JPS6051448A - Face-to-face type brushless dc motor - Google Patents

Abstract

PURPOSE:To reduce the size and weight of the entire motor and to accurately detect the rotating position of a pole by opening a recess at a stator core except a portion corresponding to a rotary force generating portion of a stator coil, and containing a Hall element in the recess. CONSTITUTION:A rotor assembly and a stator assembly are oppositely arranged, and N-poles and S-poles for forming a rotor magnet are alternately arranged in the rotating direction on the opposed surfaces of the rotor assembly. A pluraity of stator coils 10 corresponding to the rotor magnet are provided in the rotating direction on the opposed surfaces of a stator core 9 in the stator assembly, and recesses 9a-9f are opened at the portions of the core 9 corresponding to the non rotary force generating portions of the coil 10. Hall elements H1-H3 are respectively contained in the recesses 9f, 9a, 9b opened at an interval of the angle of 60 deg. of the recesses. Thus, the entire motor can be reduced in size and weight, and the rotating positions of the poles can be accurately detected.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to 1) a surface-facing brushless DC motor used as a D motor or the like of a VTR;

A conventional face-to-face type pushless direct current motor will be explained with reference to FIGS. 1 to 7, taking as an example a motor used as a DD motor (direct-coupled motor) for a rotating head cylinder in a VTR. To explain from the rotating head cylinder side,
In the drawing, reference numeral (1) is a lower cylinder, and (2) is an upper cylinder. The lower cylinder (1) is fixed to the VTR main body (not shown) via appropriate members. A main shaft (4) is rotatably supported on the lower cylinder (1) via bearings (3a) and (3b). The upper cylinder (2) is fixed to this main shaft (4), and is constructed as an upper cylinder rotating type. (5a) (5b) is a video head, and (6) is a rotary transformer. The diameter of the above cylinders (1) and (2) is 6 mm for home VTRs, etc.
Although it is about 0 trrmφ or more, for small-sized devices such as 8 mm VTRs, which have been developed in recent years, it is about 40 trrmφ, and the entire rotating head cylinder is becoming smaller and lighter.

Below such a rotating head cylinder, a surface-facing brushless DC motor M for rotational drive is connected to a main shaft (4).
is directly connected to. The surface-facing brushless DC motor M is mainly composed of a disc-shaped stator assembly M1 and a rotor assembly M2, both of which are MI
M2 are arranged opposite to each other.

In this opposed arrangement, the stator assembly 'JMt is fixed to the lower cylinder (1) via the stator mounting plate (force), while the rotor assembly M2 is fixed to the lower cylinder (1) via the bearing stopper (1).
8) to the main shaft (4).

Figures 3 and 4 show each assembly! J Mt This shows the structure of the opposing surface part in Mt.
Stator coils 01 to 0!9 are arranged in series at equal intervals in the rotational direction. On the other hand, in the rotor assemble IJ Mt, N and S magnetic poles constituting the rotor magnet αQ are arranged alternately on the magnet mounting plate (17). The number of magnetic poles in the illustrated example is eight. The magnet mounting plate (17) is made of iron and also has a magnetic shielding function to prevent leakage of magnetic flux from the rotor magnet Oe to the surrounding area.

FIG. 5 shows both assemblies M arranged facing each other as described above.
In I Mt, each of the stator coils 00 to 00 in the stator assembly M1 includes a part that effectively acts on generation of rotational force and a part that does not act, that is, a part that generates rotational force (10a) (Ila)...( 15a) and rotational force non-generating portions (10b) (llb)... (15b).In other words, the rotational force of the rotor assembly M2 is generated by the magnetic field generated by the rotor magnet (10) The interaction between the current flowing through the stator coils 00 to α9, in other words, occurs according to Fleming's left hand rule.
In, the part (10a) in the direction orthogonal to the rotation direction
(lla)...The kinetic force generated in (15a) is directed in the rotational direction, and this acts as a rotational force. On the other hand, the part facing in the same direction as the rotation direction (10b) (llb)...
In (15b), the kinetic force is generated in the radial direction and does not act as a rotational force.

Therefore, it is desirable that the kinetic force directed in the radial direction be as small as possible when considering rotational efficiency and the like.

The symbols in Figures 1 and 2 (II is the FG coil, C1 is the PG magnet, and the wire is a printed board. The printed board wire shows the rotational position of the rotor magnet magnetic pole N% S as the rotor assembly M2 rotates. Figure 6 (A
) fBl Stator coils (11 to 1) as shown in (C)
The Hall element H, % H, which outputs the α field current switching signal el 62 C3 is 30% relative to the axis center of the main shaft (4).
They are arranged at angular intervals of °. As the K VTR becomes smaller in size, both the stator and rotor assemblies MI Mt of the DC motor M attached to the handle become smaller, so Hall elements H, -H, Due to lack of mounting space, the Hall elements H and -H3 are mounted outside the printed board board or the like. Fig. 7 shows that when the number of magnetic poles of the rotor magnet αe is 8 and the number of stator coils (1 to αω is 6) as described above, the currents shown in Fig. 6 (A), (B), and (C) are It is a wiring diagram including a control circuit in the case of three-phase driving with switching signal e1 C2C3. In the figure, Q! to Q6 are switching elements, and C21) is a connection end to a DC power source.

The angular spacing between the three Hall elements H1 to H3 is 30.
It is known that not only in the case of 600.1200 degrees, but also in the case of 600.1200 degrees, it is possible to perform current switching of stator coils OI to α using a signal obtained from this.

On the other hand, the ones shown in Figures 8 to 10 show other conventional examples, in which the VTR itself is very small and the diameter of the rotating head cylinder is 60 to 80 gates. This shows an example of a brushless DC motor that is attached to an object. In this conventional example, three Hall elements H1 to H3 are arranged at angular intervals of 60 degrees, and the diameter of the stator core of the one installed in such a VTR is large, and the diameter of each stator coil is large. (22a) to (22f) also have large dimensions. The stator coil has a relatively large coil stacking thickness and a relatively large center gap size. Therefore, three Hall elements H! ~H, ha,
It is attached to the center of the stator coil (FIG. 8) or the gap between the coils (FIG. 10) without mechanically interfering with other members.

However, in the conventional surface-facing brushless DC motor for equipping small VTRs, etc., the Hall element H
.
7), it was not possible to sufficiently downsize the brushless DC motor as a whole including the Hall element, and there was a problem in that the accuracy of detecting the rotational position of the magnetic pole by the Hall element was reduced.

This invention aims to solve these conventional problems.

The present invention will be explained below based on the drawings.

FIG. 11 to FIG. 13 are diagrams showing an embodiment of the present invention. In each of the figures following FIG. 11, the same or equivalent members or parts as in FIGS. 1 to 5 are designated by the same reference numerals and redundant explanations will be omitted.

First, to explain the configuration, in this embodiment, the rotational force non-generating portion (1ob) (Il
b)...Qsb) Recesses (9a) (9b)...(9f) are bored in portions of the stator core (9) corresponding to Qsb). In the illustrated example, the planar area of the recesses (9a), (9b), ... (9f) is the portion (10b) where no rotational force occurs (1
1t+)...Qsb), and its depth extends to a depth position equal to or more than % of the thickness of the stator core (9). Note that this recess (9a) (9b)...(
The shape of the hole 9f) is not limited to the shape shown in the illustration, but the rotational force generating portion (10a) (lla)...(15
If it is less than a), it can be made into an appropriate shape. Since the stator core (9) is usually manufactured by powder compression (iron-based sintered body) using a mold, the stator core (9) is
) (9b)...(9f) can be formed simultaneously during this molding.

Of the recesses formed in this way, three recesses are bored at angular intervals of 60' ((9f in the example in the figure)).
(9a) In (9b) recess), Hall elements H1~
H3 is stored respectively.

Next, the effect will be explained.

Hall element H! ~H3 is placed in the plane facing the rotor magnet al, at a position where the magnetic flux from each of its magnetic poles N and S reaches directly through the shield plate, so
Note that the rotational position of each magnetic pole can be detected with high sensitivity. Therefore, detection errors do not occur. Further, since the Hall elements H1 to H3 are arranged within the stator assembly Mi, the overall size of the motor M can be reduced.

On the other hand, since the recesses (9a), (9b), ... (9f) formed on the back side of each stator coil αI-(151) are air gaps, these parts are more magnetic than other parts. The resistance is large.For this reason, each recess (9a
) (9b)...(9f) The rotor magnet near the perforated part) (The magnetic flux from lf19 is
(9b)...(9f), that is, the rotational force generating portions (10a) (lla)...(15a) are biased, and the rotational force non-generating portions (1ob) (ttb)...( 15b
) decreases. Therefore, the kinetic force generated in the rotational direction by each stator coil (IGK) becomes larger, and the radial kinetic force that does not act as a rotational force decreases. Both phenomena act more effectively than increasing the rotational efficiency. do.

Furthermore, due to an error in the winding shape of the stator coil, there is a tendency for the stator coil to generate a kinetic force in the rotational direction even in a portion where no rotational force is generated. However, in this portion where no rotational force is generated, the magnetic flux density is reduced as described above, so the rotational force caused by the winding shape error is suppressed to a minimum. Therefore, all stator coils are 0
Even if some of the coils 1 to αQ have a winding shape error as described above, the tendency of the rotational force to become unstable due to this error is eliminated. Furthermore, each recess (9a) (9b)...(
9f) contributes to reducing the weight of the DC motor M.

Next, FIG. 14 shows another embodiment of the present invention.

In this embodiment, the recesses (9a) (9b) in FIG.
In addition to (9f), at each intermediate portion of these recesses, and at the portion (10a) where the stator coil generates the rotational force (
Concave portions (k) (9h)...(
9t) is drilled. In the example shown in the figure, the entire concave portion (9a) (
9b) -(9f), (9g) (9h)...(9t)
The respective arrangement angular intervals are defined as 30°. In this example, as shown in the figure, (9t) (9a) (9g)
A Hall element H1"Hg is housed in each of the three recesses, and the angular interval between these Hall elements H3 is also 30.
° is specified.

To explain the effect, in the embodiment of , the recess (9a)
(cab) - (9t), (9g) (9h) - (9
Since the number of motors 7) is larger than that of the above embodiment, the motor M
Further weight reduction is achieved. Other functions such as highly sensitive detection of the rotational position of each magnetic pole and increase in rotational efficiency are substantially the same as those of the first embodiment.

In each of the above-mentioned embodiments, a case was described in which the surface-facing brushless DC motor according to Jin's invention was applied as a DD motor of a VTR, but the DC motor according to the present invention is not limited to such applications, but can also be used as a capstan motor or , it can also be applied as a motor in other equipment.

As detailed above, according to the present invention, four parts are bored in the stator core part other than the part corresponding to the part where the rotational force of the stator coil is generated, and the Hall element is housed in the recessed part, so that the entire motor is small and lightweight. In addition, even when the entire motor is downsized, the rotational position of the rotor magnet magnetic poles can be detected with high sensitivity. In addition, a concave portion is provided in the stator core portion corresponding to the portion where no rotational force is generated in the stator coil, and this portion has a large magnetic resistance. The force in the direction can be reduced, and rotational efficiency can be improved. Further, even if there is a winding shape error in a portion of each stator coil where no rotational force occurs, instability in rotation caused by this can be eliminated.

[Brief explanation of drawings]

Figures 1 to 2 show a VTR rotating head cylinder to which a conventional surface-facing brushless DC motor is applied. Figure 1 is a half-sectional side view, Figure 2 is a bottom view, and Figures 3 to 7. The figure shows the face-to-face type brushless DC motor shown in Fig. 1, Fig. 3 is a plan view of the facing part of the stator assembly, and Fig. 4 is a plan view of the opposing part of the stator assembly.
The figure is a plan view of the opposing portion of the rotor assembly, FIG. 5 is a plan view for explaining the rotational force generating portion of each stator coil in the stator 7 assembly, and
(C) is a waveform diagram showing the output signal of the Hall element, Figure 7 is a wiring diagram of the stator coil, etc., Figures 8 to 10 are other conventional examples, and Figure 8 is a diagram of the stator assembly. Opposed partial plan view, FIG. 9 is a partial cross-sectional view taken along the line X-X in FIG. 8,
FIG. 10 is a plan view of opposing parts of the stator assembly showing a different mounting manner of the Hall element from FIG. 8, and FIGS. 11 to 13 show an embodiment of the surface-facing brushless DC motor according to the present invention. FIG. 11 is a plan view of the opposing portion of the stator core, and FIG. 12 is a side view of the same stator core.
FIG. 13 is a partially enlarged side view showing a state in which the Hall element is accommodated in the recess, and FIG. 14 is a plan view of a portion of the stator core facing each other, showing another embodiment of the present invention. 4: Main shaft 7: Stator mounting plate 9: Stator core 9a to 9t: Recesses 10 to 15; Stator coils 10a to 15a: Rotational force generating portions 10b to 15b = Rotational force non-generating portion 16: Rotor magnet 17: Magnet mounting plate Hl-yH37 Hall element M: Surface-facing brushless DC motor Ml = Stator assembly M2: Rotor assembly Clarion Co., Ltd. agent Ashi 1) Naoe 1st section Figure 2 Figure 3 Figure 3 Figure 4 Figure 6 Figure 7 1 8N m = Figure 11 Figure 12

Claims (1)

[Claims] A rotor assembly and a stator assembly are disposed opposite to each other, N and S magnetic poles constituting a rotor magnet are arranged alternately in the rotational direction on the opposing surfaces of the rotor assembly, and the stator cores of the stator assembly are arranged opposite to each other. A plurality of stator coils corresponding to the rotor magnets are arranged in series in the rotational direction on the surface, and a Hall element is further provided for detecting the rotational position of the magnetic pole and outputting a signal for switching the current of the stator coil. A brushless direct current motor, characterized in that four parts are bored in the stator core part other than the part corresponding to the rotational force generating part of the stator coil, and the Hall element is housed in the recessed part. Brushless DC motor.