JPS63181660A - Linear dc motor - Google Patents

Abstract

PURPOSE:To reduce the weight of a linear DC motor by using a yoke in which its sectional area is reduced near the center thereof with small magnetic flux amount and increased at locations near both ends. CONSTITUTION:A pair of permanent magnets 1a, 1b of rectangular parallelopiped are disposed separately at opposed faces 1U and 1D. Nonopposed faces 1u, 1d are held closely in contact with side yokes 2a, 2b, a central yoke 3 of the same shape as the yokes 2a, 2b is disposed therebetween, and both ends are held at a predetermined interval by side plates 7L, 7R. A movable coil 6 is wound circumferentially at the yoke 3. In this case, the yokes 2a, 2b and 3 are so formed in width that the both ends become twice as large as the width of the magnets 1a, 1b, and a rhombic hole 8 having the length of half of the thickness at a short diagonal and the length of half of the yoke 3 is opened at the center of the side at the part having the same width as that of the magnets 1a, 1b of the yoke 3. Thus, total magnetic flux amounts are increased toward both ends.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention (Field of Industrial Application) The present invention relates to a linear motor, and particularly to a voice coil type linear DC motor with a long stroke width.

(Prior art) In the conventional voice coil type linear DC motor, the sixth
As shown in the figure, each yoke (52a) (52b) (53
) are held by the side plates (57L) (57R), and a pair of permanent magnets (51a) (5l b) held by the side yokes (52a) (52b) generate a uniform magnetic flux over the entire stroke of the motor. A current was passed through the moving coil (56) within the coil to obtain thrust within the stroke. With this type, it is necessary to generate a uniform magnetic flux over the entire stroke, so
In particular, when the stroke is long, the total amount of magnetic flux becomes considerably large, and the amount of magnetic flux of each yoke (52a), (52b), and (53) becomes maximum at the respective ends (L) and (R). A conventional linear DC motor has each yoke (52a) (52
b) (53) is a rectangular parallelepiped, and each yoke (52)
a) (52b>) Each yoke (52a) (53) should be
Since the cross-sectional area of 2b) (53) was determined, each yoke (52a), (52b), and (53) became extremely heavy, which was an obstacle to reducing the weight of the motor.

(Problems to be Solved by the Invention) As the stroke of a linear DC motor becomes longer, its total magnetic flux increases. For this reason, each yoke of the motor has a rectangular parallelepiped shape with a cross-sectional area that prevents magnetic flux saturation at both ends. Therefore, as the stroke of the linear DC motor becomes longer and the total amount of magnetic flux increases, the weight increases in proportion to this, which has been a problem in reducing the weight of the linear DC motor.

[Structure of the invention] (Means for solving the problem) In the case of a voice coil type linear DC motor, the magnetic flux emitted from the permanent magnet passes through the left and right center yokes with the center of the motor as the border, and then sequentially passes through the center yoke and the side yokes. The magnet passes through the holding member, which is the holding means for holding the magnet, and the side yoke, and returns to the permanent magnet. At this time, if magnetic resistance is ignored, the total magnetic flux in the yoke is approximately proportional to the distance from the center of the motor. Therefore, in order to solve the above-mentioned problems, it is sufficient to form yokes whose cross-sectional areas are changed according to the magnetic flux passing through each yoke. In other words, the cross-sectional area is made small enough to prevent magnetic flux saturation near the center of the yoke, where the amount of magnetic flux is small, and the cross-sectional area is made large to prevent magnetic flux saturation near the ends of the yoke, where the amount of magnetic flux is large. By using this, a lightweight linear DC motor can be provided.

(Function) When a linear DC motor is constructed as described above, the total amount of magnetic flux emitted from the permanent magnets is small near the center;
The total amount of magnetic flux increases as it approaches both ends. Accordingly, each yoke also increases its cross-sectional area, so that magnetic flux saturation does not occur. By forming the yoke in this way, it is possible to reduce the weight of the linear DC motor.

(Example) An example of the present invention will be described using FIGS. 1 to 5.

As shown in Figure 2, a pair of rectangular permanent magnets (la) (
lb) have opposing surfaces (IU) (ID) and are spaced apart. The non-opposed surfaces (1u) and (1d) are held in close contact with the side yokes (2a) and (2b). Furthermore, the central yoke (3), which has the same shape as the side yokes (2a) (2b),
) are arranged between them, and these pair of side yokes (2
a) Attach both ends of (2b) and central yoke (3) to side plates (7L).
) (7R) and are held at regular intervals.

Also, the permanent magnets (1a) (1b) and the central yoke (3
), a movable coil (6) having a coil (5) wound in multiple layers around a bobbin (4) made of a non-magnetically conductive material is disposed around the central yoke (3).

Side yokes (2a) (2b) and central yoke (3)
As shown in Figure 3, both ends are permanent magnets (1a) (1b).
The width is twice the width of the permanent magnet (1a), and the plate thickness is such that magnetic flux saturation does not occur in this state, and the width at both ends becomes the same as the width of the permanent magnets (1a) and (1b). The sides are cut out with a cutting straight line so that the width from both ends to the center is 0.

Further, as shown in Fig. 4, a short diagonal half the length of the plate thickness is placed in the center of the side of the part of the central yoke (3) with the same width as the permanent magnets (la) and (lb). Central yoke (3
) with a long diagonal diamond-shaped hole (8).

Next, the operation of the present invention will be explained with reference to FIG.

The total amount of magnetic flux (m) emitted from the permanent magnets (1a) (1b) increases from the center toward both ends, and the total amount of magnetic flux becomes maximum at both ends.

At this time, the cross-sectional area of the central yoke (3), which was small at the center, increases in size as the total amount of magnetic flux increases, and magnetic flux saturation does not occur even at both ends where the total amount of magnetic flux is maximum. Also, the magnetic flux (m) passes through the side plates (7L) (7R), and when passing through the side yokes (2a) and (2b), the magnetic flux (m) is permanently Since the magnets (1a) and (1b) return to each other, magnetic flux saturation does not occur.

By forming the side yokes (2a) (2b) and the center yoke (3) in this manner, it is possible to construct a linear DC motor that is lighter in weight than a linear DC motor constructed of conventional rectangular yokes. In this example, each yoke was thinned out as described above to the extent that it could overcome the attraction force of the permanent magnets (1a) (1b) to the central yoke (3), but if the rigidity can be maintained, As in the central yoke (3') of the other embodiment of the present invention shown in FIG. A plurality of holes may be formed sequentially from the left and right from the large hole (9c) to the small holes (91) and (9r). In other words, within the range that can maintain rigidity,
In the present invention, each yoke may be formed so as to have a cross-sectional area at least large enough not to cause magnetic flux saturation, and to have a decreasing portion in which the cross-sectional area decreases from both ends toward the center.

It goes without saying that the side plate has a cross-sectional area large enough to prevent magnetic flux saturation.

[Effects of the Invention] As described above, the present invention provides the yoke of a voice coil type linear motor with a cross-sectional area at least within a range that does not cause magnetic flux saturation, and whose cross-sectional area increases from both ends to the center. Since the linear direct current motor is formed to have a reduced portion that makes the motor smaller, the total weight of the conventional linear DC motor can be reduced by about 20%, and its practicality can be greatly increased.

[Brief explanation of the drawing]

FIG. 1 is a partial cross-sectional state diagram showing the operation of an embodiment of the present invention, FIG. 2 is a perspective view showing the same configuration, FIG. 3 is a plan view showing the shape of the yoke, and FIG. FIG. 5 is a side view showing the shape of a yoke in another embodiment of the present invention, and FIG. 6 is a perspective view showing the configuration of a conventional example.

Claims (1)

[Claims] a pair of permanent magnets having opposing surfaces for generating magnetic flux;
A pair of side yokes that hold the non-opposing surfaces of the permanent magnets in close contact and allow magnetic flux to pass therethrough; a central yoke that is provided between the permanent magnets in parallel with the opposing surfaces and allow magnetic flux to pass therethrough; and the side yokes and the center yoke. In the linear DC motor, the linear DC motor comprises a holding means for holding the magnets at a predetermined constant interval and passing magnetic flux therethrough, and a moving coil disposed around the central yoke between the permanent magnet and the central yoke. The yoke and the central yoke have a minimum cross-sectional area at both ends that does not cause magnetic flux saturation with the maximum amount of magnetic flux of the linear DC motor, and the cross-sectional area decreases linearly so that the cross-sectional area becomes 0 at the center. What is claimed is: 1. A linear direct current motor, characterized in that it has a cross-sectional area larger than the minimum shape of the linear DC motor, and is formed to have a gradually decreasing portion from both ends toward the center.