JPH04101656A - Voice coil type linear motor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a high-frequency, high-precision voice coil type linear motor used for positioning drive of heads of magnetic recording devices, IC hondas, and the like.

[Prior Art] Conventionally, as shown in Fig. 3, a voice coil type linear motor has a base l and an outer yoke 2 made of a ring-shaped magnetic material.
A magnet 3 having magnetic poles in the coil moving direction is fixed to the base 1 inside the outer yoke 2.

An inner yoke 4 made of a magnetic material is fixed to the tip of the magnet 3 so as to face the inner side of the outer yoke 2 with a gap G in between, so that the magnet 3 generates a magnetic field in the gap G. . In the gap G between the outer yoke 2 and the inner yoke 4, a ring-shaped armature coil 5 is connected to the inner yoke 4.
The coil support 51 is arranged so as to be movable along the side surface of the coil support 51, and coupled to the driven body via the coil support 51.

[Problems to be Solved by the Invention] By the way, a thrust is generated in the axial direction by passing a current through an armature coil in a magnetic field, and the generated thrust F is expressed as F=Br-r-1. Here, B is the magnetic flux density of the magnetic field, β is the coil length, and i is the intensity of the current.

In order to increase the thrust, the length of the coil and the current must be increased (therefore, the structure of the near motor must be thickened).

Increasing the magnetic flux density increases the thrust, but when the field is made of permanent magnets, there is a limit to the improvement of magnetic properties depending on the material of the permanent magnets. In particular, with rare earth magnets that have a high magnetic flux density, the magnetic flux density does not increase in proportion to the length even if the length of the magnet is increased.Also, in the case of electromagnets, there is a problem that the structure becomes large, and there is a limit to the improvement of characteristics. Ta.

The present invention aims to increase thrust without increasing coil length or current.

[Means for Solving the Problems] The present invention includes a ring-shaped outer yoke having one end fixed to a base, and a first ring-shaped outer yoke fixed to the base inside the outer yoke and having a magnetic pole in the coil moving direction. A voice coil comprising a magnet, an inner yoke fixed to the tip of the first magnet and facing the inner side of the outer yoke with a gap in between, and a ring-shaped armature coil provided in the gap. In the type linear motor, a second magnet is disposed on an end surface of the inner yoke opposite to the end surface on which the first magnet is fixed, and a magnetic pole of the surface of the second magnet facing the inner yoke is set to the second magnet. The magnet is magnetized to have the same polarity as that of the surface of the magnet No. 1 that is in contact with the inner yoke.

Further, the second magnet is fixed to a cover attached to an end surface of the outer yoke.

Further, the armature coil is fixed to a coil support having a mounting portion protruding from a notch provided between an end face of the outer yoke and the inner yoke.

[Function] A first magnet and a second magnet are provided on both sides of the inner yoke.
The magnetic flux of the two magnets concentrates on the inner yoke and then exits to the outer yoke to form a magnetic circuit, so the magnetic flux density generated in the gap between the inner yoke and the outer yoke is equal to This is the sum of the magnetic flux densities generated by the magnets, and the magnetic flux density is approximately twice as high.

"Example" The present invention will be described with reference to embodiments shown in the drawings.

FIG. 1 is a side sectional view showing an embodiment of the present invention, in which one end 21 of a ring-shaped outer yoke 2 is fixed to a base l, and the base 1 inside the outer yoke 2 is provided with magnetic poles in the direction of coil movement. A first magnet 3 is fixed thereto. An inner yoke 4 is fixed at one end surface 41 to the tip surface 31 of the first magnet 3, and a gap G is formed between the side surface of the inner yoke 4 and the inside of the outer yoke 2.
so that they face each other through. The other end 22 of the outer yoke 2 extends longer than the other end surface 42 of the inner yoke 4 in the coil movement direction, and a notch 23 is provided at a position between the other end 22 and the inner yoke 4. A cover 6 made of a magnetic material is fixed to the other end 22 of the outer yoke 2. A second magnet 7 having almost the same characteristics as the first magnet 3 is attached to one end surface 61 of the cover 6.
One end surface 71 of the second magnet 7 is fixed, and the other end surface 72 of the second magnet 7 is magnetized to the same polarity as the tip surface 31 of the first magnet 3 and is arranged so as to be in contact with the other end surface 42 of the inner yoke 4. .

That is, the magnetic flux emitted from the first magnet 3 passes through the inner yoke 4, passes through the air gap G, passes through the outer yoke 2, the base 1, and returns to the magnet 3 through the magnetic circuit, and from the second magnet 7 passes through the inner yoke 4. , a magnetic circuit is formed which passes through the outer yoke 2 and the cover 6 via an air gap and returns to the second magnet 7.

A ring-shaped armature coil 5, which is shorter than the axial length of the inner yoke 4, is arranged between the outer yoke 2 and the inner yoke 4 so that it can move along the side surface of the inner yoke 4 in the air. The coil support 8 is fixed to one end of the armature coil 5 and protrudes from the notch 23 of the outer yoke 2 so as to be coupled to a driven body via a coil support 8 having a section 81.

Therefore, with the above configuration, a magnetic circuit is formed in which the magnetic flux of the first and second magnets concentrates on the inner yoke 4 and then exits to the outer yoke, so that the gap G between the inner yoke 4 and the outer yoke 2 The magnetic flux density generated is the sum of the magnetic flux densities generated by the first magnet 3 and the second magnet 7, and almost double the magnetic flux density is obtained.

Note that the armature coil 5 may be longer than the axial length of the inner yoke 4, as shown in FIG.

[Effects of the Invention] As described above, according to the present invention, by arranging magnets with substantially the same characteristics on both sides of the inner yoke, almost twice the magnetic flux density can be obtained, and the coil length and length of the armature coil can be increased. The thrust can be increased without increasing the current, and this has the effect of providing a small, high-performance voice coil type linear motor.

[Brief explanation of the drawing]

FIG. 1 is a front sectional view showing an embodiment of the present invention, FIG. 2 is a front sectional view showing another embodiment, and FIG. 3 is a front sectional view showing a conventional example. 1... Base, 2... Outer yoke, 3... First magnet, 4... Inner yoke, 5... Armature coil, 6
・Cover, 7...Second magnet, 8...Coil support Patent applicant Yasuyo Electric Manufacturing Co., Ltd. Figure 1 Figure 2

Claims (1)

[Claims] 1. A ring-shaped outer yoke with one end fixed to the base;
a first magnet fixed to the base inside the outer yoke and having a magnetic pole in the direction of coil movement; and a first magnet fixed to the tip of the first magnet and opposed to the inner side of the outer yoke with a gap therebetween. In a voice coil type linear motor comprising an inner yoke and a ring-shaped armature coil provided in the gap, a second magnet is disposed on an end surface of the inner yoke opposite to the end surface to which the first magnet is fixed. A voice coil type characterized in that a magnet is arranged, and the magnetic pole of the surface of the second magnet facing the inner yoke is magnetized to the same polarity as the magnetic pole of the surface of the first magnet that is in contact with the inner yoke. linear motor. 2. The voice coil type linear motor according to claim 1, wherein the second magnet is fixed to a cover made of a magnetic material attached to an end surface of the outer yoke. 3. Claim 1 or 2, wherein the armature coil is fixed to a coil support having a mounting part protruding from a notch provided between the end face of the outer yoke and the inner yoke.
The voice coil type linear motor described.