JP2007197162A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the deformation of a lower conveyance guide even if a user inserts a paper feeding cassette without returning the lower conveyance guide to an original holding position erroneously. <P>SOLUTION: When the paper feeding cassette 7 is pulled out of a device body 1A, the tip 86a of the lower conveyance guide 86 in a sheet refeeding and reconveying part 80 turns in a storage region K for the paper feeding cassette with a rotary axis 86b as a center to open a refeeding path 89. Since the tip 86a of the lower conveyance guide 86 is supported at a position for receiving the paper feeding cassette by a lower conveyance guide stop member 30 even if the paper feeding cassette is inserted into the device body while the refeeding path is opened, the lower conveyance guide 86 can receive the paper feeding cassette by the tip 86a. Since the sheet conveyance guide 86 cannot receive the paper feeding cassette by an intermediate part, its deformation is prevented. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that forms an image on a supplied sheet.

  Conventionally, as shown in FIG. 5, an image forming apparatus forms an image on one side of a sheet P fed from a sheet feeding cassette 107 by an image forming unit 103, then reverses the sheet, Some of these surfaces can also form an image (see Patent Document 1). In this image forming apparatus, the reversed sheet is supplied again to the image forming unit 103 by the sheet refeed conveyance unit 180.

  The sheet refeed conveyance unit 180 is opened to remove a jammed sheet when a jammed sheet occurs in the refeed path 189.

  The refeed path 189 is opened in the following order.

  The paper feed cassette 107 is slid in the direction of arrow E and pulled out from the apparatus main body 101A of the image forming apparatus 101. Then, the release lever 192 is pushed into the apparatus main body 101A. Then, the conveyance surface holding member 190 is pushed by the release lever 192 and rotates counterclockwise in FIG. 5 about the rotation shaft 190a, and the holding portion 190b of the conveyance surface holding member 190 serves as a lower conveyance guide as a guide member. 186 is released. The lower conveyance guide 186 is received and received by the bottom plate 122 with the tip 186a side being rotated by the weight of the lower conveyance guide 186 around the rotation shaft 186b at the cassette insertion depth side. As a result, the refeed path 189 is opened. The jam sheet is taken out from the opening B by the user's hand in the opening A of the apparatus main body 101A.

JP 2001-163470 A

  However, in the conventional image forming apparatus, if the user mistakenly inserts the paper feed cassette 107 without returning the lower transport guide 186 to the original holding position, the intermediate portion of the lower transport guide 186 is pushed by the paper feed cassette 107. In some cases, it could be transformed into a reverse “he” shape. In this state, even if the sheet conveyance guide 186 is returned to the original position, the sheet refeed conveyance unit 180 cannot smoothly guide the sheet, which may cause a sheet jam or skew. there were.

  Therefore, it is conceivable that the lower conveyance guide 186 is made to have a strong structure and is difficult to be deformed. However, if the structure is strong, other problems such as an increase in the size of the apparatus, an increase in cost, and a decrease in operability due to an increase in the weight of the lower conveyance guide occur.

  The present invention provides an image forming apparatus capable of reducing deformation of a lower conveyance guide even when a user mistakenly inserts a paper feed cassette without returning the lower conveyance guide to its original holding position. It is to provide.

  The present invention includes a conveyance path that guides a sheet by a guide member along a direction in which a sheet feeding cassette on which sheets are stacked is pulled out from the apparatus main body, and the guide when the sheet feeding cassette is pulled out from the apparatus main body. The member is configured such that the cassette drawer front side pivots into the storage area of the sheet feeding cassette around the cassette insertion back side to open the transport path, and the guide member opens the transport path. In this state, when the paper feeding cassette is inserted into the apparatus main body, positioning means is provided for positioning an end portion of the guide member on the near side of the cassette drawer at a position for receiving the paper feeding cassette. It is said.

  Even if the user accidentally inserts the paper feed cassette into the apparatus main body without returning the guide member to the original holding position, the guide member receives the paper feed cassette at the end on the front side of the cassette, The deformation of the guide member can be reduced as compared with the conventional case.

  In addition, since the guide member is less deformed than in the prior art, it is possible to smoothly guide the sheet and reduce the occurrence of sheet jamming and skewing.

  An image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings. Examples of the image forming apparatus include a laser beam printer, a copying machine, a facsimile, and a composite device thereof. The image forming apparatus of the present embodiment will be described using a laser beam printer (hereinafter simply referred to as “printer”) as an example.

(Configuration of printer 1)
FIG. 3 is a cross-sectional view along the sheet conveying direction of a laser beam printer which is an image forming apparatus according to an embodiment of the present invention.

  The printer 1 includes a paper feeding / conveying unit 2, an image forming unit 3, a paper discharging unit 4, a sheet refeeding / conveying unit 80, and the like.

  The sheet feeding / conveying unit 2 is mainly composed of a sheet feeding cassette 7 and a feeding unit 8. A plurality of sheets P are stacked on the sheet feeding cassette 7. The feeding unit 8 is a unit that separates and feeds the sheets P on the sheet feeding cassette 7 one by one by a sheet feeding roller 8a, a separation pad 8b, and the like. The conveyance roller pairs 9 and 10 are rubber roller pairs that convey the fed sheet P to the image forming unit 3. A top sensor 11 for detecting the leading edge of the sheet for determining the image writing timing is provided in the vicinity of the pair of conveying rollers 10.

  The image forming unit 3 includes a process cartridge 12, a transfer roller 13, a fixing unit 14, and the like. The process cartridge 12 includes a photosensitive drum 12a, a primary charger (not shown), a developing device, toner, and the like, and is detachable from the apparatus main body 1A of the printer 1.

  The fixing unit 14 pressurizes and heats the sheet P on which the toner image is transferred to fix the toner image on the sheet P.

  The paper discharge unit 4 includes a post-fixing conveyance roller pair 15, a paper discharge roller pair 16, a paper discharge tray 17, and the like. The paper discharge tray 17 is provided on the upper part of the apparatus main body 1 </ b> A of the printer 1.

  The sheet refeed conveyance unit 80 is configured to guide the image formed and inverted sheet to the image forming unit 3 again. As will be described later, the refeed path 89 of the sheet refeed conveyance unit 80 can be opened so that when a jammed sheet is generated, the jammed sheet can be removed.

(Description of operation of printer 1)
When receiving a print command from a host computer (not shown), the sheets P stacked on the paper feed cassette 7 are separated and fed one by one by the feeding unit 8 and sent to the conveying roller pairs 9 and 10. The sheet P passes through the top sensor 11 by the conveying roller pair 9 and 10 and is then fed into the nip between the photosensitive drum 12 a and the transfer roller 13.

  When the leading edge of the sheet P is detected by the top sensor 11, the photosensitive drum 12 a is uniformly charged by a primary charger (not shown), and an electrostatic latent image is formed on the outer peripheral portion by laser light from the laser scanner 18. Are sequentially formed. The electrostatic latent image formed on the photosensitive drum 12a is developed by a developing device (not shown) to be visualized as a toner image. The toner images on the photosensitive drum 12 a are sequentially transferred by the transfer roller 13 to the sheet P sent between the photosensitive drum 12 a and the transfer roller 13.

  Thereafter, the sheet P to which the toner image has been transferred is pressed and heated to pass through the nip between the fixing roller 14a and the pressure roller 14b provided in the fixing unit 14 to fix the toner image. The sheet P that has passed through the fixing unit 14 is sent to the nip of the post-fixing conveyance roller pair 15 and then sent to the nip of the paper discharge roller pair 16. When receiving a print command for single-sided printing from the host computer, the printer 1 discharges the sheet P to the discharge tray 17 by the discharge roller pair 16.

  When the printer 1 receives a double-sided printing signal from the host computer, the sheet P that has been printed on one side is sandwiched between the nips of the paper discharge roller pair 16 and the trailing end of the sheet P is removed from the fixing unit 14. The paper discharge roller pair 16 is reversed. The sheet P is conveyed in a switchback manner, passes through the sheet refeed transport unit 80, passes through the lateral registration correction unit, and the transport path 88, and is transported again to the image forming unit 3.

  The sheet P conveyed to the image forming unit 3 undergoes an image forming process similar to that on the front surface, forms an image on the back surface, and is discharged to the paper discharge tray 17 by the paper discharge roller pair 16.

(Sheet refeed conveyance unit 80)
The sheet refeed conveyance unit 80 is an area from a branch point 81 with the conveyance path to the paper discharge tray 17 to a junction 82 with the conveyance path from the paper feed cassette 7. Note that the sheet refeed conveyance unit 80 may be at least the length of the portion facing the paper discharge tray 17. The sheet refeed conveyance unit 80 includes an oblique conveyance roller 83, an oblique conveyance roller 84 that abuts on the oblique conveyance roller 83, a reference guide 85 that defines a registration position in the width direction of the sheet, a lower conveyance guide 86, and an upper conveyance guide 87. Has been. The reference guide 85, the lower conveyance guide 86, and the upper conveyance guide 87 form a refeed path 89 (see FIG. 3) as a conveyance path. Note that the sheet refeed conveyance unit 80 may include only the lower conveyance guide 86. In this case, the lower conveyance guide 86 forms a refeed path.

  The sheet refeed conveyance unit 80 has a lateral registration correction function. The lateral registration correction function is a function for correcting the position in the width direction before forming the image on the second surface by bringing the conveyed sheet to the reference guide 85.

(Description of lower conveyance guide 86)
The lower conveyance guide 86 as a guide member is configured such that a front end portion 86a positioned on the front side of the cassette drawer can be rotated in the vertical direction with a rotation shaft 86b on the back side of the cassette insertion as a fulcrum. At the time of image formation, the lower conveyance guide 86 has two conveyance surface holdings in which supported portions 86d provided on both the left and right sides of the distal end portion 86a are connected by the rotation shaft 90a shown in FIG. The sheet 90 is supported at a position where it can be guided by the member 90.

  The conveyance surface holding member 90 is fixed to both ends of a rotation shaft 90a provided in a direction (sheet width direction) orthogonal to the sheet conveyance direction and rotates integrally with the rotation shaft 90a. Yes. The transport surface holding member 90 is normally biased to a position where the lower transport guide 86 is held by a spring (not shown).

  When a jammed sheet is generated in the sheet refeed conveyance unit 80, the sheet feeding cassette 7 is pulled out as shown in FIG. The sheet cassette 7 includes a storage guide 28 (see FIG. 2) having a U-shaped cross section provided in the right frame 21 (see FIG. 4) and a storage guide (not shown) provided in the left frame 23 (see FIG. 4). Both sides of the member are guided and slid rightward in FIG. When the paper feed cassette 7 is pulled out, an opening A is formed in the apparatus main body 1.

  A release lever 92 is provided at the front portion (right side portion in FIG. 2) of the apparatus main body 1A of the printer 1. When the front end (the right end in FIG. 2) of the release lever 92 is pushed in the left direction in FIG. 2, the rear end (the left end in FIG. 2) comes into contact with the transport surface holding member 90. The conveyance surface holding member 90 rotates in the counterclockwise direction in FIG. 2 around the rotation shaft 90a. Since the holding portion 90b (see FIG. 2) supporting the supported portion 86d (see FIG. 4) of the lower conveyance guide 86 is also rotated, the holding state of the lower conveyance guide 86 is released.

  When the lower conveyance guide 86 is released from the holding state, the leading end portion 86a of the lower conveyance guide 86 is rotated about the rotation shaft 86b by the weight of the lower conveyance guide 86 into the cassette storage area K after the sheet feeding cassette 7 is removed. . At this time, a part of the upper conveyance guide 87, the oblique feeding roller 84 and the reference guide 85 are dropped and rotated integrally with the lower conveyance guide 86.

  As shown in FIG. 4A, the contact surfaces 86c provided on the left and right sides of the tip 86a of the lower conveyance guide 86 are lower conveyance guides as positioning means provided on the right and left frames 21 and 23. It is received by a receiving surface 30 a formed on the upper portion of the stop member 30. The left and right sides of the front end portion 86a of the lower conveyance guide 86 are both sides along the cassette pull-out direction. Of course, the lower conveyance guide stop member 30 is provided at a position where it does not interfere with the paper feed cassette 7.

  As a result, as shown in FIG. 2, the leading end 86 a of the lower conveyance guide 86 is received by the lower conveyance guide stop member 30, and an opening B is formed in the sheet refeed conveyance unit 80. The jam sheet is taken out from the opening B by the user's hand in the opening A of the apparatus main body 1A.

  The transport surface holding member 90 after releasing the holding state of the lower transport guide 86 is tilted and stopped at the release position as shown in FIG. 2 by a lock mechanism (not shown).

  Next, the case where the lower conveyance guide 86 is returned from the opened state shown in FIG. 2 to the holding position shown in FIG. 3 will be described. The tip end portion 86a of the lower conveyance guide 86 is lifted and rotated upward about the rotation shaft 86b. When the distal end portion 86a of the lower conveyance guide 86 abuts against a lock mechanism (not shown) of the conveyance surface holding member 90, the lock is released, and the conveyance surface holding member 90 is biased by a spring and returns to a substantially vertical holding position. In this state, when the tip end portion 86 a of the lower conveyance guide 86 is released, the supported portion 86 d is supported on the holding portion 90 b of the conveyance surface holding member 90. As a result, the lower conveyance guide 86a is returned to the holding position shown in FIG. Finally, the opening B of the sheet refeed conveyance unit 80 is closed, and the sheet refeed conveyance unit 80 returns to a state where the sheet can be guided.

(Explanation when the paper feeding cassette is accidentally pushed in when the lower transport guide 86 opens the refeed path 89 of the sheet refeed transport section 80)
In FIG. 2, when the paper feed cassette 7 is slid substantially horizontally in the left direction and inserted into the apparatus main body 1 </ b> A of the printer 1, the rear end portion 7 a of the paper feed cassette 7 is supported by the lower conveyance guide stop member 30. It contacts the leading end 86 a of the lower transport guide 86. The paper feed cassette 7 is received by the front end portion 86 a of the lower conveyance guide 86, and no more is inserted into the apparatus main body 1 </ b> A of the printer 1.

  Next, the position where the front end portion 86a of the lower conveyance guide 86 is received by the lower conveyance guide stop member 30 will be described.

  The position of the front end portion 86a of the lower conveyance guide 86 shown in FIG. 2 is set to a position where the width of the opening B can secure a width that can easily remove the jam sheet. Further, it is set at a position that satisfies the conditions described below.

  As shown in FIG. 1, the drawn paper cassette 7 is inserted into a storage guide (not shown) provided in the right frame 21 and a left guide 23 in the vicinity of the entrance of the opening A. Not. For this reason, the lower surface 7b of the paper feed cassette 7 is supported by the bottom plate 22, and the upper end corner 7d of the rear end 7a of the paper feed cassette 7 abuts against a fixing member (not shown) of the apparatus main body 1A. And slanted. The lower surface 7 b may be a printer installation table G instead of the bottom plate 22.

  When the sheet feeding cassette 7 is slid leftward in this posture, the lower corner 7c of the rear end 7a of the sheet feeding cassette 7 is lifted from the bottom plate 22. The height position of the front end portion 86a of the lower conveyance guide 86 is set to a position further above the upper limit where the lower end corner portion 7c of the rear end portion 7a of the paper feed cassette 7 is lifted. Therefore, when the paper feed cassette 7 is pushed into the apparatus main body, the paper feed cassette 7 is always received by the front end portion 86 a of the lower transport guide 86 without riding on the lower transport guide 86.

  As described above, the sheet refeeding conveyance unit 80 can detect the lower conveyance guide even if the user accidentally inserts the sheet feeding cassette 7 without returning the lower conveyance guide 86 to the original holding position. The paper feed cassette is received at the front end portion 86a. For this reason, the load received by the lower conveyance guide 86 is applied in the longitudinal direction of the lower conveyance guide 86 and hardly applied in the thickness direction of the lower conveyance guide 86. Therefore, the lower conveyance guide 86 is not easily deformed, and the deformation is less than in the conventional case. Further, if the lower conveyance guide 86 has sufficient rigidity in the longitudinal direction, buckling deformation can be prevented, and deformation of the lower conveyance guide 86 can be reliably reduced.

  In addition, the sheet refeeding / conveying unit can smoothly guide the sheet and reduce the occurrence of sheet jamming and skewing by reducing the deformation of the guide member as compared with the conventional one.

  Further, since the sheet refeed conveyance unit does not require additional parts for preventing deformation of the lower conveyance guide 86, the rigidity of the lower conveyance guide 86 can be ensured with a simple configuration without increasing the size of the apparatus. A low-cost device can be provided.

  Since the image forming apparatus of the present invention includes the sheet refeed conveyance unit that smoothly guides the sheet described above, the image forming efficiency can be increased.

(Description of the contact surfaces 86c and 86g of the lower conveyance guide 86 and the receiving surfaces 30a and 30b of the lower conveyance guide stop member 30)
4 is a view of the front end portion 86a of the lower conveyance guide 86 and the lower conveyance guide stop member 30 in FIG. 2 as viewed from the insertion direction of the paper feed cassette 7 (as viewed from the right side in FIG. 2). In FIG. 4, the contact surface 86 c of the lower conveyance guide 86 released from the holding state is received by the receiving surface 30 a of the lower conveyance guide stop member 30 protruding inside the left and right frames 23 and 21. It is also a figure showing a state. In FIG. 4, the left-right direction is also a direction orthogonal to the insertion direction of the paper feed cassette 7 and also a sheet width direction.

  When the abutting surface 86c is received by the receiving surface 30a and the front end portion 86a of the lower transport guide 86 is pressed by the paper feed cassette 7 in the state shown in FIG. A downward load is received in the direction of arrow C shown in FIG. As shown in FIG. 2, the load in the direction of the arrow C is generated because the tip 86a is lower than the rotating shaft 86b and is inclined as shown in FIG.

  As shown in FIG. 4A, the receiving surface 30a of the lower conveyance guide stop member 30 and the contact surface 86c of the lower conveyance guide 86 are formed horizontally. That is, the angle α1 formed with the direction in which the paper feed cassette 7 is inserted is formed at a substantially right angle. In this case, when the load C received by the tip end portion 86a of the lower conveyance guide 86 is very large, the reaction force D that the contact surface 86c receives from the receiving surface 30a30a upward in the drawing also increases.

  On the other hand, as shown in FIG. 4B, the left receiving surface 30b and the abutting surface 86g, and the right receiving surface 30b and the abutting surface 86g are formed in a downward gradient toward the outside. That is, an angle α2 formed with the direction in which the paper feed cassette 7 is inserted is formed as an obtuse angle.

  By setting the angle α2 to an obtuse angle, the reaction force D received by the contact surface 86g from the receiving surface 30b is directed in the diagonally upward direction in the figure. For this reason, even if the load C increases, the reaction force D received by the contact surface 86g is dispersed into a force F1 that bends the contact surface 86g upward at the base portion 86e and a force F2 that pulls in the left-right direction. The In this case, the upward force F1 is smaller than the reaction force D shown in FIG. 4A (F1 <D).

  Therefore, since F1 <D, the base portion 86e of the contact surface 86g of the lower conveyance guide 86 can be prevented from being deformed and damaged, and the strength of the sheet refeed conveyance unit 80 is reliable. Can be increased.

  Further, since the pulling force F2 in the left-right direction acts on the lower conveyance guide 86, the lower conveyance guide 86 can be positioned in the left-right direction in FIG. 4, and the sheet refeed conveyance unit 80 skews the sheet. It is possible to guide without fail.

  Note that the left receiving surface 30b and the contact surface 86g and the right receiving surface 30b and the contact surface 86g may be formed with an upward slope (α2 is an acute angle) toward the outside. In this case, since a force toward the center of the drawing acts on the lower conveyance guide 86, the lower conveyance guide 86 can be positioned in the left-right direction in FIG. The sheet can be reliably guided without skewing.

  Since the printer according to the embodiment of the present invention includes the sheet refeed conveyance unit that reliably guides the sheet described above, the image forming efficiency can be improved.

  The sheet cassette 7 described above is drawn horizontally, but may be drawn obliquely upward or obliquely downward. Further, it may be drawn vertically. When the paper feeding cassette 7 is moved vertically, in order for the lower transport guide 86 to open the refeed path 89, it is preferable that the lower transport guide 86 opens the refeed path by a spring.

It is a figure which shows the state which the sheet feeding cassette contact | abutted to the lower conveyance guide in embodiment of this invention. FIG. 6 is a view in which a lower conveyance guide in the embodiment of the present invention opens a sheet guide path. 1 is a cross-sectional view of a laser beam printer that is an image forming apparatus according to an embodiment of the present invention along a sheet conveying direction. It is the figure which showed the contact state of the contact surface of the lower conveyance guide and the receiving surface of a lower conveyance guide stop member in embodiment of this invention. (A) is a figure in case a contact surface and a receiving surface are horizontal. (B) is a figure in case a contact surface and a receiving surface incline. FIG. 6 is a cross-sectional view along a sheet conveying direction of a conventional image forming apparatus. FIG. 6 is a diagram illustrating a state in which a sheet feeding cassette is in contact with a lower conveyance guide in a conventional image forming apparatus.

Explanation of symbols

P sheet A opening B opening K cassette storage area 1 printer (image forming apparatus)
DESCRIPTION OF SYMBOLS 1A Printer main body 2 Paper feed conveyance part 3 Image formation part 7 Paper feed cassette 7a Rear end part 7b Lower side surface 7c Lower side corner part 7d Upper end corner part 8 Feeding unit 12a Photosensitive drum 14 Fixing unit 30 Lower conveyance guide Stop member (positioning means)
30a Receiving surface of lower conveyance guide stop member 30b Receiving surface of lower conveyance guide stop member 80 Sheet refeed conveyance unit 86 Lower conveyance guide (guide member)
86a Tip part of lower conveyance guide 86b Rotating shaft 86c Abutting surface 86d Supported part 86e Base part 86g Abutting surface 87 Upper conveyance guide 89 Refeed path (conveyance path)
90 Transport surface holding member 92 Release lever

Claims (3)

A sheet feeding cassette on which sheets are stacked is provided with a conveyance path for guiding a sheet by a guide member along a direction in which the sheet is pulled out from the apparatus main body, and when the sheet feeding cassette is pulled out from the apparatus main body, the guide member is In the image forming apparatus configured such that the cassette drawer front side pivots into the storage area of the paper feed cassette with the back side of the insertion as the center, and the transport path is opened.
When the paper feed cassette is inserted into the apparatus main body with the guide member opened in the transport path, the end of the guide member on the front side of the cassette is positioned at a position for receiving the paper feed cassette. Provided with positioning means for
An image forming apparatus. The positioning means is provided on both sides in the cassette pull-out direction, and includes a receiving surface that receives the contact surface provided on the guide member,
The contact surface and the receiving surface are inclined surfaces that position the guide member in a direction intersecting the cassette pulling direction.
The image forming apparatus according to claim 1. The transport path is a refeed path that guides the sheet on which an image is formed on one side and reversed, to the image forming unit.
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.

Images