JPH0919131A - Linear drive micromotor - Google Patents

Abstract

PURPOSE: To take out a high driving power in the linear direction with large displacement by threading the outer circumference of rotor and the inner circumference of stator such that they mate each other. CONSTITUTION: Similarly to a wobble motor, the rotor 11 turns by an angle corresponding to the difference between the inner circumference of stator 12 and the outer circumference of rotor 11 upon finishing a cycle of excitation of the stator 12. During that period, the rotor 11 and stator 12 are mated through the external thread 11a and internal thread 12a. Consequently, the rotor 11 is shifted axially by one pitch of thread per single revolution. Since the r.p.m. of rotor 11 is low as compared with the excitation of stator 12 and the rotor is decelerated through the thread, the reduction ratio is increased significantly. Consequently, a high power is applied to the rotor 11 in the axial direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a micromotor used as a drive source for a micromechanism, and in particular, a linear drive micromotor adapted to extract a linear driving force by utilizing the principle of a wobble motor. It is about.

[0002]

2. Description of the Related Art In recent years, a micromechanism has attracted attention, and a micromotor having a large output has been required as a driving source thereof. Several types of such micromotors have been developed, and one of them is a wobble motor.
tor). The wobble motor has a rotor having a diameter slightly smaller than that of a rotor arranged in a cylindrical stator, and the rotor is attracted to the inner peripheral surface of the stator to roll in the circumferential direction.

The principle of rotation of such a wobble motor will be described. As shown in FIG. 1, the rotor 1 has a columnar shape, and a dielectric film 2 is formed on the outer peripheral surface thereof. On the other hand, the stator 3 has a cylindrical shape having an inner diameter slightly larger than the outer diameter of the rotor 1, and a plurality of electrodes 4, 4, ... Are provided on the inner peripheral surface thereof in the circumferential direction. A voltage is applied to the electrodes 4, 4, ... From the driving power source 5 through the switching circuit 6.

In the wobble motor thus constructed, the rotor 1 is set to the ground potential and the electrodes 4, 4,
When a voltage is applied to any of the ..., The rotor 1 is attracted to the inner peripheral surface of the stator 3 at the position of the electrode 4 to which the voltage is applied by the electrostatic attraction force. Therefore, when a voltage is sequentially applied to the electrodes 4, 4, ... In the circumferential direction by the switching circuit 6, the rotor 1 revolves while rolling along the inner peripheral surface of the stator 3 as shown in FIG. do. Looking at one point a on the rotor 1, when the rotor 1 revolves once, the point a moves from the original position by an angle α.
That is, the rotor 1 rotates about the angle α in one revolution. When the outer diameter of the rotor 1 is r and the inner diameter of the stator 3 is R, the angle α is α = (R−r) / r.

In this way, the suction force acting between the rotor 1 and the stator 3 is converted into the rotational force of the rotor 1. Although such a wobble motor has a simple structure, it has a characteristic that a high speed can be obtained at a low speed because it has a built-in reduction mechanism.

When such a wobble motor is used, conventionally, the rotation of the rotor is directly extracted as a rotational force.

[0007]

However, in the case of a wobble motor, the rotor thereof moves eccentrically. Therefore, when trying to transmit the rotation of the rotor to the driven part, it is necessary to interpose a special mechanism such as a constant velocity joint between them. In a microscale environment, the influence of friction becomes significantly large, so it is difficult to efficiently transmit the rotation of the rotor to the driven part through such a mechanism.

On the other hand, in the micromechanism, the driving force in the linear direction is often required rather than the rotational driving force. In such a case, in the conventional wobble motor, a mechanism for converting the rotational movement of the rotor into a linear movement is further required, and its transmission efficiency is significantly reduced. Micro linear actuators that directly generate driving force in the linear direction have also been developed, but in the case of such actuators, the displacement is limited to several tens of μm because the movable part is supported by the suspension. There's a problem.

The present invention has been made in view of the above problems, and an object thereof is to provide a linear driving micromotor capable of extracting a large driving force in a linear direction with a large displacement. .

[0010]

To achieve this object, in the present invention, the rotor and the stator constituting the wobble mechanism are formed with screws that mesh with each other. That is, the linear drive micromotor according to the present invention includes a shaft-shaped rotor, a cylindrical inner peripheral surface having a diameter larger than the outer diameter of the rotor, and a stator arranged on the outer periphery of the rotor, and the rotor. Drive means for adsorbing to the inner peripheral surface of the stator and rolling in the circumferential direction, and screws that mesh with each other are formed on the outer peripheral surface of the rotor and the inner peripheral surface of the stator. On the contrary, the rotor may be cylindrical, and the stator may be cylindrical with a diameter smaller than the inner diameter of the rotor, and screws that mesh with each other may be formed on the inner peripheral surface of the rotor and the outer peripheral surface of the stator.

[0011]

With this structure, when the rotor is rotated in the same manner as the conventional wobble motor, the rotational movement of the rotor is converted by the screw into a linear displacement in the axial direction. Therefore, if the tip of the rotor is brought into sliding contact with the end surface of the driven member via a bearing or the like, the driven member will be driven in the linear direction. In that case, since the rotor and the stator make rolling contact, friction between them is small. Further, in addition to the high torque of the wobble motor, the force is increased by the screw, so that a large driving force can be obtained. Since the screw can be displaced by the length of the screw, the displacement in the axial direction is not restricted.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. 3 to 7 show an embodiment of a linear driving micromotor according to the present invention, FIG. 3 is a plan view thereof, and FIG. 4 is a longitudinal sectional view thereof. 5 and 6
FIG. 7 is an enlarged view of the essential parts thereof, and FIG. 7 is a circuit diagram of a drive circuit which is the drive means thereof.

As is apparent from FIGS. 3 and 4, the linear driving micromotor 10 is composed of a rotor 11 and a stator 12. The rotor 11 is, for example, a thin and long shaft-shaped member having a diameter of about 1 mm and a length of 20 mm, is made of iron, and has an external thread 11a formed on the outer peripheral surface of the upper end portion thereof. Further, the stator 12 includes the coils C1,
Four sets of magnetic poles S1, S2, S3, and S4 formed by attaching tapered iron prisms having a width of about 2.5 mm and a thickness of about 2 mm are radially arranged on the upper and lower ends of C2, C3, and C4, respectively. The magnetic poles of which are ring-shaped copper frames 13
Is fixed integrally. As shown in FIGS. 5 and 6, the tips of the magnetic poles S1, S2, S3 and S4 are formed into arcuate curved surfaces, and when they are assembled, a cylindrical surface is formed. There is. And
A female screw 12a is formed on the inner surface thereof. Rotor 11
The male screw 11a and the female screw 12a of the stator 12 are shaped to engage with each other, but the gap between them is made larger than that of a normal screw. That is, the stator 1
The inner diameter of 2 is slightly larger than the outer diameter of the rotor 11.

The coils C1, C2, C3 of the stator 12
A current is supplied to C4 by the drive circuit 15 shown in FIG. The drive circuit 15
Is a pair of high level signals for the four OR circuits 16 and 1
.. is composed of a shift circuit 17 which is sequentially shifted and supplied to each of the input sections. The shift is performed every time the clock signal is output from the clock circuit 18. When a high level signal is input to any of the OR circuits 16, a current is supplied from the power supply 20 to the corresponding coil via the amplifier 19. Therefore, a current is sequentially supplied to the coils C1, C2, C3, C4, whereby the magnetic poles S1, S2, S3, S4 of the stator 12 are excited. The order of excitation is (S1) → (S1 and S
2) → (S2) → (S2 and S3) → (S3) → ... In this way, the excited state of the stator 12 changes each time a clock signal is input to the drive circuit 15, and completes a cycle when a clock is applied eight times.

Next, the operation of the linear driving micromotor 10 thus constructed will be described. Now, assuming that the magnetic pole S1 of the stator 12 is excited by the drive circuit 15, the iron rotor 11 is attracted to the magnetic pole S1 by the magnetic attraction force. Then, the magnetic poles S1 and S2 are excited to cause the rotor 11 to
It is attracted to an intermediate position between 1 and S2. Then, the excitation of the magnetic pole S1 is stopped and only the magnetic pole S2 is excited, so that the rotor 11 is attracted to the magnetic pole S2. In this way, the rotor 11 moves in the circumferential direction while rolling along the inner peripheral surface of the stator 12. As a result, similarly to the above-mentioned wobble motor, when the excitation of the stator 12 makes one round, the rotor 11 rotates by an angle corresponding to the difference between the inner circumference of the stator 12 and the outer circumference of the rotor 11.

During this time, the rotor 11 and the stator 1
2 are engaged with each other by a male screw 11a and a female screw 12a. Therefore, when the rotor 11 rotates,
The rotor 11 moves in the axial direction. The amount of movement is one screw pitch per one rotation of the rotor 11. That is, as compared with the excitation of the stator 12, the rotation speed of the rotor 11 becomes smaller and the speed is further reduced by the screw, so that the reduction ratio becomes extremely large. As a result, a large axial force is applied to the rotor 11.

Thus, the micromotor 10 can obtain a large axial driving force. In that case, since the rotor 11 and the stator 12 are in contact with each other by rolling, friction between them is small. Therefore, even in a microscale environment, it is unlikely to be affected by friction. Further, by using a wobble motor, the rotor 11 can be made to have a simple shaft shape. Therefore, the screw 11a formed on the rotor 11 can be made sufficiently long. Since the amount of linear displacement of the micromotor 10 is limited only by the length of the screw portion of the rotor 11, it is possible to obtain an extremely large linear displacement by lengthening the screw 11a.

Further, since the rotor 11 and the stator 12 are screw-engaged with each other, the rotor 11 is held at that position even when the excitation of the stator 12 is stopped. Therefore, there is also an advantage that the axial load can be mechanically supported.

Such a linear drive micromotor 1
0 was actually prototyped and tested, and it was confirmed that it was driven well, and the diameter of the rotor 11 was 1 mm and the rotor 1
The gap between the stator 1 and the stator 12 is 40 to 100 μ.
m, the pitch of those screws 11a and 12a is 0.25 mm
, The maximum speed in the axial direction is 5 mm / s, and the maximum generated force is 45
mN was obtained.

8 and 9 are a plan view and a vertical sectional view showing different embodiments of the linear driving micromotor according to the present invention. In the case of this micromotor 20, the rotor 21 has a cylindrical shape, and the stator 22 has a cylindrical shape arranged inside the rotor 21. The stator 22 also has four pairs of magnetic poles S1, S2, as in the above embodiment.
It is composed of S3 and S4, and their magnetic poles are sequentially excited. On the inner peripheral surface of the rotor 21 and the outer peripheral surface of the stator 22, screws 21a that mesh with each other,
22a are formed.

The micromotor 20 constructed in this way
Also in the magnetic poles S1, S2, S3, S of the stator 22
When 4 is sequentially excited in the circumferential direction, the rotor 21 is attracted to those magnetic poles in order and rotates, and is axially displaced by the screw. That is, the suction force acting between the rotor 21 and the stator 22 is converted into the rotational movement of the rotor 21 by the wobble mechanism, and the rotational movement is converted into the linear displacement in the axial direction by the screw. Therefore, it is possible to obtain the same effect as that of the above-described embodiment. Further, in the case of the micromotor 20 of this embodiment, since the stator 22 is made small, there is an advantage that it can be made more compact.

In the above embodiment, the rotor 1
An example in which a magnetic attraction mechanism is used as a drive unit that causes 1 or 21 to be attracted to the stators 12 and 22 and rolls has been described. The drive unit is the electrostatic device used in the wobble motor described in FIG. An adsorption mechanism can also be adopted. By doing so, it is considered possible to further reduce the size of the micromotor.

[0023]

As is apparent from the above description, according to the present invention, the rotor and the stator of the wobble motor are formed with the screws that mesh with each other, so that the axial displacement of the rotor can be directly taken out. A high-output linear driving micromotor can be obtained. Further, since the axial displacement can be increased by increasing the length of the screw, a micromotor with a large linear displacement can be obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a wobble motor used in the present invention.

FIG. 2 is an explanatory diagram for explaining the operating principle of the wobble motor.

FIG. 3 is a plan view showing an embodiment of a linear driving micromotor according to the present invention.

FIG. 4 is a vertical sectional view of the micromotor.

FIG. 5 is an enlarged plan view of a main part of the micromotor.

FIG. 6 is an enlarged vertical sectional view of a main part of the micromotor.

FIG. 7 is a circuit diagram showing a drive circuit of the micromotor.

FIG. 8 is a plan view showing another embodiment of the linear driving micromotor according to the present invention.

9 is a vertical cross-sectional view of the micromotor of FIG.

[Explanation of symbols]

 10, 20 Linear drive micromotor 11, 21 Rotor 11a, 21a Screw 12, 22 Stator 12a, 22a Screw 15 Drive circuit (drive means)

Claims (2)

[Claims] 1. A stator having a shaft-shaped rotor and a cylindrical inner peripheral surface having a diameter larger than the outer diameter of the rotor, the stator being arranged on the outer periphery of the rotor, and the rotor being attracted to the inner peripheral surface of the stator. A linear drive micromotor, characterized in that screws that mesh with each other are formed on the outer peripheral surface of the rotor and the inner peripheral surface of the stator. 2. A rotor having a cylindrical shape, a cylindrical outer peripheral surface having a diameter smaller than the inner diameter of the rotor, and a stator disposed inside the rotor, and the rotor is attracted to the outer peripheral surface of the stator to form a circumferential direction. And a drive means for rolling the motor into a linear drive micromotor, wherein the inner peripheral surface of the rotor and the outer peripheral surface of the stator are formed with screws that mesh with each other.