JP4721558B2 - Ultrasonic motor device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ultrasonic motor device (hereinafter also referred to as a piezo motor device). More specifically, the present invention relates to a stator fixing structure.
[0002]
[Prior art]
An ultrasonic motor (piezomotor) is divided into two types, a standing wave motor and a traveling wave motor, which are symmetrical excitation modes with a fixed center of gravity of the vibrator, and a disc or cylinder that is a vibrator divided into, for example, four parts. There is known an electrostrictive rotator type motor in which the center of gravity rotates around the center when excited by an asymmetric mode in which the amplitude of the rotation is reversed, and the outer periphery of the circle is eccentric like a hula hoop. Such an ultrasonic motor (hereinafter also referred to as a piezo motor) applies a high-frequency AC voltage to a piezoelectric element serving as a stator to generate ultrasonic vibration of about 20 kHz or more, thereby rotating the rotor pressed against the stator. ing. This type of piezo motor has the advantages that it is simple in structure and suitable for reduction in size and weight, and that it can obtain high torque even during low-speed rotation, and is quiet with little drive noise. In particular, the latter electrostrictive revolving rotator type motor generates 3D revolving torque in which axial mode is coupled in addition to the diameter and circumferential direction of the cylindrical revolving rotator as disclosed in Japanese Patent Laid-Open No. 10-272420. It has the feature that it can be used as a child.
[0003]
[Problems to be solved by the invention]
The piezo motor takes out a driving torque by rotating the rotor by pressing the rotor against a sliding surface of a stator that excites ultrasonic vibrations. The rotor has a structure that is pressed against the sliding surface of the stator with an appropriate pressure. On the other hand, the stator itself needs to be stably supported and fixed to the surrounding frame members. However, it is not preferable to firmly fix the stator to the frame member because the vibration of the stator is hindered. Further, since the stator is usually made of a piezoelectric element such as ceramic, there is a risk of damage if it is directly tightened into the frame member with a screw or the like. In some cases, it may be damaged by an external impact.
[0004]
Therefore, the stator needs to be fixed to the frame member with a certain degree of freedom so as not to inhibit vibration. However, if the degree of freedom is too high, problems such as rotation of the stator itself and lack of positional accuracy with respect to the rotor occur. Therefore, a structure has been proposed in which the stator is held on the frame member by an elastic force. For example, using a coil spring, one end is soldered to the surface electrode of the stator, and the other end is fixed to the frame member. However, the stator holding mechanism using such soldering and coil springs is complicated, and the assemblability and workability are poor.
[0005]
[Means for Solving the Problems]
SUMMARY OF THE INVENTION In view of the above-described problems of the prior art, an object of the present invention is to provide a support fixing structure for a stator that can protect a piezo motor from external impacts and can stably operate. The following measures were taken in order to achieve this purpose. That is, the present invention relates to a stator made of a cylindrical piezoelectric element that generates a revolving torque on a cylindrical end surface, a rotor that is slidably pressed against the cylindrical end surface, and that rotates by the revolving torque, and the stator. A piezo motor apparatus comprising: a frame member having a cylindrical inner peripheral surface disposed so as to surround a cylindrical outer peripheral surface of the cylindrical member; and a resilient member for elastically supporting and fixing the stator to the frame member. The elastic member is a plate spring interposed between the cylindrical outer peripheral surface of the stator and the cylindrical inner peripheral surface of the frame member, and a part of the plate spring is fixed to the cylindrical inner peripheral surface of the frame member. The other part is in pressure contact with the cylindrical outer peripheral surface of the stator. Preferably, an electrode is formed on a cylindrical outer peripheral surface of the stator, and the leaf spring also serves as a connection terminal for pulling out the electrode to the outside. Further, the leaf spring has a convex curved surface formed at the portion that is pressed against the cylindrical outer peripheral surface of the stator. The stator is supported and fixed to the inside of the frame member by pushing the portion of the leaf spring located radially inward from the outer peripheral surface of the cylinder to the outside in the radial direction.
[0006]
The present invention also includes a stator formed of a cylindrical piezoelectric element that generates a revolving torque on a cylindrical end face, a rotor that is slidably pressed against the cylindrical end face, and that rotates by the revolving torque, In a piezo motor apparatus comprising an inner peripheral surface arranged to surround a cylindrical outer peripheral surface and housing the stator, and an elastic member elastically supporting and fixing the stator to the frame member, The elastic member is made of an elastic adhesive disposed between a cylindrical outer peripheral surface of the stator and an inner peripheral surface of the frame member. Preferably, the elastic adhesive is distributed at a plurality of locations in a discrete manner in the circumferential direction of the cylindrical outer peripheral surface of the stator. Further, the frame member has a positioning portion that abuts on the cylindrical outer peripheral surface of the stator and restricts its radial position.
[0007]
According to one aspect of the present invention, a leaf spring is disposed between the cylindrical outer peripheral surface of the stator and the cylindrical inner peripheral surface of the frame member surrounding the stator to elastically support and fix the stator. Thereby, a stator can be protected from an external impact. Further, the rotation and movement of the stator itself can be suppressed, and the stator can be accurately positioned with respect to the rotor. Further, this plate member can be used as an electrical connection terminal for the surface electrode of the stator. According to another aspect of the present invention, an elastic adhesive is disposed between the cylindrical outer peripheral surface of the stator and the inner peripheral surface of the frame member surrounding the stator to elastically support and fix the stator. Since an elastic adhesive such as silicon rubber is used, it can be securely supported and fixed without hindering the vibration of the stator. Impact applied from the outside can be absorbed by the elastic adhesive, and the stator itself is not damaged.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram showing a first embodiment of a piezo motor device according to the present invention, where (A) represents a cross-sectional shape and (B) represents a side surface shape. As shown in the figure, this piezo motor device is an electrostrictive revolving rotator type motor composed of a 3D revolving torque resonator disclosed in Japanese Patent Laid-Open No. 10-272420 described above, and includes a stator 1, a rotor 2, and a frame member 6. And an elastic member. The stator 1 is composed of a cylindrical piezoelectric element and generates a revolving torque on the end face of the cylinder. As shown in FIG. 5B, the rotor 2 is slidably pressed against the cylindrical end surface of the stator 1 and rotates by the revolution torque. In the illustrated example, the rotor 2 is mounted on the receiving plate 7. The receiving plate 7 is attached to the bottom of the frame member 6. The frame member 6 has a cylindrical inner peripheral surface disposed so as to surround the cylindrical outer peripheral surface of the stator 1 and accommodates the stator 1.
[0009]
As a feature of the present invention, an elastic member is used to elastically support and fix the stator 1 to the frame member 6. Specifically, the elastic member includes plate springs 61, 62, 63, 64 interposed between the cylindrical outer peripheral surface of the stator 1 and the cylindrical inner peripheral surface of the frame member 6. Each of the leaf springs 61, 62, 63, 64 is fixed to the cylindrical inner peripheral surface of the frame member 6, and the other part is pressed against the cylindrical outer peripheral surface of the stator 1. With this configuration, the stator 1 can be accurately positioned and fixed with respect to the frame member 6. Since the leaf springs 61 to 64 are used for support and fixation, the rotor 2 can be rotated without hindering the vibration of the stator 1. Further, externally applied impacts are absorbed by the leaf springs 61 to 64 and are not transmitted to the stator 1 made of ceramics or the like.
[0010]
For example, four divided electrodes 11, 12, 13, and 14 are formed on the cylindrical outer peripheral surface of the stator 1. An electrode 10 is also formed on the entire inner circumferential surface of the stator 1. The leaf springs 61 to 64 also serve as connection terminals for extracting the electrodes 11 to 14 to the outside. That is, four-phase drive voltages A, AX, B, and BX are applied to the leaf springs 61 to 64 from the outside, and the stator 1 vibrates accordingly. As described above, in this embodiment, the leaf springs 61 to 64 are used as mechanical parts for holding and fixing the stator 1 and also serve as electrical connection terminals, which is advantageous in terms of cost.
[0011]
FIG. 2 is a cross-sectional view showing an improved example of the first embodiment shown in FIG. 1, (A) shows a state after the stator 1 is incorporated in the frame member, and (B) shows the frame member 6. The state before incorporating the stator 1 in FIG. As shown to (A), as for each leaf | plate spring 61-64, the edge part press-contacted to the cylindrical outer peripheral surface of the stator 1 is each processed into the convex curve shape (R). In this manner, the vibration loss of the stator 1 is suppressed by reducing the contact area of the leaf springs 61 to 64 with the outer peripheral surface of the stator 1. In the drawing, for easy understanding, illustration of electrodes formed on the front surface and the back surface of the stator 1 is omitted.
[0012]
As shown in (B), in a state where the stator 1 is not assembled, the tips of the leaf springs 61 to 64 protrude radially inward inside the frame member 6. In this state, the stator 1 is supported and fixed inside the frame member 6 by pushing the tips R of the leaf springs 61 to 64 positioned radially inward from the outer peripheral surface of the cylinder to the outside in the radial direction. By simply inserting the stator 1 into the frame member 6, the stator 1 can be automatically positioned, leading to simplification of the assembly process. The leaf springs 61 to 64 are made of phosphor bronze, for example. Or you may use the leaf | plate spring which gave the gold plating to the surface of stainless steel material.
[0013]
FIG. 3 shows an application example of the piezo motor device shown in FIG. 1, and shows a lens driving device for a camera using the piezo motor device as a power source. Needless to say, the application example of the piezoelectric motor device according to the present invention is not limited to the camera lens driving device. This lens driving device for a camera is basically composed of a piezo motor including a stator 1 and a rotor 2, a lens barrel 3, and a transmission member for connecting them. The stator 1 is composed of a piezoelectric element, receives an alternating voltage, and excites ultrasonic vibrations to generate revolution torque. The rotor 2 is in pressure contact with the stator 1 and rotates by a revolving torque. The lens barrel 3 is mounted with a camera lens (not shown) and is linearly displaceable in the optical axis Z direction of the lens. The stator 1, the rotor 2, and the lens barrel 3 are incorporated in a frame member 6. The rear end of the frame member 6 in the optical axis Z direction is shielded by the receiving plate 7. A transmission member that connects the rotor 2 of the piezo motor and the lens barrel 3 converts the rotation of the rotor 2 into a linear displacement of the lens barrel 3 and transmits it.
[0014]
The stator 1 is composed of a cylindrical piezoelectric element having a cylindrical axis parallel to the optical axis Z. On the other hand, the lens barrel 3 is disposed on the inner side of the cylindrical stator 1, and can advance and retreat from the front end of the frame member 6 along the optical axis Z. In this way, by arranging the lens barrel 3 inside the cylindrical stator 1, it is possible to reduce the size of the camera lens driving device.
[0015]
In this embodiment, the transmission member that connects the rotor 2 and the lens barrel 3 includes a helicoid cylinder 4 that is integrated with the lens barrel 3. However, the lens barrel 3 and the helicoid cylinder 4 do not necessarily have to be integrally formed. In some cases, the lens barrel 3 may be incorporated into the helicoid cylinder 4 later. The helicoid cylinder 4 is basically cylindrical so that the lens barrel 3 is accommodated therein, and a screw 41 is cut on the outer peripheral surface thereof. A stopper 42 is attached to the front end of the helicoid cylinder 4 to prevent the rotation of the helicoid cylinder 4 itself, and is engaged with the frame member 6. As a result, the helicoid cylinder 4 performs a linear motion along the optical axis Z direction. The transmission member further includes a helicoid gear 5 connected to the rotor 2 and screwed into the helicoid cylinder 4. In this embodiment, the rotor 2 made of an annular metal and the helicoid gear 5 made of a resin such as polycarbonate are connected by a key groove on the rotor 2 side and a key 52 on the helicoid gear 5 side. As the rotor 2 rotates, the helicoid gear 5 also rotates. The helicoid gear 5 has a screw 51 cut on its inner peripheral surface. A screw 41 formed on the outer peripheral surface of the helicoid cylinder 4 and a screw 51 formed on the inner peripheral surface of the helicoid gear 5 mesh with each other. When the helicoid gear 5 rotates as the rotor 2 rotates, the helicoid cylinder 4 is linearly displaced along the optical axis Z. The rotor 2 is attached to the rear end of the cylindrical stator 1. A rotation assisting means 8 is arranged between the receiving plate 7 and the rotor 2, and the rotor 2 is slidably pressed against the rear end of the stator 1, and the revolution torque of the stator 1 is used as the rotation motion of the rotor 2. Take out. The rotation assisting unit 8 includes a bearing 81 that contacts the rotor 2, a pressing plate 82 that holds the bearing 81, and a coil spring 83 that pressurizes the pressing plate 82 toward the rotor 2.
[0016]
In such a configuration, leaf springs 62 and 63 are interposed between the frame member 6 and the stator 1. The stator 1 is elastically supported and fixed to the frame member 6 by these plate springs 62 and 63. Further, the leaf springs 62 and 63 also serve as connection terminals for the electrodes of the stator 1. A driving voltage is applied to the surface electrode of the stator 1 via the leaf springs 62 and 63, and the stator 1 excites ultrasonic vibration. At that time, since the stator 1 is elastically held by the leaf springs 62 and 63, there is no possibility that the vibration is hindered. The revolution torque generated on the cylindrical end surface of the stator 1 is converted into a rotational motion by the rotor 2 slidably pressed against the cylindrical end surface.
[0017]
4A and 4B are schematic views showing a second embodiment of the piezoelectric motor device according to the present invention, in which FIG. 4A shows a cross-sectional shape and FIG. 4B shows a vertical cross-sectional shape. For easy understanding, portions corresponding to the application example shown in FIG. 3 are denoted by corresponding reference numerals. This piezo motor apparatus basically includes a stator 1, a rotor 2, a frame member 6, and an elastic member. The stator 1 is formed of a cylindrical piezoelectric element and generates a revolving torque on the cylindrical end surface. The rotor 2 is slidably pressed against the end surface of the cylinder and rotates by a revolving torque. The frame member 6 has an inner peripheral surface disposed so as to surround a cylindrical outer peripheral surface of the stator 1 and accommodates the stator 1.
[0018]
An elastic member is used to elastically support and fix the stator 1 to the frame member 6. In this embodiment, an elastic adhesive 6 </ b> S such as silicon rubber is used as the elastic member, and is disposed between the cylindrical outer peripheral surface of the stator 1 and the inner peripheral surface of the frame member 6. The elastic adhesive 6S is dispersed in the circumferential direction of the cylindrical outer peripheral surface of the stator 1 and is uniformly arranged at a plurality of locations (three locations in the illustrated example). The frame member 6 has a positioning portion 6G that abuts on the cylindrical outer peripheral surface of the stator 1 and regulates its radial position. In the present embodiment, the elastic adhesive 6S just described above is disposed on the positioning portion 6G that protrudes inward in the radial direction of the frame member 6.
[0019]
Thus, in this embodiment, the outer periphery of the stator 1 is positioned by the frame member 6, and the stator 1 and the frame member 6 are bonded to each other using an elastic adhesive 6S such as silicon rubber. The outer periphery of the stator 1 is positioned by the inner diameter of the frame member 6. Since the vibration of the stator 1 is very small, the positioning of the stator 1 with the positioning portion 6G of the frame member 6 can be performed with very high accuracy. And since the stator 1 is adhere | attached on the frame member 6 with the silicon-type elastic adhesive agent 6S, it can fix reliably, without inhibiting the vibration of the stator 1. FIG. Therefore, the stator 1 itself does not rotate.
[0020]
FIG. 5 is a schematic perspective view showing the appearance of the piezo motor shown in FIG. 3 or FIG. 3, four-phase AC drive voltages A, B, AX, BX are applied to the surface electrodes 11, 12,... Of the stator 1 via a leaf spring. It will be. On the other hand, in the piezo motor shown in FIG. 4, in addition to an elastic adhesive provided for supporting and fixing, a flexible substrate for taking out electrodes is used to generate four-phase AC drive voltages A, B, AX, and BX. This is applied to the surface electrodes 11, 12, 13, 14 of the stator 1. As shown in the figure, the piezo motor is composed of a cylindrical stator 1 and an annular rotor 2 pressed against the rear end thereof. Electrodes 11, 12, 13, and 14 are formed on the outer peripheral surface of the cylindrical stator 1. Although not shown, electrodes are also formed on the inner peripheral surface of the cylinder. The electrodes formed on the outer peripheral surface of the cylinder are divided into four parts, and AC drive voltages A, B, AX, and BX having different phases are applied thereto. A phase voltage and B phase voltage are 90 degrees out of phase with each other. The phase of the A phase voltage and the AX phase voltage is 180 degrees different. In other words, the A phase and the AX phase have opposite polarities. Similarly, the B phase and the BX phase have opposite polarities.
[0021]
6 is a schematic cross-sectional view of the stator shown in FIG. As shown in the drawing, an electrode 10 for applying a reference potential is formed on the entire inner peripheral surface of a cylindrical stator 1 made of a piezoelectric element such as ceramic. Four driving electrodes 11 to 14 are formed on the outer circumferential surface of the cylinder. Four-phase AC voltages A, B, AX, and BX having phases shifted from each other by 90 degrees are applied to the four-divided electrodes 11 to 14, respectively.
[0022]
The operation of the piezo motor shown in FIGS. 5 and 6 will be described with reference to FIG. In the piezo motor, since the ultrasonic vibration as a power source has a constant resonance frequency, the current has a substantially constant value. The resonator has a high Q, and the rise of the vibration amplitude is considered to be within one cycle, and can be regarded as a non-inertia mechanism. The current changes only within the range where the inertia of the load affects. Various configurations of piezo motors having such characteristics have been developed, but the electrostrictive revolution type is particularly effective. The electrostrictive revolution type uses a resonator that can directly excite a uniform revolution torque over the entire peripheral surface, instead of changing the vibration into torque as in the prior art. There are two types of conventional ultrasonic transducers, standing wave type and traveling wave type, but both can be excited only in a symmetric mode with a fixed center of gravity. On the other hand, when the cylinder is excited in a mode in which left and right expansion and contraction are reversed, the center of gravity vibrates away from the center. When this asymmetric excitation is performed, a cylindrical resonance mode that cannot be observed with the conventional symmetrical excitation can be obtained. Therefore, when the electrodes of the stator cylinder are divided into, for example, four parts and excited by a rotating electric field having a phase difference of 90 degrees, resonance of a mode in which the center of gravity rotates around the center is seen as shown in FIG. At this time, the outer periphery of the cylinder is decentered like a hula hoop while maintaining the original shape, so that the vibrator rotates and revolves. The electrostrictive revolving rotator type motor having such a configuration can be used as a 3D revolving torque generator in which a direct rotation mode is excited and an axial mode is combined in addition to the diameter and circumferential direction of the cylindrical revolving element. This torque is extracted directly as the rotation of the rotor.
[0023]
FIG. 8 is a waveform diagram of the A-phase, B-phase, AX-phase, and BX-phase voltages applied to each of the quarterly divided stator electrodes. As shown in the figure, the B phase is shifted by 90 degrees relative to the A phase, the AX phase is shifted by 180 degrees, and the BX phase is shifted by 270 degrees. In this way, a rotating electric field is formed by applying alternating voltages having different phases by 90 degrees to the stator, and the stator directly excites the rotation mode in response to this.
[0024]
Finally, FIG. 9 shows a drive circuit for the piezo motor. As shown in the figure, a pair of drive signals A and AX are applied to a pair of electrodes facing each other of the stator 1 via an H bridge A. Similarly, the other pair of signals B and BX are also applied to the other pair of stator electrodes facing each other via the H bridge B. The H bridge is a driver circuit for supplying a sufficient output current to the stator electrode in response to each input signal.
[0025]
【The invention's effect】
As described above, according to the first aspect of the present invention, the stator is fixed to the frame member by using a leaf spring, and can be supported without hindering the vibration of the stator, and against an external impact. The stator can be protected. Furthermore, using both the support fixing mechanism for the stator and the electrode extraction mechanism is advantageous in terms of cost. In addition, according to the second aspect of the present invention, the stator can be held and fixed without inhibiting the vibration of the stator by attaching the stator to the frame member using an elastic adhesive such as silicon rubber. In particular, by positioning the outer periphery of the stator using the inner diameter of the frame member, a highly accurate stator holding mechanism can be obtained.
[Brief description of the drawings]
FIG. 1 is a schematic plan view and a side view showing a first embodiment of a piezo motor device according to the present invention.
FIG. 2 is a schematic plan view showing a modification of the piezo motor device shown in FIG.
FIG. 3 is a schematic longitudinal sectional view showing a camera lens driving device incorporating the piezo motor device shown in FIG. 1;
FIGS. 4A and 4B are a schematic transverse sectional view and a longitudinal sectional view showing a second embodiment of a piezo motor device according to the present invention. FIGS.
FIG. 5 is a schematic perspective view showing an appearance of a piezo motor device according to the present invention.
FIG. 6 is a cross-sectional view of a piezo motor device according to the present invention.
FIG. 7 is a schematic diagram for explaining the operation of the piezoelectric motor device according to the present invention.
FIG. 8 is a waveform diagram for explaining the operation of the piezoelectric motor device according to the present invention.
FIG. 9 is a drive circuit diagram of a piezo motor device according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Stator, 2 ... Rotor, 6 ... Frame member, 6G ... Positioning part, 6S ... Elastic adhesive, 7 ... Receiving plate, 11 ... Electrode, 12 ... -Electrode, 13 ... Electrode, 14 ... Electrode, 61 ... Leaf spring, 62 ... Leaf spring, 63 ... Leaf spring, 64 ... Leaf spring

Claims (7)

A stator composed of a cylindrical piezoelectric element that generates a revolving torque on a cylindrical end surface, a rotor that is slidably pressed against the cylindrical end surface, and that rotates by the revolving torque, and surrounds a cylindrical outer peripheral surface of the stator In a piezo motor apparatus comprising a frame member having a cylindrical inner peripheral surface arranged in this manner and housing the stator, and an elastic member elastically supporting and fixing the stator to the frame member,
The elastic member comprises a leaf spring interposed between the cylindrical outer peripheral surface of the stator and the cylindrical inner peripheral surface of the frame member,
An ultrasonic motor device according to claim 1, wherein a part of the leaf spring is fixed to the cylindrical inner peripheral surface of the frame member, and the other part is pressed against the cylindrical outer peripheral surface of the stator. 2. The ultrasonic motor device according to claim 1, wherein an electrode is formed on a cylindrical outer peripheral surface of the stator, and the leaf spring also serves as a connection terminal for pulling out the electrode to the outside. 2. The ultrasonic motor device according to claim 1, wherein a portion of the leaf spring that is in pressure contact with a cylindrical outer peripheral surface of the stator is processed into a convex curved surface shape. 2. The ultrasonic wave according to claim 1, wherein the stator is supported and fixed inside the frame member by pressing a portion of the leaf spring located radially inward from the outer peripheral surface of the cylinder to the outside in the radial direction. Motor device. A stator composed of a cylindrical piezoelectric element that generates a revolving torque on a cylindrical end surface, a rotor that is slidably pressed against the cylindrical end surface, and that rotates by the revolving torque, and surrounds a cylindrical outer peripheral surface of the stator In an ultrasonic motor device comprising a frame member having an inner peripheral surface arranged like this and housing the stator, and an elastic member elastically supporting and fixing the stator to the frame member,
The ultrasonic motor device according to claim 1, wherein the elastic member is made of an elastic adhesive disposed between a cylindrical outer peripheral surface of the stator and an inner peripheral surface of the frame member. 6. The ultrasonic motor device according to claim 5, wherein the elastic adhesive is dispersed in a plurality of locations in a circumferential direction of a cylindrical outer peripheral surface of the stator. The ultrasonic motor device according to claim 5, wherein the frame member has a positioning portion that abuts on a cylindrical outer peripheral surface of the stator and regulates a radial position thereof.

Images