JP7480580B2 - Image reading device and image forming device - Google Patents

Description

The present invention relates to an image reading device and an image forming device, and in particular to an image reading device and an image forming device capable of reading images from a moving document and a stationary document.

Image reading devices, multifunction peripherals equipped with the same devices, and other image forming devices have traditionally often been equipped with a moving document image reading unit (document feeder scanner unit) that reads images by scanning the document surface of a passing document sheet in the main scanning direction at a predetermined position in the sheet transport path, and a stationary document image reading unit (flatbed scanner unit) that reads images by scanning the document surface of a stationary document sheet set on a flatbed reading surface in the main scanning direction and sub-scanning direction.

As examples of this type of conventional image reading device and image forming device, for example, Patent Documents 1 and 2 listed below describe a device in which a common optical scanning unit can move back and forth between a document feeder scanner section and a flatbed scanner section, and the optical scanning unit is slidably held by a guide rod and driven back and forth by a belt.

Patent Document 1 also discloses that when the optical scanning unit moves to the moving document reading position, a pair of protrusions are provided on one side wall surface of the optical scanning unit in the sub-scanning direction, which abut on both ends in the main scanning direction, and an expandable biasing means provided on one of the protrusions corrects the inclination of the optical scanning unit to the same direction as when reading a still image.

Patent document 2 discloses that, taking into consideration that the DF (document feeder) contact glass surface for reading moving document images is inclined relative to the FB (flatbed) contact glass surface for reading stationary document images, in order to maintain the optical scanning unit in a good position regardless of which contact glass it comes into contact with, a plurality of springs are provided between the optical scanning unit and a carriage slidably supported on a guide rod, and the optical scanning unit, which bias the optical scanning unit against the contact glass at both ends, thereby maintaining both ends of the optical scanning unit in a position that can be changed around the longitudinal axis and displaced vertically.

However, in the above conventional image reading devices and image forming devices, the optical scanning unit, which is a line image reading unit, is supported on a carriage and moves back and forth along a guide rod, so there is a minimum amount of play between the guide rod and the guide hole of the carriage that supports the optical scanning unit, which is necessary to guide the carriage so that it can slide. Therefore, when the optical scanning unit is biased to one side in the sub-scanning direction by the carriage drive belt, a tilt (angular displacement) occurs in the optical scanning unit in the drive direction, which causes the read image to be skewed.

To address this issue, for example, the inclination of the optical scanning unit can be reduced by increasing the axial length of the carriage guide hole, but this is detrimental to miniaturizing the device. Also, image processing can be used to correct image skew, but this leads to increased processing burden due to more complex processing software and increased memory consumption. Alternatively, it is possible to eliminate backlash by dividing the carriage guide hole into one and the other guide parts of the guide rod and providing a biasing means to bring the two guide parts closer to each other, but this leads to an increase in the number of parts and higher costs.

Furthermore, in the above conventional image reading device and image forming device, the home position of the optical scanning unit is set between the FB contact glass for reading stationary document images and the DF contact glass for reading moving document images, so when the optical scanning unit is moved from its home position to the FB contact glass side, the inclination direction of the optical scanning unit with respect to the guide rod is opposite to when it is moved to the DF contact glass side. This causes the problem of the skew direction of the read image being reversed.

The present invention was made in consideration of the above-mentioned conventional problems, and aims to provide an image reading device and an image forming device that can suppress the skew of the read image within a certain range by ensuring that the inclination of the line image reading unit is in the same direction and sufficiently suppressed regardless of which image reading area the line image reading unit is placed in.

In order to achieve the above object, the image reading device according to the present invention is an image reading device comprising a first document reading glass capable of reading an image of a stationary document, a second document reading glass capable of reading an image of a moving document, a line image reading unit movable in a sub-scanning direction along the first and second document reading glasses, guide means for guiding and supporting the line image reading unit so that it can move in the sub-scanning direction along the first and second document reading glasses, and drive means for driving the line image reading unit in the sub-scanning direction, and the line image reading unit is disposed at both ends of the line image reading unit in the main scanning direction relative to the document reading glass. The device further includes a biasing means for biasing with a predetermined biasing force, and is characterized in that the strength ratio of the biasing force of the biasing means at both ends of the line image reading unit changes when the line image reading unit is in a stationary document image reading area where the image of a stationary document is read through the first document reading glass and when the line image reading unit is in a moving document image reading area where the image of a moving document is read through the second document reading glass, so as to suppress tilt of the line image reading unit in the sub-scanning direction in response to the driving force from the driving means to the line image reading unit in the sub-scanning direction.

With this configuration, the strength ratio of the biasing forces of the biasing means at both ends of the line image reading unit is changed, which suppresses the tilt of the line image reading unit in the sub-scanning direction when it is driven in the sub-scanning direction by the driving force from the driving means, and makes it possible to make the tilt direction closer when the line image reading unit is in a stationary document image reading area where an image of a stationary document is read and when it is in a moving document image reading area where an image of a moving document is read.

The present invention provides an image reading device, an image forming device, and an image processing device that can suppress the skew of a read image within a certain range by ensuring that the inclination of the line image reading unit is in the same direction and sufficiently suppressed regardless of which image reading area the line image reading unit is placed in.

1 is a schematic configuration diagram of a main part of an image forming apparatus and an image transmitting/receiving apparatus each including an image reading device according to an embodiment of the present invention; 1 is a schematic perspective view of a main portion of an image reading device according to an embodiment of the present invention, showing a state in which the upper surfaces of a DF contact glass and an FB contact glass are open. 1 is a schematic front view, including a partial cross section, of a main portion of an image reading device according to an embodiment of the present invention, showing a state in which the upper sides of the DF contact glass and the FB contact glass are closed. 1A is a schematic top view showing the arrangement of a moving original image reading area and a stationary original image reading area of an image reading device according to one embodiment of the present invention, FIG. 1B is a schematic front view showing the state of a line image reading unit moving between the two reading areas, and FIG. 1C is a load/deflection characteristic diagram explaining the difference in characteristics between one and the other springs that urge both ends of the line image reading unit in the main scanning direction toward the contact glass. 5A is a schematic top view of a main part of a drive mechanism of a line image reading unit in an image reading apparatus according to one embodiment of the present invention, and FIG. 5B is a schematic front view of a main part of a portion B5 in FIG. 5A. 1A is a schematic top view illustrating the state of a line image reading unit in an image reading device according to one embodiment of the present invention when reading a still original image, FIG. 1B is a schematic front view showing the state of the line image reading unit, and FIG. 1C is a load/deflection characteristic diagram showing that the loads of one and the other springs that urge both ends of the line image reading unit toward the contact glass are equal when reading a still original image. 1A is a schematic top view illustrating the state of a line image reading unit in an image reading device according to one embodiment of the present invention when reading a moving original image, FIG. 1B is a schematic front view showing the state of the line image reading unit, and FIG. 1C is a load/deflection characteristic diagram showing the difference in magnitude of the load of one and the other springs that urge both ends of the line image reading unit toward the contact glass when reading a moving original image. 2 is a schematic top view showing the arrangement of a home position of a line image reading unit in an image reading apparatus according to an embodiment of the present invention; FIG. 9A is an explanatory diagram showing in an exaggerated manner the slight tilt to one side in the sub-scanning direction that occurs in a line image reading unit when reading a stationary original image and when reading a moving original image in an image reading device according to one embodiment of the present invention, and FIG. 9B is an enlarged plan view cross-sectional view of the main part of portion B9 in FIG. 9A. 10A is an explanatory diagram showing an exaggerated inclination to the other side of the sub-scanning direction that occurs in a line image reading unit when reading a moving original image in an image reading device of a comparative example, and FIG. 10B is an enlarged plan view cross-sectional view of the main part of portion B10 in FIG. 10A. FIG. 11 is a schematic front view of a main part of an image forming apparatus according to another embodiment of the present invention.

A preferred embodiment of the present invention will now be described with reference to the drawings.

(One embodiment)
1 to 9 show an embodiment of an image reading apparatus according to the present invention, and an image reading apparatus and an image forming apparatus each including the image reading apparatus.

First, we will explain the configuration of this embodiment.

In this embodiment, the image reading device of the present invention is applied to an automatic document feeder of a digital multifunction device of any type, such as an electrophotographic type or an inkjet recording type.

The digital multifunction machine 1 (image forming device, image transmitting/receiving device) of this embodiment combines the functions of a copier, printer, facsimile machine, scanner, etc., and can record and output full-color images or monochrome images on transfer paper or in a specified data format based on input data such as scanned image data. However, an image forming device equipped with the image reading device of the present invention may be any device that can perform an image reading function for a moving document, and an image transmitting/receiving device equipped with the image reading device of the present invention may be any device that has the function of transmitting and outputting and receiving and inputting scanned image data, etc.

As shown in Figures 1 and 2, the digital multifunction device 1 is an image forming device that includes a paper feed unit 2, an image forming unit 3, an image reading unit 4 (image reading device) equipped with an ADF 5 (automatic document feeder), and an operation panel 6.

The paper feed unit 2, although not shown in detail, has, for example, a paper feed cassette that stores cut-sheet-shaped recording paper, and a paper feed roller that picks up and feeds recording paper from the paper feed cassette. The paper feed unit 2 also has a paper feed path that includes various rollers that transport the picked-up recording paper to a predetermined image forming position in the image forming unit 3.

The image forming unit 3 is, for example, an electrophotographic type that includes a known exposure unit, a photoconductor, a developing device that uses four colors of toner: cyan (C), magenta (M), yellow (Y), and black (K), a transfer unit, a fixing unit, etc.

The image forming unit 3 can supply toner onto an electrostatic latent image formed by exposing a photoconductor to light based on the image read by the image reading unit 4, develop the image, transfer and fix the toner image onto recording paper, and output the recording paper with the color image printed thereon from the outlet 3a. Alternatively, the image forming unit 3 can generate an image file or image data in a specified format, store it in memory, or transmit and output it based on the image read by the image reading unit 4.

The image reading unit 4 is configured to be switchable between a DF scanner mode (moving document image reading mode) that cooperates with the ADF 5 to read the image of a moving document during automatic document transport, and a flatbed scanner mode (stationary document image reading mode) that reads the image of a stationary document placed on a flat FB contact glass (first document reading glass).

In the flatbed scanner mode, the image reading unit 4 can read the original image by irradiating light onto the image surface of an original sheet, book, etc. on the FB contact glass 41 and converting the reflected light from the image surface into an image signal.

In the DF scanner mode, the ADF 5 separates original sheets one by one from a stack of original sheets loaded on the original table 51, which is a sheet placement platform, and carries them into the original transport path 52, and transports them along the original transport path 52. During transport, the original sheets are sequentially arranged to face the DF contact glass 42 (second original reading glass) on the upper surface side of the image reading unit 4, starting from the upstream portion in the transport direction. In other words, the image reading unit 4 is able to function as a document feeder scanner by sequentially reading the images on the original sheets transported by the ADF 5 on the DF contact glass 42 of the image reading unit 4.

As shown in FIG. 2, the ADF 5 is attached to the rear of the top side of the image reading unit 4 via an opening/closing mechanism 1h such as a hinge so that it can be opened and closed. It can take an open position that exposes the FB contact glass 41 of the image reading unit 4, and a closed position in which the document on the FB contact glass 41 can be pressed against it as shown in FIG. 3.

As shown in FIG. 3, the ADF 5 is covered by a cover 55 that can be opened and closed at least at its upper part. This cover 55 forms a paper feed opening 55a above the end of the document table 51 on the paper feed side, and the main guide portion that forms the document transport path 52 from the paper feed opening 55a to the discharge opening 56 is formed by ribs or the like. The document transport rollers of the ADF 5 have a known configuration as described in Patent Documents 1 and 2, etc.

As shown in Figures 2 to 4, when the image reading unit 4 functions as a flatbed scanner for reading an image of a stationary document (placed document) and a document sheet to be read is placed, the FB contact glass 41 faces the image surface of the document sheet (hereinafter also referred to as the first document). Also, when the image reading unit 4 functions as a document feeder scanner for reading an image of a moving document (transported document), the DF contact glass 42 faces the image surface of the document sheet (hereinafter also referred to as the second document) passing through a predetermined reading position on the document transport path 52.

As shown in FIG. 4(b), in this embodiment, a typical example is shown in which the DF contact glass 42 is inclined to form a predetermined inclination angle θ (the inclination is exaggerated in the figure) with respect to the FB contact glass 41. However, it is also conceivable that an inclined surface or step is arranged on the underside of the intermediate cover 43 (see FIG. 2) that forms the scale portion 43a between the FB contact glass 41 and the DF contact glass 42, and both contact glasses 41, 42 are arranged parallel to each other.

As shown in Figures 4(a) and 4(b), the image reading unit 4 includes an image sensor head 4S and a drive mechanism 4M (drive means) that drives the image sensor head 4S in the sub-scanning direction (the X direction in Figure 4).

The image sensor head 4S can read the image of a stationary original placed on the FB contact glass 41 by line scanning the image surface of the original in the main scanning direction and moving in the sub-scanning direction. As shown in Figs. 4 and 5, the image sensor head 4S includes an integrated optical scanning unit 47 (line image reading unit) that can read the line image of the original by line scanning the image of the transported original in the main scanning direction, its carriage 48, and multiple compression coil springs 49A, 49B interposed between them, and the carriage 48 is guided movably in the sub-scanning direction by a guide rod 46 that extends in the sub-scanning direction.

The drive mechanism 4M includes a loop-shaped timing belt 44 connected to the carriage 48, a pair of timing pulleys 45 around which the timing belt 44 is stretched without slack, and a drive motor (not shown) that rotates one or both of the pair of timing pulleys 45 to move the image sensor head 4S in the sub-scanning direction via the timing belt 44.

Specifically, as shown in FIG. 5(b), the integrated optical scanning unit 47 of the image sensor head 4S is elastically supported on a carriage 48 guided by a guide rod 46 via a plurality of compression coil springs 49A, 49B (elastic members, biasing means). With the plurality of compression coil springs 49A, 49B assembled between the integrated optical scanning unit 47 and the carriage 48, the integrated optical scanning unit 47 slidably contacts with one of the FB contact glass 41, the DF contact glass 42, and the lower surface of the intermediate cover 43 with a predetermined contact pressure depending on its position in the sub-scanning direction, and is restricted from rotating around the axis of the guide rod 46.

The integrated optical scanning unit 47 is configured as a contact image sensor that holds, for example, a 1:1 imaging element roof mirror lens array, an optical path separation mirror, an 1:1 image sensor, an illumination light source, etc., in a molded frame. The integrated optical scanning unit 47 is configured to be able to line scan an image in the main scanning direction with high resolution and have a large focal depth that can also be used for image reading of book documents, etc. Note that the line image reading unit referred to in this invention is not limited to a specific type such as the integrated optical scanning unit 47, so long as it is configured to be compatible with a document feeder scanner and a flatbed scanner. The main scanning direction (Y direction in FIG. 4) is parallel to both the upper surface of the FB contact glass 41 and the upper surface of the DF contact glass 42.

The carriage 48 has, for example, a lower slider portion 48a (thrust guide) slidably supported on the guide rod 46, a pair of holding plate portions 48b that rotatably and vertically hold a pair of protrusions 47p that protrude from both ends of the integrated optical scanning unit 47 in the main scanning direction, and a carriage main body portion 48c to which the lower slider portion 48a and the pair of holding plate portions 48b are integrally attached.

The lower slider portion 48a is, for example, a generally cylindrical body fixed to the lower part of the longitudinal center of the carriage body portion 48c, and constitutes a guide means that, together with the guide rod 46, guides the carriage 48 to be movable in the sub-scanning direction. The pair of holding plate portions 48b are constituted by a pair of plate-like bodies with long holes 48h that protrude upward in the figure at both ends of the carriage body portion 48c. The inner peripheral portions at both ends of the lower slider portion 48a are provided with annular inner protrusions 48d with a generally triangular cross section whose axial width narrows toward the center.

The multiple compression coil springs 49A, 49B are incorporated between the carriage body 48c of the carriage 48 and both ends of the integrated optical scanning unit 47, forming a biasing means for biasing both ends of the integrated optical scanning unit 47 upward. When the integrated optical scanning unit 47 is in the flatbed reading area Z1 (stationary document image reading area, placed document reading area) shown in FIG. 4(a), the integrated optical scanning unit 47 is pressed against the FB contact glass 41 from the lower side of both ends, and when the integrated optical scanning unit 47 is in the DF reading area Z2 (moving document image reading area, document feeder scanner area) shown in FIG. 4(a), the integrated optical scanning unit 47 is pressed against the DF contact glass 42 from the lower side of both ends.

As shown in Figures 5(a) and 5(b), a plurality of upper slider parts 47b are attached to the upper part of both ends of the integrated optical scanning unit 47, which abut against the underside of either the FB contact glass 41 or the DF contact glass 42 and slide smoothly in the sub-scanning direction. These upper slider parts 47b extend in the longitudinal or lateral direction of the integrated optical scanning unit 47 and may be composed of a plurality of protrusions spaced apart from each other in a direction perpendicular to the extending direction. In addition, the upper slider parts 47b are preferably formed from a material that has a low friction coefficient, good sliding and gliding properties against the undersides of the FB contact glass 41 and the DF contact glass 42 or guide surfaces replacing them, and can be made without lubrication.

Thus, in this embodiment, the image reading unit 4 of the digital multifunction device 1 includes an FB contact glass 41 (first document reading glass) that reads images of stationary documents and a DF contact glass 42 (second document reading glass) that can read images of moving documents, an image sensor head 4S having an integrated optical scanning unit 47 and a carriage 48 that can move in the sub-scanning direction along the FB contact glass 41 and the DF contact glass 42, a guide rod 46 (guide means) that guides and supports the carriage 48 so that it can move in the sub-scanning direction along the FB contact glass 41 and the DF contact glass 42, and a drive mechanism 4M (drive means) that drives the integrated optical scanning unit 47 in the sub-scanning direction.

When the driving force F1 (see Figs. 4 and 6) in the sub-scanning direction from the driving mechanism 4M acts on the integrated optical scanning unit 47 of the image sensor head 4S in the image reading section 4, the multiple compression coil springs 49A and 49B as the biasing means bias the integrated optical scanning unit 47 against the FB contact glass 41 with a predetermined biasing force Ffb at both ends of the integrated optical scanning unit 47 in the main scanning direction, generating approximately equal resistance forces Ffb_x. On the other hand, when the driving force F2 (see Figs. 4 and 7) in the sub-scanning direction from the driving mechanism 4M acts on the integrated optical scanning unit 47 of the image sensor head 4S in the image reading section 4, the multiple compression coil springs 49A and 49B as the biasing means bias the integrated optical scanning unit 47 against the inclined DF contact glass 42 at both ends of the integrated optical scanning unit 47 in the main scanning direction, generating different resistance forces FAdf_x and FBdf_x.

In other words, as shown in FIG. 4(c), the compression coil springs 49A, 49B have different spring load change characteristics in response to changes in the amount of deflection, for example, by changing the wire diameter, coil diameter, material, etc. of the spring wire. When the amount of deflection is small in accordance with the large usage length Lfb (installation length) of the compression coil springs 49A, 49B in the flatbed reading area Z1, they generate approximately the same biasing force Ffb. On the other hand, when the amount of deflection is large in accordance with the small usage length Ldf of the compression coil springs 49A, 49B in the DF reading area Z2, they generate different biasing forces FAdf, FBdf.

Furthermore, in this embodiment, the force ratio of the compression coil springs 49A, 49B at both ends of the integrated optical scanning unit 47 changes when the integrated optical scanning unit 47 is in the flatbed reading area Z1 (static document image reading area) and when it is in the DF reading area Z2. Therefore, when the image sensor head 4S is driven by the driving force F2 in the sub-scanning direction from the driving mechanism 4M to move from the flatbed reading area Z1 to the DF reading area Z2, the integrated optical scanning unit 47 of the image sensor head 4S is prevented from tilting in the sub-scanning direction, and the direction in which the slight tilt can occur is prevented from being in the same direction as when it was in the flatbed reading area Z1 (see Figures 6 and 9).

In addition, in this embodiment, when the integrated optical scanning unit 47 is in the DF reading area Z2, the force ratio according to the deflection amount of the multiple compression coil springs 49A and 49B is set so that the biasing force of the compression coil spring 49A on one side of the integrated optical scanning unit 47 in the main scanning direction, on which the driving force F2 in the sub-scanning direction acts, is greater than the biasing force of the compression coil spring 49B on the other side of the main scanning direction. Therefore, when the image sensor head 4S is driven by the driving force F2 in the sub-scanning direction from the driving mechanism 4M to move from the flatbed reading area Z1 to the DF reading area Z2, the integrated optical scanning unit 47 of the image sensor head 4S is prevented from tilting in the sub-scanning direction, and the direction in which the slight tilt may occur is prevented from being in the same direction as when it was in the flatbed reading area Z1 (see Figures 6, 7, and 9).

In addition, the carriage 48 extends in the main scanning direction of the integrated optical scanning unit 47 and holds the integrated optical scanning unit 47 movably in the image reading direction through the FB contact glass 41 and the DF contact glass 42, and the multiple compression coil springs 49A, 49B, which are the biasing means, constitute one and the other elastic members interposed between the carriage 48 and the integrated optical scanning unit 47 at both ends of the integrated optical scanning unit 47 in the main scanning direction. Therefore, other elastic members such as rubber elastic bodies or leaf springs, or combinations thereof, can be used instead of the multiple compression coil springs 49A, 49B.

In particular, in this embodiment, the compression coil spring 49A, which is one of the elastic members, has a spring constant greater than the compression coil spring 49B, which is the other elastic member, and when the integrated optical scanning unit 47 is within the DF reading area Z2, the force ratio according to the amount of deflection of the compression coil springs 49A and 49B is set so that the force of the compression coil spring 49A is relatively large on one side of the main scanning direction of the integrated optical scanning unit 47 where the driving force F2 in the sub-scanning direction D2 acts, and the force of the compression coil spring 49B is relatively small on the other side of the main scanning direction. Therefore, for example, by appropriately differentiating the spring constants and mounting lengths of the compression coil springs 49A and 49B, it is possible to easily set the force ratio according to the amount of deflection as shown in FIG. 4(c).

As shown in FIG. 3, a second reading unit 69 that constitutes part of the guide surface on the vertically upper side of the straight transport path 61 is provided midway along the straight transport path 61 formed in the DF reading area Z2 and downstream of the position where the image sensor head 4S reads the image from the underside of the DF contact glass 42.

This second reading unit 69 is a back-side reading unit that reads the back image of the original sheet or small hard sheet immediately after the image on the front side of either the original sheet or small hard sheet is read by the image sensor head 4S.

The second reading unit 69 is configured in a manner substantially similar to the integrated optical scanning unit 47 of the image sensor head 4S, and has a back-side scanning area extending in the main scanning direction. This allows the second reading unit 69 to read images from the back side of an original sheet or small hard sheet that is transported in the sub-scanning direction so as to pass through the back-side scanning area. When reading of the back side image is not performed, the original sheet or slightly small hard sheet passes directly through the reading position of the second reading unit 69, and the second reading unit 69 functions only as part of the guide that forms the straight transport path 61.

The digital multifunction device 1 of this embodiment functions as an image forming device when the image read by the image reading unit 4 is printed on recording paper by the image forming unit 3 or output as image data, and functions as an image transmitting/receiving device when the image read by the image reading unit 4 is transmitted and output in a communication data format that allows image formation on the receiving side, or when such communication data is received from the outside.

Next, we'll explain how it works.

When the digital multifunction device 1 of this embodiment configured as described above is stopped, the image sensor head 4S is stopped, for example, at the home position HP shown in FIG. 8.

When reading a still document image, i.e., performing a reading operation in flatbed scanner mode, the image sensor head 4S moves from the home position HP to one side in the sub-scanning direction, for example, into the flatbed reading area Z1 on the right side in FIG. 8, and executes line scanning by the integrated optical scanning unit 47 for each small movement distance to read the image on the surface (bottom surface) of the document placed on the FB contact glass 41. Furthermore, when the reading operation is completed, the image sensor head 4S returns to the home position HP again.

On the other hand, when reading a moving document image, that is, when performing a reading operation in the DF scanner mode, the image sensor head 4S moves from the home position HP to one side in the sub-scanning direction, for example, into the DF reading area Z2 on the left side in FIG. 8. That is, the image sensor head 4S moves a preset distance from the home position to the other side in the sub-scanning direction and stops at the DF document reading position below the DF contact glass 42 (the position shown by the solid line in FIG. 3 and FIG. 4(b)), and reads the image on the surface of the transported document passing over the DF contact glass 42.

When an original sheet is set on the original table 51, the original sheet is detected by an original detection and/or size detection sensor, and the ADF 5 is ready to operate in the DF scanner mode. At this time, the image sensor head 4S moves from the home position HP to the DF original reading position (position shown by solid lines in Figures 3 and 4(b)) below the DF contact glass 42, and stops in the second reading position.

Next, when a switch operation input is made to start reading the document image, the transport drive motor and sensors of the ADF 5 are activated. Then, the document sheet is brought into the document transport path 52 and transported, and the surface image of the document sheet passing over the DF contact glass 42 is read by the image sensor head 4S according to the document transport state.

In this way, the image sensor head 4S can move in the sub-scanning direction so that it can be positioned below the FB contact glass 41 and below the DF contact glass 42, and the integrated optical scanning unit 47 changes its posture between a horizontal first reading posture (horizontal posture shown in Figures 6(a) and 6(b)) in which an image can be read through the FB contact glass 41 and an inclined second reading posture (inclined posture shown in Figures 7(a) and 7(b)) in which an image can be read through the DF contact glass 42, depending on its position in the sub-scanning direction.

The transport operation in the DF scanner mode is repeated until all normal original sheets set on the original table 51 are discharged. Then, when the transport operation in the DF scanner mode is completed, the image sensor head 4S returns to the home position again.

When a document sheet is placed on the FB contact glass 41 and a switch operation input is made to start reading the document image, operation in flatbed scanner mode is executed. That is, in response to the switch operation input, the image sensor head 4S moves from the home position HP to below the FB contact glass 41, and as described above, line scanning is performed by the integrated optical scanning unit 47 for each small movement distance to read the surface image of the document sheet.

When the card supply tray (not shown) of the ADF 5 is operated to the open position and a hard sheet is placed on the card supply tray, it is detected by the hard document detection sensor, and the ADF 5 becomes operable in the DF scanner mode that corresponds to hard sheets. At this time, the image sensor head 4S moves from the home position HP to the DF document reading position below the DF contact glass 42 and stops in the second reading position.

Next, when a switch operation input is made to start reading the image on the hard sheet, the transport drive motor and sensors of the ADF 5 are activated, and the hard sheet is transported into the straight transport path 61 and transported straight ahead. Then, depending on the document transport state, the surface image of the hard sheet passing over the DF contact glass 42 is read.

If double-sided image reading is required as a predefined document transport condition, the second reading unit 69 reads the backside image of the hard sheet in addition to the frontside image reading by the image sensor head 4S. In other words, one-pass simultaneous double-sided reading is performed. After image reading is completed, the hard sheet is discharged from the discharge port 56 to the discharge tray 53.

As described above, in this embodiment, the biasing means for pressing the integrated optical scanning unit 47 of the image sensor head 4S against the FB contact glass 41 and the DF contact glass 42 is composed of compression coil springs 49A, 49B that change the force ratio according to the amount of deflection at both ends of the integrated optical scanning unit 47. Therefore, when the integrated optical scanning unit 47 is reading a moving document (when reading from the document feeder), the frictional force when the integrated optical scanning unit 47 slides against the DF contact glass 42 and the reaction force from the DF contact glass 42 differ according to the force ratio of the compression coil springs 49A, 49B.

More specifically, during reading operation in flatbed scanner mode (hereinafter also referred to as FB reading), first, as shown in FIG. 9(a), the integrated optical scanning unit 47 is driven in the D1 direction (one side of the sub-scanning direction) by the driving force F1 from the timing belt 44.

At this time, the connection point J1 between the lower slider portion 48a of the carriage 48, which elastically supports the integrated optical scanning unit 47, and the timing belt 44 is pulled in the D1 direction via the compression coil springs 49A and 49B, and the lower slider portion 48a, which slidably fits into the guide rod 46, rotates in the clockwise direction in Figures 9(a) and 9(b) by the amount of backlash in accordance with the sliding clearance (backlash). It goes without saying that the inclination of the integrated optical scanning unit 47 and the lower slider portion 48a in the figures is exaggerated.

While maintaining this rotational position, the integrated optical scanning unit 47 moves in the D1 direction to read the image of the stationary document on the FB contact glass 41.

In this state, the biasing forces of the biasing springs 49A and 49B correspond to the long usable length Lfb shown in FIG. 6(b), and become a small spring pressure Ffb as shown in FIG. 6(c). Also, when the connection point J1 between the timing belt 44 and the lower slider portion 48a of the carriage 48 is located near the center of the longitudinal direction of the integrated optical scanning unit 47, the moment M1 that rotates the integrated optical scanning unit 47 in the clockwise direction in the figure is small and does not actually cause the integrated optical scanning unit 47 to tilt (rotate).

On the other hand, during reading operation in DF scanner mode (hereinafter also referred to as DF reading), the integrated optical scanning unit 47 is driven by a driving force F2 from the timing belt 44 in the direction D2 (the other side of the sub-scanning direction), which is the opposite direction to that during FB reading.

At this time, the connection point J1 between the lower slider portion 48a of the carriage 48 and the timing belt 44 is pulled in the direction D2, but since the DF contact glass 42 is inclined at a predetermined inclination angle θ with respect to the FB contact glass 41, while the image sensor head 4S moves from the imaginary line position to the solid line position in Figures 3 and 4(b) inside the image reading unit 4, the integrated optical scanning unit 47 changes from a horizontal position to an inclined position, and the multiple compression coil springs 49A, 49B are compressed, and their usable length becomes the short usable length Ldf. Therefore, the spring pressure forces FAdf and FBdf of the compression coil springs 49A, 49B differ depending on the usable length Ldf during DF reading.

Meanwhile, a component force is generated in a direction along the DF contact glass 42 in response to the spring pressure of the compression coil springs 49A, 49B, and a resistance force is generated in the sub-scanning direction (X direction in the figure) toward the D2 direction. If these resistance forces are FAdf_x and FBdf_x, a moment M3 whose magnitude is given by (FAdf_x-FBdf_x)*Ly based on the difference between the spring pressure forces FAdf and FBdf of the compression coil springs 49A, 49B is generated in the opposite direction to the moment M2 corresponding to the driving force F2 from the timing belt 44.

At this time, since the connection point J1 between the lower slider portion 48a of the carriage 48 and the timing belt 44 is located near the guide rod 46, the moment M2 is small, whereas the opposite moment M3 can be made large enough to tilt the integrated optical scanning unit 47 in the same direction as during FB reading by setting the force ratio and size of the compression coil springs 49A, 49B so as to exceed the weight of the carriage 48 and the static frictional force with the guide rod 46. Therefore, a torque can be generated that tilts the integrated optical scanning unit 47 along the DF contact glass 42 from the main scanning position perpendicular to the guide rod 46 to a rotational direction opposite to the moment M2.

The integrated optical scanning unit 47 is supported by the lower slider portion 48a of the carriage 48 so that it can slide relative to the guide rod 46. However, the relationship D>d is always required between the outer diameter d of the guide rod 46 and the shaft hole diameter D of the lower slider portion 48a in terms of product design and part processing that takes into account variations in part dimensions. Since clearance is also necessary for smooth sliding, a gap is generated between the guide rod 46 and the lower slider portion 48a.

Because of this gap, the integrated optical scanning unit 47 tilts in the direction in which it is pulled by the timing belt 44, and image skew (tilt in the main scanning direction) is usually unavoidable. In addition, the amount of tilt can be reduced by increasing the shaft hole thrust dimension L (bearing width) of the lower slider portion 48a of the carriage 48, but this is detrimental to miniaturization.

Of course, there is a method to correct image skew by image processing, but this would result in more complicated software and greater memory consumption. Also, it is possible to provide a pressing means or the like to eliminate gaps that cause tilt (see JP 2017-121034 A), but this would require a large number of parts and would be costly.

In contrast, in this embodiment, the home position HP of the integrated optical scanning unit 47 is between the DF contact glass 42 and the FB contact glass 41, and when the integrated optical scanning unit 47 of the image sensor head 4S moves from the home position HP into the flatbed reading area Z1 to read a stationary document image and when it moves from the home position HP into the DF reading area Z2 to read a moving document image, the driving forces F1 and F2 from the timing belt 44 are in the opposite directions. However, as shown in FIG. 9(a), the force ratio and spring pressure of the compression coil springs 49A and 49B are set so that the integrated optical scanning unit 47 rotates toward the flatbed reading area Z1 with a force that exceeds the weight of the carriage 48 and the static friction force with the guide rod 46 in the DF reading area Z2, so that the inclination of the integrated optical scanning unit 47 can be increased to the same direction as during FB reading. As a result, image skew can be suppressed and the direction of the skew can be prevented from varying.

(Comparative Example)
FIG. 10 illustrates an example of the inclination direction of the integrated optical scanning unit 47 during DF reading operation in a comparative example in which springs of the same specifications are used so that the force ratio between the compression coil springs 49A, 49B is always constant.

In this case, whether the integrated optical scanning unit 47 is on the flatbed reading area Z1 side or in the DF reading area Z2, the biasing forces of the multiple compression coil springs 49A, 49B on both ends of the integrated optical scanning unit 47 in the main scanning direction are approximately constant and in the same ratio, and no effective resistance moment is generated to counter the moment caused by the driving forces F1, F2 when the integrated optical scanning unit 47 is on the flatbed reading area Z1 side or in the DF reading area Z2.

As a result, when the integrated optical scanning unit 47 is in the flatbed reading area Z1, it is tilted clockwise corresponding to the driving force F1 as shown by the imaginary line in FIG. 10, and when it is in the DF reading area Z2, it is tilted counterclockwise corresponding to the driving force F2 as shown by the solid line in the figure, which means that the problem of the skew of the read image being in the opposite direction when reading a still image and when reading a moving document cannot be resolved.

Other Embodiments
FIG. 11 shows another embodiment of the image forming apparatus according to the present invention.

Note that this embodiment differs from the previously described embodiment in that the DF contact glass 42 is not inclined relative to the FB contact glass 41, and the method of making the force ratio of the compression coil springs 49A, 49B in the DF reading area Z2 different from the force ratio in the flatbed reading area Z1. However, in other respects, the overall configuration is substantially similar to that of the first embodiment. Therefore, for identical or similar configurations, the symbols of the corresponding components in the first embodiment will be used, and the differences from the first embodiment will be described below.

In this embodiment, a spring receiver 81 that can be raised and lowered along the carriage 48 is provided between the carriage 48 of the image sensor head 4S and the compression coil spring 49A at one end of the integrated optical scanning unit 47 in the main scanning direction, and a fixed spacer 82 that protrudes and can be inserted between the carriage 48 and the spring receiver 81 is provided from an inner wall 83 on the DF reading area Z2 side of the image reading unit 4.

In the image reading unit 4, when a driving force F1 (see FIG. 4(a)) in the sub-scanning direction from the driving mechanism 4M acts on the image sensor head 4S, a substantially equal resistance force Ffb_x (see FIG. 6(a)) is generated at both ends of the integrated optical scanning unit 47 in the main scanning direction as multiple compression coil springs 49A, 49B as biasing means bias the integrated optical scanning unit 47 against the FB contact glass 41 with a predetermined biasing force Ffb.

On the other hand, in the image reading section 4, when a driving force F2 (see FIG. 7(a)) in the sub-scanning direction from the driving mechanism 4M acts on the integrated optical scanning unit 47 of the image sensor head 4S, multiple compression coil springs 49A, 49B as biasing means bias the integrated optical scanning unit 47 against the DF contact glass 42 at both ends of the integrated optical scanning unit 47 in the main scanning direction, and a fixed spacer 82 is inserted between the carriage 48 and the spring receiver 81, thereby reducing the usable length of the compression coil spring 49A at one end of the integrated optical scanning unit 47 in the main scanning direction and increasing its amount of deflection.

On the other hand, as in the embodiment, the compression coil springs 49A and 49B have different spring load change characteristics in response to changes in the amount of deflection by changing the wire diameter, coil diameter, material, etc. of the spring wire. When the amount of deflection is small in response to the large usage length Lfb of the compression coil springs 49A and 49B in the flatbed reading area Z1, approximately the same biasing force Ffb is generated. When the amount of deflection is large on only one side in response to the small usage length Ldf of the compression coil spring 49A and the large usage length Lfb of the compression coil spring 49B in the DF reading area Z2, biasing forces FAdf, FBdf and resistance forces FAdf_x, FBdf_x (FAdf_x>FBdf_x) of different magnitudes are generated, approximately as in the embodiment shown in FIG. 7(a).

In this embodiment, too, the ratio of the biasing forces from the compression coil springs 49A, 49B at both ends of the integrated optical scanning unit 47 changes when the integrated optical scanning unit 47 is in the flatbed reading area Z1 (static document image reading area) and when it is in the DF reading area Z2. Therefore, when the image sensor head 4S is driven by the driving force F2 in the sub-scanning direction from the driving mechanism 4M to move from the flatbed reading area Z1 to the DF reading area Z2, the integrated optical scanning unit 47 of the image sensor head 4S is prevented from tilting in the sub-scanning direction, and the direction in which the slight tilt may occur is prevented from being in the same direction as when it was in the flatbed reading area Z1.

Therefore, this embodiment can achieve the same effects as the first embodiment.

In the above-mentioned embodiments, the lower slider portion 48a of the carriage 48 is generally cylindrical, but it may be generally U-shaped or concave, or may have a lid that closes the open end. Of course, the vertical guide position that restricts the movement of the integrated optical scanning unit 47 in the sub-scanning direction relative to the carriage 48 and the positions of the multiple compression coil springs 49A, 49B can be freely selected. Also, although there is only one guide rod 46 and one timing belt 44, there may be more than one, and it goes without saying that other sub-scanning direction drive means can be used instead of the timing belt.

As described above, the present invention provides an image reading device, image forming device, and image transmitting/receiving device that can suppress the skew of a read image within a certain range by ensuring that the inclination of the optical scanning unit is in the same direction and sufficiently suppressed regardless of which image reading area the optical scanning unit is placed in. The present invention is useful for image reading devices and image forming devices in general that are capable of reading images from both moving and stationary documents.

1. Digital multifunction machines (image forming devices, image transmitting/receiving devices)
1h Opening/Closing Mechanism 2 Paper Feeding Section 3 Image Forming Section 3a Exit 4 Image Reading Section 4M Driving Mechanism (Driving Means)
4S Image sensor head 5 ADF (automatic document feeder)
6 Operation panel 41 FB contact glass (flatbed contact glass, first document reading glass)
42 DF contact glass (document feeder contact glass, second document reading glass)
43 Intermediate cover 43a Scale portion 44 Timing belt (driving means)
45 Timing pulley (driving means)
46 Guide rod (guide means)
47 Integrated optical scanning unit (surface reading unit)
47b Upper slider portion 47p Projection portion 48 Carriage 48a Lower slider portion (guide means, thrust guide)
48b: holding plate portion 48c: carriage body portion 48d: annular inner protrusion 48h: oblong hole
49A Compression coil spring (one biasing means, one elastic member)
49B Compression coil spring (other biasing means, other elastic member)
51 Document table 52 Document transport path 53 Paper discharge tray 55 Cover 55a Paper feed port 56 Discharge port 61 Straight transport path 69 Second reading unit (rear side reading unit)
81: spring bearing 82: fixed spacer 83: inner wall D1 direction (one side in the sub-scanning direction)
D2 direction (other side in the sub-scanning direction)
F1, F2 Driving force FAdf_x, FBdf_x Resistance force FAdf, FBdf Spring pressure (biasing force)
J1 Connection point M1, M2 Moment M3 Resistance moment Z1 Flatbed reading area (static document image reading area, placed document reading area)
Z2 DF reading area (moving original image reading area, document feeder reading area)
θ Tilt angle

JP 2017-108284 A JP 2017-218273 A

Claims (6)

An image reading device comprising: a first document reading glass capable of reading an image of a stationary document; a second document reading glass capable of reading an image of a moving document; a line image reading unit movable in a sub-scanning direction along the first and second document reading glasses; guide means for guiding and supporting the line image reading unit so as to be movable in the sub-scanning direction along the first and second document reading glasses; and drive means for driving the line image reading unit in the sub-scanning direction,
the line image reading unit is further provided with one biasing means and another biasing means for biasing the line image reading unit toward the first and second document reading glasses at both ends of the line image reading unit in a main scanning direction,
An image reading device characterized in that the force ratio of the one and the other pressing means at both ends of the line image reading unit changes when the line image reading unit is within a stationary original image reading area where the line image reading unit reads an image of a stationary original through the first original reading glass and when the line image reading unit is within a moving original image reading area where the line image reading unit reads an image of a moving original through the second original reading glass, so as to suppress inclination of the line image reading unit in the sub-scanning direction in response to a driving force from the driving means to the line image reading unit in the sub-scanning direction. The image reading device according to claim 1, characterized in that, when the line image reading unit is within the stationary original image reading area , the one and the other urging means have a force ratio that is small enough that the urging forces of the one and the other urging means at both ends of the line image reading unit do not cause the line image reading unit to be tilted in the sub-scanning direction relative to the driving force of the line image reading unit in the sub-scanning direction, and that is equal to each other, while, when the line image reading unit is within a moving original image reading area where the image of a moving original is read through the second original reading glass, the urging force of the one urging means on one side of the main scanning direction of the line image reading unit where the driving force in the sub-scanning direction acts is greater than the urging force of the other urging means on the other side of the main scanning direction. a carriage is provided which extends in the main scanning direction of the line image reading unit and movably holds the line image reading unit in an image reading direction through the first document reading glass and the second document reading glass,
3. An image reading device as described in claim 1 or 2, characterized in that the one and other urging means have one and other elastic members interposed between the carriage and the line image reading unit at both ends of the line image reading unit in the main scanning direction. 4. The image reading device according to claim 3, characterized in that, when the line image reading unit is within a moving original image reading area in which an image of a moving original is read through the second original reading glass, the one elastic member elastically deforms more than the other elastic member, resulting in a force ratio in which the biasing force of the one biasing means on one side of the main scanning direction of the line image reading unit where a driving force in the sub-scanning direction acts is greater than the biasing force of the other biasing means on the other side of the main scanning direction. An image forming apparatus equipped with an image reading device according to any one of claims 1 to 4. An image transmitting/receiving device equipped with an image reading device according to any one of claims 1 to 4.