JP2014103640A - Reading device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reading device capable of suppressing the occurrence of skew including deformation of a guide rail to accurately perform reading operation.SOLUTION: A reading device 201 reads an image of a document placed on a document platen with a reading unit that moves in a sub scanning direction. The reading unit 1 is mounted in a housing 202 accommodating the reading unit 1 slidably on a guide rail 2 extended along the sub scanning direction; the housing 202 includes therein height direction positioning guides 9A and 9B that are extended in the sub scanning direction at positions with an equal distance therebetween across a traction part of the reading unit in a main scanning direction; and the height direction positioning guides 9A and 9B have ends in the main scanning direction of the reading unit 1 slidably mounted thereon.

Description

  The present invention relates to a reading apparatus and an image forming apparatus, and more particularly to a positioning mechanism for a reading unit that optically reads a document placed on a document placement surface while moving it in the sub-scanning direction.

As is well known, the reading apparatus includes a document reading apparatus provided in an image forming apparatus such as a copying machine, a printer, or a facsimile machine.
In the document reading apparatus, in addition to a format in which scanning is performed by moving the document while the reading optical system is fixed, the document placed on the mounting table can be read by a carriage that moves in the sub-scanning direction. There is a scanning format by a scanner.
In the latter type, a configuration in which a carriage having a reading element arranged in the main scanning direction is moved along a guide rail extended in the sub-scanning direction in the housing of the reading apparatus that accommodates the carriage is known. (For example, Patent Document 1).

By the way, in the configuration in which the carriage is moved in the sub-scanning direction using the guide rail, a configuration that prevents the occurrence of skew, which is a phenomenon in which the reading element tilts in the main scanning direction, is used.
When the skew occurs, for example, a color image may have a color shift at the reading position due to a mismatch in the reading position in the sub-scanning direction.

Therefore, Patent Document 1 proposes the following configuration as a configuration for preventing the occurrence of skew.
In other words, a guide rail with a convex section extending in the sub-scanning direction is provided at the center of the main scanning direction on the frame of the reading device, and a part of the guide rail that is integral with the carriage is fitted into the guide rail. In such a state, a skew prevention structure is provided in a part of the fitting portion.

As the skew prevention structure, an inclined surface is provided on each of the guide rail and the inner surface of the guided member facing the position, and the horizontal component force generated when the guided portion is pressed against the inclined surface. It is the structure which eliminated the backlash between a to-be-guided part and a guide rail using.
In this configuration, since the surface facing the inclined surface of the guided portion is formed in the vertical direction, the play in the horizontal direction is eliminated, and the guide rail and the guided portion are caused by the horizontal component force generated in the inclined surface. It is possible to prevent the skew due to the tilt when the play occurs between the two.

In the configuration disclosed in Patent Document 1, skew is not generated by sandwiching the guide rail between the inclined surface of the guided portion and the vertical surface opposite thereto.
However, the frame provided with the guide rail may cause deformation such as shrinkage or warpage, which is referred to as sink, at the center of the bottom surface when an open top resin casing is used by molding. is there.

  If deformation occurs in the central portion of the bottom surface of the housing, the guide rail itself molded integrally with it also differs from the initial shape. For this reason, there is a possibility that rattling occurs on the contact surface between the guide rail and the guided portion, and the carriage is inclined to cause skew.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a reading apparatus and an image forming apparatus having a configuration capable of performing a reading operation with high accuracy by suppressing the occurrence of skew including deformation of a guide rail and the like in view of the problems in the conventional reading apparatus. Is to provide.

In order to achieve this object, the present invention provides a reading device that reads an image of a document placed on a document placement table by a reading unit that moves in the sub-scanning direction,
The reading unit is slidably mounted on a guide rail extending in the sub-scanning direction within a housing that accommodates the reading unit,
The inside of the housing includes a height direction positioning guide extended in the sub-scanning direction at equally spaced positions across the position of the guide rail in the main scanning direction,
The height direction positioning guide includes a reading device in which an end portion in the main scanning direction of the reading unit is slidably mounted.

  According to the present invention, the end of the reading unit slides along the height positioning guides provided at equal intervals across the traction part of the reading unit separately from the guide rail provided in the housing. . As a result, the frictional resistance generated at the end of the reading unit in the main scanning direction can be equalized and the moment when towed can be suppressed, and even when the guide rail is warped, the height positioning guide can The position facing the document image is optimized.

1 is an external view of an image forming apparatus to which a reading apparatus according to an embodiment is applied. 1 is an external view of a reading apparatus according to an embodiment. It is an external view which shows the internal structure in the reading apparatus shown in FIG. It is the external view which extracted the inside of the reading apparatus shown in FIG. It is a figure for demonstrating the tension mechanism of the traction member used for the reading apparatus shown in FIG. It is a figure for demonstrating one of the characteristic parts of the reader shown in FIG. It is a figure for demonstrating the relationship between the guide rail used for the characteristic part shown in FIG. 6, a skew prevention guide, and a traction part. It is an enlarged view of the characteristic part shown in FIG. It is a figure for demonstrating the deformation | transformation state of the housing | casing used for a reader. It is a top view for demonstrating an effect | action with the structure shown in FIG. It is a figure for demonstrating another effect | action with the structure shown in FIG. It is a figure for contrasting the effect | action shown in FIG. 11 with the conventional structure. It is a figure which shows the other prior art example explaining another Example regarding the guide rail used for the structure shown in FIG. It is a figure for demonstrating another characteristic for the structure shown in FIG. It is a figure for demonstrating the effect | action by the structure shown in FIG.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to embodiments shown in the drawings.
FIG. 1 is an external view of an image forming apparatus using the reading apparatus according to the present embodiment.
An image forming apparatus 100 shown in FIG. 1 is configured such that a reading device 102 is mounted on an upper surface of an apparatus main body 101 provided with an image forming processing unit, and a document conveying device 103 is mounted on the reading device 102.
Although not shown, an image forming unit that executes an electrophotographic copying process is provided inside the apparatus main body 101.

FIG. 2 is an external view of the reading device 102 extracted from FIG.
In FIG. 1, a reading apparatus 102 includes a scanner cover 201 and a casing 202 that forms the apparatus main body. The scanner cover 201 includes a contact glass 203 corresponding to a document placement table and a contact glass 204 for a document feeder. The document feeder contact glass 204 is a glass surface used when reading a document conveyed by the document conveying device 103.

FIG. 3 is an external view showing the inside of the housing 202 with the scanner cover 201 removed from the reading apparatus 102 shown in FIG.
In the figure, a housing 202 is a member that accommodates a reading unit 1 that can move in the sub-scanning direction. The housing 202 extends in the sub-scanning direction and can slidably mount the reading unit 1. A pulling member 3 that reciprocates the unit 1 in the sub-scanning direction is provided.
In the reading unit 1, a reading element 1 </ b> A such as an image sensor whose longitudinal direction is set in the main scanning direction is arranged facing the scanner cover 201 side.
The reading unit 1 moves in the sub-scanning direction, and receives light reflected from the document surface using a light source (not shown), thereby performing document image scanning in the main scanning and sub-scanning directions.
At the time of document scanning on the document feeder contact glass 204, the reading unit 1 scans an image of the document that is transported while being fixed at the position of the document feeder contact glass 204.

  The pulling member 3 includes an endless belt 3A integrated with a part of the reading unit 1 and pulleys 3B and 3C around which the endless belt 3A is wound. When the endless belt 3A moves, the reading unit 1 is interlocked.

FIG. 4 is a view for explaining the configuration of the pulling member 3.
In the same figure, the pulling member 3 is endless on pulleys 3B and 3C (the pulley 3C is shown in FIG. 4) disposed at both ends in the sub-scanning direction so as to have a stretched surface in the sub-scanning direction in the housing 202. A belt 3A is wound around.
One pulley 3 </ b> B is attached to the output shaft of the drive motor 4, and the endless belt 3 </ b> A can be reciprocated along the sub-scanning direction in accordance with forward / reverse drive of the drive motor 4.

A tension mechanism 5 is provided on the other pulley 3C as shown in FIG.
The tension mechanism 5 includes a tension spring 5B such as a compression coil spring disposed between one end portion of a bracket 5A that rotatably supports the other pulley 3C and a support portion 202A fixed to the housing 202 side. ing.
When the bracket 5A is pressed by the urging force of the tension spring 5B, tension is applied to the endless belt 3A.

The features of the present embodiment will be described as follows for the reading apparatus 102 having the above configuration.
The feature of the present embodiment is that the reading accuracy of the reading unit 1 is not lowered even when contraction deformation occurs in a part of the housing including the guide rail 2.
Configurations for exhibiting this feature are as described in (1) to (4).
(1) The attachment position of the pulling member 3 with respect to the reading unit 1 is made to correspond to the position of the center of gravity of the reading unit 1 in the main scanning direction.
As shown in FIG. 6, the endless belt 3 </ b> A used for the pulling member 3 is connected at the center of gravity of the reading unit 1 (the position indicated by the arrow Mg in FIG. 6) as the relationship between the reading unit 1 and the pulling member 3. Yes.
The reason why the center-of-gravity position Mg is shifted to the right rather than the center in the main scanning direction of the reading unit 1 is that the center of gravity is shifted due to the arrangement of cables and cable noise reduction cores (not shown) on the right side of the reading unit 1. The reason is.

(2) The cross-sectional shape of the skew prevention guide 6 mounted on the guide rail 2 that guides the reading unit 1 in the sub-scanning direction is a trapezoid, and the arrangement position of the skew prevention guide 6 is the center of the reading range by the reading element.
The guide rail 2 has a trapezoidal cross-sectional shape along the main scanning direction, and a skew prevention guide 6 provided on the lower surface of the reading unit 1 is fitted from the upper surface side thereof.
The skew prevention guide 6 is positioned so as to correspond to the center of the reading range in the main scanning direction of the reading element 1A provided in the reading unit 1. This configuration will be described with reference to FIG. 10, but is a configuration for reducing the amount by which the reading unit 1 is tilted.

FIG. 7 is a view for explaining the opposing relationship between the skew prevention guide 6 and the guide rail 2.
In the figure, the skew prevention guide 6 includes a slide shoe 6A having a trapezoidal inner surface corresponding to the shape of the guide rail 2 as a main part, and a support pin protruding from the bottom surface of the reading unit 1 on the upper surface of the slide shoe 6A. 7 is inserted.
The support pin 7 is fixed on the reading unit 1 side, and is supported on the slide shoe 6A side in a state where the slide shoe 6A can be raised and lowered.

  A spring 8 is disposed between the support pin 7 and the bottom surface of the reading unit 1. The spring 8 has a function of pressing the slide shoe 6A against the surface of the guide rail 2, and does not cause backlash between the guide rail 2 and the guide shoe 6A. By eliminating this backlash, the reading unit 1 is prevented from tilting in the main scanning direction so as not to generate so-called skew.

As shown in FIG. 8, the urging force of the spring 8, that is, the elastic force, is a spring 1 </ b> B that is used to urge the reading element 1 </ b> A in contact with the contact glass 203 (see FIG. 3) in the reading unit 1. The force is determined to be smaller than the combined value of the weights of the reading unit 1.
Note that the spring 1B that is the target of the summed value described in this case is arranged at a symmetrical position in the main scanning direction with the pulling portion of the reading unit 1 as a boundary, although not shown. In FIG. 8, the spring 1B of only one side is shown.
Therefore, in the reading unit 1, the reading element 1A is pressed evenly toward the contact glass 203 by the spring 1B on both sides in the main scanning direction. For this reason, the above-described total value targets the urging force of the spring 1B located on both sides in the main scanning direction and the weight of the reading unit 1. If this is a force larger than the combined value, when the reading unit 1 is pushed upward, it is lifted from height positioning guides 9A and 9B described later in FIGS. This is to prevent it. This prevents the driving of the reading unit 1 that occurs when the reading unit 1 is lifted from becoming unstable.

(3) The generation of moment is suppressed by reducing the distance between the pulling member 3 and the skew prevention guide 6.
The pulling member 3 and the skew prevention guide 6 are provided as close as possible to each other in the main scanning direction. Thereby, the generation of moment in the horizontal direction when a traction force acts on the reading unit 1 is suppressed, and the occurrence of skew is suppressed.

(4) Height positioning guides 9A and 9B are provided at equal intervals apart from the guide rail 2 with the attachment position of the pulling member 3 to the reading unit 1 in the main scanning direction.
In the housing 202 of the reading apparatus 102 equipped with the reading unit 1, height positioning guides 9 </ b> A and 9 </ b> B are provided on the end side in the main scanning direction across the pulling portion of the reading unit 1, in addition to the guide rail 2. Is provided.
As shown in FIGS. 6 and 8, the height positioning guides 9 </ b> A and 9 </ b> B are formed with convex portions arranged at equally spaced positions in the main scanning direction across the connecting position of the pulling member 3.
On the bottom surface of the reading unit 1, a sliding portion 1C mounted on the top surfaces of the height positioning guides 9A and 9B is provided at a position facing the height positioning guides 9A and 9B. As a result, the reading unit 1 can slide with the end portion in the main scanning direction positioned by the height positioning guides 9A and 9B.

  The height positioning guides 9A and 9B have the function of maintaining the facing distance between the reading unit 1 and the contact glass and not deteriorating the reading accuracy even when the height of the guide rail 2 is changed due to contraction deformation generated when the casing is molded. Have.

FIG. 9 is a diagram showing a deformed state when the casing 202 is injection-molded. In FIG. 9, a region where the warpage occurs more greatly as the blackness increases.
As shown in the figure, the greatest warpage occurs at approximately the center of the casing in the main scanning direction. For this reason, the guide rail 2 positioned corresponding to this position is affected by warpage, and the facing distance from the contact glass 204 changes. As a result, since the position of the skew prevention guide 6 in the height direction also changes from the initial condition, the facing positional relationship between the reading element 1A and the document image is deteriorated from an appropriate state.

  On the other hand, the occurrence of warpage is reduced at the arrangement positions of the height positioning guides 9A and 9B. For this reason, by mounting the reading unit 1 on these height positioning guides 9A and 9B, it is possible to prevent a change in the facing distance between the reading unit 1 and the document image in the height direction.

  When the guide rail 2 is warped, the slide shoe 6A can be displaced according to the deformation of the guide rail 2 by the urging of the tension spring 5B disposed between the slide shoe 6A and the reading unit 1. Thereby, the occurrence of skew is kept in a suppressed state.

  On the other hand, in FIG. 10, the height positioning guides 9A and 9B are subjected to the weight of the reading unit 1 and the reaction force of the spring 5C used to urge the contact glass 204 toward the contact force. Acts as fb. This frictional force acts evenly on both sides of the main scanning direction with respect to the force P that pulls the reading unit 1 in the direction of movement during scanning, and thus a force (moment that causes the reading unit 1 to tilt). ) Will be canceled. Thereby, the skew of the reading unit 1 is suppressed.

  If the height positioning guides 9A and 9B are not equidistant from the traction portion, the distance from the traction portion to any one of the height positioning guides 9A and 9B is different, so that the moment is related to the friction force and the distance. Differences will occur and skew will occur.

  The function of suppressing the generation of moment in the reading unit 1 described above also contributes to the fact that the position of the traction portion is the center of gravity of the reading element 1A. A moment is generated according to the distance from the.

The effect of setting the position of the pulling unit at the center of the reading range is to suppress a deviation amount from an ideal position (a position indicated by a symbol S in FIG. 11) when a skew (tilt) of the reading unit 1 occurs. There are things that can be done.
11 and 12, with the configuration of FIG. 6 as an object, when the reading unit 1 is skewed in the main scanning direction, the scanning position is from an ideal scanning position (indicated by reference numeral S in FIGS. 11 and 12). FIG. 11 shows a shifted state (indicated by symbol S1 in FIG. 11 and symbol S2 in FIG. 12).
The amount of deviation from the ideal scanning position S is affected by the position of the skew prevention guide 6 used in the pulling unit of the reading unit 1 with respect to the skew generation angle (α).
That is, as shown in FIG. 11, when the position of the traction unit is at the center of the reading range, as shown in FIG. 12, when the traction unit of the reading unit 1 is the end in the main scanning direction (right side in FIG. 12). In comparison, the amount of deviation from the ideal scanning position (S) can be kept small.
11 and 12, the amounts of deviation when the same skew angle (α) occurs are indicated by symbols P and P0. In the case of the configuration shown in FIG. 11, in the case shown in FIG. On the other hand, a relationship of P <P0 is obtained.
As described above, even when a skew occurs in the reading unit 1, by setting the position of the pulling portion of the reading unit 1 at the center of the reading range, the amount of deviation from the ideal scanning position can be reduced and the sub-scanning direction and the main scanning direction can be reduced. Reading errors in the scanning direction are reduced to prevent deterioration in reading accuracy.

Next, the features of the present embodiment will be described for the case where the shape of the guide rail 2 described above is a vertical plane.
FIG. 13 shows a guide rail (indicated by reference numeral 2 ′ for convenience) having a guide wall standing upright from the bottom surface of the housing 202. In this case, a pair of guide walls are provided to face each other in order to prevent the reading unit 1 from shifting in the horizontal direction. On these guide walls, a sliding surface 21 corresponding to a slide shoe is arranged so as to be able to face and abut the facing portion on the reading unit 1 side. Each sliding surface 21 is pressurized by a spring 22 to eliminate play in the horizontal direction.
In such a configuration, by providing a pair of guide walls, a space occupied by these guide walls is required.

On the other hand, in this embodiment, as shown in FIG. 14, one of the extended surfaces of the endless belt 3A that is wound around the pulleys 3B and 3C increases the tension. That is, one extended surface is projected outward from a line connecting the centers of the pulleys 3B and 3C, and the projected position is used as a pulling portion for the reading unit 1.
As a configuration in which one of the extended surfaces of the endless belt 3A is projected outward, a bypass pulley (not shown) of the endless belt on the side of the reading unit 1 corresponding to a position outside the line connecting the centers of the pulleys. ) Or the like is used.
Also in this case, the position of the pulling unit in the reading unit 1 is set to the center of the reading range of the reading element 1A, as in the case shown in FIG.

By using the configuration of the endless belt 3A shown in FIG. 14, the reading unit 1 generates a horizontal force Ft due to an increase in tension, as shown in FIG. A state where pressure is applied in one direction in the scanning direction is maintained.
As a result, the slide surface 20 ′ corresponding to the slide shoe provided facing the guide wall on the reading unit 1 side has only a force in one direction, so that the guide rail 2 ′ also receives the force Ft. It is only necessary to provide it.

  With the above-described configuration, it is not necessary to provide a pair of vertical surfaces as shown in FIG. When such a vertical surface is used, it is possible to improve the processing accuracy and die cutting accuracy when the casing 202 is formed. In addition, since the force on the vertical surface can be adjusted by the tension acting on the endless belt 3A, it is possible to reliably prevent rattling from occurring in the reading unit by reliably eliminating rattling from the vertical surface. Can do.

In this embodiment, as shown in FIGS. 6 and 7, the anti-skew guide 6 that slides in the fitted state or the opposing portion on the reading unit side that faces the guide wall as shown in FIG. 15. The slide surface 20 ′ can be a separate member from the reading unit 1.
Accordingly, the reading unit 1 can be smoothly moved by using a material having good sliding properties.
Also, the sliding portion 1C mounted on the top surfaces of the height positioning guides 9A and 9B can be fitted into a recess (not shown) formed on the top surfaces of the height positioning guides 9A and 9B. is there.
In this configuration, the inclination of the reading unit 1 can be more effectively suppressed by preventing it from coming out of the recess in a state where the sliding resistance is equalized.

DESCRIPTION OF SYMBOLS 1 Reading unit 1A Reading element 2 Guide rail 3 Pulling member 3A Endless belt 3B, 3C Pulley 5 Tension mechanism 9A, 9B Height positioning guide 201 Reading device 202 Case 203 Contact glass

Japanese Patent No. 4941386

Claims (10)

A reading device that reads an image of a document placed on a document placement table by a reading unit that moves in a sub-scanning direction,
The reading unit is slidably mounted on a guide rail extending in the sub-scanning direction within a housing that accommodates the reading unit,
In the casing, a height positioning guide extended in the sub-scanning direction at equidistant positions across the pulling portion of the reading unit in the main scanning direction is provided,
The height positioning guide is slidably mounted with an end portion in the main scanning direction of the reading unit.   The pulling member extended in the sub-scanning direction is attached to the reading unit, and the pulling member is connected at the center of gravity in the main scanning direction of the reading unit. Reading device.   3. The reading apparatus according to claim 1, wherein the height positioning guides are positioned at equal intervals in the main scanning direction with the attachment position of the pulling member interposed therebetween.   The reading apparatus according to claim 1, wherein the height positioning guide is positioned on an end portion side in the main scanning direction of the housing.   The reading unit is provided with a reading element having a longitudinal direction set along a main scanning direction, and the guide rail is positioned at the center of a reading range using the reading element. The reading device according to any one of 1 to 4.   The reading apparatus according to claim 1, wherein the guide rail has a trapezoidal cross-sectional shape along the main scanning direction. The pulling member includes a belt partially connected to the reading unit and having a stretched surface in the sub-scanning direction, and a pulley around which the belt is wound at both ends in the sub-scanning direction,
7. The reading apparatus according to claim 1, wherein one of the belt's extending surfaces has a tension increased in a main scanning direction.   The reading unit according to claim 7, wherein the reading unit is provided with a sliding portion having a vertical surface that can come into contact with a guide wall standing vertically from the bottom surface of the housing. apparatus.   The reading device according to claim 1, wherein the reading unit side facing portion capable of contacting the guide rail or the guide wall is formed by a member separate from the reading unit. .   An image forming apparatus using the reading device according to claim 1.

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