JPH0448146Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a linear DC motor.

This type of linear DC motor is being put to practical use as a driving device for linear motion of electronic sewing machines, industrial robots, measurement control equipment, and the like.

FIG. 1 is a schematic diagram showing an example of a conventional linear DC motor. In the figure, 1 and 2 are outer yokes, 3
indicates the central yoke, which is made of soft magnetic material and is magnetically closed circuit. 4 and 5 are flat permanent magnets, and the opposing poles are set to be the same. 6 is a moving coil that slides on the central yoke. In such a linear DC motor, if the magnetic flux density from the permanent magnet applied to the moving coil 6 is B, and the current flowing through the coil 6 is I, then the force (thrust) F is calculated by Fleming's left-hand rule as follows: = I×B [N/m]. Therefore, it seems that in order to increase the thrust force, it is necessary to increase I, that is, to make more current flow through the coil 6 or to increase the number of turns, or to increase B by using a strong permanent magnet. However, in conventional devices, the soft magnetic materials forming the outer yokes 1 and 2 and the central yoke 3 are generally operated at a state close to magnetic saturation. Therefore, when the magnetic flux from the coil 6 is superimposed, the thrust characteristics cannot be as shown in the ideal straight line A as shown in Figure 2, and the thrust almost increases at a certain current value i ₁ as shown in the curve B. I won't. In order to solve this thrust stagnation, it is necessary to increase the cross-sectional area of the central yoke 3 and the outer yokes 1 and 2, which results in an increase in size and weight, which becomes a bottleneck in reducing the size and weight. ing.

In view of these points, the present invention creates a magnetic flux in the opposite direction to the magnetomotive force generation direction of the moving coil to prevent the magnetic saturation of the yoke, thereby increasing thrust with good linearity, resulting in a compact and lightweight design. The main purpose is to propose a linear DC motor that can be

An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 3 is a front view showing one embodiment of the present invention, and in the figure, parts having the same meaning as in the example of FIG. 1 are given the same reference numerals and will be explained.

Reference numeral 7 denotes a fixed coil, which is wound around the end of the central yoke 3, and the magnetic field generation direction of the coil 7 is opposite to that of the movable coil 6, and more preferably, the magnetomotive force NI is also the same as that of both coils. are selected so that they are approximately equal and their magnetomotive forces cancel each other out. By providing the fixed coil 7 that generates a magnetic field in the opposite direction to the moving coil 6, the closed magnetic path composed of the central yoke 3 and the outer yokes 1 and 2 is maintained magnetically unsaturated. Extremely high thrust retention with almost the same linearity as the straight line A in FIG. 2 can be obtained. As a result, not only the linearity between the input current of the moving coil and the thrust force is greatly improved, but also the cross-sectional area of the yoke has to be made larger for safety reasons, since conventional equipment had to be designed with magnetic saturation in mind. However, efforts were made to make it smaller and lighter. In addition, when switching the current direction of the moving coil 6 from the rightward direction to the leftward direction, as shown in FIG. 4, by connecting the moving coil 6 and the fixed coil 7 in series in opposite directions,
The generated magnetic field is automatically canceled out.

In addition, the present invention allows the use of four or more permanent magnet plates instead of the non-uniform magnetic field type linear motor using two permanent magnets as described above. It goes without saying that the magnetic field uniform type may also be used.

As described above, according to the present invention, the outer yoke made of a soft magnetic material and the center yoke constitute a closed magnetic path with a cross section shaped like a Japanese letter. In a linear motor in which a permanent magnet is bonded to the inside of the yoke, and the central yoke is equipped with a sliding movable coil that generates a magnetomotive force in the longitudinal direction, the movable coil is installed so that the central yoke does not become magnetically saturated. Since the central yoke is provided with a fixed coil that generates a magnetomotive force in the opposite direction to the magnetomotive force generation direction, the fixed coil can cancel out the magnetic oversaturation of each yoke caused by the driving of the movable coil. Therefore, the thrust of the movable coil increases in proportion to the increase in the current to the movable coil, which has the effect of improving the linearity of this type of motor. Furthermore, the minimum size of the yoke corresponding to the thrust of the moving coil can be set without increasing the size of the yoke more than necessary, thereby achieving reduction in size and weight.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing an example of a conventional linear DC motor, Fig. 2 is a diagram for explaining operational stability, Fig. 3 is a sectional view of a linear motor showing an embodiment of the present invention, and Fig. 4 is a schematic diagram showing an example of a conventional linear DC motor. The figure is a circuit diagram showing another example of the present invention. 1, 2...outer yoke, 3...center yoke,
4, 5... Permanent magnet, 6... Moving coil, 7...
Fixed coil.

Claims (1)

[Claims for Utility Model Registration] An outer yoke and a center yoke made of a soft magnetic material form a closed magnetic path with a cross section shaped like a Japanese letter. In a linear motor in which a permanent magnet is bonded to the inside and the central yoke is equipped with a sliding movable coil that generates magnetomotive force in the longitudinal direction, the movable coil is activated so that the central yoke does not become magnetically saturated. A linear motor characterized in that the central yoke is provided with a fixed coil that generates a magnetomotive force in a direction opposite to the direction in which the magnetic force is generated.