JPH04308481A - Piezoelectric motor - Google Patents

Abstract

PURPOSE:To provide a piezoelectric motor which produces driving force positively. CONSTITUTION:The piezoelectric motor comprises a cantilever driving shaft 16, a plurality of piezoelectric elements 19 disposed around the driving shaft 16 and applied with voltages having different phase order, and an output section 25 disposed at the open end of the driving shaft 16 and taking out vibration of the driving shaft 16 in the form of rotational motion. The output section 25 comprises a drive gear 23 of internal tooth and a driven gear 13 of external tooth wherein the number of teeth of the driven gear 13 is set smaller than that of drive gear.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small motor used in electronic equipment, and more particularly to a piezoelectric motor that generates high torque at low speed rotation.

0002

[Prior Art] Compared to conventional electromagnetic motors, piezoelectric motors can obtain high torque at low rotation speeds and do not generate electromagnetic noise, so they are used for camera autofocus, etc. It's being used. The basic driving principle of such a piezoelectric motor is that a piezoelectric element that generates elliptical motion is used as a stator, and a rotor that is pressed against the stator generates rotational motion through frictional force. An example of a conventional device having such a configuration is shown in FIG. The piezoelectric motor shown in the figure is a combination of a bolt tightening vibrator 1 that generates torsional vibration and a laminated piezoelectric displacement element 2. The combination of the movements of the two causes an elliptical movement at the upper end of the laminated piezoelectric displacement element 2. This generates rotational torque for the rotor 3 which is in pressure contact with the laminated piezoelectric displacement element 2. Note that the reference numeral 4 in the figure is a resonant metal block.

0003

[Problems to be Solved by the Invention] However, in the above-mentioned conventional piezoelectric motor, etc., even if the laminated piezoelectric displacement element 2 is used, it is difficult to obtain an amplitude sufficient to reliably rotate the rotor 3. It remained unresolved. Therefore, an object of the present invention is to provide a piezoelectric motor that can obtain reliable driving force.

0004

[Means for Solving the Problems] The structure of the present invention as set forth in claim 1 to achieve the above object includes a drive shaft supported in a cantilevered manner, and a portion near a fixed end of the drive shaft. It is equipped with a plurality of drive elements arranged around the drive shaft and to which voltages with sequentially changed phases are applied, and an output section that is provided at the open end of the drive shaft and extracts the vibration of the drive shaft as rotational motion. are doing. In order to achieve the same object, the configuration of the present invention as set forth in claim 2 is such that the output section as set forth in claim 1 is connected to a drive side gear supported on the open end of the drive shaft;
The drive gear includes a driven gear that meshes with the driving gear. Furthermore, the configuration of the present invention according to claim 3 is,
According to a second aspect of the present invention, a displacement magnifying mechanism for magnifying the amount of displacement of the drive element is provided, and vibration is applied to the drive shaft via this displacement magnifying mechanism.

[0005]

The operation of the present invention having the structure set forth in claim 1 is to apply voltages whose phases are sequentially changed to a plurality of drive elements disposed near the fixed end of the drive shaft. By applying this voltage, the drive shaft is deflected by the drive element. The displacement due to this deflection is amplified toward the open end, where the output section is provided. That is, the amplitude of the drive element due to the applied voltage is amplified by the drive shaft and transmitted to the output section. In this way, reliable driving force can be obtained. The operation of the present invention having the configuration set forth in claim 2 is such that the output portion set forth in claim 1 is connected to a driving gear supported on the open end of the drive shaft, and a gear meshing with the driving gear. By including a drive side gear, more reliable driving force can be obtained. Furthermore, in the invention as set forth in claim 3, since the displacement magnifying mechanism is provided to magnify the amount of displacement of the drive element and give vibration to the drive shaft, it is possible to increase the amplitude of the drive side gear. Therefore, the pitch circle of the large-diameter gear on the driving side or the driven side can be increased, and the module of the gear for a given number of teeth can be increased, making it difficult for mutual slip between gears to occur, and gears can also be manufactured at low cost. become.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained below with reference to the drawings. FIG. 1 is a sectional view showing an assembled piezoelectric motor according to a first embodiment, and FIGS. 2 and 3 are exploded perspective views showing the piezoelectric motor shown in FIG. 1 in an exploded state. The piezoelectric motor 10 shown in FIGS. 1 to 3 includes first and second cylindrical cases 11 and 12 that are fitted into each other, an output section 25 housed in the second case 12, and an output section 25 housed in the second case 12. a substantially cylindrical drive shaft 16 secured to the open end of the section 25;
A plurality of piezoelectric elements 19 are provided near the left end of the drive shaft 16 in the drawing. In this embodiment, the drive shaft 16 is made of duralumin, and as shown in FIG. 1 case 11
can be mounted cantilevered on. A plurality of conical holes 16b having a substantially V-shaped cross section are formed near the mounting portion 16a. Here, a laminated piezoelectric element 1 to be described later is shown.
9 and a rolling element (ball) 21 interposed in a press-contact state.
is placed. Furthermore, a flange 16c is located near the right end in the figure.
is formed. This flange portion 16c is for positioning an internal gear (drive side gear) 23 that forms a part of the output portion 25, the details of which will be described later.

[0007] The first case 11 has the drive shaft 16
It is made of the same duralumin as , and is almost cylindrical with a bottom. An insertion hole 11a into which the mounting portion 16a of the drive shaft 16 is inserted is formed in the center of the left end surface 11e of the first case 11, and an insertion hole 11a into which the mounting portion 16a of the drive shaft 16 is inserted is formed in the outer peripheral surface of the right end. A joint portion 11b is formed. The fitting portion 11b also has a female threaded portion 11c on the outer circumferential surface facing the drive shaft 16 housed inside.
, 11c are bored. Also, this first case 1
In this embodiment, a drive shaft 16 is provided on the outer peripheral surface near the left end of the drive shaft 16.
Bolt insertion holes 11d are formed at 90 degree intervals with the center at . A laminated piezoelectric element 19 is placed here. Note that the mounting portion 16a of the drive shaft 16 and the insertion hole 11a of the first case 11 are connected to a set screw 20.
, 20.

The illustrated screw member 17 is screwed into each bolt insertion hole 11d. This screw member 17 has a threaded portion 17a formed on its outer circumferential surface, and a groove 17 for a screwdriver at its bottom.
It has a cylindrical shape. A laminated piezoelectric element 19 is housed inside this. This laminated piezoelectric element 1
Reference numeral 9 is constructed by laminating a plurality of piezoelectric elements in the longitudinal direction, and is designed to increase the amplitude when the applied voltage is turned on and off. Each of the laminated piezoelectric elements 19 is in pressure contact with the drive shaft 16 via the rolling elements 21 . Note that the reference numeral 18 indicates the screw member 17.
This is a lock nut to prevent loosening. The output unit 25 shown in this embodiment includes a drive side gear 23 fixed to the open end (right end in the figure) of the drive shaft 16, and the drive side gear 23.
The driven gear 13 is rotatably arranged and meshes with the driven gear 13.

The drive side gear 23 has a substantially cylindrical shape, and has a recess 23b formed on its right end face in the drawing.
These are internal teeth in which teeth 23a are formed on the inner circumferential surface of 3b. Moreover, a fitting hole 23c into which the drive shaft 16 is fitted is provided at the axis thereof.
is formed. The driven gear 13 has external teeth that mesh with the driving gear 23, and has a shaft 13a protruding from one side of the rotation center and having a threaded portion formed on its outer circumferential surface. It is rotatably supported by the second case 12 via this shaft 13a. The second case 12 is made of the same duralumin as the first case 11, and has an approximately cylindrical shape with a bottom as a whole. A recess 12a is formed in the center of the right end surface in the drawing, and lock nuts 14 and 15 for the driven gear 13 are screwed into the recess 12a.
It is rotated and driven. In this case, the rolling elements 22 and 24 are arranged to sandwich the wall surface in which the recess 12a is formed, and rotatably support the driven gear 13 itself through the clamping force of the lock nuts 14 and 15. ing. As shown in FIG. 2, holes 12b, 12b are formed on the outer circumferential surface of the left end in the figure at positions corresponding to the female threads 11c formed in the first case 11.

By the way, the diameter value (tooth tip circle diameter) of the driven side gear 13 is set smaller than the diameter value (tooth tip circle diameter) of the recess 23b of the drive side gear 23.
It is set so that the two do not come into contact with each other in a state where they are not displaced, that is, in a neutral state. That is, the number of teeth formed on both is 404 in this embodiment, the number of teeth on the drive side gear 23 is 404.
The number of sheets is 400 for the driven gear 13. By making the number of teeth slightly different in this way, a reduction ratio corresponding to the difference in the number of teeth is obtained. The reduction ratio in the case of this tooth number ratio is (4/400)=(1/100). still,
The number of teeth of the drive side gear and the driven side gear is not limited to the above-mentioned number of teeth, and may be appropriately set in consideration of the desired reduction ratio and the like. The general formula for the relationship between the ratio of the number of teeth and the output rotation speed N in this motor is N={(Z
1-Z2)/Z2}×60×f (rpm). However, N is the output rotation speed, Z1 is the number of teeth of the driving side gear (internal gear), Z2 is the number of teeth of the driven side gear (external gear), and f is the vibration (rotational vibration) frequency (Hz).

The operation of one embodiment of the apparatus having the above configuration will be explained with reference to FIG. 4 as well. Figures 4(A) to (
D) is an explanatory diagram showing the operating state of the drive side gear and the driven side gear. Note that the actual difference in the number of teeth between the two gears is as small as 4, and the difference in the diameters of the drive side gear 23 and the driven side gear 13 is small.
The diameter ratio is exaggerated. First, in this embodiment, voltages with different phases are sequentially applied to the four laminated piezoelectric elements 19. As a result, the open end of the drive shaft 16 is displaced in a clockwise circular motion as shown in FIGS. 4(A) to 4(D). In this case, since the laminated piezoelectric element 19 is disposed near the fixed end of the drive shaft 16, the amount of displacement of the drive shaft 16 by the laminated piezoelectric element 19 is from the fixed end to the free end. It will be amplified by In this way, when voltages with different phases are sequentially applied to the four laminated piezoelectric elements 19, the meshing portion between the driven gear 13 and the driving gear 23 changes from the state shown in FIG. 4(A) to the same state. The state changes sequentially to the state shown in Figure (D). In FIG. 4, the centers of the drive shaft 16 and output side shaft 13a are indicated by O1, and the center of the drive side gear 23 is indicated by O1.
It is shown as 2. When voltages with different phases are sequentially applied to the four laminated piezoelectric elements 19 to cause the open end of the drive shaft 16 to move in a circular motion, as shown in FIGS. 4A to 4D, for example, the drive side The center O2 of the gear 23 rotates clockwise about the center O1 of the shaft 13a or the like.

In the state shown in FIG. 2A, the drive shaft 16 (not shown in the diagram) is displaced to the right in the figure and is centered at O2.
is moving to the right, and in this state, the driven gear 1
The left portion of No. 3 in the drawing and the left portion of the drive side gear 23 are in mesh with each other. From this state, when voltages with different phases are sequentially applied to the four laminated piezoelectric elements 19, the open end of the drive shaft 16 moves in a circular trajectory to the state shown in FIG. 3(B). . Due to such displacement of the drive shaft 16, the drive side gear 23 attached to its open end rotates the engaged driven side gear 13 counterclockwise by a predetermined angle. Similarly, when the drive shaft 16 is sequentially displaced, the driven gear 13 meshing with the drive gear 23 is sequentially rotated counterclockwise by a predetermined angle.

Then, when the drive shaft 16 is displaced from the state shown in FIG. 3(D) to the state shown in FIG.
It rotates by the difference between the number of teeth of the drive side gear 23 and the number of teeth of the driven side gear 13. In this embodiment, the difference in the number of teeth is 4, so when the series of movements shown in FIGS. 4A to 4D is performed 100 times, the driven gear 13 rotates once. That is,
In this embodiment, the reduction ratio is set to (1/100) as described above. Then, when the application of voltage to the laminated piezoelectric element 19 is stopped, the bending displacement state of the drive shaft 16 is released, and thereby the drive side gear 23 and the driven side gear 13 become in a state of not meshing. Therefore, if it is necessary to stop the drive shaft 16 at a fixed rotational position, a voltage may be applied to any one of the laminated piezoelectric elements 19.

In the first embodiment described in detail above, the amplitude of the laminated piezoelectric element 19, which expands and contracts in accordance with the applied voltage, is amplified by the drive shaft 16. Therefore,
It is possible to perform reliable operation that could not be achieved with conventional piezoelectric motors of this type. Furthermore, the laminated piezoelectric element 19
By making the drive frequency match the primary resonance frequency of the drive shaft 16 or a frequency near it, the amount of displacement of the open end of the drive shaft 16 can be further increased, thereby ensuring more reliable operation. Can be done. Further, in this embodiment, since the output section is constituted by a gear, it is possible to output the rotational speed at a constant speed. Further, since the gear ratio can be arbitrarily set, a desired reduction ratio can be obtained. It should be noted that the present invention is not limited to the embodiments described above, and various modifications can be made within the scope of the invention. In the above embodiment, the output section provided at the open end of the drive shaft is connected to the internal teeth fixed to the drive shaft, and the driven gear rotatably supported by the second case so as to be able to mesh with the internal teeth. Although the output section is illustrated as having the following, an output section having the configuration shown in FIG. 5 may be used.

The output section 26 shown in FIG. 5 includes a driving member 27 having one end fixed and an external gear 26a formed at the other end, and an internal gear 28 meshing with the external gear 27a. It is equipped with the following. That is, in the illustrated embodiment, the configuration is the same as that in which the drive side gear and the driven side gear are replaced. Even with an output section having such a configuration, the same effects as those of the illustrated or described embodiments can be obtained. Incidentally, in each of the above embodiments, the drive member has a circular cross-sectional shape, but it may have a cross-sectional shape as shown in FIGS. 6 to 8. First, the drive member 29 shown in FIG. 6 has a rectangular cross-sectional shape. A laminated piezoelectric element 19 similar to that described above is fixed on each side surface near the fixed end portion 29a.

The drive member 30 shown in FIG. 7 has a triangular cross-section, and the drive member 31 shown in FIG. 8 similarly has a hexagonal cross-section. in this case,
A piezoelectric element indicated by reference numeral 32 is pressed into contact with each side surface. Even with a piezoelectric motor equipped with each drive member having such a shape, the same effects as in each of the embodiments described above can be obtained. Furthermore, in each of the above embodiments, the dimensions and number of teeth of the driving gear and the driven gear are set so that they do not mesh when no voltage is applied to the laminated piezoelectric element. The difference in the number of teeth between the side gear and the driven gear may be further reduced so that when the driving gear to which no voltage is applied is in a neutral state, the tips of the teeth of both gears are in mesh with each other. As a result, the driven member does not rotate and remains fixed when no voltage is applied. Moreover, the driving side gear and the driven side gear may not be circular but may be elliptical. Even with a piezoelectric motor having such configurations, it is possible to obtain the same effects as in each of the embodiments described above.

Furthermore, the present invention allows a structure such as the second embodiment shown in FIG. In this embodiment, the drive shaft 1
As a mechanism for displacing the piezoelectric element 6, a displacement magnifying mechanism 35 is provided to magnify the displacement of the laminated piezoelectric element 19 using a lever. For example, the laminated piezoelectric element 19 and the displacement magnification mechanism 3
5 are provided in four similar to the first embodiment, and by applying voltages with different phases to the respective laminated piezoelectric elements 19, the amount of rotational displacement ( The amplitude of the open end of the drive shaft 16 will be enlarged. As a result, for example, when the number of teeth of the drive side gear 23 and the number of teeth (reduction ratio) of the driven side gear 13 are set to certain values, the pitch circle of the gear can be made larger than in the first embodiment, and the gear module can be made larger. Therefore, the teeth can be made larger, there is no slippage between the teeth of both gears, and gears with larger modules are easier to manufacture. Furthermore, Figure 9
In this embodiment, as shown in FIG. 5, it is also possible to use an external gear on the driving side and an internal gear on the driven side.

Furthermore, in both the first and second embodiments, that is, in FIGS. 1, 5, and 9, the gears 23 and 27a provided at the end of the drive shaft are connected to the drive shaft 16 and the drive member 27. The other gear 23 is rotatably provided by a bearing.
, 28, it is also possible to rotate the gear on the drive shaft side. Further, in each of the above embodiments, a piezoelectric material element is used as the drive element, but it is also possible to use a giant magnetostrictive material element, a shape memory alloy element, or the like.

[0019]

According to the present invention described in detail above, it is possible to provide a piezoelectric motor that can obtain reliable driving force. Further, in the invention as set forth in claim 2, the rotational output can be extracted at a predetermined reduction ratio using gears. According to the third aspect of the invention, the module of the gear can be increased at a certain reduction ratio setting, tooth slip can be eliminated, and an inexpensive gear can be used.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an assembled state of a piezoelectric motor as a first embodiment.

FIG. 2 is an exploded perspective view showing the piezoelectric motor shown in FIG. 1 in an exploded state.

FIG. 3 is an exploded perspective view showing the piezoelectric motor shown in FIG. 1 in an exploded state.

FIGS. 4A to 4D are explanatory diagrams showing the meshing state of a driving gear and a driven gear.

FIG. 5 is a configuration explanatory diagram showing another embodiment of the output section.

FIG. 6 is a schematic perspective view showing another embodiment of the driving member.

FIG. 7 is a schematic perspective view showing another embodiment of the driving member.

FIG. 8 is a schematic perspective view showing another embodiment of the driving member.

[Figure 9] Schematic diagram of the structure of the piezoelectric motor of the second embodiment

[Figure 1
0] A perspective view showing the configuration of a conventional piezoelectric motor.

[Explanation of symbols]

16, 29 to 31 Drive shaft 19, 32 Piezoelectric element 25 Output section 23 Drive side gear 13 Driven side gear 35 Displacement magnification mechanism

Claims (3)

[Claims] 1. A drive shaft supported in a cantilevered manner, and a plurality of drives arranged near the fixed end of this drive shaft and centered around this drive shaft, to which voltages with sequentially changing phases are applied. What is claimed is: 1. A piezoelectric motor comprising: a piezoelectric element; and an output section that is provided at an open end of a drive shaft and extracts vibrations of the drive shaft as rotational motion. 2. The piezoelectric motor according to claim 1, wherein the output section includes a driving gear supported on the open end of the drive shaft, and a driven gear meshing with the driving gear. 3. The piezoelectric motor according to claim 2, further comprising a displacement amplifying mechanism for enlarging the amount of displacement of the drive element, and vibration is applied to the drive shaft via the displacement amplifying mechanism.