JPH0371689B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The invention of this application relates to a polygon mirror driving device. In particular, the present invention relates to a drive device equipped with a small flat brushless motor that enables stable and smooth rotation of a polygon mirror.

The motors conventionally employed for driving polygon mirrors are ordinary synchronous motors, hysteresis motors, etc., and the configuration of the device is as shown in the attached FIG. 1.

The polygon mirror a is attached to the tower mounting hub e fixed to the rotating shaft c of the drive motor, and the polygon mirror a is attached to the housing b.
A stator d having a predetermined winding f is housed therein, and the rotating shaft c is rotatably held by bearings h and h' fitted into a bracket g of the housing b, and a rotor is mounted on the outer periphery of the stator d. Wear i. j is the cover of polygon Mira.

This type of motor has the drawback that the hub e is fitted and fixed to the rotating shaft of the completed drive motor afterwards, and the polygon mirror is attached to this, resulting in a vertically long structure. Also, since there is an error in assembling the polygon mirror, it is difficult to achieve accurate tilting of the polygon mirror reflective surface with respect to the rotation center axis. Therefore, there are defects such as the laser beam reflected on the reflective surface of the polygon mirror not being scanned at an accurate predetermined speed, and furthermore, since the entire structure of the polygon mirror drive device is formed long in the vertical direction, rotation is difficult. There is a risk that the rotating shaft on which the polygon mirror is attached at the end may tilt during driving, resulting in drawbacks such as the inability of the laser beam to be incident on or reflected on the mirror surface at an accurate position.

Therefore, the present invention has been devised to overcome these drawbacks, by making the polygon mirror drive device extremely small and thin, and by improving the motor mounting mechanism, it is intended to rotate the polygon mirror evenly. .

An embodiment of the present invention will be described below with reference to the accompanying drawings.

In FIG. 2, the polygon mirror 1 forms a cylindrical body with a U-shaped cross section that opens downward, and has one end side surface on the outer wall of a cylindrical hub 2 having a protruding arm 2', and a lower surface thereof on the outer wall of a cylindrical hub 2 having a protruding arm 2'. It is fixed horizontally so as not to move and perpendicularly to the shaft 10, which will be described later.
5 to the hub 2, and also to the upper balancer 11 fixed to the hub 2 using screws 27.

A pair of cylindrical shaft support shafts 3 having a substantially L-shaped cross section are fitted and erected inside the cylindrical hub 2, and a shaft 10 is housed in the center thereof in the vertical direction. Shaft 1
The upper part of the hub 2 is inserted into and fixed to the upper surface of the hub 2, and a pair of ball bearings 18 and 19 are fitted between the shaft 10 and the support shaft 3. Therefore, shaft 1
0 is supported by a shaft support shaft 3 and a pair of ball bearings 18, 19, and includes a hub 2, a polygon mirror 1, an upper rotor plate 4, a lower rotor plate 20, and a pair of rotor magnets 5, which will be described later.
5' It is configured to be rotatable in the cavity formed by the upper case 9 and the lower case 8 together with the FG magnet 22 (hereinafter referred to as a rotating member). Reference numeral 17 is a retaining ring provided on the shaft 10, 16 is a C-ring, and 23 and 24 are O-rings fitted between the shaft shaft 3 and ball bearings 18 and 19. On the side surface of the hub 2 and the lower surface of its protruding arm 2',
The upper rotor plate 4 provided with the bent portion is fixed.
A lower rotor plate 20 is fixed to the upper surface of a lower balancer 12 fixed to the outside of the hub 2 at a lower position symmetrical to this plate.

A rotor magnet 5 is fixed to the lower surface of the upper rotor plate 4, and a lower rotor magnet 5' is fixed to the upper surface of the lower rotor plate 20, respectively. so as to face the lower rotor magnet 5' with a gap in between,
A winding coil group 6 is arranged on the lower surface of a substrate 7 fixedly supported by a curved arm 8' of a lower case 8. Further, an FG coil (not shown) is printed and wired at a position facing the FG magnet 22 on the substrate 7. The board 7 is fixed to the lower case 8 with screws 26 and spacers 33 so as not to move. Also, one end of the upper case 9 has a screw 2.
5, it is fixed to the lower case 8 so as not to move. The Hall element 29 is housed in the winding coil group 6. Reference numeral 22 designates an FG magnet (frequency energizer magnet) attached to the bent end of the upper rotor plate 4.

A lead wire 31 is inserted into the insulating plate 30 and connected to the board 7, and is connected to the connector 32. 2
8 and 28' are fixing screws provided on the upper balancer 11 and the lower balancer 12, respectively.

Next, the winding coil group 6 will be explained with reference to FIG. 3 of the accompanying drawings. The winding coil group 6 consists of a total of six air-core coils 6a, 6b, 6c, 6d, 6e, and 6f provided on the lower surface of the substrate 7, one at each 60° angle, and three Hall elements 21a are installed at appropriate positions. ,21
b, 21c are arranged.

Note that FIG. 4 of the accompanying drawings shows another embodiment of the present invention. In this embodiment, in order to further reduce the size and flatness of the polygon mirror mounting mechanism, an air-core winding coil 6 is disposed between the lower base 34 and the substrate 7 to maintain a gap with one rotor magnet 5. This is how we faced each other. The other configurations are substantially the same as those of the previously described embodiments, so explanations will be omitted.

This embodiment is composed of a so-called three-phase brushless motor. Six coils 6a to 6f and three Hall elements 21a to 21c are installed as windings at appropriate locations in the magnetic field of the rotor magnets 5 and 5', and the magnetic pole position and polarity of the rotor magnets are controlled by the Hall elements. The magnitude and direction of the current flowing through the six coils is controlled by an electronic circuit to generate rotational force in a predetermined direction of rotation in the rotor. In addition, the speed is controlled by using the magnitude or frequency of the speed electromotive force induced in a coil printed and wired on the opposite substrate 7 by the FG magnet 22, so that a predetermined stable rotation is maintained. , a polygon mirror (rotating polygon mirror) is rotated at a predetermined speed, and the optical precision of the mirror surface can be maintained at a high level.

As for the speed detection method, in this example, the change in the magnetic force of the FG magnet is detected by the coil on the substrate. Of course, an optical encoder using an LED and a phototransistor may also be used.

In the drive device of the present invention, a rotating member rotatable at the same time as the hub 2 is provided on the outer periphery of the cylindrical hub 2 having a U-shaped cross section fixed to the shaft 10 so that the motor-driven shaft 10 is located at the center thereof. A polygon mirror 1, upper and lower rotor plates 4, 2
0, upper and lower balancers 11, 12, magnets 5, 5' attached to the upper and lower rotor plates, and FG magnet 22, etc. attached to the upper rotor plate, to the shaft 1.
0 as the center, and the shaft 10 and these rotating members can be finished simultaneously using the center holes 10a, 10b provided at both ends of the shaft 10 as a reference, so high precision can be easily maintained. .

Further, since the cylindrical member is disposed around the outer periphery of the cylindrical hub 22, the overall shape forms a cylindrical body, and therefore, dynamic balance can be easily maintained during rotational driving. Another advantage is that the upper rotor plate 4 and magnet 5, as well as the lower rotor plate 20 and magnet 5', are each made of plastic magnets and can be easily manufactured by integral molding. Furthermore, it goes without saying that the FG magnet 22 and the magnet 5 can be integrally formed and operated. It is also possible to use only the upper magnet 5 and omit the lower magnet 5'.

In addition, the polygon mirror drive device equipped with the drive motor according to the present invention is configured to be flat and compact, and can rotate smoothly so that the laser beam can be incident and reflected at an accurate mirror surface position, so that scanning of the light beam at a predetermined speed is possible. It must be done accurately.

Furthermore, droplets of lubricating oil that are scattered outward due to centrifugal force while the rotating member rotates together with the shaft 10 pass through the gap between the hub 2 and the shaft support shaft 3 and are formed between the lower balancer 12 and the bottom of the shaft support shaft 3. Since the oil flows into the cavity, there is no risk that the polygon mirror 1 will be contaminated by oil droplets. Further, a lubricating oil leak hole (not shown) may be provided at an appropriate location at the bottom of the L-shaped cylindrical shaft branch. Furthermore, unlike the conventional configuration in which the rotational force of the motor is transmitted to the hub through the shaft to rotate the mirror, the configuration of the present invention is such that the rotational force of the motor directly acts on the hub and rotates the mirror. Since it rotates together with the hub, it maintains high rotational accuracy.

[Brief explanation of drawings]

Figure 1 shows a conventional polygon mirror drive device. Second
The figure is a sectional view of a polygon mirror driving device according to the present invention. FIG. 3 is an enlarged plan view of the air-core winding group viewed from below the upper rotor plate. FIG. 4 is a sectional view of another embodiment of the invention. 1...Polygon mirror, 2...Hub, 3...Shaft support shaft, 4...Upper rotor plate, 5...
Rotor magnet (upper), 5'... Rotor magnet (lower), 6... Winding coil group, 7... Board (winding) stator, 8... Lower case, 9... Upper case, 10... ...Shaft, 20...Lower rotor plate, 21a, 21b, 21c...Hall element,
22...FG magnet.

Claims (1)

[Scope of Claims] 1. A cylindrical hub having a U-shaped cross section is fitted around the outer periphery of a cylindrical shaft support shaft having an L-shaped cross section, and the shaft whose end portion penetrates and is fixed to the upper surface of the hub is used to support the shaft. A shaft is rotatably mounted on the inside of the shaft, and a polygon mirror, an upper rotor plate, and a lower rotor plate are each fixed horizontally at right angles to the hub on the outer periphery of the hub,
The upper rotor magnet mounted on the upper rotor plate, the stator board supported horizontally on the lower case, and the lower rotor magnet mounted on the lower rotor plate face the winding group mounted on the stator board through gaps. and a cavity formed by the polygon mirror provided on the outer periphery of the hub, the upper rotor plate, the lower rotor plate, the upper and lower magnets provided on the upper and lower rotor plates, and the hub together with the shaft and the upper case and the lower case. A polygon mirror drive device with a rotatable interior. 2. The polygon mirror according to claim 1, in which the upper magnet provided on the upper rotor plate and the lower magnet provided on the lower rotor plate are made of plastic magnets, and are formed integrally with the respective plates. Drive device. 3. The polygon mirror drive device according to claim 1, wherein lubricating oil droplets pass through the gap between the shaft support shaft and the hub and flow into the gap formed by the inner bottom part of the support shaft and the lower balancer. . 4. The polygon mirror drive device according to claim 1, which is formed by simultaneously finishing the shaft and the rotating member. 5. The polygon mirror drive device according to claim 1, wherein an air-core winding is disposed between the base and the substrate, and the rotor magnet mounted on the rotor plate and the substrate face each other so as to maintain a gap. .