JPS63129848A - Linear actuator - Google Patents

Abstract

PURPOSE:To widen the range of the driving force of a linear actuator to be constant, by arranging a sub-magnet having poles in the same direction as that of first magnets, near both the ends of the moving units of the first magnets in the moving direction, so that the sub-magnet may be confronted with the first magnets. CONSTITUTION:A sub-magnet 6 is embedded in a yoke 4 so that a magnetic circuit 3 may be confronted with both the front and rear end sections of main permanent magnets 5. The sub-magnet 6 is placed in the same direction as the magnetized direction of the main permanent magnets 5. By the density distribution of magnetic flux for penetrating coils 7 in the moving direction of the coils 7 at a gap center position on the magnetic circuit 3, the characteristic of the magnetic flux which is increased at both the ends and is suddenly reduced is shown. As a result, when the coils 7 are positioned at both the ends, then the magnetic flux for penetrating the coils 7 is averaged, and a flux- generating force on the coils 7 is not reduced compared with the force on the magnetic circuit without the fitted sub-magnet 6. Accordingly, without changing the lengths of the main permanent magnets 5, a range for obtaining the uniform generating force on the coils can be widened.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial use of diacritics) The present invention relates to a linear actuator, and uses a transducer for a recording medium on which information is recorded in a special recording device or the like. The present invention relates to a linear actuator that can be moved reciprocally.

(Prior Art) FIG. 14 shows a conventional example of a disk recording device using a linear actuator that is closest to the present invention. In this device, a driving coil 34 movable in the theta direction of the transducer 30 is disposed within the magnetic gap of a magnetic circuit 31 composed of a yoke 32 and a permanent magnet 33, and a current is passed through the coil 34. A carriage 35 on which a transducer 30 is mounted by generating a magnetic force in a coil 34
A drive motor with this structure is generally called a linear actuator.

Figure 1S shows the magnetic circuit 3 of this linear actuator.
1 is shown. In this magnetic circuit 31, FIGS.
Various magnetic paths are formed, as indicated by arrows in the figure. However, the only magnetic path actually required to drive the coil 34 is the one indicated by arrow a in FIG. 16, and the magnetic flux passing through the other magnetic paths is unrelated to driving the transducer 30.

FIG. 17 shows the distribution of magnetic flux density flowing in the direction of arrow a in FIG. 16 in the magnetic gap of this magnetic circuit 31. The distribution of magnetic flux density in the magnetic gap as shown in Fig. 17 is due to the magnetic flux shown by arrows b-c in Fig. 16.
It suddenly decreases at the end of the permanent magnet 33 at point A and point 0. By the way, when the drive filter 34 is located near the point A-C of the end portion of the permanent magnet 33, the coil generated force has a smaller value than when it is located at another position, as shown in FIG. 15'. This results in problems such as variations in the seek speed of the transducer 30.

Therefore, in conventional linear actuators, the coil 34 is driven only in the region where the magnetic flux density is constant, and the region where the magnetic flux density decreases at the front and rear ends of the permanent magnet 33 is not used, or the coil 34 is driven at the front and rear ends of the permanent magnet 33. By controlling the current to increase the current flowing through the coil, the force generated by the coil was kept constant.

(Problems to be Solved by the Invention) As mentioned above, conventional linear actuators for recording devices do not use the magnetic gaps between the front and rear magnet ends in the direction of movement of the transducer, or add an extra control circuit. Because it is a small fl! ! It was disadvantageous for quantification.

Therefore, an object of the present invention is to propose a linear actuator for a recording device in which the coil generated force remains constant even if the entire magnetic gap formed by the yoke and the full length of the magnet is used for driving the fill.

[Structure of the invention]

(Means for Solving the Problems) In the linear actuator for a recording device of the present invention, at least one main permanent magnet and a yoke surface having an air gap near both front and rear ends of the range in which the drive coil can move, At least one sub-magnet is installed opposite the main permanent magnet, and the magnetic poles of the sub-magnet are arranged in the same direction as those of the main permanent magnet.

(Function) In the linear actuator configured in this way, the direction of the magnetic flux unrelated to the coil drive generated from the main permanent magnet at both the front and rear ends of the main permanent magnet is changed by providing the sub magnet. change direction. Then, the magnetic flux density required to drive the coil increases, and the region in which the force generated in the drive coil is constant expands. Also,
By embedding the sub-magnet in the yoke, the air gap between the main permanent magnet and the yoke does not change, so the maximum coil generation force remains the same compared to when no sub-magnet is attached. By installing this sub-magnet in this way, it is possible to make the linear actuator smaller and lighter with the same drive coil stroke.

(Example) The present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a first embodiment of the present invention, and is a schematic diagram of a disk recording device equipped with a linear actuator for a recording device. 1 is the disk, 2 is the transducer, 8
indicates a carriage.

Moreover, only the magnetic circuit 3 of the linear actuator is shown in FIG. This magnetic circuit 3 includes a main permanent magnet 5 and a yoke 4.
A sub-magnet 6 is embedded in the yoke 4 so as to face both the front and rear ends of the main permanent magnet 5. This sub-magnet 6 is placed in the same direction as the magnetization direction of the main permanent magnet 5.

In such a magnetic circuit 3, the magnetic flux density distribution passing through the coil 7 in the direction in which the fill 7 moves at the center position of the gap exhibits a characteristic of increasing at both ends and decreasing rapidly, as shown in FIG. The sudden decrease is the same as in the conventional case, but the average magnetic force in the coil having a predetermined length hardly decreases because it increases before that. In other words,
When the coil 7 is located at both ends, the magnetic flux passing through the fill 7 is averaged, and the force generated in the coil 7 does not decrease compared to a magnetic circuit in which the sub-magnet 6 is not attached.

Therefore, without changing the length of the main permanent magnet 5, the area in which uniform coil generation force can be obtained can be expanded.

Furthermore, since the gap is not changed, the motor constant is also not changed.

In fact, the inventors calculated Lm=28m+a as shown in FIG.
, the main permanent magnet 5 with dimensions of Tm=3mys, Lsm=7
xx,'l s m / When a fill is attached to the magnetic circuit to which the dragon's sub-magnet 6 is attached, the variation in the coil generated force (F/Fmax) is reduced to 5 within the magnet length region, as shown in Fig. 3.
We have obtained a linear actuator that is within %.

However, FmaX is the maximum force generated in the coil.

As a result, compared to the one without the sub-magnet 6, 5%
A linear actuator was obtained in which the range of variation in coil generated force within the range increased by about 20%, and the maximum coil generated force did not change.

In the first embodiment described above, the case is described in which the main permanent magnet 5 and the yoke 4 form at least one pair, and one sub magnet 6 is arranged at each of the front and rear ends of the main permanent magnet 5. The effects of the present invention can be obtained even when a large number of sub-magnets 6 are used, and even when the shapes thereof are changed.

Next, a second embodiment will be described with reference to FIGS.

FIG. 5 schematically shows a disk recording device equipped with a linear actuator for a recording device according to the second embodiment.

Note that the same parts or parts as those in the first embodiment are given the same reference numerals, and the explanation thereof will be omitted. Also, in Figure 6,
Only the magnetic circuit 13 of the linear actuator is shown. This magnetic circuit 13 is composed of a permanent magnet 15 and a yoke 14, and the magnetic gap formed by the permanent magnet 15 and the yoke 14 is large at the center of the permanent magnet 15.
The shape of the center yoke 14 is changed (for example, into a trapezoidal shape) so that both the front and rear ends of the center yoke are smaller.

In such a magnetic circuit 13, the magnetic flux density distribution passing through the coil 7 in the direction in which the coil 7 moves becomes large at both ends and rapidly decreases, as shown in FIG. This means that if the coil 7 is located at both ends, the coil 7
The force generated in one coil 7 by averaging the magnetic flux passing through the coil 7 does not decrease compared to a magnetic circuit in which the magnetic gap interval is not changed.

Therefore, without changing the length of the permanent magnet 15, the area in which uniform coil generation force can be obtained can be expanded.

In fact, inventor 5 has determined that L m = 28 as shown in FIG.
Me, a permanent magnet with dimensions Tm = 3 mm, L a = 10
ms, L b =33111%.

Gma X:2,9111SGmin=2.131
31 A coil is attached to a magnetic circuit having a magnetic capacitor 7' to generate a fill generating force (F/F) as shown in Fig. 9.
A linear actuator in which the variation in max) is within 5% in the magnet length region has been obtained. However, Fmax is the maximum force generated in the coil. As a result, the magnetic gap does not change in the direction of coil movement (G m a x
=Gmin=2.5 mm), the range of coil generated force variation within 5% increases by about 20%.

In the second embodiment described above, the magnetic gap formed by at least one pair of permanent magnets 15 and yoke 14 is changed to a trapezoidal shape in the moving direction of the coil 7, but this shape is changed to an arcuate shape. The same effect can be obtained by changing the yoke surface that opposes the permanent magnet through the magnetic gap.

Next, a third embodiment will be described with reference to FIGS. 10 and 11. 10 and 11 are a perspective view and a plan view of the magnetic circuit. Other parts are the same as those in the first and second embodiments.

In the third embodiment, sub-magnets 26 are arranged at both ends of the permanent magnet 25 in order to increase the magnetic flux density distribution at both ends of the permanent magnet 25. The direction of magnetization of this sub-magnet 26 is set so that the magnetic path of the magnetic flux from the permanent magnet 25 is directed toward the yoke 24 on the opposite side, that is, in order to prevent leakage of magnetic flux from occurring at the end of the permanent magnet 25. The direction is to do so. With such a configuration, the magnetic flux density increases at the end of the permanent magnet 25 due to the repulsive force of the sub-magnet 26, and the same effects as in the first and second embodiments can be obtained.

FIGS. 12 and 13 are a perspective view and a plan view of a magnetic circuit in the fourth embodiment. Here, a shield member 27 such as an aluminum plate is arranged in place of the sub-magnet 26 in the third embodiment. Even in such a configuration, leakage magnetic flux does not occur at the end of the permanent magnet 25, and the effect of increasing the magnetic flux density can be expected to some extent.

In addition, in the above-mentioned embodiment, the permanent magnet 2 is attached to the yoke 24.
5 is fixed, but it is not limited to a permanent magnet, and may be a 'xi stone, etc. Similarly, the sub-magnets 6 and 26 are not limited to permanent magnets either. Furthermore, a permanent magnet may be provided on the moving body side.

In addition, in the above embodiment, the 'J near actuator is applied to a magnetic disk device, but it is not limited to this, and can be applied to precision positioning devices, other information recording/reproducing devices, various AV devices, etc. Can adapt. As described above, the present invention can be modified and used in various ways without departing from the gist thereof.

〔Effect of the invention〕

As described in detail above, according to the present invention, it is possible to widen the area in which the driving force of the linear actuator is constant, so that it is possible to reduce the size and weight of the linear actuator.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view of an IJ near actuator according to a first embodiment of the present invention, FIG. 2 is a perspective view of a magnetic circuit according to the first embodiment, and FIGS. 3 and 4 5 is a distribution diagram showing the magnetic flux density distribution and fill generation force distribution in the magnetic gap in the magnetic circuit according to the first embodiment, and FIG. 5 is a schematic diagram of the linear actuator according to the second embodiment of the present invention. A perspective view, FIGS. 6 and 7 are a perspective view and a plan view of a magnetic circuit according to a second embodiment, and FIGS. 8 and 9 are a perspective view and a plan view of a magnetic circuit according to a second embodiment.
A distribution diagram showing the magnetic flux density distribution and coil generation force distribution in the magnetic gap in the magnetic circuit according to the third embodiment, FIGS. 10 and 11 are a perspective view and a plan view showing the magnetic circuit in the third embodiment, 12 and 13 are a perspective view and a plan view showing a magnetic circuit in the fourth embodiment, and FIG. 14 shows a conventional linear actuator generally showing the magnetic flux density in the magnetic gap in the conventional magnetic circuit. FIG. 3 is a distribution diagram showing distribution and coil generated force distribution. DESCRIPTION OF SYMBOLS 1... Disk 2... Transducer 3... Magnetic circuit 4... Yoke 5... Main permanent magnet (first magnet) 6... Sub-magnet 7... Coil (second (magnet) 8... Carriage (mobile body) Agent Patent attorney Nori Ken Yudo Chika Kikuo Takehana Figure 1 Figure 2 Figure 3 Figure 5 Figure 7 Ward 8 Figure m! J Prisoner / Figure 12 Figure 13 Figure 15 Figure 16 Figure 18

Claims (2)

[Claims] (1) comprising a first magnet and a second magnet disposed in a magnetic gap formed by the first magnet and the yoke;
A linear actuator in which at least one of the first and second magnets is formed of a coil, and the moving body is moved in a predetermined direction by controlling energization of the coil, wherein the first magnet moves the moving body in a predetermined direction. Near both ends of
A linear actuator characterized in that a sub-magnet having a magnetic pole in the same direction as the first magnet is arranged to face the first magnet. (2) The linear actuator according to claim 1, wherein the sub-magnet is embedded in the yoke to make the magnetic gap uniform.