JPH03243180A - Oscillation wave motor - Google Patents

Abstract

PURPOSE:To permit the highly accurate detection of a rotating angle by a method wherein a stator, connected to piezo-electric elements having an interval corresponding to the predetermined wave length of an electrode pattern, and a pressure detector, accommodated in a rotor, are combined. CONSTITUTION:The electrode pattern of driving oscillators 1-3 or piezo-electric elements are divided so as to have an interval corresponding to a predetermined wave length or 1/4 wave length, for example. A stator 1-1, connected to the piezo-electric elements 1-3, is combined with a pressure detector 1-4 accommodated in a rotor 1-2. The pressure detector 1-4 provided in the rotor 1-2 detects a contacting pressure corresponding to the crest and trough of bent traveling wave oscillating the stator 1-1. A pressure detected by a pressure detecting unit 1-5 is converted into an electric signal and is inputted into a phase difference detecting unit 1-7 as an oscillating signal 1-a. On the other hand, a signal 1-b, branched from a driving signal power supply 1-6 supplying a power to the stator 1-1, is inputted into a phase difference detector 1-7 together with said signal 1-a. According to this method, the detection of the rotating angle of the rotor 1-2 can be made highly accurate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a vibration wave motor using ultrasonic waves as a driving source, and particularly to a vibration wave motor having a rotation angle detection function.

[Conventional technology]

First, the configuration of a traveling wave type vibration wave motor having a rotation angle detection function will be explained, and then the operating principle of a vibration wave motor using traveling waves and the rotation angle detection principle of a vibration wave motor will be explained.

Because vibration wave motors are small, lightweight, and generate large torques at low speeds, they are being actively researched and developed by manufacturers of small electrical equipment and by mechanical and electrical universities. There are examples of it being built into cameras, and its practical use is progressing. However, in order to actually use a motor built into a device, it is essential to detect and control the rotation angle and rotation speed. In conventional technology, it is difficult to detect the rotation angle of a single vibration wave motor by itself, and therefore an external detector such as an encoder is provided. Therefore, the inventor of the present invention developed a small and lightweight piezoelectric element.
We have invented a method to detect the rotation angle of a motor by taking advantage of the characteristics of a vibration wave motor, such as driving by a constant vibration mode and frictional contact, and have been conducting research and development on a traveling wave ultrasonic motor with a rotation angle detection function. This traveling wave type ultrasonic motor with a rotation angle detection function has been described by the present inventor in the Nikkan Kogyo Shimbun (IO 26, 1986) ``High Precision Ultrasonic Motor''.
Nikkei Menical (1989/3-20) ``Small and lightweight new actuator that points to 0'' ``Detection of position without encoder'', etc., was introduced, and the patent was also applied for in 1989.
No. 157289, Japanese Patent Application No. 18416/1983, etc. have been filed.

FIG. 4 shows a typical configuration example of a conventional vibration wave motor.

As shown in the upper part of FIG. 4, a vibration wave motor using a traveling wave has a resonator 4-8 made of an elastic body and a resonator 4-8 having a similar shape to the resonator 4-8 on the back side of the resonator 4-8. 3 are joined to form an integrated stator 4-1. Stator 4-1
The rotor 4-2 is shown on the right side. The rotor 4-2 has a pressure detector 4-4 sandwiched between a lining 4-9 and a rotor substrate 4-10, and presses the lining 4-9 with a predetermined pressure using a pressurizer 4-11 such as a chrysanthemum-shaped spring. do.

An electric signal is supplied to the vibrator 4-3 by a drive signal power source 4-6. The synchronization signal branched from the drive electric signal generated by the drive signal power source 4-6 and the signal obtained from the pressure detector 4-4 built into the rotor 4-2 are input to the phase difference detection section 4-7, and the phase difference is be compared. A phase difference signal corresponding to the rotation angle of the rotor is output from the phase difference detection section 4-7.

A piezoelectric element is generally used as the vibrator 4-3, and as shown in FIG. The two electrode groups are arranged to be shifted by λ/4 (λ is the wavelength of the natural vibration mode of the stator 4-1) in the circumferential direction. Further, each electrode is divided into electrode portions 5-3 by an insulating portion 5-4. Decide on the angle so that they correspond to the same voltage. Further, the directions of polarization of adjacent electrodes are alternately reversed as shown by the + and - symbols in FIG. And electrode group 5-
Electrode groups 5-1 and 5-2 can be connected by covering the surfaces of 1.5-2 with conductive paint or by connecting them with conductive wires.
Each electrode in the circuit is combined into one signal line.

The pressure detector 4-4 uses a piezoelectric element, which is a piezoelectric material. The pressure detection unit 4-5 is an electrode provided in a part of the pressure detector 4-4, and this pressure detection unit 4-5 detects the vibration of the traveling wave excited in the stator through the sliding material of the rotor. The configuration is such that it is detected as a change in the pressing force between the stator and rotor.

Next, the principle of driving a vibration wave motor using traveling waves will be explained.

First, a vibration waveform with a temporal phase shifted by π/2 [rad] obtained from the drive signal power source 4-6 shown in FIG.
When phase signals are applied to the electrode groups 5-1 and 5-2, the electrodes alternately expand and contract in the circumferential direction, causing bending vibrations in the stator 4-1 due to the bimetallic effect. the result,
The positions of the electrode 5-1 and the electrode 5-2 are both π/
Two standing waves with wavelengths corresponding to the lengths of the two electrodes shifted by 2 [rad] are generated, and these waves reach the stator 4-
1 and becomes a traveling wave. In this way, a progressive flexural vibration is generated in the stator 4-1 by inputting a signal having a vibration waveform. The traveling wave on the stator 4-1, as shown in the explanatory diagram of FIG. 6, focuses on one point 6-3 on the surface of the stator 6-1. Draw -4.

The rotor 6-2 is in contact with the apex of the traveling wave of the stator 6-1, and since the rotor 6-2 can be moved by friction in the direction of the locus of the apex of the ellipse, the rotor 6-2 is in contact with the traveling direction of the traveling wave. goes in the opposite direction to the left.

Therefore, the rotor 6-2 rotates in a direction opposite to the traveling direction of the traveling wave on the stator 6-1. In order to easily explain the operating principle in FIG. 6, the rotor 6-2 and stator 6-1 are replaced with the rotor 7-2, . Stator 7-l
, the pressure detector 7-4 and the pressure detecting section 7-5 have simplified shapes, but they perform the same functions as those in FIG. 4. On the left side of Fig. 7 is the pressure detector 7 of the rotor 7-2.
-4 pressure detection part 7-5 and reference position 7 of stator 7-1
The right side of FIG. 7 shows the case where the rotor 7-2 rotates and the position of the reference position 7-7 of the stator-1 and the pressure detection part 7-5 of the rotor 7-2 is shown. This shows the case where they are different. The circumference of the stator is 5 to 7 times the wavelength.
Since the stator is designed to have a double angle, when the vibration of a traveling wave passing through a part of the stator is observed, a phase of 5 to 7 times as many as 360 degrees will appear, and therefore, a phase of all 360 degrees will appear. Therefore, in order to explain the principle in an easy-to-understand manner, the reference position 7-7 of the stator is provided at a position where the vibration of the traveling wave generated at this position matches the phase of the signal branched from the drive signal power source. As shown on the left side of FIG. 7, the pressure detection section 7-5 of the pressure detector 7-4 of the rotor 7-2
When the reference position 7-7 of the stator 7-1 matches, the vibration phases of the vibration of the stator 7-1 and the signal obtained from the rotor 7-2 match, and the phase difference is 7. -g
is small. On the other hand, when the rotor 7-2 rotates and the reference position 7-7 of the stator 7-1 and the position of the pressure detection part 7-5 of the rotor 7-2 are different, the reference position 7 of the stator
A phase difference 7-h of vibration occurs between the vibration of -7 and the signal obtained from the rotor 7-2. The phase difference changes in magnitude depending on the rotation angle of the rotor. This is the basic operation of the rotation angle detection mechanism.

Next, the rotation angle detection operation described above will be explained using a mathematical formula.

Set each variable as shown below.

A, B: Amplitude of the standing wave excited in the stator ω: Ultrasonic angular frequency θ: Angle from the reference position set on the stator n: Wave number of the wave excited in the stator, 9
The two-phase standing waves with different phases of 0 degrees are E1=A-3In(ωt)・cos(θn)
−−−−−■E2=B−cos(ωt)・s! n(θ
n) −・−■, and in the synthetic skin of these two-phase standing waves, the phase difference in position is 90 degrees and the amplitude ratio is A/B=
In the case of 1, in the formula ■, A=B and E '' E + + E 2 = A-S IN (ω is 10θn) ・-kawa・
It becomes a traveling wave shown by ■.

The traveling wave vibration of the stator represented by the formula (2) is converted into an electrical signal as a pressure change by a pressure detecting section provided in a pressure detector built into the rotor due to pressurized contact with the rotor. This signal corresponds to the steering plate caused by the traveling wave of the stator passing through the pressure detection section.

Therefore, B: Assuming the ratio of the output signal amplitude from the stator's vibration amplitude layer pressure detector, the signal from the rotor's pressure detector is F(θ, t
)=k −A−5IN(ωt+θ1) −−−
---■ Indicated by Chile.

If the reference position provided on the stator is the same as the position of the pressure detection part of the pressure detector provided on the rotor, E=A-8IN(ωt) using formulas ① and ②, assuming θ=O.
■F(0,t)=K −A −S I N(ωt)
・・・・・・■. Equation (2) indicates the vibration at the reference position of the stator, and Equation (2) indicates the signal obtained from the pressure detector. As shown in the equations, there is no phase difference between the two equations and they match.

On the other hand, as the rotor rotates, the reference position provided on the stator and the position of the pressure detection part of the pressure detector provided on the rotor change to m [ra
d] If it is different, in formula (■) it is vibration at the standard position of the stator, so set θ=0, and in formula (2), the position of the pressure detection part of the rotor is at the same level as the standard position of the stator, so 02m Then, E=A-8IN(ωt)...
■F(0,t)=to-A-3IN(ωt++n-n)
＋＋＋・＋・■. Equation (2) represents the vibration at the reference position of the stator, and Equation (2) represents the signal obtained from the pressure detector. 2
There is a phase difference of two equations m−n [rad]. By the way, n is the wave number of the traveling wave and is known at the time of design, so the rotation angle m [ra
d] can be detected.

Note that the phases of the vibration at the reference position 7-7 of the stator and the signal branched from the drive signal power source are made to match. Therefore, by detecting the phase difference between the signal branched from the drive signal power source and the signal output from the pressure detector of the rotor, the same operation as described above can be obtained in the form of an electric signal.

[Problem to be solved by the invention]

According to the configuration described in the above-mentioned conventional technology,
Logically, the rotation angle of a vibration wave motor can be detected by the phase difference, but the electrode/polarization pattern of the piezoelectric element that excites the stator excites two-phase standing waves with different phases in semicircular units. A non-uniform traveling wave is excited in the stator in order to combine the waves into a traveling wave. In order to detect this non-uniform traveling wave in the rotor, the phase difference between the signal from the stator drive signal power source and the signal obtained from the rotor's pressure detector has a nonlinear correspondence with the actual rotation angle. This has the disadvantage that an error occurs in detecting the rotation angle.

[Means to solve the problem]

The vibration wave motor of the present invention includes a stator including a vibrator that inputs an electric signal having a vibration waveform having a frequency in the ultrasonic range and converts it into mechanical vibration, and an annular resonator coupled to the vibrator; A vibration wave motor comprising an annular rotor pressurized and in contact with the stator, wherein the rotor includes a pressure detector having a pressure detection section that partially detects pressure between the stator and the rotor. The electrode pattern of the piezoelectric material that constitutes the resonator is provided with a plurality of electrodes arranged radially at intervals corresponding to 1/4 of the wavelength of the vibration of the resonator, and the electrodes are connected to four adjacent electrodes. As one set of electrodes, +, 10.

Polarization is performed in the order of -, and the connection of the drive signal is such that the electrodes arranged every other place are electrically connected together, and the remaining electrodes arranged every other place are also electrically connected together. , a total of two sets of drive signal lines are provided, and
A drive signal power source that supplies two sets of drive signals having different phases and frequencies in the ultrasonic range to the two sets of drive signal lines, a detection signal obtained from the pressure detector provided on the rotor, and the drive signal. and a phase difference detection section that receives a signal synchronized with the signal and outputs a phase difference signal corresponding to the phase difference between the two.

[Effect]

In the stator drive piezoelectric element, a two-phase standing wave with the same amplitude and a vibration phase difference of 90 degrees at the stator drive frequency and a 90 degree shift in time is generated at any position of the stator. An ideal traveling wave is excited when excited with equal amplitude. However, in the conventional electrode division pattern shown in Figure 5, a standing wave is excited every half circumference, and the standing wave excited at one electrode group is not attenuated and has the same strength throughout the circumference of the stator. It is difficult to propagate. That is, two standing waves are excited with the same amplitude at all positions of the stator. The state of the traveling wave created by combining the two biased standing waves described above is expressed by a mathematical expression.

A, B: Input voltage amplitude ω: Ultrasonic angular frequency θ: Position on the stator n: Wave number of the wave excited in the stator,
The two-phase standing wave is E+=A-sin(ωt) ・cos(θn)
・−=−■E2=B−cos(ωt) ・5in(
θn ) ----- ■ If the amplitude ratio in the synthetic skin of these two-phase standing waves is A/B = 1, as mentioned above, in the formula ■, A = B, E = E, +E2 = A-S IN (ωt+θn)...
It becomes a traveling wave shown by −・−■.

On the other hand, when the amplitude ratio A/B of equations (■) and (■) is changed appropriately, the change in phase difference with respect to the rotation angle is no longer linear, and two cycles occur while the phase of one wavelength of the traveling wave changes. Indicates a varying error. That is, E=A-sin(ωt)cos(θn)+B-cos(
ωt) sin(θn)A' ・cos2(θn)+(A
-cos(θn)+B-5IN(θ・n))2XSIN
(φ + ωt) Here, φ indicates the amount of phase modulation, and the signal from the pressure detector installed at q is: F=K・( A-3ln(ωt)・C08(θn)+B-
cos(ωt) sin(θn))=k−A”cos
'(θn)+(A-cos(θn)+B-5IN(θ-
n))' xSIN(φ+ωl)φ=ArcTan((
B/A)tan(θn)), where φ indicates the error in rotation angle detection.

The above φ is wave number n=5, rotor rotation angle O〈θ〈2π15
A graph of this is shown in Figure 8. The vertical axis of the graph shows the rotation angle detection error φ[DEC], and the horizontal axis shows the rotor rotation angle θCrad]. In the graph, as shown in the equation, a two-cycle fluctuation error appears while the phase of the traveling wave changes by one wavelength (that is, 0 × θ × 2π15).

Now, in the configuration according to the present invention, the electrode pattern of the piezoelectric element, which is a vibrator that excites traveling waves, is divided into 1/4 wavelength units, and when every other electrode is connected, + and - polarization directions appear alternately. . Connecting the remaining electrodes,
Again, every other one is connected, but like the former, the + and - polarization directions appear alternately. Since the interval between every other electrode is 1/2 wavelength and the polarization direction is opposite, there are two gaps of 1/4 wavelength each, but this corresponds to unevenness with a - set of standing waves. Similarly, the remaining every other electrode is polarized in the opposite direction at 1/2 wavelength intervals, so it corresponds to the unevenness of the - set of standing waves, except for two locations at 1/4 wavelength intervals. do. As a result, two sets of standing waves can be excited alternately and independently with a distance of 1/4 wavelength. When a traveling wave with five wavelengths is excited in the stator, the length of 1/4 wavelength corresponds to 1/(4 times the wave number) or 1/20 of the circumference of the stator, and therefore This eliminates the need to excite two standing waves separated by half a stator rotation as in the case of the electrode pattern. Therefore, the two standing waves can be excited more uniformly over the entire stator speed than in conventional printing. Therefore, compared to the conventional configuration, it is possible to excite the stator with a uniform traveling wave as shown in equation (2). By detecting a uniform traveling wave close to the formula (2) in the rotor pressure detector, it is possible to reduce errors in rotation angle detection relative to the actual rotor rotation angle.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram including a perspective view of an embodiment of the present invention;
FIG. 2 is a front view showing electrode division and polarization patterns of the vibrator shown in FIG. 1, and FIG. 3 is a block diagram illustrating in detail the phase difference detection section shown in FIG. 1.

In FIG. 1, a resonator 1-8 is an annular resonator made of an elastic material such as phosphor bronze or aluminum bronze. A vibrator 1-3 is bonded to the lower surface of the resonator 1-8, forming a stator 1-1. The vibrator 1-3 uses a piezoelectric element with a thickness of 0.5 mm that exhibits piezoelectricity, and the electrodes are divided into lengths corresponding to 1/4 wavelength of the traveling wave vibration excited by the stator, and the electrodes are divided into two pieces each having a length corresponding to 1/4 wavelength of the traveling wave vibration excited by the stator. Polarization is taking place. The rotor 1-2 is constructed such that a pressure detector 1-4 is sandwiched between a lining 1-9 and a rotor substrate 1-10, and the lining 1-9 is moved by a chrysanthemum-shaped spring or the like that generates a compressive force of 2 kgf to 5 kgf. Press with the pressurizer 1-11. The material of lining 1-9 is highly abrasion resistant,
Furthermore, synthetic plastics having a large coefficient of friction are used, and a piezoelectric element made of a piezoelectric material with a thickness of 0.5 mm is used for the pressure detector 1-4. The electrodes provided in a part of the pressure detector 1-4 use a pattern that detects changes in the pressing force between the stator and the rotor through the vibration of a traveling wave excited in the stator through the sliding material of the rotor.

FIG. 2 shows in detail the electrode division and polarization pattern of the piezoelectric element which is the vibrator 1-3 shown in FIG. Second
In the figure, a conductive thin film made of components such as silver and gold is formed on the surface of the piezoelectric element, and is divided into electrode parts 2-3 each having 174 wavelengths by an insulating part 2-4 where no thin film exists. By connecting every other electrode section 2-3, polarization is performed so that + and - polarization directions appear alternately. Similarly, even if the remaining electrodes are connected every other electrode, polarization is performed so that + and - polarization directions appear alternately.

The spacing between the two electrodes is 1/2 wavelength, and the polarization direction is opposite, so in order to excite the other standing wave, two electrode parts of 1/4 wavelength each are removed, but in the - group. Corresponds to the unevenness of standing waves. Similarly, the remaining every other electrode is 1
/2 wavelengths apart and oppositely polarized, so 1
/4 wavelengths, excluding two locations, corresponds to the unevenness of the - set of standing waves.

Due to the pattern of electrode division and polarization direction as shown in Figure 2, two sets of standing waves can be excited alternately and independently at intervals of 1/4 wavelength.

Now, an electrical signal (for example, a sinusoidal ultrasonic wave of 42 kHz, ±100 square meters) is input to the vibrator 1-3 of the stator 1-1 to excite the bending traveling wave of the stator 1-1. As previously explained with reference to FIG. 6, the vibrator 1-3 generates vibration having an elliptical locus due to the generation of a bending traveling wave in the stator 1-1. By pressurizing and contacting the lining 1-9 with the lining 1-9 by a pressurizer 1-11 using a chrysanthemum-shaped spring, rotational movement is generated in the rotor 1-2.

The pressure detector 1-4 provided on the rotor 1-2 has a diameter of 3
An annular piezoelectric element with a thickness of 0.5 mm and a thickness of 0.5 mm is used.

The other surface of the pressure detector 1-4 is joined to the rotor substrate 1-10. Pressure detector 1- installed on rotor 1-2
4 detects the contact pressure corresponding to the peaks and troughs of the bending traveling wave that excites the stator 11 as described above. The pressure detected by the pressure detection section 1-5 is converted into an electrical signal and inputted to the phase difference detection section 1-7 as a vibratory signal 1-a.

On the other hand, drive signal power supply 1-6 supplied to stator 1-1
The signal 1-b branched from the signal 1-b is input to the phase difference detection section 1-7 together with the above-mentioned signal 1-a.

FIG. 3 is a block diagram showing details of the phase difference detection section 1-7. As shown in FIG. 3, each signal 1-a is input to a band pass filter 3-2, and a signal component whose center frequency is the frequency of vibration of the stator 1-1 is extracted. This signal is converted by the zero cross comparator 3-2 into a pulse signal whose positive and negative vibration waveforms correspond to 9'1'' and "0", respectively, and is output. 3 detects the phase difference, and outputs an output signal 1-C proportional to the rotation angle.

〔Effect of the invention〕

As explained above, in the vibration wave motor of the present invention, the electrode pattern of the piezoelectric element, which is the drive vibrator, is divided by 1/4 wavelength, and the piezoelectric element is joined to the stator and the rotor, which have built-in pressure detection. By combining with the
The rotation angle of the rotor can be detected more accurately with less error than in the past, and there is an effect that a vibration wave motor having a built-in rotation angle detection function with higher precision can be obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram including a perspective view of an embodiment of the present invention;
Fig. 2 is a front view showing the electrode division and polarization pattern of the vibrator shown in Fig. 1, Fig. 3 is a block diagram explaining in detail the phase difference detection section shown in Fig. 1, and Fig. 4 is A block diagram including a perspective view showing an example of a conventional vibration wave motor, FIG. 5 is a front view showing the electrode division and polarization pattern of the vibrator in the conventional example, and FIG. 6 shows the driving principle of the vibration wave motor. FIG. 7 is an explanatory diagram illustrating the principle of rotation angle detection, and FIG. 8 is a diagram showing an error in rotation angle detection due to two standing waves with different amplitudes. 1-1.4-1.6-1.7-1...Stator, 1-2.4-2.6-2.7-2...Rotor,
l-3゜4-3... vibrator, 1-4.4-4...
... Pressure detector, l-5, 4-5 ... Pressure detection section, 1-8.4-8 ... Resonator, 1-6.4-
6... Drive signal power supply, 1-7.4-7...
- Phase difference detection section, 1-a. 1-b, 1. -c... Signal, 7-7...Reference position, 7-g, 7-h...Phase difference, 1-9.1
-9... Lining, 1-10.4-10...
...Rotor board, 1-11.4-11...
Pressurizer, 1-12,412... Shaft, 3-1...
... Bandpass filter, 3-2 ... Zero cross comparator, 3-3 ... Phase detector, 2-3.5-3
...Electrode part, 2-4.5-4...Insulation part, 5
-1.5-2... Electrode group. Collar 2 Figure Shoulder 6 Figure Arrow 7

Claims (1)

[Claims] a stator having a vibrator that inputs an electric signal having a vibration waveform having a frequency in the ultrasonic range and converts it into mechanical vibration; and an annular resonator coupled to the vibrator; and a stator that is pressed into contact with the stator. In the vibration wave motor, the rotor includes a pressure detector having a pressure detection section that partially detects pressure between the stator and the rotor, and the vibration wave motor includes a pressure detector that partially detects pressure between the stator and the rotor, and The constituting piezoelectric electrode pattern has a wavelength of 1/1 of the vibration wavelength of the resonator.
A plurality of electrodes are provided radially at intervals corresponding to
, −, − in the order of polarization, and the drive signal is connected by connecting the electrodes arranged at every other interval together, and also connecting the remaining electrodes arranged at every other interval together. conduction to provide a total of two sets of drive signal lines,
and a drive signal power source that supplies two sets of drive signals having different phases and frequencies in the ultrasonic range to the two sets of drive signal lines; a detection signal obtained from the pressure detector provided on the rotor; A vibration wave motor comprising: a phase difference detection section that receives a signal synchronized with a drive signal and outputs a phase difference signal corresponding to a phase difference between the two.