JPH0523783U - Brushless motor - Google Patents

Abstract

(57) [Abstract] [Purpose] To obtain a brushless motor that can easily support thinner motors and can obtain a stable rotational position detection signal. A brushless motor having a cup-shaped rotor yoke provided with a space between a side wall open end and a drive magnet, and a position detecting element such as a Hall element arranged in the space.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a brushless motor, and more particularly to a brushless motor having an improved arrangement of position detecting elements for detecting the rotational position of a rotor.

[0002]

[Prior Art]

 Conventionally, a brushless motor has a circuit board (3) mounted on a bearing housing (1) coaxially holding a pair of ball bearings (2) (2) as a bearing member, for example, as shown in the schematic sectional view of FIG. ) And a magnetic core (5) are fixed, a salient pole tooth (7) formed on the magnetic core (5) is wound with a drive coil (9), and is rotatably supported by ball bearings (2) and (2). A rotor rotor (11) having a cup shape is fixed to the shaft (4) via a bush (10), and N poles and S poles are alternately magnetized in the circumferential direction inside the side wall (13) of the rotor yoke (11). The ring-shaped drive magnet (15) is fixed at a slight distance from the tips of the salient pole teeth (7), and the rotational position of the magnetic pole of the drive magnet (15) is converted into an electric signal and output. Hall element (17) (1 Only shown) arranged on the surface of the circuit board (3), were is positioned between the tip and the circuit board of the salient pole teeth in the vicinity of the drive the magnet bets (15) (7) (3).

In such a brushless motor, when the hall element (17) detects the rotational position of the drive magnet (15) and the drive current is switched to the drive coil (9) based on the detection signal, the rotor yoke ( 11) rotates.

[0004]

[Problems to be solved by the device]

 However, in the above-mentioned configuration, since the Hall element (17) is arranged between the circuit board (3) and the magnetic core (5), a certain distance is secured between the circuit board (3) and the magnetic core (5). It was necessary, and it was a constraint to make the brushless motor thinner.

Further, a configuration has been proposed in which a space between the circuit board (3) and the magnetic core (5) is narrowed by using a chip-shaped Hall element (17), but in this case, the Hall element (17) is structurally arranged. Most of the magnetic flux of the drive magnet (15) acting on () is absorbed by the magnetic core (5), and the output of the Hall element (17) is significantly reduced. Therefore, it is said that the stability is poor as a position detection signal. There are difficulties.

The present invention has been made to solve the above-mentioned conventional drawbacks, and it is easy to reduce the distance between the circuit board (3) and the magnetic core (5) and to reduce the thickness, and It is intended to provide a brushless motor that can obtain a reliable position detection signal.

[0007]

[Means for Solving the Problems]

 In order to solve such a problem, the present invention supports a circuit board on a stator member, rotatably supports a cup-shaped rotor yoke on the stator member, and rotates a north pole in a circumferential direction at a predetermined pitch. A drive magnet magnetized to the S pole and the S pole is arranged inside the side wall of the rotor yoke so as to face the circuit board, and a position detecting element for electrically detecting the rotational position of the drive magnet is provided on the circuit board. In addition to being arranged, a cavity is formed between the inside of the side wall of the rotor yoke and the drive magnet, and the position detection element is loosely inserted into the cavity from the side of the circuit board.

[0008]

[Action]

 In the present invention equipped with such means, the magnetic core around which the drive coil is wound is arranged in the stator member in order to rotate the rotor yoke, but the position detection element is provided in the space between the side wall of the rotor yoke and the drive magnet. Since it is arranged, the space between the circuit board and the magnetic core is narrowed.

Moreover, since the position detecting element is arranged in the space surrounded by the driving magnet and the side wall of the rotor yoke and having a high magnetic flux density, the magnetic flux of the driving magnet sufficient to obtain a sufficient output acts on the Hall element.

[0010]

【Example】

 Hereinafter, embodiments of the present invention will be described with reference to the drawings. The same parts as those in the conventional example are designated by the same reference numerals.

FIG. 1 is a half sectional view of a brushless motor according to the present invention.

Two bearings (21) (21) made of ball bearings are coaxially fixed to the hollow portion of the bearing housing (1) as a fixed cylinder.

A circuit board (3) is placed and fixed on a step portion provided on the outer periphery of the bearing housing (1).

On the surface of the circuit board (3), a plurality of power generating elements formed at the same pitch along a magnetic pole boundary of a drive magnet (15) described later are connected in series in a rectangular shape to form a substantially annular shape. The formed frequency generating coil (25) (not shown in FIGS. 2 and 3) is formed.

A magnetic core (5) formed by laminating magnetic steel sheets is fixed to the outer periphery of one end of the bearing housing (1), and a plurality of drive coils (7) are attached to the salient pole teeth (7) of the magnetic core (5). 9) is wound, and its lead portion is connected to a drive circuit (not shown) formed on the circuit board (3).

A cap-shaped rotor yoke (11) is screwed to a tip of a shaft (27) supported by a pair of bearings (21) (21) via a bush (29), and this rotor yoke (11) is A ring-shaped drive magnet (15) facing the tip of the magnetic core (5) at a slight distance is attached to the side wall (13) of the drive magnet (15). The N and S poles are alternately magnetized.

As shown in FIG. 2, in the side wall (13) of the rotor yoke (11), the front end open part (31) is expanded outward through the bent step part (33) to form the front end open part (31). A space (35) is formed between the drive magnet (15) and the drive magnet (15).

On the surface of the circuit board (3), for example, three Hall elements (17) (only one is shown) as a position detecting element for detecting the magnetic pole position of the drive magnet (15) have a shaft (27). It is arranged at a predetermined angle as the center.

These Hall elements (17) are loosely inserted so as not to come into contact with the open end portion (31) of the rotor yoke (11) and the drive magnet (15).

A rotary cylinder (37) is fixed to the tip of the shaft (27).

According to the present invention, the hall element (17) detects the rotational position of the drive magnet (15) and outputs a position detection signal. Based on the position detection signal, the drive coil (9) is supplied to the drive coil (9). The drive current is switched and energized to rotate the rotor yoke (11).

Since the Hall element (17) is not arranged between the circuit board (3) and the magnetic core (5), it is not necessary to secure the space between them, and the brushless motor is provided only by the height of the Hall element (17). The thickness of the rotor yoke (11) can be easily reduced, and the side wall (13) of the rotor yoke (11) can be simply modified.

Moreover, since the Hall element (17) is arranged in the region of high magnetic flux density by the drive magnet (15), its output signal is stable and reliable.

The present invention is not limited to the above-mentioned configuration, and a configuration as shown in FIG. 3, for example, is also possible.

That is, the driving magnet (15) facing the side wall (13) of the rotor yoke (11) is formed with a cavity (39) so that the side wall (13) and the driving magnet (15) do not come into contact with each other. The element (17) is loosely inserted into the void (39) to omit the bending of the side wall (13) of the rotor yoke (11).

As described above, in the present invention, the voids (35) and (39) are formed between the inside of the side wall (13) of the rotor yoke (11) and the driving magnet (15) to have a play, and thus the hall element (17). ) May be inserted from the circuit board (3) side.

[0027]

[Effect of the device]

 As described above, according to the present invention, a space is formed between the inner side wall of the rotor yoke and the drive magnet, and the position detecting element for detecting the rotational position of the drive magnet is loosely inserted from this side of the circuit board into the space. It is not necessary to provide a gap in the height direction between the magnetic core around which the drive coil that rotates the rotor yoke is wound and the circuit board, and it is possible to reduce the distance between the circuit board and the magnetic core. The brushless motor can be easily made thinner.

Further, since the position detecting element can be operated in a region where the driving magnet has a high magnetic flux density, it is possible to obtain a stable position detecting signal having a good S / N ratio.

[Brief description of drawings]

FIG. 1 is a half sectional view showing an embodiment of a brushless motor of the present invention.

FIG. 2 is an enlarged sectional view showing a main part of the brushless motor of the present invention.

FIG. 3 is an enlarged cross-sectional view showing a main part of another embodiment of the present invention.

FIG. 4 is a half sectional view schematically showing a conventional brushless motor.

[Explanation of symbols]

 (1) Bearing housing (2) (21) Bearing (ball bearing) (3) Circuit board (4) (27) Shaft (5) Magnetic core (7) Salient pole tooth (9) Drive coil (10) (29) Bushing (11) Rotor yoke (13) Side wall (15) Drive magnet (17) Position detecting element (Hall element) (25) Frequency generating coil (31) Open end (33) Bending step (35) (39) Vacancy

Claims (1)

[Scope of utility model registration request] 1. A circuit board supported by a stator member, a cup-shaped rotor yoke rotatably supported by the stator member, and a drive disposed inside a side wall of the rotor yoke so as to face the circuit board. A brushless motor comprising a magnet and a position detecting element arranged on the circuit board for detecting a magnetic pole position of the driving magnet, wherein the position detecting element is formed between an inner side wall of the rotor yoke and the driving magnet. A brushless motor, wherein the brushless motor is loosely inserted from the side of the circuit board into the opened space.