JP7581100B2 - Vibration actuator, camera head, and electronic device - Google Patents

Description

The present invention relates to a vibration actuator having a vibrating body and a contact body.

Because of their characteristics of low speed and high torque, vibration actuators have been put to practical use, for example as drive motors for autofocus in the photographic lenses of single-lens reflex cameras, and in recent years they are expected to be used in a variety of electronic devices other than cameras. For example, vibration actuators are expected to be used to drive the joints of robot arms and the rotation of robot hands, to drive the rotation of the pan heads of imaging devices such as surveillance cameras, and to drive the rotation of photosensitive drums in image forming devices.

In order to meet the demands of improving the productivity and reducing the cost of vibration actuators for such applications, a technology has been proposed in which the friction sliding member of the vibrating body is made of a separate material (see Patent Document 1). This involves manufacturing the friction sliding member separately from the main body of the vibrating body, and then bonding the two together. Similarly, a technology has also been proposed in which the friction sliding member of the moving body (contact body) is made of a separate material.

The technology described in Patent Document 1 proposes joining the vibrating body and the contact body as separate members, and then processing the friction sliding parts in a post-process such as lapping to smooth them out. This is because vibration actuators are required to achieve lower sound pressure level standards for quietness, which have been required in recent years, and also to perform smooth operation from the perspective of high position controllability standards such as the rotational drive of camera platform and robotic hands.

However, processes such as lapping to smooth out frictional sliding parts take time and are a cause of high costs.

Patent No. 3450524

Therefore, the present invention provides a vibration actuator that achieves quiet, uniform and smooth rotational operation without incurring large costs.

A vibration actuator is provided, comprising a vibrating body having a ring-shaped elastic body and an electromechanical energy conversion element, and a ring-shaped contact body in contact with the vibrating body, the contact body having a first friction part in contact with the vibrating body and a first non-contact part adjacent to the first friction part and not in contact with the vibrating body, the elastic body having a second friction part in contact with the first friction part and a second non-contact part adjacent to the second friction part and not in contact with the contact body, the first friction part has a lower hardness than the second friction part, and the first non-contact part has a smaller root mean square roughness than the second non-contact part.

The above invention makes it possible to provide a vibration actuator that is low-cost, suppresses the generation of abnormal noise, and achieves smooth rotational operation.

1 is a cross-sectional view illustrating a schematic configuration of a vibration actuator according to a first embodiment of the present invention. 2 is a diagram for explaining a state of deformation of a driving vibration excited in the vibrator in FIG. 1 . FIG. 2A and 2B are a schematic view and a detailed view showing the configuration of a contact body and a vibrating body in FIG. 1 . 2 is a diagram showing a schematic diagram of a wear state of the friction member and the elastic body in FIG. 1 . FIG. 2 is a diagram illustrating a configuration of a first modified example of the contact body in FIG. 1. FIG. 1. FIG. 4 is a diagram illustrating a configuration of a second modified example of the contact body in FIG. 1. FIG. 4 is a diagram illustrating a configuration of a third modified example of the contact body in FIG. 1. FIG. 4 is a diagram illustrating a configuration of a fourth modified example of the contact body in FIG. 1. FIG. 9 is a diagram illustrating a configuration of a fifth modified example of the contact body in FIG. 1. FIG. 9 is a diagram illustrating a configuration of a sixth modified example of the contact body in FIG. 1 is a diagram showing a schematic configuration of a camera platform on which a vibration actuator according to an embodiment of the present invention is mounted, and an imaging device mounted on the camera platform;

[Example 1]
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First Embodiment
1 is a cross-sectional view showing a schematic configuration of a vibration actuator 10 according to a first embodiment of the present invention. The mechanical configuration of the vibration actuator 10, including a vibrating body 20, a contact body 300 (moving body, driven body), and a pressure mechanism 40, is functionally equivalent to that of the vibration actuator described in, for example, JP 2017-108615 A.

The vibration actuator of this embodiment includes a vibrating body having an elastic body and an electromechanical energy conversion element, and a contact body that contacts the vibrating body. In addition, it includes a power supply member (flexible printed circuit board) that supplies power to the electromechanical energy conversion element.

In FIG. 1, the vibration actuator 10 includes a vibrating body 20 formed in a circular ring shape, a contact body 300 formed in a circular ring shape, and a pressure mechanism 40. The vibration actuator 10 also includes a shaft, a housing, and a bearing.

The vibrating body 20 has an elastic body 21, a piezoelectric element 22 which is an electrical-mechanical energy conversion element bonded to the elastic body 21, and a power supply member 100 which is bonded to the piezoelectric element 22 and applies a driving voltage which is an AC voltage to the piezoelectric element 22.

The pressure mechanism 40 has a vibration-damping rubber 41, a pressure spring receiving member 42, a pressure spring receiving rubber 43, a pressure spring 44, and a pressure spring fixing member 45. The vibrating body 20 and the contact body 300 are arranged concentrically with the shaft as the central axis, and are in pressure contact (frictional contact) with each other in the thrust direction of the shaft by the pressure mechanism 40 fixed to the shaft. Specifically, the pressure spring 44, whose movement is restricted by the pressure spring fixing member 45 fixed to the shaft, presses the contact body 300 in the thrust direction via the vibration-damping rubber 41, the pressure spring receiving member 42, and the pressure spring receiving rubber 43. This configuration ensures stable contact between the contact body 300 and the vibrating body 20.

In the vibration actuator 10, a driving voltage, which is an AC voltage, is applied to the piezoelectric element 22 through the power supply member 100 to excite the vibration body 20 to drive vibration. The form of the driving vibration depends on the number and arrangement of the electrodes of the piezoelectric element 22, but the piezoelectric element 22 is designed so that the excited driving vibration becomes an n-th order (n=9 in this embodiment) traveling wave that advances in the circumferential direction of the vibration body 10. Note that the n-th order driving vibration is a bending vibration with n waves in the circumferential direction of the vibration body 20. The driving vibration generated in the piezoelectric element 22 drives the contact body 300 in the circumferential direction around the shaft by the traveling wave generated in the contact portion 25 of the vibration body 20. In other words, the contact body 300 rotates relatively to the vibration body 20 while maintaining its concentricity. The rotational force generated in the contact body 300 is output to the outside through the pressure mechanism 40 and the shaft.

The vibration actuator 10 of this embodiment shown in Figure 1 can freely rotate a movable object by, for example, fixing the housing to a desired member and fixing the movable object, such as a camera, to a flange surface that is configured to diverge downward from the shaft. On the other hand, it is also possible to fix the shaft and rotate the housing.

Figure 2 is a diagram for explaining the state of deformation of the driving vibration excited in the vibrating body 20. Note that in Figure 2, the displacement is exaggerated to make it easier to understand the displacement of the driving vibration excited in the vibrating body 20.

Figure 3(a) is a cross-sectional view that shows the configuration of the contact body 300 and the configuration of the vibrating body 20, which has a different form from the vibrating body described above. The vibrating body 20 of this embodiment has an elastic body 21 with a trapezoidal cross section. A piezoelectric element 22, which is an electromechanical energy conversion element, is bonded to the elastic body 21. Note that other members, including a power supply member for applying a drive voltage to the piezoelectric element 22, are the same as those in the vibration actuator described above and are not shown. The contact body 300 has a main body member 301 and a friction member 302 that is a separate member from the main body member 301. The main body member 301 and the friction member 302 are connected by adhesion or bonding.

The main body member 301 has a base portion 301a and a support portion 301b extending in the radial direction of the contact body 300. The support portion 301b has an L-shaped cross section, and a friction member 302 is connected to the end portion. The main body member 301 is configured in a circular ring shape.

Figure 3(b) is a detailed cross-sectional view of the frictional contact portion where the contact body 300 and the elastic body 21 come into contact. The friction member 302 has a first contact portion 302a that comes into contact with the elastic body 21, and a first non-contact portion 302b that is adjacent to the first friction portion 302a and does not come into contact with the elastic body 21. The elastic body 21 has a second friction portion 21a that comes into contact with the first friction portion 302a, and a second non-contact portion 21b that is adjacent to the second friction portion 21a and does not come into contact with the friction member 302. In other words, the first friction portion is held by the support portion, and both ends of the ring-shaped contact body of the first friction portion in the radial direction are configured to have portions that do not come into contact with either the contact body or the vibrating body.

The friction member 302 has a lower hardness than the elastic body 21, and the second friction portion 20b has a smaller root-mean-square roughness than the second friction portion 21b of the elastic body. In simple terms, the friction member 302 has a soft and smooth surface property compared to the elastic body 21, and the elastic body 21 has a hard and rough surface property compared to the friction member 302.

The friction member 302 has a convex shape with a curvature in cross section relative to the elastic body 21, and is configured in a circular ring shape. In this embodiment, the magnitude of the curvature is R0.6, and the curvature is the same over the entire convex shape, but it may have a variable curvature in which the curvature changes depending on the position, and the curvature may be selected depending on the usage environment and product life. The convex tip of the friction member 302 in the initial state, when it is not worn, is in point contact with the rough surface of the elastic body 21, but as frictional sliding occurs, the convex tip of the friction member 302 wears and the rough surface of the elastic body 21 also wears, and both form flat parts. In addition, since the friction member 302 is configured in a circular ring shape, it is in line contact around the circumference in the initial state, and as wear progresses, it becomes flat contact.

Figure 4 is a cross-sectional view showing the frictional contact state between the friction member 302 and the elastic body 21. Figure 4a shows the initial state of the friction sliding part that is not worn, and Figure 4b shows the friction sliding part that has reached a steady state after initial wear. As shown in Figure 4a, in the initial state, neither the friction member 302 nor the elastic body 21 is worn, so the convex tip of the friction member 302 and the protruding part of the rough surface of the elastic body 21 are in point contact, resulting in a high surface pressure. As shown in Figure 4b, when the friction member 302 is operated multiple times, the convex tip of the friction member 302 is worn, and the hard rough surface of the elastic body 21 is also worn to form a flat part, resulting in a state where the surface pressure is reduced. The friction material 302 has a curvature in the radial direction, and even if wear gradually progresses, the friction material 302 has a smooth surface property, so the smooth surface always comes into contact with the elastic body 21, making it possible to maintain smooth rotation and quietness.

In addition, during the operation check of the shipping inspection in the manufacturing process, a rotation speed and load greater than those in normal use are applied, so that a large amplitude occurs in the vibrator, and contact and initial wear occur over a wider range than the contact area during normal use, and the hard, rough surface of the elastic body 21 becomes flat accordingly. Therefore, even if the friction material 302 wears, it contacts the flat part of the elastic body 21 where the initial wear has ended, so smooth rotation and quietness can be maintained. If the elastic body 21 is softer and more likely to wear than the friction member 302, it will wear into a groove and the friction member 302 will get stuck in the groove, causing an obstruction to smooth rotation. In this embodiment, the friction member 302 is formed into a desired shape by pressing a plate material of SUS420j2, and then hardened. The hardness is about 580 Hv in Vickers hardness, and the root mean square roughness Rq of the first contact part 302a and the first non-contact part 302b before the initial wear occurs was 0.213 μm. In addition, the elastic body 21 is made of a steel-based material and has been subjected to nitriding treatment, and no treatment to improve the surface quality to a smooth state, such as lapping, which leads to increased costs, has been performed. The surface hardness of the elastic body is about 1100 Hv in Vickers hardness, and the root mean square roughness Rq of the second contact portion 21a and the second non-contact portion 21b before the occurrence of initial wear is 0.461 μm. When observing several motors, it was found that the hardness of the first contact portion 302a and the first non-contact portion before the occurrence of initial wear and the root mean square roughness of the second contact portion and the second non-contact portion before the occurrence of initial wear are in a good relationship of 4 <= 5, and the root mean square roughness is 2 <= 2.5. The nitriding treatment may be salt bath nitriding, gas nitriding, ion nitriding, or any other treatment. The nitriding treatment causes nitrogen to penetrate and diffuse into the surface layer of the part to harden it, so a hardness difference occurs between the surface layer and the base material. Therefore, if it wears beyond the hardened layer, the wear progresses at an accelerated rate, so it is preferable that the friction member 302 has a low hardness and is relatively easy to wear.

The first friction part may be configured to fit inside and/or outside the support part in the radial direction of the annular contact body. The first friction part may be made of an annular wire.

The contact body 300 contacts the vibrating body 20 at the friction surface 302a, and the support part 301b functions as a contact spring. Variations in the spring stiffness of the contact spring cause abnormal noise (ringing) of the vibration actuator. Therefore, it is preferable that the support part 301b, which is a contact spring, is made of a material with a low Young's modulus, such as aluminum alloy or brass, so that variations in spring stiffness do not occur even if there is a processing error. On the other hand, since the friction member 302 is in frictional contact with the vibrating body 20, it is preferable that the material be steel or the like, which has a lower hardness than the elastic body 21 but is highly wear-resistant. Generally, highly wear-resistant materials such as steel are harder and have a higher Young's modulus than materials such as aluminum alloy or brass. In other words, it is preferable that the Young's modulus of the material constituting the support part 301b is lower than that of the material constituting the friction member 302.

In addition, the base portion 301a comes into contact with the vibration-damping rubber 41, which has a damping effect to suppress abnormal noise from the vibration actuator.

The materials and processing methods of the main body member 301 and the friction member 302 will be described. The friction member 302 is preferably made of a material with high wear resistance, and can be manufactured by pressing and hardening using a plate material of a steel material such as stainless steel. On the other hand, the main body member 301 is required to have a vibration damping function, so it is preferably made of a material with high damping properties and a free-cutting material that can be processed with high precision, and can be manufactured by cutting using an aluminum alloy or brass that is more free-cutting than the friction member 302. The main body member 301 may be surface-treated, and if it is an aluminum alloy, it may be anodized. The manufacturing method of the friction member 302 and the main body member 301 is not limited to the above-mentioned methods. The processing method of the friction member 302 may be laser processing, electric discharge processing, cutting, etching, or a combination of these. In addition, the heat treatment of the friction member 302 may be nitriding, carburizing, or the like, or a hardening treatment such as plating other than heat treatment. Possible methods for processing the main body member 301 include die casting, forging, or a combination of these.

The assembly of the main body member 301 and the friction member 302 will be described. The main body member 301 has high component rigidity and can therefore be manufactured with higher precision than the friction member 302. In particular, in a camera head or robot hand that requires high positioning precision, a high degree of flatness is required for the contact surface between the contact body and the vibrating body to ensure smooth operation. The main body member 301 has high component rigidity and therefore the surface 301c that comes into contact with the vibrating body 20 can have a high degree of flatness.

On the other hand, the friction member 302 is subject to large distortion during manufacturing processes such as press working and hardening. However, since the friction member 302 has low rigidity as a component, it can be easily deformed elastically. Therefore, the friction surface 302a becomes highly flat as the friction member 302 is elastically deformed using the highly accurate main body member 301 as a reference.

In this embodiment, the friction member 302 is subjected to a chemical polishing process after hardening, and no smoothing process such as lapping is performed. The manufacturing method of the friction member 302 is described above, but smoothing processes such as lapping are performed to remove cutting marks and burrs generated during pressing, and smooth rotation and quietness are obtained, and the fact that this process takes time leads to increased costs. Chemical polishing can remove cutting marks and burrs in a short time, and smooth rotation and quietness can be obtained by obtaining a smooth surface texture. In addition, it is not limited to chemical polishing, and electrolytic polishing may be used. Chemical polishing and electrolytic polishing may be performed by modifying the surface with a phosphoric acid or sulfuric acid solution. Another method for smoothing the surface texture is buff polishing. Since it is polished with a soft cloth-like material, it is possible to obtain a smooth surface texture even for parts with curvature. Since the surface 301c on the side that contacts the vibration body 20 has a high flatness in this way, the friction member 302 that follows it can obtain a smooth surface texture and high flatness while maintaining the curvature without performing a process such as lapping, which takes a long time to process.

In addition, it is preferable to connect the main body member 301 and the friction member 302 by gluing or bonding to avoid friction between metals. This makes it possible to suppress abnormal noise (ringing) from the vibration actuator.

5 is a diagram showing an example of a modified example of this embodiment. The contact body 310 has a main body member 311 and a friction member 312 that is a separate member from the main body member 311. The main body member 311 has a base portion 311a and a support portion 311b that has an L-shaped end cross section extending in the radial direction of the contact body 310, and is configured in an annular shape. The friction member 312 has a first friction portion 312a that contacts the elastic body 21 (not shown), a first non-contact portion 312b that is adjacent to the first friction portion 312a and does not contact the elastic body 21, and a fitting portion 312c that extends in a direction along the central axis of the contact body 310 and fits into the support portion 311b. The first friction portion and the first non-contact portion may be configured as a single continuous member. The first friction portion and the first non-contact portion may also form a curved surface along the radial direction of the annular contact body.

The friction member 312 may be significantly distorted during manufacturing processes such as press working and hardening. However, since the friction member 312 has low rigidity as a part, it can be easily elastically deformed. Therefore, the friction member 312 is elastically deformed using the support portion 311b of the highly accurate main body member 311 as a reference while the fitting portion 312c is fitted to the inner diameter. This makes it possible to maintain a high degree of flatness of the friction surface 312a, suppress misalignment of the friction member 312, and improve the roundness of the friction surface 312a. The same effect can be obtained with an outer diameter fitting as shown in Figure 6.

Figure 7 is a diagram showing an example of a modified example of this embodiment. The contact body 320 has a main body member 321 and a friction member 322 that is a separate member from the main body member. The main body member 321 has a groove 321c on the surface facing the elastic body 21 (not shown), and a holding portion 321d is provided on both sides of the groove 321c. The friction member 322 is arranged on the holding portion 321d in a double-supported beam shape, so that the friction member 322 has the function of a contact spring. Since the friction member 322 has the function of a contact spring, the stiffness of the contact spring can be adjusted by changing the plate thickness of the friction member 322 and the groove 321c. The friction member 322 has a curved portion having a first friction portion that contacts the second friction portion and a first non-contact portion, and by obtaining a smooth surface property by chemical polishing or the like, smooth rotation and quietness can be realized.

Figure 8 is a diagram showing an example of a modified example of this embodiment. The main body member 331 has a base portion 331a and a support portion 331b extending in the radial direction of the contact body 330. A V-shaped groove 331e is formed on the surface of the support portion 331b that contacts the elastic body 21 (not shown) at the tip of the support portion 331b, and a linear friction member 332 is fitted and joined into the V-shaped groove 331e. In this embodiment, a friction member 332 made of SUS420j2 wire is used, which is made into a ring by welding both ends of the wire, but the wire may be joined by adhesion, diffusion bonding, etc. Also, the wire may be fitted into the V-groove 331c without being joined at both ends. The groove may be rectangular or U-shaped other than V-shaped, but a V-shape is preferable because it is easy to position. In this way, smooth rotation and quietness can be achieved even if the side of the wire that has been given a smooth surface property by chemical polishing or the like is used as a friction member. In Figure 9, the cross section of the tip of the support portion 331b is L-shaped, and a linear friction member 332 is fitted into the outer diameter side of the L-shaped tip. A similar effect can be achieved in this form.

Figure 10 shows an example of a modified version of this embodiment. In this embodiment, the main body member 341 and the friction member 342 are integrated. Therefore, the entire contact body 340 is made of hardened SUS420j2, which has high wear resistance. Since it is manufactured by cutting, cutting marks remain on the first friction part, but by performing chemical polishing in a later process, the surface properties become smooth, making it possible to achieve smooth rotation and quiet operation.

Second Embodiment
In the second embodiment, a configuration of a camera platform for an imaging device such as a surveillance camera will be described as an example of a device including the vibration actuator 10 described in the first embodiment.

In this embodiment, a pan head equipped with a rotating table and a vibration actuator provided on the rotating table is described below.

Figure 6 is a diagram showing the schematic configuration of a pan head 800 and an imaging device 840 mounted on the pan head 800. The pan head 800 includes a base 820, a head 810 equipped with two vibration actuators 870 and 880, and an L-angle 830 for fixing the imaging device 840. The vibration actuator 880 provided on the pan axis is an actuator for rotating the head 810, the L-angle 830, and the imaging device 840 around the pan axis relative to the base 820. The vibration actuator 870 provided on the tilt axis is an actuator for rotating the L-angle 830 and the imaging device 840 around the tilt axis relative to the head 810.

By using two vibration actuators 870, 880 in the camera head 800, it is possible to change the orientation of the imaging device 840 quickly, with high response, quietly, and with high precision. In addition, since the vibration actuator has a high holding torque even when not energized, the orientation of the imaging device 40 can be maintained without consuming power from the vibration actuator even if the center of gravity of the imaging device 840 shifts around the tilt axis.

In addition, it is possible to provide an electronic device that includes a component desired by a user of the present invention and a vibration actuator attached to that component.

REFERENCE SIGNS LIST 10 vibration type actuator 20 vibrating body 21 elastic body 21a second contact portion 21b second non-contact portion 22 piezoelectric element 100 power supply member 300, 310, 320, 330, 340 contact body 301, 311, 321, 331, 341 main body member 301a, 311a, 331a, 341a base portion 301b, 311b, 331b, 341b support portion 321c groove 321d holding portion 331e V-shaped groove 302, 312, 322, 332, 342 friction member 302a, 312a, 322a, 332a, 342a first contact portion 302b, 312b, 322b, 332b, 342b First non-contact part 312c fitting part

Claims (18)

A vibrating body having an annular elastic body and an electromechanical energy conversion element;
a ring-shaped contact body that contacts the vibrating body,
the contact body has a first friction portion in contact with the vibration body and a first non-contact portion adjacent to the first friction portion and not in contact with the vibration body,
the elastic body has a second friction portion in contact with the first friction portion and a second non-contact portion adjacent to the second friction portion and not in contact with the contact body,
The first friction portion has a lower hardness than the second friction portion, and the first non-contact portion has a smaller root mean square roughness than the second non-contact portion. the contact body has a base portion and a support portion extending annularly along a radial direction of the annular contact body connecting the base portion and the first friction portion,
2. The vibration actuator according to claim 1, wherein the first friction portion is provided at an end of the support portion. The vibration actuator according to claim 2, wherein the first friction portion is a separate member from the base portion and the support portion. The vibration actuator according to any one of claims 1 to 3, wherein the first friction portion and the first non-contact portion are a single continuous member. The vibration actuator according to claim 4, wherein the first friction portion and the first non-contact portion have a curvature in the radial direction of the annular contact body. The vibration actuator according to claim 5, wherein the first friction portion and the first non-contact portion form a curved surface along the radial direction of the annular contact body. the annular elastic body includes a surface layer including the second friction portion and a base material adjacent to the surface layer,
7. The vibration actuator according to claim 1, wherein the surface layer has a hardness higher than a hardness of the base material. The first friction portion is held by the support portion, and both ends of the first friction portion in the radial direction of the annular contact body are
4. The vibration actuator according to claim 3, further comprising a portion that is not in contact with either the contact body or the vibrating body. The first friction portion is disposed relative to the support portion in a radial direction of the annular contact body.
4. The vibration actuator according to claim 3, which is internally fitted and/or externally fitted. The vibration actuator according to claim 3, wherein the first friction portion has a curved portion that contacts the second friction portion. 7. The vibration actuator according to claim 2, wherein the contact body has a groove having a V-shaped cross section in the radial direction, and the first friction portion is received in the groove. The vibration actuator according to claim 3, wherein the first friction part is a ring-shaped wire. The vibration actuator according to claim 4, wherein the first friction portion is integral with the base portion of the contact body. A step of obtaining a vibrating body using an annular elastic body and an electromechanical energy conversion element;
a step of subjecting the annular member to chemical polishing, electrolytic polishing, or buff polishing to obtain an annular contact body;
A method for producing a vibration actuator, comprising the steps of obtaining the vibration actuator according to claim 1 by using the vibrating body and the contact body. The method for manufacturing a vibration actuator according to claim 14, wherein the chemical polishing and electrolytic polishing are performed by surface modification using a phosphoric acid or sulfuric acid solution. A pan head comprising a rotating table and a vibration actuator according to any one of claims 1 to 13 provided on the rotating table. An electronic device comprising a member and a vibration actuator according to any one of claims 1 to 13 provided on the member. An apparatus comprising: a lens; and the vibration actuator according to claim 1 for moving the lens.

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