Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
1998-12-23
2001-01-23
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
Reexamination Certificate
active
06177754
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an ultrasonic motor used for a clock, an automatic focusing system of a camera, an opening and closing operation of a shutter and a drive operation of an X-Y stage, and more particularly to an improvement of an ultrasonic motor and an electronic apparatus with an ultrasonic motor which reduces an abrasion in a pressure-contact portion between a pressing member and a pivot member.
In recent days, an attention has been given to an ultrasonic motor which generates an oscillating wave in an oscillator connected to a piezoelectric element and which can move a moving body by applying a frictional force due to the oscillator (for example, refer to Japanese Patent Examined Publication No. 62-92781).
Further, an ultrasonic motor of a rotating type is provided with an oscillator fixed to a central shaft, a piezoelectric element connected to a lower surface of the oscillator, a rotor brought into contact with a projection provided in the oscillator, a pivot fixed to a rotating center of the rotor, and a pressing spring for pressing the pivot (for example, refer to Japanese Patent Unexamined Publication No. 8-107686).
In accordance with this structure, the pressing spring urges the pivot so as to apply a pressing force to the rotor and the oscillator, generates a suitable frictional force to the rotor and the projection in the oscillator, and rotates the rotor in a predetermined direction.
However, since the pressing spring and the pivot are made of the same kind of material, both are hard cohered and abraded. Further, even when a lubricating oil is supplied between the pivot and the pressing spring, the lubricating oil is lost after the rotor rotates for a long time rotation, so that the pivot and the pressing spring are abraded.
As a result abrasion of the pivot or the pressing spring is associated with the problems of changing the pressing force and the frictional force, lowering a rotating speed of the rotor and a torque of the motor, and further stopping the motor.
Further, since the pivot is always pressure-contact at the same point with the pressing spring, there is a problem that a load of the pivot against the frictional force generated in the pressure-contact portion is great, so that the pivot is highly abraded.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an ultrasonic motor and an electronic apparatus with an ultrasonic motor which prevents an abrasion of a pivot member and a pressing member so as to prevent a rotating speed of a rotor from lowering and prevent a torque from lowering.
An ultrasonic motor according to the present invention comprises a piezoelectric element, an oscillator connected to the piezoelectric element, a rotor brought into contact with the oscillator, a pivot member provided in a rotating center of the rotor and a pressing member pressure-contacting to the pivot member
wherein the pressing member and the pivot member are made of different materials mutually different from each other.
In this case, the pressing member includes any of a plate spring and a structure in which a plate-like member is mounted to a distal end of a rubber or a spring.
It is preferable that the pivot member is made of a rigid material in view of transmitting a pressing force to the rotor, and it is preferable that the pressure-contact portion with the pressing member is formed in a spherical shape, a pin shape or a triangular conical shape in view of reducing a frictional force generated between the pressure-contact portion and the pressing member.
A material for the pressing member includes a stainless steel, a spring steel, a BeCu, a phosphor bronze.
A material for the pivot member includes a steel hardened by a heat treatment, a stainless steel, and ceramics such as an Al
2
O
3
, a SiC and Si
3
N
4
.
In accordance with this structure, the piezoelectric element is excited so as to generate an oscillating wave in the oscillator, whereby the oscillator is brought into contact with the rotor at every period. The pressing member is brought into pressure contact with the pivot member so as to press, the pressing force is transmitted to the rotor so as to generate a frictional force in the contact portion between the rotor and the oscillator, and the rotor is rotated due to the frictional force. When the rotor is rotated, a friction is generated in the pressure-contact portion between the pressing member and the pivot member. The friction is reduced by making the pressing member and the pivot member of materials mutually different from each other in comparison with the case that the same kind of material is used for both, and the pressing force to the rotor and the frictional force are maintained.
Accordingly, the friction of the pivot member and the pressing member can be reduced, and the reduction of the rotating speed and the torque of the rotor can be prevented.
In another embodiment an ultrasonic motor according to the present invention comprising a piezoelectric element, an oscillator connected to the piezoelectric element, a rotor brought into contact with the oscillator, a pivot member provided in a rotating center of the rotor and a pressing member pressure-contacting to the pivot member,
a hardness of the pivot member being greater than that of the pressing member.
In accordance with this structure, since the hardness of the pivot member is greater than that of the pressing member, abrasion of the pivot member is reduced with respect to the friction generated in the pressure-contact portion.
Still further, another ultrasonic motor according to the present invention comprises a piezoelectric element, an oscillator connected to the piezoelectric element, a rotor brought into contact with the vibrator, a pivot member provided in a rotating center of the rotor, pressing member pressure-contacting to the pivot member,
and a hard film provided in a pressure-contact portion of at least one of the pivot member and the pressing member.
In this case, it is preferable that the hard film is formed by any one of a DLC, a TiN, a TiCrN, a CrN, a TiCNi, a TiAlN, an Al
2
O
3
, a ZrO
2
, a SiC, a Cr, a NiP, a WC, a SiO
2
, a Ta
2
O
5
, a SiN, a SiaAlbOcNd (a sialon).
In accordance with this structure, the pivot member or the pressing member is protected from the friction by forming the hard film, and a durability is improved. Further, since a comparatively soft material can be selected for the pivot member and the pressing member, a selective range for the material is increased as well as a workability for the material is improved.
Furthermore, another ultrasonic motor according to the present invention comprises a piezoelectric element, an oscillator connected to the piezoelectric element, a rotor brought into contact with the oscillator, a pivot member provided in a rotating center of the rotor, and a pressing member pressure-contacting to the pivot member,
and a solid lubricant for reducing a friction is provided in at least one of the pressing member and the pivot member.
In this case, it is preferable that the solid lubricant be, a PTFE (a polytetrafluoroethylene), a graphite, a molibuden disulphide or a gold.
In accordance with this structure, the solid lubricant reduces the friction generated in the pressure-contact portion between the pressing member and the pivot member, reduces the friction in the pivot member or the pressing member, and requires no lubricating oil.
Moreover, another ultrasonic motor according to the present invention comprises a piezoelectric element, an oscillator connected to the piezoelectric element, a rotor brought into contact with the oscillator, a pivot member provided in a rotating center of the rotor, and a pressing member pressure-contacting to the pivot member,
and a recess portion for holding a lubricating oil provided in a pressure-contact portion between the pressing member and the pivot member.
In this case, the recess portion of the pressure-contact portion can have any cross sectional shape so lone as it can hold the lubricating oil, such as a circular
Iino Akihiro
Kasuga Masao
Suzuki Kenji
Suzuki Makoto
Yamanaka Takashi
Adams & Wilks
Medley Peter
Ramirez Nestor
Seiko Instruments Inc.
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