JPH0923665A - Stator of ultrasonic motor and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stator of an ultrasonic motor which can drive a rotor with high efficiency and which requires a less number of processes and shorter processing time. SOLUTION: A stator is integrally formed of sintered alloy. On an outer surface of a base 10 fixed in a housing, a supporting section 11 is formed. And, a ring shaped vibrating section 12 is formed on an outer surface of the supporting section 11. On a lower face of the vibrating section 12, a piezoelectric element is pasted. The supporting section 11 is formed sufficiently thin since it was pressurized after sintering. In the supporting section, a plurality of through holes 13 which pass through in the axis direction are formed at equal angle intervals.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a stator for an ultrasonic motor and a method for manufacturing the same.

[0002]

2. Description of the Related Art FIG. 11 shows an ultrasonic motor stator 50.
Is shown. In this stator 50, a base 51, a support portion 52, and a vibrating portion 53 are integrally formed. That is, a thinly formed support portion 52 is formed on the outer peripheral side of a base 51 mounted on a mounting portion provided in a housing of an ultrasonic motor (not shown), and a circular shape is formed on the outer peripheral side of the support portion 52. An annular vibrating portion 53 is formed. A piezoelectric element (not shown) to which a high frequency voltage is applied is attached to the lower surface of the vibrating portion 53. Further, on the upper side of the vibrating portion 53, a large number of protrusions 55 isolated by the radial slits 54 are formed. A rotor (not shown) is brought into pressure contact with the upper surface of each protrusion 55. Then, when a high frequency voltage is applied to the piezoelectric element, high frequency elastic vibration is excited in the vibrating portion 53. By this high frequency elastic vibration,
The rotor that comes into pressure contact with the upper surface of the protrusion 55 is rotationally driven.

In an ultrasonic motor using such a stator 50, the supporting portion 52 is formed as thin as possible so that the vibrating portion 53 is easily bent. As a result, high-frequency vibration is excited in the vibrating portion 53 with high efficiency. Further, the loss due to the transmission of the high frequency vibration excited in the vibrating portion 53 to the base 51 side is prevented.

Further, by forming the slit 54 as narrow as possible and making the upper surface area of each projection 55 (that is, the contact area with the rotor) as large as possible, the high frequency vibration excited in the vibrating portion 53 is efficiently transmitted to the rotor. I try to communicate well.

Further, by increasing the flatness of the upper surface of each protrusion 55 to improve the contact state between each protrusion 55 and the rotor, the high frequency vibration of the vibrating portion 53 is efficiently transmitted.

By the way, as a method of integrally forming the stator 50 as described above, there are press forming of metal plate, forging, powder metallurgy (that is, formed of sintered alloy) and the like.
Of these, when the stator 50 is formed by press molding, it is difficult to form the slit 54 by press molding. Therefore, the slit 54 must be formed by cutting the stator 50 after molding by a milling machine or the like. I have to. Therefore, since it is necessary to repeatedly perform cutting to form a large number of slits 54, there is a problem that a long processing time is required and a manufacturing cost is increased. Further, since the flatness of the upper surface of each projection 55 after press molding is poor, a step of polishing the projection 55 flat after molding is necessary.
Since this polishing step also requires a long processing time, the manufacturing cost is further increased. Further, since the support portion 52 also needs a precise thinning process, similarly, the cutting process after the press molding is required. Therefore, the manufacturing cost is increased by the processing time.

On the other hand, when the stator 50 is molded from a sintered alloy, the slits 54 can be formed by the pressure molding and sintering processes, so that slit cutting after sintering becomes unnecessary. Regarding the flatness of the upper surface of the protrusion 55, a relatively high flatness can be obtained by pressing the protrusion 55 after sintering. Therefore, the stator 5 is made of sintered alloy.
When 0 is formed, it can be manufactured at a relatively lower cost than in the case of press molding.

[0008]

However, when forming the stator 50 with a sintered alloy, it is difficult to form the support portion 52 sufficiently thin. Because the support 52
Needs to be formed to have a thickness of, for example, about 0.5 mm. However, in the pressure molding step of the raw material powder, it is difficult for the powder to spread to the supporting portion 52 of the molding die, so that such a thin support is required. It is difficult to form the portion 52.

Therefore, when the stator 50 is formed of the sintered alloy, the support portion 52 is formed thicker than the intended thickness in the forming and sintering steps. Then, after the sintering, the support portion 52 is cut and formed into a predetermined thickness. Therefore, at present, even when the stator 50 is integrally formed of a sintered alloy, the number of processing steps and the processing time for cutting the support portion 52 are required, so that sufficient manufacturing cost reduction cannot be achieved. .

The present invention has been made to solve the above problems, and an object thereof is to be able to drive a rotor with high efficiency and to reduce the number of processing steps and processing time. An object is to provide a stator of an ultrasonic motor and a manufacturing method thereof.

[0011]

In order to solve the above-mentioned problems, the invention according to claim 1 is a base fixed to a housing of an ultrasonic motor, and a high frequency vibration by a piezoelectric element formed in an annular shape. In a stator of an ultrasonic motor integrally formed of a sintered alloy, the support portion is formed after the sintered alloy is sintered. Was pressed into a predetermined thickness.

Therefore, according to the first aspect of the present invention,
For the base fixed to the housing of the ultrasonic motor,
The supporting portion that supports the vibrating portion in which high-frequency vibration is excited can be thinly formed by pressure molding. As a result, it is possible to reduce the thickness of the support portion without performing cutting work. or,
Since the support portion is thinned, the vibrating portion easily bends.
As a result, high-frequency vibration is excited in the vibrating section with high efficiency, and the transmitted high-frequency vibration to the base side is suppressed.

In the invention according to claim 2, in the invention according to claim 1, a plurality of through holes penetrating in the axial direction are formed in the support portion. Therefore, according to the second aspect of the invention, in addition to the effect of the first aspect of the invention, the support portion escapes into the through-hole in which a plurality of excess wall portions of the support portion are formed during pressurization. Is thinly formed without its density becoming too high. As a result, the support portion can be easily thinned. Further, since the supporting portion is thinned without increasing the density, high-frequency vibration is excited in the vibrating portion with higher efficiency, and transmission of the excited high-frequency vibration to the base side is further suppressed.

According to a third aspect of the present invention, there is provided a base fixed to the housing of the ultrasonic motor, a vibrating portion formed in an annular shape, in which high frequency vibration is excited by a piezoelectric element, and a vibrating portion. In a method for manufacturing a stator of an ultrasonic motor in which a stator composed of a supporting portion that supports a table is integrally formed from a sintered alloy, a predetermined thickness is obtained by pressing the supporting portion after sintering the sintered alloy. So that it is molded.

Therefore, according to the invention of claim 3,
The stator is composed of a base fixed to the housing of the ultrasonic motor, a vibrating part formed in an annular shape in which high-frequency vibration is excited by a piezoelectric element, and a supporting part supporting the vibrating part with respect to the base. After tying, the supporting portion was pressed to form the thickness thereof to a preset thickness. As a result, the thickness of the supporting portion can be formed to a thickness that cannot be formed in the steps of forming and sintering the sintered alloy.

Further, in the invention described in claim 4, in the invention described in claim 3, a plurality of through holes penetrating in the axial direction are formed in the support portion after sintering, and the through holes are formed. The supporting portion was pressed.

Therefore, according to the invention described in claim 4,
In addition to the effect of the invention described in claim 3, when the sintered support part having a plurality of through holes penetrating in the axial direction is pressed, a surplus of the support part has a flesh in each through hole. escape. As a result, the pressed support is thinned without excessively increasing its density.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. FIG. 4 shows a cross section of the ultrasonic motor 1. The housing 2 is composed of a base 3 and a case 4, and a mounting portion 5 is formed inside the base 3 so as to project therefrom. A base end portion of a rotary shaft 6 is rotatably supported by a bearing 7 in the center of the base 3, and the base end portion is penetrated through the mounting portion 5 and introduced into the case 4. A support cylinder 5 a through which the rotating shaft 6 is inserted is formed on the upper surface of the mounting portion 5.

A stator 8 is mounted on the mounting portion 5,
A support cylinder 5 is provided in a shaft hole 9 formed in the center of the stator 8.
a is inserted. Then, the stator 8 is supported by the support cylinder 5a.
As a result, it is caulked and fixed on the mounting portion 5.

As shown in FIGS. 1 to 3, the stator 8 is integrally formed of a sintered alloy and has an annular base 10 that is mounted on the mounting portion 5 with the shaft hole 9 as the center, and the base 10. It is composed of a support portion 11 formed on the outer peripheral side and a vibrating portion 12 formed on the outer peripheral side of the support portion 11. The support 11 is the base 1
It is formed thinner than 0 and the vibration part 12. In the present embodiment, the outer diameter of the vibrating portion 12 is 60 mm and the supporting portion 11 is
Has a thickness of 0.5 mm. A plurality of substantially fan-shaped through holes 13 are formed in the support portion 11 over the entire circumference at equal angular intervals. A plurality of slits 14 are formed in the upper part of the vibrating portion 12 at equal angular intervals radially around the shaft hole 9, and a protrusion 15 is formed between each adjacent slits 14. The piezoelectric element 16 is bonded to the lower surface of the vibrating portion 12.

On the upper surface of the stator 8, an annular rotor 1 is provided.
7 is placed. An annular lining material 18 is attached to the lower surface of the outer peripheral portion of the rotor 17, and the outer peripheral portion of the rotor 17 is provided with the protrusions 1 of the vibrating portion 12 via the lining material 18.
It is in contact with the upper surface of 5. A shaft hole 19 is formed in the center of the rotor 17, and the rotary shaft 6 is inserted through the shaft hole 19 and protrudes above the rotor 17.

An elastic pressing member 20 is arranged on the upper surface of the rotor 17, and the elastic pressing member 20 is fixed by a nut 21 screwed to a male screw portion 6a provided at the tip of the rotary shaft 6. The lower surface of the elastic pressing member 20 contacts the upper surface of the rotor 17 to press the rotor 17 downward, and the lower surface of the outer peripheral portion of the rotor 17 is pressed to the upper surface of each protrusion 15 of the vibrating portion 12. . Therefore, the rotor 17 and the rotating shaft 6 are engaged with each other in the rotating direction, and the rotating shaft 6 rotates together with the rotor 17.

When a high frequency voltage is applied to the piezoelectric element 16, high frequency elastic vibration is excited in the vibrating portion 12. as a result,
The rotor 17 is rotationally driven and the rotary shaft 6 is rotated.

Next, a method of manufacturing the stator 8 will be described. First, the molding process will be described. FIG. 5 is a schematic cross-sectional view showing how the stator prototype 32 is molded from the raw material powder with the molding dies 30 and 31. The lower molding die 30 in the frame portion 33 is formed in a shape corresponding to the upper side of the stator 8, and the upper molding die 31 is also formed in a shape corresponding to the lower side of the stator 8. In addition, each molding die 3
No parts for forming the through holes 13 of the support part 11 are provided in the parts 0 and 31. And both these molds 3
At 0 and 31, the raw material powder is pressure-molded to form the stator prototype 32 in which the through holes 13 are not formed. The stator prototype 32 is sintered in the subsequent sintering process. Next, the hole forming process, which is a process subsequent to the sintering process, will be described.

FIG. 6 shows a mold 34, 35 including a stator prototype 32.
It is a schematic cross section which shows a mode that the through hole 13 is formed.
In the lower die 34 in the frame portion 36, a plurality of concave portions 36 are formed at equal angular intervals at positions corresponding to the support portion 11. Each recess 36 is formed in a substantially fan shape like the through hole 13. Further, penetrating portions 37 having a substantially fan-shaped cross section are arranged at positions corresponding to the respective recesses 36 of the upper mold 35. When the upper die 35 is fitted to the lower die 34, each through portion 37 is fitted into the corresponding recess 36. Then, the stator prototype 32 sintered to the lower mold 34
Is placed and pressed by the upper die 35, a plurality of through holes 13 are formed at predetermined positions of the supporting portion 11 by the through portions 37 and the corresponding recesses 36.

Next, the pressurizing step will be described. FIG. 7 is a schematic cross-sectional view showing a state in which the supporting portions 11 of the stator prototype 32 are pressed by the molds 38 and 39. The lower mold 38 in the frame portion 40 is formed in a shape corresponding to the upper side of the stator prototype 32, and the upper mold 39 is formed in a shape corresponding to the lower side of the stator prototype 32. A support pressing unit 41 is provided at a position corresponding to the support 11 of the upper mold 39. When the upper die 39 is fitted to the lower die 38, the gap between the supporting portion pressing portion 41 and the portion of the lower die 38 corresponding to the supporting portion 11 becomes equal to the finished thickness of the supporting portion 11. Has become. Then, the stator mold 32 is attached to the lower mold 38.
Is placed and pressure is applied by the upper mold 39, the support part pressure part 41
The support part 11 is pressurized by.

FIG. 8 shows a cross section of the support portion 11 at a position including the through hole 13, and the broken line shows the shapes of the support portion 11 and the through hole 13 before pressurization. When the support portion 13 is pressed, the support portion 11 is thinly plastically deformed as shown by a solid line in FIG.
It flows in. As a result, the support portion 11 is formed to have a predetermined thickness. At this time, since the excess meat part of the support part 11 before pressurization moves into each through hole 13, the density of the support part 11 thinned by pressurization is slightly increased. Then, although the support portion 11 is thinly formed, the support portion 11 has a required strength by slightly increasing the density. Each through hole 1
3 has a smaller shape than before pressing.

The stator 8 is formed by the above steps. Next, the stator 8 of the ultrasonic motor configured as described above
The operation of will be described.

When a high frequency voltage is applied to the piezoelectric element 16, high frequency vibration is excited in the vibrating portion 12. At this time,
Since the vibrating portion 12 is easily bent by reducing the thickness of the support portion 11, high-frequency vibration is excited in the vibrating portion 12 with high efficiency. Further, since the plurality of through holes 13 of the supporting portion 11 are provided, the vibrating portion 12 is more easily bent,
High-frequency vibration is excited in the vibrating section 12 with higher efficiency.

Further, since the support portion 11 is sufficiently thin, the transmission of the high frequency vibration excited by the vibration portion 12 to the base 10 side is suppressed. As a result, the high frequency vibration of the vibrating section 12 is less likely to be attenuated, so that the rotor 17 is driven with high efficiency. Further, since the support portion 11 is provided with the plurality of through holes 13, the high frequency vibration of the vibrating portion 12 is further difficult to be transmitted to the base 10. As a result, the high frequency vibration of the vibrating section 12 is less likely to be damped, and the rotor 17 is driven with higher efficiency.

As described in detail above, according to the stator of the ultrasonic motor of the present embodiment, the supporting portion 11 is made of raw material powder.
A stator prototype 32 having a plurality of through holes 13 formed therein is integrally molded, and after the stator prototype 32 is sintered, the support portion 11 is formed.
Was pressed to form a thin film having a predetermined thickness. As a result, it is possible to reduce the thickness of the supporting portion 11 without performing cutting work or the like after sintering, so that it is possible to reduce the number of processing steps and the processing time. In addition, when pressurizing, the excess meat portion of the support portion 11 is allowed to escape into each through hole 13. As a result, it is possible to facilitate the thinning of the supporting portion 11 and to suppress the increase in the density of the supporting portion 11 due to the pressurization to a slight size.

Further, in the present embodiment, the density of the support portion 11 is slightly increased by pressurization, so that the strength is secured and the vibration absorption function is provided even if the thickness is thin. As a result, the vibrating portion 12 is easily bent, so that high-frequency vibration can be excited in the vibrating portion 12 with high efficiency. Therefore, the rotor 17 can be driven with high efficiency. Further, it is possible to suppress the transmission of the high frequency vibration excited in the vibrating section 12 to the base 10 side. As a result, damping of high-frequency vibrations in the vibrating section 12 can be suppressed, so that the rotor 17 can be driven with high efficiency.

Further, since the plurality of through holes 13 are formed in the supporting portion 11, the vibrating portion 12 can be more easily bent and the high frequency vibration can be excited in the vibrating portion 12 with higher efficiency. Therefore, the rotor 17 can be driven with higher efficiency. Further, the plurality of through holes 13 of the support portion 11 can further suppress the transmission of the high frequency vibration excited in the vibration portion 12 to the base 10 side. As a result, damping of high-frequency vibrations in the vibrating section 12 can be suppressed, so that the rotor 17 can be driven with higher efficiency.

Further, according to the method of manufacturing the stator 8 of the ultrasonic motor of the present embodiment, the supporting portion 11 is molded and sintered to have a thickness larger than a predetermined thickness, and the plurality of through holes 13 are formed. After being formed and sintered, the supporting portion 11 is pressed to be formed into a predetermined thickness. As a result, in the stator 8 formed of a sintered alloy, the thin support portion 11 can be formed without cutting.

Further, a plurality of through holes 13 are provided in the support portion 11 before pressurization, and when pressurizing the support portion 11, an extra meat portion of the support portion 11 escapes into the through hole 13. As a result, the support portion 11 can be thinly formed without excessively increasing the density.

The present invention is not limited to the above embodiment, but may be configured as follows. (1) In the above-described embodiment, the through hole 13 provided in the support 11 is opened in the support 11 even after the pressing process. As shown in FIG. 9, the through hole 13 may be completely removed after the pressing step.

Alternatively, the through hole 13 may not be provided in the support portion 11, and the support portion 11 of the stator prototype 32 after sintering may be formed to have a predetermined thickness only by pressing. However, in this case, since the density of the supporting portion 11 tends to be high, there is a limit to thinning.

(2) The shape of each through hole 13 is not limited to a substantially fan shape, but may be an elliptical through hole 13 as shown in FIG. 10, for example. In addition, other shapes such as a quadrangle, a triangle, and an ellipse may be formed.

(3) In the above embodiment, the stator prototype 32 in which the through holes 13 are not formed in the support portion 11 is formed in the molding and sintering process, and the through holes 13 are formed in the hole forming process. . The through hole 13 may be formed in the molding step, and the hole forming step may not be performed.

(4) In the pressurizing step, the vibrating section 12 may be simultaneously pressed to have a higher density than the support section 11. In this case, the attenuation of the high frequency vibration excited in the vibrating section 12 can be suppressed, so that the rotor 17 can be driven with high efficiency.

The technical ideas other than the claims that can be understood from the above-described embodiment will be described below along with their effects. (1) In the stator of the ultrasonic motor according to claim 1, the density of the vibrating portion 12 is set higher than that of the supporting portion 11. With such a configuration, high-frequency vibration is excited in the vibrating section 12 with high efficiency, and the excited high-frequency vibration is less likely to be attenuated, so that the rotor 17 can be driven with high efficiency.

[0042]

As described above in detail, according to the first aspect of the invention, the rotor can be driven with high efficiency, and the number of processing steps and the processing time can be reduced.

According to the invention described in claim 2, in addition to the effect of the invention described in claim 1, it is possible to reduce the thickness of the supporting portion without making the density of the supporting portion excessively high. Therefore,
The rotor can be driven with higher efficiency.

According to the third aspect of the invention, since the thin supporting portion can be formed without cutting, it is possible to reduce the number of processing steps and the processing time.
According to the invention described in claim 4, in addition to the effect of the invention described in claim 3, it is possible to reduce the thickness of the supporting portion without excessively increasing the density.

[Brief description of drawings]

FIG. 1 is a perspective view showing a stator.

FIG. 2 is a front view of the same.

FIG. 3 is a sectional view of the same.

FIG. 4 is a sectional view of an ultrasonic motor.

FIG. 5 is a schematic view showing a molding process.

FIG. 6 is a schematic diagram showing a through hole forming step.

FIG. 7 is a schematic diagram showing a pressurizing step.

FIG. 8 is a schematic cross-sectional view showing a state of a through hole of a support portion.

FIG. 9 is a schematic cross-sectional view showing a state of a support portion.

FIG. 10 is a front view showing a stator of another example.

FIG. 11 is a perspective view showing a conventional stator.

[Explanation of symbols]

1 ... Ultrasonic motor, 2 ... Housing, 10 ... Base, 11
... Supporting part, 12 ... Vibrating part, 13 ... Through hole.

Claims (4)

[Claims] 1. A base which is fixed to a housing of an ultrasonic motor, a vibrating section which is formed in an annular shape and in which high frequency vibration is excited by a piezoelectric element, and a support section which supports the vibrating section with respect to the base. A stator of an ultrasonic motor integrally formed of a sintered alloy, wherein the stator is pressed to a predetermined thickness after sintering the sintered alloy to form a predetermined thickness. 2. The stator of an ultrasonic motor according to claim 1, wherein the support portion has a plurality of through holes penetrating in the axial direction. 3. A base that is fixed to the housing of the ultrasonic motor, a vibrating portion that is formed in an annular shape and in which high-frequency vibration is excited by a piezoelectric element, and a support portion that supports the vibrating portion with respect to the base. In a method of manufacturing an ultrasonic motor stator in which a stator made of is integrally molded from a sintered alloy, a stator of an ultrasonic motor in which a supporting portion is pressed to have a predetermined thickness after sintering of the sintered alloy. Manufacturing method. 4. The stator of the ultrasonic motor according to claim 3, wherein after the sintering, a plurality of through holes penetrating in the axial direction are formed in the support portion, and the support portion having the through holes is pressed. Production method.