JPH03230774A - Vibration wave motor - Google Patents

Abstract

PURPOSE:To prevent generation of a stick slip and to prevent generation of a beat by reducing the magnitude of a maximum static distortion deformation in the friction driving direction of half number or more of protrusions of many protrusions formed on one side surface of an elastic unit. CONSTITUTION:Protrusions 2a of an annular elastic unit 2 to be bonded with a piezoelectric element 1 are provided at an equal pitch. Each protrusion 2a is formed in a trapezoidal section, and 63 protrusions 2a are disposed on a circumference. In generating states of a protrusion static distortion deformation amount and beat, no beat is generated if motor characteristics are equivalent but the static distortion deformation is smaller than 1.75X10<-4>mm/N, and the beat is generated if it is larger than 1.75X10<-4>mm/N. The above results are the same in the case in which the inner diameter of the unit is any of 54.1 and 68.0mm.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention produces progressive bending vibration in the elastic body by applying an alternating current voltage to an electro-mechanical energy conversion element joined to the elastic body. This invention relates to a convex vibration magnification mechanism provided on an elastic body of an ultrasonic motor that frictionally drives a moving body pressed against an elastic body by causing a mass point of the body to move in a circular or elliptical manner.

[Prior Art] First, the principle of a vibration wave motor using traveling waves of bending vibration will be explained with reference to FIG. 8 and FIG. 9, which is a bottom view thereof. As shown in the figure, a first group of electro-mechanical energy conversion elements 1a and a second group of electro-mechanical energy conversion elements 1b are arranged on the lower surface of a ring plate-shaped vibrating body 2 made of an elastic body (for example, metal). It is fixed. As these electro-mechanical energy conversion elements, piezoelectric elements, electrostrictive elements, magnetostrictive elements, etc. can be used, and below, piezoelectric elements will be used as a representative example.

First, regarding the first group of piezoelectric elements 1a, electrode films (not shown) are provided on the upper and lower surfaces of all the piezoelectric elements 1a, and these electrodes are connected to each other by an electrical connection means (not shown) to each other on the upper surface and to each other on the lower surface. are electrically connected in parallel,
A voltage is simultaneously applied to each piezoelectric element 1a, and each piezoelectric element is configured to expand and contract in the circumferential direction by applying this voltage. Each piezoelectric element 1a is arranged such that adjacent ones have opposite polarities (i.e.,
(so that when one expands, the other contracts) and are arranged in the circumferential direction with a pitch of λ/2.

The same applies to the configuration and arrangement of the second group piezoelectric elements 1b.

The first group 1a and the second group 1b are arranged to be shifted by an odd number of times λ/4. Further, it is assumed that the length of the entire circumference of the vibrating body 2 is an integral multiple of λ. Note that a portion 1° between the first group 1a and the second group lb is a region where no voltage is applied and no expansion or contraction action is actively performed.

In such a configuration and arrangement, when an AC voltage is applied only to the first group of piezoelectric elements 1a, the vibrating body 2 will convex downward in the part of the piezoelectric element 1a that extends, and convex upward in the part of the piezoelectric element 1a that contracts. As a result of the bending deformation, a standing wave of bending vibration (wavelength wave) is generated over the entire circumference of the vibrating body 2. In this case, the intermediate position between the piezoelectric elements 1a and the positions every λ/2 from there are nodes. Second group piezoelectric element 1
When an AC voltage is applied only to b, a standing wave of wavelength λ is similarly generated, but the position of the node is shifted by λ/4 compared to that of the standing wave.

If an AC voltage is applied to the first group piezoelectric element 1a and at the same time an AC voltage having an electrical phase difference of 90 degrees is applied to the second group piezoelectric element 1b, as a result of the synthesis of standing waves by both, A traveling wave of bending vibration that travels in the circumferential direction is generated in the vibrating body 2, and its traveling direction is determined by the sign of the phase difference between the applied voltages. In the traveling wave of this bending vibration, points on the neutral plane of the thickness of the vibrating body 2 (surface to which no bending stress is applied) only vibrate in the vertical direction, but points on the top and bottom surfaces of the vibrating body 2 vibrate in the vertical direction. performs a type of elliptical motion that is a combination of vertical vibration and circumferential vibration. Therefore, in FIG. 8, if the vibrating body 2 is appropriately supported so as not to rotate, and a ring plate-shaped movable body 3 (not shown) is brought into pressure contact with the upper surface of the vibrating body 2, the vibrating body 2 The piezoelectric element group 1 rotates by being driven by the frictional force caused by the elliptical motion of the
It can be selected depending on the positive or negative phase difference of the applied voltages a and lb.

The above is the principle of a vibration wave motor that uses traveling waves of bending vibration.

By the way, with such a vibration wave motor, in order to increase the moving speed of the moving body 3 and further increase the driving efficiency, as shown in FIG. A proposal has been made to form a large number of convex portions 2a by providing slits 2b (Japanese Patent Publication No. 1-40597).

FIG. 11 is a side view of such a vibrating body.

As shown in FIG. 12, without increasing the bending rigidity of the vibrating body 2, the convex portion 2a can increase the circumferential displacement and speed of the mass point (the tip of the convex portion 2a) of the vibrating body 2 that comes into contact with the moving body. The speed of the moving object can be increased.

[Problems to be Solved by the Invention] However, in the ultrasonic motor using progressive bending vibration as shown in the conventional example above, for example, the machining accuracy of the vibrating body and the moving body is not good, etc. When temporal and spatial unevenness occurs in the surface pressure of the contact surfaces of the body, unnecessary vibrations different from the vibrations used to drive the moving object are generated in the vibrating body. There was a problem in that noise was generated. Although the details of the mechanism by which such noise is generated are not clear, the following causes may be considered. In other words, if the frictional force acting between the movable body 3 and the tip of the convex portion 2a of the vibrating body that is in contact with it exceeds (*number of scratches)X (surface pressure), the movable body 3 and the convex portion 2a The tip of the slips,
(friction coefficient) x (surface pressure), if the moving body 3
The tip of the convex portion 2a sticks (fixes). It is known that unnecessary vibrations occur due to such repeated stick-slip cycles, such as in the case of vibrations in disc brakes of automobiles. The noise in ultrasonic motors is thought to be caused by the above-mentioned stick-slip phenomenon occurring more easily due to some mechanism when temporal and spatial unevenness occurs in the contact pressure between the vibrating body and the moving body. .

An object of the present invention is to solve these conventional problems, prevent stick-slip from occurring, and provide a vibration wave motor that does not generate squeal.

[Means and effects for solving the problem] The gist of the present invention to achieve the object is that an electric-mechanical energy conversion element is bonded to one side, and a large number of convex portions are formed on the other side. The electricity in the elastic body formed at approximately equal intervals
A vibration wave motor that forms progressive bending vibration waves in the elastic body by applying an alternating current voltage to a mechanical energy conversion element, and relatively moves a member that contacts a convex portion of the elastic body and the elastic body by frictional force. Among the many convex portions formed on the other surface of the elastic body, the maximum static deflection deformation in the friction drive direction of more than half of the convex portions is 1.
The vibration wave motor is characterized by being smaller than 75×10'ml11.

In other words, we focused on the fact that stick-slip is the cause of squeaking, and in particular focused on the fact that sticks are caused by elastic deformation due to the frictional force of the convex parts of an elastic body, and by increasing the rigidity of the convex parts, the elastic This makes deformation difficult, prevents stick-slip, and eliminates squealing. Even if the rigidity of all the convex parts is not increased, it is effective as long as more than half of the convex parts are made rigid.

[Embodiments] First Embodiment A partial perspective view of a first embodiment of the present invention is shown in FIG. 1, and a sectional view thereof is shown in FIG. 2. The unit shown in numbers is mm,
Further, the dimensions indicated by a, b, h, and Il are as shown in Table 1, respectively.

In the vibration wave motor of this embodiment, convex portions 2a are provided at equal pitches on an annular elastic body 2 to which a piezoelectric element 1 is joined, and the convex portions 2a have a trapezoidal cross section as shown in the figure. , a total of 63 pieces are arranged on the circumference. The material of the elastic body 2 is 5US42
0J2 (E-1950ON/mm2), but Nf-P plating containing SiC grains (~0.5 μff1) is applied to the tip of the convex portion 2a in contact with the moving body as an anti-wear coating.

Table 1 shows dimensions a, b, and h of 1.000 Im and 2.55 Im, respectively.
mm2.3011101, 1 is 1.89mm, 1
．． 95mm, 2.05mm.

Examples 1 to 4 with 2.40 ml and 1.50 mm, 1.75 mm, 185 mm for comparative reference
The static deflection deformation amount of the convex portion and the occurrence of squealing in Comparative Examples 1 to 3 are shown.

Surface material 5US420J2 Here, the amount of static deflection deformation of the convex portion means the tip of the convex portion 2a (
This is the calculated value of the amount of deflection of the tip of 28 when a load of 1N is applied to the friction contact portion). The calculations were as follows.

When the X-axis is taken as shown in Fig. 3, the width C of the convex portion 2a is X=
Since C=a in O and c=b in x==h, C-(b''.

h x)+ Second moment of area to ■ teeth IL3 1 ba-a =□( 12h x+a)42' -a (□・ xa -11) b (However, I 13 Therefore, the equation of the elastic line is y x = h and y = - =.

From x and equation 0, bh + -((b -a a)x +ah) (log ((ba-a) xa-h) + (ba-a)hx-ahxlog(bh) + -
(b-a) h2bh -a bh (log (bh) -1) -(b-a) h2ah
2(log(bh)) The amount of deflection at the tip of the convex part is +ah2 by substituting x=0 into the equation 0.
1og (bh)) ... ■ ■ The amount of deflection at the tip of the convex portion 2a when a load of 1N was applied was determined using the formula. (The 1st position is mm/N) The calculated value is G, or the absolute value is shown in the table.

The motor characteristics (T-N characteristics and efficiency) were the same in both cases, but as shown in Table 1, the static deflection deformation was 1.75x 1.
No squeal occurred in Examples 1 to 4, which were smaller than 0 cm/N, and squeal occurred in Comparative Examples 1 to 3, which were larger than 1.75 x 10 mm/N.

The above results show that the inner diameter of the elastic body is 54 mm, 1 mm, and 6 mm.
The same was true for both cases of 8.0 mm.

Second Embodiment In the second embodiment, the elastic body 2 is made of invar (E-1480ON/mm' ), and the dimensions of the convex portion are It = 2.90 mm, 2.
Table 1 shows the amount of static deflection deformation of the convex portion of Example 5゜6.7 with a diameter of 19 mm and 2.79 mm, and the occurrence of squealing.
It is shown in Table 2 as well. Note that N1-P plating containing SiC grains is applied to the tips of the convex portions as in Examples 1 to 4. For comparative reference, Comparative Examples 4 and 5 with 42 = 1.39 mm' and 1.89 mm are also described.

Table 2 Material: Invar E = 1480 ON/mm' As seen from Table 2, even when the material is Invar, Examples 5 to 7 of the present invention have a static deflection deformation of 1.75x 10-'mm/N or less. No damage occurs.

Third Embodiment A partial perspective view of a third embodiment of the present invention is shown in FIG. 4, and a sectional view thereof is shown in FIG. Dimensions shown in numbers are in mm
and Examples 8 to 130 shown in ah-11
The dimensions are shown in Table 3. Example 8~
The convex portions 2a in 13 have a rectangular cross section as shown in the figure, and a total of 63 convex portions 2a are arranged at equal intervals on the circumference.

The material of the elastic body 2 is 5IJS420J2 (E-1950
ON/■2) However, the tip of the convex portion 2a in contact with the moving body is coated with SiC grains (~Q) as a wear-resistant coating.
, 5 μm) N1-P plating is applied.

Table 3 Material: 5US420J2 Table 3 shows the dimensions of the convex portions, the amount of static deflection deformation of the convex portions, and the occurrence of stains in Examples 8 to 13 and Comparative Examples 6 to 11 for comparison reference. Here, considering the static deflection deformation amount of the convex portion in the same way as in Examples 1 to 4, the tip of the convex portion 2a (frictional contact This value is the amount of deflection of the tip of 2a when a load of 1N is applied to the part), calculated according to the following formula.

4PH’ y,,tsu=-...■ aj23 The calculated value is e, but it is shown as an absolute value in the table.

The motor characteristics (T-N characteristics/efficiency) were the same in both cases, but even if the convex cross-sectional shape was rectangular, the static deflection deformation was smaller than 1.75x 1G-'a+m/N in Example 8. ~13, no squeal occurred, 1.75 x 10
In Comparative Examples 6 to 11, which were larger than -'mm/N, squealing occurred.

Fourth example FIG. 7 shows a fourth embodiment.

In this embodiment, two types of convex portions 2a are provided on the elastic body 2.

and 2a are mixed, and the circumferential length of the first convex portion 2al is J211 width d and height, and the circumferential length of the second convex portion 2a2 is I12 + width d and height h, jZ,≠1
It is 2. Note that the height of the elastic body is N1, and the width is D.

In the elastic body configured in this way, the inner diameter is 54.1.
D=4. OO+nm, H=2.70+nm, and each dimension of the first convex portion 2a and the second convex portion 2a2 is I.
l-+-L, tlOmm, d=2.50mm, h=2.
30 (Static deflection deformation = 1.712x 10-'m
+n/N), It 2-1.40mm, (
Static deflection deformation = 3.638 x 10-'+n+n
/N), the circumferential length is 1.80mm
Example 1 in which the first convex portion 2a is more than half of the total number of convex portions.
Table 4 shows the occurrence of squealing in 4.15. The material of the elastic body is 5US420J2, and SiC grains (
For comparison, Comparative Example 12.13 in which N1-P plating with 1.80 mm of circumferential length is less than half of the total number of convex parts is also included. I wrote it down.

Static deflection deformation is 1.75X as in Example 14.15
If the number of first convex portions 2a smaller than 10-'LL+m is more than half of the total number of convex portions, no smearing occurs.Table 4 [Effects of the Invention] As explained above, according to the present invention, elastic Among the many convex portions that are vibration magnifying mechanisms provided on the moving body side, the static deflection deformation of more than half of the convex portions is 1.75X 10-
By providing the lid with a rigidity of less than 1 m/N, it is possible to prevent dripping without changing other characteristics.

[Brief explanation of drawings]

Fig. 1 is a partial perspective view of an elastic body showing a first embodiment of the vibration wave motor according to the present invention, Fig. 2 is a sectional view thereof, and Figs. 3 (a) and (b) are for calculating the amount of deflection. FIG. 4 is a partial perspective view of the second embodiment, FIG. 5 is a sectional view thereof, FIG. 6 is a schematic diagram for calculating the amount of deflection, and FIG. 7 is a portion of the third embodiment. 8 is a perspective view of a conventional vibration wave motor; FIG. 9 is a bottom view thereof; FIG. 10 is a perspective view of a conventional vibration wave motor; FIG. 11 is a partially enlarged side view; The figure is a diagram showing the driving state. 1...Piezoelectric element 2...Elastic body 2a...Protrusion and other 4 people ¥1 Figure 2 Figure 4

Claims (1)

[Claims] 1. AC to the electro-mechanical energy conversion element in an elastic body having an electro-mechanical energy conversion element bonded to one side and a large number of convex portions formed at approximately equal intervals on the other side. A vibration wave motor that forms a progressive bending vibration wave in the elastic body by applying a voltage and moves a member that contacts a convex portion of the elastic body and the elastic body relative to each other by frictional force, the vibration wave motor including the following: Among the many convex portions formed on the surface side, the maximum static deflection deformation in the friction driving direction of more than half of the convex portions is smaller than 1.75 x 10^4 mm per 1N. vibration wave motor.