JPH06332079A - Optical system driving device - Google Patents

Abstract

PURPOSE:To prevent a blurred picture by making engaged gear backlash smaller than other part only at the time starting the driving of a scanner in an optical unit driving the scanner by a rack gear and a pinion. CONSTITUTION:A fixed rack gear 21 and a movable rack gear 31 are integrally attached to a rotary shaft 17 so as to respectively engage with the pinions 15 and 16, and the rotary shaft 17 is rotated by driving a rack gear for input and performs self-travelling along the fixed rack gear 21 and moves a light source unit. Then the fixed rack gear 21 is finely bent on a tooth side at the point of a length 1 which is approximately 20mm from the start of the tooth being the driving start part gear 22 of the fixed rack gear 21, and the height (h) of a tip is made higher by approximately 0.15-0.20mm so that the backlash with the pinion 15 is made smaller to about the half of a normal driving part. Therefore the engagement of the fixed rack gear 21 and the pinion 15 is tightened at the driving start part of the scanner, and a brake is applied and a shock between gears is eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical system driving device used in a scanner of an image forming apparatus such as a copying machine or a printer.

[0002]

2. Description of the Related Art A table glass is used as a scanner in a movable copyboard type copy machine, and a copy lamp unit, a mirror unit or a combination thereof is used as a scanner in a fixed copyboard type copy machine. Note that, for example, in a fixed copyboard type copying machine, a light source unit including a lamp as a light source and a first mirror is reciprocally moved to scan an original document placed on the original plate, and reflected light from the original document is scanned. Is exposed to the photoconductor through the second and third mirrors mounted on the movable mirror unit, the lenses, the fourth and fifth mirrors mounted on the mirror holder, and the sixth mirror fixedly arranged. An image is formed by performing a developing process of supplying toner to the exposed surface of the photoconductor, and then performing a process process of transferring the toner image on the photoconductor to a sheet.

However, in any type of copying machine, at the start of driving the scanner, a shock caused when the pinion starts to mesh with the rack gear appears in the copy as an image blur.

Further, in the copy plate moving type copying machine described in Japanese Patent Laid-Open No. 63-161440, when the copy platen is projected, the backlash between the rack gear and the pinion is at the normal position due to its own weight when the copy platen is projected. It will be wider compared to
Although the backlash interval is corrected by that amount and held over the entire area, image blur occurs when the driving of the scanner is started.

[0005]

With respect to the image blur at the leading end of the sheet in the conventional optical system driving device of the copying machine or the like as described above, the shock of the meshing of gears at the start of driving the scanner is absorbed. Although a means for braking a scanner or the like with a leaf spring or the like has been taken, the pressure of the leaf spring depends on the precision of parts, and the effect on image blur varies.

[0006]

In order to solve the above-mentioned problems, the optical system driving device of the present invention is an optical unit for driving a scanner by means of a rack gear and a pinion. The engagement with the pinion is characterized in that the backlash is made smaller in only the drive start portion of the scanner than in the other drive portions.

Further, the present invention is characterized in that the rack gear portion corresponding to the drive start portion of the scanner is slightly bent toward the tooth side.

Furthermore, the rack gear portion corresponding to the drive start portion of the scanner is formed with helical teeth, the other rack gear portions are formed with spur teeth, and the pinion meshing with the rack gear is formed with spur teeth. Is.

[0009]

In the optical system drive device according to the present invention, the backlash between the rack gear and the pinion is small at the drive start portion of the scanner, and the shock due to the gear connection is eliminated, and the drive transmission of the scanner is smoothly operated from the acceleration motion to the constant speed motion. Become.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the optical system driving device of the present invention will be described below, for example, for a scanner of a fixed platen type copying machine.

In the scanner, as shown in FIG. 1, a light source unit 2 is arranged below the document table 1 so as to scan a document on a document table 1 made of hard glass.
The light source unit 2 has a movable base 3 which is movable over the entire length in the scanning direction, and is reciprocated in the scanning direction from the movement start position (home position) in the A direction and the B direction. The movable base 3 has a flat plate shape extending in a direction orthogonal to the scanning direction, and the lamp 4, the reflection plate 5, the first mirror 6 and the like are mounted on the movable base 3. The light emitted from the lamp 4 is applied to the document placed on the document table 1 and reflected by the document. Reflected light from the document is guided to a movable mirror unit 7 arranged in the scanning direction of the light source unit 2 via a first mirror 6 mounted on the movable base 3.

A second mirror 8 and a third mirror 9 are mounted on the mirror unit 7, and the reflected light guided to the mirror unit 7 travels along the optical path by the second mirror 8 and the third mirror 9. Is reflected. And the third mirror 9
The light reflected by is passed through a lens 10 provided between the light source unit 2 and the mirror unit 7, and is guided to a mirror holder 11 provided near the home position of the light source unit 2.

The mirror holder 11 includes a fourth mirror 1
The second and fifth mirrors 13 are mounted. 4th mirror 1
The second and fifth mirrors 13 reverse the optical path of the guided reflected light and guide it to the sixth mirror 14 fixedly arranged in the middle of the scanning direction in the copying machine. The sixth mirror 14 directs the optical path of this reflected light downward to expose it on a photosensitive drum (not shown). As a result, a latent image is formed on the photosensitive drum, and then a known image forming process is performed.

The mirror unit 7 is a light source unit 2
Is in the home position, it is located at the center of the moving path and is movable from the center to the other end of the moving path. The mirror unit 7 is ½ of the moving speed of the light source unit 2 in the same direction as the moving direction of the light source unit 2 by the optical system driving device described below.
It is moved synchronously at the speed of.

The guide fixed rack gear 21 is provided along the entire length of the moving path of the light source unit 2 along the lower side of one side edge thereof, and is fixed above the fixed rack gear 21. Rack gear 2
1, and a movable rack gear 31 having a length substantially half that of the fixed rack gear 21 is provided.

The optical unit is driven to reciprocate in the light source unit 2 and the mirror unit 7 provided in the optical path between the light source unit 2 and a photoconductor (not shown) is moved at a predetermined speed in the moving direction of the light source unit 2. Moved by the ratio.
The fixed rack gear 21 arranged along the moving path of the light source unit 2 and the mirror unit 7 provided along the movable rack gear 31 are slidably provided on a guide shaft (not shown). The fixed rack gear 21 and the movable rack gear 31
Further, the first pinion 15 and the second pinion 16 are integrally attached to the rotary shaft 17 so as to mesh with each other, and the rotary shaft 17 is connected to an input rack gear (not shown). The rotation shaft 17 is rotated by the drive of the input rack gear, and the light source unit 2 is moved by self-propelled along the fixed rack gear 21, while the first pinion 15 and the second pinion 15 are also moved.
The diameter of the pinion 16 in the pitch is moved by the traveling unit set in association with the speed ratio of the light source unit 2 and the mirror unit 7.

The traveling section will be described below. FIG. 2 (a) is a perspective view of the traveling section, and FIG. 2 (b) is a schematic front view of a drive start portion of the traveling section. Fixed rack gear 2
20m from the start of the tooth which is the drive start partial gear 22 of 1
It is slightly bent to the tooth side at a length l of about m, and the height h is increased by about 0.15 to 0.20 mm at the tip, and the table 23 is placed between the reference plane of the main body of the copying machine. It is something to insert.
The backlash with the first pinion 15 that meshes with the drive start part gear 22 of the fixed rack gear 21 is about half of the backlash of the basic design, that is, the backlash of the normal drive part. The reason is the fixed rack gear 2
This is because if the backlash between the first pinion 15 and the first pinion 15 is too small, the load will increase and the power of the drive motor will be insufficient, and if the backlash is too large, the braking effect of the running portion will be lost. .

The height of the rotary shaft 17 during traveling of the first pinion 15 meshing with the fixed rack gear 21 is constant, and the backlash value varies depending on the traveling speed of the scanner and the gear module. Not a constant number. Height h at the tip of the fixed rack gear 21
Is increased by 0.20 mm, the backlash is reduced over the increased range. If the backlash becomes smaller, the fixed rack gear 21 and the first pinion gear 15 mesh more tightly, and the state is the same as when the brake is applied.

As another means for reducing the backlash in the vertical direction between the fixed rack gear 21 and the first pinion 15, that is, in the meshing direction, the traveling height of the rotary shaft 17 of the first pinion 15 at the drive start portion 22 is lowered. Alternatively, the teeth of the fixed rack gear in the drive start partial gear 22 can be raised.

Next, FIG. 3 (a) is a perspective view of another embodiment of the traveling unit, and FIG. 3 (b) is a schematic perspective view of a drive starting portion of the traveling unit. The fixed rack gear 21 has teeth 24 ', 24', ... in the front-rear direction over a length 1 of about 20 mm from the start of the teeth which are the drive start partial gears 24.
As a helical tooth with a width w of about 0.20 mm,
To the extent of the other drive part gear 21, the teeth 21 ',
21 ', ... are constructed as flat teeth. 3B is a portion where the tooth shape of the fixed rack gear 21 is switched from the helical tooth 24 'to the spur tooth 21', and the side with a narrow tooth thickness (groove side) is the first pinion. Is the same as the tooth thickness of 15,
The front side of FIG. 3B is wider than the tooth thickness of the first pinion 15.

The first pinion 15 that meshes with the helical teeth 24 'of the drive start partial gear 24 of the fixed rack gear 21 and the normal spur tooth 21' is a spur tooth, and backlash occurs within the range of this helical tooth 24 '. Becomes smaller. This 0.20 mm
If the backlash is reduced to a certain degree, the engagement between the helical teeth 24 'of the fixed rack gear 21 and the first pinion 15 becomes tight, and the state is the same as when the brake is applied.

[0022]

Since the present invention has the above-described structure, the connection of each drive is unstable because the load state is changed from the no-load state at the start of copying, but the drive of the scanner is started. The brake is applied by the small backlash engagement of the fixed rack gear and the pinion in the part,
If there is no shock between the gears and the scanner is running during the drive start part, the drive connection is stable, after that it will be a smooth operation to the constant speed motion, and the image blur that occurred at the start of the drive will disappear. is there.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing the overall structure of an embodiment of an optical system driving device of the present invention.

FIG. 2 is an enlarged view of a traveling unit of the device.

FIG. 3 is an enlarged view of another traveling unit of the present device.

[Explanation of symbols]

 1 Document Plate 2 Light Source Unit 7 Mirror Unit 11 Mirror Holder 15 First Pinion 16 Second Pinion 17 Rotation Shaft 21 Fixed Rack Gear 21 'Fixed Rack Gear Flat Teeth 24' Fixed Rack Gear Bevel Teeth 31 Movable Rack Gear

Claims (3)

[Claims] 1. In an optical unit for driving a scanner with a rack gear and a pinion, the backlash of the engagement between the rack gear with which the scanner advances and retracts with the pinion on the scanner side is made smaller than the other drive portions only at the drive start portion of the scanner. An optical system driving device characterized by. 2. The optical system driving device according to claim 1, wherein a rack gear portion corresponding to a driving start portion of the scanner is slightly bent toward a tooth side. 3. A rack gear portion corresponding to a drive start portion of the scanner is a helical tooth, another rack gear portion is a spur tooth, and a pinion meshing with the rack gear is a spur tooth. Item 2. The optical system driving device according to Item 1.