JP3113481B2 - Piezo motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric motor for rotating a rotor section by vibrating a piezoelectric element.

[0002]

2. Description of the Related Art A bolted Langevin type piezoelectric motor has been well known.
A piezoelectric motor using a cantilever torsional ultrasonic vibrator according to Japanese Patent Publication No. 0, and an ultrasonic motor according to Japanese Patent Application Laid-Open No. 63-217984 are known.

A method for controlling these piezoelectric motors (or ultrasonic motors) is disclosed in Japanese Patent Laid-Open No. Hei 4-210.
There is known a bolted Langevin type ultrasonic motor according to Japanese Patent Publication No. 784. As shown in FIG. 12, the ultrasonic motor includes a stator section 111 and a rotor (not shown) attached to an end face of the stator section 111. The stator section 111 includes piezoelectric elements 118a and 118b,
It is composed of block bodies 114 and 116 and bolts and the like (not shown). A torsional vibration sensor 130 is attached and fixed at a predetermined position on the side surface of the block body 116.

[0004] The control method of the piezoelectric motor disclosed in the above-mentioned publication discloses a method of controlling the motor drive voltage and the stator as long as the frequency of the motor drive voltage is controlled to the optimum drive frequency, no matter how the optimum drive frequency changes. The phase difference from the torsional vibration generated in the portion 111, that is, the phase angle φ always uses a constant value α °. The torsional vibration sensor 130 described above is provided to detect the phase of the torsional vibration generated in the stator portion 111. As shown in FIG. 13, the motor drive voltage Vm applied to the piezoelectric elements 118a and 118b and the torsional vibration The motor drive voltage Vm is controlled such that the phase difference φ between the output signal Vs of the torsional vibration sensor 130 and the output signal Vs, which represents the state described above, always becomes a constant value α °. At this time, the motor drive voltage Vm is controlled to the optimum drive frequency, and the most efficient motor drive can be performed.

[0005]

As described above, in order to maintain the phase difference φ between the motor drive voltage and the torsional vibration at a constant value α °, the phase of the torsional vibration must be accurately detected. For this purpose, the torsional vibration sensor 130 is mounted and fixed at a predetermined position on the side surface of the block body 116.
As described above, in the conventional ultrasonic motor, the torsional vibration sensor 130 must be attached to the outside of the stator section 111, and the retrofit to the stator section 111 is poor, and thus the assembling property is poor. Due to the vibration stress applied to the portion, there is a problem that the portion is easily broken and the durability is poor.

Therefore, the vibration sensor is connected to the stator 111
It is convenient if the vibration sensor can be taken into the inside of the stator portion 111 without being attached to the outside of the housing.
-289375. According to these publications, the same piezoelectric element as that used for vibration generation is used for vibration detection, and the piezoelectric element for vibration detection is used by sandwiching it between block bodies. In this case, durability and assemblability are improved. However, the piezoelectric elements for vibration detection disclosed in these publications are polarized in the direction of the rotation axis of the rotor portion, and have a problem that longitudinal vibration can be detected but torsional vibration cannot be detected.

Incidentally, the above-mentioned Japanese Patent Application Laid-Open No. Hei 4-21078 is disclosed.
Instead of controlling the phase difference between the motor drive voltage and the torsional vibration generated in the stator unit to a constant value according to the control method disclosed in Japanese Patent Application Publication No. 4 (1994), the motor drive voltage and the longitudinal vibration generated in the stator unit are not controlled. If the motor can be driven at the optimum drive frequency by controlling the phase difference to be constant, there is no problem even if the polarization direction of the vibration sensor is in the direction of the rotation axis of the rotor unit. The disclosed technology may be used as it is. However, in the ultrasonic motor shown in FIG. 12, the phase difference between the drive voltage and the longitudinal vibration is as shown in FIG.
Although the phase difference at 1 is φb, the phase difference hardly changes near the optimal driving frequency f1, and therefore, it is very difficult to detect the optimal driving frequency f1 by controlling the phase difference of the longitudinal vibration to be constant φb. Have difficulty.

Further, the vibration intensity of the longitudinal vibration is shown in FIG.
The intensity at the optimum driving frequency f1 hardly changes in the vicinity thereof and changes even with a load or the like. Therefore, it is very difficult to detect the optimum driving frequency f1 based on the intensity of the longitudinal vibration.

As described above, the technique disclosed in Japanese Patent Application Laid-Open Nos. Hei 4-210786 and Hei 3-289375 cannot drive the ultrasonic motor shown in FIG. 12 at the optimum driving frequency f1. It is difficult to perform the most efficient motor drive.

However, as shown in FIG. 14A, when the phase difference between the driving voltage and the torsional vibration is used, the optimum driving frequency f1 is detected by controlling the phase difference to be constant at φa. be able to. Therefore, if the phase of the torsional vibration can be detected, the most efficient motor drive can be performed.

The present invention has been made in view of the above points, and provides a piezoelectric motor having a torsional vibration sensor capable of detecting the phase of torsional vibration and having good assemblability and durability. The purpose is to:

[0012]

In order to solve the above-mentioned problems, a first aspect of the present invention has a stator section and a rotor section, and utilizes the torsional vibration generated in the stator section to rotate the rotor section. In a piezoelectric motor that performs rotation, the stator section includes a first piezoelectric element used to directly or indirectly generate the torsional vibration, and a first electrode that applies a high-frequency AC voltage to the piezoelectric element. A second piezoelectric element that is polarized in the circumferential direction of the rotor portion and detects the torsional vibration by being installed at a position other than the antinode of the torsional vibration; and an end face of the second piezoelectric element that detects the torsional vibration. A second electrode for detecting a generated voltage; and at least two blocks attached and fixed to both sides of the first and second piezoelectric elements so as to sandwich the first and second piezoelectric elements and the first and second electrodes. The piezoelectric motor comprises a body, a, characterized in that the torsional vibration generated by the vibration of the first piezoelectric element detected by said second piezoelectric element.

According to a second aspect of the present invention, in the first aspect of the present invention, the second piezoelectric element is mounted near a position of the node of the torsional vibration.

According to a third aspect of the present invention, in the first or second aspect, a phase difference between a high-frequency AC voltage applied to the first electrode and a detection voltage from the second electrode becomes a predetermined value. Control as described above.

[0015]

In the piezoelectric motor according to the first aspect, the second piezoelectric element is polarized in the circumferential direction of the rotor portion, and is sandwiched by the block so that the piezoelectric element is located at a position other than the antinode of the torsional vibration. ing. The second piezoelectric element is provided with a second electrode, so that a voltage generated on the end face of the second piezoelectric element due to torsional vibration can be taken out.

According to the first aspect of the present invention, the phase of the torsional vibration is efficiently detected by polarizing the second piezoelectric element in the circumferential direction and mounting it at a position other than the antinode of the torsional vibration. Can be. Moreover, the second piezoelectric element is sandwiched by at least two blocks like the first piezoelectric element used for generating vibration, and is not externally attached to the stator, so that the assembly and durability are improved. Can be improved.

In the piezoelectric motor according to the present invention, the second piezoelectric element is mounted near the position of the node of the torsional vibration, and the amplitude of the torsional vibration between the two end faces of the second piezoelectric element is reduced. The difference is the largest. For this reason, the intensity of the voltage output from the second electrode also becomes maximum, and the most efficient torsional vibration detection with a favorable SN ratio can be performed.

Further, in the piezoelectric motor according to the present invention, the high-frequency AC voltage applied to the first piezoelectric element and the torsional vibration appearing in the stator portion are utilized by utilizing the phase of the torsional vibration detected by the second piezoelectric element. The motor drive is performed by controlling the phase difference to be a predetermined value, and it is possible to always apply a high-frequency AC voltage having an optimum drive frequency to the first piezoelectric element, thereby maximizing the drive efficiency of the piezoelectric motor. It can be.

[0019]

Next, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram showing the entire configuration of an embodiment to which the piezoelectric motor of the present invention is applied.

The piezoelectric motor according to the present embodiment shown in FIG.
And a stator portion 20 that is driven to rotate by elliptical vibration generated on the rotor contact surface 12 which is one end surface. The rotor unit 10 includes a disk 14 that comes into contact with the rotor contact surface with a constant pressure, and a rotation output shaft 16 attached to the center of rotation of the disk 14. Therefore, when the elliptical vibration occurs on the rotor contact surface 12 of the stator section 20, the disk 14 of the rotor section 10 is driven to rotate around the rotation output shaft 16 in one direction.

The stator section 20 includes piezoelectric elements 22 and 24 and electrode plates 26 and 28 used for generating longitudinal vibration, and a piezoelectric element 30 and electrode plates 32 and 34 used for detecting torsional vibration. , An insulating plate 36, a first metal block body 38, a second metal block body 40, and a third metal block body 42 arranged so as to sandwich them from both sides, and a first metal block positioned at both ends. It includes a connecting bolt 44 for tightening and fixing the block body 38 and the third metal block body 42.

Piezoelectric element 2 used for generating longitudinal vibration
Each of the members 2 and 24 is formed in a ring shape by using a piezoelectric material such as ceramics, and is polarized in the rotation axis direction of the rotor unit 10. The two electrode plates 26 and 28 are arranged so as to be in contact with both sides of one piezoelectric element 24 over the entire surface, and drive voltage is applied to one piezoelectric element 24. In addition, one of the electrode plates 26 is
And the other electrode plate 28 is arranged so as to contact the entire surface with one end face of the first metal block body 3.
8, the other end face of the piezoelectric element 22 is also indirectly contacted via the coupling bolt 44 and the second metal block body 40, and the two electrode plates 26 and 28 drive the motor for the other piezoelectric element 22. A voltage can be applied.

The piezoelectric element 30 functioning as a vibration sensor for detecting torsional vibration is polarized in the circumferential direction, and electrode plates 32 and 34 that are in contact with the entire surface on both sides are arranged. Further, an insulating plate 36 is disposed outside one of the electrode plates 32, and the two electrode plates 32 and 34 are connected to the same potential through the second metal block body 40, the connecting bolt 44, and the third metal block body 42. The voltage generated at the end face of the piezoelectric element 30 when torsional vibration occurs can be taken out from the two electrode plates 32 and 34.

The above-mentioned piezoelectric elements 22 and 24 are used as electrodes during polarization, for example, those obtained by polishing and removing the silver and nickel surfaces after the completion of polarization.
A detailed method of polarization of the piezoelectric element 30 will be described later.

FIG. 2 is a perspective view showing a state where the stator unit 20 is assembled. As shown in the figure, the assembled stator unit 20 includes a third metal block body 42, an insulating plate 36, an electrode plate 32, a piezoelectric element 30, an electrode plate 34,
The metal block body 40, the piezoelectric element 22, the electrode plate 26, the piezoelectric element 24, the electrode plate 28, and the first metal block body 38 are connected and integrated. An external connection terminal 46 protrudes from one of the electrode plates 26 disposed on both sides of the piezoelectric element 24, and an external connection terminal 48 protrudes from the other electrode plate 28. Further, external connection terminals 50 protrude from one electrode plate 32 disposed on both sides of the piezoelectric element 30, and external connection terminals 52 protrude from the other electrode plate 34.

The two external connection terminals 46 and 48 are for applying a high frequency AC voltage having a constant frequency to the piezoelectric element 24. Further, as described above, the end face of the second metal block 40 electrically connected to the external connection terminal 48 via the coupling bolt 44 shown in FIG. In order to operate, a high frequency AC voltage having a constant frequency is applied by the second metal block body 40 and the external connection terminal 46.

The two external connection terminals 50 and 52 are
This is for detecting a voltage generated between two end faces (flat portions) of the piezoelectric element 30.
The detection voltage can be taken out to the outside by 0 and 52.

FIG. 3 is an exploded perspective view showing the detailed structure and the assembled state of the stator section 20.

A screw hole is formed at the center of each of the first metal block body 38 and the third metal block body 42 so that a male screw groove formed in the coupling bolt 44 is screwed. ing. At the center of the second metal block body 40, a bolt insertion hole 40a having an inner diameter substantially equal to the outer diameter of the coupling bolt 44 is formed.

Further, each of the piezoelectric element 22, the electrode plate 26, the piezoelectric element 24, and the electrode plate 28 has a bolt insertion hole 22a, 2 having an inner diameter larger than the outer diameter of the coupling bolt 44.
6a, 24a and 28a are formed. The inner diameter of these bolt insertion holes 22a, 26a, 24a, 28a is determined by the size of the insulating collar 54 inserted outside the coupling bolt 44 when the piezoelectric element 22, the electrode plate 26, the piezoelectric element 24, and the electrode plate 28 are assembled. It is formed so as to substantially match the outer diameter.

Similarly, each of the insulating plate 36, the electrode plate 32, the piezoelectric element 30, and the electrode plate 34 has a bolt insertion hole 36a, 3 having an inner diameter larger than the outer diameter of the coupling bolt 44.
2a, 30a, and 34a are formed, and the inner diameters of these bolt insertion holes substantially match the outer diameters of the insulating collars 56 that are inserted outside the coupling bolts 44 when assembling the piezoelectric element 30 and the like. Is formed.

To assemble the stator portion 20, first, one end of a coupling bolt 44 is screwed and fixed to the first metal block body 38, and then a collar 54 is inserted. Each of the plate 28, the piezoelectric element 24, the electrode plate 26, and the piezoelectric element 22 is inserted sequentially. Next, the second metal block body 40 and the collar 56 are sequentially inserted, and then the electrode plate 34, the piezoelectric element 30, the electrode plate 32, and the insulating plate 36 are inserted through the outer periphery of the collar 56. Finally, the third metal block body 42 is screwed into the other end of the coupling bolt 44, so that the other members are fastened and fixed by the first and third metal block bodies 38 and 42.

The piezoelectric elements 22 and 24 are arranged so as to have different polarization directions as shown in FIG. 3. When high-frequency AC voltages of the same polarity are applied, when one expands, the other contracts. become. However, since the high frequency AC voltage of the opposite polarity is applied by using the electrode plate 26 in common, when one piezoelectric element 22 is extended, the other piezoelectric element 24
When one of the piezoelectric elements 22 contracts, the other piezoelectric element 24 also contracts. Thereby, the stator section 20
The amplitude value of the longitudinal vibration in the longitudinal direction of the coupling bolt 44 as a whole can be increased.

As described above, in the piezoelectric motor of this embodiment, when a high-frequency AC voltage is applied to the piezoelectric elements 22 and 24, longitudinal vibrations in the thickness direction of the piezoelectric elements 22 and 24 occur, and the coupling bolt 44 Torsion vibration caused by the thread groove of the first metal block body 42 and the elliptical vibration which combines the longitudinal vibration and the torsional vibration on the end face of the third metal block body 42 (the same applies to the end face of the first metal block body 38). The rotor section 10 shown in FIG. 1 is driven to rotate in one direction by the elliptical vibration.

Next, the operation of the piezoelectric element 30 used for detecting torsional vibration will be described. FIG. 4 is a diagram showing the principle of detecting torsional vibration using a piezoelectric element polarized in the circumferential direction.

As shown in FIG. 3A, attention is paid to a part Δt of the piezoelectric element 30 polarized in the circumferential direction. This part Δt can be considered as a rectangular shape as shown in FIG. 3B, and its polarization direction can be approximated as being substantially parallel to one side of the rectangular shape. When a high-frequency AC voltage is applied to the two end faces of the piezoelectric element having such a rectangular shape, the two end faces operate to move in opposite directions as shown in FIG. Therefore, when a high-frequency AC voltage is applied to the two end faces of the piezoelectric element 30 having a circular shape, the piezoelectric element 30 operates so that the two end faces move in opposite directions toward the circumferential direction.

The detection of the torsional vibration of the piezoelectric element 30 is based on the idea that it can be performed by using the opposite effect of such a principle.

FIG. 5 is a diagram for explaining the optimal position of the piezoelectric element mounted for detecting torsional vibration. FIG. 2A shows a state of longitudinal vibration appearing on the stator section 20, and FIG. 2B shows a state of torsional vibration appearing on the stator section 20.

In the piezoelectric motor of this embodiment having such a vibration state, by arranging the piezoelectric element 30 at the position of the node of the torsional vibration as shown in FIG. Conceivable. That is, by disposing the piezoelectric element 30 at this position, a phenomenon occurs in which the two end faces of the piezoelectric element 30 move in opposite directions as shown in FIG. 4C, and the voltage amplitude generated between the two end faces is reduced. Will be the largest. However, not only when the two end faces of the piezoelectric element 30 move in opposite directions but also when the moving directions are the same but the amounts are different, a voltage is generated between the two end faces. At positions other than antinode 1 and antinode 2 shown in (B), torsional vibration can be detected.

FIG. 6 is a diagram showing an example of a polarization method when the piezoelectric element 30 is polarized in the circumferential direction. As shown in the figure, in the piezoelectric element 30 of the present embodiment, the plane portion is divided into a plurality of regions (for example, 8 divisions) along the circumferential direction.
Silver deposition is applied to each of the divided regions. As shown in “Polarization 1” to “Polarization 8” in the same drawing, two adjacent divided regions are extracted, and a DC voltage is applied between these two divided regions, whereby a part of the polarization in the circumferential direction is changed. carry out.
By performing this part of the polarization in a loop until it is completed for all the divided regions, and finally polishing the silver deposition surface,
The piezoelectric element 30 is completed by removing the silver deposition.

In the polarization method shown in FIG. 6, a case where the plane portion of the piezoelectric element 30 is divided into eight parts has been described as an example, but other divisions may be used. Although the polarization is performed for each of two adjacent divided regions, a pair may be formed for each of two adjacent divided regions, and a plurality of sets may be simultaneously polarized.

Next, the results of actually detecting the torsional vibration using the piezoelectric element 30 will be described.

FIG. 7 is a diagram showing the result of measuring the strength of the detection signal while changing the mounting position of the piezoelectric element 30. The frequency of the motor drive voltage applied between the electrode plates 26 and 28 and the electrode plates 32 and 34 are shown. The relation with the strength (output amplitude) of the detection signal appearing in between is shown. Each of a to c in FIG. 5 corresponds to each of a to c in FIG. That is, a is a detection result when the piezoelectric element 30 is arranged at the position of the node 2 of the torsional vibration shown in FIG. 5B, and b is a position where the piezoelectric element 30 is slightly shifted from the node 1 of the torsional vibration. This is a detection result in the case of arrangement. C is a detection result in which the piezoelectric element 30 is arranged at the position of the antinode 1 of the torsional vibration.

As shown in FIG. 7, when the piezoelectric element 30 is arranged at the position of the node of the torsional vibration, the detected intensity is the largest, and it becomes smaller as the position is shifted from the position of the node. Therefore, when the piezoelectric element 30 is arranged at the position of the node, an efficient detection operation with the best SN ratio is performed.

FIG. 8 is a diagram showing the result of measuring the phase of the torsional vibration by changing the position of the piezoelectric element 30. FIG. 8 shows how the phase difference between the motor drive voltage and the torsional vibration changes the drive frequency. Is shown. Each of a to c in FIG. 14 corresponds to each of a to c in FIG. 7 and FIG.

As shown in FIG. 8, in a and b in which the piezoelectric elements 30 are arranged at positions other than the antinode of the torsional vibration, phase difference curves having almost the same tendency are obtained. However, since the directions of the torsional vibration are opposite in the vicinity of the nodes 2 and 1 in FIG.
The phase difference curve shown in FIG. 8A and the phase difference curve shown in FIG. 8B appear 180 degrees out of phase.

On the other hand, the phase difference curve of c in which the piezoelectric element 30 is placed at the antinode of vibration does not show a certain tendency and becomes unstable.

Assuming that the optimum driving frequency of the piezoelectric motor having such a phase difference characteristic is f 1, when the piezoelectric element 30 is mounted on the node of FIG. By controlling the frequency of the drive voltage so that the phase difference with the vibration is about -70 degrees, the motor can always be driven with the maximum efficiency. Similarly, when the piezoelectric element 30 is mounted near the node 1 in FIG. 5B (case b)
Has a phase difference between the motor drive voltage and the torsional vibration of about 110.
By controlling the motor drive voltage so that the motor drive voltage is high, the motor can be driven with maximum efficiency.

However, when the piezoelectric element 30 is mounted at the position of the antinode 1 in FIG. 5B (case (c)), the phase difference between the motor drive voltage and the torsional vibration is set to about -80 degrees. Also,
Since the corresponding drive frequency is not determined, the motor cannot be driven based on this detection signal.

FIG. 9 is a diagram showing in detail a phase difference curve when a piezoelectric element is mounted at a position other than the antinode of torsional vibration.
As an example, the phase difference between the motor drive voltage and the torsional vibration is about 9
A case of a piezoelectric motor having an optimum driving frequency f1 at 0 ° is shown. Since the phase difference changes abruptly near the optimum drive frequency f1, when the control is performed so that the phase difference is constant, the change in the drive frequency is small and stable control can be performed.

As described above, the piezoelectric motor of this embodiment generates the elliptical vibration on the rotor contact surface 12 using the torsional vibration, and changes the phase of the torsional vibration to a position other than the antinode of the torsional vibration (preferably, Piezoelectric element 3 attached to the position near the node)
0 is detected. In particular, this piezoelectric element 30
Since it is polarized in the circumferential direction, it is possible to efficiently detect the vibration state in the torsional direction, and since it can be mounted by being sandwiched between the second and third metal block bodies 40 and 42, Thereby, the parts are not broken or detached due to partial stress, and the assembling property and the durability can be improved.

The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the invention.

For example, in the above-described embodiment, the second
Since the circumferentially polarized piezoelectric element 30 is arranged between the metal block body 40 and the third metal block body 42, at least three metal block bodies 38, 40, and 42 are required. A piezoelectric element or the like for detecting torsional vibration may be arranged between the first metal block body 38 and the piezoelectric element 22 or the like used for generating vibration. That is, FIG.
Since the piezoelectric elements 22 and 24 used to generate longitudinal vibration are arranged so as to be substantially at the nodes of longitudinal vibration and torsional vibration as shown in FIG.
Even when the torsional vibration detecting piezoelectric element 30 or the like is arranged adjacent to the torsional vibrations 2, 24, etc., it is always near the position of the node of the torsional vibration. Therefore, although the strength of the detection signal is slightly reduced as compared with the case where the piezoelectric element 30 is arranged completely corresponding to the position of the node of the torsional vibration, a good phase difference curve as shown in FIG. As a result, the motor can be driven at the optimum drive frequency. In addition, when the piezoelectric element 30 is arranged as described above, the second metal block 40
Since it is not necessary to divide the third metal block body 42 and the third metal block body 42, both of them can be formed integrally, and the assemblability can be further improved.

In the above-described embodiment, the elliptical vibration is generated on the rotor contact surface 12 by using the longitudinal vibration generated by the piezoelectric element and the torsional vibration caused by the screw groove of the bolt. Is not limited to this.

In FIG. 10, a plurality of oblique slit grooves 58 are formed on one end surface (the side opposite to the rotor contact surface 12) of the third metal block 42 so that the ends thereof coincide with each other. Therefore, after assembling the stator section 20, the second metal block body 40 and the third metal block body 42 are integrated with the piezoelectric element 30 or the like interposed therebetween, and a plurality of oblique slit grooves 58 are provided near the center thereof. Is formed.

FIG. 11 is a diagram showing details of the oblique slit groove 58 formed in the third metal block body 40. FIG. 5A is a view of the third metal block body 42 as viewed from the side, in which a plurality of oblique slit grooves 58 are partially in contact with the lower end face of the third metal block body 42. Is shown. These oblique slit grooves 58 can be formed by cutting from the lower side or the lateral direction of the third metal block body 42, so that the formation can be performed relatively easily.

FIG. 7B is a view of the third metal block 42 as viewed from below, and shows a state in which twelve oblique slit grooves 58 are formed as an example.

By arranging the centers of the plurality of oblique slit grooves 58 so as to substantially coincide with the positions of the nodes of the longitudinal vibration, the oblique slit grooves 58 can expand and contract in different directions with the center as a boundary. Become. In addition, since the inclination direction of the oblique slit groove 58 is different from the vibration direction of the longitudinal vibration, when such expansion and contraction occurs, a phenomenon occurs that the rotation is performed in a direction in which the center portion rotates in a certain angle range around the center. . Thereby, the third metal block body 42
In the diagonal slit groove 58, a torsional vibration is generated, and this vibration is propagated to the other metal block bodies 38, 40, so that the entire stator portion 20 is torsionally vibrated. Therefore, the longitudinal vibration directly generated by the piezoelectric elements 22 and 24 and the torsional vibration generated by the action of the oblique slit groove 58 are combined, and an elliptical vibration in a certain direction is generated on the rotor contact surface 12, and the elliptical vibration is generated. Accordingly, the rotor unit 10 is driven to rotate in one direction.

The phase difference between the longitudinal and torsional vibrations of the piezoelectric motor of FIG. 10 and the motor drive voltage is as shown in FIG. 15A, and the vibration intensity is as shown in FIG. 15B. The phase difference between the longitudinal vibration and the motor drive voltage with respect to the optimum drive frequency f1 is φb, and the phase difference between the torsional vibration and the motor drive voltage is φ
Although there are many frequencies that become φb in the longitudinal vibration, the optimum driving frequency f1 by controlling the phase difference between the longitudinal vibration and the motor driving voltage to be constant φb is obtained.
Is difficult to detect. Further, although the intensity with respect to the optimum driving frequency f1 is gb, the value of gb changes due to a change in load or the like, so that it is difficult to detect the optimum driving frequency f1 even with the vibration intensity.

As described above, it is difficult for the piezoelectric motor shown in FIG. 10 to perform the most efficient motor drive with the technique disclosed in Japanese Patent Laid-Open No. 210786/1990.

However, in the control in which the phase difference of the torsional vibration is kept constant at φa, the optimum drive frequency f1 can be detected. Therefore, the piezoelectric motor of FIG. Driving can be performed. Therefore, even when the torsional vibration is generated in this manner, the piezoelectric element 30 polarized in the circumferential direction near the position of the node of the torsional vibration (or a position other than the antinode) as in the above-described embodiment. By attaching it,
It is possible to efficiently detect torsional vibration, thereby enabling motor control using the phase difference between the motor drive voltage and the torsional vibration.

As another method of generating torsional vibration, for example, a piezoelectric element polarized in the direction of the rotational axis and a piezoelectric element polarized in the circumferential direction are simultaneously vibrated, thereby obtaining longitudinal vibration and circumferential vibration. The torsional vibration combined with the vibration in the direction may be generated.

Further, in this embodiment, the case where the piezoelectric element 30 polarized in the circumferential direction is mounted on a part of the piezoelectric motor has been described. However, for example, the piezoelectric element 30 is incorporated in another device using a torsional vibrator. Alternatively, the torsional vibration generated by the torsional vibrator may be directly detected.

[0065]

As described above, according to the first aspect of the present invention,
By polarizing the second piezoelectric element in the circumferential direction and mounting it at a position other than the antinode of the torsional vibration, the phase of the torsional vibration can be detected efficiently. Moreover, the second piezoelectric element is sandwiched by at least two blocks like the first piezoelectric element used for generating vibration, and is not externally attached to the stator portion, so that the assemblability and durability are improved. Can be improved.

Further, according to the piezoelectric motor of the present invention, the second piezoelectric element is mounted near the position of the node of the torsional vibration, and the torsional vibration between the two plane portions of the second piezoelectric element is provided. Is maximized, the amplitude intensity of the voltage output from the second electrode is also maximized, and the most efficient torsional vibration detection with a good SN ratio can be performed.

According to the piezoelectric motor of the third aspect, the second
It is possible to drive the motor such that the phase difference between the high-frequency AC voltage applied to the first piezoelectric element and the torsional vibration appearing in the stator section has a predetermined value by utilizing the phase of the torsional vibration detected by the piezoelectric element. Yes, it is possible to always apply a high-frequency AC voltage having the optimum driving frequency to the first piezoelectric element, and it is possible to maximize the driving efficiency of the piezoelectric motor.

[Brief description of the drawings]

FIG. 1 is a diagram showing an entire configuration of an embodiment to which a piezoelectric motor of the present invention is applied.

FIG. 2 is a perspective view showing a state where a stator unit is assembled.

FIG. 3 is an exploded perspective view showing a detailed structure and an assembled state of a stator unit.

FIG. 4 is a diagram illustrating the principle of detecting torsional vibration using a piezoelectric element polarized in a circumferential direction.

FIG. 5 is a diagram for explaining an optimal position of a piezoelectric element mounted for detecting torsional vibration.

FIG. 6 is a diagram illustrating an example of a polarization method when a piezoelectric element is polarized in a circumferential direction.

FIG. 7 is a diagram showing the result of measuring the strength of a detection signal while changing the mounting position of a piezoelectric element.

FIG. 8 is a diagram showing the result of measuring the phase of torsional vibration while changing the position of the piezoelectric element.

FIG. 9 is a diagram illustrating a relationship between a phase difference of torsional vibration and a driving frequency.

FIG. 10 is a view showing a structure of a piezoelectric motor in which a plurality of oblique slit grooves are formed on one end surface of a metal block.

FIG. 11 is a diagram showing details of an oblique slit groove formed in a metal block body.

FIG. 12 is a view showing a conventional piezoelectric motor.

FIG. 13 is a diagram showing a relationship between a driving frequency and a phase of torsional vibration when driving the piezoelectric motor shown in FIG.

FIG. 14 is a diagram illustrating a relationship between a phase difference, an amplitude intensity, and a driving frequency with respect to longitudinal vibration of the piezoelectric motor illustrated in FIG.

FIG. 15 is a diagram illustrating a relationship between a phase difference, amplitude intensity, and driving frequency of the piezoelectric motor illustrated in FIG. 10 with respect to longitudinal vibration and torsional vibration.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Rotor part 20 Stator part 22, 24, 30 Piezoelectric element 26, 28, 32, 34 Electrode plate 36 Insulating plate 38 1st metal block body 40 2nd metal block body 42 3rd metal block body 44 Coupling bolt

──────────────────────────────────────────────────の Continued on the front page (72) Inventor Keisuke Honda 20 Oyama-cho, Oiwa-cho, Toyohashi-city, Aichi Prefecture Inside Honda Electronics Co., Ltd. (56) References JP-A-5-111267 (JP, A) JP-A-5-64468 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02N 2/00

Claims (3)

(57) [Claims] 1. A piezoelectric motor having a stator portion and a rotor portion, wherein the stator portion rotates by utilizing torsional vibration generated in the stator portion, wherein the stator portion directly or indirectly causes the torsional vibration. A first piezoelectric element used to generate a piezoelectric element; a first electrode for applying a high-frequency AC voltage to the piezoelectric element; and a first electrode that is polarized in a circumferential direction of the rotor section, and A second piezoelectric element that detects the torsional vibration by being installed at a position other than the antinode, a second electrode that detects a voltage generated at an end face of the second piezoelectric element, the first and second piezoelectric elements, And at least two blocks attached and fixed to both sides of the piezoelectric element and the first and second electrodes so as to sandwich the piezoelectric element and the first and second electrodes. The piezoelectric motor, characterized in that the torsional vibration detected by said second piezoelectric element. 2. The piezoelectric motor according to claim 1, wherein the second piezoelectric element is mounted near a position of the node of the torsional vibration. 3. The method according to claim 1, wherein a phase difference between a high-frequency AC voltage applied to the first electrode and a detection voltage from the second electrode is controlled to a predetermined value. And a piezoelectric motor.