JP2011237744A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of properly feeding transfer paper with a reduced number of driving parts and components concerning the driving part.SOLUTION: An image forming apparatus comprises: an image carrier 10; a transfer part 20 which transfers a toner image formed on the image carrier 10 to a sheet P; a fixation part 30 which fixes the toner transferred on the sheet P; and a driving part which feeds the sheet P from the transfer part 20 to the fixation part 30 by rotating the image carrier 10 and the fixation part 30. A buffer mechanism 40 is arranged between the transfer part 20 and the fixation part 30 to absorb sagging caused by the feeding of sheet P.

Description

  The present invention relates to an image forming apparatus, and more particularly, to an image forming apparatus that conveys a sheet having a toner image transferred from an image carrier to a fixing device.

  As a configuration of the image forming apparatus, for example, there is a configuration as described in Patent Document 1. As shown in FIGS. 1 and 2 of Patent Document 1, this configuration includes a photoconductor, a developing unit, a fixing unit, a paper feed unit, a paper discharge unit, a unit for conveying transfer paper from the paper feed unit to the photoconductor, Each of the means for transporting the transfer paper from the fixing means to the fixing means may be provided with an independent drive unit. With this configuration, the image forming apparatus operates each drive unit to form an image on the transfer paper and is discharged to the discharge unit.

  However, such a configuration increases the number of parts due to an increase in the number of parts related to the drive part and the drive part. For this reason, the manufacturing cost of the apparatus is increased, and the management cost of the drive unit and the parts of the drive unit is also increased. In addition, it is necessary to perform control between the drive units in order to appropriately feed the transfer paper in consideration of uneven rotation of the photosensitive member, expansion / contraction of the transfer paper due to fixing, and the control becomes complicated.

JP 2003-223029 A

  The problem to be solved is that even if the number of drive units and the number of parts related to the drive units are reduced and the manufacturing cost and management cost described above are reduced, the appropriate transfer paper is fed. There is.

  In order to solve the above problems, according to the present invention, in claim 1, the image carrier, a transfer portion for transferring the toner image formed on the image carrier to the sheet, and the toner transferred to the sheet are fixed. A fixing unit; a driving unit that rotates the image carrier and the fixing unit to feed the sheet from the transfer unit to the fixing unit; and a sheet between the transfer unit and the fixing unit. A buffer mechanism is provided for absorbing sheet sagging caused by variations in feeding of the sheet.

  According to a second aspect of the present invention, the buffer mechanism is configured to convey the sheet in a state in which the sheet is guided while the sheet is guided to the fixing unit and receives the fed sheet, the normal position in which the sheet is conveyed without sagging, and the sheet is slack. And an actuating portion for shifting the guide portion to the operated position.

  Further, according to claim 3, the image forming apparatus further includes a conveyance unit that conveys the sheet to the image carrier, and the operation position is shifted when the leading edge of the sheet passes the fixing unit, and the normal position is when the trailing edge of the sheet passes. It is characterized by shifting. Further, in the fourth aspect of the present invention, the driving of the image carrier, the fixing unit, the conveying unit, and the operating unit is a single driving unit.

  In the image forming apparatus of the present invention, by providing a buffer mechanism between the transfer unit and the fixing unit, sheet sag caused by variations in sheet feeding is absorbed, and the sheet on which the toner image is formed is transferred to the image carrier or The sheet can be transported from the toner image transfer position to the fixing unit without contacting the fixing unit.

  Further, in the second aspect, the buffer mechanism receives the fed sheet, and a guide portion that guides the sheet to the fixing portion, a normal position where the sheet is conveyed without sagging, and sagging occur in the sheet. The effect of claim 1 can be obtained as a specific configuration by using the operating portion that shifts the guide portion to the operation position conveyed in the state.

  Further, in claim 3, when the leading edge of the sheet passes through the fixing portion, the guide portion is shifted to the operating position, and when the trailing end of the sheet passes through the conveying portion, the guide portion is shifted to the normal position. Two effects can be obtained.

  Further, in claim 4, the driving of the fixing unit, the conveying unit, and the operating unit is configured by a single driving unit, so that control in consideration of each driving unit and parts related to each driving unit are eliminated. The structure of the apparatus and the conveyance control can be simplified. As a result, the sheet can be conveyed appropriately even if the manufacturing cost and the management cost are reduced.

1 is a schematic diagram of an image forming apparatus of the present invention. FIG. 7 is a diagram illustrating the operation of the guide according to the present invention, in which the sheet is fed out to the fixing unit side. FIG. 6 is a diagram illustrating the operation of the image forming apparatus according to the present invention, in which the guide portion is activated to the operating position. FIG. 4 is a diagram in which a sheet is fed out from the state of FIG. 3. FIG. 5 is a diagram in which the transfer of the toner image to the sheet from the state of FIG. 4 is completed and the trailing edge of the sheet is conveyed to the fixing unit side. FIG. 6 is a diagram in which the rear end of the sheet passes through the fixing unit and the guide unit returns to the normal position.

    Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 schematically shows an image forming apparatus according to the present invention.

  As shown in FIG. 1, the image forming apparatus feeds a sheet P from a supply unit (not shown) by a conveyance unit 70, then transfers the toner image to the sheet P and fixes the toner image transferred to the sheet P. And output to the outside. Here, the sheet P is a material related to coated paper, glossy paper, plain paper, tracing paper, film, etc., a long paper that is cut to a predetermined size by cutting a roll paper, or a paper that has been cut into a standard size in advance. It is not limited to the size etc. regarding.

  Specifically, in the image forming apparatus, each part excluding the image carrier 10, the charge removal unit 100, the charging unit 200, the exposure unit 300, the developing unit 400, and the fixing unit 30 is disposed at appropriate positions around the image carrier 10. ing. The neutralization unit 100 is an eraser lamp that specifically neutralizes the surface of the image carrier 10 by erasing charges remaining on the surface of the image carrier 10. The charging unit 200 uniformly charges the surface of the image carrier 10 neutralized by the charge eliminating unit 100 to a characteristic polarity, and is specifically a corona charger.

  The exposure unit 300 forms a latent image on the surface of the image carrier 10 that is uniformly charged with data read by a scanner or the like. Specifically, the light emitting element is linearly formed by the number of image pixels. It is the arranged LED head. The developing unit 400 develops a toner image on the latent image formed on the image carrier 10. Specifically, the developing unit 400 stores a toner cartridge 406 filled with toner and toner supplied from the toner cartridge 406. A developer container 401, a developing roller 402, a layer thickness regulating portion 403 that is disposed in contact with the developing roller 402 at an appropriate pressure, and forms a constant toner thin layer on the developing roller 402; A supply roller 404 that is provided in contact with each other and supplies toner in the developing container 401 to the developing roller 402 and a stirring member 405 disposed behind the supply roller 404 are provided.

  The transfer unit 20 transfers the toner image developed on the image carrier 10 to the sheet P. Specifically, the transfer unit 21 transfers the toner image to the sheet P, and the transferred sheet P is image-carrying. It consists of a separating device 22 that separates from the body 10. The cleaning unit 500 collects toner remaining on the image carrier 10 without being transferred to the sheet P after transfer. The fixing unit 30 fixes the toner image transferred to the sheet P, and specifically includes a fixing roller and a pressure roller. The fixing unit 30 is provided with a detection unit 500 that detects the leading edge of the sheet P.

  Although not shown, the driving of each unit such as the conveyance unit 70, the image carrier 10, the fixing unit 30, and the developing unit 400 is supplied by a single driving source. More specifically, the drive from the drive source to each part is performed by a transmission means that combines a belt, a gear, or a belt and a gear. As a result, the drive sources for driving the respective units are integrated into one, these drive sources can be eliminated, and the control related to the drive and the like associated therewith can be eliminated.

  Driving means from the drive source to the transport unit 70 and the fixing unit 30 is configured so that the transport speed of the transport unit 70 is faster than the transport speed of the fixing unit 30.

  In the case where the number of driving sources is one, when the feeding speed of each part is fixed, the feeding of the sheet P in each part is likely to vary due to the components constituting the transmission means, the mechanical accuracy of each part, and the like. Here, as the mechanical accuracy, specifically, for example, the roundness of each roller of the conveyance unit 70 that conveys the sheet P and the parallelism in the axial direction of the roller are referred to.

    If this mechanical accuracy is not appropriate, for example, if the parallelism of the rollers is not appropriate, the pressure between the nips of the rollers will be uneven. As a result, the urging force for feeding out the sheet P is not uniform, the amount of feeding out the sheet P becomes uneven, a difference in the conveyance speed occurs in the conveyance unit 70 and the fixing unit 30, and the sheet P is slackened. The sheet P is pulled.

  As a result, when sagging occurs in the sheet P, the following problem is likely to occur as a specific example. For one, the sheet P contacts the image carrier 10 and the toner image formed on the image carrier 10 is broken. One is that the toner image formed on the sheet P breaks when the sheet P contacts the fixing unit 30. One is that the toner image that comes into contact with the fixing unit 30 and adheres to the above-described fixing unit 30 is sequentially fixed to the sheet P fed to the fixing unit 30.

Further, when the sheet P is pulled in the transport unit 70 and the fixing unit 30, the following problem is likely to occur as a specific example.
One is that the sheet P is displaced between the conveyance unit 70 and the position where the toner image is transferred to the sheet P, and the image is blurred. One is that the sheet P shifts from the position where the toner image is transferred to the sheet P to the fixing unit 30 and the image is blurred.

  For this reason, in order to solve the above problem by using a single drive source, it is better to use the slack of the sheet P than to prevent the image blur due to the tension of the sheet P. Judged that it was easy to solve. The reason is that in the case of mainly solving the prevention of image blur due to the pulling of the sheet P, it is necessary to increase the mechanical accuracy of the conveying unit 70, the fixing unit 30, and the transmission means related thereto, more than usual. This is because the cost for this is higher than the normal cost.

  Driving means from the drive source to the transport unit 70 and the fixing unit 30 is configured so that the transport speed of the transport unit 70 is faster than the transport speed of the fixing unit 30. In the present invention, as will be described below, attention is particularly paid to the conveyance of the sheet P between the transfer unit 20 and the fixing unit 30.

  FIG. 2 shows details of the present invention and a schematic diagram of the buffer mechanism 40. The buffer mechanism 40 is provided between the transfer unit 20 and the fixing unit 30. The buffer mechanism 40 is mainly caused by variations in the feeding of the sheet P of each part (conveying unit 70, fixing unit 30 and the like) and a difference in conveying speed for feeding out the sheet P of the conveying unit 70 and the fixing unit 30. The sheet P is absorbed.

  The buffer mechanism 40 includes a guide unit 50, an operation unit 60, and an urging unit. The guide unit 50 receives the sheet P on which the toner image is formed, and guides the sheet P to the fixing unit 30 side. The guide unit 50 is made of a plate-like member, and one end positioned on the transfer unit 20 side is freely rotatable. It is supported.

  The sub guide unit 80 guides the sheet P fed out from the guide unit 50 to the fixing unit 30. The auxiliary guide member 50 is made of a plate-like member like the guide member 50, and is provided between the guide member 50 and the fixing unit 30.

  Even if the sheet P is conveyed in a state where it is slack to the fixing unit 30, the actuating unit 60 does not allow the part of the slack sheet P to contact the fixing unit 30, and does not allow the part of the slack sheet P to contact the image carrier 10. Thus, the guide part 50 is shifted to a predetermined position.

  The operating unit 60 includes a cam unit 61 that shifts the guide unit 50 to a predetermined position, an operating shaft 62 that is connected to the transmission unit and transmits the driving force of the driving unit to the cam unit 61, and a sensor that detects the position of the guide unit 50. Part 63. Specifically, the transmission means to which the operating shaft 62 is connected is a stepping clutch.

  In addition, the predetermined position here refers to the position of the guide unit 50 where the sheet P is conveyed in a state where there is no slack. Further, as described above, even when the sheet P is conveyed in a state of being slack to the fixing unit 30, the portion of the sheet P that is slack is prevented from coming into contact with the fixing unit 30, and the portion of the slack sheet P is imaged. A position where the guide portion 50 is shifted so as not to contact the carrier 10 is referred to as an operation position.

  Further, a buffer part 90 is provided under the guide part 50. Specifically, the buffer portion 90 is a spring, and the buffer portion 90 softens the impact received by the guide portion 50 when the guide portion 50 is shifted upward and downward by the operation of the operating portion 60, and the image carrier 10 due to this impact. This prevents shaking.

  Next, the operation of the present invention will be described. As shown in FIG. 2, the sheet P is fed out from a sheet feeding unit (not shown) by the conveyance unit 70. The transferred sheet P is transferred to the sheet P by the transfer unit 20, and the sheet P on which the toner image is transferred is conveyed to the fixing unit 30 side.

  Further, when the sheet P is fed out from the state of FIG. 2 and the leading edge of the sheet P is conveyed to the fixing unit 30, the detection unit 500 detects this. When the detection unit 500 detects the leading edge of the sheet P, as shown in FIG. 3, the stepping clutch is operated and the cam unit 61 moves in the direction of the arrow through the action shaft.

  Along with this, the guide part 50 also moves downward in the direction of the arrow about the fulcrum FP of the guide part 50, and the guide part 50 is shifted to the operating position. At this time, when shifting, the buffer portion 90 receives the weight of the guide portion 50 and softens the impact caused by this.

  When the leading edge of the sheet P is conveyed to the fixing unit 30, the conveyance speed of the conveyance unit 70 is faster than the conveyance speed of the fixing unit 30. Furthermore, when the conveyance unit 70 sequentially feeds out the sheet P, the portion where the sheet P is slacked tends to fall downward as a loop due to its own weight.

  At this time, as shown in FIG. 4, in this loop, a space S formed by the transfer unit 20, the downwardly shifted guide unit 50, and the sub guide unit 80 becomes a conveyance path of the sheet P, and this space S The loop is accommodated in

  By this accommodation, the sheet P which is slack so as to keep the size of the loop constant is absorbed. Here, the constant loop size means a size such that a part of the loop is not brought into contact with the fixing unit 30 and a part of the loop is not brought into contact with the image carrier 10.

  As shown in FIG. 5, the rear end of the sheet P passes through the transfer unit 20, and the rear end of the sheet P portion passes through the fixing unit 30. Thereafter, when the detection unit 500 detects this, as shown in FIG. 6, the stepping clutch is operated and the cam unit 61 moves in the direction opposite to the arrow shown in FIG. Is shifted to the normal position.

  The present invention can also be applied to an apparatus for forming an image on a sheet, for example, an ink jet method, a thermal method, or the like.

DESCRIPTION OF SYMBOLS 10 Image carrier 20 Transfer part 30 Fixing part 40 Buffer mechanism 50 Guide part 60 Actuation part 70 Conveyance part 80 Sub guide part 90 Buffer part FP Support point P Sheet S Space

Claims (4)

An image carrier, a transfer unit that transfers a toner image formed on the image carrier to a sheet, a fixing unit that fixes the toner transferred to the sheet, and the image carrier and the fixing unit are rotated. A drive unit for feeding the sheet from the transfer unit to the fixing unit;
An image forming apparatus, wherein a buffer mechanism is provided between the transfer unit and the fixing unit to absorb the sagging of the sheet caused by the feeding of the sheet.   The buffer mechanism receives the fed sheet, guides the sheet to the fixing unit, a normal position where the sheet is conveyed without sagging, and is conveyed in a state where sagging occurs in the sheet. The image forming apparatus according to claim 1, further comprising: an operation unit that shifts the guide unit to an operation position. A transport unit that transports the sheet to the image carrier;
2. The working position is shifted when a leading end of the sheet passes through the fixing unit, and the normal position is shifted when a trailing end of the sheet passes through the fixing unit or the conveying unit. Or the image forming apparatus according to 2;   4. The image forming apparatus according to claim 1, wherein driving of the image carrier, the fixing unit, the transport unit, and the operating unit is a single driving unit. 5.

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