JPH11223887A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent failure from occurring because the frame of a device main body part is deflected in the case of pressing a book document and the deflected part comes in contact with a scanner mechanism. SOLUTION: This device is provided with a strain gauge 10 attached to the frame 6 as a detection means for detecting deformation amount caused by deflection, a warning means 12 giving a warning message, and a controller 11 receiving the deformation amount as an electrical signal from the detection means and starting the warning means. When the detection means detects the deformation amount exceeding the specified tolerance, the warning message showing that pressing is excessive is displayed on a display device 12 through the controller 11. Thus, a user avoids the excessive pressing so as to prevent the failure that the work of the scanner mechanism 9 is disturbed because the frame 6 comes in contact with the scanner mechanism 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a copying machine and a printer, and more particularly to an image forming apparatus having an automatic document feeder.

[0002]

2. Description of the Related Art In a conventional image forming apparatus, an original is automatically transported to an exposure position on a contact glass and is exposed by a scanner mechanism, and then the original on the contact glass is discharged to a discharge tray. An image forming apparatus provided with a feeding device (hereinafter, referred to as “ADF”) is well known. In general, an image forming apparatus including an ADF has a configuration in which a pressure plate is integrated with the ADF. Such a pressure plate is heavy because it has a large number of components such as a document table, a discharge tray, and each transport roller, and is made of a strong member for supporting it.

In an image forming apparatus having such an ADF, when a thick original such as a book original is subjected to pressure plate copying, the thick book original is pressed due to the high weight and high rigidity of the pressure plate in which the ADF is mounted. In such a case, the following problem occurs.

FIG. 6 shows a schematic configuration diagram of a conventional image forming apparatus. The pressure plate 1 has an ADF inside, and is rotatably attached to a hinge 4 on the back side of the apparatus main body 3, and presses a book original 7 set on a contact glass 5 from above during copying. And fix it. Then, the book document 7 is exposed by a light source (not shown) of the scanner mechanism 9 in the scanner unit 8, and an image is read. The light source moves immediately below the contact glass 5 and scans and illuminates the book document 7.
It is read line by line. The contact glass 5 is held by the frame 6 of the apparatus main body 3 at the peripheral edge.

[0005] In the pressing plate copy, the set book original 7 is strongly pressed by the pressing plate 1 so that the original surface is sufficiently adhered to the contact glass 5. At this time, if the pressing force is excessive, the frame 6 supporting the book document 7 and the contact glass 5 bends downward.

FIG. 7 shows a state of bending of the frame 6 in the image forming apparatus of FIG. As shown in this figure, the tip of the flexed frame 6 is quite close to the scanner mechanism 9. As described above, the scanner mechanism 9 includes the light source that moves directly below the contact glass 5, the mirror, and the like, and its operation is precisely controlled to obtain accurate image information. Therefore, depending on the amount of the deflection, the scanner mechanism 9 contacts the scanner mechanism 9 and hinders its operation. In particular, as shown in FIG. 6, when the document setting position is the back reference position close to the hinge part 4, a problem easily occurs.

[0007]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus capable of keeping the deformation due to the bending of the frame within a certain range and preventing the occurrence of a malfunction of the scanner mechanism. is there.

[0008]

SUMMARY OF THE INVENTION An image forming apparatus according to the present invention includes a pressure plate for fixing an original on a contact glass, and a supporting means for rotatably supporting the pressure plate on a main body of the apparatus. In, a detecting means for detecting the load on the frame of the device body due to the descent of the pressure plate,
Preventing means for preventing the load from increasing.

Preferably, the detecting means detects a deformation amount of the frame holding the contact glass, and more preferably, a strain gauge attached to the frame.

The prevention means comprises a support portion formed on the apparatus main body, a supported portion formed on the pressure plate, and an elastic member, and the support portion loosely fits the supported portion. Preferably, the supported portion is urged toward the apparatus body by the elastic member.

The supporting means may be provided with a locking means for locking the rotation of the pressure plate in the descending direction by the upward movement of the supported portion. Further, the locking means comprises a sector gear fixed to the supported portion and an L-shaped lever rotatably supported by the support portion. When one of the L-shaped levers moves upward, the one of the L-shaped levers rises together with the supported portion, and when the load exceeds a predetermined value, the other of the L-shaped levers engages with the sector gear to suppress the lowering of the pressure plate. It can be.

[0012] The detecting means may detect upward movement of the supported portion. Further, the prevention means includes a warning means for issuing a warning message, and a control device, and when the detection means detects a load exceeding a predetermined value, the warning means is activated via the control device. You can also.

Further, the control device may be configured to temporarily stop the image forming operation of the apparatus main body together with the activation of the warning means.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of an image forming apparatus according to a first embodiment of the present invention. In the image forming apparatus shown in FIG. 1, the ADF and the pressure plate 1 are integrated with each other, and are rotatably supported by a support means 4 on the upper back side of the apparatus main body 3. The support means 4 is configured such that a hinge bracket 4a fixed to the apparatus main body 3 and a hinge shaft 4b fixed to the pressure plate 1 are rotatably fitted. Further, in the apparatus main body 3, a part of the frame 6 protrudes below the contact glass 5, and the contact glass 5 is supported from below by its peripheral edge to keep a horizontal surface.

In the platen copy mode, the user
The book document 7 is set on the contact glass 5, the platen 1 is lowered, and the book document 7 is fixed between the contact glass 5 and the platen 1. When a copy start button (not shown) is turned on, a light source (not shown) of a scanner mechanism 9 in the scanner unit 8 scans and irradiates the set book original 7 while moving along the contact glass 5 with respect to the set original 7. I do. The image information read here is delivered as reflected light to an image forming unit via a mirror and a lens (not shown).

As shown in FIG. 1, when copying a thick original such as a book original 7, the user applies a force F1 from above with the pressure plate 1 in order to keep the original surface sufficiently open. Add. At this time, due to the high weight and high rigidity of the pressure plate 1, a force F2 is applied to the frame 6 supporting the book document 7 and the contact glass 5.

When pressing with the pressure plate 1 depending on the thickness of the document, the user tends to apply excessive pressure with the pressure plate 1 because the pressure plate 1 is not horizontal. In particular, when the book document 7 is set at a position close to the support means 4 as in the present embodiment, the angle of the pressure plate 1 becomes large, and the frame 6 receiving the force F2 receives an excessive load and withstands this. It is easy to bend.

The image forming apparatus of this embodiment includes a strain gauge 10 as a means for detecting a load applied to the frame 6 in order to detect a deformation amount of the bending due to the force F2.
It is stuck on the bent part of the frame 6. As the attachment position, a portion that is easily deformed is selected in consideration of the shape of the frame 6 and the like. The strain gauge 10 can detect the amount of deformation of the frame 6 as a change in an electric signal.

On the other hand, as schematically shown in FIG.
As a preventive means for indirectly preventing an increase in load due to the control unit 2, the device main unit 3 includes a control device 11 disposed in the electrical unit.
And a warning unit including a display device 12 provided in the operation unit.

In the above configuration, the amount of deformation obtained by the detection means is sent to the control device 11 as an electric signal. When the amount of deformation of the frame 6 exceeds a certain range, the control device 1
1 determines that the amount of deformation due to the bending has reached a predetermined value, and causes the display device 12 to display a warning message on the panel of the operation unit indicating that the pressing is excessive.

The user who sees this display notices that the force F1 applied to the pressure plate 1 is excessive. Then, when the user empirically knows the pressing force to be slightly reduced and to what extent the force is allowed, the bending of the frame 6 exceeds a certain range, and the frame 6 is moved to the scanner mechanism 9.
Can be avoided, and the malfunction of the scanner mechanism 9 can be prevented.

The warning means is not limited to displaying the warning message on a panel of an operation unit (not shown), and may be a warning means for calling a user's attention by a buzzer sound or the like.

In place of the means for indirectly preventing an increase in the load through the user's operation as described above, the control device 11 controls the image forming operation of the apparatus body at the same time as the activation of the warning means. As a means of preventing suspension,
Critical failure of the scanner mechanism 9 is prevented beforehand.
Furthermore, if the warning means and the means for stopping the image forming operation are used in combination, the reliability is further improved.

In the above embodiment, the detecting means is:
Since the amount of deformation of the frame 6 is detected by the strain gauge 10, it is not limited to the case where the book document 7 is pressed and fixed by the pressure plate 1, and the book document 7 is directly used by the user himself without using the pressure plate 1. Can be detected by pressing the frame 6 against the contact glass 5.

The detecting means using the strain gauge 10 does not require a complicated structure, and the warning means only needs to be displayed on an existing display.
Therefore, there is an advantage that the influence of the surrounding layout change is small.

FIG. 2 shows a schematic configuration of an image forming apparatus according to a second embodiment of the present invention. This image forming apparatus includes:
The support means 22 includes a hinge bracket 22a as a support portion for supporting the pressure plate 1, and a hinge shaft 22b and a bearing portion 22d as supported portions supported by the support portion. Other configurations are the same as those of the image forming apparatus of the first embodiment.

In the support means 22, a hinge bracket 22a is formed as a support part on the upper rear side of the apparatus main body 3, and this hinge bracket 22a allows the supported part formed on the pressure plate 1 to have play in the vertical direction. It is loosely fitted. That is, the hinge bracket 22a includes a bearing portion 22d that rotatably receives the hinge shaft 22b.
It has a long hole 22c for making it movable within a certain range only in the vertical direction. Due to the configuration of the support means 22, the pressure plate 1 can be freely moved in the vertical direction within a certain range at the rear end.

Further, the hinge bracket 22a is provided with a bearing 22d on the side of the main body of the apparatus, that is, a slot 22.
c, a spring member which is an elastic member for urging the member downward.
e is provided. As the spring member 22e, for example, there is a coil spring shown in the drawing. This spring member 2
By 2e, the axial position at the time of rotation of the pressure plate 1 in the normal state is positioned at the lower end of the long hole 22c.

At the time of pressing plate copy, when a thick document such as a book document 7 is placed on the contact glass 5 and the platen 1 descends and the book document 7 begins to be pressed, a force F2 is applied to the frame 6 by the pressing force. Occurs. When the pressing is further continued, the pressing plate 1 generates a reaction force F3 in which the rear portion of the pressing plate 1 is directed upward with the upper portion 26 of the book document 7 as a fulcrum. Here, the supported portion starts to move upward against the urging force of the spring member 22e due to the reaction force F3.

FIG. 3 shows a schematic configuration of the image forming apparatus of FIG. 2 in a state where the supported portion of the support means 22 is moving upward. The pressing force from the pressure plate 1 is
It is released by the upward movement in 2c, and as a result, an increase in the force F2 transmitted to the frame 6 can be suppressed.

Therefore, in the image forming apparatus having the support means 22, the support portion starts to move upward before the force F2 is applied so that the deformation amount of the frame 6 exceeds the allowable range. By suppressing the increase in F2, the deformation of the frame 6 due to the overload and the trouble of the scanner mechanism 9 due to this are prevented. The spring coefficient of the spring member 22e is set in consideration of the weight of the pressure plate 1 in which the ADF is mounted, the rigidity of the frame 6, and the like.

Further, the upward movement of the support portion makes the pressure platen 1 approach a horizontal plane when pressed, so that the book document 7 can be relatively easily fixed to the spread. If the pressing plate 1 at the time of pressing slightly approaches the horizontal plane, when the book document 7 is set on the back side on the contact glass 5 (especially, when the document reference position is the back reference), excessive pressing is likely to be performed, It is effective to avoid this.

The supporting means 22 temporarily prevents the force F2 from increasing when the pressing of the pressure plate 1 is continued with an excessive force. Therefore, the spring member 22e shrinks completely, and the supported portion is
After reaching the upper end of c, an increase in the load on the frame 6 cannot be suppressed. Therefore, the supporting means 2
In addition to 2, it is desirable to use a detecting means for detecting the load applied to the frame 6 as shown in the first embodiment and a preventing means for giving a warning to a user via a control device.

In this case, a detection switch may be provided above the elongated hole 22c of the hinge bracket 22a as the detection means. In this detection switch, the supported portion has a long hole 22c.
When it moves upward along the axis and reaches the upper end, O
N. As described above, the load of the frame 6 can be detected by the indirect detection means using the reaction force F3. Further, as in the first embodiment, a detecting means for directly detecting the deformation amount of the frame 6 with a strain gauge may be provided. Further, it is possible to use a prevention unit that activates a warning unit or stops an image forming operation from the detection unit via the control device.

Next, a description will be given of a case where the support means 22 is provided with a locking means for locking the rotation of the pressure plate 1 in the downward direction by the upward movement of the supported portion in the image forming apparatus of this embodiment.

FIG. 4 is an enlarged view of the structure of the support means 22. The locking means is an L-shaped lever 27 rotatably attached to the hinge bracket 22a as a locking tool.
And a sector gear 28 fixed to the hinge shaft 22b as a locked member.

The L-shaped lever 27 has a hinge shaft 2 at one end thereof.
At the other end, which is attached at the center thereof so as to urge the 2d from above, and protrudes toward the hollow, a locking claw 27a which is bent at the tip and is flush with the sector gear 28 is provided.
have. On the other hand, the sector gear 28 having a large number of teeth on the periphery is fixed to the hinge shaft 22b and rotates integrally with the pressure plate 1.

A book manuscript is placed on the contact glass,
When excessive pressing is performed on the pressure plate 1, the supported portion including the hinge shaft 22b starts to move upward as described above. With this upward movement, one end of the L-shaped lever 27 rises,
It rotates in the direction of arrow 29. At the same time, L-shaped lever 2
7 is at the other end of the teeth of the sector gear 28.
Engagement locks the rotation of the sector gear 28 in the direction of the arrow 30.

FIG. 5 shows the support means 22 in a state where the rotation of the pressure plate 1 is locked. As described above, when the L-shaped lever 27 locks the sector gear 28, the lowering of the hinge shaft 22b that fixes the sector gear 28 and the pressure plate 1 that fixes the hinge shaft 22b are locked. Accordingly, even if the user continuously presses, the pressing force is not transmitted to the frame 6 shown in FIG. 3, and the increase in the load applied to the frame 6 is completely suppressed. Therefore, troubles such as hindering the driving of the scanner function are reliably prevented.

The angle of the pressure plate 1 at the time when the supported portion starts to move upward depends on the thickness of the document. Therefore, as shown in the figure, the sector gear 28 is formed by forming a large number of teeth in a predetermined range of the peripheral edge thereof, so that the rotation of the pressure plate 1 can be locked within a certain range of angle. .

After the locking by the locking means, when the force on the pressure plate 1 in the descending direction is relaxed, the support portion moves downward by its own weight and returns to the original position. At the same time, the L-shaped lever 27 for urging the hinge shaft 22b also rotates back to the original position, so that the locking claw 27a
Is released from the sector gear 28 and the lock is released. Thus, the locking means locks only in the descending direction, and this lock is released naturally when the user releases the force.

Although the above embodiment has been described with reference to an image forming apparatus in which an ADF is built in a pressure plate, a similar configuration may be provided in an image forming apparatus having no ADF. Even in such an apparatus, there is a case where excessive pressing is performed by a user (for example, a case where a very thick and heavy original is copied), and the same effect is exerted in this case.

[0043]

According to the image forming apparatus of the present invention, there are provided detecting means for detecting a load applied to the frame of the apparatus main body due to lowering of the pressure plate, and preventing means for preventing the load from increasing. It is possible to prevent the operation of the scanner mechanism from being hindered by deformation due to the bending of the frame.

Further, according to the structure in which the detecting means detects the amount of deformation of the frame by using a strain gauge for the frame, the structure is simple, so that there is no influence on the surrounding layout. The load can be detected not only at the time of pressing.

Further, the prevention means may be a support means, wherein the support part has a resilient member for loosely fitting the supported part in a vertically movable manner and biasing the supported part downward. For example, an increase in the load on the frame due to the upward movement of the supported portion can be temporarily prevented.

Further, according to the structure in which the supporting means is provided with the locking means for locking the downward movement of the pressure plate by the upward movement of the supported portion, the lowering of the pressure plate is achieved by the lock.
The increase in the load on the frame is completely suppressed, and the malfunction of the scanner mechanism is reliably prevented.

Further, according to the above-mentioned prevention means, according to the structure having the warning means for issuing a warning message, a large change of the device structure is not required, and the influence on the surrounding layout is small.

Further, according to the prevention means for temporarily stopping the image forming operation of the apparatus main body together with the activation of the warning means, the malfunction of the scanner mechanism is more reliably prevented.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a schematic configuration of a main part of an image forming apparatus according to a first embodiment of the invention.

FIG. 2 is a diagram schematically illustrating a main configuration of an image forming apparatus according to a second embodiment of the present invention.

FIG. 3 is a view showing a state in which a supported portion of a support means is moving upward in a second embodiment.

FIG. 4 is an enlarged view showing a configuration of a supporting means provided with a locking means for locking the rotation of the pressure plate.

FIG. 5 is a view showing the support unit of FIG. 4 in a state where the rotation of the pressure plate is locked;

FIG. 6 is a diagram illustrating a schematic configuration of a conventional image forming apparatus.

FIG. 7 is a diagram illustrating a state of bending of a frame in the image forming apparatus of FIG. 6;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 pressure plate 3 device main body 4 support means 5 contact glass 6 frame 10 strain gauge 11 control device 12 display device (warning means) 22a hinge bracket (support portion) 22b hinge shaft (supported portion) 22d bearing portion (supported portion) 22e Spring member 27 L-shaped lever 28 Sector gear

Claims (9)

[Claims] 1. An image forming apparatus comprising: a pressure plate for fixing a document on a contact glass; and support means for rotatably supporting the pressure plate on an apparatus main body. An image forming apparatus comprising: detecting means for detecting a load on a frame; and preventing means for preventing an increase in the load. 2. An image forming apparatus according to claim 1, wherein said detecting means detects a deformation amount of said frame holding said contact glass. 3. The image forming apparatus according to claim 2, wherein the one that detects the amount of deformation is a strain gauge attached to the frame. 4. The apparatus according to claim 1, wherein the preventing means comprises a support portion formed on the apparatus main body, a supported portion formed on the pressure plate, and an elastic member, and the support portion loosely fits the supported portion. 2. The image forming apparatus according to claim 1, wherein the supported portion is urged toward the apparatus main body by the elastic member. 5. An image forming apparatus according to claim 4, wherein said support means includes locking means for locking rotation of said pressure plate in a downward direction by upward movement of said supported portion. 6. The locking means comprises a sector gear fixed to the supported portion, and an L-shaped lever rotatably supported by the support portion, wherein the load is increased when the pressure plate is lowered. When the supported portion moves upward, one of the L-shaped levers rises together with the supported portion, and when the load exceeds a predetermined value, the other of the L-shaped levers engages with the sector gear to suppress the lowering of the pressure plate. The image forming apparatus according to claim 5, wherein: 7. The image forming apparatus according to claim 4, wherein said detecting means detects the upward movement of said supported portion. 8. The prevention means comprises: a warning means for issuing a warning message; and a control device. When the detection means detects a load exceeding a predetermined value, the warning means is activated via the control device. 2. The method according to claim 1, wherein
8. The image forming apparatus according to any one of claims 1 to 7, 9. The image forming apparatus according to claim 8, wherein the control device temporarily stops the image forming operation of the apparatus main body together with the activation of the warning unit.