JP2005084551A - Pressure plate mechanism, automatic original feeding device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure plate mechanism, an automatic original feeding device and an image forming apparatus which is capable of enhancing both of picture quality and operability of pressure plate with a relatively simple method and obtaining a uniform force over all region of the area pressed by the pressure plate and, moreover, prevents the sticking of an original pressing member to a contact glass. <P>SOLUTION: The pressure plate mechanism in the image forming apparatus of reading the original, transferring an image of the original and performing image formation is provided with the pressure plate F which brings the original into pressurized contact with the contact glass 100. Therein, at least one part of the original pressing part of the pressure plate is composed of a soft hollow member 96 having a sealing performance into which the fluid filler 97 is sealed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a pressure plate mechanism, an automatic document feeder, and an image forming apparatus including the same in an image forming apparatus that reads an original and transfers an image of the original to form an image.

  2. Description of the Related Art Conventionally, an image reading apparatus that reads an image by moving a reading unit while a document is stationary on a contact glass is provided with a pressure plate unit for pressing the document against the contact glass.

For example, in a flat head scanner and a copying machine, there is a pressure plate that also serves as a cover for the contact glass of the scanner, or a pressure plate attached to the bottom surface of a sheet-through automatic document feeder (sheet-through ADF).
In such a configuration including a pressure plate that presses the original against the contact glass, the paper original with folds, waves, and curls must be pressed so as not to float from the contact glass.
Here, if a large float occurs, the read image will be stained or partially disturbed. Such a problem may occur when a gap is generated between the pressure plate and the scanner side contact glass due to variation in component dimensions or accumulation of tolerances. In particular, there is a relatively high concern about the occurrence of an ADF having a complicated structure.
Conventionally, in order to absorb a gap that may occur, a configuration in which a resin white sheet of a pressure plate is pressed by an elastic body having a sufficient stroke, for example, a soft cushion material such as a sponge or a leaf spring, is often used.
In addition, in order to apply a sufficient pressing force to the pressure plate, the hinge that supports the pressure plate unit has a closing force, or a magnet is used to magnetize the scanner side with the pressure plate unit closed. The structure to do is sometimes adopted.
However, as the pressure plate, it is desirable that the pressing force is uniform over the entire area of the pressure plate, but it is very difficult to equalize the pressing force by these methods. On the other hand, if a pressing force is applied to the pressure plate, the pressure plate unit becomes heavy when it is lifted, resulting in poor operability.
In addition, when the pressure plate sheet member and the contact glass are brought into close contact with each other, the smooth pressure plate sheet sticks to the contact glass, which not only deteriorates the operability of lifting but also forcibly lifts the scanner side, or There is also a concern that the platen unit will be damaged.
For the above reasons, image quality has been prioritized in the past, and the weight of operability is divisible, and for sticking to contact glass, the white sheet is embossed, or air is put into the gap. Measures such as sticking a convex member to the white sheet were necessary.
As described above, in order to obtain a good image quality, it is necessary to make the pressing plate pressing member uniformly adhere to the contact glass over the entire area, but this is very difficult by the conventional method using a cushion material or a spring. Then, the problem is that the operability of the pressure plate unit deteriorates.

FIG. 7 is a schematic view showing a typical pressure plate configuration together with a conventional seat-through ADF. FIG. 8 is a schematic view showing another conventional pressure plate configuration. First, in FIG. 7, the description of the sheet through ADF is omitted. The pressure plate is attached to the bottom of the ADF by pressure plate-ADF attachment means 93 attached to the resin sheet 92 by attaching a sponge sheet 95 and a resin sheet 92 to the back surface of the resin white sheet 94 with a double-sided adhesive tape.
In this case, the elastic force of the sponge sheet 95 aims to absorb the unevenness of the document pressing force due to component dimensional errors and mounting errors, but when the sponge sheet 95 is large and relatively thin, the stroke during compression is Since there are not so many, sufficient effect may not be acquired.
In FIG. 8, a pressure plate-ADF attachment means such as a sponge piece of about 15 to 20 or a leaf spring is attached to the back surface of a resin white plate 94a having rigidity and flatness comparable to contact glass. (Elastic member) 93a is attached to the bottom of the ADF.
By the sufficient stroke and elastic force of the pressure plate-ADF attachment means (elastic member) 93a, the non-uniform absorption of the document pressing force due to component dimensional error and attachment error is aimed. However, the influence of the finished part on the document pressing force, such as the flatness of the resin white plate 94a, is not limited.

7 and 8, theoretically, only the pressing force in the vicinity of the place where the pressure plate-ADF attachment means 93 and the pressure plate-ADF attachment means (elastic member) 93a are strong, and the other places are weak. Thus, in a strict sense, the document pressing force cannot be equalized.
Further, as a phenomenon common to both cases of FIGS. 7 and 8, the resin white sheet 94 or the resin white plate 94a may stick to the contact glass like a sucker. The same phenomenon is likely to occur when the resin white sheet 94 or the resin white plate 94a is warped and the center is convex in the opposite direction to the contact glass.
In response to this phenomenon, a convex portion having a height of about 0.5 mm is provided on the front side of the resin white sheet 94 or the resin white plate 94a so as to leave a minute gap with the contact glass. Measures to prevent sticking as described above may be taken by flowing in.
Here, the gap is minute and hardly affects the image reading quality, but it is not a desirable direction for the function of the pressure plate to hold the document so as not to float.
In order to solve the above problems, the object of the present invention is to achieve both the image quality and the operability of the pressure plate by a relatively simple method, and to obtain a uniform pressing force over the entire area pressed by the pressure plate. An object of the present invention is to provide a pressure plate mechanism, an automatic document feeder, and an image forming apparatus including the pressure plate mechanism that prevent the pressing member from sticking to the contact glass.

In order to solve the above-mentioned problem, the invention according to claim 1 is a pressure plate mechanism in an image forming apparatus that reads an original and transfers an image of the original to form an image to press the original against a contact glass. The pressure plate mechanism is characterized in that at least a part of the document pressing portion of the pressure plate is formed of a hermetically sealed soft hollow member in which a fluid filler is enclosed.
The invention according to claim 2 is characterized in that the hollow member is configured to directly press down the document.
The invention according to claim 3 is characterized in that the hollow member is configured to press the document through a soft white resin sheet.
The invention according to claim 4 is a configuration in which the hollow member or the support member to which the hollow member is attached is attached to the pressure plate side via at least one elastic member installed on the upper part of the hollow member. A pressure plate mechanism according to claims 1 to 3 is characterized.
The invention according to claim 5 is characterized in that the pressure plate mechanism according to any one of claims 1 to 4 is provided with an internal pressure adjusting mechanism that enables an internal pressure of the hollow member to be adjusted.
A sixth aspect of the present invention is characterized in that the pressure plate mechanism according to the fifth aspect is provided with an adjusting mechanism for adjusting an internal pressure by increasing or decreasing a fluid filler inside the document pressing member.
According to a seventh aspect of the invention, there is provided an automatic document feeder provided with the pressure plate mechanism according to any one of the first to sixth aspects.
According to an eighth aspect of the present invention, there is provided an image forming apparatus including the automatic document feeder according to the fifth aspect.

  According to the present invention, since the pressure of the fluid filling material enclosed in the soft hollow member is used, even if there is no pressing force of the pressing force by other means, the entire area of the area pressed by the soft hollow member is uniform. It is possible to obtain a sufficient pressing force and to prevent the document pressing member from sticking to the contact glass.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention relates to a pressure plate mechanism for pressing an original on the contact glass in an image reading apparatus that reads an image by moving the reading means while the original is stationary on the contact glass.
Examples of the image reading apparatus include a flat head scanner and a copying machine, each of which is attached to a pressure plate that also serves as a contact glass cover of the scanner or a bottom surface of a sheet through type automatic document feeder (sheet through ADF). A pressure plate is provided.
In the following description, the case of the seat-through ADF, which has the most complicated structure, will be taken up, and the basic configuration, operation, action, and embodiment of the present invention will be described.
FIG. 1 is a sectional view showing an automatic document feeder to which the present invention is applied. FIG. 2 is a control block diagram of the automatic document feeder shown in FIG. With reference to FIG. 1 and FIG. 2, the processing operation for a bundle of documents of the same size will be described first.
The automatic document feeder includes a document setting unit 1 for setting a document bundle to be read, a separation feeding unit 2 for separating and feeding documents one by one from the set document bundle, and primary abutting alignment of the fed documents. And a resist unit 3 that draws out and conveys the document after alignment.
The automatic document feeder also turns the document to be conveyed, turns the document surface toward the reading side (downward), and reads the surface image of the document from below the contact glass. A first reading / conveying unit 5 and a second reading / conveying unit 6 for reading a back side image of a document after reading are configured.
The automatic document feeder further includes a paper discharge unit 7 that feeds a document whose front and back scanning has been completed to the outside of the machine or a reversing unit, a reversing unit 8 that performs reversing for rereading, and stacks and holds a document after the reading is completed. The stacking unit 9, the driving units 101 to 104 that drive these conveying operations, and the controller 100 that controls a series of operations.

The original bundle 13 to be read is set on the original setting table 10 with the leading end abutting the broken line position of the original stopper 25, and the width direction of the original bundle 13 is set to the side guide 11 (only one is shown in the front and rear directions). The positioning in the direction orthogonal to the conveyance direction is performed.
In this state, the document set detection filler 21 is displaced from the broken line position to the solid line position. Accordingly, the shielding of the document set detection sensor 28 is released, and when the document set is detected, the document set detection sensor 21 is detected via the I / F unit 107. A document set signal is transmitted to the main body control unit 111.
Further, the document length detection sensor 12 or 14 provided on the document table surface (a reflection type sensor or an actuator type sensor that can detect even one document is used) can be used to approximate the length of the document in the conveyance direction. It is determined (a sensor arrangement capable of determining at least whether the document size is vertical or horizontal is necessary).
Thereafter, a document feed operation is executed by a document feed signal (a signal input from an operation unit (not shown) and instructed from the main body control unit to the controller 100 via the I / F unit 107).
The document stopper 25 is retracted to the solid line position by the CW (forward rotation) drive of the drive unit (calling motor) 101 (in this embodiment, it is a stepping motor but can also be realized by a solenoid) to open the leading edge of the document.
Thereafter, the pickup roller 20 is moved from the position indicated by the broken line to the upper surface of the document indicated by the solid line by the reverse drive of the drive unit (calling motor) 101 (in this embodiment, it is a stepping motor but can be a solenoid) and is pressed with a predetermined force. Is done. The home position sensor 19 is a sensor for detecting the states of the pickup roller 20 and the document stopper 25.
During the pressure contact operation of the pickup roller 20, when the number of documents is small, the drop impact sound of the pickup roller 20 is generated due to the large drop height and the small cushioning action of the document between the document setting table 10 and the pickup roller 20. A bug that becomes larger occurs.
As a solution, a concave roller relief is formed at the contact point of the document setting table 10 with the pickup roller 20 so that the pickup roller 20 does not strike the document setting table 10 directly.

Thereafter, after a predetermined time, a drive unit (paper feed motor) 102 that drives the separation feeding unit 2 and the registration unit 3 rotates in the CW (forward rotation) direction, and the pickup roller 20 rotates in the clockwise direction, so that the original bundle 13 Is fed in the direction of the separator 2.
At this time, the paper feeding belt 23 is stretched around the belt pulleys 22 and 24 with a predetermined tension, and is in pressure contact with the separation roller 26 provided oppositely.
The separation roller 26 is friction-driven via a torque limiter (not shown) having a predetermined magnitude of torque, and is in a state of being engaged with the paper feeding belt 23 or via a single document. Then, the sheet feeding belt 23 is rotated counterclockwise.
In the unlikely event that two or more originals enter between the paper feeding belt 23 and the separation roller 26, the follower force is set to be lower than the torque of the torque limiter. It rotates in the clockwise direction, which is the driving direction, and works to push back excess originals, thereby preventing double feeding.
The original separated into one sheet by the action of the paper feed belt 23 and the separation roller 26 is further fed by the paper feed belt 23 and advances through the paper feed path 27. In this process, the abutting sensor 29 detects the tip and further abuts against the pull-out roller 31 that has stopped.
After that, a predetermined distance is fed from the detection of the abutting sensor 29, and as a result, the drive unit 102 is reversed by being pressed against the pull-out roller 31 with a predetermined amount of deflection. The driving of the paper belt 23 is stopped.
At this time, by rotating the drive unit 101 in the CCW (reverse rotation) direction, the pickup roller 20 is retracted from the upper surface of the document, and the document is fed only by the conveying force of the paper feeding belt 23, so that the leading end of the document is pulled out by the pullout roller 31. The roller 30 enters the nip of the upper and lower roller pairs, and the tip is aligned (skew correction).
Thereafter, the pull-out roller 31 is driven by the reverse rotation of the drive unit 102 to convey the document in the direction of the turn unit 4. Here, when feeding the first sheet of the original bundle to the registration stop position, the conveyance speed of the pull-out roller 31 is set higher than the reading speed, and the reading conveyance roller 43 is also driven by the drive unit (reading motor) 103. Drive at high speed.

In the case of the second and subsequent sheets, the form of first advance of the next document is taken. Since the reading conveyance roller 43 during reading of the document image is driven by the driving unit 103 at a speed corresponding to the reading magnification instructed from the main body control unit 111, the conveyance speed of the next original is the same as the speed of the reading conveyance roller 43. It must be fed into the nip between the reading conveyance roller 43 and the pressure roller 35.
Therefore, when the trailing edge of the original document being read passes through the abutting sensor 29, the first count conveyance of the next original document is started while monitoring the progress of the trailing edge of the original document being read by starting a pulse count for controlling the sheet interval. To do.
First, the pickup roller 20 is brought into pressure contact with the upper surface of the next original by the forward rotation of the drive unit 101, and then the drive unit 102 is driven to rotate forward and is conveyed until it contacts the stopped pull-out roller 31.
Here, the rear end position of the document being read is calculated from the inter-sheet pulse count value, and the drive unit 102 is driven in reverse when the paper advances from the pull-out roller 31 by a predetermined interval. The pull-out roller 31 is driven at a high speed similarly to the first sheet, and is fed to the tip detection sensor 34 at this speed.
It is decelerated to the reading speed (speed of the reading conveyance roller 43) by the detection of the leading end detection sensor 34. By performing this operation between successive original sheets, it is possible to recover the time stopped by the original abutting operation and maintain a predetermined original interval.
Further, the width of the document leading edge past the pull-out roller 31 is detected by the size detection sensor 32 in the direction orthogonal to the conveyance direction. When an accurate document size is determined by a combination of the width signal and the length signal obtained by the document length detection sensor 12 or 14, a document size signal is sent from the controller 100 to the main body control unit 111. / F part 107 is transmitted.
Thereafter, the document advances to the nip between the reading conveyance roller 43 and the pressure roller 35, stops at a position where a predetermined pulse is conveyed from the detection of the registration sensor 40, and transmits a registration stop signal to the main body control unit 111. It waits for the input of a reading start signal from 111 (a signal transmitted when synchronization with transfer paper or preparation for storage in the image memory is completed).

Next, an original reading operation is executed by inputting a reading start signal. The document whose registration is stopped is sent to the first reading and conveying unit 5 by the reading and conveying roller 43 and the pressure roller 41 that are rotated by the normal rotation driving of the driving unit (reading motor) 103.
The driving speed of the driving unit (reading motor) 103 at this time is determined based on information transmitted from the main body control unit 111 to the controller 100 based on a reading magnification input from a main body operation unit (not shown).
In the first reading conveyance unit 5, the document is conveyed between the reading glass 54 and the white background plate 51 disposed on the upper surface thereof with a predetermined interval. During this time, an image is read by a reading system (not shown), is electrically converted via a CCD, and is stored in a memory device (not shown).
The reading / conveying unit 5 is provided with a means for making the conveyance gap as narrow as possible and reducing the degree of freedom of the document as much as possible. As such a method, a method of projecting a flexible guide member from the inner surface of the reading entrance guide 42 toward the white background plate 51 and filling the gap is effective.
Further, the white background plate 51 is pressed onto the reading glass 54 with a predetermined elasticity with a gap of about 0.5 mm ± 0.2 mm, and errors in the reading depth direction are also suppressed.

The surface of the reading glass 54 is treated with a surface active agent (silicon-based activator) so that the ink does not adhere or adhere to the surface. Further, the above-mentioned flexible guide is extended to the vicinity of the reading point.
The document surface is not positively brought into contact with the reading glass 54 at the reading point position, and the front end of the document can be wiped near the reading point of the reading glass 54 (the action of scraping off foreign matter on the glass surface at the leading end). ing.
The timing at which the leading edge of the document reaches the reading and conveying unit 5 is controlled by the pulse count of the driving unit 103, and a surface DF gate signal indicating a surface image effective reading region in the sub-scanning direction is transmitted at that timing. Thereafter, the document advances while being read, and is fed to the intermediate conveyance pressure roller 53 through the pickup guide 52.
Since the pressure roller 41 and the intermediate conveyance pressure roller 53 are driven by the reading conveyance roller 43 in common, the feeding speed and the drawing speed are the same, which has the effect of reducing the occurrence of a delivery shock.
The document sent out from the first reading and conveying unit 5 by the intermediate conveying and pressing roller 53 is sent to the second reading and conveying unit 6 and is in close contact with the contact image sensor 61 arranged with the reading unit facing downward from the upper surface. It passes between the pressing members 62 arranged on the reading surface of the image sensor 61 with a predetermined pressure and a predetermined interval.

In the duplex mode, the timing at which the leading edge of the document reaches the contact image sensor 61 is controlled by the conveyance pulse count from the detection of the leading edge of the registration sensor, and at this timing, the effective reading area of the back image is transmitted to the contact sensor unit.
Based on this signal, an image of the surface corresponding to the back side of the document is read, electrically converted to the same as the front side, temporarily stored in a frame memory unit (not shown), and then transferred to the main body control unit 111. The pressing member 62 serves as a reference for shading and serves as a white background plate.
The pressing member 62 can be formed of a rotating body in addition to the plate-shaped guide member shown in FIG. The timing of ending the document reading area on the front and back sides is controlled by a pulse count from the time when the trailing edge of the document is detected by the registration sensor.
Thereafter, the original is discharged to the stack unit 9 by a pair of paper discharge rollers 71 and 72 including a paper discharge driving roller 71 and a paper discharge pressure roller 72. The sheet discharge stacker 90 is configured to be high on the downstream side, and contributes to preventing the discharged document from jumping out and improving the stack document alignment accuracy.
During continuous reading of a plurality of originals, the drive unit (reading motor) 103 is stopped by the registration stop operation by first advance of the original after the original discharge completion timing. When the reading motor is restarted, the discharge end signal is transmitted to the main body control unit 111 when the trailing edge of the document leaves the discharge sensor.
When a small-size document is stacked, the reversing switching claw 80 of the reversing unit 8 is switched to the state indicated by the broken line by the driving unit (reversing switching solenoid) 105, and the document is conveyed to the reversing path 85.
The paper is discharged from a pair of reverse conveying rollers 81 and 82 including a reverse paper discharge driving roller 81 and a reverse paper discharge driven roller 82 onto a small size dedicated stacker 91 configured as a part on the document stacker 90. This improves the visibility after discharging a small-size document.
In addition, the document setting table 10 is configured so as to be able to rotate upwards with the rotation fulcrum 15 as the center, thereby improving the stack document extraction performance. When the document is discharged, the operation of the reverse switching claw 80 is synchronized with the trailing edge of the discharged document. Immediately after the document is discharged, the reverse switching claw 80 is rotated in the direction of the broken line by the drive unit 105 to Control is performed to hit the trailing edge and prevent the trailing edge of the discharged document from remaining.

The above is an overview of the processing for single-sided or double-sided originals with the same size original bundle. Next, processing of single-sided and double-sided originals when sizes are mixed will be described.
When mixed sizes are used, the document lengths are mixed and cannot be determined by the document length detection sensors 12 and 14 on the table. Therefore, after separating the documents into one sheet, the trailing edge of the document is separated from the sheet bundle. The size can be determined only when it becomes completely independent.
For this reason, when it is desired to determine the document size before reading, the document path configuration is ½ or more of the maximum document length between the first document trailing edge detection position after separation and the registration sensor position before reading. It is necessary to set the length.
If this is satisfied, there is a disadvantage that the document setting position needs to be greatly separated from the reading position, and the portion including the document table 10 and the conveyance path becomes large, and the entire apparatus becomes wide. Therefore, in order to make the apparatus small, it is necessary to devise a method for detecting the document length when mixed loading.
As a countermeasure, if the document size cannot be determined before the start of reading at the time of mixed loading, the reading is not performed at the first conveyance, the paper is passed only for reading the size, and the second reading is performed via the reversing unit. A method is adopted in which the front and back surfaces are read simultaneously when passing.
In this case, the conveyance operation until the first registration stop is the same as when a document of the same size is bundled, but the operation after receiving the read start signal transmitted from the main body control unit 111 (particularly the processing after the discharge unit 7). Different.

When the paper is discharged after passing through the reading unit, the reverse switching claw 80 is moved in the direction of the broken line by the drive unit (reverse switching solenoid) 105 before the leading edge of the document protrudes from the pair of paper discharge rollers 71 and 72 to reverse the document. It feeds to the path 85 side.
Thereafter, the original is fed by the reverse discharge roller pair 81, 82 driven by the drive unit (reverse motor) 104 until the rear end of the original passes the discharge roller pair 71, 72. This control is performed by pulse count from the paper discharge sensor 70.
After the document is stopped, the reverse switching claw 80 is moved in the solid line direction by the drive unit 105 and the rear end of the document is directed in the nip direction of the reverse conveying roller. Thereafter, the reverse paper discharge driving roller 81 rotates in the counterclockwise direction, and the document end (initial state) is placed at the nip portion of the reverse roller pair 71 and 83 composed of the stopped paper discharge drive roller 71 and the reverse upper roller 83. The leading edge skew matching operation is performed.
Thereafter, the reverse roller pair 71, 83 starts feeding by the driving unit 103, and is sent again to the first reading conveyance unit 5 and the second reading conveyance unit 6 through the turn unit 4, and reading of the front and back sides is performed.
At this time, since the document is in a state where the back side and the front side are reversed, the reading order is the back side and the front side is read later, so the back side gate on signal is transmitted first, and then the front side gate signal on signal is transmitted. . Based on this signal, a page order change process is performed on the image processing apparatus side.
This completes the reading operation. However, if the sheet is discharged as it is, the page order will be out of order.
In addition, the conveyance for only the size reading and the conveyance for only the page alignment are configured so as to be sent at the highest conveyance speed of the apparatus for the conveyance operation not involving reading of the image, thereby reducing the loss time. ing.

Next, a configuration that does not include the second reading conveyance unit 6 will be described. Although FIG. 1 shows a configuration having a contact image sensor 61 for handling double-sided originals, this reading device is expensive, and double-sided original processing using a reversing mechanism is possible even without this device. It is. This type is expected to increase in actual products.
The document whose front surface has been read by the reading operation in the first reading and conveying unit 5 is conveyed to the first reading and conveying unit 5 again through the reversing unit 8 and the back side is read. The paper is discharged onto the document stacker 90 through reverse discharge.
As described above, in an apparatus having no second reading / conveying unit 6, productivity is lowered when a double-sided copy is made from a double-sided original. As a countermeasure, a method is adopted in which a plurality of originals are fed into the unit and image reading and reverse document discharge are alternately combined to reduce a paper loss.
First, the first original is fed, and one page of image is read by the first reading / conveying unit 5, which is sent to the reversing unit 8, and after abutting alignment with the pair of reversing rollers 71, 83, the first document is read again. The first reading conveyance unit 5 is sent to perform reading of the second page, and is sent to the reversing unit 8 in order to align the page order at the time of paper discharge.
Before and after this, the second original is fed, and the first reading conveyance unit 5 reads the third page. Subsequently, reverse discharge of the first original is executed. Subsequently, the fourth page of the second original is read. Thereafter, the second original is sent to the reversing unit 8, the third original is sent before and after this, the fifth page is read, and then the second original is reversed and discharged.
In this way, by performing the process between the reverse reading operation of the document that has already been read between the reading of the front surface and the reading of the back surface, the loss time between papers of the reverse discharging operation without reading is minimized. It is possible to stay. Note that this processing can be performed only on a document having a size that fits between the pair of reverse conveyance rollers 81 and 82 and the registration sensor 40.

FIG. 3 is a schematic view illustrating a pressure plate mechanism according to the present invention. FIG. 4 is a schematic view showing a first stage in the process of closing the ADF in the pressure plate mechanism of FIG. FIG. 5 is a schematic view showing a second stage in the process of closing the ADF in the pressure plate mechanism of FIG. FIG. 6 is a schematic view showing filling of the soft member.
In FIG. 3, an appropriate amount of fluid filler 97 is sealed inside the soft hollow member 96 and sealed. The upper side of the soft hollow member 96 is attached to a back plate 99 which is a support member having moderate rigidity.
The pressure plate-ADF attachment means (elastic member) 93a attached to the back plate 99 is attached to the bottom of the ADF. Further, a relatively thin resin white sheet 94 used for an existing pressure plate is attached to the lower side of the soft hollow member 96.
Here, if the material of the soft hollow member 96 has durability, light reflection characteristics, and cleaning properties that are suitable for the purpose of pressing the document, the soft white member 94 does not exist and the soft hollow member 96 does not exist. The configuration may be such that 96 directly presses the document.
Here, it is considered that the fluid filler 97 filled in the soft hollow member 96 is optimally a gas such as an inert gas or air, but a liquid such as an aqueous solution, a chemical solution, or oil, It may be a semi-solid such as a gel.
In addition, as long as sufficient apparent fluidity can be obtained, the filler 97 may be a fine granular solid such as resin beads or powder. At this time, since the soft hollow member 96 becomes convex toward the contact glass side by the fluid filler 97, the soft hollow member 96 does not stick to the contact glass like a suction cup as in the conventional example.

In the embodiment of the present invention shown in FIG. 3, as shown in FIGS. 4 and 5, there is no positional relationship in which the soft hollow member 96 contacts the contact glass 100 evenly when the ADF is closed. That is, there is a difference in the left and right heights A and B.
However, even in such a case, the fluid filler 97 filled in the soft hollow member 96 flows, and finally the soft hollow member 96 or the resin white sheet 94 is fluid. The contact glass 100 is pressed evenly over the entire contact area by the pressure of a certain filler 97.
Using the pressure of the fluid filler 97 enclosed in the soft hollow member 96, even if the pressing force is not biased by other means, the pressing force is uniform over the entire area of the soft hollow member 96. And the sticking of the document pressing member to the contact glass 100 can be prevented.
Note that the pressure plate-ADF attachment means (elastic member) 93a attached to the back plate 99 presses the soft hollow member 96 through the back plate 99 by the elastic force as in the function of the prior art. .
Since the soft hollow member 96 itself also serves as a document pressing member, the number of parts can be reduced and simplified, and low cost and high reliability regarding parts production can be obtained.
The soft hollow member 96 does not directly press the document, but by pressing the document through the document pressing member that has been proven so far, high reliability can be obtained with respect to the document pressing function, and a plurality of elastic members can be used in combination. Thus, an optimum document pressing function that is difficult to obtain with only the soft hollow member 96 is also obtained.
By adjusting the internal pressure of the soft hollow member 96, it is possible to provide an optimal document pressing function that does not depend on the initial state, and the internal pressure adjustment of the soft hollow member 96 can be performed by an internal pressure adjusting valve in a simple and low-cost manner. .
Furthermore, in the present invention, a pressure adjusting mechanism for adjusting the pressure by the flowable filler 97 filling the inside of the soft hollow member 96 is provided, and an embodiment thereof is shown. As an example of the pressure adjustment mechanism, there is a pressure adjustment mechanism by increasing or decreasing the filling amount of the fluid filler 97.
For example, if the fluid filling material 97 is gas, liquid, or gel, as shown in FIG. 6, a rubber adjustment valve 98 is provided, and the filling amount is adjusted with a syringe 101 or the like, so The power can be adjusted.

1 is a cross-sectional view showing an automatic document feeder to which the present invention is applied. FIG. 2 is a control block diagram of the automatic document feeder in FIG. 1. Schematic explaining a pressure plate mechanism according to the present invention. Schematic which shows the 1st step of the process which closes ADF in the pressure plate mechanism of FIG. Schematic which shows the 1st step of the process which closes ADF in the pressure plate mechanism of FIG. Schematic which shows filling of a soft member. Schematic which shows the typical pressure plate structure with the conventional sheet through ADF. Schematic which shows the other conventional pressure plate structure.

Explanation of symbols

93a Elastic member (pressure plate-ADF attachment means)
94 White sheet made of resin 96 Soft hollow member (document holding member)
97 Filling material with fluidity 98 Internal pressure adjustment mechanism (pressure adjustment valve)
100 contact glass C pressure plate mechanism D image forming device E automatic document feeder F pressure plate

Claims (8)

  In a pressure plate mechanism in an image forming apparatus that reads an original and transfers an image of the original to form an image, the pressure plate mechanism includes a pressure plate that presses the original against a contact glass, and at least a part of the original pressing portion of the pressure plate is fluid. A pressure plate mechanism comprising a soft hollow member having a sealing property in which a filler is enclosed.   The pressure plate mechanism according to claim 1, wherein the hollow member directly presses the document.   2. The pressure plate mechanism according to claim 1, wherein the hollow member is configured to hold the document through a soft white resin sheet.   2. The structure according to claim 1, wherein the hollow member or the support member to which the hollow member is attached is attached to the pressure plate side via at least one elastic member installed on an upper portion of the hollow member. 3. The pressure plate mechanism according to 3.   The pressure plate mechanism according to claim 1, further comprising an internal pressure adjustment mechanism that enables adjustment of an internal pressure of the hollow member.   6. The pressure plate mechanism according to claim 5, further comprising an adjustment mechanism for adjusting an internal pressure by increasing or decreasing a fluid filler inside the document pressing member.   An automatic document feeder comprising the pressure plate mechanism according to any one of claims 1 to 6.   An image forming apparatus comprising the automatic document feeder according to claim 5.

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