JP2880837B2 - Planar drive type piezoelectric 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 planar drive type piezoelectric motor which obtains a planar displacement by using expansion and contraction of a piezoelectric element as a drive source.

[0002]

2. Description of the Related Art In a conventional motor, a plurality of iron pieces are arranged at a constant pitch on the outer periphery of a rotor, and a plurality of magnetic poles are arranged on the inner circumference of a stator by sequentially shifting the iron pieces of the rotor by a predetermined angle. There is a stepping motor that sequentially excites each magnetic pole and attracts an iron piece to rotate the rotor by a certain angle.

However, in a stepping motor that rotates the rotor by attracting the iron piece of the rotor by such a magnetic force, the stepping motor is surely positioned at a position where the magnetic pole and the iron piece are aligned against the inertial force generated when the rotor is rotated. It was difficult to stop. Therefore, a piezoelectric motor proposed in Japanese Patent Application Laid-Open No. 61-22775 has been proposed as a motor that improves this point. As shown in FIG. 10, this piezoelectric motor has a rotor 20
A plurality of engaging teeth 21 having a cross-sectional shape of an isosceles triangle are formed at a constant pitch radially about the rotation axis of the rotor 20, and a plurality of levers 22 are arranged to face one surface of the rotor 20. The lever 22 is arranged radially with respect to the rotation axis of the rotor 20, and is capable of moving forward and backward in the axial direction of the rotor 20 (in FIG. 10, a direction perpendicular to the paper surface). Then, in a portion of the lever 22 facing the engagement tooth 21,
A plurality of feed dogs 23 which can mesh with the engagement teeth 21 and have the same pitch as the engagement teeth 21 are formed.

Here, the positional relationship between the feed teeth 23 of the respective levers 22 and the engagement teeth 21 will be described with respect to the case where the number of the levers 22 is five. If the teeth are aligned and engaged, the feed dog 23 at the position B is shifted by 1/5 pitch from the engagement tooth 21, 2/5 pitch at the position C, 3/5 pitch at the position d, and 4/5 at position E. It is formed so as to shift the pitch.

On the surface of the lever 22 opposite to the surface facing the rotor 20, a retractable actuator (not shown) is arranged perpendicular to the surface on which the engaging teeth 21 of the rotor 20 are formed. . In this actuator, a large number of piezoelectric ceramics are laminated, and when a voltage is applied to each piezoelectric ceramic, the actuator extends in the laminating direction due to the total distortion of the piezoelectric ceramics, and the lever 22 is moved to the engagement teeth
When the voltage is stopped when the voltage is stopped, the actuator contracts and the lever 22 moves back from the surface on which the engaging teeth 21 of the rotor 20 are formed.

In this piezoelectric motor, when rotation starts from a state in which the feed dog 23 of the lever 22 at the position A shown in FIG. 10 is engaged with the engagement tooth 21, the actuator corresponding to the lever 22 at the position B is extended. The lever 22 in the position a.
The actuator corresponding to is contracted. At this time, the feed dog 23 of the lever 22 at the position B is
1 is located on the inclined surface in the clockwise direction, the forward movement of the lever 22 causes the feed dog 23 to push the inclined surface of the engaging tooth 21, thereby rotating the rotor 20 clockwise and engaging with the feed dog 23. The rotor 20 is rotated until the teeth 21 are completely engaged. At this time, the rotor 20 rotates by 1/5 pitch.

In the same manner, the actuator corresponding to the lever 22 at the position C is extended, and the lever 22 at the position
Is contracted, the rotor 20 rotates by １ ／ pitch at a time. Here, if the expansion and contraction of the actuator corresponding to the positions A to E are repeated in a constant cycle, the rotor 20 can be rotated at a constant speed.

In this piezoelectric motor, since the rotor is rotated by mechanical engagement, the rotation stop position can be made accurate.

[0009]

However, when linear positioning is performed using the above-described piezoelectric motor, since the piezoelectric motor performs a circular operation, it is necessary to convert the circular operation into a linear operation. There is a problem that a decrease in accuracy due to this conversion cannot be avoided. Furthermore, in applications where planar positioning that further develops linear positioning is required, there has been a problem that the precision in converting a circular motion into a linear motion is reduced, thereby further lowering the positioning accuracy. .

The present invention has been made in view of the above points, and an object of the present invention is to provide a planar drive type piezoelectric motor which can accurately perform planar positioning.

[0011]

According to the present invention, in order to achieve the above object, a flat stator and a mover movably disposed on the stator are provided. In addition, a plurality of teeth are arranged in two directions, and each tooth is formed into a pointed shape having inclined surfaces on both sides in the two directions. The movable element is provided with a plurality of pressing members including a telescopic actuator which is driven by a piezoelectric element that moves forward and backward so as to engage and disengage the joint portion with the tooth.

In order to facilitate the formation of the teeth, the teeth may be formed in a conical shape. Further, for example, when it is desired to make the positioning accuracy different in two directions, the inclination angles of the inclined surfaces of the teeth may be made different in two directions. Further, as an example of a specific method of forming the teeth and the pressing body for accurately performing the planar positioning, a plurality of teeth are arranged in a row at a constant pitch in two directions orthogonal to the stator. When a plurality of pressing bodies are provided on the mover at a constant pitch in each of the two directions, and one direction is defined as the X direction and the other direction is defined as the Y direction, the pressing body pitch Px in the X direction and the Y direction are defined. Px = nx · px + px / mx Py = ny · py + py / my where mx is the number of pressed bodies in the X direction, my is the number of pressed bodies in the Y direction, and px is the pitch of the teeth in the X direction. May be a positive integer including the pitch nx, ny: 0 in the Y direction.

[0013]

The present invention has the above-described structure,
The mover can be moved linearly, which eliminates the need to convert circular motion to linear motion as in the past, enabling high-precision positioning, and allowing the mover to move linearly in two directions. By doing
The mover can be operated in an arbitrary direction in a plane, that is, the mover can be operated in a plane, so that planar positioning can be accurately performed. Things.

[0014]

(Embodiment 1) FIGS. 1 to 5 show an embodiment of the present invention. In the planar drive type piezoelectric motor of this embodiment, FIG.
As shown in FIG. 1, the stator 1 includes a planar stator 1 and a mover 3 movably disposed on the stator 1. here,
As a method of movably providing the mover 3 on the stator 1, for example, the mover 3 may be magnetically attracted (or repelled) to the stator 1 and held. However, if the mover 3 is movable on the stator 1, another method may be used. On the surface of the stator 1 facing the mover 3, a plurality of teeth 2 are arranged at a constant pitch in two orthogonal directions (X and Y directions in FIG. 1). Further, the movable element 3 includes a plurality of actuators 6 each of which includes a piezoelectric element which generates a distortion due to application of a voltage as a driving source.
And pressing members 4 and 5, each of which is attached to the tip of these actuators 6 and includes a plurality of engaging portions 7 and 8 which can be disengaged from the teeth 2.

As shown in FIG. 8A, the teeth 2 of the stator 1 are formed in a regular quadrangular pyramid having inclined surfaces on both sides in the X and Y directions. In the present embodiment, the mover 3 is arranged as shown in FIG.
As shown in (b), a plurality of pressing members 5 each comprising an actuator 6 and an engaging portion 8 are provided along both end edges in the X direction of the flat rectangular parallelepiped base, and the pressing members 5 along both side edges in the Y direction are provided. While the pressing members 5 are lined up, the actuator 6
And a plurality of pressing members 4 each comprising an engaging portion 7. Here, each of the engaging portions 7 and 8 has a shape in which a triangular prism is turned sideways, and the engaging portions 7 have inclined surfaces on both sides of the stator 1.
Is formed as a direction along the slope of the teeth 2 in the X direction,
The engaging portion 8 is formed so that the inclined surfaces on both sides are along the inclined surfaces of the teeth 2 of the stator 1 in the Y direction. Therefore, in the following description, the engaging portions 7 and 8 will be referred to as the X engaging portion 7 and the Y engaging portion 8.
Will be identified and called.

The pitch between the X engaging portions 7 adjacent to each other is set to Px as shown in FIG.
Px = nx × px + px / mx where mx is a positive integer including the number of pressing bodies 4 in the X direction, nx: 0, and the pitch of the Y engaging portions 8 adjacent to each other. Is Py, as shown in FIG. 3B, and the pitch in the Y direction of the teeth 2 adjacent to each other is py, where Py = ny · py + py / my, where: my: the number of pressing bodies 5 in the Y direction ny: It is a positive integer including 0. In order to simplify the following description, as shown in FIGS. 2 and 3, mx = my = 3 and nx = my = 3
The case where ny = 2 will be described.

The operation of the planar drive type piezoelectric motor will be described with reference to FIG. First, the driving operation of the flat drive type piezoelectric motor in the X direction will be described. Here, for convenience of explanation, the X engaging portions 7 will be described as 7a, 7b, 7c in order from the left side in FIG. 1, and the corresponding actuators 6 will be described as 6a, 6b, 6c.
Now, when a voltage is applied to the actuator 6a, the actuator 6a expands, and as shown in FIG. 4A, the tip of the X engaging portion 7a is located between the two teeth 2 of the stator 1 facing each other. It is assumed that each is engaged.

In this state, when the actuator 6b is extended and the voltage applied from the actuator 6a is released and contracted, the X engaging portion 7b engages with the inclined surface of the tooth 2, and the actuator The force in the traveling direction indicated by the arrow in FIG. 4 is applied to the mover 3 by the pressing force received from 6b, and the mover 3 moves. Then, the X engaging portion 7b moves to a position where it is completely engaged between the teeth 2 as shown in FIG. Here, since the pitch Px of the X engaging portion 7 is 2px + px / 3 as described above, the mover 3
Move by x / 3.

Next, the actuator 6c is extended and the actuator 6b is contracted. At this time, the mover 3 further moves in the advancing direction by the pressing force received from the actuator 6c, and as shown in FIG.
Move to a position where c fully engages between teeth 2. Hereinafter, if the actuators 6a, 6b, and 6c are sequentially extended and contracted cyclically by extending the actuator 6a and contracting the actuator 6c, FIG.
It advances by a predetermined pitch in the direction of the middle arrow.

When the actuators 6a, 6b, 6c are cyclically expanded and contracted in the reverse order to the above-described case, the actuators 6a, 6b, 6c can move in a direction opposite to the direction indicated by the arrow in FIG. In the above description, the driving operation in the X direction was performed.
/ 3 can be moved. That is, the planar drive type piezoelectric motor of this embodiment can be a motor that moves in steps of px / 3 in the X direction and py / 3 in the Y direction.

In the above description, the driving in the X direction and the driving in the Y direction are performed independently. However, FIGS. 5A and 5B show (a) to (b). (C)
When the driving in the X direction and the driving in the Y direction are performed at the same time as shown in (1), it is possible to move in a direction having an angle with respect to the X and Y directions. For example, the pitch p in the X and Y directions
When x and py are equal, 45 ° with respect to the X and Y directions
Mover 3 can be moved in the direction of. further,
By changing the pitch and the driving speed in the X and Y directions, the moving direction of the mover 3 can be changed.

(Embodiment 2) FIGS. 6 and 7 show still another embodiment of the present invention. This embodiment shows a driving method of a planar drive type piezoelectric motor for further improving the positioning accuracy. The driving method of the present embodiment will be described for the case where the mover 3 is driven in the X direction. FIG. 6A shows a state in which the X engaging portion 7c is engaged between the teeth 2, and FIG. 6C is driven by one step from the state of FIG. It shows a state in which it is engaged between the teeth 2. In this one step period, when the actuator 6c is contracted and the actuator 6a is extended at the same time, the X engaging portion 7
a, 7c simultaneously engages the inclined surface of the tooth 2 in FIG.
The state shown in FIG.

Therefore, as shown in FIGS. 7B to 7D, if the three actuators 6 are gradually expanded and contracted and the expansion and contraction state is stopped halfway, one step (FIG. 6B) is performed. px / 3), the mover 3 can be positioned at a position between (px / 3). That is, the positioning can be performed in one step or less. This can be similarly performed in the Y direction.

(Embodiment 3) By the way, it is also possible to combine the driving method of the above-mentioned planar drive type piezoelectric motor with the above-mentioned Embodiment 1 and Embodiment 2. Specifically, a desired distance is moved in a plurality of steps (1 step is p / 3) by the driving method described in the first embodiment (this is referred to as coarse movement), and after the movement, the plurality of movements described in the second embodiment are performed. The engaging portions 7 and 8 are engaged simultaneously with the teeth 2 to perform positioning (this is called fine movement). In this case, the mover 3 can be moved at a high speed by the coarse movement, and the positioning can be performed with high accuracy by the fine movement. Here, to reduce the positioning time
Is, X, step number Ux in the Y direction of each of the coarse, Uy, it is preferable to satisfy the following equation.

Lx−px / 3 <Ux · px / 3 ≦ Lx Ly−py / 3 <Uy · py / 3 ≦ Ly, where Lx: distance to a predetermined position in the X direction Ly: predetermined position in the Y direction (Embodiment 4) In each of the above embodiments, the teeth 2 of the stator 1 are shown in FIG.
Although the case of a quadrangular pyramid shown in FIG. 1 has been described, a conical shape shown in FIG. In this case, tooth 2
In addition, there is no need to form inclined surfaces in the X and Y directions, that is, inclined surfaces orthogonal to each other, and there is an advantage that machining of the teeth 2 is facilitated.

(Embodiment 5) FIG. 9 shows still another embodiment of the present invention.
The apex angles of the respective surfaces in the X and Y directions are made different as shown by θx and θy. In this way, the moving distance of the mover 3 in one step can be made different.

[0027]

As described above, the present invention comprises a planar stator and a mover movably disposed on the stator, and a plurality of teeth are formed in two directions perpendicular to the stator. The teeth are arranged in a row and each tooth is formed into a pointed shape having inclined surfaces on both sides in the two directions. An engaging portion that can be disengaged from the tooth and the engaging portion is disengaged from the tooth. Since a plurality of pressing bodies composed of a telescopic actuator that is driven by a piezoelectric element that moves forward and backward so as to cause the movable element to be provided,
Since the mover can be operated linearly, there is no need to convert a circular operation into a linear operation as in the prior art, high-precision positioning can be performed, and the mover can be operated linearly in two directions. The movable element can be operated in an arbitrary direction within the above, that is, the movable element can be operated in a plane, so that planar positioning can be accurately performed.

When the teeth are formed in a conical shape, the accuracy of the inclined surface is not required as in the case of a pyramid, and the teeth can be easily formed. Further, if the angles of the inclined surfaces on both sides of the tooth are different in two directions, for example, the positioning accuracy can be different in the two directions.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of an embodiment of the present invention.

FIGS. 2A to 2D are a perspective view, a plan view, a front view, and a side view of a mover.

FIGS. 3A and 3B are explanatory views showing the formation state of teeth and pressing bodies in the X and Y directions, respectively.

FIG. 4 is an operation explanatory diagram when the mover is moved in one direction.

FIG. 5 is an operation explanatory diagram when a mover is simultaneously moved in X and Y directions.

FIG. 6 is an operation explanatory view of still another embodiment.

FIG. 7 is an explanatory diagram of a driving method of the actuator in the above.

FIGS. 8A and 8B are perspective views showing teeth of different shapes.

FIGS. 9A to 9C are a plan view, a side view, and a front view showing still another method of forming teeth.

FIG. 10 is an explanatory view of the structure and operation of a conventional piezoelectric motor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Stator 2 Teeth 3 Mover 4,5 Pressing body 6 Actuator 7,8 Engaging part

Claims (4)

(57) [Claims] 1. A stator comprising: a planar stator; and a mover movably disposed on the stator. A plurality of teeth are arranged in two directions orthogonal to the stator, and each tooth is arranged. Are formed in a pointed shape having inclined surfaces on both sides in the two directions, and an engaging portion that can be engaged and disengaged with the tooth, and a piezoelectric element that advances and retreats so as to engage and disengage the engaging portion with the tooth. A planar drive type piezoelectric motor, wherein a plurality of pressing bodies each including an extendable actuator serving as a driving source are provided on the movable element. 2. A planar drive type piezoelectric motor according to claim 1, wherein said teeth are formed in a conical shape. 3. A planar drive type piezoelectric motor, wherein said inclined surfaces of said teeth have different inclination angles in two directions. 4. A plurality of teeth are arranged in a row at a constant pitch in two directions orthogonal to the stator, and a plurality of pressing bodies are provided on the mover at a constant pitch in the two directions, respectively. Direction and the other direction is the Y direction,
The pitch Px of the pressing body in the X direction and the pitch Py of the pressing body in the Y direction are as follows: Px = nx · px + px / mx Py = ny · py + py / my where mx: number of pressing bodies in the X direction my: pressing in the Y direction 2. The planar drive type piezoelectric motor according to claim 1, wherein the body number px: the pitch of the teeth in the X direction py: the pitch of the teeth in the Y direction nx, ny: a positive integer including 0. 3.