JPH0445423Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a frequency generator mounted on a brushless motor.

[Technical background of the invention and its problems] Brushless motors, such as cylinder motors for video tape recorders, require highly accurate speed control.
Constant speed control is performed by detecting the deviation from the rated speed and providing feedback.
The specific configuration of this frequency generator is conventionally,
A frequency power generation magnet magnetized with multiple poles in the circumferential direction is provided on the rotor of the motor, and an insulated substrate on which a frequency power generation coil is formed in an annular region corresponding to the frequency power generation magnet is provided on the stator side. The configuration was such that a frequency signal with a frequency corresponding to the speed of the rotor was obtained from the generator coil. However, since the motor itself generates electrostatic or electromagnetic noise, there is a problem in that the noise is induced in the frequency generator coil of the frequency generator, distorting the frequency signal and reducing the accuracy of speed control.

Therefore, in recent years, by forming a cancel loop along the frequency power generation coil and connecting it in series in the opposite direction to the frequency power generation coil, the noise component induced in the frequency power generation coil is reduced by the negative phase component induced in the cancellation loop. A configuration that cancels out noise using noise components has been considered. However, even with this method, the noise components induced in the frequency generator coil and the noise components induced in the cancel loop do not completely become out of phase, so a slight distortion remains in the frequency signal, impairing the accuracy of speed control. There is still a problem that it cannot be improved sufficiently.

[Purpose of the invention] Therefore, an object of the present invention is to provide a frequency generator that can obtain highly accurate frequency signals by improving noise resistance.

[Summary of the invention] The invention provides a frequency power generation magnet that is circumferentially magnetized with multiple poles on the rotor of a brushless motor, and a frequency power generation coil is formed in a predetermined annular region facing the frequency power generation magnet. In a frequency generator in which an insulating substrate is attached to a frame made of a conductive material of the brushless motor, a cancel loop insulated from the frequency generating coil is formed on the insulating substrate along the frequency generating coil, and this cancel loop is formed on the insulating substrate along the frequency generating coil. A ring-shaped conductor is connected in series to the frequency power generation coil in a reverse direction, and an annular conductor is formed on the insulating substrate at least on the inner or outer side of the frequency power generation coil and the cancel loop, and the ring-shaped conductor is electrically connected to the frame. The feature is that the absolute amount of noise components induced in the frequency power generation coil is reduced by setting the frequency generation coil to the above state.

[Example of the invention] Figures 1 to 3 below show an example in which the invention is applied to a cylinder motor of a video tape recorder.
This will be explained with reference to the figures.

Reference numeral 1 denotes a frame made of a conductive material such as aluminum die-casting, and includes an upper cylinder 2 and a lower cylinder 3. A bearing sleeve 3a is integrally provided approximately at the center of the lower cylinder 3 so as to protrude vertically, and a rotating shaft 5 is supported therein via a bearing 4. A rotating disk 7 having a video head 6 is fixed to the upper end of the rotating shaft 5, and a rotor 8 is fixed to the lower end. The rotor 8 is constructed by fixing a rotor yoke 9 to the rotating shaft 5, and fixing to the rotor yoke 9 a field magnet 10 and a frequency power generation magnet 11, both of which are annular. The frequency power generation magnet 11 is magnetized with, for example, 120 poles so that the poles are alternately different in the circumferential direction. on the other hand,
The stator 12 is made up of a plurality of armature coils 14 attached to an annular stator core 13.
3 is fitted into the lower end of the bearing sleeve 3a and placed within the field magnet 10 of the rotor 8. Now, 15 is an insulating board formed of, for example, a glass epoxy plate, and this has a mounting opening 15a having an inner diameter approximately equal to the outer diameter of the bearing sleeve 3a.
6 and is fixed to the lower surface of the lower cylinder 3 together with the stator 12 in a fitted state to the bearing sleeve 3a. As shown in FIG. 1, in an annular region of the lower surface of the insulating substrate 15 near the outer periphery facing the frequency power generation magnet 11 of the rotor 8, there is a frequency power generation coil shaped like a continuous rectangular wave. 17 is formed by, for example, printed wiring means, and constitutes a frequency generator together with the frequency power generation magnet 11. On the other hand, the anti-frequency power generation coil 17 of the insulating substrate 8
On the side surface (top surface in FIG. 2), a ring-shaped cancel loop 1 is also connected by printed wiring means along the radially intermediate portion of the frequency generating coil 17.
8 (see FIG. 3), which is connected to the frequency generating coil 17 through a through hole (not shown).
are connected in series in opposite directions. Further, as shown in FIG. 1, on the surface (lower surface) of the insulating substrate 15 facing the frequency power generation coil 17, a ring-shaped conductor 19 is formed along the inner peripheral edge of the mounting opening 15a by printed wiring means. The inner peripheral edge of this annular conductor 19 is exposed at the inner peripheral edge of the attachment port 15a. Therefore, when the insulating substrate 15 is attached to the frame 1, the inner peripheral edge of the annular conductor 19 is in contact with the bearing sleeve 3a, and the annular conductor 19 is electrically connected to the frame 1. still,
Although not shown, a wiring pattern for configuring a drive circuit is formed on the insulating substrate 15 by printed wiring means, and a Hall element 20 for detecting the rotational position of the rotor 8 and various electronic components are mounted on the insulating substrate 15. A drive circuit is mounted that sequentially transmits communication to the armature coil 14 according to the rotational position of the rotor 8 and controls the speed of the rotor 8 based on a frequency signal from the frequency generating coil 17. Further, in FIG. 3, 21 is a spacer provided between the insulating substrate 15 and the stator core 13.

In the above configuration, if electrostatic or electromagnetic noise occurs due to switching of the armature coil 14, for example, the frequency generator coil 17 of the frequency generator
Noise voltage is induced in the However, a similar noise voltage also occurs in the cancel loop 18 provided along the frequency power generation coil 17. Since the cancel loop 18 is connected in series with the frequency generating coil 17 in the opposite direction,
The noise voltage generated in the frequency power generation coil 17 and the noise voltage generated in the cancel loop 18 are as follows.
They have substantially opposite phases and cancel each other out. Therefore, the noise component of the frequency signal from the frequency power generation coil 17 is reduced.

Moreover, the insulating substrate 15 has a ring-shaped conductor 1 on the inner circumferential side.
9 is formed and electrically connected to the frame 1. Since the frame 1 is normally grounded, the potential of the annular conductor 19 becomes the ground potential, and the electric flux due to electrostatic noise flows toward the annular conductor 19 rather than the frequency generating coil 17 and the cancel loop 18. For this reason, the frequency power generation coil 1
7 and the cancel loop 18 are present, and the voltage induced in the frequency generating coil 17 and the cancel loop 18 due to electrostatic noise is reduced. Furthermore, when magnetic flux due to electromagnetic noise interlinks with the annular conductor 19, an eddy current flows through the annular conductor 19 in a direction that cancels out the magnetic flux. As a result, the magnetic flux interlinking with the frequency generating coil 17 and the cancel loop 18 decreases, and the voltage induced in the frequency generating coil 17 and the cancel loop 18 due to electromagnetic noise decreases.

In this way, the frequency generating coil 17 and the cancel loop 18 are both electrostatically and electromagnetically shielded by the annular conductor 19, and the noise voltage induced in the frequency generating coil 17 and the cancel loop 18, respectively, is shielded from the annular conductor 19. 19 is significantly reduced compared to those without. Therefore, the noise voltage induced in the frequency power generation coil 17 and the cancel loop 18 is not completely out of phase, and the noise voltage induced in the frequency power generation coil 17 cannot be completely canceled by the cancel loop 18 alone. Even if there are various circumstances that make it impossible, the frequency generator coil 17
Since the absolute amount of noise voltage induced in the frequency generating coil 17 can be reduced, the distortion of the frequency signal from the frequency generating coil 17 can be sufficiently reduced.
As a result, the accuracy of speed control of the rotor 8 can be greatly improved.

In the above embodiment, the annular conductor 19 is formed on the inner circumferential side of the frequency generating coil 17, but the present invention is not limited to this, and as shown in FIG.
9 may be provided on the outer peripheral side of the frequency power generation coil 17. In this case, the annular conductor 19 is formed on the outermost periphery of the insulating substrate 15 so that the outer periphery of the annular conductor 19 is exposed at the outer periphery of the insulating substrate 15. By forming an annular protrusion 22 on the lower surface of the lower cylinder 3 in contact with the outer periphery of the insulating substrate 15, the annular conductor 19 can be easily and reliably connected to the frame 1.

In addition, the present invention is not limited to the embodiments described above and shown in the drawings, and may be implemented with various modifications within the scope of the invention, such as not being limited to a frequency generator for a cylinder motor of a video tape recorder. It is something that can be done.

[Effects of the invention] As described above, the present invention can cancel the noise induced in the frequency generation coil by the cancel loop, and reduce the absolute amount of noise voltage induced in the frequency generation coil by the annular conductor. As a result, distortion of the frequency signal from the frequency power generation coil can be significantly reduced, which is an excellent effect.

[Brief explanation of the drawing]

1 to 3 show an embodiment of the present invention,
1 is a plan view of the insulating substrate shown together with the frequency generating coil and the annular conductor, FIG. 2 is a vertical cross-sectional view, FIG. 3 is shown together with the cancel loop, and FIG. 1 is a plan view of the insulating substrate shown together with the frequency generating coil and the annular conductor. 2 is a longitudinal sectional view of the whole, FIG. 3 is a perspective view of the insulating substrate together with the cancel loop, and FIGS. 4 and 5 correspond to FIGS. 1 and 2 showing different embodiments of the present invention. It is a diagram. In the drawing, 1 is a frame, 8 is a rotor, 11 is a frequency power generation magnet, 12 is a stator, 15 is an insulating substrate, 17 is a frequency power generation coil, 18 is a cancel loop, and 19 is an annular conductor.

Claims (1)

[Scope of utility model registration request] A frequency power generation magnet magnetized with multiple poles in the circumferential direction is provided on the rotor of the brushless motor, and an insulating substrate on which a frequency power generation coil is formed in a predetermined annular region facing the frequency power generation magnet is used as a conductive material of the brushless motor. A cancel loop insulated from the frequency generating coil is formed on the insulating substrate along the frequency generating coil, and this cancel loop is connected in series to the frequency generating coil in an opposite direction. and a frequency generator, characterized in that an annular conductor is formed on the insulating substrate at least on the inner or outer periphery side of the frequency generating coil and the cancel loop, and the annular conductor is electrically connected to the frame. .