JPH0511533Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a rotating polygonal mirror type optical deflector used for optical scanning of laser beam printers, etc.

(Prior Art) In a conventional rotating polygonal mirror type optical deflector of this type, as shown in FIG. A motor drive magnet 2 is installed in the rotational speed signal generator, which is composed of a FG pattern).
In order to prevent excess leakage magnetic flux (noise) from the main magnet (hereinafter referred to as the main magnet) from entering and having a negative effect on the wow and flutter of the motor, the FG magnet 3 should be placed far away from the main magnet 2 in the radial direction, or As shown in FIG. 8, the FG magnet 3 is covered with a magnetic shield ring 8 or the like to block excess magnetic flux from the main magnet 2 and reduce output errors in the rotational speed signal. In the figure, reference numeral 1 is a rotating polygon mirror, 4 is a rotor case, 5 is a printed circuit board, and 7 is an armature coil group.

(Problems to be Solved by the Invention) The conventional techniques described above have the following problems.

(1) Since the FG magnets are placed far away from the main magnet in the radial direction, it is difficult to downsize the motor, and the moment of inertia of the rotor becomes larger than necessary, making it difficult to start the motor. It took a long time and was inefficient.

(2) Also, if the diameter of the main magnet is designed to be small,
The output of the electric motor was also reduced, the degree of freedom in design was not obtained, and it was difficult to accommodate a wide range of rotational speeds of the electric motor itself.

(3) To shield magnetic flux from the main magnet
Providing a shield ring or the like on an FG magnet increases unbalance during rotation, which increases the likelihood of vibration and noise, and increases the number of parts, making assembly complicated and causing high costs.

The present invention aims to solve the above-mentioned problems.

(Means for solving the problem) In order to achieve the above object, in the present invention,
Provide the following means:

(1) Match the rotational direction magnetization phases of the main magnet and FG magnet in accordance with the specified rotational direction of the motor rotor so that the error in the rotational speed output signal is minimized.

(2) When the rotation direction of the motor rotor is reversed, the mutual magnetization phases are reversed.

(3) The main magnet and the FG magnet are integrally formed using a plastic magnet or the like.

(Function) The function of the above-mentioned configuration will be explained with reference to FIGS. 1 to 6.

As shown in Fig. 1, the main magnet part 2a and the FG
By energizing the armature coil group 7, a rotor magnet 9 in which the magnet portion 3a is integrally formed with a plastic magnet is axially opposed to the armature coil group 7 and rotatably supported by the rotation axis R. , the rotor magnet 9 rotates in a predetermined direction and axially faces the FG magnet part 3a, and a comb-like rotational speed signal output pattern 6 (hereinafter referred to as FG pattern) is disposed on the printed circuit board 5. When the rotor magnet 9 rotates counterclockwise as viewed from the rotating polygon mirror 1, the main magnet portion 2a and the FG magnet shown in FIG. The arrangement of part 3a is
It is most preferable to set the magnetization phase to 2b and 3b shown in FIG. 5. When the rotor magnet 9 is rotated in this magnetization phase state, the FG Pattern 6 outputs a signal. In the figure, 2b is the already explained main magnet part magnetization phase, and 3b is the FG magnet part magnetization phase. 10 is the FG pattern output by the main magnet, 11 is
FG pattern output by FG magnet, 12 shows composite FG output.

In this case, it is clear that the time error of the waveform of the composite FG output 12 is minimum, that is, T _X = T _Y.
By minimizing this error, it becomes possible to stabilize rotational fluctuations (wow and flutter) of the electric motor.

However, the output waveform when the mutual phases of the magnets are reversed without changing the direction of rotation is as shown in FIG. 4.

In this state, the time error in the waveform of the composite FG output 12 is the largest, and the rotational fluctuations of the motor become worse.

As is clear from the above explanation, it is necessary to carefully determine the magnetization phase of the main magnet and FG magnet according to the rotational direction of the motor rotor.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 1 to 6.

In FIG. 1, a rotor magnet 9 in which a main magnet part 2a and an FG magnet part 3a are integrated with a plastic magnet or the like is axially opposed to an armature coil group 7, and is rotatably connected to a rotating part R.
The rotor magnet 9 rotates in a predetermined direction together with the rotating polygon mirror 1 attached to the rotating part R by supporting the armature coil group 7 and energizing the armature coil group 7.
In a comb-shaped rotational speed signal output pattern 6 (hereinafter referred to as FG pattern) arranged on the printed circuit board 5 and facing the FG magnet part 3a in the axial direction,
Generates a speed signal.

When the motor rotor magnet 9 rotates counterclockwise as viewed from the rotating polygon mirror 1, the magnetization phase of the main magnet section 2a and the FG magnet section 3a shown in FIG. 3 is changed to the magnetization phase 2b shown in FIG. 5. , 3b, the output waveform induced by the FG pattern 6 is
As shown in FIG. 5, T _X =T _Y , that is, the time error of the falling edge and zero cross point of the waveform of the composite FG output 12 is minimized.

This shows that even if excess leakage (noise) from the main magnet 2 enters the FG pattern 6, it hardly affects the time error of the output waveform.

Therefore, the error in the rotational speed signal becomes extremely small.
It is clear that the speed control system can also easily detect true rotational speed variations, and therefore the wow and flutter of the motor can be kept low.

Incidentally, although the rotation direction is counterclockwise as mentioned above, the respective magnetization phases 2b and 3b of the main magnet part 2a and FG magnet part 3a in FIG. 2 are as shown in FIG. Considering the case of inversion, the output waveform of FG pattern 6 is
Formed as shown in FIG. 4, the time error of the waveform of the composite FG output 12 is maximum, and has the most adverse effect on the wow and flutter of the motor.

Therefore, depending on the rotational direction of the motor rotor magnet 9 and whether the rising zero-crossing point or falling zero-crossing point of the waveform of the composite FG output 12 is adopted, the main magnet part 2a and the FG
It is necessary to carefully determine the mutual phase relationship of magnetization of the magnet portions 3a.

(Effects of the invention) As detailed above, according to the present invention, the following effects can be expected.

(1) Even if excess leakage magnetic flux (noise) from the main magnet enters the FG pattern, it is hardly affected, so the main magnet and FG magnet can be placed close together, making the motor more compact. It is also possible to measure efficiency improvements.

(2) By inverting the phases of the main magnet and the FG magnet according to the rotational direction of the rotor, it is possible to handle either rotational direction.

(3) Due to the reason mentioned in (1) above, the main magnet and the FG magnet can be integrally formed as a plastic magnet, which makes it easy to assemble and enables a significant cost reduction.

[Brief explanation of the drawing]

Figures 1 to 6 show embodiments of the present invention;
The figure is a sectional view of the optical deflector according to the present invention, and FIGS. 2 and 3 are surface views showing the magnetized states of the main magnet section and the FG magnet section at the A=A' section in FIG. 4 and 5 are output waveform diagrams of the FG pattern due to the difference in magnetization phase, and FIG. 6 is a perspective view of the FG magnet and the FG pattern. FIGS. 7 and 8 are cross-sectional views of conventional optical deflectors, respectively. 1... Rotating polygon mirror, 2... Main magnet, 3...
FG magnet, 4... Rotor case, 5... Printed circuit board, 6... FG pattern, 7... Armature coil group, 9... Rotor magnet, 10... FG pattern output by main magnet, 11...
FG pattern output by FG magnet, 12...
Synthetic FG output, 2a... Main magnet section, 2b...
Main magnet part magnetization phase, 3a...FG magnet part, 3
b...FG magnet part magnetization phase.

Claims (1)

[Claims for Utility Model Registration] 1. The motor driving magnet used for the rotation speed output signal in the constant speed rotation control system of the rotating polygonal mirror type optical deflector has a P pole (P is a positive integer of 2 or more); When the rotation speed signal output magnet is P pole or 2P pole, the rotation speed is adjusted between the motor drive magnet (main magnet) and the rotation speed according to the rotation direction of the motor rotor so that the time error of the rotation speed output signal is minimized. An optical deflector characterized in that the magnetization phases of the signal output magnets (FG magnets) in the rotation direction are matched. 2. The optical deflector according to claim 1, wherein the mutual magnetization phases of the main magnet and the FG magnet are reversed according to the rotational direction of the motor rotor. 3. The optical deflector according to claim 1, wherein the main magnet and the FG magnet are each formed integrally with a plastic magnet.