JPH0487544A - Dc brushless motor - Google Patents

Abstract

PURPOSE:To suppress skin effect and to achieve high torque and high efficiency even during high speed rotation by a constitution wherein a plurality of coils are arranged concentrically on a substrate and a plurality of split coils are connected in parallel with a power supply. CONSTITUTION:A plurality of coils 120... are arranged concentrically on a substrate and a plurality of split coils 120a, 120b, connected in parallel with a power supply, are stacked vertically in two stages. The split coils 120a, 120b have identical constitution. Surface area of one coil 120 increases by an amount corresponding to the increase of the matching face of the split coils 120a, 120b without varying the number of turn, cross-sectional area or ampere turn. Accordingly, skin effect is suppressed and the current level does not decrease even during high speed rotation thus increasing the motor torque.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a DC brushless motor for low voltage, high current drive.

"Prior Art" A conventional DC brushless motor (hereinafter abbreviated as "motor") will be explained based on FIGS. 4 to 7.

This motor is generally composed of a stator lO, a rotor 20, an output shaft 30 fixed to the rotor 20, and a back yoke 40 made of a magnetic metal such as pure iron.

The stator 10 includes a resin disk-shaped substrate 11 made of a non-magnetic material, and a number of pieces arranged on the substrate 11 along the circumferential direction, for example, a multiple of 3 (in the motor shown in FIG. 5, 12 pieces). The coil 12 is made up of several coils 12. As the coil 12, as shown in FIG. 6, coil material 12a of copper foil is overlapped in the thickness direction and wound in a substantially triangular shape, or as shown in FIG. 7, a coil material 12b of round wire is used. There are some that are wound into a substantially triangular shape, but all of them are constructed by winding one or more coils of material. Further, the outer peripheral end portion of the substrate 11 is fixed to a housing (not shown).

The rotor 20 is formed into a disk shape and is connected to the output shaft 3.
0, a magnet 22 disposed on the inner surface of the support plate 21 (lower surface in FIG. 5) facing the coil 12, and a magnet 22 between the support plate 21 and the output shaft 30. It includes a cylindrical spacer 23 that is fixed and connects the two.

The back yoke 40 is disposed on the back side of the substrate 11 at a position corresponding to the magnet 22, and rotates with the rotation of the rotor 20.

In the conventional motor described above, as shown in FIG.
It can be driven by applying rotational force to the 0.

"Problems to be Solved by the Invention" By the way, when the above-mentioned C brushless motor is rotated at high speed, the direction of the current flowing through the coil 12 is sequentially changed. By sequentially changing the direction of the current flowing through the coil 12 in this way, when the frequency increases (when the rotational speed increases), a so-called skin effect occurs in which the current is difficult to flow only near the surface of the coil material. therefore,
If you try to rotate it at high speed, the resistance will increase, the current value will decrease, and the torque and efficiency will also decrease.

Since the back electromotive force that causes the skin effect is proportional to the current value, the effect of the skin effect becomes particularly large when a large current is passed at a low voltage, causing a significant drop in torque and efficiency at high rotations. This may cause problems.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a DC brushless motor that exhibits high torque and high efficiency even at high rotation speeds.

"Means for Solving the Problem" In the invention, each coil arranged on a substrate is constituted by a plurality of divided coils arranged concentrically with each other and connected in parallel to the power supply side.

"Effect" Looking at individual coils made up of multiple split coils, compared to conventional coils, by setting the cross-sectional area of the split coil material to 1/N1 and the number of split coils to N,
The surface area of the coil can be increased without changing the overall ampere turns of the coil. Therefore, the influence of the skin effect can be suppressed to a small extent, and high torque and high efficiency can be achieved even at high rotation speeds.

"Example" Hereinafter, an example of the present invention will be described with reference to the drawings. Note that configurations common to those of the above-mentioned conventional technology are given the same reference numerals and description thereof will be omitted.

First example FIG. 1 is a sectional view of a main part showing a first embodiment of the present invention.

This embodiment is an example in which the stator coil 120 is constructed by winding a coil material 120a of copper foil. That is, in this embodiment, a plurality of coils 120 arranged on the board are each a plurality of divided coils 12 arranged concentrically with each other and connected in parallel to the power supply.
0a and 120b are stacked vertically in two stages. The individual divided coils 120a and 120b have the same configuration, and the copper foil coil material 121 that constitutes them has a thickness t and a length C compared to the conventional coil material 12a shown in FIG. They are the same, and the width W is set to approximately half the value. In other words, although the cross-sectional area of the conventional copper foil coil material 12a is half that of the conventional copper foil coil material 12a, and the resistance value of the divided coils 120a (120b) is doubled, the divided coils are made into a set of two, and the power supply side Since the coil is used in parallel connection with the coil, when viewed as a single coil, the inductance and resistance values are no different from conventional ones, and the ampere turns are also the same. Note that both the split coils 120a.

Although the mating surfaces of 120b do not necessarily need to be joined,
In consideration of handling, etc., they may be joined using an insulating adhesive if necessary.

According to the motor with the above configuration, the stator coils 120 and
Each coil 120 is composed of a plurality of divided coils 120a and 120b connected in parallel to the power supply side, and each coil 120 has a smaller number of turns, cross-sectional area, and ampere turns than the conventional coil 12. Without any change, the surface area increases by the increase in the mating surface S of both split coils 120a and 120b. Therefore, the influence of the skin effect is reduced, and the torque of the motor can be increased compared to conventional motors without decreasing the current value even at high rotation speeds.

FIGS. 2(a) to 2(f) compare the performance of the motor with the above configuration and a conventional motor. As can be seen from these figures, the motor with the above configuration is better able to suppress the increase in effective resistance value than conventional motors even when the rotational speed increases and at the same time the frequency of the current flowing through the coil increases. At the same time, it is possible to reduce the current drop, and it is possible to exert torque at a value close to the ideal value (Fig. 2 (a) to (d))
reference).

As a result, as shown in FIGS. 2(e) and 2(f), the torque-efficiency characteristics and rotational speed-efficiency characteristics of the motor can be brought closer to ideal curves.

2nd fruit %1 FIG. 3 shows a second embodiment of the invention.

[In the above-mentioned first embodiment, an example was shown in which the present invention was applied to a stator coil made of a copper foil coil material, but here, the present invention is applied to a stator coil made of a round wire coil material. Applying the invention.

In this example as well, the round wire coil material 122 has the same length and the same number of turns as the conventional round wire coil material 12b, and the cross-sectional area is set to half that. In this embodiment as well, the first
Similar to the embodiment, the surface area of the coil 120 can be increased, the skin effect can be reduced, and efficiency can be achieved, especially in the high frequency range. ” Nao, in each of the above embodiments, two stator coils are used.
Although the configuration is made up of three divided coils, the present invention is not limited to this, and may be configured with three or more divided coils. In that case, the cross-sectional area of the coil material constituting the split coil should be set to 1/N (N: number of split coils) of the cross-sectional area of the conventional coil material.
If the length and number of turns are set to the same value as the conventional coil, the resistance value and inductance can be maintained at the same level as the conventional coil.

In addition, in each of the above embodiments, the stator coil is constructed by stacking the split coils one above the other; however, the stator coil is not limited to this, and the stator coils are arranged on the inner and outer circumferential sides on the same plane while remaining concentric. They may be arranged radially shifted so that

"Effects of the Invention" As explained above, in the present invention, each coil arranged on the board is composed of a plurality of divided coils arranged concentrically with each other and connected in parallel to the power supply side. Therefore, the surface area of the coil can be increased without changing the ampere turns of the entire coil, and the influence of the skin effect can be reduced. Therefore, high torque and high efficiency can be achieved even at high rotation speeds.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of the main parts showing the first embodiment of the present invention, FIG. 2 is a diagram comparing the characteristics of the motor of the first embodiment and a conventional motor, and FIG. 3 is a diagram of the motor of the present invention. FIG. 7 is a vertical cross-sectional view of main parts showing a second embodiment. Figures 4 to 7 are diagrams showing conventional motors, with Figure 4 being an enlarged vertical sectional view of the motor, Figure 5 being a plan view of the board and motor, and Figure 6 being a perspective view showing an example of the coil. , FIG. 7 is a perspective view showing another example of the coil. O...Stator O...Rotor O...Output shaft OO...Substrate 20...Coil 20a, 120b...Divided Coil 21...
・Coil material 22...Coil material

Claims (1)

[Claims] A DC brushless motor comprising a rotor that rotates integrally with an output shaft, and a stator in which a plurality of coils are arranged along the circumferential direction to apply rotational force to the rotor on the board, wherein the stator is arranged on the board. A DC brushless motor characterized in that each coil is constituted by a plurality of divided coils arranged concentrically with each other and connected in parallel to a power supply side.