JP2007025349A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cam mechanism capable of making an apparatus small in size and low in cost by reducing the number of components in a pressure releasing mechanism of a fixing device. <P>SOLUTION: In the pressure releasing mechanism of the fixing device, which prevents a pressure higher than necessary from being applied to a pressure roller 41 or a fixing roller 42 in a power saving mode or the like, cam follower surfaces X, Y, and Z of a pressure releasing cam 45 are provided with gentle parts, and the pressure releasing cam is rotated half a turn or more to switch from a pressure releasing state to a pressurizing state, so that acceleration of rotation due to an energizing force from an energizing member is suppressed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention employs an electrostatic recording system, an electrophotographic recording system, and the like, and has a function of forming an image on a recording medium such as a sheet, for example, an image forming apparatus such as a copying machine, a printer, or a facsimile machine It is about.

  In recent years, as a fixing device in an image forming apparatus such as a copying machine, a printer, or a facsimile machine, a nip is formed by a fixing member 41 having a heat source (not shown) and a pressure member 42 as shown in FIG. In a state where the fixing member 41 is pressed against the pressing member 42 by a predetermined pressure by the pressing spring 43 and the connecting member 44, the recording material P on which an unfixed image is placed in the nip is conveyed and heated and pressed. A configuration for fixing is known. In the case of a paper jam process in the fixing device, the connecting member 44 and the fixing member 41 are moved to the pressure member 42 by rotating the pressure release cam 45 halfway in the direction of arrow B as shown in FIG. Structures that are further spaced apart to facilitate paper jam handling are also well known. It is also well known that the fixing device can be easily detached from the image forming apparatus main body for paper jam handling and maintenance.

  However, in the fixing device having the pressure release configuration using the cam as described above, the following problems occur.

  That is, the pressure release cam 45 rotates the pressure release cam 45 another half from the state shown in FIG. 5 (2) to the state shown in FIG. 5 (1) in order to perform a normal fixing operation after the paper jam processing is completed. return. At this time, the power transmission system including the pressurizing release cam 45 is inevitably rotated by receiving the biasing force of the pressurizing spring 43. Depending on the magnitude of the biasing force of the pressurizing spring 43, the pressurizing release is performed. Acceleration is applied to the rotational operation of the cam, and abnormal noise, vibration, damage to parts, etc. occur. In particular, since the urging means used in the fixing device as described above has a large urging force, there is a high possibility that the above-mentioned problem will occur. In order to solve this problem, the cost is increased because the parts are made of a robust material. There is a problem that it ends up.

  On the other hand, even in the fixing drive system as shown in FIG. 4, it is very problematic that the urging force as described above accelerates the rotation of the pressure release cam.

  That is, the fixing drive system shown in FIG. 4 includes a drive motor 61, a reduction gear 62, a gear 63 located at the center of oscillation, a gear 65 for directly rotating a pressure member around the shaft center of the gear 63, and a pressure release cam 45. And a rocking gear 64 that rocks to a position that meshes with a gear 66 that directly rotates the gear 66. In FIG. 4A, when the drive motor 61 rotates in the direction of arrow C, the swing gear 64 swings until it engages with the pressure member gear 65 by the rotational force received from the gear 63. In FIG. 4 (2), when the drive motor 61 rotates in the direction of arrow D, the swing gear 64 swings until it engages with the pressure release cam gear 65 by the rotational force received from the gear 63. In this way, the fixing drive system using the swing gear as shown in FIG. 4 is cost-effective because the separate drive systems of the fixing drive operation and the pressure release operation are performed by forward and reverse rotation of a single motor. This is very advantageous and contributes to the miniaturization of the equipment. However, in the drive system using the oscillating gear as shown in FIG. 4, the urging force is applied to the pressure release cam in the direction of accelerating the rotation, so that the oscillating gear is disengaged. As a result, tooth skipping occurs, making it difficult to reliably transmit the drive, and eventually the parts are damaged.

  Further, the fixing device as a whole may be lifted by vibration accompanying acceleration of the rotation operation of the pressure release cam. In such a case, a configuration such as a lock member for completely fixing the fixing device to the image forming apparatus main body. There is also a problem in usability that it is difficult to reduce the cost and size of the apparatus, and that it cannot be easily attached and detached.

In order to solve such a problem, a proposal has been made to reduce the influence of the urging force on the rotation operation of the pressure release cam by providing a braking means in the pressure release mechanism (Japanese Patent Laid-Open No. 2003-280308). In the above proposal, a braking means using a notch gear and a torque limiter is incorporated in the power transmission system of the pressure release mechanism to effectively reduce the influence of the urging force during the rotation operation of the pressure release cam, It is very effective in preventing vibrations and component damage.
JP 2003-280308 A

  However, in the above invention, a notch gear, a torque limiter, or the like is used as the braking means, so that the drive configuration for releasing the pressure becomes complicated, and it becomes difficult to ensure the reliability of the apparatus.

  In addition, since the number of parts and the number of assembly steps are surely increased, the part cost and the assembly cost are increased, and the cost reduction of the entire apparatus is surely obstructed.

  Further, a place for providing the braking means is necessary in the apparatus, which hinders downsizing of the apparatus, and the braking means must be disposed in the vicinity of the fixing device that is at a high temperature. The device becomes large.

  Accordingly, an object of the present invention is to solve the above problems.

  The present invention has been made to solve the above-described conventional drawbacks, and can be solved by the following invention.

1st invention has a heat source inside, the fixing member for fixing the image on a recording material, the pressurization member which presses and conveys a recording material to the said fixing member, and pressurizes the said fixing member An urging means for pressing the member with a predetermined pressure, and a pressure release that moves to a pressing position that acts on the urging means to press the fixing member against the pressing member and a release position that releases the pressing force. An image forming apparatus comprising:
The pressure release means has a pressure release cam for releasing the pressing force,
The pressure release cam moves the fixing member alternately between the pressure position and the release position every rotation and moves the fixing member from the release position to the pressure position. This is realized by rotating the pressure release cam half or more times.

According to a second aspect of the present invention, there is provided a fixing member having an internal heat source for fixing an image on a recording material, a pressure member for pressing and conveying the recording material against the fixing member, the fixing member and the heating member. A drive unit comprising a drive motor and a drive gear train for rotating the pressure member, an urging means for pressing the fixing member against the pressure member with a predetermined pressure, and acting on the urging means to fix the fixing member In an image forming apparatus having a pressure release unit that moves a pressure position to press a member against a pressure member and a release position to release the pressing force.
The pressure release means has a pressure release cam that releases the pressing force. The drive unit has a swing gear that swings between a first position and a second position by forward and reverse rotation of the drive motor. When the drive motor rotates in the forward direction, the swing gear is disposed at the first position to rotate the fixing member and the pressure member. When the drive motor rotates in the reverse direction, the swing gear is set to the second position. The pressure release cam is arranged to be driven to rotate,
The pressure release cam moves the fixing member alternately between the pressure position and the release position every rotation and moves the fixing member from the release position to the pressure position. This is realized by rotating the pressure release cam half or more times.

  According to a third aspect of the present invention, in the first and second aspects of the present invention, the pressure release cam can move the fixing member to the release position by rotating half a turn or less, and the connecting member. And a cam follower surface that can move the fixing member to the pressure position by rotating more than half a rotation with respect to the urging means.

According to the image forming apparatus of the present invention,
The influence of the urging force in the rotation operation of the pressure release cam can be mitigated by optimizing the shape and rotation angle of the cam follower surface of the pressure release cam without using a braking means such as a notch gear or a torque limiter. Therefore, the drive structure for releasing pressure is not complicated, and it is easy to ensure the reliability of the apparatus.

  In addition, the number of parts and the number of assembling steps can be reduced, the parts cost and the assembling cost can be kept low, and the cost reduction of the entire apparatus can be surely realized. Furthermore, since a place for providing a braking means or the like is unnecessary, it is also effective from the viewpoint of downsizing the apparatus.

  In addition, the entire fixing device is not lifted by the vibration associated with acceleration of the rotation operation of the pressure release cam, and there is no need for a configuration such as a lock member for completely fixing the fixing device to the image forming apparatus main body. Therefore, it is possible to reduce the cost and the size of the apparatus, and to improve usability such that it can be easily attached and detached.

  Hereinafter, the present invention will be described more specifically with reference to examples. Although these examples are examples of the best mode of the present invention, the present invention is not limited to these examples.

  FIG. 2 is a schematic configuration diagram showing an image forming apparatus (in the figure, an electrophotographic inline type full color printer) according to the first embodiment of the present invention.

  The image forming apparatus includes an image forming unit 1a that forms a yellow image, an image forming unit 1b that forms a magenta image, an image forming unit 1c that forms a cyan image, and a black image. The image forming unit 1d to be formed includes four image forming units (image forming units), and these four image forming units 1a, 1b, 1c, and 1d are arranged in a line at regular intervals.

  Each of the image forming units 1a, 1b, 1c, and 1d is provided with drum-type electrophotographic photosensitive members (hereinafter referred to as photosensitive drums) 2a, 2b, 2c, and 2d as image carriers. Around each of the photosensitive drums 2a, 2b, 2c, and 2d, chargers 3a, 3b, 3c, and 3d, developing devices 4a, 4b, 4c, and 4d, and drum cleaning devices 5a, 5b, 5c, and 5d are installed, respectively. An exposure device 6a, 6b, 6c, 6d is installed above the charger 3 and the developing device 4, respectively. Each developing device 4a, 4b, 4c, and 4d contains yellow toner, magenta toner, cyan toner, and black toner, respectively.

  Each of the photoconductor drums 2a, 2b, 2c, and 2d is a negatively charged OPC photoconductor having a photoconductive layer on an aluminum drum base, and an arrow direction (counterclockwise) by a driving device (not shown). Are rotated at a predetermined process speed. The chargers 3a, 3b, 3c, and 3d as charging means make the surfaces of the photosensitive drums 2a, 2b, 2c, and 2d uniform to a predetermined negative potential by a charging bias applied from a charging bias power source (not shown). Charge.

  The developing devices 4a, 4b, 4c, and 4d develop toner images by attaching toners of respective colors to the electrostatic latent images formed on the photosensitive drums 2a, 2b, 2c, and 2d, respectively (visualization). To do. As a developing method using the developing devices 4a, 4b, 4c, and 4d, for example, toner particles mixed with a magnetic carrier are used as a developer and conveyed by magnetic force, and the photosensitive drums 2a, 2b, 2c, and 2d are used. In contrast, a two-component contact development method in which development is performed in a contact state can be used.

  The transfer rollers 34a, 34b, 34c, and 34d as transfer means are made of an elastic member, and an endless belt-like transfer material conveyance belt (hereinafter referred to as a transfer belt) at the nip portion of each transfer portion Ta, Tb, Tc, and Td. And abutted on the photosensitive drums 2a, 2b, 2c, and 2d via 31. Here, the transfer roller 34 is used as the transfer unit, but a transfer blade that is applied with a high pressure when the toner image is transferred onto the transfer material and is in contact with the transfer belt 31 may be used.

  The drum cleaning devices 5a, 5b, 5c, and 5d remove and collect the transfer residual toner remaining on the surfaces of the photosensitive drums 2a, 2b, 2c, and 2d, respectively.

  In the exposure apparatuses 6a, 6b, 6c, and 6d, a laser beam modulated in accordance with a time-series electric digital pixel signal of image information is output from a laser output unit (not shown), and a polygon mirror (not shown) that rotates at high speed. By exposing the surfaces of the photosensitive drums 2a, 2b, 2c, and 2d through the like, images are formed on the surfaces of the photosensitive drums 2a, 2b, 2c, and 2d charged by the chargers 3a, 3b, 3c, and 3d. An electrostatic latent image of each color corresponding to the information is formed.

  The transfer belt 31 is stretched between the drive roller 32 and the tension roller 33 and is rotated (moved) in the direction of the arrow (clockwise) by the drive of the drive roller 32. The transfer belt 31 is made of a dielectric resin such as a polycarbonate, a polyethylene terephthalate resin film, a polyvinylidene fluoride resin film, or the like.

  A fixing device 40 having a heating roller 41 and a pressure roller 42 that include a heat source 46 is installed downstream of the transfer belt 31 in the transfer material conveyance direction.

  Next, an image forming operation by the above-described image forming apparatus will be described.

  When the image formation start signal is issued, the photosensitive drums 2a, 2b, 2c, and 2d of the image forming units 1a, 1b, 1c, and 1d that are rotationally driven at a predetermined process speed are respectively charged by the chargers 3a, 3b, and 3c. , 3d is uniformly negatively charged. The exposure devices 6a, 6b, 6c, and 6d convert the image signal of the output image into an optical signal by a laser output unit (not shown), respectively, and the laser beam that is the converted optical signal is charged to each photosensitive element. Each of the drums 2a, 2b, 2c, and 2d is scanned and exposed to form an electrostatic latent image.

  First, yellow toner is adhered to the electrostatic latent image formed on the photosensitive drum 2a by the developing device 4a to which a developing bias having the same polarity as the charging polarity (negative polarity) of the photosensitive drum 2a is applied. Visualize as an image.

  Then, in accordance with the timing at which the front end of the toner image on the photosensitive drum 2a is moved to the transfer portion Ta between the photosensitive drum 2a and the transfer blade 5a, a transfer material fed from the paper feed cassette 21 through the transfer material conveyance guide 23 ( Paper) P is conveyed by the registration roller 24 to the transfer portion Ta. A yellow toner image is transferred onto the transfer material P by the transfer roller 34a to which a transfer bias (opposite polarity (positive polarity) with respect to toner) is applied to the transfer material P conveyed to the transfer portion Ta.

  The transfer material P onto which the yellow toner image has been transferred is moved to the image forming unit 1b by the transfer material conveyance belt 31. In the transfer unit Tb constituted by the image forming unit 1b and the transfer roller 34b, the magenta toner image formed on the photosensitive drum 2b in the same manner as described above is superimposed on the yellow toner image on the transfer material P. Is transcribed.

  In the same manner, cyan and black toner images formed on the photosensitive drums 2c and 2d of the image forming units 1c and 1d on the yellow and magenta toner images superimposed and transferred onto the transfer material P are similarly transferred to the transfer units Tc. , Td are sequentially overlapped to form a full-color toner image on the transfer material P.

  The transfer material P on which the full-color toner image is formed is conveyed to the fixing device 40, and the full-color toner image is heated and pressed at the fixing nip between the heating roller 41 and the pressure roller 42 to be thermally fixed on the surface of the transfer material P. After that, the paper is discharged onto the paper discharge tray 51 by the paper discharge roller 47, and the series of image forming operations is completed.

  When the above image is transferred from the photosensitive drum to the transfer material, the transfer residual toner remaining on the photosensitive drums 2a, 2b, 2c, and 2d is removed by the drum cleaning devices 5a, 5b, 5c, and 5d, respectively. And recovered.

  When outputting a monochrome image, the above-described image forming process is performed only in the image forming unit 1d that forms a black image.

(Characteristic part of the first embodiment)
Next, characteristic parts of the present embodiment will be described with reference to FIG.

  FIG. 1 schematically shows the pressure release mechanism of the fixing device 40 in FIG. 2, FIG. 1 (1) shows the pressing state of the fixing roller 41, and FIG. Indicates the pressure release state. The fixing roller 41 arranged to face the pressure roller 42 is connected at a connecting portion 44 b of the connecting member 44. The pressure spring 43 presses the fixing roller 41 against the pressure roller 42 with a predetermined pressure via the connecting member 44. The predetermined pressure is optimized by the fixing property and the conveyance property of the recording material, and is usually determined within a range of 10 to 50 kg. The pressure release cam 45 is disposed substantially opposite to the pressure spring 43 with the connecting member 44 interposed therebetween. The pressure release cam 45 is configured to be rotatable about a rotation shaft 45a in the direction of arrow B by a drive source (not shown). The pressure release cam 45 includes a cam follower surface X extending from 45b to 45c, which is the lowest point when the fixing roller is pressed, a cam follower surface Y extending from 45c to 45d, and a cam follower surface Z extending from 45d to 45e to 45b. It is configured.

  Next, the pressure release state of the fixing roller shown in FIG. 1 (2) is when the paper jam that occurs during image output is processed, when the low power mode is entered when the printer is not used for a certain period of time, and when the image is displayed. In order to prevent an unnecessary high pressure from being applied to the pressure roller and the fixing roller when the power of the forming apparatus main body is turned off, the pressure release cam is rotated. As a specific means, by rotating the pressure release cam approximately 90 °, the cam follower surface X of the pressure release cam pushes down the connecting member 44 against the urging force of the pressure spring 43, and further, the cam follower surface Y This is realized by holding the posture of the pressure release cam by the flat surface.

  Further, when the pressurization state shown in FIG. 1 (1) is reproduced from the pressure release state in order to make the image forming apparatus main body ready for image output after the paper jam processing, FIG. ) Is again rotated in the direction of arrow B by approximately 270 °, and the connecting member 44 is gradually returned to the pressurizing position by the cam follower surface Z.

  FIG. 3 is a graph showing the relationship between the height of the cam follower surface of the pressure release cam 45 and the rotation angle. Points 45b, 45c, 45d, 45e on the graph coincide with points 45b, 45c, 45d, 45e on the cam follower surface.

  When the fixing roller is moved from the pressure release state to the pressure state in this way, the pressure release cam 45 receives the biasing force of the pressure spring 43, but as shown in the graph of FIG. Since the fluctuation range per angle of the height of the cam follower surface for moving to the pressurizing state is set to be small and gentle, the urging force of the pressurizing spring 43 reaches the rotational operation of the pressurizing release cam 45 all at once. Therefore, the acceleration applied to the rotation operation of the pressure release cam 45 can be suppressed to a small level.

  Therefore, the pressurization / pressure release operation of the fixing roller can be smoothly operated without using a mechanical structure such as a braking means, and the vibration and abnormal noise of the device accompanying the acceleration by the biasing force received by the pressure release cam. It is possible to reliably prevent parts from being damaged. Further, since the acceleration by the urging force is suppressed by the rotation angle and the shape of the cam follower surface, it is possible to keep the component cost and the assembly cost low without increasing the number of components. Further, since a mechanical configuration such as a braking means is unnecessary, it is an effective means for downsizing the apparatus.

  Further, the entire fixing device is not lifted by vibration accompanying acceleration of the rotation operation of the pressure release cam, and a configuration of a lock member or the like for completely fixing the fixing device to the image forming apparatus main body is not required. Therefore, it is possible to reduce the cost and the size of the apparatus, and also improve the usability of being easily detachable.

  Further, in a fixing drive system using a single drive motor as shown in FIG. 4 and switching between the driving of the fixing driving operation and the pressure releasing operation using the swing gear, the rotation operation of the pressure releasing cam is attached. By suppressing the acceleration of the power to a small extent, it is possible to prevent the swinging gear from coming off, skipping teeth, etc., which is very effective in realizing downsizing and cost reduction of the apparatus.

  In this embodiment, the connecting member and the biasing member are arranged on the fixing roller side, and the pressing roller and the pressing release state are realized by moving the fixing roller with respect to the pressing roller. It goes without saying that the present invention is effective even if the apparatus is configured to be movable with respect to the fixing roller.

FIG. 2 is a schematic diagram illustrating a fixing device and a pressure release mechanism of the image forming apparatus according to the present invention. 1 is a schematic sectional view of an image forming apparatus according to the present invention. It is a graph showing the relationship between the cam surface height and rotation angle of the pressure release cam of the fixing device according to the present invention. 1 is a schematic diagram illustrating a fixing drive system of an image forming apparatus according to the present invention. It is a schematic diagram showing a fixing device and a pressure release mechanism of an image forming apparatus which is a conventional example.

Explanation of symbols

1a, 1b, 1c, 1d Each color image forming unit 20 Paper feeding unit 40 Fixing device 41 Fixing roller 42 Pressure roller 43 Pressure spring 44 Connecting member 45 Pressure release cam 45b, 45c, 45d, 45e Pressure release cam Each point on the cam follower surface

Claims (3)

A fixing member having an internal heat source for fixing an image on the recording material, a pressure member for pressing and conveying the recording material against the fixing member, and the fixing member to the pressure member at a predetermined pressure Image forming comprising: an urging unit for pressing; and a pressure releasing unit that acts on the urging unit and moves the pressure member to a pressing position that presses the fixing member against the pressing member and a release position that releases the pressing force. In the device
The pressure release means has a pressure release cam for releasing the pressing force,
The pressure release cam moves the fixing member alternately between the pressure position and the release position every rotation and moves the fixing member from the release position to the pressure position. The image forming apparatus is realized by causing the pressure release cam to rotate half or more times. A fixing member that has an internal heat source and fixes an image on the recording material, a pressure member that presses and conveys the recording material to the fixing member, and rotates the fixing member and the pressure member. A driving unit comprising a driving motor and a driving gear train, urging means for pressing the fixing member against the pressure member with a predetermined pressure, and acting on the urging means to make the fixing member a pressure member In an image forming apparatus having a pressure release unit that moves to a pressing position to press and a release position to release the pressing force,
The pressure release means has a pressure release cam that releases the pressing force. The drive unit has a swing gear that swings between a first position and a second position by forward and reverse rotation of the drive motor. When the drive motor rotates in the forward direction, the swing gear is disposed at the first position to rotate the fixing member and the pressure member. When the drive motor rotates in the reverse direction, the swing gear is set to the second position. The pressure release cam is arranged to be driven to rotate,
The pressure release cam moves the fixing member alternately between the pressure position and the release position every rotation and moves the fixing member from the release position to the pressure position. The image forming apparatus is realized by causing the pressure release cam to rotate half or more times.   The pressure release cam is configured to move the fixing member to the release position by rotating half or less, a cam follower surface that is flat with respect to the coupling member, and the biasing unit. The image forming apparatus according to claim 1, further comprising a cam follower surface capable of moving the fixing member to the pressure position by rotating more than half a rotation.

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