JP2623007B2 - Scanning optical device - Google Patents

Description

The present invention relates to a scanning optical device provided in, for example, a laser beam printer, a copying machine, and the like.

(Prior Art) Conventionally, as this kind of scanning optical device, there is one as shown in FIG. 8, for example. In the figure, 100 indicates a scanning optical device provided in a laser beam printer,
A document P placed on a platen glass 101 is irradiated with light in a slit shape by an illumination light source 102, and the reflected light is transmitted through a first mirror 103, a second mirror 104, a third mirror 105, and a projection lens 106 to a CCD. The image of the document P is formed on the reading sensor 107 using an image reading method, and the image of the document P is copied based on the read image information.

Further, in this apparatus, a first optical table 108 on which an illumination light source 102 and a first mirror 103 are installed, and a second mirror 104
And the second optical table 109 on which the third mirror 105 is installed is driven by a driving motor such as a stepping motor in the left-right direction in the figure to scan the original. At this time, in order to keep the optical path length constant, The first optical bench 108 is driven synchronously at the speed V and the second optical bench 109 is driven at the speed V / 2.

(Problems to be Solved by the Invention) However, in the case of the above-described conventional technology, the scanning optical system vibrates due to the vibration of the drive motor. The so-called cogging phenomenon causes uneven rotation of the motor, causing the optical system to vibrate violently, thus causing a problem that reading accuracy is deteriorated.

In order to solve this problem, a method of increasing the mechanical strength of the optical system or changing the natural frequency of the optical system by at least one digit compared with the drive pulse frequency of the stepping motor has been adopted. In this case, there is a disadvantage that the apparatus becomes large and the cost becomes high.In the latter case, the scanning speed of the optical system is wide in which the maximum scanning speed reaches about 60 times the minimum scanning speed depending on the magnification and the scanning direction. Therefore, it is difficult to set the natural frequency of the optical system to be different from the entire driving frequency of the stepping motor corresponding to this wide range of scanning speed.

9 (a), (b), and FIG.
A method of reducing the occurrence of the cogging phenomenon of the stepping motor by attaching a flywheel as shown in FIG. In FIG. 5A, a weight member F10 is fixed to a motor shaft MS of the motor M by a set screw S to increase the inertia of the motor M. In FIG. Damping member 110
And the motor M is fixed to the motor shaft MS by the set screw S, the inertia of the motor M is increased, and the vibration damping member 11
By 0, vibration energy is converted to heat energy or the like, and rotation unevenness of the motor M is reduced. In the flywheel F12 shown in FIG. 3 (c), a fixed flange member F12a made of a magnetic material such as an iron-based material
The magnet F12b is fixed to the MS, and is attracted to the fixed flange member F12a via a sliding member F12c made of synthetic resin, phosphor bronze, or the like. The inertia of the motor M is increased by the weight of the magnet F12b, and the fixed flange member is increased.
The rotation unevenness of the motor M is reduced by the sliding of the magnet F12a and the magnet F12b via the sliding member F12c.

Here, in recent years, in order to copy many sheets at high speed, it is necessary to perform high-speed return scanning in which the optical system moves from the scanning end position to the scanning start position during non-reading. It is necessary to perform the return scanning at a speed of 7 times or more. However, in the method using the flywheel described above, since the inertia of the motor is increased by attaching the flywheel, it is difficult to control the rotation speed of the motor. There is a problem that a step-out easily occurs. When a magnet as shown in FIG. 9 (c) is used, the magnet itself vibrates at the time of high-speed rotation of the return scanning because the attraction force of the magnet is not taken into consideration, and this vibration is generated via the motor shaft. The vibration is transmitted to the optical system and remains at the time of the next original scanning, and the read image is often blurred. SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems of the related art, and an object of the present invention is to provide a scanning optical device capable of scanning a document with high accuracy and performing return scanning at high speed. Is to do.

(Means for Solving the Problems) In a scanning optical apparatus in which an optical system is driven by a drive motor to scan an original, a fixed flange member made of a magnetic material fixed to a motor shaft of the drive motor is partially or entirely provided. Is provided with a flywheel in which a weight member made of a magnet is attached via a sliding member, a product a of a maximum angular acceleration during scanning of the drive motor and an inertia moment of the weight member, and a sliding member of the magnet. The relationship between the product b of the tangential component of the outer peripheral tangent and the radius of the attraction portion at the attraction portion of the attraction force to the fixed flange member via the optical system is scanned during document scanning when the optical system moves from the scanning start position to the scanning end position. a <b and a> b at the time of return scanning in which the optical system moves from the scanning end position to the scanning start position.

(Operation) In the apparatus of the present invention having the above configuration, assuming that the inertia moment of the weight member is I and the angular acceleration of the drive motor at the time of scanning is, the rotation moment a due to the inertia force of the weight member is a = I × Also, assuming that the component of the tangent to the outer periphery of the attracting force (magnetic force) to the fixed flange member via the sliding member of the magnet is F and the radius of the attracting portion is r, the rotational moment b due to the attracting force of the magnet is b = F × r.

Then, at the time of document scanning, if the maximum angular acceleration of the drive motor at this time is FWmax, then a = I × FWmax <F × r = b, so that the attractive force of the magnet overcomes the inertial force of the weight member and the weight member It rotates with the motor shaft. Accordingly, the inertia of the drive motor increases due to the weight of the weight member, so that the occurrence of the cogging phenomenon of the drive motor and the uneven rotation of the motor are reduced, and the vibration of the optical system is prevented.

Also, at the time of return scanning, if the maximum angular acceleration of the drive motor at this time is BKmax, then a = I × BKmax <F × r = b, so that the inertial force of the weight member overcomes the attraction force of the magnet and the drive motor The torque is not transmitted to the weight member. Therefore, since the inertia of the drive motor is reduced, the control of the rotation speed of the drive motor becomes easy, and the return scan can be performed at high speed.

(Examples) Hereinafter, the present invention will be described with reference to the illustrated examples. FIG. 1 is a perspective view showing a schematic configuration of a scanning optical device according to one embodiment of the present invention. In the figure, reference numeral 1 denotes a scanning optical device provided in a laser beam printer, and a first optical table 2 on which an illumination light source and a first mirror, not shown, are installed.
A second optical bench 3 on which a second mirror and a third mirror (not shown) are installed, and a driving wire 4 for connecting the first optical bench 2 and the second optical bench 3 to each other;
5. A stepping motor M as a driving motor driven through a large driving pulley 6 having a radius R and a small driving pulley 7 having a radius R / 2.
(Hereinafter referred to as a motor M).

Driving wires 4, 4 are provided one at each end of the first optical bench 2.
However, at both ends of the second optical bench 3, one drive wire 5
The two drive wires 4, 4 are individually wound on the large drive pulley 6, 6, and the two drive wires 5, 5 are individually wound on the small drive pulley 7, 7, respectively. The tension is given to the idle pulleys 8, 8,... Individually.

The drive large pulleys 6, 6 and the drive small pulleys 7, 7 are all fixed to one drive shaft 9, and the drive shaft 9 is a timing pulley.
The motor M rotates through the timing belts 10 and 11 and the timing belt 12.

Further, a flywheel F1 is provided on the motor shaft MS opposite to the timing pulley 10. FIG. 2 is a longitudinal sectional view showing the structure of the flywheel F1. In the figure, a fixed flange member F1a made of a magnetic material is fixed to a motor shaft MS by a set screw S, and a weight member F1b coupled with a magnet m by a screw 30 becomes a sliding member F1c made of a synthetic resin, phosphor bronze, or the like. It is attached by suction to the fixed flange member F1a through the intermediary. 31 is a bearing and 32 is a thrust stopper.

In this flywheel F1, the moment of inertia of the weight member F1b including the magnet m is I, the maximum angular acceleration of the motor M when scanning the document is FWmax, the maximum angular acceleration during return scanning is BKmax, and the sliding member F1c of the magnet m Tangential component of the attraction force (magnetic force) to the fixed flange member F1a via the
Assuming that F and the radius of the suction portion are r, the values of I, F and r satisfy the following equation.

I × FWmax <F × r <I × BKmax (1) FIG. 3 is a schematic plan view showing a part of the scanning optical device 1, FIG. 4 is a longitudinal sectional view showing the first optical table 2, and FIG. The figure is a longitudinal sectional view showing the large driving pulley 6. As shown in FIGS. 3 and 4, the first optical bench 2 contacts two rails 15, 16 via a sliding member 14 having a small coefficient of friction.
An elastic member 17 having a large elasticity and a regulating member 18 attached to the optical bench 2 sandwich one rail 15 via sliding members 19 and 20, and the first optical bench 2 is connected to the rails 15 and 16. Move along. The second optical bench 3 is similarly guided by the rails 15 and 16. As shown in FIG. 5, the drive wire 4 is wound along a groove 21 formed in a linear shape on the cylindrical side surface of the large drive pulley 6 and drawn into a slot 6a provided on the large drive pulley 6. And a recess 6b provided at the center of the slit 6a.
After being fixed to the bottom of the main body by screws 22, it is further wound around the large drive pulley 6 along the groove 21. Drive large pulley 6
The large drive pulley 6 is fixed to the drive shaft 9 by screwing a screw 23 in the radial direction and pushing the screw 23 into a flat portion 9 a provided on the cylindrical surface of the drive shaft 9. The driving small pulley 7 is similarly fixed to the driving shaft 9. The drive shaft 9 is supported by a bearing (not shown) so as to be movable in the axial direction.

Then, as shown in FIG. 3, the driving wire 4
A tension is applied to the idle pulley 8 rotatably supported on the shaft 8a. The shaft of this idle pulley 8
8a is fixed to a slide 8b, and the slide 8b is supported by a guide bar 8c so as to be movable in the axial direction, and is urged in a direction opposite to the large drive pulley 6 by a coil spring 24 locked to an immobile portion. ing. As a result, the driving wire 4 is pulled in the opposite direction to the driving large pulley 6 and is given tension. After the driving wire 4 is held by the large driving pulley 6 and the idle pulley 8 as described above, both ends are attached to one end of the first optical bench 2. Similarly, the driving wire 5 is held by the small driving pulley 7 and the idle pulley 8 and attached to the second optical table 3.

When scanning, reading, and copying a large number of originals continuously using this apparatus, the motor M rotates and the drive shaft 9 is rotated.
Is rotated clockwise (in the direction of the solid arrow) in FIG. 1, the large drive pulley 6 and the small drive pulley 7 simultaneously rotate clockwise, and the first optical table 2 and the second optical table 3 are synchronized. Direction toward drive shaft 9 at speeds V and V / 2, respectively (first
(In the direction of the solid line arrow in the figure). As a result, a document (not shown) is scanned, and an image of the document is read and copied by a reading device (not shown) and an image forming device. At this time, in the flywheel F1, the attracting force of the magnet m overcomes the inertial force of the weight member F1b, and the weight member F1b rotates together with the drive motor M.

When the scanning of the original is completed, the motor M rotates in the reverse direction to rotate the drive shaft 9 counterclockwise (in the direction of the dashed arrow) in FIG. 1, and the large drive pulley 6 and the small drive pulley 7 The first optical table 2 and the second optical table 3 move from the scanning end position to the scanning start position in the direction away from the drive shaft 9 (in the direction of the dashed arrow in FIG. 1) to move to the next original scanning. Prepare. At this time, the inertial force of the weight member F1b overcomes the attraction force of the magnet m, and the rotational force of the drive motor M is not transmitted to the weight member F1b.

The above-mentioned original scanning and return scanning are repeated, and reading and copying of the original image are continuously performed.

In the apparatus of this embodiment, the weight member F1b of the flywheel F1 rotates together with the motor shaft MS at the time of scanning a document, so that the inertia of the motor M is increased and the motor M
The occurrence of the cogging phenomenon and the uneven rotation of the motor M are reduced, and the vibrations of the first optical bench 2 and the second optical bench 3 are prevented. Therefore, an image can be read with high accuracy.

At the time of return scanning, the rotational force of the drive motor is not transmitted to the weight member F1b, and the fixed flange member F having a small inertia is not transmitted.
Since only 1a rotates together with the motor shaft MS, the inertia of the motor M is reduced, and the return scanning can be performed at high speed without the motor M stepping out. Therefore, the number of copies per unit time can be increased, and copying can be performed at high speed.

Further, a flywheel F2 as shown in FIG. 6 may be provided in place of the flywheel F1 in the above device.
In this flywheel F2, the magnet F2b having the same moment of inertia as the weight member F1b including the magnet m is attached as a weight member to the fixed flange member F2a via the sliding member F2c and attached to the motor shaft MS. I have. The fixing flange member F2a is set screw S as in the above embodiment.
Is fixed to the motor shaft MS. 41 is a bearing, 4
2 is a thrust stopper.

In the flywheel F2, the attracting force (magnetic force) of the magnet increases with an increase in the size of the magnet, but the above equation (1) can be satisfied by increasing the thickness of the sliding member F2c. .

Further, in the apparatus shown in FIG. 1, even if the flywheel F1 is attached to the drive shaft 9 as shown in FIG. 7, the same effect as in the above embodiment can be obtained. In this case, a flywheel as shown in FIG. 6 may be used.

In this embodiment, the scanning optical device of the both-side driving system is used, but the same effect can be obtained by applying the present invention to the scanning optical device of the one-side driving system.

Further, in the present embodiment, the scanning optical system provided in the laser beam printer is taken as an example, but the present invention is not limited to this, and for example, the scanning optical system provided in the analog copying machine may be used. Applicable.

(Effects of the Invention) The present invention has the above-described configuration and operation. By increasing the inertia of the drive motor during original scanning and decreasing the inertia of the drive motor during return scanning, vibration of the optical system during original scanning is reduced. , And return scanning can be performed at high speed.

Therefore, using the apparatus of the present invention to read the image of
When copying, read with high accuracy, and
Many copies can be made at high speed.

Further, in the apparatus of the present invention, it is necessary to increase the mechanical strength of the optical system in order to prevent vibration of the optical system, and to provide control means such as a clutch and a microprocessor for connecting and disconnecting the flywheel. Therefore, the configuration can be simplified, the size of the device can be reduced, and the cost of the device can be reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a schematic configuration of a scanning optical apparatus according to an embodiment of the present invention, FIG. 2 is a longitudinal sectional view showing a configuration of a flywheel of the apparatus, and FIG. FIG. 4 is a schematic plan view, FIG. 4 is a longitudinal sectional view showing a first optical bench of the apparatus, and FIG.
Fig. 6 is a longitudinal sectional view showing a large driving pulley of the apparatus, Fig. 6 is a longitudinal sectional view showing another example of a flywheel, and Fig. 7 is a schematic perspective view showing an example in which a flywheel is attached to a drive shaft in the apparatus. FIG. 8 is an explanatory view showing the configuration of a scanning optical device provided in the laser beam printer.
(B), (c) is a longitudinal sectional view showing a conventional flywheel. DESCRIPTION OF SYMBOLS 1... Scanning optical device 2... 1st optical bench 3... 2nd optical bench 4, 5... Drive wire 6... Large drive pulley 7. F1 Flywheel F1a Fixed flange member F1b Heavy member F1c Sliding member m Magnet M Stepping motor (drive motor)

Claims (1)

(57) [Claims] 1. A scanning optical apparatus in which an optical system is driven by a drive motor to scan an original, wherein a fixed flange member made of a magnetic material fixed to a motor shaft of the drive motor is partially or entirely made of a magnet. A flywheel having a weight member attached via a sliding member is provided, and the product a of the maximum angular acceleration of the drive motor during scanning and the moment of inertia of the weight member is provided, and the product a is provided via the magnet sliding member. The relationship between the product b of the tangential component of the outer peripheral tangent at the attracting portion of the attracting force to the fixed flange member and the radius of the attracting portion is such that a <b, A scanning optical apparatus wherein a> b is satisfied at the time of return scanning in which the optical system moves from the scanning end position to the scanning start position.