left under high humidity, moisture is adsorbed on the friction surface (friction sliding surface), so that the holding torque or the holding force is lowered at the time of subsequent start-up. As a technique for solving this problem, Patent Document 1 describes a technique for nitriding a surface layer portion of a stainless steel friction material in which a titanium charcoal sulfide phase is dispersed. Specifically, the titanium nitride phase and the like are dispersed by subjecting a stainless steel material in which the titanium charcoal sulfide phase is dispersed to a nitriding treatment such as ion nitriding to change the titanium carbonitride phase on the surface layer to the titanium nitride phase and the like. A hardened layer is formed. Since the titanium nitride phase is hard and hard to wear, fine protrusions are formed on the friction surface due to frictional wear, and even if water is adsorbed on the friction surface, the protrusions break through the water film to secure the true contact part. Will be done. As a result, it is possible to suppress a decrease in holding torque or holding force after being left in high humidity.

Japanese Patent No. 5236160

However, in the technique described in Patent Document 1, hard particles such as the titanium nitride phase bite into the mating material, resulting in elastic wear that generates a friction driving force. Therefore, when trying to obtain a large holding torque or holding force, there arises a problem that the amount of wear of the mating material increases.

Further, the friction material used for the vibration type actuator is required to have various characteristics in addition to the friction characteristics with respect to humidity. For example, wear resistance according to the application of the vibrating actuator, the degree of change in frictional force with the progress of wear, constant frictional force can be obtained regardless of the relative position of the driven body and the vibrating body, and further. Characteristics such as less scattering of abrasion powder are required. By the way, in the technique described in Patent Document 1, the particle size, amount, morphology, dispersion state, etc. of titanium nitride or the like depend on the titanium charcoal sulfide crystallized in the steel material before the nitriding treatment. Therefore, it is not easy to freely design and control the state and characteristics of the friction surface when producing a friction material for a vibration type actuator by nitriding treatment.

Further, it is desired that the vibrating body used in the vibrating actuator is provided with the friction material only in a necessary region in order to prevent not only the friction characteristics but also the vibration damping due to the friction material as much as possible. Correspondingly, when a joining method such as bonding, welding, or brazing is used, the vibration characteristics may become unstable due to poor joining or uneven joining.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to suppress wear of the mating material, suppress a decrease in holding torque or holding force due to the influence of humidity, and further, a vibrating actuator that does not impair the characteristics according to the application. The purpose is to provide.

The vibrating actuator according to the present invention includes a vibrating body having an electro-mechanical energy conversion element and an elastic body, and a contact body that comes into pressure contact with the vibrating body, and the vibrating body is generated by vibration excited by the vibrating body. and said contact body a vibration-type actuator for relatively moving the, the second contact portion for contacting with the vibration member at a first contact portion or the contact body in contact with the contact member in the vibrator at least one comprises a stainless steel sintered body having pores, a part of the pores of the resin is impregnated, the resin is exposed on the surface of the stainless steel sintered body, the other part is the surface of the pores It is characterized by being exposed.

According to the present invention, it is possible to suppress the wear of the mating material, suppress the decrease in the holding torque or the holding force due to the influence of humidity, and further, the vibration without impairing the characteristics according to the application. A type actuator can be realized.

It is a figure for demonstrating the schematic structure of the 1st vibration type actuator. It is a figure for demonstrating the schematic structure of the 1st vibration type actuator. It is a figure for demonstrating the schematic structure of the 1st vibration type actuator. It is a figure for demonstrating the schematic structure of the 1st vibration type actuator. It is a figure for demonstrating the schematic structure of the protrusion having contact (friction part) containing a stainless sintered body. It is a figure for demonstrating the schematic structure of the protrusion having contact (friction part) containing a stainless sintered body. It is a figure for demonstrating the schematic structure of the 2nd vibration type actuator. It is a figure for demonstrating the schematic structure of the 2nd vibration type actuator. It is a figure for demonstrating the schematic structure of the 2nd vibration type actuator. It is a figure for demonstrating the schematic structure of the modification of the 2nd vibration type actuator. It is a figure for demonstrating the schematic structure of the modification of the 2nd vibration type actuator. It is a process drawing for schematically explaining the 2nd manufacturing method of the driven body. It is a photograph showing the microstructure near the boundary between the friction part and the polished surface of the main body part after the smoothing treatment. It is a process drawing for schematically explaining the 3rd manufacturing method of the driven body. It is sectional drawing explaining the schematic structure of the 3rd vibration type actuator. It is an exploded sectional view of the 3rd vibration type actuator. It is a figure for demonstrating the friction part provided in the vibrating body which the 3rd vibrating type actuator has. It is a figure for demonstrating the friction part provided in the vibrating body which the 3rd vibrating type actuator has. It is a figure for demonstrating the vibrating body which constitutes the 4th vibration type actuator. It is a figure for demonstrating the vibrating body which constitutes the 4th vibration type actuator. It is a figure for demonstrating the vibrating body which constitutes the 4th vibration type actuator. It is a figure for demonstrating the vibrating body which constitutes the 4th vibration type actuator. It is an electron micrograph which shows the state of the friction surface of the friction part of the driven body of Example 3. FIG. It is a figure which shows the measurement result of the holding torque of the vibrating type actuator of Examples 1 to 3 and Comparative Example 1. It is a figure which shows the measurement result of the holding torque of the vibrating type actuator of Examples 4-6 and Comparative Example 2. It is an electron micrograph which shows the state of the friction surface of the friction part before the reciprocating drive of Example 5. FIG. It is a micrograph which shows the state of the friction surface of Example 5 after the reciprocating drive of 70,000 times is completed. It is an electron micrograph which shows the state of the friction surface of the friction part before the reciprocating drive of Example 6. It is a figure for exemplifying the manufacturing method of the friction material using a mold. It is a figure for exemplifying another manufacturing method of the friction test pin on which the friction material was formed. It is a perspective view which shows the schematic structure of the robot equipped with the vibration type actuator. It is a perspective view which shows the schematic structure of the lens drive mechanism provided in the lens barrel.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. First, a configuration example of the first vibration type actuator according to the embodiment of the present invention will be described. 1A to 1C are views for explaining a schematic configuration of the first vibrating actuator 10, and FIG. 1A is a perspective view showing a schematic configuration of the vibrating actuator 10. The vibrating actuator 10 includes a driven body 1 and a vibrating body 2. The vibrating body 2 includes a substantially rectangular flat plate-shaped elastic body 2b as a base material, a substantially flat plate-shaped piezoelectric element 2c bonded to one surface of the elastic body 2b with an adhesive or the like, and a piezoelectric element 2c in the elastic body 2b. It has two protrusions 2a provided on the surface opposite to the surface to which the is joined.

For convenience of explanation, as shown in FIG. 1A, the X-axis, Y-axis, and Z-axis that are orthogonal to each other are defined. The X-axis direction is a direction connecting the two protrusions 2a, and is a relative moving direction of the driven body 1 and the vibrating body 2 as described later. The Z-axis direction is the thickness direction of the elastic body 2b and the protruding direction of the protrusion 2a. The Y-axis direction is a direction orthogonal to both the X-axis and the Z-axis, and is the width direction of the elastic body 2b. The driven body 1 is in pressure contact with two protrusions 2a in the Z-axis direction by a pressure means (not shown). Hereinafter, the portion of the vibrating body 2 that comes into contact with the driven body 1 (contact body) is referred to as the first contact portion, and the portion of the driven body 1 that comes into contact with the first contact portion of the vibrating body 2 is referred to as the second contact portion. do. In the vibrating actuator 10, for example, the driven body 1 and the vibrating body 2 are brought together by causing an elliptical motion in the plane including the X-axis direction and the Z-axis direction (in the ZX plane) at the tip of the protrusion 2a. It can be moved relatively in the X-axis direction.

FIG. 1B is a plan view showing the electrode structure of the piezoelectric element 2c. The piezoelectric element 2c, which is an example of the electric-mechanical energy conversion element, has an electrode region divided into two equal parts in the X-axis direction, and the polarization directions in each electrode region are the same direction (+). For example, alternating voltages VA and VB having frequencies close to the resonance frequencies of the out-of-plane primary bending vibration mode and the out-of-plane secondary bending vibration mode are applied to the two electrodes of the piezoelectric element 2c as shown in FIG. 1B. As a result, the vibration in the out-of-plane primary bending vibration mode and the vibration in the out-of-plane secondary bending vibration mode are combined to generate an elliptical motion in the ZX plane on the protrusion 2a, and this elliptical motion causes the driven body. 1 and the vibrating body 2 can be relatively moved in the X-axis direction.

The out-of-plane primary bending vibration mode is bending vibration in the Y-axis direction, and is a vibration mode in which two nodes appear substantially parallel to the X-axis direction on the vibrating body 2. The out-of-plane secondary bending vibration mode is bending vibration in the X-axis direction, and is a vibration mode in which three nodes are generated in the vibrating body 2 substantially parallel to the Y-axis direction. The two protrusions 2a are provided at a position that is an antinode of the vibration in the out-of-plane primary bending vibration mode and a position that is an antinode of the vibration in the out-of-plane secondary bending vibration mode. Since the principle of causing the protrusion 2a of the vibrating body 2 to generate an elliptical motion in the ZX plane in this way is well known, a more detailed description thereof will be omitted.

FIG. 1C is a perspective view showing a schematic configuration of the driven body 1. The square rod-shaped driven body 1 is made of a stainless sintered body obtained by sintering stainless powder so as to have a constant porosity, and one XY surface of the driven body 1 is in pressure contact with the protrusion 2a. It is a contact portion (friction surface, friction sliding surface) of 2. In the driven body 1, for example, stainless powder is molded into a square bar shape by a well-known molding method, the molded body is sintered in a non-oxidizing atmosphere such as a vacuum atmosphere, and at least the friction surface of the obtained sintered body is polished ( It is manufactured by grinding) processing. As the stainless steel powder, for example, SUS420j2 powder defined by JIS standard (for example, an average particle size of about 10 μm) can be used. As the sintering conditions in this case, for example, a process of quenching after performing a sintering process of holding in a vacuum atmosphere at 1100 ° C. for 30 minutes can be used. When the SUS420j2 sintered body is produced, the sintered body can be cured by quenching through a quenching treatment from the sintering temperature. As a result, the wear resistance of the driven body 1 made of the SUS420j2 sintered body can be improved, and the durability of the vibrating actuator 10 can be improved. In order to obtain this effect, it is desirable that the Vickers hardness of the SUS420j2 sintered body is 600 HV or more.

The stainless steel sintered body, which is the driven body 1, has a certain amount of pores. Therefore, even if the vibrating actuator 10 is left in a high humidity environment and water (water molecules) adheres to the second contact portion (friction surface) of the driven body 1, the pores serve as a place for removing water. Therefore, the true contact portion between the protrusion 2a and the driven body 1 can be easily secured. As a result, it is possible to suppress a decrease in the holding force of the vibration type actuator 10. Further, the driven body 1 promotes wear of the protrusion 2a, which is the mating material, unlike the friction material that generates a friction driving force by the hard particles biting into the mating material as described in the prior art. There is no. When the average value of the ratio of pores in the range of contact with the protrusion 2a (hereinafter referred to as "surface porosity") on the friction surface of the stainless sintered body is about 5 to 40%, the holding torque or holding force decreases. Has been confirmed to have the effect of reducing. In particular, from the viewpoint of wear resistance, it is desirable that the average value of the surface porosity is around 10%. The surface porosity can be measured, for example, by capturing the surface of the friction surface as an image in image processing software using a microscope. Since the friction surface of the stainless steel sintered body is gradually worn, the surface porosity is almost the same if the wear is slight, but it is desirable that the surface porosity is as described above even after the wear.

The above-mentioned effect is not limited to the case where the driven body 1 is made of a SUS420j2 sintered body, and can also be obtained when the driven body 1 is made of another stainless steel material sintered body. Since the pores existing in the driven body 1 serve as a place for absorbing (adsorbing) wear debris, it is possible to suppress a change in drive performance by suppressing the accumulation of wear debris on the friction surface. At the same time, it is possible to avoid the occurrence of problems such as spoiling the aesthetic appearance due to the scattering of wear debris. Further, by suppressing the scattering of the wear debris to the outside, it is possible to suppress the influence of the wear debris on various devices such as electronic devices equipped with the vibration type actuator 10.

FIG. 1D is a perspective view showing a schematic configuration of a modified example of the driven body 1. A modified example of the driven body 1 has a main body portion 1b which is a base material and a friction portion 1a provided on the main body portion 1b. The friction portion 1a is a second contact portion that comes into contact with the protrusion 2a of the vibrating body 2, and is a portion that frictionally slides with the protrusion 2a of the vibrating body 2 when the vibrating actuator 10 is driven. The friction portion 1a includes a stainless steel sintered body and has pores (vacancy). Since these pores serve as a place for removing water, it becomes easy to secure a true contact portion between the protrusion 2a and the friction portion 1a. As a result, it is possible to suppress a decrease in the holding force of the vibration type actuator 10. Further, since the pores existing in the friction portion 1a serve as a place for absorbing (adsorbing) wear debris, the drive performance is changed by suppressing the accumulation of wear debris on the friction surface (friction sliding surface). Can be suppressed. Further, by suppressing the scattering of the wear debris to the outside, it is possible to suppress the influence of the wear debris on various devices such as electronic devices equipped with a vibrating actuator. In addition, the friction portion 1a promotes wear of the protrusion 2a, which is the mating material, unlike the friction material that generates a friction driving force by the hard particles biting into the mating material as described in the prior art. It won't go away.

A method of forming the friction portion 1a on the main body portion 1b will be described. First, a slurry (paste) in which stainless steel powder is dispersed is applied onto one surface of a main body 1b made of a square bar-shaped stainless steel material by a screen printing method or the like to spread the stainless powder on the main body 1b. Mold. Subsequently, the slurry coating portion (molded portion of stainless steel powder) and the main body portion 1b are integrally heated to a predetermined temperature and fired to sinter the molded stainless powder. As a result, it is possible to obtain a driven body 1 in which the friction portion 1a, which is a stainless steel sintered body, and the square rod-shaped main body portion 1b are directly bonded by integral sintering. The fact that the friction portion 1a and the main body portion 1b are directly bonded means that they are bonded without using another material such as an adhesive or a brazing material.

Further, a stainless steel material such as SUS304 is used for the main body portion 1b, and SUS420j2 powder having an average particle size of about 10 μm can be used as the stainless steel powder used as a raw material for the friction portion 1a. The sintering conditions in this case are the same as the above-mentioned sintering conditions for the driven body 1.

A stainless steel sintered body may be used for the driven body 1 and its friction portion 1a, or instead, a stainless steel sintered body may be provided at the first contact portion of the protrusion 2a to form a friction surface. 2A and 2B are diagrams for explaining a schematic configuration of a protrusion 2a having a friction portion (first contact portion) 2aa made of a stainless steel sintered body. FIG. 2A is a perspective view showing a schematic configuration of a protrusion 2a having a friction portion 2aa, and FIG. 2B is a cross-sectional view showing a schematic configuration of the protrusion 2a having a friction portion 2aa. For the elastic body 2b, for example, a plate-shaped stainless steel material such as SUS420j2 is press-processed to integrally form a protrusion 2a on the elastic body 2b, and a recess is formed in the center of the tip of the protrusion 2a. Can be used. A friction portion 2aa having a structure (microstructure) equivalent to that of the friction portion 1a is provided in the recess of the protrusion 2a, and the friction portion 2aa is formed by, for example, integrally sintering with an elastic body 2b. The surface of the friction portion 2aa is formed in a substantially spherical shape, whereby the contact position with the driven body 1 can be defined, and the surface formed with the progress of wear of the friction portion 2aa is circular. Can be maintained at. As a result, the performance of the vibration type actuator 10 can be stabilized.

Next, the configuration of the second vibration type actuator in which the friction material according to the embodiment of the present invention is used will be described. 3A to 3C are views for explaining a schematic configuration of the second vibration type actuator 20, and FIG. 3A is an exploded perspective view of the vibration type actuator 20. The vibrating actuator 20 includes a ring-shaped driven body 5 and three vibrating bodies 2. Each of the three vibrating bodies 2 is arranged on a base (not shown) so that the direction connecting the two protrusions 2a is the tangential direction of a circle concentric with the inner or outer circumference of the driven body 5. The driven body 5 can be rotated in the circumferential direction thereof. The tip of the protrusion 2a of the vibrating body 2 and one surface (friction surface 5d (see FIG. 3B)) substantially parallel to the radial direction of the driven body 5 are in pressure contact with each other by a pressurizing means (not shown). ing. After arranging three vibrating bodies 2 having the same specifications, various outer diameters and inner diameters can be obtained by changing the sizes (shapes) of the base on which each vibrating body 2 is arranged and the driven body 5. A vibrating actuator can be manufactured.

The driven body 5 is made of, for example, a sintered body of SUS316 powder, which is a kind of austenitic stainless steel, and a nitride layer is provided on the friction surface 5d of the second contact portion in contact with the vibrating body 2 and impregnated with resin. Has been done. FIG. 3B is a diagram schematically showing a manufacturing process of the driven body 5. The SUS316 powder is formed into an annular shape using a well-known molding method and sintered under predetermined conditions to prepare a sintered body 5a having an average particle size of, for example, about 75 μm. After the shape of the sintered body 5a is adjusted by cutting, one surface of the sintered body 5a that is substantially parallel to the radial direction is subjected to a hardening treatment to improve wear resistance. Specifically, the nitrided layer 5b is provided by the ion nitriding method. Further, a liquid epoxy resin 5c is applied to the surface of the nitrided layer 5b, and the sintered body 5a is held at 50 ° C. to reduce the viscosity of the epoxy resin and impregnate the pores of the nitrided layer 5b. This impregnation treatment may be performed in a vacuum atmosphere. As a result, the impregnation of the epoxy resin 5c into the pores can be promoted. Then, the epoxy resin 5c is cured by, for example, holding the sintered body 5a at 80 ° C. for 1 hour. Subsequently, the resin cured portion on the nitrided layer 5b is removed by using, for example, GC # 320 emery paper, and then polishing using a copper surface plate and polycrystalline diamond (average particle size: 3 μm). Processing (wrapping) is performed to form a smoothed friction surface 5d. As a result, the driven body 5 is obtained.

In the vibrating actuator 20, in order to deposit abrasion powder inside the pores, it is desirable that all the pores of the driven body 5 are not impregnated with the resin, but some of the pores remain. Such resin impregnation of the driven body 5 can be similarly applied to the driven body 1 described with reference to FIG. Further, depending on the characteristics required for the driven body 5, a ceramic powder such as green carborundum (GC) or white random ceramic powder (WA) may be mixed in the liquid epoxy resin. The type, particle size, grain morphology, amount, etc. of the ceramic powder to be added shall be appropriately adjusted according to the characteristics required for the driven body 5 in consideration of the porosity, pore size, etc. of the sintered body 5a. Can be done. Further, the impregnation treatment may be performed using an acrylic resin instead of the epoxy resin.

The stainless steel material used for the driven body 5 is not limited to austenitic stainless steel, and may be a ring-shaped sintered body of martensitic stainless steel such as SUS420j2. When a sintered body of SUS420j2 powder is used as the driven body 5, quenching can be performed to increase the hardness by performing quenching treatment after holding the sintered body at the sintering temperature for a predetermined time. Durability) can be improved. However, in light of the object of the present invention of suppressing a decrease in holding torque or holding force due to the influence of humidity, it is not essential that the friction surface 5d of the driven body 5 is a surface that has been hardened, and nitriding. It is also not essential that the layer 5b is impregnated with resin. FIG. 3C is a diagram schematically showing a manufacturing process of the driven body 5 when the nitrided layer is not provided. When a sintered body of SUS420j2 powder is used for the driven body 5, the hardness can be increased by quenching, so that the nitrided layer is not essential. On the other hand, it is desirable that the friction surface 5d is a surface that has been hardened and impregnated with a resin so that the property of increasing wear resistance (improving durability) can be obtained. ..

3D and 3E are diagrams for explaining a schematic configuration of a modified example of the second vibration type actuator.

FIG. 3D is a perspective view of the driven body 5 of the modified example of the second vibration type actuator. FIG. 3E is a cross-sectional view including the thrust axis of the driven body 5, and shows only one of the two appearing cross sections. The driven body 5 has a friction portion 5aa as a second contact portion and a main body portion 5bb which is a base material. The friction portion 5aa is in pressure contact with the protrusion 2a of the vibrating body 2, and when the vibrating actuator is driven, the friction driving force due to the elliptical motion excited by the protrusion 2a is received. The friction portion 5aa is arranged so as to be embedded in an annular recess (groove) provided in the main body portion 5bb.

The first manufacturing method of the driven body 5 will be described. First, a main body portion 5bb made of SUS316, having a convex portion 5b2 formed on one surface and a concave portion 5b1 formed on the convex portion 5b2 is prepared. The method for producing the main body 5bb is not limited to this. Specifically, a mixed powder is prepared by mixing 2% by weight of copper powder (average particle size: 10 μm) with SUS316 powder (water atomized powder having an average particle size of 10 μm). Next, the mixed powder is filled in the recess 5b1 and ^{molded by applying a pressure of about 50 MPa (1.5 tons / 300 mm 2} ) for a predetermined time using a tubular punch (pressurizing member), and then integrated with the main body 5bb. Then, in a vacuum atmosphere, the mixture is held at 1100 ° C. for 1 hour and rapidly cooled with nitrogen gas. As a result, a stainless steel sintered body firmly bonded to the main body portion 5bb is formed.

It is desirable that the friction portion 5aa has high wear resistance. Here, SUS316 is an austenitic stainless steel, and in the austenitic stainless steel, a curing method using martensitic transformation cannot be adopted. Therefore, after cutting the upper surface of the stainless steel sintered body together with the convex portion 5b2, a nitride layer is formed on the surface of the stainless steel sintered body by the ion nitriding method. Finally, using a well-known lapping device having a copper surface plate and polycrystalline diamond powder (average particle size: 3 μm), the surface of the nitride layer is smoothed together with the surface of the convex portion 5b2. As a result, the upper surface of the convex portion 5b2 and the friction portion 5aa are flush with each other. In the smoothing treatment, only the sintered body and the convex portion 5b2 protruding from the main body portion 1b need to be smoothed, so that the processing time can be shortened. As a result, the driven body 5 having the friction portion 5aa can be obtained.

Next, a second method for manufacturing the driven body 5 which can reduce the man-hours in the manufacturing process by not performing the nitriding treatment will be described. FIG. 4 is a process diagram for schematically explaining a second manufacturing method of the driven body 5. The main body 5bb of the driven body 5 is manufactured, for example, by cutting SUS430, which is a ferrite-based stainless steel, but the manufacturing method is not limited to this. The value of the coefficient of thermal expansion of SUS430 is close to the coefficient of thermal expansion of SUS420j2, which is a martensitic stainless steel used as a raw material for the friction portion 5aa. Therefore, by using SUS430 for the main body portion 5bb, it is possible to suppress the occurrence of cracks in the friction portion 5aa when the friction portion 5aa is formed by sintering. It should be noted that using an iron-based material for the main body 5bb, which has various characteristics including the coefficient of thermal expansion similar to the stainless steel used for the friction portion 5aa, not only suppresses the occurrence of cracks, but also suppresses the occurrence of cracks and the friction portion 5aa. It is also desirable from the viewpoint of improving the adhesion by mutual diffusion with the main body 5bb.

The main body 5bb is provided with a recess 5b1 in the circumferential direction. SUS420j2 powder (for example, average particle size: 10 μm), which is a raw material for the friction portion 5aa, is filled in the concave portion 5b1, and the powder near the surface layer is scraped off to fill the concave portion 5b1 with powder having the same height as the convex portion. Part 5a1 is formed. By using martensitic stainless steel as the raw material of the friction portion 5aa, it is possible to perform a hardening treatment by quenching following the sintering treatment. When the granulated powder is used when forming the powder filling portion 5a1, the fluidity of the powder is improved. As a result, the handleability can be improved, for example, the adhesion of powder to the punch or the like used in the pressing process, which is the next process, can be reduced. Subsequently, the powder filling portion 5a1 is pressed with a pressure of, for example, 1 to 15 ton / 300 mm ² using a cylindrical punch 8 to obtain a green compact 5a2. At that time, a sufficient clearance is provided between the inner outer peripheral surface of the punch 8 (a surface substantially parallel to the pressurizing direction) and the inner outer peripheral wall surface (side wall surface) of the recess 5b1. The region where the vibrating body 2 is frictionally slid with the protrusion 2a is near the center of the green compact 5a2, and the filling density of the SUS420j2 powder is increased in that portion because the pressing force by the punch 8 is acting. ..

Subsequently, the main body portion 5bb on which the green compact 5a2 is formed is sintered. The sintering process is performed, for example, in a vacuum atmosphere (in a vacuum furnace), holding at 1150 ° C. for 1 hour, lowering the temperature to 1050 ° C., holding at 1050 ° C. for 30 minutes, and then quenching with nitrogen gas in the same furnace. Do by. As a result, the powder filling portion 5a1 becomes a sintered body 5a3 and is directly bonded to and integrated with the main body portion 5bb. According to a hardness test conducted separately, the Vickers hardness of the sintered body 5a3 at the portion where the pressing force by the punch 8 was applied in the pressing step of the previous stage was 600 HV or more. That is, it was confirmed that quenching and hardening were performed at the same time in the sintering process.

Next, the liquid epoxy resin 5c is applied to the recesses of the sintered body 5a3 and held at 50 ° C. for 30 minutes to reduce the viscosity of the liquid epoxy resin 5c, whereby the liquid epoxy is applied to a part of the pores of the sintered body 5a3. The resin 5c is impregnated. At this time, the impregnation treatment may be performed in vacuum. As a result, the impregnation of the liquid epoxy resin 5c into the pores can be promoted. Then, for example, the liquid epoxy resin 5c is cured by leaving the liquid epoxy resin 5c at 80 ° C. for 1 hour. As a result, the sintered body 5a3 becomes the resin impregnated portion 5a4. Depending on the characteristics required for the friction portion 5aa, a ceramic powder such as green carborundum (GC) or white random ceramic powder (WA) may be mixed in the liquid epoxy resin 5c. As a result, the ceramic powder can be dispersed in a part of the pores of the sintered body 5a3. The type, particle size, grain morphology, amount, etc. of the ceramic powder to be added may be appropriately adjusted according to the characteristics required for the friction portion 5aa, taking into consideration the porosity, pore size, etc. of the sintered body 5a3. can. After cutting the upper surface of the convex portion 5b2 and the cured resin impregnated portion 5a4, the machined surface is brought into contact with the copper surface plate, and the copper surface plate is rotated while the polycrystalline diamond particles (average particle size) are formed on the copper surface plate. A smoothing treatment (polishing treatment) is performed by dropping a polishing material (slurry) containing (3 μm). The convex portion 5b2 and the upper surface portion of the cured resin impregnated portion 5a4 may be removed by grinding with a grindstone made of particles such as green carborundum (GC) instead of cutting.

FIG. 5 is a photograph showing a microstructure near the boundary between the friction portion 5aa and the main body portion 5bb (convex portion 5b2) on the polished surface (surface) after the smoothing treatment. It can be seen that at the boundary between the central portion of the friction portion 5aa (left side of the photo) and the main body portion 5bb (right side of the photo), there are many pores that appear black on the photograph, and the density is lower than that of the central portion of the friction portion 5aa. .. This is because the sintered body density is high at the center of the green compact 5a2 on which the pressing force of the punch 8 acts directly because the powder packing density is high, and the compaction powder on which the pressing force of the punch 8 does not act directly. This is because, at the peripheral edge of the body 5a2, the density of the sintered body is also small because the powder filling density is small. In the friction portion 5aa, the sintering process was performed integrally with the main body portion 5bb, which is a dense body, by providing a difference or inclination in the sintered body density between the central portion and the peripheral portion (the boundary portion with the main body portion 5bb). Even in this case, it is considered that cracks and the like are suppressed in the sintered body. The effect of suppressing the occurrence of cracks can be similarly obtained even when austenitic stainless steel SUS304, which has a larger coefficient of thermal expansion than SUS420j2, is used for the friction portion 5aa.

FIG. 6 is a process diagram for schematically explaining a third manufacturing method of the driven body 5. Since the main body portion 5bb to be prepared is the same as that used in the second manufacturing method, the description here will be omitted. A slurry of SUS420j2 powder (average particle size: 10 μm) is prepared. After filling the recess 5b1 with the prepared slurry, the powder-filled portion 5a1 is formed by holding the slurry at 80 ° C. for 1 hour and drying it. Next, using a punch 9 having a cylindrical shape and having a recess (recess) formed in the central portion in the radial direction, the powder filling portion 5a1 is pressurized by 170 MPa (= about 5 ton / 300 mm ² ). Let it be powder 5a2. The recess of the punch 9 is designed so that the convex portion 5b2 can be tilted toward the concave portion 5b1. Therefore, when the convex portion 5b2 falls toward the powder filling portion 5a1, the surface of the green compact 5a2 and the convex portion 5b2 become substantially the same height. After that, the sintering treatment and the smoothing treatment are performed in the same manner as in the second manufacturing method. As a result, the driven body 5 having the friction portion 5aa having a smooth surface can be obtained.

When the slurry contains a large amount of organic substances such as binders, it is desirable to perform a binder removal (solvent degreasing) treatment prior to the sintering treatment under the condition that the green compact 5a2 and the main body 5bb are not oxidized. After the sintering treatment, the sintered body 5a3 may be impregnated with an epoxy-based or acrylic-based adhesive in order to improve the bondability between the particles forming the sintered body 5a3. In the third manufacturing method, the portion of the convex portion 5b2 that is bent toward the concave portion 5b1 can be removed by a smoothing process (grinding process or polishing process) without providing a step of removing the concave portion 5b1 side. The surface of the friction portion 5aa can be finished in a desired state in a short time.

Next, a configuration example of a third vibration type actuator in which the friction material according to the embodiment of the present invention is used will be described. FIG. 7 is a cross-sectional view illustrating a schematic configuration of the third vibration type actuator 30. FIG. 8 is an exploded cross-sectional view of the vibrating actuator 30, showing only the main parts. In the vibration type actuator 30, the internal components are generally housed in a case including a flange 19, a side cover 25, and housings 21a and 21b. The vibrating actuator 30 includes driven bodies 11A and 11B, a vibrating body 12, a support member 14, a flexible printed wiring board 13, pressure springs 23a and 23b, and pressure equalizing rings 24a and 24b as internal components. Further, the vibration type actuator 30 has rotation transmission members 22a, 22b, internal bearings 15a, 15b, a shaft 16, bearings 26a, 26b, an E ring 17, and a spacer 18.

By sandwiching the vibrating body 12 between the two driven bodies 11A and 11B, the vibrating actuator 30 can generate twice as much torque as the vibrating actuator with one driven body. Further, the reaction force of the pressing force by the pressure springs 23a and 23b for pressing the two driven bodies 11A and 11B against the vibrating body 12 is only the tension of the shaft 16 which is the output shaft at the center thereof. Is. Therefore, the thrust force caused by the pressure springs 23a and 23b is not applied to the bearings 26a and 26b. Therefore, a large bearing that receives the thrust force caused by the pressure springs 23a and 23b is unnecessary, and energy loss due to friction of the bearing does not occur. With such a structure, the characteristics of small size, high torque, and high efficiency can be realized. Further, since the thrust force caused by the pressure springs 23a and 23b is not applied to the bearings 26a and 26b, the support member 14 supporting the vibrating body 12 has a torsional reaction caused by the rotational torque of the driven bodies 11A and 11B. Since only the force is applied, the rigidity of the shaft 16 in the axial direction may be small. The support member 14 itself has a flexible configuration in a direction orthogonal to the axial direction of the shaft 16 so as not to hinder the vibration of the vibrating body 12. The support member 14 is fixed by being sandwiched between the housing 21a and the side cover 25. A bearing 26a is fixed to the housing 21a, and by providing the E-ring 17 via the spacer 18, even if a thrust force is applied to the shaft 16, the friction portion (details will be described later) of the vibrating actuator 30 is applied. The structure does not affect the pressure.

In the vibrating body 12, a piezoelectric element 12c, which is an electric-mechanical energy conversion element, is arranged in the central portion, and the two elastic bodies 12a and 12b have electrical resistance to each other with the piezoelectric element 12c, the support member 14 and the flexible printed wiring board 13 sandwiched therein. It has a structure joined by welding. The flexible printed wiring board 13 supplies electric power to the piezoelectric element 12c and also serves as a terminal for detecting a voltage generated as a result of deformation of the piezoelectric element 12c.

The vibration type actuator 30 has a structure substantially symmetrical in the axial direction of the shaft 16 with the piezoelectric element 12c as the center. The shaft 16 is inserted into the vibrating body 12 and the internal bearings 15a and 15b so that the vibrating body 12 is sandwiched between the internal bearings 15a and 15b made of resin. Here, the vibrating body 12 is formed in a substantially columnar shape, and by synthesizing two bending vibrations, a vibrating motion like a rope in a skipping rope is performed. The internal bearings 15a and 15b are arranged at positions that are substantially nodes of the vibration so as not to interfere with the vibration excited by the vibrating body 12, whereby the shaft can be avoided while avoiding direct contact between the vibrating body 12 and the shaft 16. Coaxiality with 16 is ensured. The shaft 16 is inserted with the driven bodies 11A and 11B and the pressure springs 23a and 23b that press the driven bodies 11A and 11B against the vibrating body 12 to generate a frictional force. Made of resin to reduce uneven pressure generated at the ends of the pressure springs 23a and 23b, respectively, between the pressure spring 23a and the driven body 11A and between the pressure spring 23b and the driven body 11B, respectively. The pressure equalizing rings 24a and 24b of the above are arranged.

In the driven body 11A, after adhering the annular metal friction member 31 having a spring property and the annular elastic body 32, the friction surface of the metal friction member 31 is smoothed, and the elastic body 32 is attached to the rotation transmission member 22a. Is formed by adhering. The structure of the driven body 11B is the same as that of the driven body 11A. The rotation transmission members 22a and 22b are press-fitted into the shaft 16.

9A and 9B are diagrams for explaining the friction portion 12d provided on the vibrating body 12. FIG. 9A is an enlarged view of the region A shown in FIG. 7. The springy metal friction member 31 has a second contact portion that is in pressure contact with a friction portion (first contact portion) 12d provided on the vibrating body 12 by a force that the pressure springs 23a and 23b try to extend. Is. FIG. 9B is a perspective view of the elastic body 12a. The friction portion 12d is a stainless sintered body similar to the driven body 5 of the vibrating actuator 20, and is joined to the elastic body 12a by an adhesive. Generally, the stainless sintered body has a large vibration damping, and the vibration damping tends to be large particularly when the pores of the sintered body are impregnated with the resin. However, when the friction portion 12d, which is a stainless sintered body, is formed only on a part of the elastic body 12a, the vibration is not substantially attenuated due to the friction portion 12d. That is, by providing the friction portion 12d in a part of the vibrating body 12 (elastic body 12a) so as to come into contact with the metal friction member 31, it is possible to secure the characteristic required for the vibrating body 12 that the vibration is hard to be attenuated. can. Further, when the friction portion 12d is provided on a part of the elastic body 12a which is the base material, the vibration type actuator 20 can be formed by the above-mentioned second manufacturing method or the third manufacturing method. At that time, the powder filling portion 5a1 can be easily formed on the elastic body 12a by using a jig such as a mold that surrounds the outer circumference of the elastic body 12a.

Next, a configuration example of the fourth vibration type actuator in which the friction material according to the embodiment of the present invention is used will be described. 10A to 10D are diagrams for explaining the vibrating body 42 constituting the fourth vibrating actuator. FIG. 10A is a perspective view of the vibrating body 42. A piezoelectric element (not shown) is bonded to the lower surface of the vibrating body 42. The vibrating body 42 applies a rotational driving force to a driven body (not shown) that pressurizes and contacts the upper surface of the vibrating body 42, which is a frictional portion, by exciting a traveling type driving vibration (traveling wave) that travels in the circumferential direction. Used in well-known vibrating actuators. The upper surface of the vibrating body 42 is formed in a comb-teeth shape in which irregularities are repeated at regular intervals in the circumferential direction, whereby the vibration displacement excited by the vibrating body 42 can be expanded.

FIG. 10B is a perspective view of a precursor 41 (a part in a state before being processed into the vibrating body 42) used for manufacturing the vibrating body 42. FIG. 10C is a diagram for schematically explaining the processing method of the precursor 41. FIG. 10D is a cross-sectional view of the vibrating body 42. When forming a comb-shaped friction portion, it is not desirable to provide a friction portion made of a stainless steel sintered body on each convex portion because the manufacturing process becomes complicated. Therefore, for example, a main body portion 42b having an annular shape and a groove portion formed in the circumferential direction is prepared, and a friction member 42a made of a stainless sintered body that can be fitted into the groove portion is prepared. The friction member 42a can be manufactured in the same manner as the driven body 5 of the vibrating actuator 20. An adhesive is applied to the groove portion of the main body portion 42b, and the friction member 42a (second contact portion) is fitted into the groove portion. In this way, the precursor 41 can be obtained by performing the smoothing treatment on the upper surface in a state where the friction member 42a is joined to the main body portion 42b. Alternatively, in the same manner as in the second manufacturing method and the third manufacturing method of the vibrating actuator 20, a friction member 42a made of a stainless sintered body is formed in the recess, and the upper surface is smoothed. This also gives the precursor 41. In addition, using the screen printing method described above, a friction portion similar to the friction portion 1a of the vibration type actuator 10 may be formed on the upper surface of the annular main body portion in which the recess is not formed. Further, when the slurry is applied, the thickness of the coating film may be made uniform by utilizing centrifugal force while rotating the main body portion 42b in the same manner as spin coating.

As shown in FIG. 10C, the upper surface of the obtained precursor 41 is cut by a cutter 43 to form a groove (recess), so that the upper surface of the precursor 41 has a comb-like shape. Process. As a result, as shown in FIG. 10D, it is possible to obtain a vibrating body 42 in which the friction member 42a is arranged on the upper surface of each convex portion formed on the main body portion 42b. The friction member 42a has the same effect as that of the driven bodies 1 and 5.

Next, the operating characteristics of the various vibrating actuators described above, particularly the starting characteristics after being left in a high humidity environment, will be described. The vibrating actuator has a problem that the starting characteristic after being left in a high humidity environment is deteriorated. That is, there is a problem that the friction driving force due to the vibration excited by the vibrating body does not efficiently act on the driven body, so that the relative movement speed between the vibrating body and the driven body rises slowly. It is considered that the cause is that if the vibrating actuator is left in a humid environment, water molecules are adsorbed on the friction surface between the vibrating body and the driven body, and the friction surface becomes slippery. In particular, when it is placed in a high humidity environment, it is considered that the water becomes more slippery due to the presence of water as a water film.

The reason why the friction surface becomes slippery when the vibrating actuator is left in a humid environment can be explained by considering the mixed lubrication state and the fluid lubrication state. That is, in a dry environment (low humidity environment), a large frictional force is obtained by the true contact part of the solid, but if water exists between the frictional surfaces, the water film supports the force in the direction perpendicular to the frictional surface. , The true contact area of the solid is reduced. Unlike solids, water itself has an extremely small force to resist in the shearing direction, so the area ratio supported by water easily increases when the vibrating actuator is activated, and the friction surface between the driven body and the vibrating body increases. Friction force becomes small. Further, the holding torque (holding force) of the vibrating actuator also decreases due to the influence of moisture existing on the friction surface between the driven body and the vibrating body for the same reason as the problem of deterioration of the starting characteristics. This reason can also be explained by considering the above-mentioned mixed lubrication state and fluid lubrication state.

Correspondingly, the friction portions 1a, 2aa, 5aa, 42a of the friction material according to the present embodiment include a stainless steel sintered body and have holes. As a result, even if moisture due to humidity or the like is present between the friction surface of the friction portion and the friction surface of the member in frictional contact with the friction material, the moisture moves to the pores of the sintered body. It is possible to suppress a decrease in the true contact area between the friction surfaces. Therefore, by applying the friction material according to the present embodiment to at least one friction surface of the vibrating body and the driven body that are in frictional contact with each other, the true contact area on the friction surface between the vibrating body and the driven body is reduced. Can be suppressed. That is, in the vibrating actuator in which at least one friction surface of the vibrating body and the driven body in frictional contact with each other is made of the friction material according to the present embodiment, deterioration of the starting characteristics after being left in a high humidity environment is suppressed. can do.

Next, the test results obtained by taking the configuration of the vibrating actuator 20 as an example will be described. In the test, the driven body 5 shown in FIG. 3C was used as the driven body 5 of the vibration type actuator 20.

The vibrating actuators of Examples 1 to 3 were manufactured using the driven body 5. The vibrating actuator of Comparative Example 1 is made of a SUS420j2 molten material obtained by cutting a round bar obtained by rolling a cast billet manufactured by a normal stainless steel manufacturing method, and a nitrided layer is provided on the friction surface by an ion nitriding method. The driven body was used. The SUS420j2 molten lumber has a dense structure (microstructure). The vibrating actuator of Example 1 was made of a stainless steel sintered body obtained by sintering SUS420j2 powder, and was subjected to quenching treatment (hardening treatment) by quenching after holding at the sintering temperature in the sintering treatment. The driven body 5 was used. In the vibrating actuator of Example 2, as shown in FIG. 3B, SUS316 powder was formed into an annular shape using a well-known molding method, sintered under predetermined conditions, and then stainless-baked with a nitrided layer. A driven body 5 in which the body was impregnated with an epoxy resin was used. As the vibrating actuator of Example 3, a driven body 5 obtained by impregnating a stainless sintered body equivalent to the driven body 5 used in Example 1 with an epoxy resin containing GC # 2000, which is a ceramic powder, was used. .. FIG. 11 is an electron micrograph showing the state (microstructure) of the friction surface of the friction portion of the driven body 5 of Example 3. It can be confirmed that pores are present between the bonded stainless steel particles, and a part of the pores is impregnated with a resin containing ceramic powder. The method for manufacturing the driven body 5 of the vibrating actuator 20 described above can be used for manufacturing the driven body 5 used in each of the vibrating actuators of Examples 1 to 3.

For each of the produced vibration type actuators of Examples 1 to 3, the driven body is reciprocated 70,000 times with the rotation angle range of the driven body set to 0 ° to 50 °, and further, the rotation angle range is set to 50 ° to 100 °. The reciprocating drive was performed 5,000 times. By such a reciprocating drive, "familiarity" is generated between the protrusion 2a and the friction surface 5d. Familiarity means that the distance between the two surfaces around the true contact part of the friction surface has become closer. Due to the familiarity, the contact area of the protrusion 2a with respect to the friction surface 5d increases, and the area of the portion where the distance between the two surfaces is close to each other increases accordingly. After the protrusion 2a and the friction surface 5d become familiar with each other, the friction surface becomes more slippery due to the influence of humidity. That is, when the friction material and the mating member are in contact with each other in a certain area (true contact portion), a comparison between before the familiarity occurs (before familiarization) and after the familiarization occurs (after familiarization) is compared. , The distance between the parts that were not in contact with each other before familiarization is reduced. If water (water molecules) exists between two surfaces that are not in contact with each other in such a state, the water will support the normal force, so the true contact area will decrease and the shearing force (friction coefficient) of the friction surface will decrease. ) Decreases. On the other hand, when there is no moisture between the two surfaces that are not in contact with each other, a high coefficient of friction can be obtained by increasing the true contact area. Therefore, it is considered that the slipperiness of the friction surface greatly differs depending on whether or not water is present in the familiar portion. For this reason, the above-mentioned reciprocating drive is performed so that the influence of moisture on the friction surface is likely to appear.

Each vibrating actuator after reciprocating drive is left in a high humidity environment with a temperature of 60 ° C. and a relative humidity of 90% for 12 hours, and then taken out to a room temperature environment (temperature of 25 ° C. and a relative humidity of 50%). After leaving it for a while, the holding torque of the driven body 5 in the circumferential direction was measured. The holding torque was measured as follows. That is, the driven body 5 and the three vibrating bodies 2 were arranged according to the configuration of FIG. 3A, and the pressing force between them was set to 900 gf (9N). In this case, a load of 150 gf was applied to each of the protrusions 2a. When the contact portion of the protrusion 2a is substantially circular and its diameter is 0.9 mm, the apparent surface pressure is 235 gf (24N) / mm ² . A shaft member that passes through the radial center of the vibrating actuator and is orthogonal to the radial direction is arranged, the shaft member and the driven body 5 are connected, and the shaft member is rotated to rotate the driven body 5, thereby causing protrusions. The driven body 5 can be rotationally moved relative to the portion. A pulley was attached to the shaft member, and an elastic thread was wound around the pulley. The thread was wound up by a tensile tester to rotate the pulley, thereby rotating the shaft member. The holding torque was calculated from the value obtained by converting the output from the load cell of the tensile tester at this time into force.

In this test, since an external force is dynamically applied to the driven body 5 via a thread, changes in frictional resistance during that period are continuously captured, but stick slip occurs at that time. The value at the top of the saw blade, which corresponds to the static friction force, is read as the holding torque. Since the maximum speed at which the stick slip appears was 2 mm / min, this maximum speed was used as the relative moving speed between the protrusion 2a and the driven body 5 for obtaining the holding torque for the purpose of shortening the measurement time. Using.

FIG. 12 is a diagram showing a measurement result of the holding torque. When the driven body 5 starts to move, it shows a relatively high torque, but once it starts to move and the relative positions of the protrusion 2a and the friction surface 5d change, it can be seen that the holding torque is lower than when it starts to move. .. From this result, even when exposed to a high humidity environment, the original true contact part is maintained and a high holding torque is maintained at the beginning of movement, but after the relative position between the friction surfaces has moved, It is considered that the holding torque is drastically reduced due to the influence of the water film described above. That is, it is considered that water (water molecules) is adsorbed on the friction surface 5d, and it is considered that the frictional force between the friction surfaces is reduced by the presence of water as a film between the protrusion 2a and the friction surface 5d.

In Comparative Example 1, the stick slip (variation range of the magnitude of the holding torque) is small, which is considered to be because the friction surface is close to the fluid lubrication state. On the contrary, in Examples 1 to 3, the fluctuation range of the magnitude of the holding torque is large, and this is because the relative velocity of the friction surface and the friction coefficient are in a negative relationship, so that Comparative Example 1 It is considered that this is the result of the stick slip appearing more clearly.

The order of the magnitude of the holding torque is Comparative Example 1 <Example 1 <Example 2 <Example 3, and the holding torque of Example 3 is about 0.96 kgf · cm [0.10 N · m]. The value was 3 times that of the holding torque of Comparative Example 1 of about 0.30 kgf · cm [0.03 N · m]. In Example 1, even if water adheres to the friction surface 5d, the pores serve as a place for removing water, so that a true contact portion with the protrusion 2a is secured, and as a result, a larger holding torque than in the comparative example is shown. It is considered to be.

In all of Comparative Example 1 and Examples 1 to 3, the holding torque in the portion of the friction surface 5d that has not been reciprocated before being left in a high humidity environment (the portion that does not cause familiarity) is reciprocated. It showed a larger value than the part that was made to. From this, it is considered that the influence of the water film appears remarkably by causing the friction surface to become familiar by repeating the frictional sliding. In Examples 2 and 3, an oxide film formed by friction and a resin transfer film are present on the stainless steel portion on the friction surface 5d after reciprocating drive, and these films are the stainless steel material constituting the protrusion 2a and the friction member. Prevents direct contact between metals. As a result, the friction member (stainless steel sintered body impregnated with resin) used in Example 2 is larger than the friction member (stainless steel sintered body impregnated with resin) used in Example 1. Has high wear resistance. The reason why Example 2 showed a larger holding torque than that of Example 1 is that in Example 2, the progress of familiarization was slower than that of Example 1 due to the difference in wear resistance, and the state of the friction surface at the time of fabrication. It is presumed that the change from is small.

Similarly, it is considered that the reason why Example 3 showed a larger holding torque than that of Example 2 is due to the difference in wear resistance due to the presence or absence of the ceramic powder. That is, high wear resistance can be obtained in a structure in which a film that is hard and does not easily diffuse and react with the mating material exists on the friction surface, such as a structure in which ceramic powder is contained in the resin. The reason why Example 3 showed a larger holding torque than that of Example 2 is that in Example 3, the progress of familiarization was slower than that of Example 2 due to the difference in wear resistance, and the state of the friction surface at the time of fabrication. It is presumed that the change from is small.

Since stainless steel has high deformation resistance and high corrosion resistance, it has a surface suitable as a friction material, but depending on the friction conditions, the oxide film on the surface may be damaged and metal adhesion (or seizure) may occur. .. To solve this problem, if a part of the pores of the stainless sintered body is impregnated with resin, the resin impregnated in the pores moves to the friction surface and adheres to prevent direct metal contact. As a result, the occurrence of metal adhesion (or seizure) can be suppressed. Further, since the friction material (stainless steel sintered body) having pores is used in Examples 1 to 3, the substantial surface pressure is high on the friction surface of the friction material. As a result, it cannot be denied that the friction materials used in Examples 1 to 3 are inferior in wear resistance to the dense stainless steel materials used in Comparative Example 1 unless the friction surface is hardened. No. Therefore, in consideration of wear resistance (durability), when a stainless sintered body having pores is used as a friction material, a hardening treatment such as quenching treatment or at least nitriding treatment on the friction surface is performed. It is desirable to do. When the nitriding treatment is performed, the stainless sintered body has a nitrogen-containing region (a layer composed of a nitride phase (compound phase), a layer in which nitrogen is diffused, and a layer in which nitrogen is diffused, depending on the conditions of the nitriding treatment and the depth from the surface. Layers in their intermediate state, etc.) are formed. The layer made of the nitride phase is a layer made of stainless steel chromium or a nitride obtained by combining iron and nitrogen. The nitrogen-diffused layer is a layer in which nitrogen atoms are diffused between stainless steel lattices. The layer in the intermediate state is a layer in which nitrogen atoms and chromium atoms are close to each other, but the compound is not stable.

Next, a test result using a modified example of the second vibration type actuator 20 shown in FIG. 3D will be described. The vibrating actuators of Comparative Example 2 and Examples 4 to 6 were manufactured by using the driven body 5 having friction portions 5aa different from each other. In Comparative Example 2, a driven body 5 in which an annular member made of a SUS420j2 molten material as a friction portion 5aa is joined to a recess 5b1 of the main body portion 5bb by an adhesive is used, and a circle serving as a friction surface with respect to the protrusion 2a. A nitride layer was provided on the surface of the annular member by an ion nitriding method. The SUS420j2 molten material is obtained by cutting a round bar obtained by rolling a cast billet produced by a normal stainless steel production method by cutting, and has a dense structure (microstructure).

In Example 4, a friction portion 5aa made of a stainless steel sintered body obtained by sintering SUS420j2 powder and subjected to quenching treatment (hardening treatment) by quenching after holding at the sintering temperature in the sintering treatment is provided. The driven body 5 to have was used. In Example 5, a driven body 5 having a friction portion 5aa obtained by impregnating a stainless sintered body equivalent to the friction portion 5aa used in Example 4 with an epoxy resin was used. In Example 6, a driven body 5 was used in which a stainless sintered body equivalent to the friction portion 5aa used in Example 4 was impregnated with an epoxy resin containing green carborundum ceramic powder. The method of manufacturing the driven body 5 used in Examples 4 to 6 is as described with reference to FIG. Therefore, in the driven body 5 used in Examples 4 to 6, the stainless steel sintered body, which is the friction portion 5aa, is formed by integral sintering with the main body portion 5bb.

Each of the produced vibration type actuators was subjected to the reciprocating drive applied to Examples 1 to 3 and Comparative Example 1. As a result, "familiarity" was generated on the friction surfaces of the protrusion 2a and the friction portion 5aa. After that, the vibrating actuators of Examples 4 to 6 and Comparative Example 2 are left in a high humidity environment under the same conditions as in Examples 1 to 3 and Comparative Example 1, and further, with Examples 1 to 3 and Comparative Example 1. The holding torque of the driven body 5 in the circumferential direction was measured by the same method.

FIG. 13 is a diagram showing a measurement result of the holding torque. The driven body 5 (friction portion 5aa) shows a relatively high torque at the start of movement, but once the movement starts and the relative positions of the friction surfaces of the protrusion 2a and the friction portion 5aa change, the holding torque becomes higher than that at the start of movement. It can be seen that it is decreasing.

From this result, even when exposed to a high humidity environment, the original true contact part is maintained and a high holding torque is maintained at the beginning of movement, but after the relative position between the friction surfaces has moved, It is considered that the holding torque is drastically reduced due to the influence of the water film described above. That is, it is considered that water (water molecules) is adsorbed on the friction surface of the friction portion 5aa, and the moisture exists as a film between the friction surface of the protrusion 2a and the friction portion 5aa, so that the frictional force between the friction surfaces is present. Is thought to decrease.

The order of the magnitude of the holding torque is Comparative Example 2 <Example 4 <Example 5 <Example 6, and the holding torque of Example 6 is about 1.00 kgf · cm [0.10 N · m]. The value was 3 times that of the holding torque of Comparative Example 2 of about 0.30 kgf · cm [0.03 N · m]. In the fourth embodiment, even if water adheres to the friction surface of the friction portion 5aa, the pores serve as a place for excluding the moisture, so that the true contact portion with the protrusion 2a is secured, and as a result, the holding portion is larger than that of the comparative example 2. It is probable that it showed torque.

In all of Comparative Example 2 and Examples 4 to 6, the holding torque in the portion of the friction portion 5aa that has not been reciprocated before being left in a high humidity environment (the portion that does not cause familiarity) is reciprocated. It showed a larger value than the part that was made to. From this, it is considered that the influence of the water film appears remarkably by causing the friction surface to become familiar by repeating the frictional sliding. In Examples 5 and 6, an oxide film and a resin transfer film generated by friction are present on the stainless steel portion on the friction surface of the friction portion 5aa after reciprocating drive, and these films form the protrusion 2a and the friction portion 5aa. Prevents direct contact between metals with the constituent stainless steel materials. As a result, the friction portion 5aa (stainless steel sintered body impregnated with resin) used in Example 5 is the friction portion 5aa (stainless steel sintered body impregnated with resin) used in Example 4. Has higher wear resistance than. The reason why Example 5 showed a larger holding torque than that of Example 4 is that in Example 5, the progress of familiarization was slower than that of Example 4 due to the difference in wear resistance, and the state of the friction surface at the time of fabrication. It is presumed that the change from is small.

FIG. 14A is an electron micrograph showing the state (microstructure) of the friction surface before the reciprocating drive of Example 5. It can be confirmed that pores are present between the bonded stainless steel particles and that a part of the pores is impregnated with resin. FIG. 14B is a photomicrograph showing the state of the friction surface of Example 5 after the reciprocating drive of 70,000 times is completed. A brownish abrasion powder was confirmed in the pores of the frictional sliding range, and it was confirmed that the abrasion powder was hematite [Fe (Cr) ₂ O ₃ ] from the color and component analysis. FIG. 14C is an electron micrograph showing the state (microstructure) of the friction surface before the reciprocating drive of Example 6. It can be confirmed that the resin is mottled in the stainless steel and the ceramic particles (ceramic powder) are dispersed in the mottled resin.

Next, another method for producing the friction material according to the present invention will be described. FIG. 15 is a diagram for schematically explaining a method of manufacturing a friction material using a mold. Here, the friction material is formed on the test pin of the pin-on disk friction tester (JIS R 1613-1993), but the friction material of the vibration type actuator 30 can be manufactured by the same method. .. This method is convenient when producing a structure in which the friction material is integrally formed around the friction material without a wall portion of the base material (when the friction material is not formed in the recess).

A second mold 54 having a cylindrical shape is inserted into the columnar space provided in the first mold 53. At this time, since there is a certain clearance between the first mold 53 and the second mold 54, the second mold 54 is placed in the inserted columnar space in the thrust direction (up and down in the figure). It is possible to move in the direction). Subsequently, a cylindrical elastic body serving as a base material for forming the friction material (sintered body) so that the space 51 for filling the stainless powder is formed in the columnar space of the first mold 53. 52b is inserted into the cylindrical space of the first mold 53 in the same manner as the second mold 54. The space portion 51 is filled with stainless steel powder to form the powder filling portion 52a1. The powder filling portion 52a1 is pressed and compressed using the punch 55 to form a molded body 52a2.

Subsequently, the second mold 54 is pushed out toward the elastic body 52b using the knockout pin 56, so that the molded body 52a2 is taken out together with the elastic body 52b. At this time, the elastic body 52b and the molded body 52a2 are bonded to each other, and the molded body 52a2 does not separate from the elastic body 52b unless a strong force is applied. The strength and density of the molded body can be adjusted by adjusting the type of binder that binds the stainless steel powders to each other, the addition ratio to the stainless steel powder, and the pressure molding pressure by the punch 55. By sintering the molded body 52a2 integrated with the elastic body 52b under the same conditions as the sintering conditions of the green compact 5a2 described with reference to FIG. 4, the molded body 52a2 becomes stronger than the elastic body 52b. It becomes the sintered body 52a3 bonded to. By smoothing the upper surface of the sintered body 52a3 by grinding or polishing, a friction test pin on which the sintered body 52a3, which is a friction material, is formed can be obtained, and vibration can be obtained by the same method as described above. The friction material of the mold actuator 30 can be obtained. Since the side surface (circumferential curved surface) of the sintered body 52a3 does not become a friction surface, it may be left as it is after the sintering treatment.

FIG. 16 is a diagram for schematically explaining another method for manufacturing a friction test pin on which a friction material is formed. As an elastic body 62b used as a base material for forming a friction material (sintered body), a SUS304 round bar having a diameter of 10 mmφ, which is easily available, is prepared, and a recess 62b1 having a side wall portion 62b2 on one end surface by cutting or the like is prepared. To form. However, the diameter of the elastic body 62b is not limited to 10 mmφ. A stainless powder (for example, SUS316L) is filled in the recess 62b1 of the elastic body 62b to form a powder filling portion 62a, and then the powder filling portion 62a is pressed and compressed by a punch 55 to form a molded body 62a2. By sintering the molded body 62a2 integrated with the elastic body 62b under the same conditions as the sintering conditions of the green compact 5a2 described with reference to FIG. 4, the molded body 62a2 becomes stronger than the elastic body 62b. It becomes the sintered body 62a3 bonded to. Finally, a cutting process for removing the side wall portion 62b2 (for example, a cylindrical grinding process) and a smoothing process for the upper surface of the sintered body 62a3 are performed. As a result, a friction test pin on which the sintered body 62a3, which is a friction material, is formed can be obtained, and the friction material of the vibration type actuator 30 can be obtained by the same method as described above.

The method for producing the friction material described above is different from the molding method using the first mold 53 described with reference to FIG. 15, and here, as the stainless powder, a binder (for example, stearic acid emulsion, polyvinyl alcohol, etc.) is used. ) Is not included. In general, when stainless steel powder is compressed using a mold without mixing a binder, it is often broken when it is taken out from the mold due to the low strength of the molded product. On the other hand, when a recess 62b1 having a side wall portion 62b2 is formed in an elastic body 62b corresponding to a mold and a molded body is molded from stainless powder in the recess 62b1, it is not necessary to take out the molded body 62a2. The destruction of 62a2 does not occur. Further, in producing the sintered body, the role of the binder is mainly to maintain the shape of the molded body until sintering. However, when a binder is contained, a binder removal step is required before the sintering process, and the binder removal step is generally performed by holding the binder at a temperature of about 400 ° C. for a predetermined time in the atmosphere. .. At that time, since the strength of the molded body is reduced after the binder is removed, the shape of the molded body cannot be maintained during the sintering process, and cracks may occur. Further, since the surface of the stainless steel powder particles is oxidized in the binder removal step, the metal diffusion bond between the particles in the sintering reaction is hindered, and the desired strength is obtained without sufficient bonding between the particles. It may not be possible. In particular, when a sintered body having a large porosity is produced, the shrinkage rate at the time of sintering becomes large, so that such inconvenience is likely to occur.

Further, carbon or the like having a small friction coefficient is used as a plate on which the molded product is placed during sintering so that the shrinkage during sintering can be freely shrunk as much as possible without being partially restrained. However, the gravity applied to the molded body inhibits the shrinkage during sintering, which may cause deformation or cracking in the fired body. On the other hand, if the molded body 62a2 is formed in the recess 62b1 provided in the elastic body 62b, the possibility of deformation or cracking in the obtained fired body can be significantly reduced. The reason for this is that the molded body 62a2 itself becomes strong against an external force due to the presence of the side wall portion 62b2, and the molded body 62a2 can maintain its shape in the recess 62b1 without using a binder. That is, by providing the recess 62b1 having the side wall portion 62b2, the molded body 62a2 can be maintained without losing its shape.

Next, application examples of the vibrating actuators 10, 20, and 30 will be described. FIG. 17 is a perspective view showing a schematic structure of a robot 100 equipped with a vibration type actuator, and here exemplifies a horizontal articulated robot which is a kind of an industrial robot. Rotational drive motors used for bending arm joints, gripping and rotating hands of industrial robots, etc. show TN characteristics (load torque-rotational speed relationship) that can obtain high torque at low rotation speeds. Those having a drooping characteristic) are required. Therefore, for example, the rotation drive type vibrating actuator 20 (or the vibrating actuator 30) is built in the arm joint portions 111a to 111c and the hand portion 112 in the robot 100.

The arm joint portion 111a attached to a base (not shown) rotates the arm 120a with its thrust axis as a central axis. The arm joint portion 111b connects the arms 120a and 120b so that the crossing angles of the arms 120a and 120b can be changed, and the arm joint portion 111c connects the arms 120b so that the crossing angles of the arms 120b and 120c can be changed. , 120c are connected. The hand portion 112 has an arm 120d, a grip portion 121 attached to one end of the arm 120d, and a hand joint portion 122 connecting the arm 120d and the grip portion 121, and the hand joint portion 122 rotates the grip portion 121. Let me. The vibrating actuator 20 (or the vibrating actuator 30) is used as a rotation driving device for the arm joint portions 111a to 111c and the hand joint portion 122.

Subsequently, an image pickup device (optical device) including the linear drive type vibration type actuator 10 will be described. FIG. 18 is a perspective view showing a schematic structure of the lens driving mechanism 200 included in the lens barrel. The lens driving mechanism 200 includes a vibrating body 201, a lens holder 202, a first guide bar 203, a second guide bar 204, a pressure magnet 205, and a lens 206. The vibrating body 201 and the second guide bar 204 correspond to the vibrating body 2 and the driven body 1 constituting the vibrating actuator 10 described with reference to FIG. 1, respectively.

The first guide bar 203 and the second guide bar 204 are held on a substrate (not shown) so as to be parallel to each other. The lens holder 202 has a cylindrical holder portion 202a for holding the lens 206, a holding portion 202b for holding the vibrating body 201 and the pressurizing magnet 205, and a guide portion 202c through which the first guide bar 203 is inserted. The first guide portion is formed by movably inserting the guide portion 202c into the first guide bar 203.

The pressure magnet 205 is composed of a permanent magnet and two yokes arranged at both ends of the permanent magnet. A magnetic circuit is formed between the pressurizing magnet 205 and the second guide bar 204, and an attractive force is generated between these members so that the pressure magnet 205 is arranged between the pressurizing magnet 205 and the second guide bar 204. The vibrating body 201 is pressed against the second guide bar 204. As a result, the two protrusions (corresponding to the protrusion 2a of the vibrating body 2) of the vibrating body 201 come into pressure contact with the second guide bar 204 to form the second guide portion. The second guide portion forms a guide mechanism by utilizing the attractive force by magnetism, and the pressure magnet 205 is not in contact with the second guide bar 204. Therefore, it is expected that the vibrating body 201 and the second guide bar 204 will be separated from each other when the second guide portion receives an external force or the like. As a countermeasure, the lens drive mechanism 200 is configured so that the lens holder 202 (vibrating body 201) returns to a predetermined position when the dropout prevention portion 202d provided on the lens holder 202 comes into contact with the second guide bar 204. Has been done.

The driving method of the vibrating body 201 is the same as the driving method of the vibrating body 2, and the vibrating body 201 and the second guide bar 204 are brought together by generating elliptical vibration in the two protrusions of the vibrating body 201. A frictional driving force is generated between them. At this time, since the first guide bar 203 and the second guide bar 204 are fixed, the lens holder 202 is moved by the generated frictional driving force to the length of the first guide bar 203 and the second guide bar 204. It can be moved along the direction. In the lens drive mechanism 200, a magnetic force is used for the pressurizing mechanism, but the present invention is not limited to this, and an urging force by a spring may be used for the pressurizing mechanism. Further, the lens drive mechanism 200 uses a linear drive type vibration type actuator 10, but the lens drive mechanism 200 is not limited to this, and the rotation drive type vibration type actuators 20 and 30 shown in FIGS. 3A or 7 are used. May be good. That is, the structure is such that the rotational output of the vibrating actuators 20 and 30 is converted into a driving force that linearly moves the member holding the lens in the optical axis direction by the engagement between the cam pin and the cam groove, the gear, and the like. Just do it. Driving the lens by the vibration type actuator is suitable for driving the autofocus lens, but is not limited to this, and can also be used for driving the zoom lens. Further, the vibration type actuator can also be used to drive the lens or the image sensor at the time of image stabilization.

Although the present invention has been described in detail based on the preferred embodiments thereof, the present invention is not limited to these specific embodiments, and various embodiments within the scope of the gist of the present invention are also included in the present invention. Included in the invention. Further, each of the above-described embodiments is merely an embodiment of the present invention, and each embodiment can be combined as appropriate. The vibrating actuator according to the present invention is not limited to the robot and the lens barrel (imaging device) described with reference to FIGS. 17 and 18, and is a component that requires positioning by driving the vibrating actuator. It can be widely applied to electronic devices equipped with.

1,5 Driven body (contact body)
2 Vibrating body 2a Protruding part 2aa Friction part 2b Elastic body 2c Piezoelectric element 5c Epoxy resin 10, 20, 30 Vibration type actuator 42a Friction member 42b Main body 100 Robot 200 Lens drive mechanism

Claims (26)

A vibrating body having an electric-mechanical energy conversion element and an elastic body, and a contact body that is in pressure contact with the vibrating body are provided, and the vibrating body and the contact body are relatively brought into contact with each other by vibration excited by the vibrating body. It is a vibrating actuator that moves
Wherein at least one of the second contact portion for contacting with the vibration member at a first contact portion or the contact body in contact with the contact body in the vibration member comprises a stainless steel sintered body having pores, said pores one A vibrating actuator characterized in that a portion is impregnated with a resin, the resin is exposed on the surface of the stainless sintered body, and the other part of the pores is exposed on the surface. A vibrating body having an electric-mechanical energy conversion element and an elastic body, and a contact body that is in pressure contact with the vibrating body are provided, and the vibrating body and the contact body are relatively brought into contact with each other by vibration excited by the vibrating body. It is a vibrating actuator that moves
At least one of the first contact portion in contact with the contact body in the vibrating body or the second contact portion in contact with the vibrating body in the contact body includes a stainless sintered body having pores and is one of the pores. The portion is impregnated with resin, and the resin is exposed on the surface of the stainless sintered body.
A vibrating actuator characterized in that ceramic particles are dispersed in the resin. The vibrating actuator according to claim 1 or 2 , wherein the contact body is made of the stainless sintered body. The contact body has a main body portion and a second contact portion provided on the main body portion and in contact with the vibrating body.
The vibrating actuator according to claim 3 , wherein the stainless steel sintered body of the second contact portion is directly coupled to the main body portion. The vibrating actuator according to claim 4 , wherein a recess is provided in the main body, and the stainless sintered body is provided in the recess. The first contact portion, said provided in the elastic body, wherein the stainless steel sintered first contact portion, claim 1, wherein the bonded said direct and elastic body The vibrating actuator according to any one of the above items. The vibrating actuator according to claim 6 , wherein a recess is provided in the elastic body, and the stainless sintered body is provided in the recess. Vibration type actuator according to claim 1, characterized in that the ceramic particles are dispersed in the resin. The vibrating actuator according to any one of claims 1 to 8 , wherein the stainless sintered body is made of martensitic stainless steel and has a Vickers hardness of 600 HV or more. The vibrating actuator according to any one of claims 1 to 8 , wherein the stainless sintered body is made of austenitic stainless steel and has a nitride phase on its surface. The vibrating actuator according to any one of claims 1 to 10.
An electronic device including a member positioned by driving the vibration type actuator. It has a friction part including a stainless steel sintered body having pores, a part of the pores is impregnated with a resin, the resin is exposed on the surface of the stainless steel sintered body, and the other part of the pores is the surface. A friction material characterized by being exposed to stainless steel. Friction having a friction portion including a stainless sintered body having pores, wherein a part of the pores is impregnated with a resin, the resin is exposed on the surface, and ceramic particles are dispersed in the resin. Material. The friction material of claim 12, the ceramic particles prior Bark in fat, characterized in that the dispersed. The friction material according to any one of claims 12 to 14, wherein the resin is an epoxy resin or an acrylic resin. The friction material according to any one of claims 12 to 15 , wherein the friction portion is made of the stainless sintered body. Has a base material
The friction material according to any one of claims 12 to 16 , wherein the stainless steel sintered body of the friction portion is directly bonded to the base material. The friction material according to any one of claims 12 to 17 , wherein the resin is mottledly dispersed in the stainless sintered body. The friction material according to any one of claims 12 to 18 , wherein the ceramic particles are dispersed in the resin. A method for producing a friction material having a base material and a friction portion provided on the base material and containing a stainless sintered body having pores.
The molding is formed by molding a molded body from the stainless powder with respect to the base material and integrally sintering the molded body and the base material in a state where the molded body of the stainless powder and the base material are in contact with each other. The stainless sintered body formed by sintering the body is integrally formed with the base material, and the body is integrally formed.
Impregnated with resin in some of the pores of the sintered stainless steel body, exposing the resin to a surface of the stainless steel sintered body, another part of the pores is characterized by Rukoto are exposed to the surface friction How to make the material. A method for producing a friction material having a base material and a friction portion provided on the base material and containing a stainless sintered body having pores.
The molding is formed by molding a molded body from the stainless powder with respect to the base material and integrally sintering the molded body and the base material in a state where the molded body of the stainless powder and the base material are in contact with each other. The stainless sintered body formed by sintering the body is integrally formed with the base material, and the body is integrally formed.
A part of the pores of the stainless steel sintered body is impregnated with resin, and the resin is exposed on the surface of the stainless steel sintered body.
A method for producing a friction material, which comprises dispersing ceramic particles in the resin. A recess is provided in the base material, the recess is filled with the stainless powder, and a compact is formed from the stainless powder on the base material by applying pressure to the stainless powder filled in the recess. The method for producing a friction material according to claim 20 or 21 , wherein the friction material is produced. The friction material according to claim 22 , wherein a constant clearance is provided between a surface substantially parallel to the pressurizing direction of the pressurizing member used when applying pressure to the stainless powder and a side wall surface of the recess. How to make. A recess is provided in the base material, the recess is filled with a slurry containing the stainless powder, and the slurry is dried to form a molded body from the stainless powder on the base material. The method for producing a friction material according to claim 20 or 21. After inserting the base material into a mold, the space formed by the base material and the mold is filled with the stainless powder, the stainless powder is compressed and molded, and the molded stainless powder and the base are formed. The method for producing a friction material according to claim 20 or 21 , wherein the material is integrally taken out from the mold, and the molded stainless powder is sintered integrally with the base material. Using martensitic stainless steel powder as the stainless steel powder,
The invention according to any one of claims 20 to 25 , wherein the molded stainless steel powder is integrally sintered with the base material and then rapidly cooled to quench the stainless steel sintered body. Method of manufacturing friction material.

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