Vibration motors

Details Vibration motors Vibration motors

2001-03-09

2003-09-30

Ramirez, Nestor (Department: 2834)

Electrical generator or motor structure

Non-dynamoelectric

Piezoelectric elements and devices

C310S323040, C310S320000, C310S328000

Reexamination Certificate

active

06628044

ABSTRACT:

GENERAL FIELD OF THE INVENTION
The present invention relates to vibration motors.
Vibration motors are also known as “ultrasound” motors which refers to their preferred operating frequency, or as “piezoactive” motors which refers to their preferred excitation material.
The invention is particularly advantageous in application to rotary vibration motors, however it can also be applied to linear actuators, the term “vibration motor” in the present specification covering both rotary motors and linear actuators.
SUMMARY OF ONE POSSIBLE STRUCTURE FOR A VIBRATION MOTOR
A rotary vibration motor conventionally comprises at least one stator and one rotor, together with execution means for deforming said stator and/or said rotor in vibration modes that combine tangential vibrations and normal vibrations suitable for driving the rotor in continuous rotation.
Particularly advantageous vibration motor structures are proposed in particular in patent applications EP 0 907 213 and FR 98/10391 to which reference can advantageously be made. The general principle of those structures is shown diagrammatically in
FIGS. 1 and 2
.
Such a motor comprises an outer casing
2
containing two rotor disks
1
secured to a shaft
3
together with stator plates
4
between which said disks
1
are disposed.
Each stator plate
4
is constituted by a plurality of contact sectors
6
(referred to as stator “petals”) which are angularly distributed and which are separated in pairs by active elements
7
for imparting tangential deformation (piezoelectric or other elements). The contact sectors
6
of the two inner plates
4
are in register with one another. Active elements
8
(piezoelectric or other elements) for generating a normal force are interposed between the sectors
6
and these two inner plates
4
. Spring-forming means
9
are interposed between the casing
2
and the contact sectors
6
of the outer plates
4
.
When an active element
8
lengthens, the contact sectors
6
in register therewith clamp the rotor disks
1
. When it retracts, the corresponding contact sectors
6
release the disks
1
.
Two active elements
7
on either side of the same sector
6
are excited in phase opposition. Similarly, two adjacent active elements
8
are likewise excited in phase opposition. The active elements
8
for generating a normal force and the active elements
7
for tangential deformation are controlled synchronously so as to drive the rotors
1
in rotation.
STATE OF THE ART AND OBJECTS OF THE INVENTION
One of the problems encountered with vibration motors is that of their efficiency.
Proposals have already been made to use a material having resilient properties in a reciprocating contact zone between a rotor and a stator so as to minimize energy dissipation associated with cyclic friction between the rotor and the stator.
In particular, French patent application FR 2 742 011 proposes using shape memory alloys which are materials having non-linear super-elasticity and which, compared with conventional materials, have the advantage of accommodating large amounts of deformation in small quantities of material.
The term “super-elasticity” is used throughout the present specification to designate the property whereby a material can accept reversible elongation of 1% or more. It is also recalled that the non-linear character of super-elasticity gives rise to the presence of a change-of-phase plateau in the curve of deformation as a function of traction force.
In above-mentioned patent application FR 2 742 011, it is shown that such a structure has the advantage of limiting the peaks of the applied normal force and of maintaining the tangential friction force at values below the slip threshold.
An object of the invention is to further increase the efficiency of vibration motors.
Application BP 0 543 114 discloses an actuator in which bearing contact between the fixed portion and the moving portion is minimized so as to ensure that energy losses due to friction are minimized. In the solution proposed in that document, the contact surface of the fixed part as constituted by the stator is not rigid, but is deformed by the propagation of a traveling wave which drives the moving part which constitutes the rotor. Only the peak of the continuous deformation then comes into contact with the driven part.
It will be understood that that solution does not make it possible to obtain high drive powers of a kind that would be obtainable from vibration motor structures as described above with reference to
FIGS. 1 and 2
and operating on the principle of netting rigid sectors into vibration which sectors are moved bodily and not by continuous deformation.
BRIEF SUMMARY OF THE INVENTION
The invention proposes a solution for increasing the efficiency of a vibration motor of the type comprising comprising at least one stationary part and one part driven to move relative to said fixed part, together with excitation means suitable for exerting forces that tend to move rigid contact sectors presented by said fixed part and/or said moving part and to cause said rigid sectors to vibrate in vibration modes that combine tangential vibration and normal vibration, thereby driving the movement of the moving part.
For the tangential vibrations or the normal vibrations, said motor presents a main resonant mode and at least one secondary resonant mode, and the proposed solution consists in that the secondary resonant mode is at a frequency which is substantially equal to a harmonic frequency of the main resonant mode.
In particular, the moving part can be a rigid disk rotor, said motor having a stator which comprises at least one pair of stator plates, each plate having rigid petals suitable for receiving means for displacing said rigid petals tangentially and normally.
In a variant, the motor can be a linear actuator.
In a first advantageous variant, at least one element having elastic deformation properties is included is in the moving part and/or the stationary part, said element being separated from the contact face of said moving part and/or of said fixed part by a shoe-forming portion, and
the part (s) In which the elastic deformation elements are included is/are dimensioned in such a manner that the frequency of the secondary tangential resonant mode which is the resonant mode in which the shoe-forming portion and the remainder of the part oscillate in phase opposition, is substantially equal to a frequency which is a harmonic frequency of the main tangential resonant mode, in which the shoe-forming portion and the remainder of the part oscillate in phase.
Such a motor advantageously further includes the various following characteristics:
the frequency of the secondary tangential resonant mode is substantially equal to twice the frequency of the main tangential resonant mode;
it includes an array of elastic elements interposed between the shoe-forming portion and the remainder of the stationary part and/or the moving part; and
the elastic element is made of a material presenting properties of super-elasticity.
In another, likewise advantageous variant, which can be implemented in addition to the first variant or independently thereof, the motor presents a secondary normal resonant frequency which is substantially a harmonic frequency of the main normal resonant frequency, and the excitation means comprise means for generating normal vibrations at both of these two resonant frequencies.
Such a motor advantageously further includes the various following characteristics taken singly or in any feasible combination:
it comprises a casing containing at least two is pairs of stator plates having tangential deformation active elements, and two rotor disks which extend between the plates of respective ones of said two pairs, the normal deformation active elements extending in particular between the plates of both of the two facing pairs, spring-forming means being interposed between the pairs of plates and the casing, and
it includes, between the stator plates and the spring-forming means, at least one assembly comprising a mass and an elas

Affiliated with

Also associated with

Rating

Vibration motors does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Vibration motors, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Vibration motors will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3018378