JP2007297141A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate damage of an actuator by a recording medium even if the recording medium jammed in a fixing unit is drawn out to a fixing cover side. <P>SOLUTION: When a paper guide 62 is upwardly turned making a turning fulcrum M as a center, an arm 42 is turned together with turning of the paper guide 62 making a shaft 38 as a center and is retreated from above a nipping part of a heat roll 32 and a pressurization roll 34. Namely, when the paper guide 62 is released, the arm 42 is not left above the nipping part of the heat roll 32 and the pressurization roll 34. Therefore, since a route for drawing out the jammed paper P is not closed by the arm 42, the paper P to be drawn out is not abutted on the arm 42. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus including a fixing device that fixes a toner image on a recording medium.

  In an image forming apparatus such as a copying machine or a printer, an electrostatic latent image is formed on the surface of an image carrier such as a photoconductor, and the electrostatic latent image is visualized by a developing device to form a toner image. Then, after the toner image is transferred to a recording medium such as paper, the toner image on the recording medium is fixed by heating and pressing with a fixing device.

  The fixing device includes a heating roller with a built-in heater and a pressure roller that presses the recording medium against the heating roller. Then, the recording medium on which the toner image is formed is passed between the heating roller and the pressure roller (fixing unit), and the toner image is melted and fixed on the recording medium by heating and pressing.

  Such a fixing device is usually provided with an actuator for detecting the presence or absence of a sheet in the vicinity of the sheet discharge port (see Patent Document 1). When the tip of the recording medium passing through the fixing unit comes into contact with this actuator, the actuator rotates, and a sensor for detecting the rotation of the actuator detects whether or not the recording medium exists in the fixing device. The

By the way, when the recording medium is jammed in the fixing device, it is necessary to open the fixing cover provided above the actuator and remove the jammed recording medium. In the image forming apparatus of Patent Document 1, when the fixing cover is opened, the actuator remains in the vicinity of the paper discharge port. For this reason, when the jammed paper from the fixing unit is pulled out to the fixing cover side, an axial force acts on the tip of the actuator from the recording medium, and the actuator may be damaged.
JP 2002-82562 A

  An object of the present invention is to prevent an actuator from being damaged by a recording medium even when the recording medium jammed in the fixing device is pulled out to the fixing cover side.

  According to a first aspect of the present invention, there is provided an image forming apparatus in which a toner image on a recording medium is fixed by a fixing device and the recording medium on which the toner image is fixed is discharged to a paper discharging portion. A paper guide that is provided in a releasable manner and guides a recording medium on which a toner image is fixed to the paper discharge unit, and a paper that is attached to the fixing device and that is pressed by the recording medium and swings to detect the presence of the recording medium. A detection unit; and a guide unit that is provided in the paper guide and contacts the paper detection unit when the paper guide is opened, and rotates the paper detection unit together with the paper guide. It is characterized by.

  According to the first aspect of the present invention, when the paper guide is opened, the guide portion provided on the paper guide comes into contact with the paper detection means and rotates together with the paper guide.

  That is, even when the paper guide is opened, the paper detection means does not remain at the paper discharge port of the fixing device, so that the paper discharge port is opened. For this reason, when the jammed recording medium is pulled out in the fixing device, the recording medium does not hit the paper detection means, so that the paper detection means is not damaged.

  According to a second aspect of the present invention, the recording sheet detecting means includes an arm that contacts the leading end of the recording medium on which the guide portion contacts and a toner image is fixed, and an end portion of the arm that is connected to the fixing device. And a detection unit that is provided on the shaft and that is detected by a sensor installed in the fixing device when the shaft rotates. It is said.

  According to the invention of claim 2, when the leading end of the recording medium on which the toner image is fixed contacts the arm, the shaft connected to the arm rotates. And the detection part provided in the shaft is detected by the sensor installed in the fixing device.

  With such a configuration, for example, when it is detected that the arm does not return to the original position after a predetermined time has elapsed since the sensor detects that the leading edge of the recording medium has come into contact with the arm, It can be determined that the recording medium has jammed.

  According to a third aspect of the present invention, the end of the arm is provided with a biasing member that rotates the shaft toward the upstream side in the paper transport direction, and the biasing member is opened when the paper guide is opened. It is characterized in that a cover for covering is provided.

  According to the invention of claim 3, the urging member that urges the shaft to rotate toward the upstream side in the paper transport direction is covered by the cover and not exposed to the user side when the paper guide is opened. Has been. Thus, for example, when a metal coil spring is used as the urging member, the user who tries to pull out the recording medium does not directly touch the coil spring heated by the heat generated from the fixing device.

  The present invention described in claim 4 is characterized in that the surface of the arm with which the guide portion abuts is a curved surface.

  According to invention of Claim 4, a guide part rotates an arm, contacting the curved surface of an arm. In other words, since the guide part and the arm have different rotation centers, the movement trajectories are also different, and by making the surface that the guide part of the arm contacts a curved surface, the arm is smoothly guided to the guide part, and the paper guide Rotates with opening.

  The present invention according to claim 5 is characterized in that the guide portion is brought into contact with the tip of the arm when the paper guide is opened.

  According to the invention of claim 5, when the sheet guide is opened, the guide portion comes into contact with the tip of the arm. That is, when the paper guide is opened, the tip of the arm is covered with the guide portion and is not exposed to the user side. For this reason, since the user's hand does not touch the arm tip, the arm is prevented from being damaged.

  The present invention described in claim 6 is characterized in that a guide piece protruding from the arm when the paper guide is opened is formed inside the paper guide.

  According to the invention of claim 6, a guide piece is formed inside the paper guide, and when the paper guide is opened, the guide piece protrudes from the arm. Accordingly, when the recording medium is pulled out from the fixing device with the paper guide being opened, the recording medium contacts the guide piece and does not directly contact the arm. Therefore, there is no possibility that the arm is damaged by pulling out the recording medium.

  The present invention according to claim 7 is characterized in that the shaft is provided with a contact piece that contacts the fixing device and maintains the arm in a predetermined posture.

  According to the seventh aspect of the present invention, the arm is maintained in a predetermined posture by the contact piece provided on the shaft contacting the fixing device. As a result, the shaft urged toward the upstream side in the paper conveyance direction by the urging member is accurately regulated with respect to the paper conveyance path, so that the arm rotates each time the shaft rotates by opening the paper guide. Therefore, there is no fear that the recording medium will jam.

  Since the present invention is configured as described above, even if the recording medium jammed in the fixing device is pulled out to the fixing cover side, the actuator is not damaged by the recording medium.

  An image forming apparatus 10 according to an embodiment of the image forming apparatus of the present invention will be described.

  FIG. 1 shows a schematic configuration of an image forming apparatus 10 according to an embodiment of the present invention.

  The image forming apparatus 10 includes four photosensitive drums 12 corresponding to each color (yellow, magenta, cyan, black). A charger 14 is provided around each photosensitive drum 12, and the photosensitive drum 12 is charged to a predetermined surface potential by the charger 14.

  Further, a developing device 16 is provided downstream of the charging device 14 in the rotation direction of the photosensitive drum 12. The developing device 16 develops the electrostatic latent image by supplying toner to the electrostatic latent image formed on the photosensitive drum 12 by the light beam LB emitted from the optical scanning device 29, thereby developing the photosensitive drum 12. A toner image is formed thereon.

  A transfer device 18 is disposed on the side where each photosensitive drum 12 is provided. The transfer device 18 includes a pair of conveying rollers 20 and an endless sheet conveying belt 22 wound around the conveying rollers 20.

  On the other hand, a paper feed cassette 24 is disposed below the image forming apparatus 10. When the paper P is supplied from the paper feed cassette 24 to the transfer device 18, the paper P is electrostatically attracted and transported to the paper transport belt 22, and is transferred by a transfer device 26 provided at a position facing the photosensitive drum 12. The toner image on the photosensitive drum 12 is transferred to the paper P.

  The single-color images of yellow, magenta, cyan, and black formed on each photoconductor drum 12 are transferred onto the paper P conveyed by the paper conveyance belt 22 in a superimposed manner. As a result, a multicolor toner image is formed on the paper P and sent to the fixing device 28 provided on the upstream side in the paper transport direction.

  As shown in FIG. 4, the fixing device 28 includes a housing 30, and a heat roll 32 heated to a predetermined temperature is pressed into the housing 30 and the paper P is pressed between the heat roll 32. A pressure roll 34 is provided.

  The heat roll 32 is rotated in the direction of arrow F by a drive motor (not shown), and the pressure roll 34 is driven to rotate by this rotation. At this time, the paper P on which the toner image is formed is conveyed to the nip portion between the heat roll 32 and the pressure roll 34, and the toner on the paper P is transferred by the heat from the heat roll 32 and the pressure from the pressure roll 34. The toner image is melted and fixed on the paper P. The paper P is transported along the transport path by the transport roll 65 disposed on the downstream side in the transport direction of the heat roll 32 and the pressure roll 34.

  2 and 3 show the fixing device 28 taken out from the image forming apparatus 10.

  As shown in FIG. 3, an actuator 36 is provided on the top plate 30 </ b> A of the housing 30 of the fixing device 28. The actuator 36 has a shaft 38. The shaft 38 is disposed along a direction orthogonal to the paper transport direction, and one end is formed on the side wall of the housing 30, and the other end is formed on the top plate 30 </ b> A of the housing 30. 40 is rotatably supported.

  An arm 42 is integrally provided in the vicinity of the other end of the shaft 38 (the side supported by the support protrusion 40). The arm 42 has a long and substantially rectangular plate shape, the longitudinal direction is orthogonal to the axis of the shaft 38, and the shaft 38 and the arm 42 are substantially T-shaped.

  The arm 42 is rotated about the shaft 38 along with the rotation of a sheet guide 62 described later. As shown in FIG. 4, when the paper guide 62 is in the closed state, the tip of the arm 42 is separated by a predetermined distance above the nip portion of the heat roll 32 and the pressure roll 34 (on the conveyance path of the paper P). Located in a state. For this reason, the leading edge of the paper P that has passed through the nip portion between the heat roll 32 and the pressure roll 34 comes into contact with the surface of the arm 42 on the side of the heat roll 32 and the pressure roll 34 (this surface is referred to as a “back surface”). .

  When the leading edge of the paper P comes into contact with the back surface of the arm 42, the arm 42 rotates about the shaft 38. That is, the arm 42 is pushed upward by the paper P. As a result, as shown in FIG. 7B, the arm 42 is retracted from the transport path 44 and transported upward while the back surface of the paper P is in contact with the arm 42. At this time, a paper guide 62 (to be described later) is also pushed upward by the leading edge of the paper P, and the paper P is sent to the transport roll 65 and discharged to the paper discharge unit 66 (see FIG. 1).

  On the other hand, as shown in FIGS. 3 and 9, a cutout 46 is formed at the base of the arm 42. One end of a coil spring 48 wound around the shaft 38 is hooked on the notch 46. The other end of the coil spring 48 is hooked on a lid-like locking part 50 formed on the top plate 30A of the housing 30. The coil spring 48 causes the arm 42 to rotate counterclockwise (upstream in the transport direction of the paper P). Side).

  The shaft 38 is provided with a rectangular convex piece 54. As shown in FIG. 8, the convex piece 54 is provided at a position where it comes into contact with the top plate 30 </ b> A when the tip of the arm 42 is located above the nip portion of the heat roll 32 and the pressure roll 34 (see FIG. 4). It has been.

  As a result, when the paper P passes, the arm 42 lifted by the leading edge of the paper P is rotated upstream in the transport direction of the paper P by the urging force of the coil spring 48 (see FIG. 4). At this time, since the rotation of the shaft 38 is restricted by the convex piece 54, the arm 42 is maintained in the posture positioned on the conveyance path 44.

  Incidentally, a cover 52 is provided on the portion of the shaft 38 around which the coil spring 48 is wound so as to cover the coil spring 48. The cover 52 is provided on the side opposite to the side on which the arm 42 of the shaft 38 is formed. For this reason, when the shaft 38 rotates and the back surface of the arm 42 faces upward, the coil spring 48 is covered by the cover 52 and is not exposed to the front surface (user side).

  On the other hand, at one end of the shaft 38 (side supported by the side wall of the housing 30), a plate piece 56 projects in the radial direction.

  A photo sensor 58 is disposed below the plate piece 56. The photosensor 58 includes a light projecting unit 58A that emits light, and a light receiving unit 58B that receives light emitted from the light projecting unit 58A. It is installed so as to sandwich it. When the light emitted from the light projecting unit 58A is received by the light receiving unit 58B, the light is turned on, and otherwise the light is turned off.

  With such a configuration, when the shaft 38 rotates and the plate piece 56 is positioned between the light projecting unit 58A and the light receiving unit 58B, the photosensor 58 is turned on and it is detected that the shaft 38 has been rotated. ing.

  That is, as shown in FIG. 7B, when the paper P that has passed through the nip portion of the heat roll 32 and the pressure roll 34 contacts the arm 42 and the shaft 38 rotates clockwise, the rotation of the shaft 38 causes the plate to rotate. The piece 56 turns on the photosensor 58, and it is detected that the paper P is in contact with the arm 42.

  When the rear end of the paper P is separated from the arm 42, as shown in FIG. 7A, the shaft 38 rotates counterclockwise by the biasing force of the coil spring 48, the photo sensor 58 is turned off, and the arm 42 is turned off. It is detected that the rear end of the sheet P has passed through the conveyance path 44 between the housing 30 and the housing 30.

  If the photosensor 58 does not turn off even after a predetermined time has passed since the photosensor 58 is turned on, it is determined that the paper P has jammed in the fixing device 28. The fact that the paper P has jammed in the fixing device 28 is displayed on a panel (not shown) of the main body of the image forming apparatus 10 (see FIG. 1).

  By the way, as shown in FIGS. 2 and 3, a paper guide 62 is provided above the actuator 36. The sheet guide 62 includes a cover 62B that covers the conveyance path 44 (see FIG. 7B) and guide pieces 62A that protrude from both surfaces of the cover 62B.

  One end of the cover 62B in the width direction (paper conveyance direction) is rotatably supported by a bearing portion 64 formed near the side wall of the top plate 30A of the housing 30. As a result, when the leading edge of the paper P comes into contact with the back surface (the surface facing the arm 42) of the paper guide 62, one end portion (a portion supported by the bearing portion 64, hereinafter referred to as a “rotation fulcrum M”). It can be rotated around the axis and lifted.

  With this configuration, the paper P passes through the paper guide 62 and is discharged to the paper discharge unit 66 (see FIG. 1) by the transport roll 65.

  The transport roll 65 is capable of forward and reverse rotation. In the double-sided printing mode, when the actuator 36 detects the trailing edge of the paper P, the transport roll 65 reverses and the paper P is placed on the upper surface of the paper guide 62. Be transported. Then, the sheet P on which an image is formed on one side is sent to a transport unit 68 provided on the right side of the transfer device 18 in FIG. 1, and is reversed and sent to the transfer device 18.

  On the other hand, as shown in FIGS. 2 and 3, a rectangular opening 70 is formed at a substantially central portion of the paper guide 62. Further, a guide portion 72 is provided on the back surface of the paper guide 62 at a position where the opening portion 70 is formed. The guide portion 72 includes a standing piece 74 standing from both sides in the width direction of the opening 70 (a direction orthogonal to the conveyance direction of the paper P), and a connecting piece 76 connecting the standing piece 74. It is shaped like a letter.

  As shown in FIG. 4, when the paper guide 62 is closed, the connecting piece 76 is positioned below the arm 42 of the actuator 36. When the paper guide 62 is opened, first, the connecting piece 76 comes into contact with the vicinity of the base on the back surface of the arm 42 as shown in FIG. When the paper guide 62 is further rotated about the rotation fulcrum M, the connecting piece 76 rotates the arm 42 about the shaft 38 while moving along the curved surface on the back surface of the arm 42. When the paper guide 62 rotates about 180 degrees around the rotation fulcrum M, the connecting piece 76 supports the front end portion of the back surface of the arm 42. That is, the connecting piece 76 is in contact with the arm 42 even when the paper guide 62 is fully opened. Thereby, when the paper guide 62 is opened, the arm 42 is also rotated together, and the nip portion between the heat roll 32 and the pressure roll 34 is exposed.

  Incidentally, as shown in FIG. 3, the leading end of the guide piece 62 </ b> A protruding to the back side of the paper guide 62 is positioned below the connecting piece 76 when the paper guide 62 is closed. Thus, as shown in FIG. 6, when the paper guide 62 is fully opened, the leading end of the guide piece 62A is positioned above the arm 42, so that the paper is fed from the nip between the heat roll 32 and the pressure roll 34. When the paper P is pulled out in the direction in which the guide 62 is opened, the paper P comes into contact with the tip of the guide piece 62A. That is, the paper P to be pulled out is not in contact with the arm 42.

  Next, the operation of the embodiment of the present invention will be described.

  When the paper guide 62 is rotated upward about the rotation fulcrum M, the connecting piece 76 of the guide portion 72 provided integrally with the paper guide 62 contacts the arm 42 of the actuator 36. As the paper guide 62 rotates, the arm 42 is guided to the connecting piece 76. As the paper guide 62 rotates, the arm 42 rotates about the shaft 38, and the heat roll 32 and the pressure roll 34. Retreat from above the nip.

  That is, when the paper guide 62 is opened, the arm 42 does not remain above the nip portion between the heat roll 32 and the pressure roll 34. Therefore, the path for pulling out the jammed paper P is not blocked by the arm 42, so that the paper P to be pulled out does not hit the arm 42. Further, even when the jammed paper P is pulled out to the side where the paper guide 62 is opened, it does not come into contact with the tip of the arm 42 from a substantially vertical direction. Therefore, no matter which direction the paper P is pulled out, the arm 42 is not damaged.

  The arm 42 is biased counterclockwise in FIG. 4 by the coil spring 48. When the paper guide 62 is opened and the arm 42 is turned upward, the coil spring 48 wound around the shaft 38 is It is not exposed to the user side. Thus, the user who is trying to pull out the paper P does not directly touch the coil spring 48 heated by the heat generated from the heat roll 32.

  Further, when the paper guide 62 is opened, the connecting piece 76 of the guide portion 72 comes into contact with the tip of the arm 42. That is, even if the paper guide 62 is opened, the tip of the arm 42 is covered with the connecting piece 76 and is not exposed to the user side. For this reason, since the user's hand does not touch the tip of the arm 42, the tip of the arm 42 is prevented from being damaged.

  Further, since the guide piece 62A protrudes from the back surface of the paper guide 62 in a state of protruding from the guide portion 72, the paper P pulled out from the nip portion of the heat roll 32 and the pressure roll 34 is the guide piece. It abuts on 62A and does not abut directly on the arm 42. Therefore, even if the paper P is pulled out in the direction in which the paper guide 62 is opened, the arm 42 is not damaged.

  Further, when the paper guide 62 is in the closed state, the convex piece 54 provided on the shaft 38 contacts the top plate 30A of the housing 30, so that the angle of the arm 42 with respect to the conveyance path of the paper P is accurately regulated. . That is, every time the shaft 38 rotates by opening and closing the paper guide 62, the position of the arm 42 does not shift. For example, the position of the arm 42 moves closer to the nip portion side of the heat roll 32 and the pressure roll 34. Thus, even if the leading edge of the paper P comes into contact, the arm 42 is not moved, and there is no worry that the paper P is jammed.

  In addition, since the guide portion 72 and the arm 42 have different rotation centers, the movement trajectories are also different. Accordingly, the arm 42 is smoothly guided to the guide portion 72 by making the surface with which the guide portion 72 of the arm 42 abuts a curved surface. Thus, the sheet guide 62 rotates with the opening.

  In the present embodiment, the convex piece 54 provided on the shaft 38 of the actuator 36 is detected by the photo sensor 58 provided on the housing 30 of the fixing device 28, so that the leading edge of the paper P contacts the arm 42. As described in the configuration in which the contact is detected, the means for detecting whether or not the leading edge of the paper P has contacted the arm 42 is replaced with an optical sensor, a magnetic sensor, an ultrasonic sensor, A micro switch or the like can be used.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a perspective view showing a fixing device mounted on the image forming apparatus with a paper guide closed. FIG. 3 is a perspective view illustrating a state in which a sheet guide is opened in a fixing device mounted on the image forming apparatus. FIG. 3 is a side sectional view of the fixing device. FIG. 4 is a side cross-sectional view illustrating a state where a sheet guide of the fixing device is closed. FIG. 4 is a side cross-sectional view illustrating a state in which a sheet guide of the fixing device is opened. 4A and 4B are side cross-sectional views of the fixing device, in which FIG. 4A is a diagram illustrating a state where the paper P is not in contact with the actuator, and FIG. 4B is a diagram illustrating a state where the paper P is in contact with the actuator. FIG. 3 is a perspective view showing an actuator mounted on the fixing device and a sensor provided on the apparatus main body. It is a fragmentary perspective view which shows the state which rotated the actuator.

Explanation of symbols

10 Image forming device (device main body)
28 Fixing device (fixing device)
36 Actuator (paper detection means)
38 Shaft (paper detection means)
42 Arm (paper detection means)
48 Coil spring (biasing member)
52 Cover 54 Convex piece (contact piece)
56 Plate (paper detection means, detection unit)
58 Photosensor (Sensor)
62 Paper guide 66 Paper discharge part 72 Guide part 78 Guide piece

Claims (7)

In an image forming apparatus for fixing a toner image on a recording medium with a fixing device and discharging the recording medium on which the toner image is fixed to a paper discharge unit,
A paper guide that is removably provided at a paper discharge port of the fixing device and guides a recording medium on which a toner image is fixed to the paper discharge unit;
A sheet detecting means attached to the fixing device and pressed by the recording medium to swing and detect the presence or absence of the recording medium;
A guide portion provided in the paper guide, which abuts against the paper detection means when the paper guide is opened and rotates the paper detection means together with the paper guide;
An image forming apparatus comprising:   The sheet detecting means includes an arm that abuts on the leading end of the recording medium on which the guide portion abuts and a toner image is fixed, and a shaft that is coupled to the end of the arm and is rotatably supported by the fixing device. 2. The image forming apparatus according to claim 1, further comprising: a detection unit that is provided on the shaft and that is detected by a sensor installed in the fixing device when the shaft rotates. apparatus.   An urging member that rotates the shaft toward the upstream side in the paper conveyance direction is provided at an end of the arm, and a cover that covers the urging member when the paper guide is opened is provided. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   The image forming apparatus according to claim 2, wherein a surface of the arm with which the guide portion abuts is a curved surface.   4. The image forming apparatus according to claim 2, wherein the guide portion is brought into contact with a tip of the arm when the paper guide is opened. 5.   6. The guide piece according to claim 2, wherein a guide piece that protrudes beyond the arm when the paper guide is opened is formed inside the paper guide. 7. Image forming apparatus.   7. The image forming apparatus according to claim 2, wherein the shaft is provided with a contact piece that contacts the fixing device and maintains the arm in a predetermined posture. apparatus.

Images