JPH0895168A - Image reader - Google Patents

Abstract

PURPOSE: To provide an image reader improved in image quality and reduced in a cost. CONSTITUTION: In the image reader provided with a scanner 11 for reading an original 2 set at a fixed position while moving, a wire rope 16 for moving the scanner 11, a driving pulley 15 whose position is fixed and around which the wire rope 16 is wound by several turns so as to transmit driving force to the wire rope 16, a carriage pulley 20 pivotally supported at the side end surface of the scanner 11 in a main scanning direction, an idle pulley 19 whose position is fixed and which is arranged on an opposite side in a subscanning direction while holding the carriage pulley 20 in between; correcting pulleys 17 and 18 whose rotary shafts are orthogonal with respective pulleys are arranged freely rotatably at the lead-out route of the wire rope 16 respectively led from the driving pulley 15 or the idle pulley 19 and the wire rope 16 is pressed by the outer peripheral surfaces of the correcting pulleys 17 and 18, so that the stretched route of the wire rope 16 is maintained to be a normal route which is parallel with the subscanning direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of an image reading apparatus used as an input means of a copying machine, a printer, a facsimile, or an image forming apparatus having a combination of these functions. The present invention relates to improvement of a moving mechanism of a scanning scanner.

[0002]

2. Description of the Related Art An image forming apparatus utilizing an electrophotographic process, such as a copying machine, a printer, a facsimile machine, etc., is equipped with an image reading device as an image information input means. An image reading device (image scanner) having no image forming unit is also known. The image reading apparatus includes a first scanner having a light source, a reflector and a first mirror, and a second scanner having second and third mirrors for guiding the reflected light of the document to a photoconductor, a CCD or the like. , Each scanner is engaged with a wire rope driven by a motor and driven in the sub-scanning direction. The wire rope is stretched by a pulley, and as the pulley, a drive pulley directly connected to the output shaft of the motor, an idle pulley rotatably supported by the main frame of the apparatus, and further rotatably supported by the carriage of the scanner. There is a carriage pulley. When driving the scanner in the sub-scanning direction, each scanner is parallel to the main scanning direction, and the relationship between each scanner and the wire rope extending in the sub-scanning direction is orthogonal to each other when viewed from the plane direction, In addition, it is necessary for the driving force to be transmitted by the wire rope to be along the direction orthogonal to the scanner in order to ensure stable traveling.

In the scanner moving mechanism having such a structure, what is important is to ensure stable running without microvibration. In order to prevent slight vibration during running of the scanner, particularly high precision is required in the flat image scanner and the digital copying machine, and several steps higher than the precision in the analog copying machine. But conventionally,
Actually, unless the precision and assembly accuracy of the components that make up the drive system and the transmission system are set to a highly accurate structure, a slight vibration occurs and the image quality is adversely affected.

As described above, a transmission body such as a wire rope or a timing belt is used to move the scanner, but the wire rope has a lower vibration generation rate. However, when trying to transmit the driving force using a wire rope, the winding position fluctuates in the axial direction (thrust direction) of the pulley when the wire rope wound around the drive pulley is wound up or sent out. , A component force is generated in the thrust direction. In this case, the wire rope does not pull the scanner extending in the main scanning direction only in the orthogonal direction (sub-scanning direction), and the tensile force in the thrust direction is generated. It is a cause of vibration. Further, as described above, in order to maintain the wire rope extending in the sub-scanning direction in the posture orthogonal to the scanner, high precision component precision and assembly precision are required, which complicates the manufacturing process and increases cost. There was a problem of inviting.

That is, FIG. 6 is a schematic diagram showing the structure of a conventional flat bed type image reading device (image input device), in which a light source 3 is placed on an original 2 fixed on a contact glass 1.
From the CCD, the reflected light of the original is reflected by the mirrors 4, 5 and 6 and folded back, condensed by the lens 7, and then the CCD.
The image is formed at 8, and photoelectrically converted by the CCD 8. The light source 3 and the first mirror 4 constitute a first scanner 11 which is mounted on one carriage and independently advances and retracts in the sub-scanning direction, and the second and third mirrors 5 and 6 are arranged on another carriage. The second scanner 12 which is mounted and independently moves back and forth in the sub-scanning direction.
Make up. FIG. 7 is a perspective view of the image reading apparatus, and the drive mechanism for driving each scanner is a motor 13
A drive pulley 15 driven by a motor 13, a carriage pulley 12P rotatably supported on the carriage side surface of the second scanner 12, an idle pulley 19 rotatably supported by the apparatus body, and these pulleys 12
And a wire rope 16 that is wound around P and 19 and transmits a driving force.

As described above, it is essential that the positional relationship between the scanners 11 and 12 extending in the main scanning direction and the wire rope 16 extending in the sub-scanning direction be orthogonal to each other when seen in the plane direction, and the drive pulleys are orthogonal to each other. Wire rope 16 on 15
As the position of the wire in the thrust direction fluctuates, the pulling direction of the wire rope 16 does not become parallel to the sub-scanning direction, and the scanner is slightly vibrated to cause unstable magnification, image distortion, image jitter, etc. Maintenance issues occur.

In order to solve such a problem, in Japanese Utility Model Laid-Open No. 62-103360, the drive pulley is configured to be movable in the thrust direction so that the winding position of the wire rope around the drive pulley is kept constant. However, this method is sure to increase the cost, and a highly accurate structure is required to move the drive pulley. Further, in Japanese Utility Model Laid-Open No. 63-5763, when winding a wire around drive pulleys arranged at both positions (left and right) in the main scanning direction, the winding direction of the wire around both drive pulleys is reversed. As a result, a configuration is disclosed in which the force applied diagonally to the scanner is made uniform on the left and right. However, with this method, it is difficult to ensure high accuracy due to slipping of wires on the drive pulley, and it is necessary to prepare and assemble parts such as drive pulleys having different shapes on the left and right when assembling. Therefore, the assemblability is poor and the cost is increased.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and maintains the positional relationship between the wire rope and each scanner in an orthogonal state without requiring high precision of parts and assembly, and An object of the present invention is to provide an image reading apparatus that improves the image quality and lowers the cost by keeping the pulling direction of the scanner by the rope always parallel to the sub-scanning direction and preventing the generation of component force in the thrust direction. I am trying. That is, in the present invention, in order to maintain the positional relationship between the scanner and the wire rope in the orthogonal direction at all times without increasing the cost, a new idle pulley is arranged on the wire rope that is led out from the drive pulley in the sub-scanning direction. Therefore, the object is to provide a highly accurate drive transmission mechanism.

Further, by providing a groove on the outer circumference of the drive pulley in which the axial pitch and the inclination angle are gradually increased or decreased, the image reading apparatus in which the wire rope is not bent at the position where the wire rope is wound around the drive pulley. Is intended to provide. Further, since the drive pulley having a long axial length is used, the lead-out length L of the wire rope that is led out from the correction pulley arranged in the immediate vicinity and is wound around the drive pulley becomes long as the wire is wound. In order to prevent the problem that the moving speed gradually decreases,
The output of the motor is gradually increased to the extent that the moving speed of the scanner is gradually reduced.

[0010]

SUMMARY OF THE INVENTION To achieve the above object, the present invention provides a scanner for reading a document set at a fixed position while moving it, a wire rope for moving the scanner, and a driving force transmitted to the wire rope. A drive pulley for fixing the position of winding the wire rope a plurality of times around the carriage, a carriage pulley axially supported on the end face in the main scanning direction of the scanner, and a position fixing arranged on the opposite side of the carriage pulley in the sub scanning direction. In the image reading apparatus having the idle pulley of, a correction pulley having a rotation axis orthogonal to each of the pulleys is rotatably disposed in the lead-out path of the wire rope that is led out from the drive pulley or the idle pulley, By pressing the wire rope by the outer peripheral surface of the correction pulley, the tensioned path of the wire rope is changed to a regular path parallel to the sub-scanning direction. And wherein the maintained.

Further, the drive pulley has a spiral groove for winding the wire rope on the outer peripheral surface thereof, and the axial interval and the inclination direction of each groove portion appearing on the outer peripheral surface of the drive pulley are corrected by the correction. The drive pulleys are made different from each other so as to match the approaching angle of the wire ropes derived from the drive pulleys, and the drive pulleys are changed according to the variation of the derived length of the wire ropes derived from the correction pulleys to the drive pulleys. It is characterized in that it is controlled so as to change the output of the motor for driving.

An embodiment of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a plan perspective view of an image reading apparatus according to an embodiment of the present invention, and FIG. 2 is a view for explaining the principle of the present invention. It should be noted that, with reference to FIG. 6 and FIG. 7 together, the same portions will be denoted by the same reference numerals for description. The first scanner 11 is fixed to a proper position 16A of the wire rope 16, and the first scanner pulley 20A pivotally supported on the side surface of the second scanner 12 fixes the first scanner 11 to the first scanner.
Invert the wire rope extending backward from A into a U shape,
The tip portion 16B is fixed to the apparatus body side. The other end of the wire rope 16 is wound around the idle pulley 19 and then inverted by the second carriage pulley 20B so that the tip 16C is supported by the reading device main body via a spring or the like. As a result, the second scanner 12 is translated in the same direction at a speed half that of the first scanner 11, for example. In this embodiment, the horizontal idle pulley (correction pulley) 17 is arranged on the path of the wire rope 16 led out from each drive pulley 15 in the sub-scanning direction, and the wire rope 1
6 is maintained parallel to the sub-scanning direction, and a horizontal idle pulley (correction pulley) 18 is also arranged on the path of the wire rope 16 led out from each idle pulley 19 to adjust the attitude of the wire rope 16. A characteristic is that the structure is maintained parallel to the sub-scanning direction.

The drive pulley 15, the idle pulley 19, and the carriage pulleys 20A and 20B are all vertical pulleys that rotate along a vertical plane about a horizontal axis, while the horizontal idle pulleys 17 and 18 are used. Is
It is a pulley in a horizontal posture that rotates along a horizontal plane about a vertical axis, and the rotation axes of both pulley groups are orthogonal to each other. In addition, a part of the outer peripheral surface of the horizontal idle pulleys 17 and 18 is a wire rope 1 that is led out from each pulley 15 and 19.
6 is horizontally positioned in the sub-scanning direction and is positioned along the sub-scanning direction line to correct the posture.

Next, FIGS. 4 (a) and 4 (b) are an external view and an operation state explanatory view showing the structure of a drive pulley as another embodiment of the present invention, and FIG. 4 (c) shows a conventional example. It is a figure which shows a fault. The drive pulley 15 of the present invention has a spiral groove 30 for fitting the wire rope 16 on the outer peripheral surface thereof as shown in FIG. 4 (a). The groove 30 has a spiral shape as a whole, but its pitch (axial pitch) is not constant, the pitch between grooves increases toward the shaft end, and the inclination angles differ. The formation angle of each groove is the wire rope 1 from the horizontal idle pulley 17 to the drive pulley 15.
It is set to match the approach angle of 6. The reason is that since the distance L from the idle pulley 17 to the drive pulley 15 is short, the approach angle of the wire rope 16 is as shown in FIG.
This is because the pitch and inclination angle of the groove 30a near the shaft end of the drive pulley 15 is equal to the pitch and inclination angle of the groove 30b near the other end as shown in FIG. When set to, the entry angle of the wire rope 16 and the inclination angle of the groove 30 are displaced as shown in FIG. 4 (c), and the wire rope comes out of the groove and is wound in a bent state. This is because the durability is reduced. On the other hand, if the groove pitch and the inclination angle are matched with the approach angle of the wire rope as shown in FIG. 4 (a), this bending can be prevented and the durability of the wire rope can be enhanced.

By the way, the drive pulley 15 having a long axial length
Is used, the wire rope 16 becomes a horizontal idle pulley 1
When the wire rope is led out from the wire 7 and wound around the outer peripheral surface of the drive pulley 15, the wire rope winds around from the outer side position to the inner side position in the axial direction. Figure 5 (a) shows that state.
The distance (derived length) L from the outer circumference of the horizontal idle pulley 17 to the center of the drive pulley 15 was L1 when wound on the axially outer side position, but the winding position on the axially inner side (left side in the drawing) was changed. As you move, L2, L
3 and it gets longer. This means that the moving speed of the scanner per one rotation of the drive pulley increases as the winding position of the wire rope moves inward in the axial direction. That is, there is a possibility that the scanning speed of the scanner may vary and the obtained image quality may deteriorate. Therefore, in the present embodiment, the moving speed of the scanner is made constant by controlling the output of the motor (stepping motor) 13 as shown in FIG. 5 (b).
That is, after the through-up to a predetermined speed n ₁ in the rising period t ₁ of the scanning start, although during scanning the conventional control method for constant-speed driving of the motor, deriving the length of the wire rope in the present invention L In consideration of the fluctuation of, the deceleration is continued by a small amount. As a result, the rotation speed of the drive pulley is gradually reduced by an amount corresponding to the increase amount of the movement speed of the scanner due to the gradual increase of the lead-out length L of the wire rope, and the movement speed of the scanner can always be kept constant. Of course, the control of the motor is executed by a control unit such as a microcomputer (not shown) according to a predetermined program.

[0016]

As described above, according to the present invention, the positional relationship between the wire rope and each scanner is maintained in an orthogonal state without requiring a high degree of parts accuracy and assembly accuracy, and a scanner using the wire rope is provided. It is possible to provide an image reading apparatus which improves the image quality and lowers the cost by keeping the pulling direction of the disk parallel to the sub-scanning direction and preventing the generation of the component force in the thrust direction. That is, the present invention
In order to maintain the positional relationship between the scanner and the wire rope in the orthogonal direction at all times without increasing the cost, a new idle pulley is placed on the wire rope that is led out from the drive pulley in the sub-scanning direction for highly accurate driving. Provide a transmission mechanism.
As a result, since the positional relationship between the scanner and the wire rope is always orthogonal to each other, microvibration, lateral displacement, etc. do not occur on the scanner, and it is possible to prevent deterioration of image quality.

Further, by providing a groove on the outer circumference of the drive pulley in which the pitch and the inclination angle in the axial direction gradually increase or decrease, bending and vibration of the wire rope at the position where the wire rope is wound around the drive pulley can be eliminated, and winding can be performed. The attachment can be smoothed.

Further, since the drive pulley having a long axial length is used, the lead-out length L of the wire rope which is led out from the correction pulley arranged in the immediate vicinity and wound around the drive pulley becomes long as the wire is wound, and as a result, In order to prevent the problem that the moving speed of the scanner gradually decreases, the output of the motor is gradually increased to an extent commensurate with the gradually decreasing amount of the moving speed of the scanner.

[Brief description of drawings]

FIG. 1 is a plan perspective view of an image reading apparatus according to an embodiment of the present invention, and FIG. 2 is a diagram illustrating the principle of the present invention.

FIG. 2 is a diagram illustrating the principle of the present invention.

FIG. 3 is a diagram illustrating a defect of a conventional example.

4A and 4B are an external view and an operation state explanatory view showing a structure of a drive pulley as another embodiment of the present invention, and FIG.
Shows a conventional defect.

5A is a diagram for solving the problem of the present invention, and FIG. 5B is a diagram showing a method for solving the problem.

FIG. 6 is a schematic diagram of a conventional reader.

FIG. 7 is a perspective view showing the overall configuration of a conventional reading device.

[Explanation of symbols]

1 contact glass, 2 originals, 3 light sources, 4, 5,
6 mirror, 11 1st scanner, 12 2nd scanner, 13 motor, 15 drive pulley, 16 wire rope, 17, 18 horizontal idle pulley (correction pulley), 19 idle pulley.

Claims (3)

[Claims] 1. A scanner for reading a document set in a fixed position while moving it, a wire rope for moving the scanner, and a position fixing for winding the wire rope a plurality of times to transmit a driving force to the wire rope. In the image reading device, a drive pulley, a carriage pulley axially supported on an end surface of the scanner in the main scanning direction, and a fixed idle pulley arranged on the opposite side in the sub scanning direction with the carriage pulley interposed therebetween. A correction pulley whose rotation axis is orthogonal to each of the pulleys is rotatably arranged in a wire rope derivation path that is drawn out from the drive pulley or the idle pulley, and the wire rope is formed by the outer peripheral surface of the correction pulley. Image reading characterized in that the tensioned path of the wire rope is maintained as a regular path parallel to the sub-scanning direction by pressing. apparatus. 2. The drive pulley has a spiral groove for winding the wire rope on an outer peripheral surface of the drive pulley, and an axial interval and an inclination direction of each groove portion appearing on the outer peripheral surface of the drive pulley are corrected by the correction. 2. The image reading device according to claim 1, wherein the image reading devices are made different from each other so as to coincide with the approach angle of the wire rope led out from the pulley. 3. According to the variation of the derived length of the wire rope derived from the correction pulley to the drive pulley,
The image reading apparatus according to claim 2, wherein the output of a motor that drives the drive pulley is controlled to be changed.