JPH0757084B2 - Drum motor - Google Patents

Description

The present invention relates to a VTR drum motor, and more particularly to a brushless motor suitable for reducing a specific frequency component included in an FG signal.

[Conventional technology]

As an FG (Frequency Generator) method of a drum motor, for example, as shown in Japanese Utility Model Laid-Open No. Sho 60-93486, a drive magnet is held on the inner diameter side of a case, and a rotor holding the FG magnet on the end face, and the FG magnet. There is a method of obtaining with a zigzag-shaped copper foil pattern of a printed circuit board which is installed so as to face. However, even though the configuration was explained, no consideration was given to performance such as uneven rotation or FG accuracy.

Normally, the VTR drum motor is used at a high rotation speed of 1800 rpm, and it drives the upper drum, which has a larger inertia than the rotor of the motor itself, so its rotation unevenness is almost FG.
It can be said that it is decided with accuracy. Therefore, in order to improve the uneven rotation, it is necessary to realize a highly accurate FG.

For this FG accuracy, the rotor side has a runout of the FG magnet,
A number of factors are influencing each other intricately, such as misalignment, multi-pole magnetized pitch unevenness, magnetic field unevenness, misalignment of zigzag copper foil pattern on the stator side, pitch unevenness, surface deviation of the insulating substrate that holds the pattern. , It is difficult to improve FG accuracy.

[Problems to be solved by the invention]

However, the above-mentioned prior art does not consider the axial leakage magnetic field of the drive magnet. That is, the axial leakage magnetic field of the drive magnet that reaches the FG magnet from the rotor case is superposed on the magnetic field of the FG magnet, and the distorted magnetic field generates power in a zigzag pattern.
The signal contains the frequency component from the drive magnet,
There was a problem that the rotation irregularity of the motor was made worse.

An object of the present invention is to reduce the frequency component due to the drive magnet included in the FG signal.

[Means for solving problems]

The above object is achieved by satisfying the relation of [zigzag-shaped copper foil pattern outer diameter on insulating substrate] ≤ [rotor case inner diameter] for generating a magnetic field change of the FG magnet as an FG signal.

[Action]

That is, since the outer diameter of the zigzag copper foil pattern that generates the magnetic field change of the FG magnet as a frequency signal is set to be smaller than the inner diameter of the rotor case, the magnetic field on the pattern is less distorted by the drive magnet. Also, the generated FG signal has few frequency components due to the drive magnet, and the uneven rotation of the motor can be improved.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS.
In the figure, reference numeral 1 is a rotary drum, on which a video head 2 is mounted and fixed to a rotary support 4 about a rotary shaft 3.
A fixed drum 5 has an upper bearing 6A and a lower bearing 6B that support the rotating shaft 3 mounted in the inner diameter portion. Reference numeral 7 is a stator of a motor. A core 8 obtained by punching and laminating magnetic materials is fixed with a rivet 9 and the surface of the core 8 is insulated (not shown), and then insulated with a coil 10 around which a conductor such as a magnet wire is wound. Board 11A
An insulating substrate 11 having a copper foil 11B set in a zigzag shape and a cover 12 for protecting these components. 13 is the stator 7
Is a screw for attaching to the fixed drum 5. Reference numeral 14 denotes a motor rotor, which is composed of a cylindrical case 15 made of a magnetic material, a drive magnet portion 16A radially magnetized with a plurality of poles, and an FG magnet portion 16B magnetized with a large number of poles in the axial direction. Attach the magnet 16 such as a switch molded product.

In the drum motor having the above-described structure, the laminated core 8, the drive magnet portion 16A, the magnetic circuit including the case 15, the rotor position detection element (not shown), and the drive electric circuit generate a rotational torque to generate a zigzag pattern. Copper foil 11B
An FG signal is generated between the insulating substrate 11 having the and the FG magnet portion 16B.

The principle of rotation of the drum motor configured as described in this section is already known and is not directly related to the description of the text, and therefore its description is omitted.

In the drum motor configured as described above, the insulating substrate 11
The outer diameter side D of the upper zigzag copper foil pattern 11B and the rotor 1
The case 15 is manufactured by setting the relationship of the inner diameter E of the case 15 such that D ≦ E. Then, the FG magnet section 16B is generated by the axial leakage magnetic field G of the drive magnet section 16A magnetized to have a plurality of poles.
Since the distorted magnetic field distribution of does not act on the zigzag copper foil pattern 11B, the frequency / component due to the distorted magnetic field distribution is not generated.

Therefore, the frequency component due to the axial leakage magnetic field of the drive magnet 16A is reduced, so that the drum motor with less uneven rotation can be obtained.

In addition, the cancellation pattern in the conventional insulating substrate is
As shown in FIG. 2, a folded copper foil pattern H is formed on the outer diameter side of the zigzag-shaped copper foil pattern 11B with a diameter I of
It is set to be larger than the outer diameter F of the case 15. Therefore, the canceling effect of the folded copper foil pattern H is small because it is performed only by the leakage magnetic field.

However, in the present invention, the diameter I of the folded copper foil pattern H is
Can be set between the inner diameter E and the outer diameter F of the case 15,
Since it is performed in a strong magnetic field, there is an advantage that the canceling effect becomes large.

[Advantages of the Invention] According to the present invention, the outer diameter of the zigzag copper foil pattern for FG signal generation is set to be smaller than the inner diameter of the case of the rotor. Since it is set between the diameters, the generation of frequency components due to the axial leakage magnetic field of the drive magnet is suppressed, and a highly accurate FG with a large canceling effect can be realized, and a drum motor with less uneven rotation can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part of a rotary magnetic drum showing an embodiment of the present invention, and FIG. 2 is a front view showing a copper foil pattern state of an insulating substrate. 1 ... Rotating drum, 5 ... Fixed drum, 7 ... Stator, 11 ... Insulating substrate, 14 ... Rotor, 15 ... Case, 16 ... Magnet.

Claims (1)

[Claims] 1. A rotor integrally supported by a case with a magnet including a drive magnet portion magnetized with a plurality of poles and a rotational speed detecting FG magnet portion magnetized with a large number of poles, and the magnet facing the drive magnet portion. And a coil in which a conductor is wound by insulating the laminated core arranged by
A drum motor provided with a stator, which is arranged opposite to an FG magnet portion and is provided with a copper foil pattern for generating a magnetic field change of the FG magnet portion due to rotation of a rotor as a frequency signal. The pattern comprises a zigzag-shaped copper foil pattern portion that is substantially rounded once and is smaller than the inner diameter of the case, and an arc-shaped pattern portion that is folded back around the outer diameter side of the zigzag-shaped copper foil pattern portion and is substantially rounded. A drum motor, wherein an arc-shaped pattern portion is set on the substrate facing between an inner diameter and an outer diameter of the case.