JP2005300847A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To ensure steady turning movement, in a composition where a transfer roll is turned to be brought into contact with an intermediate transfer body or separated therefrom. <P>SOLUTION: Since the rotating shaft 102 extends through an arm 104 and a rotation mechanism 100 is highly rigid, the arm 104 is prevented from twisting. This ensures steady rotating operation. In addition, a secondary transfer roll 80 can be brought accurately into contact with an intermediate transfer belt 64. The rotating shaft 102 faces a recording-paper transport path, such that the rotational shaft 102 is not in contact with recording paper P and is exposed beyond the width of the recording paper. Additionally, the rotating shaft is metal and conductive. Accordingly, when the recording paper passes on the rotational shaft 102, it releases charges onto the rotational shaft 102, so that the charges are removed from the recording paper P. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus.

  As an image forming apparatus for forming a color image, an image forming apparatus using the following known electrophotographic process is known.

The latent image formed on the photosensitive member is developed with each color developing device for each rotation to form a toner image, and transferred to the intermediate transfer member. Then, the color toner images are sequentially superimposed on the intermediate transfer member to form a color image. This color image is collectively transferred from the intermediate transfer member to the recording medium, and the transferred color image is fixed to the recording medium, whereby the color image is recorded on the recording medium. A color image is transferred to a recording medium through a recording medium through a nip portion between the intermediate transfer body and the transfer roll while a transfer roll is brought into contact with the intermediate transfer body and a transfer bias is applied to the transfer roll.

  Now, if the toner image of each color is superimposed on the intermediate transfer member to form a color image and the transfer roll is in contact with the intermediate transfer member, the color image is disturbed by the transfer roller. Therefore, a mechanism for contacting and separating the transfer roll from the intermediate transfer member is required except when transferring from the intermediate transfer member to the recording medium.

Therefore, there is an image forming apparatus provided with a mechanism for rotating an arm, to which a transfer roll is attached, by an eccentric cam to make contact and separation. (For example, refer to Patent Document 1).
Japanese Patent Laid-Open No. 11-161050

  However, in the method described in Japanese Patent Laid-Open No. 11-161050, the rotation center of the arm is merely a fulcrum and the rigidity is insufficient. For example, the arm is twisted and the transfer roll does not rotate stably. there is a possibility. For this reason, there is a possibility that the transfer roll cannot be brought into contact with the image carrier with high accuracy.

  Further, the arm extends from the fulcrum in the opposite direction to the transfer roll, and the spring and the cam are located on the arm portion extending from the fulcrum in the opposite direction to the transfer roll.

  The present invention has been made to solve the above problem, and an object of the present invention is to stably perform a rotating operation in a configuration in which a transfer roll is rotated to contact and separate from an intermediate transfer member.

  The image forming apparatus according to claim 1, wherein an image carrier on which a toner image is formed and a transfer that contacts the image carrier and transfers the toner image to a recording medium that passes through a nip portion with the image carrier. A roll, an arm that supports both ends of the rotation shaft of the transfer roll, and a rotation shaft that supports the arm at both ends so that the arm can rotate. And a rotation mechanism that rotates and moves the transfer roll from and to the image carrier, and the rotation shaft is provided to face the conveyance path of the recording medium.

  According to a first aspect of the present invention, the image forming apparatus includes a transfer roll that contacts the image carrier on which the toner image is formed and transfers the toner image to a recording medium that passes through a nip portion with the image carrier.

  The arms of the rotation mechanism are supported rotatably at both ends of the rotation shaft. Further, the arm supports both ends of the rotation shaft of the transfer roll. Then, the arm rotates around the rotation shaft, and the transfer roll is brought into contact with and separated from the image carrier.

  Thus, since both ends of the rotation shaft are attached to the arm, the rotation mechanism has a high rigidity. Therefore, for example, the arm is less likely to be twisted due to the turning operation. Therefore, the rotation operation is performed stably. For this reason, the transfer roll can be brought into contact with the image carrier with high accuracy.

  The recording medium passes through the nip portion between the transfer roll and the intermediate transfer member. The conveyance path of the recording medium exiting from the nip portion is approximately 90 degrees with respect to the transfer roll and the intermediate transfer member. The rotating shaft is provided facing the recording medium conveyance path. Therefore, the direction in which the arm rotates and urges the transfer roll toward the intermediate transfer member is substantially the same as the direction facing the intermediate transfer member. For this reason, it is possible to efficiently transmit the urging force that urges the transfer roll to the intermediate transfer member.

  According to a second aspect of the present invention, in the configuration according to the first aspect, the rotation mechanism includes a biasing unit that biases the arm in a direction in which the transfer roll contacts the image carrier. A cam for rotating the arm, and the urging means urges a position away from the transfer roll with respect to the rotation shaft, and the cam presses the arm to press the transfer roll. It is characterized by being separated from the image carrier.

  According to a second aspect of the present invention, the rotation mechanism includes a biasing unit that biases the arm in a direction in which the transfer roll contacts the image carrier, and a cam that rotates the arm. The cam then presses the arm to separate the transfer roll from the image carrier.

  Since the urging means urges a position away from the transfer roll with respect to the rotation shaft, the distance between the urging means and the rotation shaft is longer than the transfer roll and the rotation shaft. Therefore, the transfer roll can be urged to the intermediate transfer body with a force larger than the urging force of the urging means on the principle of leverage.

  Furthermore, since the urging means urges the position away from the transfer roll with respect to the rotation axis shaft, for example, compared with a structure in which the rotation axis shaft is provided between the urging means and the transfer roll. Even if the urging force for urging the transfer roll to the intermediate transfer member is the same, the space is saved.

  According to a third aspect of the present invention, in the configuration of the first or second aspect, the rotation shaft is exposed to the transport path.

  In the image forming apparatus according to the third aspect, since the rotation shaft is not covered with a cover or the like and is exposed to the conveyance path, for example, the cost is low and the transfer is performed by a compact rotation mechanism. The roll can be efficiently urged to the intermediate transfer member.

  According to a fourth aspect of the present invention, in the configuration according to the third aspect, the rotation shaft is conductive.

  In the image forming apparatus according to the fourth aspect, when the recording medium is transported, for example, the recording medium comes into contact with various members in the transport path and is charged. For this reason, the toner image transferred to the recording medium may be disturbed by static electricity and deteriorate the image quality. Therefore, it is desirable to neutralize the charged recording medium.

  The rotation shaft faces the conveyance path and is exposed to the conveyance path. Moreover, it has electroconductivity. Therefore, when the recording medium is conveyed on the conveyance path portion facing the rotation shaft, the discharge is discharged to the rotation shaft.

  According to a fifth aspect of the present invention, in the configuration of the fourth aspect, the rotating shaft is not grounded.

  The image forming apparatus according to the fifth aspect has the same effect as that of the fourth aspect, but the rotating shaft is not grounded, and therefore the recording medium is not rapidly discharged. Therefore, image disturbance due to rapid charge removal is prevented.

  According to a sixth aspect of the present invention, in the configuration of the fourth aspect, the rotating shaft is grounded through a resistor.

  The image forming apparatus according to the sixth aspect has the same effect as that of the fourth aspect, but the rotating shaft is grounded via a resistor, so that the recording medium is not rapidly discharged. Therefore, image disturbance due to rapid charge removal is prevented.

  According to a seventh aspect of the present invention, in the configuration of the fourth aspect, the rotating shaft is grounded via a diode.

  The image forming apparatus according to the seventh aspect has the same operation as that according to the fourth aspect. However, since the rotating shaft is grounded via the diode, the recording medium is not suddenly discharged. Therefore, image disturbance due to rapid charge removal is prevented.

  An image forming apparatus according to an eighth aspect of the present invention is the configuration according to any one of the fourth to seventh aspects, in which the rotating shaft shaft is downstream of the transfer roll with respect to the conveyance direction of the recording medium. It is characterized by being on the side.

  In the image forming apparatus according to the eighth aspect, the rotation shaft is on the downstream side of the transfer roll with respect to the conveyance direction of the recording medium. Therefore, the recording medium is neutralized by the rotary shaft after the transfer roll. Therefore, it is possible to prevent the recording medium from being wound around without being peeled from the intermediate transfer member due to static electricity.

  An image forming apparatus according to a ninth aspect is the configuration according to any one of the fourth to seventh aspects, wherein the rotating shaft shaft is upstream of the transfer roll with respect to a conveyance direction of the recording medium. It is characterized by being on the side.

  In the image forming apparatus according to the ninth aspect, the rotation shaft is on the upstream side of the transfer roll with respect to the conveyance direction of the recording medium. Therefore, before the toner image is transferred to the recording medium, the charge is eliminated by the rotating shaft. For this reason, even if the recording medium comes into contact with the rotating shaft for some reason and the charge is suddenly removed, the toner image transferred to the recording medium is hardly affected. Therefore, the position accuracy of the rotary shaft may be rough.

  As described above, according to the present invention, since both ends of the rotation shaft are attached to the arm, the rotation mechanism has high rigidity. Therefore, the rotation operation is performed stably.

  Hereinafter, as an example to which the image forming apparatus according to the present invention is applied, a color printer to which a known electrophotographic process is applied will be described with reference to the drawings. The image forming apparatus to which the present invention is applied is not limited to a color printer described below, and may be an image forming apparatus such as a copying machine, a facsimile machine, or a multifunction machine.

  A first embodiment of the present invention will be described with reference to the drawings. In the following description, detailed descriptions of those not directly related to the essence of the present invention are omitted.

  FIG. 1 shows an outline of a color printer 10 according to an embodiment of the present invention.

  The color printer 10 includes a color printer main body 12, and an open / close cover 16 that is rotatable about a rotation fulcrum 14 is provided on the upper portion of the color printer main body 12. In addition, a paper feeding unit 18 is disposed below the color printer main body 12.

  The paper supply unit 18 includes a paper supply unit main body 20 and a paper supply cassette 22 in which the recording paper P is stored. A feed roll 24 that feeds recording paper P from the paper feed cassette 22 and a retard roll 26 that scoops the supplied recording paper P one by one are arranged in the upper part near the rear end of the paper feed cassette 22.

  The conveyance path 28 is a path for the recording paper P from the feed roll 24 to the discharge port 30. The conveyance path 28 is in the vicinity of the back side (right side in FIG. 1) of the color printer main body 12 and is formed substantially vertically from the paper feeding unit 18 to the fixing device 90. A secondary transfer roll 80 and a secondary transfer backup roll 72 are arranged on the upstream side of the fixing device 90 in the conveyance path 28, and a resist roll 32 is arranged on the upstream side of the secondary transfer roll 80 and the secondary transfer backup roll 72. Has been. In addition, a discharge roll 34 is disposed in the vicinity of the discharge port 30 of the conveyance path 28.

  Accordingly, the recording paper P sent out from the paper feeding cassette 22 of the paper feeding unit 18 by the feed roll 24 is turned by the retard roll 26 and only the uppermost recording paper P is guided to the transport path 28, and is fed by the registration roll 32. The toner image is transferred between the secondary transfer roll 80 and the intermediate transfer belt 64 (secondary transfer backup roll 72) at a timing, and is guided by the guide member 150 and sent to the fixing device 90. It is done. The recording sheet to which the toner image has been transferred is fixed by the fixing device 90 and is discharged from the discharge port 30 to the discharge portion 36 provided on the upper portion of the opening / closing cover 16 by the discharge roll 34. The discharge portion 36 has a low discharge port portion and is inclined so as to gradually increase toward the front direction (left direction in FIG. 1).

  The color printer main body 12 is provided with a rotary developing device 38 at a substantially central portion. The rotary developing device 38 includes developing units 42a to 42d that respectively form toner images of four colors of yellow, yellow, magenta, cyan, and black in the developing unit main body 40. It rotates counterclockwise (counterclockwise in FIG. 1) about the rotary developing device center 44. Each of the developing units 42a to 42d has developing rolls 46a to 46d, and is pressed in the normal direction of the developing unit main body 40 by elastic bodies 48a to 48d such as coil springs.

  The rotary developing device 38 is arranged so that the photosensitive drum 50 rotating about the rotation support shaft 49 is in contact with each other, and the developing rolls 46a to 46d are not in contact with the photosensitive drum 50, respectively. A part of the outer periphery of the developing device protrudes from the outer periphery of the developing device main body 40 in the radial direction by about 2 mm. Further, a tracking roll (not shown) having a diameter slightly larger than the diameter of the developing rolls 46a to 46d is provided at both ends of each of the developing rolls 46a to 46d so as to rotate coaxially with the developing rolls 46a to 46d. Yes. In other words, the developing devices 42 a to 42 d are arranged on the outer periphery of the developing device main body 40 at intervals of 90 ° with the rotary developing device center 44 as the center, and the tracking rolls of the developing rollers 46 a to 46 d are disposed at both ends of the photosensitive drum 50. While contacting a provided flange (not shown) and forming a predetermined gap between the developing rolls 46a to 46d and the photosensitive drum 50, the latent image on the photosensitive drum 50 is made of toner of each color. develop.

  A charging roll 52 is provided below the photosensitive drum 50, and a charging bias is applied to the charging roll 52 to uniformly charge the photosensitive drum 50. A photosensitive drum cleaner 54 is provided so as to hang from the rotation spindle 49 of the photosensitive drum 50, and the photosensitive drum 50 and the photosensitive drum cleaner 54 are integrated. The cleaning blade 56 scrapes off the waste toner remaining on the photosensitive drum 50 after the primary transfer. The toner collecting case 58 collects the waste toner scraped off by the cleaning blade 56.

  Note that a rib or the like is formed on the back side (right side in FIG. 1) of the toner recovery case 58, and the recording paper P is curved to form a part of the transport path 28.

  On the lower back side of the rotary developing device 38, an exposure device 60 for writing a latent image on the photosensitive drum 50 charged by the charging roll 52 with a light beam such as a laser beam is disposed. Above the rotary developing device 38, the toner image visualized by the rotary developing device 38 is primarily transferred at the primary transfer position, and then transferred to the secondary transfer position A (the secondary transfer roll 80 and the secondary transfer backup roll 72). An intermediate transfer device 62 that conveys the toner to the nip portion) is provided.

  The intermediate transfer device 62 includes an intermediate transfer belt 64, a primary transfer roll 66, a wrap-in roll 68, a wrap-out roll 70, a secondary transfer backup roll 72, a scraper backup roll 74, a brush backup roll 76, and the like.

  The intermediate transfer belt 64 has elasticity and is stretched substantially flat so as to have a long side and a short side above the rotary developing device 38. The long sides on the upper and lower sides of the intermediate transfer belt 64 are stretched so as to be substantially parallel to the discharge portion 36 provided on the upper portion of the color printer body 12.

  The intermediate transfer belt 64 is positioned between a wrap-in roll 68 disposed upstream of the primary transfer roll 66 below the long side of the intermediate transfer belt 64 and a wrap-out roll 70 disposed downstream of the primary transfer roll 66. Thus, the photosensitive drum 50 has a primary transfer portion (photosensitive drum wrap region) that contacts the photosensitive drum 50 in a wrap shape, is wound around the photosensitive drum 50 by a predetermined range, and is driven by the rotation of the photosensitive drum 50. As described above, the intermediate transfer belt 64 primarily transfers the toner image on the photosensitive drum 50 by the primary transfer roll 66 in the order of yellow, magenta, cyan, and black, and the primary transferred toner image is secondary-transferred. It is conveyed toward the transfer roll 80. Note that the wrap-in roll 68 and the wrap-out roll 70 are separated from the photosensitive drum 50.

  As described above, the intermediate transfer belt 64 is stretched by the five rolls of the wrap-in roll 68, the wrap-out roll 70, the secondary transfer backup roll 72, the scraper backup roll 74, and the brush backup roll 76, and the primary transfer roll 66, the toner image on the photosensitive drum 50 is transferred.

  Further, a flat portion (short side) is formed on the back side (right side surface in FIG. 1) of the intermediate transfer belt 64 by a wrap-out roll 70 and a secondary transfer backup roll 72, and this flat portion is the secondary transfer portion. It faces the transport unit 28.

  In the secondary transfer portion, the wrap-out roll 70 is disposed so that the intermediate transfer belt 64 and the conveyance path 28 are at an angle of about 12 °.

  A scraper backup roll 74 assists the scraper 84 to scrape waste toner remaining on the intermediate transfer belt 64 after the secondary transfer, and a brush backup roll 76 removes waste toner remaining on the intermediate transfer belt 64 after the secondary transfer. Helps the brush roll 86 to scrape.

  A reflective photosensor 78 is provided above the long side of the intermediate transfer belt 64 by being fixed to the back surface (inside) of the open / close cover 16. The reflective photosensor 78 reads a toner patch formed on the intermediate transfer belt 64, detects the position of the intermediate transfer belt 64 in the rotational direction, and detects the density of the toner image.

  A secondary transfer roll 80 is opposed to the secondary transfer backup roll 72 of the intermediate transfer device 62 with the conveyance path 28 interposed therebetween. That is, a secondary transfer position A in the secondary transfer portion is between the secondary transfer roll 80 and the secondary transfer backup roll 72, and the secondary transfer roll 80 is assisted by the secondary transfer backup roll 72. The toner image primarily transferred to the intermediate transfer belt 64 is secondarily transferred to the recording paper P at the secondary transfer position A. Here, the secondary transfer roll 80 is primarily transferred by the rotation mechanism 100 while the intermediate transfer belt 64 rotates three times, that is, the toner images of three colors of yellow, magenta, and cyan are superimposed on the intermediate transfer belt. While being conveyed, it is separated from the intermediate transfer belt 64, and is brought into contact with the intermediate transfer belt 64 when a black toner image is transferred. (Details of the rotation mechanism 100 will be described later).

  A transfer bias is applied to the secondary transfer port 80 so that a predetermined potential difference is generated between the secondary transfer roll 80 and the secondary transfer backup roll 72. Connected to ground (GND).

  An intermediate transfer belt cleaner 82 is provided at the end of the intermediate transfer belt 64 on the side opposite to the photosensitive drum 50. The intermediate transfer belt cleaner 82 includes a scraper 84, a brush roll 86, a toner collection case 88 and a rotation support shaft 89, and swings about the rotation support shaft 89. The scraper 84 scrapes off and cleans waste toner remaining on the intermediate transfer belt 64 after the secondary transfer. The brush roll 86 further scrapes off the waste toner remaining after cleaning by the scraper 84. The toner collecting case 88 collects the waste toner cleaned by the scraper 84 and the brush roll 8. The scraper 84 is made of a thin stainless steel plate, and a voltage having a polarity opposite to that of the toner is applied.

  The brush roll 86 is made of a brush such as acrylic that has been subjected to a conductive treatment. While the intermediate transfer belt 64 conveys the toner image, the scraper 84 and the brush roll 86 are separated from the intermediate transfer belt 64 and come into contact with the intermediate transfer belt 64 at a predetermined timing. Has been.

  A fixing device 90 is disposed above the secondary transfer position A. The fixing device 90 includes a heating roll 92 and a pressure roll 94, and fixes the toner image secondarily transferred to the recording paper P by the secondary transfer roll 80 and the secondary transfer backup roll 72 to the recording paper P. It is conveyed toward the discharge roll 34. The discharge roll 34 discharges the recording paper P from the discharge port 30 to a discharge unit 36 provided at the upper part of the opening / closing cover 16.

  The intermediate transfer device 62, the photosensitive drum 50, the charging roll 52, the photosensitive drum cleaner 54, and the intermediate transfer belt cleaner 82 are integrated to constitute an image forming unit 96. The image forming unit 96 is disposed immediately below the discharge portion 36 of the opening / closing cover 16 and is detachable from the color printer main body 12. The image forming unit 96 is attached / detached by opening the opening / closing cover 16.

  2 to 4 show the rotation mechanism 100. FIG.

  As shown in FIG. 2, the rotation shaft 101 of the secondary transfer roll 80 is rotatably supported by the arms 104 and 114. Further, a metallic rotation shaft 102 penetrates the arms 104 and 114, and supports the arms 104 and 114 so as to be rotatable. Further, both ends of the rotation shaft 102 are fixed to a housing (not shown).

  In addition, since the rotation mechanism 100 has the same configuration on the left and right, it will be described as arms 104, 114, etc. in the following description, but only one (arm 104 side) is shown in the drawings after FIG. . A spring 108 and an eccentric cam 106 described below are also configured as a pair on the left and right.

  As shown in FIG. 3, the arms 104 and 114 have an L-shape composed of the arms 104a and 114a and the arms 104b and 114b.

  The rotation shaft 102 is rotatably fixed to a branch portion (L-shaped corner) between the arms 104a and 114a and the arms 104b and 114b. One end side of the spring 108 is attached to the ends of the arms 104a and 114a, and the other end side is fixed to a housing or the like (not shown). Therefore, the springs 108 urge the arms 104 and 114 in the direction in which the secondary transfer roll 80 contacts the intermediate transfer belt 64. An eccentric cam 106 is disposed so as to be detachable from the arms 104b and 114b. The eccentric cam 106 is rotated by driving means (not shown).

  Therefore, when the eccentric cam 106 is at the position shown in FIG. 4A, the eccentric cam 106 is separated from the arms 104b and 114b, so that the secondary transfer roll 80 is moved to the intermediate transfer belt 64 by the biasing force of the spring 108. Is being energized. However, when the eccentric cam 106 is rotated to the position shown in FIG. 4B, the eccentric cam 106 lifts the arms 104 b and 114 b upward, and the secondary transfer roll 80 is separated from the intermediate transfer belt 64. That is, the arms 104 and 114 rotate about the rotation axis shaft 102 as a rotation axis, and the secondary transfer roll 80 comes into contact with and separates from the intermediate transfer belt 64.

  As shown in FIG. 3, the rotation shaft 102 is positioned downstream of the secondary transfer roll 80 with respect to the conveyance direction of the recording paper P. Further, it faces the conveyance path 28 of the recording paper P. However, the position is not in contact with the recording paper P.

  Further, as shown in FIG. 2, the space between the left and right arms 104 and 114 extends over the width of the recording paper P. Thus, since the rotation shaft 102 is configured to penetrate the arms 104 and 114, the rotation mechanism 100 as a whole has high rigidity. The rotating shaft 102 is grounded via a resistor 120 having a predetermined resistance value. Further, the rotating shaft 102 is not covered with a cover or the like and is exposed to the transport path 28.

  Next, the operation of the above embodiment will be described.

  As shown in FIG. 1, when an image forming signal is sent, the photosensitive drum 50 is uniformly charged by the charging roll 52, and the charged photosensitive drum 50 receives light from the exposure device 60 based on the image signal. Is emitted. The light beam from the exposure device 60 exposes the surface of the photosensitive drum 50 to form a latent image. The latent image on the photosensitive drum 50 formed by the exposure device 60 is developed sequentially with yellow, magenta, cyan, and black toner images by the rotary developing device 38, and the respective color toner images are sequentially applied to the intermediate transfer belt 64. A color image is formed by superimposing and superimposing the images. In the primary transfer, waste toner remaining on the photosensitive drum 50 is scraped off and collected by the cleaning blade 56.

  As described above, when the toner images of the respective colors are superimposed on the intermediate transfer belt 64 to form a color image, if the secondary transfer roll 80 is in contact with the intermediate transfer belt 64, the secondary transfer roll 80. The color image is disturbed. Therefore, as shown in FIG. 4B, the arms 104 and 114 of the rotation mechanism 100 are rotated to separate the secondary transfer roll 80 from the intermediate transfer belt 64.

  On the other hand, the recording paper P stored in the paper feed cassette 22 is sent out by the feed roll 24 by the paper feed signal, turned by the retard roll 26 and guided to the transport path 28, and temporarily stopped by the registration roll 32. And is conveyed toward the guide member 29. The guide member 29 guides the recording paper P to the secondary transfer position A.

  Immediately before the recording paper P is guided to the secondary transfer position A, the arms 104 and 114 are rotated to bring the secondary transfer roll 80 into contact with the intermediate transfer belt 64 as shown in FIG. Keep it.

  When the recording paper P passes through the nip portion (secondary transfer position A) between the intermediate transfer belt 64 (secondary transfer backup roll 72) and the secondary transfer roll 80, a transfer bias is applied to the secondary transfer roll 80. As a result, the toner image primarily transferred to the intermediate transfer belt 64 is secondarily transferred to the recording paper P. Waste toner remaining on the intermediate transfer belt 64 after the secondary transfer is scraped off and collected by the intermediate transfer belt cleaner 82.

  The recording paper P onto which the toner image has been transferred is guided to the fixing device 90 by the guide member 150, and the toner image is fixed by the thermal pressure by the heating roll 92 and the pressure roll 94. The recording paper P on which the toner image is fixed is discharged from the discharge port 30 to the discharge unit 36 by the discharge roll 34.

  The secondary transfer roll 80 needs to be brought into contact with the intermediate transfer belt 64 (secondary transfer backup roll 72) with a predetermined pressing force. Therefore, in order to perform the rotation operation, the rotation mechanism 100 needs to have a predetermined rigidity. As described above, since the rotation shaft 102 is configured to penetrate the arms 104 and 114 and the rotation mechanism 100 has high rigidity, the arms 104 and 114 are not twisted. Therefore, the operation | movement stable with respect to rotation operation can be performed. Further, the secondary transfer roll 80 can be brought into contact with the intermediate transfer belt 64 with high accuracy.

  As shown in FIG. 3, the recording paper P passes through the nip portion (secondary transfer position A) between the secondary transfer roll 80 and the intermediate transfer belt 64 (secondary transfer backup roll 72). The conveyance path 28 of the recording paper P exiting from the nip portion is in a direction of approximately 90 degrees with respect to the secondary transfer roll 80 and the secondary transfer backup roll 72. As described above, the rotation shaft 102 faces the conveyance path 28 of the recording paper P. Therefore, the arms 104 and 114 rotate and the secondary transfer roll 80 biases the secondary transfer roll 80 to the intermediate transfer belt 64 (secondary transfer backup roll 72). The direction is substantially the same as the direction facing the roll 72). Therefore, it is possible to efficiently transmit the urging force that urges the secondary transfer roll 80 to the intermediate transfer belt 64 (secondary transfer backup roll 72).

  Further, the distance between the contact position of the spring 108 with the arm 104 a and the rotation axis shaft 102 is longer than the distance between the rotation axis 101 of the secondary transfer roll 80 and the rotation axis shaft 102. Therefore, on the principle of leverage, the secondary transfer roll 80 is biased to the intermediate transfer belt 64 (secondary transfer backup roll 72) with a force larger than the biasing force of the spring 108.

  Further, the spring 108 biases the position away from the secondary transfer roll 80 with respect to the rotation shaft 102. (The secondary transfer roll 80 is positioned between the spring 108 and the rotary shaft 102). Therefore, space is saved as compared with a configuration in which a rotary shaft is provided between the spring and the secondary transfer roll (see, for example, FIG. 2 of JP-A-11-161050).

  Further, since the eccentric cam 106 contacts the branched arms 104b and 114b, the distance between the rotating shaft 102 and the contact position of the eccentric cam 106 is long. Therefore, even if the driving force of the eccentric cam 106 is small due to the lever principle, the secondary transfer roll 80 can be separated by rotating the arms 104 and 114.

  Furthermore, since the arms 104 and 114 are L-shaped, the contact positions of the arms 104 b and 114 b of the eccentric cam 106 are arranged on the secondary transfer roll 80 side with respect to the rotating shaft 102. Therefore, space is saved as compared with the side opposite to the secondary transfer roll (for example, see FIG. 2 of JP-A-11-161050) with respect to the rotation shaft.

  Now, when the recording paper P is conveyed, it contacts the guide member 29 and is charged. Further, the secondary transfer roll 80 is also charged by the transfer bias.

  When the recording paper P is charged in this way, the recording paper P is hardly peeled off from the intermediate transfer belt 64 by electrostatic force, and may be wound around the intermediate transfer belt 64. In addition, the toner image secondarily transferred to the recording paper P may be disturbed by static electricity and deteriorate image quality. Therefore, it is desirable to perform charge removal on the charged recording paper P.

  As shown in FIG. 3, the rotation shaft 102 is located on the downstream side with respect to the conveyance direction of the recording paper P of the secondary transfer roll 80. Further, it faces the conveyance path 28 of the recording paper P. However, the position is not in contact with the recording paper P. Further, as shown in FIG. 2, the recording paper P is exposed over the width. The rotating shaft 102 is metallic and conductive.

  Therefore, when the recording paper P passes over the rotating shaft 102, the recording paper P is discharged and discharged. Therefore, the above-described recording paper P is prevented from being wound around the intermediate transfer belt 64 and the toner image on the recording paper P is not disturbed.

  If the charge is suddenly removed, the secondary transferred toner image is disturbed and the image quality is deteriorated. Further, when the recording paper P comes into contact with the rotating shaft 102 for some reason, the transfer bias applied to the secondary transfer roll 80 is transmitted to the rotating shaft 102 through the recording paper P, and the secondary to the recording paper P is transferred. The transfer is hindered, and the image quality is deteriorated.

  However, as shown in FIG. 2, since the rotating shaft 102 is grounded via the resistor 120, the charge is gradually removed. Therefore, the secondary-transferred toner image is disturbed and the image quality is unlikely to deteriorate. Further, even if the recording paper P comes into contact with the rotating shaft 102 for some reason, the transfer bias is transmitted through the recording paper P and hardly flows to the rotating shaft 102. Therefore, secondary transfer onto the recording paper P is not hindered.

  Further, since the rotation shaft 102 is not covered with a cover or the like and is exposed to the conveyance path 28, the cost is low, and the secondary transfer roll 80 is attached to the intermediate transfer belt 64 by a compact opening mechanism. Can be energized efficiently.

  Next, a second embodiment of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the member demonstrated in 1st Embodiment, and the overlapping description is abbreviate | omitted.

  As shown in FIG. 5, the rotation shaft 102 of the rotation mechanism 200 of the color printer 11 according to the second embodiment is located upstream with respect to the conveyance direction of the recording paper P of the secondary transfer roll 80. . Further, by rotating the eccentric cam 206, the secondary transfer roll 80 contacts and separates from the intermediate transfer belt 64.

  Next, the operation of the above embodiment will be described.

  The second embodiment also has the same effect as the first embodiment, but has the following different effects.

  In the first embodiment, as shown in FIG. 3, the rotation shaft 102 is positioned on the downstream side with respect to the conveyance direction of the recording paper P of the secondary transfer roll 80. That is, the recording paper P is neutralized after the secondary transfer. For this reason, when the recording paper P comes into contact with the rotation shaft 102 for some reason, the toner image on the recording paper P is disturbed depending on various conditions, even through the resistor 120 (see FIG. 2). May deteriorate. For this reason, it is necessary to design the position of the rotation shaft 102 and the conveyance control of the recording paper P with high accuracy so as not to make contact as much as possible.

  On the other hand, in the second embodiment, as shown in FIG. 5, the rotation shaft 102 is positioned on the upstream side with respect to the conveyance direction of the recording paper P of the secondary transfer roll 80. Therefore, the rotating shaft 102 is neutralized before the secondary transfer of the recording paper P. Therefore, even if the recording paper P comes into contact with the rotary shaft 102 for some reason and is discharged rapidly, the toner image after the secondary transfer is not disturbed and the image quality is not deteriorated. Therefore, the positional accuracy of the rotation shaft 102 and the conveyance control of the recording paper P may be rough as compared with the first embodiment.

  The present invention is not limited to the above embodiment.

  For example, in the above embodiment, the rotating shaft 102 is grounded via the resistor 120, but the present invention is not limited to this. For example, it may be grounded via a diode. Alternatively, it may be in an electrically floating state without being grounded.

  Further, for example, the rotation shaft 102 is exposed to the conveyance path 28, but is not limited thereto. Even if the rotation shaft 102 faces the conveyance path 28, for example, a guide member or the like for guiding the conveyance of the recording paper P may be disposed between the rotation shaft 102 and the conveyance path 28. In this case, the neutralizing action of the recording paper P by the rotating shaft is not achieved.

  Further, for example, a recording medium other than the recording paper P may be used. For example, an OHP sheet may be used.

1 is a cross-sectional view schematically showing the inside of a color printer according to a first embodiment of the present invention. FIG. 2 is a front view schematically showing a rotation mechanism of the color printer according to the first embodiment of the present invention. It is a side view which shows typically the rotation mechanism of the color printer which concerns on the 1st Embodiment of this invention. 1 schematically shows a rotation mechanism of a color printer according to a first embodiment of the present invention, where (a) shows a state in which a secondary transfer roll is in contact with an intermediate transfer belt, and (b) shows an arm that rotates. The secondary transfer roll is separated from the intermediate transfer belt. FIG. 4 schematically shows a rotation mechanism of a color printer according to a second embodiment of the present invention, where (a) shows a state in which a secondary transfer roll is in contact with an intermediate transfer belt, and (b) shows an arm that rotates. The secondary transfer roll is separated from the intermediate transfer belt.

Explanation of symbols

10 Color printer (image forming device)
64 Intermediate transfer belt (image carrier)
80 Secondary transfer roll (transfer roll)
DESCRIPTION OF SYMBOLS 100 Rotating mechanism 101 Rotating shaft 102 Rotating shaft shaft 104 Arm 106 Eccentric cam (cam)
108 Spring (biasing means)
114 Arm 120 Resistance
P Recording paper (recording medium)

Claims (9)

An image carrier on which a toner image is formed;
A transfer roll for contacting the image carrier and transferring the toner image to a recording medium passing through a nip with the image carrier;
An arm that supports both ends of the rotation shaft of the transfer roll, and a rotation shaft that supports the arm at both ends so that the arm can rotate. The arm rotates around the rotation shaft. A rotating mechanism for moving the transfer roll away from the image carrier;
With
The image forming apparatus, wherein the rotation shaft is provided facing a conveyance path of the recording medium. The rotation mechanism is
An urging means for urging the arm in a direction in which the transfer roll contacts the image carrier;
A cam for rotating the arm;
With
The urging means urges a position away from the transfer roll with respect to the rotation shaft, and the cam presses the arm to separate the transfer roll from the image carrier. Item 2. The image forming apparatus according to Item 1.   The image forming apparatus according to claim 1, wherein the rotation shaft is exposed to the conveyance path.   The image forming apparatus according to claim 3, wherein the rotation shaft is conductive.   The image forming apparatus according to claim 4, wherein the rotation shaft is not grounded.   The image forming apparatus according to claim 4, wherein the rotation shaft is grounded through a resistor.   The image forming apparatus according to claim 4, wherein the rotation shaft is grounded via a diode.   The image forming apparatus according to claim 4, wherein the rotation shaft is located downstream of the transfer roll with respect to a conveyance direction of the recording medium.   The image forming apparatus according to claim 4, wherein the rotation shaft is on the upstream side of the transfer roll with respect to a conveyance direction of the recording medium.

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