JPH0241676A - Oscillating wave motor - Google Patents

Abstract

PURPOSE:To detect an angle of rotation highly precisely by constituting a pressure detector to detect the contact state of a rotor with a stator by the use of two detection sections provided to the position apart by a specified phase angle. CONSTITUTION:An oscillating wave motor is composed of a stator 3-3 consisting of a resonator 3-1 and an oscillator 3-2 and a rotor 3-5 consisting of a lining 3-4, etc., and is equipped with a phase difference detection section 3-11 and a motor driving power source 3-13. A pressure detector 3-6 is provided to this rotor 3-5. This detector 3-6 is divided into two pressure detection sections 4-1 to 4-2 at an angle. Insulation sections 5-1 to 5-2 are provided both between then and onto their sides. A signal 3-15 taken out of a part of the driving signals from the driving power source 3-13 and output signals 3-14a to 3-14b from the pressure detector 3-6 are inputted into the phase difference detection section 3-11 and an angle of rotation can be obtained. A flexural travelling wave is generated to the stator 3-3, so that a rotating movement is generated to 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. 10 is an exploded perspective view showing the main parts of an example of a conventional vibration wave motor, and Fig. 11 is
FIG. 12 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 shown in FIG.
a), (b), and (C) are explanatory diagrams showing examples of different combinations of a vibration wave motor and a rotary encoder.

In general, an annular vibration wave motor that uses traveling waves is
As shown in FIG.
The stator 1-3 has a stator 1-3 which is integrated by bonding the stator 1-2. As the vibrator used here, a piezoelectric element, which is a type of ceramic, is often used. Stator 1-
Above 3, 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. The sliding surface of the rotor 10-5 with the stator 1-3 is made of a wear-resistant material (for example, a composite plastic material with aromatic polyamide fiber as a filler and polyurethane resin as a material). By providing the lining 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 linings 2-4 are in contact with the top of the traveling wave of the stator 2-3. Since the rotor 2-5 is moved by friction in the direction of the locus 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 control the device by detecting its rotation angle. A conventional means that has been widely used to detect 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. 11, the rotational motion output from the output shaft 0-9 of the vibration wave motor 11-1 is transmitted to the detection shaft 1-5 of the rotary encoder 12, and the rotary motion is transmitted to the rotary encoder 11-2. The rotation angle is transmitted as an electrical signal.

FIG. 12 shows examples of several combinations of such a row encoder and a vibration wave motor.

In FIG. 12(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. 12(b) is an example in which a rotary encoder 124 of a shaft-through type is used and a rotary encoder 12-4 is disposed in front of a vibration wave motor 12-3. In these two examples, since the row encoder is arranged in series with the vibration wave motor, the overall length in the axial direction becomes long. FIG. 12(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 the backlash in the gear train 12-7 is Moreover, since the two rotating shafts are arranged in parallel, an extra space is required for the rotary 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 provided on the rotor for detecting pressure between the stator and the rotor, the pressure detection means At least one set of pressure detection groups each having two types of pressure detection units are arranged at a predetermined phase angle with an insulating part in between, and the signals output from each of the two types of pressure detection units are connected in parallel. or a phase difference detection unit that inputs two signals connected to the toroidal resonator and a signal branched from the signal input to the annular resonator and detects the phase difference between them; An amplitude detector is provided on a part of the circumference to detect the amplitude of the vibration of the input electric signal, and the output signal from this amplitude detector is used to input the signal input to the annular resonator into a branched signal. The signal 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 phase of the vibratory signal detected in the rotor due to the presence or absence of contact with the stator and the amplitude of the traveling wave generated in the stator or the phase of the vibratory signal supplied to the stator is determined by the rotation angle of the rotor. It changes depending on. The present invention detects the state of contact between the rotor and the stator using a pressure detector such as a piezoelectric element. At this time, as shown in FIG. 3, two pressure detecting sections 4-1 and 4-2 are provided at positions separated by a length corresponding to the phase angle α set at the time of designing the pressure detector 1-6. Furthermore, the vibration of the stator is detected by using a signal supplied to the stator or a signal output from a part of the piezoelectric element that excites the traveling wave in the stator, and the amplitude of the traveling wave is detected. The rotation angle of the rotor is detected by comparing the phase with the signal obtained from the change in the contact pressure between the rotor and the stator described above (there are multiple pressure detection parts as described above). be.

FIG. 4 is an explanatory diagram showing the state of change in the contact between the traveling wave excited in the stator and the rotor when the pressure detection section of the rotor is at a rotational position having a rotation angle m with respect to the stator. As shown in FIGS. 4(a) to 4(d), the rotor 3-5
The contact point between the stator 3-4 and the stator 3-4 sequentially moves as the signal (travelling wave) supplied to the stator 3-4 advances.

FIG. 5 shows the state of change in the output signals 3-14a and 3-14b from the two pressure detection units 4=1 and 4-2 separated by the phase angle α provided on the rotor in FIG. It is a graph showing the state of signal 3-15 from the motor drive power supply supplied to the stator.

As shown in FIG. 5, there is a phase difference (mn> or (mn
10αn) is generated, and this phase difference (mn) or (mn+α
n), the rotation angle can be calculated.

This will be explained below using mathematical formulas.

FIGS. 6(a) and 6(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. 6, 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.

To excite a traveling wave in the stator, the electrical signal supplied to the oscillator is ξ−A 5in(ωt) −(
1) ξ= A cos(ωt)
-(2). Here, (Al (rad/5ec
) is the angular frequency, A (v) is the amplitude, and t (sec) is the time.

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

In order to convert and organize the polar coordinates provided on the stator, f(
Frequency (period) of the signal that supplies 1-1z) to the stator
, θ (rad) is the position on the stator, n is the wave number of the traveling wave excited in the stator, r (m) is the radius of the stator ring, then λ-2πr / n ... (6
) θ−x / J− (7), and these can be expressed as (1), (2), and (5
), then ξ1 = A 5in(2yr ft)
−(8) ξ2 = A cos(2yr ft)
-(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 detection group provided on the rotor separated by the position of phase angle α is (θ-0) in polar coordinates set on the stator.
), that is, the pressure detection part is at the position (θ
-0) and (θ-α), the oscillatory signal output from the pressure detector part of the rotor is expressed as (θ-〇) and (θ=0+α) in equation (10), ζ1=Bsin (2πft> −(
11) ζ2 = B 5in (2yr ft - an
) −(12).

The vibration signal output from the stator vibration detector is
Similarly, in equation (10), as (θ-0), 77 -C5in(2yr ft)
−(13). Here B and C(v) are amplitudes.

On the other hand, the position of the pressure detection part of the rotor 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 changes depending on the angle m. The signal output from the rotor pressure sensor is
1o) In equation (θ-m) and (θ-m+α), ζ1=B 5in(2yr ft -mn)
−(14)ζ 2 = B 5in(2
π fL-mn-a n)-(1
5).

In the present invention, the signals shown by equations 14) and (15) and the signals shown by equations (8) or (9) or (12)
) Compare the signals shown by the formula. In both cases, when the rotation angle of the rotor is (m), the phase difference obtained by comparing the signals is (mn) and (mn+αl). n and α are known when designing the stator. Therefore, the rotation angle m of the rotor can be determined by detecting the phase difference.

On the rotor, the phase angle of the stator drive vibration is 0 degrees and 18 degrees.
When p detection units are provided at positions separated by a predetermined angle excluding the angle corresponding to 0 degrees, that is, when the angle is α1α2...αP, the phase difference is There are p signals necessary for calculation. The p signals have different phase differences from each other, and therefore, compared to the case where only one detection unit is provided on the rotor, the number of signals output from the rotor detector during one rotation of the rotor is smaller. This means that it has increased by several p times. Therefore, the resolution of detection has improved by that amount.

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. For this reason, the pressure detection groups are provided at positions separated by an integral multiple of the wavelength (λ) of the vibration excited in the stator. Then, each detection group is connected as shown in FIG. 8 to obtain signals 8-14a and 8-14b. By doing this, the signal 8-14 obtained from the detection group
a and 8-14b are signals obtained by taking the average of multiple signals, and compared to signals 3-14a and 3-14b, they are closer to the signals shown in equations (14) and <15), and are noise-free. can be reduced.

In order to further reduce the noise, this noise component is eliminated by a filter whose passband is the frequency f shown by equation (15).

〔Example〕

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

FIG. 1 is an exploded perspective view showing the main parts of the first embodiment of the present invention, FIG. 3 is a plan view showing how the electrodes of the amplitude detector of the embodiment shown in FIG. 1 are divided, and FIG. FIG. 9 is a graph showing signals of the pressure detection group in the embodiment shown in FIG. 1, and FIG. 9 is a block diagram showing details of the phase difference detection section in the embodiment shown in FIG.

In FIG. 1, 3-1 is an annular resonator made of an elastic material such as phosphor bronze or aluminum bronze.
3-2 is an electric vibration signal (e.g. 55 kHz, ±7
0V sinusoidal ultrasonic waves) are input to excite the bending traveling wave of the stator 3-3. This vibrator 3-2 is first
As explained with reference to the drawings, vibrations having an elliptical locus F are generated by the bending traveling wave generated in the stator 3-3. By pressurizing and contacting the lining 3-4 with the disc spring 3-8 by applying this vibration, rotational movement is generated in the rotor 3-5.

3-6 is a pressure sensor whose voltage changes in response to strain caused by pressure in the axial direction, and is an annular pressure sensor with a diameter of 30 mm and a thickness of 30 mm, made of a piezoelectric ceramic material such as PZT. . Stator 3 of pressure detector 3-6
A lining 3-4 made of engineering plastics with excellent abrasion resistance is adhered to the surface in contact with the lining 3-3. As described above, the pressure detector 3-6 provided on the rotor detects the contact pressure corresponding to the state of the bending traveling wave excited in the stator 3-3. The pressure detector 3-6 is
As shown in FIG. 3, it is divided into two pressure detecting sections 4-1 and 4-2 forming an angle of α degrees, and insulating sections 5-1 and 5-1 are provided between them and on their sides. 2 are provided.

In the embodiment of FIG. 1, as shown in FIG. 1, a portion of the drive signal from the motor drive power source 3-13 that supplies power to the stator 3-3 is extracted after adjusting the gain with a resistor. The output signals 3-15 and the plurality of output signals 3-14a and 1-14b output from the pressure detector 3-6 are input to the phase difference detection section 3-11 to obtain output signals 3-12a and 312b. The rotation angle can be obtained by calculating the phase difference α and the wave number.

FIG. 9 is a block diagram showing details of the phase difference detection section 3-11.

Signals 3-14a and 3-14b and 314. shown in FIG. n is input to band pass filters 7-3a, 7-3b and 7-30, respectively, and is input to stator 3-3.
A signal component whose center frequency is the frequency of vibration No. 3 is extracted. These signals are connected to amplifiers 7-8a and 7, respectively.
-8b and 78n, the positive and negative vibration waveforms are amplified by zero cross comparators 7-6a, 7-6b and 7-6n, and are output after being converted into pulse signals corresponding to "'1" and "O"', respectively. .

These pulse signals are sent to phase difference detectors 7-7a and 7-
The phase difference is detected by 7n and output as signals 3-12a and 3-1.2b proportional to the rotation angle.

In addition, as the above-mentioned pressure detector, there is also a method of using polyvinylidene fluoride (PVDF), which is a piezoelectric polymer, or a method of using a strain gauge instead of the piezoelectric element. When using PVDF, its thickness is approximately 100 μm, which is thinner than a piezoelectric element, so that the pressure detection mechanism can be made thinner.

FIG. 13 is an exploded perspective view showing the main parts of a second embodiment of the present invention, and FIG. 7 is a plan view showing the vibrator of the embodiment of FIG. 13.

In the embodiment of FIG. 13, a part of the vibrator 6-2 bonded to the stator 6-3 is as shown in FIG.
An amplitude detector 6-2 for detecting the amplitude of a traveling wave divided by providing two insulating parts 6-2c between them.
d. The signal 6-15 from the amplitude detector 6-2d and the output signals 6-14a and 6-14b from the pressure detectors 6-6 of the rotors 6-5 are input to the phase difference detection section 6-11. Signal 6 to calculate rotation angle
12a and 6-12b.

FIG. 14 is a plan view showing a pressure sensor according to a third embodiment of the present invention, and FIG. 8 is a plan view showing an electrical connection state of the pressure sensor shown in FIG. 14.

The pressure detector 8-6 shown in FIG. 14 includes a plurality of pressure detection groups 95 at positions separated by an angle that is an integral multiple of the wavelength λ.

Each pressure detection group 9-5 has two pressure detection parts 9-1 and 9-2 forming an angle α with an insulating part 9-3 in between, and insulating parts 94 on both sides thereof. There is. The pressure detection section 8-6 configured in this way is connected as shown in FIG.

That is, a plurality of pressure detecting sections 9-1 and 9-2 are respectively connected in parallel and signals 8-14a and 8-14b are taken out from each.

Signals 8-14a and 8-14 thus obtained
b is signal 3 14a and 3-14 of the embodiment of FIG.
It is possible to obtain a signal with fewer noise components compared to signal b. Both signals 8-14a and 8-14b are input to the phase difference detection section.

〔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 of providing a vibration wave motor with a simple configuration. Additionally, since the rotation angle can be detected at intervals equal to or greater than the stator's resonant frequency, the rotation angle can be detected with high resolution, resulting in a vibration wave motor that is low cost, compact, and has excellent resolution. .

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view showing the main parts of the first embodiment of the present invention, FIG. 2 is an explanatory view showing the state of vibration of the stator due to traveling waves of a general vibration wave motor, and FIG. 1 is a plan view showing the pressure detector of the embodiment, FIG. 4 is an explanatory diagram showing the state of change in the contact between the traveling wave excited in the stator and the rotor, and FIG. Graph showing changes in pressure and changes in signal supplied to the stator, Figure 6 (a
) and (b) are a plan view and a sectional view showing the coordinate axes provided on the stator for calculating the rotation angle of the vibration wave motor, FIG. 7 is a plan view showing the vibrator of the embodiment shown in FIG. 13, FIG. 8 is a plan view showing the electrical connection state of the pressure detector of the embodiment shown in FIG. 14, FIG. 9 is a block diagram showing details of the phase difference detection section of the embodiment shown in FIG. 1, and FIG. FIG. 11 is a front view including a partial cross section showing an example of a conventional vibration wave motor; FIG. 11 is a front view including a partial cross section showing a state in which the example of FIG.
Figures (a), (b), and (c) are explanatory diagrams showing examples of different combinations of a vibration wave motor and a rotary encoder,
FIG. 13 is an exploded perspective view showing the main parts of a second embodiment of the present invention, and FIG. 14 is a plan view showing a pressure detector according to a third embodiment of the present invention. 1-1, 2-1, 3-1...resonator, 1-2, 22,
3-2, 6-2... vibrator, 1-3, 2-3, 3-3
・6-3...Stator, 1-4・2-43-4...
Lining, 1-5...Detection axis, 2-5, 3-5, 6
-5・10-5...Rotor, 1-6・36・6-6・
8-6...Pressure detector, 1-8.38... Belleville spring,
10-9...Output shaft, 3-11.61], --.Phase difference detection section, 3-12a-3-12b3-14a.3-
14b-3-158-14a/8-14b...Signal, 3
-13... Motor drive power supply, 4-1, 4-2, 9-1,
9-2...Pressure detection section, 4-3...Pressure detection group, 5
-1, 5-2, 62c, 9-3, 9-4...Insulation section,
6-2d... Amplitude detection section, 6-6... Pressure detection strain gauge, 7-3a, 7-3b, 7-3n... Band pass filter, 76a, 7-6b, 7-6n...・Zero cross comparator, 7-8a -7-8b -7-8n-
...Amplifier, 7-7a 7-7n...Phase difference detection section, 11-1, 12-1, 12-3, 12-5...Vibration wave motor, 11-2, 12-2, 12- 4.12-6.
...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 is provided with an annular rotor that is in contact with the rotor, and includes pressure detection means for detecting pressure between the stator and the rotor, which is provided on the rotor, the pressure detection means sandwiching an insulating part between the vibration wave motor and the rotor. At least one pressure detection group having two types of pressure detection units arranged at a predetermined phase angle is provided, and the signals output from each of the two types of pressure detection units are connected in parallel. A vibration wave motor comprising a phase difference detection unit that receives a signal and a signal obtained by branching the signal input to the annular resonator and detects a phase difference between the signals. (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.