JPH02289835A - scanning optical device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention is applicable to, for example, a laser beam printer. This article relates to scanning optical devices installed in copying machines, etc. (Prior Art) Conventionally, as this type of scanning optical device, there is one shown in FIG. 8, for example. In the figure, 100 indicates a scanning optical device installed in a laser beam printer,
The original P placed on the original table glass 101 is illuminated by the illumination light source 10.
2 irradiates light in a slit shape, and the reflected light is transmitted to the first mirror l03, the second mirror 104, and the third mirror 105.
, and is imaged onto a reading sensor 107 using COD or the like through a projection lens 106, the image of the original P is read, and the image of the original P is copied based on the read image information.

Further, in this device, the first optical bench 108 on which the illumination light source 102 and the first mirror 103 are installed, and the second optical bench 109 on which the second mirror 104 and the third mirror 105 are installed are in a stepping mode. The document is scanned by being driven in the left-right direction in the figure by a drive motor such as . At this time, in order to keep the optical path length constant, the first optical bench 108 is moved at a speed of V, and the second optical bench 109 is moved at a speed of V/2. are driven synchronously. (Problems to be Solved by the Invention) However, in the case of the above-mentioned conventional technology, the scanning optical system vibrates due to the vibration of the drive motor, and in particular, in the case of a stepping motor, specific vibrations caused by the drive pulse,
The problem was that the so-called cogging phenomenon caused uneven rotation of the motor, which caused the optical system to vibrate violently, resulting in a deterioration in reading accuracy. In order to solve this problem, methods have been adopted to increase the mechanical strength of the optical system or to make the natural frequency of the optical system different by at least one order of magnitude compared to the driving pulse frequency of the stepping motor. In the latter case, the disadvantage is that the device becomes larger and the cost increases, and in the latter case, the maximum scanning speed of the optical system can reach approximately 60 times the minimum scanning speed depending on the magnification ratio and scanning direction. It was difficult to set the natural frequency of the optical system to be different from the total driving frequency of the stepping motor to accommodate this wide range of scanning speeds. Furthermore, a method of reducing the cogging phenomenon of a stepping motor by attaching a flywheel to the stepping motor has been considered. In recent years, in order to copy a large number of sheets at high speed, it has become necessary to perform a return scan at high speed in which the optical system moves from the scan end position to the scan start position when not scanning, and sometimes when scanning the original. It is necessary to perform the return scan at a speed more than 7 times faster than the original speed. However, in the method using the flywheel described above,
Attaching a flywheel increases the inertia of the motor, making it difficult to control the motor's rotational speed, and the problem arises that the motor is susceptible to step-out, especially when performing high-speed return scanning. The present invention has been made to solve the problems of the prior art described above, and its purpose is to provide a scanning optical device that can scan a document with high precision and perform return scanning at high speed. It's about doing. (Means for Solving the Problems) In order to achieve the above object, the present invention provides a scanning optical device in which an optical system is driven by a drive motor to scan a document, in which the optical system is moved from a scanning start position. A switching means is provided for coupling the flywheel to the drive motor during document scanning in which the document moves to a scanning end position, and for separating the flywheel from the drive motor during return scanning in which the optical system moves from the scanning end position to the scanning start position. It is characterized by: (Function) In the present invention having the above configuration, when scanning a document,
Since the flywheel is coupled to the drive motor and the inertia of the drive motor is increased, the occurrence of the cogging phenomenon of the drive motor and uneven rotation of the motor are reduced, and vibration of the optical system is prevented. Furthermore, during return scanning, the flywheel is separated from the drive motor and the inertia of the drive motor is reduced, making it easier to control the rotational speed of the drive motor and allowing high-speed return scanning. (Examples) The present invention will be described below according to illustrated examples. 1st
The figure is a perspective view showing a schematic configuration of a scanning optical device according to an embodiment of the present invention. In the figure, reference numeral 1 indicates a scanning optical device installed in a laser beam printer, which includes an illumination light source (not shown), a first optical bench 2 on which a first mirror is installed, and a second mirror (not shown). A drive wire 4 connects the second optical bench 3 with the third mirror installed, the first optical bench 2 and the second optical bench 3;
5. It is composed of a stepping motor M (hereinafter referred to as motor M) as a drive motor which is driven via a large driving bobbly 6 with a radius of R and a small driving bobbin 7 with a radius of R/2. One drive wire 4.4 is attached to each end of the first optical bench 2, and one drive wire 5.5 is attached to each end of the second optical bench 3.
is attached, the two drive wires 4.4 are individually wound around the large drive boob 6.6, the two drive wires 5, 5 are individually wound around the small drive boob 97.7, and Idol Boori 8, 8. It is placed under tension by... The large drive pulleys 6, 6 and the small drive pulleys 97, 7 are all fixed to one drive shaft 9, and the drive shaft 9 is rotationally driven by a motor M via a timing pulley 10.11 and a timing belt l2. It will be done. Also, the motor shaft MS on the opposite side from the timing boolean 10
is provided with a flywheel Fl and an electromagnetic clutch 13 as a switching means for connecting and disconnecting the flywheel F1 and the motor M. FIG. 2 is a schematic plan view showing a part of this scanning optical device 1;
3 is a longitudinal sectional view showing the first optical bench 2, and FIG. 4 is a longitudinal sectional view showing the large driving boob 6. As shown in FIGS. 2 and 3, the first optical bench 2 has a sliding member 1 with a small coefficient of friction.
An elastic member l7 with high elasticity is attached to the first optical bench 2 and is in contact with the two rails 15 and 16 through the
and the regulating member 18 support one rail 15 via sliding members 19, 20, and the first optical bench 2 supports the rails l5, 1.
Move along 6. Similarly, the second optical bench 3
You will be directed to 5.16. As shown in FIG. 4, the drive wire 4 is wound along a groove 21 formed in a spiral shape on the cylindrical side surface of the large drive boob 6, and is wound along a slot 6a provided in the large drive boob 6. After being drawn in and fixed to the bottom of a recess 6b provided in the center of this slot 6a with a screw 22, it is further wound around the large drive bobbin 6 along the groove 2l. The large drive boob 6 is fixed to the drive shaft 9 by screws 23 screwed in in the radial direction and pushed into a flat part 9a provided on the cylindrical surface of the drive shaft 9. It has been done. Drive small boob 7
is similarly fixed to the drive shaft 9. This drive shaft 9 is supported by a bearing (not shown) so as to be movable in the axial direction.

As shown in FIG. 2, this drive wire 4 is applied with tension by being hung around an idler bobber 8 rotatably supported by a shaft 8a. The shaft 8a of the idler bogie 8 is fixed to a slide 8b, and the slide 8b is supported by a guide bar 80 so as to be freely movable in the axial direction. is biased in the opposite direction. As a result, the drive wire 4 is pulled in the opposite direction to the large drive bobbin 6 and tension is applied. After the drive wire 4 is thus held by the large drive boom 6 and the idle boom 8, both ends are attached to one end of the first optical bench 2. Similarly, the drive wire 5 is connected to the drive small bobbly 7 and the idle bobbly 8.
is held on the second optical bench 3. Figure 5 is a longitudinal sectional view showing the motor M section. In the figure, the flywheel Fl is rotatably and axially movably fitted into the motor shaft MS via a bearing 25, and with an appropriate air gap between the flywheel Fl and the flywheel Fl, the clutch 13 is connected to the motor shaft MS by a set screw 26. It is fixed to . Further, when the rotation of the clutch 13 is to be stopped, a portion 13a of the clutch l3 is engaged with a rotation stop plate 27 extending from the main body of the device, and the rotation of the clutch is stopped. When scanning a document to read the document, the clutch l3 is turned on and the armature of the flywheel F1 and the clutch l3 are coupled, so that the flywheel F1
is connected to the motor shaft MS, and during return scanning during non-reading, the clutch is turned off and the flywheel F1 is connected to the motor shaft M.
Separated from S.

When using this device to continuously scan, read, and copy a large number of originals, first, the clutch 13 is turned on and the flywheel Fl is connected to the motor M.
The motor M rotates to rotate the drive shaft 9 clockwise (in the direction of the solid arrow) in FIG.
The optical bench 2 and the second optical bench 3 are synchronized and have respective speeds V,
It moves in the direction toward the drive shaft 9 (in the direction of the solid line arrow in Figure 1) at V/2. As a result, the original (not shown) is scanned and sent to a reading device (not shown). The image forming device reads and copies the original image. When the scanning of the document is completed, the clutch 13 is turned off and the flywheel F1 is separated from the motor M, and the motor M rotates in the opposite direction to rotate the drive shaft 9 counterclockwise (in the direction of the dashed arrow) in FIG. The large drive pulley 6 and the small drive pulley 7 rotate counterclockwise, and the first
Optical bench 2. The second optical bench 3 moves in the direction away from the drive shaft 9 (
1) from the scan end position to the scan start position in preparation for the next document scan. The above-described original scanning and return scanning are repeated to continuously read and copy images of the original. In the apparatus of this embodiment, when scanning a document, the flywheel F1 is connected to the motor M and the inertia of the motor M is increased, thereby reducing the cogging phenomenon of the motor M and the uneven rotation of the motor M. 1 optical bench 2 and 2nd
Vibration of the optical bench 3 is prevented. Therefore, images can be read with high precision. Incidentally, by gradually increasing the voltage of the clutch 13 to smoothly connect the flywheel F1 with the motor M, the impact on the motor M can be alleviated, vibration of the optical system can be prevented, and reading accuracy can be further improved. Can be done. During return scanning, the flywheel F1 is operated by the motor M.
Since the inertia of the motor M is reduced by being separated from the motor M, return scanning can be performed at high speed without causing the motor M to step out. Therefore, the number of copies per unit time can be increased and copying can be performed at high speed.

Furthermore, although an electromagnetic clutch is used as the switching means in this embodiment, a one-way clutch may be used as the switching means, as shown in FIG. In the figure, a flywheel F2 to which a one-way clutch 28 is fixed is rotatably fitted onto the motor shaft MS, and is held by an E-ring retaining ring 30 via a spring washer 29. This one-way clutch 28
locks to the motor shaft MS during document scanning, thereby connecting the flywheel F2 to the motor M, and during return scanning, the one-way clutch 28 becomes free with respect to the motor shaft MS, thereby disconnecting the flywheel F2 from the motor M. be separated.

Furthermore, in the apparatus of this embodiment, even if the flywheel F1 and clutch 13 are attached to the drive shaft 9 as shown in FIG. 7, the same effects as in the above embodiment can be obtained. In this case as well, a one-way clutch as shown in FIG. 6 may be used as the switching means. In this embodiment, a scanning optical device of both-side driving type is used, but the same effect can be obtained even if the present invention is applied to a scanning optical device of one-sided driving type. Further, in this embodiment, a scanning optical system installed in a laser beam printer is taken as an example, but the present invention is not limited to this, and can also be applied to a scanning optical system installed in an analog copying machine, for example. It is applicable. (Effects of the Invention) The present invention has the above-described configuration and operation, and the switching means connects the flywheel to the drive motor during original scanning, and disconnects the flywheel from the driving motor during return scanning, so that the original scanning can be performed. It is possible to reduce the vibration of the optical system and perform return scanning at high speed.

Therefore, when reading and copying images of originals using the apparatus of the present invention, it is possible to read with high precision and copy a large number of sheets at high speed. Furthermore, in the device of the present invention, there is no need to increase the mechanical strength of the optical system in order to prevent vibration of the optical system, so the device can be made smaller and the cost of the device can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a schematic configuration of a scanning optical device according to an embodiment of the present invention, FIG. 2 is a schematic plan view showing a part of the same device,
Fig. 3 is a longitudinal sectional view showing the first optical bench in the same school, Fig. 4 is a longitudinal sectional view showing the large drive pulley 9 of the same device, Fig. 5 is a longitudinal sectional view showing the motor part of the same device, Fig. 6 is a longitudinal sectional view showing an example in which a one-way clutch is used as a switching means in the same device, Fig. 7 is a schematic perspective view showing an example in which a flywheel and clutch are attached to the drive shaft in the same device, and Fig. 8
The figure is an explanatory diagram showing the configuration of a scanning optical device installed in a laser beam printer. Explanation of symbols 1... Scanning optical device 2... First optical bench 3...
2nd optical bench 4.5... Drive wire 6... Large drive boolean 7... Small drive boolean 9... Drive shaft l3... Clutch (switching means) M... Stepping motor (drive Motor) Fl, F2
...Flywheel Fig. 3 Fig.

Claims (1)

[Scope of Claims] A scanning optical device in which an optical system is driven by a drive motor to scan a document, wherein a flywheel is coupled to the drive motor during document scanning in which the optical system moves from a scan start position to a scan end position. A scanning optical device, further comprising a switching means for separating the flywheel from the drive motor during return scanning in which the optical system moves from a scanning end position to a scanning starting position.