JPH06105532A - Direct-acting type actuator for applicating wobble motor - Google Patents

Abstract

PURPOSE:To make it possible to convert a rotary motion into a linear motion by clearing problems such as a reduction ratio and miniaturization while the utilizing merits of a wobble motor and changing slight torque of the motor into large force. CONSTITUTION:An actuator comprises a wobble motor for harmonically driving a rotor 3 by combining a cylindrical stator 1 with the rotor 3 loosely fitted into the stator 1, a female screw 6 formed on the inner circumference surface of a shaft hole 5 bored in the shaft center to the rotor of the wobble motor, a male screw 9 which has a shaft with a diameter shorter than the shaft hole 5 and engages with the female screw 8 on the outer circumference surface, and an actuator output rod 7 which is fitted into the rotor shaft hole 5 of the wobble motor and is slidably pivoted in an axial direction through a slide bearing 8 in a concentric position with the stator 1. The stroke operation of the actuator output rod 7 is straight performed by the rotation of the wobble motor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microminiature direct acting actuator applied to the field of micromachines.

[0002]

2. Description of the Related Art Recently, research and development relating to micromachines have progressed, and electrostatic micromotors having a diameter of 100 .mu.m or less have been manufactured by utilizing micromachining technology for manufacturing semiconductor devices. By the way, such an electrostatic micromotor has a very small moment of inertia and a theoretical rotation speed of several tens to several million rpm, which is very high, but its generated torque is very small, of several nN to several tens nN. For this reason, when the micromotor is used as an actuator, it is greatly affected by friction loss of the bearing and cannot be put to practical use as an actuator as it is.

On the other hand, a wobble motor is used as a micromotor which has a large reduction ratio and which amplifies the output torque while maintaining the feature of miniaturization as a micromotor. Is known for. The operating principle of this wobble motor (electrostatic drive type) is the same as that of a rolling motor, and its construction is such that the inside diameter of the stator is smaller than the inside diameter of the stator in the cylindrical stator with the drive electrodes divided on the inner peripheral surface. The rotor is loosely fitted, and by sequentially switching and applying the voltage to the drive electrode, the electrostatic attraction force acting between the drive electrode and the rotor causes the rotor to move to the inner peripheral surface of the stator. It is driven harmonically so that it rotates (revolves) while rolling (revolving) along it.

In the wobble motor, the inner diameter of the stator is set to D
_1,The outer diameter of the rotor is D_2,Voltage mark on the stator drive electrode
The number of rotations of the electric field due to the addition is N₁Then, the rotation speed of the rotor
(Rotation) N₂Is given by the following equation. N₂= (D₁/ D₂-1) N₁= K₁N₁ ──── (1) In the above formula (1), for example, D₁/ D₂= 1.033
If K₁= 0.033, K₁Reduction ratio which is the reciprocal ratio of
= 30 is obtained. In addition, this reduction ratio allows
Data output T₂Is due to the electrostatic force between the stator and rotor.
Generated torque is T ₁As T₂= T₁/ K₁ ─────────────── (2) That is, the output of the wobble motor (rotating the motor shaft
Force) is 1 / K₁It turns out that it is amplified twice.

[0005]

By the way, actuators applied to the field of micromachines require linear motion type actuators in addition to rotary actuators such as the micromotors. Therefore, micro-actuators that reciprocate by applying electrostatic attraction and repulsive force are known, but it is difficult to obtain sufficient driving force and moving stroke with these compact actuators. . Therefore, by combining a rotation / linear motion conversion mechanism with a micromotor, a direct drive type (linear motion type)
It is conceivable that the actuator is constructed, but adding such a motion conversion mechanism to the micromotor as an external component makes the actuator larger. Moreover,
Considering the mechanical friction loss generated in the power transmission path in the motion conversion mechanism, it is necessary to further increase the reduction ratio of the motor in order to secure a large output as an actuator. Even if a reduction gear mechanism is additionally installed, it is difficult to secure a sufficient reduction ratio because the number of teeth of the gear cannot be increased with the microminiaturized reduction gear mechanism.

The present invention has been made in view of the above points, and its purpose is to make use of the features of the wobble motor described above, and to clear the problems of reduction ratio and miniaturization to make a small torque of the motor a large force. Another object of the present invention is to provide a direct acting actuator for a wobble motor, which is capable of converting rotary motion into linear motion instead of.

[0007]

In order to achieve the above object, an actuator of the present invention comprises a cylindrical stator, and a wobble motor for harmonically driving the rotor in combination with a rotor loosely fitted in the stator. , A female screw formed on the inner peripheral surface of a shaft hole bored in the rotor center of the wobble motor, and a female screw which meshes with the female screw on the outer peripheral surface of the shaft having a smaller diameter than the shaft hole. And an actuator output rod which is inserted into the rotor shaft hole of the wobble motor and axially slidably supported at the concentric position with the stator.

In the wobble motor of the actuator having the above-mentioned structure, the drive electrodes divided in the circumferential direction are formed on the inner peripheral surface of the stator, and the dielectric layer is formed on the outer peripheral surface of the rotor. The electromagnetic motor can be configured by forming a thin film coil divided in the circumferential direction on the inner peripheral surface and forming a plurality of thin film permanent magnets on the outer peripheral surface of the rotor.

[0009]

In the above structure, when the wobble motor is rotationally driven, the meshing point between the female screw formed in the shaft hole of the rotor and the male screw of the actuator output rod fitted in the shaft hole moves with the rotation of the rotor. The actuator output rod, which is axially slidably supported (restrains the rotation direction), makes a linear motion in a direction corresponding to the rotation of the rotor to perform a stroke operation on the same principle as the feed screw mechanism. Moreover, in the screw type power transmission unit that connects the rotor of the wobble motor and the actuator output rod, a large reduction ratio due to the wobble motion similar to that of the wobble motor itself is obtained, so that the minute rotating torque of the wobble motor is amplified to a large force. Will be taken out from the actuator output rod.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. Embodiment 1 FIGS. 1 to 3 show a direct-acting actuator that employs an electrostatic wobble motor. In FIG. 1, 1 is a cylindrical stator of the wobble motor, and 2 is a division along the inner peripheral surface of the stator 1. Formed thin film drive electrodes, 3
Is a rotor of a wobble motor loosely fitted in the stator 1, 4
Is a dielectric layer formed on the outer peripheral surface of the rotor 3, 5 is a shaft hole drilled in the center of the rotor 3, 6 is a male screw formed on the inner peripheral surface of the shaft hole 5, and 7 is fitted in the shaft hole 5, The actuator output rod 9 is axially slidably supported by the slide bearing 8 at the concentric position with the stator 1, and 9 is a male screw formed on the peripheral surface of the actuator output rod 9 so as to mesh with the female screw 6. Each component constitutes a linear actuator that converts the rotary motion of the wobble motor into a linear motion and drives the actuator output shaft in the direction of the arrow. Although not shown, the rotor 3 of the wobble motor is axially supported via a thrust bearing.

The outer diameter of the rotor 3 of the wobble motor is smaller than the inner diameter of the stator 1, and the shaft hole 5 of the rotor 3 is larger than the shaft diameter of the actuator output rod 7. The actuator output rod 7 is rotatably supported by the bearing 8 so as to be slidable only in the axial direction (arrow) by providing a rotation stop key 7a on the shaft to restrain the rotation.

FIG. 2 shows a drive control circuit for the wobble motor, and for each drive electrode 2 arranged on the inner peripheral surface of the stator 1 of the wobble motor, the switching circuit 1 is provided as shown in the figure.
0, the oscillator 11, and the DC power supply 12 are connected to form a drive control circuit. The rotating operation of the wobble motor is already well known and will not be described here. next,
The operation of the direct acting actuator having the above structure will be described with reference to FIG. That is, when a voltage is applied in order (clockwise direction) from the drive control circuit shown in FIG. 2 to each drive electrode 2 of the stator, the electrostatic attraction force (force in the normal direction) that acts between the stator and the rotor. ) Sequentially moves in the circumferential direction, whereby the rotor 3 rolls (revolves) in the direction of arrow P along the arrangement of the drive electrodes 2 as shown in FIGS.
The rotor itself will rotate in the direction of arrow Q. Further, with the rotational movement of the rotor 3 described above, at the same time, the meshing points between the female screw 6 formed in the shaft hole 5 of the rotor 3 and the male screw 9 of the actuator output rod 7 fitted in the shaft hole are (a) to ( c) Transitions are made in order as indicated by A, B, and C in the figure, whereby the rotational movement is converted into a linear movement by the principle of screw movement, and the actuator output rod 7 performs a stroke operation. The movement stroke amount of the actuator output rod 7 can be increased by increasing the length of the male screw 9. If the order of applying the voltage to the drive electrode 2 is reversed, the rotation direction of the rotor 3 is reversed,
The movement direction of the actuator output rod 7 is also reversed. Therefore, if the order of voltage application to the drive electrode 2 is controlled so as to be alternately switched in accordance with the stroke operation of the rod 7, the actuator reciprocates.

Next, the torque characteristics of the actuator will be described. First, it is generally considered that the screw is a projection of a slope on a cylinder. The torque required to turn the screw is T, the diameter of the screw is d, the screw pitch is p, and the friction coefficient of the screw is μ.
Then, the force Q in the linear movement direction of the screw is given by Q = 2 (πd−μp) / (d (p + μπd)) T = K ₂ T-(3). Accordingly, the rotor 3 and the actuator output rod 7 and a female thread 6, by coupling through a wobble type screw mechanism of the male screw 9, the generated torque T ₁ of the rotor of the wobble motor of wobble motor as in FIG. 1, the (2) From the equation (3), Q = K ₂ / K ₁ T ₁ = K ₃ T ₁ ────────────────── (4) That is, in the configuration of FIG. 1, the wobble motor generated torque T ₁ is amplified by K ₃ times to drive the actuator output rod 7 in the linear movement direction.

Here, as a specific numerical example, the inner diameter D ₁ of the stator 1 in FIG. 1 is 0.8 mm and the outer diameter D _{2 of the} rotor 3 is D _2.
= 0.78 mm, rotor shaft hole 5 inner diameter D ₃ = 1.0 mm, actuator output rod 7 threaded portion outer diameter d = 0.5 mm, female,
Assuming that the thread pitch p of the male screws 6 and 9 is 0.1 mm, and the coefficient of dynamic friction between the rod 7 and the bearing 8 is μ = 0.2 (iron material is coated with carbon), these values are described in the above (1) to (4).
Substituting into the equation, K ₃ ≉580000 is obtained, and it is understood that the minute torque of the wobble motor can be converted into a large force and taken out as an actuator output. Here, when the generated torque of a wobble motor made as a minute micromotor is about 1 × 10 ⁻³ (gf-cm), the output of the actuator output rod 7 is amplified to about 6 gf, and as a result, the actuator applied to the micromachine is manufactured. As a result, a large driving force that can be put to practical use can be obtained.

Second Embodiment FIG. 4 shows a different embodiment of the present invention. In the first embodiment, an electrostatic motor is used as a wobble motor incorporated in an actuator, whereas in this embodiment, It is configured by using an electromagnetic motor. That is, in this embodiment, the 6-pole thin-film coil 1 arranged in the circumferential direction on the inner peripheral surface of the stator 1.
3 is patterned, and a 4-pole thin film magnet (permanent magnet) 14 is patterned on the outer circumference of the rotor 3. Then, the thin-film coil 13 on the stator side is connected to a drive control circuit that is a combination of the switching circuit 10, the oscillator 11 and the power supply 12 as in FIG.

[0016]

As described above, according to the configuration of the present invention, while utilizing the features of the wobble motor, the minute torque is amplified to a large force, and the rotary motion of the motor is converted into the linear motion. The actuator output rod can be stroked. Moreover, the screw mechanism for decelerating the rotational motion and converting it into a linear motion is incorporated into the wobble motor, so that the size and size can be reduced.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an actuator according to an embodiment of the present invention in which an electrostatic motor is used as a wobble motor, (a)
Is a sectional side view, (b) is a sectional view of the bearing portion of the actuator output rod in (a), and (c) is a sectional view of the wobble motor in (a).

FIG. 2 is a drive control circuit diagram of the wobble motor in FIG.

FIG. 3 is an explanatory diagram of the operation of FIG. 1 and includes (a), (b), and (c).
Is a diagram showing the transition of the wobble motor rotation

4A and 4B are configuration diagrams of an embodiment of the present invention in which an electromagnetic motor is used as a wobble motor, in which FIG. 4A is a front view and FIG. 4B is a plan view of the thin-film coil in FIG.

[Explanation of symbols]

 1 Stator of wobble motor 2 Drive electrode 3 Rotor 4 Dielectric layer 5 Shaft hole 6 Female screw 7 Actuator output rod 8 Slide bearing 9 Male screw 13 Thin film coil 14 Thin film magnet

Claims (3)

[Claims] 1. A wobble motor for driving a rotor in a harmonic manner by combining a cylindrical stator and a rotor loosely fitted in the stator, and an inner circumference of a shaft hole formed in the rotor of the wobble motor at its shaft center. A female screw formed on the surface and a female screw that meshes with the female screw on the outer peripheral surface of the shaft having a diameter smaller than that of the shaft hole, and are inserted into the rotor shaft hole of the wobble motor to be axially concentric with the stator. A direct-acting actuator for a wobble motor that is composed of an actuator output rod that is slidably supported on the actuator. 2. The actuator according to claim 1, wherein
A direct-acting actuator for use in a wobble motor, wherein the wobble motor is an electrostatic motor in which drive electrodes divided in the circumferential direction are formed on the inner peripheral surface of the stator and a dielectric layer is formed on the outer peripheral surface of the rotor. 3. The actuator according to claim 1, wherein
The wobble motor is an electromagnetic type motor in which a thin film coil divided in the circumferential direction is formed on the inner peripheral surface of the stator, and thin film permanent magnets with multiple poles are formed on the outer peripheral surface of the rotor. Actuator.