JPH0241674A - Oscillating wave motor - Google Patents

Abstract

PURPOSE:To detect an angle of rotation of a rotor by detecting the amplitude of travelling waves of a stator by the use of a part of a piezoelectric element and by comparing the phase of this signal with that of a contact pressure signal of the rotor with the stator. CONSTITUTION:An oscillating wave motor is composed of a stator 3-3 consisting of a resonator 3-1 and an oscillator (piezoelectric element) 3-2, a rotor 3-5 having an output shaft 3-9, and so on. It is also equipped with a phase difference detection section 3-11 and a motor driving power source 3-13. A pressure detector 3-6 ad a difference signal generation section 3-18 are provided. The pressure detector 3-6 provided to this rotor 3-5 which varies voltage with the axial pressure detects contact pressure corresponding to the crest and trough of flexural travelling waves that excites the stator 3-3. On that account, the space of a pair of pressure detection sections 4-2 of the pressure detector 3-6 is set at 36 deg. equivalent to 1/2 wavelength of a wavelength lambda of an exciting wave. Together with the pressure detection section 4-1 the pressure detection sections 4-2 constitute a pressure detection group 4-3. These signals are inputted into a difference signal generation section 3-18 altogether. Flexural travelling waves are thereby generated to rotate the rotor 3-5.

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.

[Conventional technology]

Fig. 2 is an explanatory diagram showing the state of vibration of the stator due to the traveling wave of a general vibration wave motor, Fig. 8 is a front view including a partial cross section showing the main part of an example of a conventional vibration wave motor, and Fig. 9 10 is a front view including a partial cross section showing a state in which a rotary encoder serving as a rotation angle detector is combined with the example in FIG. 8;
Figures (a), (b), and (c) are explanatory diagrams showing examples of different combinations of a vibration wave motor and a rotary encoder.

Generally, an annular vibration wave motor that uses traveling waves is
As shown in the figure, on the back side of the annular elastic resonator 1-1, an annular vibrator having the same shape as the resonator]-1]-
The stator 1-3 has a stator 1-3 which is made by bonding two parts together.

As the vibrator used here, a piezoelectric element, which is a type of ceramic, is often used. Stator 1-3
On the left side, there is a rotor (also an annular moving body) 105.
is provided, and is pressed with a predetermined pressure by a pressure means such as a disc spring 1-8. A lining formed of a wear-resistant material (for example, a composite plastic material containing aromatic polyamide 1 filled with fibers and polyurethane resin as a matrix) on the sliding surface of the rotor 10-5 with the stator 1-3. By providing 1-4, the stator 1
-3 wear is prevented. An electric signal having a vibration waveform is inputted to the vibrator 1-2 to generate a traveling wave deflection vibration in the stator 1-3 due to the bimetal effect. As shown in FIG. 2, the traveling wave on the stator 1-3 draws an elliptical trajectory F when focusing on one point E on the surface of the stator. The lining 2-4 is in contact with the top of the traveling wave of the stator 2-3. Since the rotor 2-5 can be moved by friction in the direction of the trajectory around the apex of the ellipse, the rotor 2-5 moves to the left in a direction opposite to the traveling direction S of the traveling wave. Therefore, the rotor 2-5 rotates in the opposite direction to the traveling direction of the traveling wave on the stator 23 (arrow R).

By the way, when a vibration wave motor is incorporated into a device and used, it is necessary to detect the rotation angle of the vibration wave motor and control the device. A widely used conventional means for detecting the rotation angle of a vibration wave motor is to attach a rotation angle detector such as a rotary encoder or a potentiometer to the rotor. That is, as shown in FIG. 9, the rotational motion output from the output shaft 10-9 of the vibration wave motor 11-1 is transmitted to the detection shaft ]-5 of the row reencoder 11-2, and the rotational motion is transmitted to the rotary motion within the row reencoder 112. and outputs the rotation angle as an electrical signal.

Examples of several combinations of such rotary encoders and vibration wave motors are shown in FIG.

In FIG. 10(a), a rotary encoder 122 is located on the back of a vibration wave motor 12-1, and the rotation angle is directly detected from the output shaft of the vibration wave motor without using a gear or the like. . FIG. 10(b) shows an example in which a shaft-through type rotary encoder 124 is used and a rotary echo motor 12-4 is disposed in front of the vibration wave motor 12-3. In these two examples, since the rotary encoder is arranged in series with the vibration wave motor, the overall length in the axial direction becomes long. FIG. 10(C) is an example in which the rotational motion of the vibration wave motor 12-5 is transmitted to the rotary encoder 12-6 via the gear train 12-7, and there is no backlash in the gear train 12-7. In addition, since the two rotating shafts are arranged in parallel, an extra space is required for the row encoder 12-6.

[Problem to be solved by the invention]

As mentioned above, when detecting the rotation angle of a vibration wave motor using a detector such as a rotary encoder or potentiometer, the mechanism for attaching the detector to the vibration wave motor is complicated, and the space required for it is also large. There is a problem with becoming. Furthermore, there is a problem in that the number of parts required for the detector and its attachment increases, and the cost also increases accordingly.

[Means to solve the problem]

The vibration wave motor of the present invention includes a toroidal stator having a vibrator that inputs an electric signal having a vibration waveform of a constant frequency and converts it into mechanical vibration, and a toroidal resonator coupled to the vibrator; A vibration wave motor comprising an annular rotor pressurized and in contact with a stator, comprising pressure detection means for detecting pressure between the stake provided on the rotor and the rotor, and the pressure detection means two pressure detection sections provided in pairs at positions separated by a length of 1/2 of the wavelength of vibration of the annular resonator; and a pressure detection section provided in the middle of the pair of pressure detection sections It has three pressure detection parts,
a difference signal generation unit that inputs a signal obtained by short-circuiting the signals output from the pair of two pressure detection units and a signal output from the third pressure detection unit and outputs a difference signal therebetween; a phase difference detection section that receives a signal output from the difference signal generation section and a signal obtained by branching the signal input to the annular resonator and detects a phase difference therebetween; An amplitude detector for detecting the amplitude of the vibration of the input electric signal is provided on a part of the circumference of the annular resonator, and the output signal from this amplitude detector is input to the annular resonator. Instead of the branched signal, it is input to the phase difference detection section.

[Effect]

A vibration wave motor is a motor that pressurizes and contacts an annular stator with an annular resonator and an annular resonator that converts electrical vibrations having a vibration waveform of a constant frequency into mechanical vibrations. As shown in FIG. 2, contact with the stator occurs at the top of the peak of the traveling wave excited by the stator. The contact position between the rotor and the stator changes depending on the movement of the traveling wave and the rotation of the rotor. Therefore, when focusing on a portion of the rotor, the presence or absence of contact between that portion and the stator is periodically repeated. Similarly, when focusing on a part of the stator, the peaks and troughs of the traveling wave passing through this part are periodically repeated. The phase difference between the cycle of contact with the stator detected by the rotor and the traveling wave vibration generated in the stator or the signal supplied to the stator changes depending on the rotation angle of the rotor. The present invention detects the state of contact between the rotor and the stator using a pressure detector such as a piezoelectric element, and detects the vibration of the stator from a signal supplied to the stator, or excites a traveling wave in the stator. The rotation angle of the rotor is determined by detecting the amplitude of the traveling wave using a part of the piezoelectric element, and comparing the phase of this stator signal with the signal obtained from the contact pressure between the rotor and stator. This is to detect.

FIG. 6 is an explanatory diagram showing changes in the contact between the traveling wave excited in the stator and the rotor.

As shown in FIG. 6, a point It progresses in sequence, and the pressure changes periodically as it progresses.

FIG. 7 shows a change in the output signal from the pressure detection section provided at point X on the rotor in FIG. 6 and a detection section for detecting the vibration amplitude of the stator or the signal obtained from the drive signal supplied to the stator in FIG. 6. It is a graph showing a signal from.

The pressure at point The supplied signal has a waveform as shown in Fig. 7(b), and a phase difference mn occurs between the pressure at point X and the signal supplied to the stator.This phase difference mn causes the vibration wave motor to rotate. The angle can be calculated.The procedure for this calculation will be explained below using mathematical formulas.

FIGS. 3(a) and 3(b) are a plan view and a sectional view showing coordinate axes provided on the stator for calculating the rotation angle of the vibration wave motor.

As shown in the explanatory diagram of FIG. 3, coordinates are determined on the stator 1-3, and an expression for the amplitude of the vibration of the traveling wave excited in the stator 1-3 is derived.

The electrical signal supplied to the oscillator to excite the traveling wave in the stator is: ξ = A 5in(ωt) −
(1) ξ= A C05(ωt)
−(2>, where (A) (rad/5e
c) is the angular frequency, A (v) is the amplitude, and j (sec) is the time.

Let the wavelength of the two input signals be λm, and ξ1 = A
5in(ωt)X cos(2πX/^) −(3
)ξ2 =-A cos(ωt)X 5in(2πX/
λ) - (4) standing waves are synthesized and δ-A sin (ωL-2πX/λ) - (5)
A traveling wave shown by is excited in the stator. Here A(v)
is the amplitude, t (sec) is the time, and x (m) is the position.

In order to convert and organize into polar coordinates provided on the stator, f
The frequency (period) of the signal that supplies (Hz) to the stator,
If θ (rad) is the position on the stator, n is the wave number of the traveling wave excited in the stator, and r (m> is the radius of the stator ring), λ-2πr / n ... (6
)θ=x/r・
...There is the relationship (7), and these can be expressed as (1) and (2).
And by substituting into equation (5), ξ+ = A 5in(2yr ft)
−(8) ξ2 = A cos(2πft)
-(9) δ = A 5in(2yr ft-
θn) −(10). Equation (10) represents the amplitude of the traveling wave excited in the stator.

By the way, the position of the pressure detector installed in a part of the rotor is
When the stator is at the position θ-0 in the polar coordinates set, the vibratory signal output from the rotor pressure detector is (θ-O) in equation (10), ξ-B 5in (2yr ft)
−(11).

Similarly, the vibration signal output from the vibration detector of the stator is expressed as (θ-〇) in equation (10), δ=C5in(2πft)
-(12>, where B and C(v) are amplitudes.

When the position of the rotor pressure detection section is (θ-m (rad)), it takes a certain amount of time for the traveling wave excited in the stator to reach the rotor detector.

Therefore, the phase difference between the vibratory signal supplied to the stator and the vibratory signal output from the rotor detector is the angle m
It changes depending on. The signal output from the rotor pressure detector is expressed as (θ-m) in equation (10), δ-B 5in (2yr ft -mn)
−(13).

In the present invention, the signal shown in equation (13) is compared with the signal shown in equation (8) or (9>).
) Compare the signal shown by equation (12) with the signal shown by equation (12).

In both cases, when the rotation angle of the rotor is m, the phase difference obtained by signal comparison is mn. n is known when designing the stator, and therefore the rotation angle m of the rotor can be determined by detecting the phase difference mn.

However, in reality, the signal output from the detector is a superposition of signals of various frequencies in addition to the signal represented by the above-mentioned trigonometric functions. In particular, low-frequency vibration noise is generated due to uneven pressure between the rotor and the stator, but in the present invention, in order to reduce the signal of this low-frequency component, as shown in FIG. ) or equation (9), a pair of pressure detection sections 4-2 are provided at an angle separated by 1/2 of the wavelength of the signal supplied to the stator, and further, another pressure detection section 4-2 is provided between the pressure detection sections 4-2. A pressure detection unit 4-1 is provided to form a pressure detection group 4-3. The two signals detected by the pair of pressure detection units 4-2 are signals whose phases are shifted by λ/2, and the wavelength of the traveling wave is λ, so when these two signals are superimposed, , the vibration components due to the traveling waves cancel each other out and decrease, leaving only a harmful low frequency component signal due to the unbalanced pressurizing force. Next, the signal 3-16 obtained from the pressure detection section 4-1 and the pressure detection section 4-
By taking the difference from signal 3-17 obtained from 2, we obtain signal 3-14 due to the traveling wave component, and this signal 3-14 is (
A signal close to the signal shown in equation 13 is obtained, and noise can be reduced.

Furthermore, in order to reduce noise, a filter whose passband is the frequency f shown by equation (13) is provided, thereby eliminating noise components.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a front view including a partial cross section showing a first embodiment of the present invention, FIG. 4 is an explanatory diagram showing division of electrodes of the pressure detector of the embodiment of FIG. FIG. 13 is a circuit diagram showing details of the difference signal generation section of the embodiment shown in the figure, and FIG. 13 is a block diagram showing details of the phase difference detection section of the embodiment of FIG.

In FIG. 1, 3-1 is an annular resonator made of an elastic material such as phosphor bronze or aluminum bronze. Vibrator (piezoelectric element) glued to the bottom surface of resonator 3-1
3-2 is an electric signal (e.g. 55 kHz, ±70V
(a sinusoidal ultrasonic wave) is input to excite the bending traveling wave of the stator 3-3. As previously explained with reference to FIG. 2, the vibrator 3-2 generates a vibration having an elliptical locus F due to the generation of a bending traveling wave in the stator 3-3. By pressurizing and bringing this vibration into contact with the lining 3-4 by the disc spring 3-8, rotational motion is generated in the rotor 3-5 and transmitted to the output shaft 3-9.

The pressure detector 3-6 provided on the rotor 3-5 is a pressure detector whose voltage changes in response to strain caused by pressure in the axial direction, and is made of a piezoelectric ceramic material such as PZT and has a diameter of 30 mm and a thickness of 1. It is an annular pressure sensor of mm. A lining 3-4 made of engineering plastic with excellent abrasion resistance is adhered to the surface of the pressure detector 3-6 that contacts the stator 3-3. The other surface of the pressure detector 3-6 is glued to the rotor 3-5.

As described above, the pressure detector 3-6 provided on the rotor 3-5 detects the contact pressure corresponding to the peaks and troughs of the bending traveling wave that excites the stator 3-3. As shown in FIG. 4, the pressure detector 3-6 has a plurality of divided electrodes. Fourth
The figure shows a case in which the stator 3-3 is excited with a wave of wave number 5, and therefore, the two pressure detection units 4-2 that form a pair
The interval is set to 36 degrees, which corresponds to 1/2 wavelength of the excitation wave wavelength λ. Another pressure detection section 4-1 is provided between these two pressure detection sections 4-2, and these pressure detection sections 4-1 and 4-2 constitute a pressure detection group 4-3. are doing. The signals from the two paired pressure detectors 4-2 are short-circuited to form a single signal 3-17, which is combined with the signal 3-16 from the pressure detector 4-2 to the difference signal generator 3-1.
Enter 18.

FIG. 12 is a circuit diagram without showing details of the difference signal generating section 3-18.

As shown in FIG. 12, signals 3-16 and 317 are
10 and is input to an operational amplifier 319 via a resistor of Ω, where they are combined and output as a signal 3-14. The output signal 3-14 from the difference signal generation section 3-18 is sent to the phase difference detection section 3-1.
Enter 1.

On the other hand, the motor drive power supply 3- supplied to the stator 3-3
A signal 3-15 extracted from a portion of 13 after adjusting the gain with a resistor or the like is also input to the phase difference detection section 3-11 together with the output signal 3-14 from the difference signal generation section 3-18.

FIG. 13 is a block diagram showing details of the phase difference detection section 3-11.

As shown in FIG. 13, signals 3-14 and 315 are
The signals are input to band pass filters 7-3 and 7-9, respectively, and signal components whose center frequency is the frequency of vibration of stator 3-3 are extracted.

After these signals are amplified by amplifiers 7-4 and 7-6, zero cross comparators 7-5 and 7-6
The positive and negative vibration waveforms are converted into pulse signals corresponding to "1" and 'O', respectively, and are output. The phase difference between these two pulse signals is detected by a phase difference detector 7-7, and a signal 3-12 proportional to the rotation angle is output.

FIG. 11 is a front view showing a second embodiment of the present invention, and FIG. 5 is a plan view showing a state in which the electrodes of the vibrator of the embodiment shown in FIG. 11 are divided.

In the embodiment shown in FIG. 11, a part of the vibrator 6-2 bonded to the stator 6-3 is provided with an insulating portion 6-2C as shown in the plan view of FIG. It is divided into two electrode groups, and an amplitude detector 6-2d for detecting the amplitude of the traveling wave is provided between them.

As shown in FIG. 5, the vibrator 6-2 has a width of λ/4 between two electrode groups 6-2a and 6-2b, in which a plurality of electrodes each having a width of λ/2 are arranged adjacent to each other alternately in positive and negative directions. One electrode group 6-
An amplitude detector 6-2d is provided between 2a and 6-2b,
Insulating portions 6-2c are provided on both sides of the amplitude detector 6-2d.

What is the signal 6-14 generated by the difference signal generation section 6-18 by inputting the signal 6-15 from the amplitude detector 6-2d and the signals 6-16 and 617 from the pressure detector 6-6? ,
The signal is input to the phase difference detection section 6-11. The rotation angle of the rotor 6-5 can be determined from the output signal 6-12 of the phase difference detection section 6-11.

In each of the embodiments described above, there is a method of using a piezoelectric polymer such as polyvinidene fluoride (PVDF) or a method of using a strain gauge instead of a piezoelectric element as a pressure detector. When using PVDF, its thickness is 100 μm
Since it is relatively thinner than a piezoelectric element, the thickness of the pressure detection mechanism can be reduced.

〔Effect of the invention〕

As explained above, the vibration wave motor of the present invention detects the rotation angle of the rotor by using the contact pressure between the rotor and the stator without using a rotation angle detection mechanism such as a rotary encoder. This has the effect that a vibration wave motor with a simple configuration can be obtained. In addition, noise components caused by uneven pressurization forces between the rotor and stator can be removed, making it possible to detect the rotation angle with high accuracy, resulting in a low-cost, space-saving, and highly accurate vibration wave motor. effective.

[Brief explanation of the drawing]

FIG. 1 is a front view including a partial cross section showing the first embodiment of the present invention, FIG. ) and (b) are a plan view and a sectional view showing the coordinate axes provided on the stator for calculating the rotation of the vibration wave motor, and FIG. 4 is a division of the electrodes of the pressure detector of the embodiment shown in FIG. 1. FIG. 5 is a plan view showing the division of the electrodes of the vibrator in the embodiment shown in FIG. 11, and FIG. 6 is an explanation showing changes in the contact between the traveling wave excited in the stator and the rotor. 7 shows the change in point X on the rotor in FIG. 6 and the change in the signal supplied to the stator in FIG. Including front view, No. 9
The figure is a front view including a partial cross section showing a state in which a rotary encoder, which is a rotation angle detector, is combined with the example of Fig. 8;
Figures 0 (a), (b), and (C) are explanatory diagrams showing examples of different combinations of a vibration wave motor and a rotary encoder, and Figure 11 shows the main part of the second embodiment of the present invention. 12 is a circuit diagram showing details of the difference signal generation section of the embodiment shown in FIG. 1, and FIG. 13 is a block diagram showing details of the phase difference detection section of the embodiment shown in FIG. 1. It is a diagram. 1-1, 2-1, 3-1...resonator, 1-2, 22,
3-2・6-2... vibrator, 1-3・2-33-3・
6-3... Stator, 1-4, 2-4, 3-4, Lining, 1-5... Detection axis, 2-5, 3-5, 6-5, 1
0-5... Rotor, 1-8, 38... Disc splash, 3-
6...Pressure detector, 3-9/10-9...Output shaft,
3-11・6-11・・Phase difference detection section, 3-12・6-
12 ・Output signal, 3-143-15・3-16・3-
17, 6-14, 615, 6-16, 6-17... Signal, 3-18, 6-18... Difference signal generation section, 4-1.
4-2...Pressure detection section, 7-3.7-9...Band pass filter, 7-4.7-8...Amplifier, 7-5.
7-6... Zero cross comparator, 7-7... Phase difference detector, 11-1, 12-1, 12-3, 12-5
...Vibration wave motor, 11-2・12-2・12-4・
126... Rotary encoder, 12-7... Gear train.

Claims (2)

[Claims] (1) An annular stator having a vibrator that inputs an electric signal having a vibration waveform of a constant frequency and converts it into mechanical vibration, and an annular resonator coupled to the vibrator; A vibration wave motor comprising a toroidal rotor that is in contact with the rotor, the vibration wave motor comprising pressure detection means for detecting pressure between the stator and the rotor, the pressure detection means being provided on the rotor, and the pressure detection means being connected to the toroidal resonator. two pressure detection sections provided in a pair at positions separated by a length of 1/2 of the wavelength of vibration; and a third pressure detection section provided in the middle of the two pressure detection sections forming the pair. and the pair 2
a difference signal generation section that inputs a short-circuited signal output from the third pressure detection section and a signal output from the third pressure detection section and outputs a difference signal therebetween; and the difference signal generation section A vibration wave motor comprising: a phase difference detection section that receives a signal output from the annular resonator and a signal obtained by branching the signal input to the annular resonator and detects a phase difference therebetween. (2) In the vibration wave motor according to claim (1), an amplitude detector for detecting the amplitude of the vibration of the input electric signal is provided on a part of the circumference of the annular resonator, and the amplitude detector A vibration wave motor characterized in that a signal inputted to an annular resonator is inputted to a phase difference detection section instead of a branched signal.