JP2008225409A - Image forming apparatus and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To discharge a recording sheet neither too much nor too little after transferring a toner image. <P>SOLUTION: An image forming apparatus 10 includes: an image carrier 12 carrying the toner image; a transfer member 34 forming a transfer area 36 for transferring the toner image to the recording sheet 46 at a nip part between the image carrier 12 and the transfer member 34; a pair of fixing members 50a and 50b provided to the downstream side of the transfer area 36 in the conveying direction of the recording sheet 46 and arranged to be opposed to each other; and a discharging member 100 arranged near the part of the recording sheet 46 striding over the transfer area 36 and a fixing area 52 formed at a nip part between the pair of fixing members 50a and 50b and discharging the recording sheet 46. By using the image forming apparatus 10, an effect that the flexure amount L1 at the part of the recording sheet 46 striding over the transfer area 36 and the fixing area 52 is under a predetermined amount or equal to or above the predetermined amount is detected, and the flexure amount L1 is controlled to at least either the amount equal to or above the predetermined amount or the amount under the predetermined amount on the basis of the detection, thereby controlling a distance D between the recording sheet 46 and the discharging member 100. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electrophotographic image forming apparatus and an image forming method, and in particular, to an image forming apparatus such as a copying machine, a printer, a facsimile, or a multifunction machine having these functions combined, and these image forming apparatuses. The present invention relates to an image forming method to be used.

  In a monochrome image forming apparatus, when a toner image is formed on a photoconductor during an image forming operation, the toner image is transferred from the photoconductor to a recording sheet. On the other hand, in a color image forming apparatus, when a toner image is formed on a photoreceptor during an image forming operation, the toner image is transferred (primary transfer) from the photoreceptor to the intermediate transfer belt, and then the intermediate transfer belt. To the recording sheet (secondary transfer).

  In both of the monochrome image forming apparatus and the color image forming apparatus, when the toner image is transferred to the recording sheet, the recording sheet is a nip portion between the image carrier (photosensitive member or intermediate transfer belt) and the transfer member. Since the transfer bias is applied to the transfer member, the recording sheet passing through the transfer region is charged by the transfer bias.

  After the transfer, if the recording sheet is peeled off from the image bearing member while being charged, a peeling discharge occurs, and there is a possibility that the toner is scattered at the portion where the peeling discharge is generated, resulting in an image defect.

  In order to avoid such a problem, a technique has been proposed in which a charge removal member is disposed in the vicinity of the recording sheet conveyance path on the downstream side of the transfer region in the recording sheet conveyance direction to discharge the recording sheet.

  If the recording sheet is excessively discharged, the charge amount at the time of transfer may be insufficient and transfer defects may occur. On the other hand, if the discharge of the recording sheet is insufficient, peeling discharge cannot be reliably prevented. Therefore, it is desirable to appropriately control the charge removal amount of the recording sheet. Further, the amount by which the recording sheet is neutralized by the neutralization member varies depending on the distance between the recording sheet and the neutralization member, and the neutralization amount increases as the neutralization member is closer to the recording sheet.

From this point of view, Patent Document 1 proposes a technique for controlling the amount of charge removal of the recording sheet by the charge removal member by movably providing the charge removal member and controlling the distance between the recording sheet and the charge removal member. .
JP-A-6-36887

  By the way, the recording sheet after the transfer of the toner image is conveyed to a nip portion (fixing area) of a pair of fixing rollers arranged on the downstream side in the conveying direction, and is in a state straddling the transfer area and the fixing area. In this state, in order to prevent the recording sheet tension from acting on the fixing roller to cause a fixing failure, a deflection (loop) is formed in the recording sheet at a portion extending between the transfer region and the fixing region. Since the deflection amount (loop amount) of the recording sheet formed in this way is not constant, the distance between the recording sheet and the charge removal member varies as the deflection amount changes.

  However, in the technique of Patent Document 1, since the change in the deflection amount of the recording sheet is not taken into consideration and the configuration is such that the charge removal amount of the recording sheet is controlled only by switching the arrangement of the charge removal member. The distance to the member cannot be appropriately controlled, and there is a drawback that the charge removal amount cannot always be appropriately controlled.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus and an image forming method that can discharge a recording sheet without excess or deficiency after transfer of a toner image.

In order to solve the above problems, an image forming apparatus according to the present invention provides:
An image carrier for carrying a toner image;
A transfer member disposed opposite to the image carrier and forming a transfer region for transferring a toner image to a recording sheet at a nip portion with the image carrier;
A pair of fixing members provided on the downstream side of the transfer region in the recording sheet conveyance direction and arranged to face each other;
A neutralizing member disposed near a portion of the recording sheet straddling the fixing region formed in the nip portion of the pair of fixing members and the transfer region, and neutralizing the recording sheet;
A distance control means for controlling the distance between the recording sheet and the charge eliminating member;
The distance control means includes
A deflection amount detecting means for detecting that the deflection amount of the portion of the recording sheet straddling the transfer region and the fixing region is less than a predetermined amount or more than a predetermined amount;
And a deflection amount control means for controlling the deflection amount to at least one of the predetermined amount or more or less than the predetermined amount based on the detection by the deflection amount detection means.

  Here, the amount of deflection is the distance between the actual recording sheet portion straddling the transfer region and the fixing region and the recording sheet portion when it is assumed that the sheet passes without being bent between the transfer region and the fixing region. The maximum value of.

An image forming method according to the present invention includes:
An image carrier for carrying a toner image;
A transfer member disposed opposite to the image carrier and forming a transfer region for transferring a toner image to a recording sheet at a nip portion with the image carrier;
A pair of fixing members provided on the downstream side of the transfer region in the recording sheet conveyance direction and arranged to face each other;
An image forming apparatus comprising: a fixing region formed at a nip portion of the pair of fixing members; and a neutralizing member disposed near a portion of the recording sheet straddling the transfer region and neutralizing the recording sheet. A method of forming an image,
Detecting that the amount of deflection of the portion of the recording sheet straddling the transfer area and the fixing area is less than a predetermined amount or more than a predetermined amount;
Based on the detection, by controlling the deflection amount to at least one of the predetermined amount or more or less than the predetermined amount,
The distance between the recording sheet and the charge eliminating member is controlled.

  According to the present invention, the amount of deflection of the recording sheet portion extending between the transfer region and the fixing region is detected, and by controlling the amount of deflection, the distance between the charge eliminating member that neutralizes the recording sheet and the recording sheet is accurately determined. Therefore, after the toner image is transferred, it is possible to reliably prevent the recording sheet from being discharged excessively to cause a transfer failure or to cause an image failure due to a peeling discharge due to insufficient discharge.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the accompanying drawings. In the following description, terms indicating a specific direction (for example, “up”, “down”, “left”, “right”, and other terms including them, “clockwise direction”, “counterclockwise” ”) Is used to facilitate understanding of the invention with reference to the drawings, and the present invention should not be construed as being limited by the meaning of these terms. Further, in the image forming apparatus and the developing apparatus described below, the same reference numerals are used for the same or similar components.

[1. Image forming apparatus]

  FIG. 1 shows a schematic configuration of an image forming apparatus 10 according to an embodiment of the present invention. The image forming apparatus 10 is an electrophotographic image forming apparatus such as a copying machine, a printer, a facsimile machine, or a multifunction machine having a combination of these functions. Currently, various types of electrophotographic image forming apparatuses have been proposed. The illustrated image forming apparatus is a so-called tandem color image forming apparatus. However, the present invention is not applied only to this type of image forming apparatus. For example, a so-called four-cycle color image forming apparatus or a toner image on an electrostatic latent image carrier is directly applied to a recording medium. The present invention is equally applicable to a direct transfer type color image forming apparatus for transferring. Furthermore, the present invention can be applied to a monochrome image forming apparatus having only one developing device.

  As shown in the figure, the image forming apparatus 10 has an endless intermediate transfer belt (corresponding to an image carrier in claims) 12 at the center. The intermediate transfer belt 12 is made of a material excellent in transfer performance, and specifically, for example, polyimide. The transfer belt 12 is supported by, for example, three rollers 14, 16, and 18. The roller 18 is drivingly connected to a motor (not shown), and the roller 18 rotates counterclockwise in the figure by driving the motor, and the intermediate transfer belt 12 and the rollers 14 and 16 in contact therewith also rotate counterclockwise. It is like that.

  Below the belt portion that moves from the roller 16 on the left side of the figure to the roller 18 on the right side of the figure, each color is in the order of yellow (Y), magenta (M), cyan (C), and black (B) from the left side. An image forming unit 20 (20Y, 20M, 20C, 20K) corresponding to the toner is disposed. Each image forming unit 20 includes a cylindrical electrostatic latent image carrier (photoconductor) 22. Around the photosensitive member 22, a charging device 24, an exposure device 26, a developing device 28, a primary transfer roller 30, and a cleaning unit 32 are arranged in this order along the rotation direction (clockwise direction in the drawing).

  The primary transfer roller 30 is disposed inside the intermediate transfer belt 12 so as to be capable of being pressed and separated from the photoreceptor 22 via the intermediate transfer belt 12. As the primary transfer roller 30, for example, an ion conductive roller is used. Since the ion conductive roller is excellent in the uniformity of electric resistance, the transfer performance can be improved and the image quality can be improved by using the ion conductive roller as the transfer roller 30. As a more specific material of the primary transfer roller 30, for example, nitrile rubber (NBR), urethane rubber, hydrin rubber, or the like is preferably used.

  On the right side of the roller 18, a secondary transfer roller (corresponding to a transfer member in claims) 34 is disposed so as to come into contact with and separate from the roller 18 via the intermediate transfer belt 12, and is in a nip portion with the belt 12. A secondary transfer region 36 is formed. As the secondary transfer roller 34, an ion conductive roller is preferably used as in the case of the primary transfer roller 30, and specific materials of the secondary transfer roller 34 include, for example, nitrile rubber (NBR), urethane rubber, or hydrin rubber. Etc. are preferably used.

  Above the secondary transfer area 36, a pair of fixing rollers (corresponding to the fixing members in claims) 50a and 50b arranged opposite to each other are arranged, and the fixing area 52 is located at the nip portion of these fixing rollers 50a and 50b. Is formed. One fixing roller 50a is drivably coupled to a fixing roller driving device (not shown) and is rotatable counterclockwise in the drawing. The other fixing roller 50b rotates following the fixing roller 50a. The rotation speed of the fixing roller 50a is controlled by a control unit 70 provided at the upper left portion of the image forming apparatus 10, and the fixing roller 50a and the control unit 70 constitute a deflection amount control unit 104 described later. The control unit 70 can be provided at an arbitrary position in the image forming apparatus 10.

  A neutralizing member 100 for neutralizing the recording sheet 46 is disposed in the vicinity of the recording sheet 46 portion extending over the secondary transfer area 36 and the fixing area 52. The neutralizing member 100 is preferably a neutralizing cloth, but is not particularly limited as long as it has a neutralizing ability. For example, a neutralizing needle, a neutralizing sheet, a neutralizing brush, or the like can be used. When using a static elimination cloth as the static elimination member 100, specific materials of the static elimination cloth include, for example, carbon fiber, stainless steel fiber, sanderlon fiber (including acrylic fiber and copper), Dyna fiber (heat resistant PVA fiber and copper). SA-7 (including acrylic fiber and carbon fiber), amorphous fiber, spatless static elimination sheet, etc. are used.

  A deflection amount detection unit 110 described later is provided in the vicinity of the neutralization member 100, and a distance control unit 102 that controls the distance between the recording sheet 46 and the neutralization member 100 from the deflection amount detection unit 110 and the deflection amount control unit 104. Is configured. The configuration of the distance control means 102 will be described in detail later.

  A sheet feeding cassette 42 is detachably disposed as a sheet feeding device below the image forming apparatus 10, and a plurality of recording sheets 46 are stacked and accommodated in the sheet feeding cassette 42. The recording sheets 46 accommodated in the paper feed cassette 42 are sent out one by one from the uppermost one to the transport path 99 by the rotation of the paper feed roller 44 disposed in the vicinity of the paper feed cassette 42. A registration roller 48 for sending the recording sheet 46 to the secondary transfer area 36 at a predetermined timing is provided in the vicinity of the paper feed roller 44.

  The conveyance path 99 extends from the paper feed cassette 42 through the nip portion of the registration roller pair 48, the secondary transfer region 36, and the fixing region 52 to the paper discharge unit 11 provided in the upper portion of the image forming apparatus 10. .

  An example of a color image forming operation will be briefly described.

  First, in each image forming unit 20, the surface of the photoreceptor 22 that is rotationally driven at a predetermined peripheral speed is charged by the charger 24. Next, light is projected from the exposure device 26 that has received the drive signal output from the control unit 70 onto the outer peripheral surface of the charged photoconductor 22 to form an electrostatic latent image. Subsequently, the electrostatic latent image is made visible by the developer toner supplied from the developing device 28. The toner images of the respective colors formed on the photoconductor 22 in this way reach the primary transfer area by the rotation of the photoconductor 22, and in this order from the photoconductor 4 to the intermediate transfer belt 12 in the order of yellow, magenta, cyan, and black. Transferred (primary transfer) and overlaid. At the time of primary transfer, a transfer bias (primary transfer bias) having a polarity opposite to the polarity of the toner is applied to the primary transfer roller 30.

  The toner image superimposed on the intermediate transfer belt 12 moves with the rotation of the intermediate transfer belt 12 and reaches the secondary transfer region 36.

  On the other hand, the recording sheet 46 accommodated in the paper feed cassette 42 is sent out to the conveyance path 99 by the rotation of the paper feed roller 44. Then, the superimposed toner images are conveyed to the secondary transfer area 36 by the registration roller 48 in accordance with the timing when the toner images reach the secondary transfer area 36.

  When the recording sheet 46 is conveyed to the secondary transfer area 36, the toner image is transferred (secondary transfer) from the intermediate transfer belt 12 to the recording sheet 46. During secondary transfer, a transfer bias (secondary transfer bias) having a polarity opposite to the polarity of the toner is applied to the secondary transfer roller 34.

  Therefore, the recording sheet 46 is charged by the secondary transfer bias when passing through the secondary transfer area 36, but is discharged from the belt 12 because it is discharged by the charge removing member 100 after passing through the secondary transfer area 36. At this time, peeling discharge is not generated.

  When the recording sheet 46 is conveyed to the fixing region 52 further downstream of the conveying path 99, the toner image is fixed on the recording sheet 46 by the fixing roller 50, and then sent to the paper discharge unit 11.

  On the other hand, the toner remaining on the intermediate transfer belt 12 after passing through the secondary transfer region 36 is removed by the cleaning member 38.

[2. Distance control means]
Hereinafter, the distance control means 102 according to the present invention will be described.

  As shown in FIG. 2, the distance control unit 102 according to the present invention includes a deflection amount detection unit 110 and a deflection amount control unit 104 so as to appropriately control the distance D between the recording sheet 46 and the charge removal member 100. It is configured. By appropriately controlling the distance D by the distance control means 102, the recording sheet 46 can be neutralized without excess or deficiency, and image defects and peeling discharge can be reliably prevented.

  In the present invention, the deflection amount detection means 110 is configured to detect that the deflection amount L1 of the recording sheet 46 portion straddling the secondary transfer region 36 and the fixing region 52 is less than a predetermined amount or more than a predetermined amount. The deflection amount control unit 104 is configured to control the deflection amount L1 to at least one of a predetermined amount or more or less than a predetermined amount based on the detection by the deflection amount detection unit 110. In the following embodiments, specific examples of the configurations of the deflection amount detection unit 110 and the deflection amount control unit 104 will be described.

  The deflection amount L1 is bent between the actual recording sheet 46 straddling the secondary transfer area 36 and the fixing area 52, and between the secondary transfer area 36 and the fixing area 52, as shown in FIG. It is assumed that the maximum value of the distance from the recording sheet portion when it is assumed that the sheet has been passed through (the state indicated by the alternate long and short dash line in FIG. 6).

[First Embodiment]
The first embodiment will be described with reference to FIGS. 2 and 3.

  The deflection amount detecting means 110 includes an actuator (corresponding to a movable member in claims) 127 and a photo sensor (corresponding to a movable member detecting device in claims) 129.

  The actuator 127 includes a contact portion 121 disposed so as to be in contact with, for example, the central portion of the recording sheet 46 extending over the secondary transfer region 36 and the fixing region 52, a shaft portion 123, and a contact portion via the shaft portion 123. 121 includes a reflecting portion (corresponding to a detected portion in claims) 125 that is continuous in an L shape. The actuator 127 is rotatable around the shaft portion 123 while maintaining the contact state with the recording sheet 46 at the contact portion 121 as the deflection amount L1 of the recording sheet 46 changes.

  When the deflection amount L1 of the recording sheet 46 is small, the actuator 127 is rotated to the left as shown by a solid line, and when the deflection amount L1 of the recording sheet 46 is large, the actuator 127 is at the right side as shown by a two-dot chain line. It will be in the state rotated to. The actuator 127 is biased by a biasing member (not shown), so that the contact state with the recording sheet 46 in the contact portion 121 is maintained.

  The photosensor 129 includes an irradiation unit that emits light in a predetermined direction, and a light reception detection unit that receives light reflected from the reflection unit 125 of the actuator 127 after being irradiated from the irradiation unit. The unit 125 is configured to detect whether or not the unit 125 exists at a predetermined position.

  In the present embodiment, the photo sensor 129 can detect whether or not the reflection portion 125 of the actuator 127 is present at a predetermined position T when the deflection amount L1 of the recording sheet 46 reaches the predetermined amount Q. Is arranged.

  By disposing the photosensor 129 in this way, the deflection amount L1 increases to the predetermined amount Q, and accordingly, the actuator 127 rotates in the clockwise direction in the figure, and the reflecting portion 125 moves to the predetermined position T. (The state shown by the two-dot chain line), the light emitted from the irradiating part of the photosensor 129 is reflected by the reflecting part 125, and the received light detecting part of the photosensor 129 detects this reflected light. Thereby, the photo sensor 129 detects that the reflecting portion 125 exists at the predetermined position T. As described above, when the photo sensor 129 detects the presence of the reflecting portion 125, the deflection amount detection unit 110 detects that the deflection amount L1 has reached the predetermined amount Q.

  On the other hand, when the deflection amount L1 decreases and becomes less than the predetermined amount Q, the actuator 127 rotates counterclockwise in the drawing, and the reflecting portion 125 moves from the predetermined position T (illustrated by a solid line). State), the light emitted from the irradiation part of the photosensor 129 is not reflected by the reflection part 125, and the light reception detection part does not detect the received light. Thereby, the photo sensor 129 detects that the reflecting portion 125 does not exist at the predetermined position T. As described above, when the photo sensor 129 detects the absence of the reflecting portion 125, the deflection amount detection unit 110 detects that the deflection amount L1 is less than the predetermined amount Q.

  As described above, the deflection amount control unit 104 includes the fixing roller 50a and the control unit 70 that controls the rotation speed of the fixing roller 50a.

  Based on the detection by the deflection amount detection unit 110, the deflection amount control unit 104 can control the deflection amount L1 to at least one of less than the predetermined amount Q or more than the predetermined amount Q.

  When the deflection amount control unit 104 controls the deflection amount L1 to be less than the predetermined amount Q, when the deflection amount detection unit 110 detects that the deflection amount L1 has reached the predetermined amount Q, the deflection amount control unit 104 By controlling the control unit 70 to increase the rotational speed of the fixing roller 50a, the deflection amount L1 is controlled to be less than the predetermined amount Q. Thereby, the distance D between the recording sheet 46 and the charge removal member 100 can be maintained to be larger than a predetermined value (for example, 3 mm), and the recording sheet 46 can be prevented from being excessively discharged.

  On the other hand, when the deflection amount control unit 104 controls the deflection amount L1 to be greater than or equal to the predetermined amount Q, when the deflection amount detection unit 110 detects that the deflection amount L1 is less than the predetermined amount Q, the deflection amount control unit. 104 controls the deflection amount L1 to be equal to or greater than the predetermined amount Q by reducing the rotation speed of the fixing roller 50a under the control of the control unit 70. Thereby, the distance D between the recording sheet 46 and the charge removal member 100 can be maintained at a predetermined value (for example, 5 mm) or less, insufficient discharge of the recording sheet 46 can be prevented, and occurrence of peeling discharge can be avoided.

[Second Embodiment]
As shown in FIG. 4, the deflection amount detection means 130 according to the second embodiment includes two photo sensors, that is, a first photo sensor 129a and a second photo sensor 129b. The configuration of each photosensor 129a, 129b is the same as that of the photosensor 129 of the first and second embodiments.

  The first photosensor 129a is arranged so that it can detect whether or not the reflecting portion 125 of the actuator 127 is present at a predetermined position T when the deflection amount L1 of the recording sheet 46 reaches a predetermined amount Q. Has been.

  On the other hand, the second photosensor 129b includes a predetermined position S where the reflecting portion 125 of the actuator 127 is disposed and a predetermined position T when the deflection amount L1 of the recording sheet 46 becomes a predetermined amount P smaller than the predetermined amount Q. It is arrange | positioned so that it can detect whether the reflection part 125 exists in any one of the position between and predetermined position T.

  By disposing the photosensors 129a and 129b in this way, the deflection amount L1 increases to the predetermined amount Q, and accordingly, the actuator 127 rotates in the clockwise direction in the drawing, and the reflecting portion 125 becomes the above-mentioned predetermined amount. When arranged at the position T (the state shown by the two-dot chain line), the presence of the reflecting portion 125 is detected by the first photosensor 129a and the second photosensor 129b. As described above, when the two photosensors 129a and 129b detect the presence of the reflection portion 125, the deflection amount detection unit 130 detects that the reflection portion 125 is disposed at the predetermined position T, and thereby the deflection amount. It is detected that L1 has reached a predetermined amount Q.

  Further, when the deflection amount L1 is larger than the predetermined amount P and smaller than the predetermined amount Q, the reflecting portion 125 is disposed between the predetermined position S and the predetermined position T (a state shown by a one-dot chain line). At this time, the presence of the reflecting portion 125 is not detected by the first photosensor 129a, and the presence of the reflecting portion 125 is detected only by the second photosensor 129b. As described above, when the presence of the reflecting portion 125 is detected only by the second photosensor 129b, the deflection amount detection unit 130 detects that the deflection amount L1 is equal to or greater than the predetermined amount P and less than the predetermined amount Q.

  Further, when the deflection amount L1 is reduced to the predetermined amount P, the actuator 127 is rotated counterclockwise in the drawing, and the reflecting portion 125 is disposed at the predetermined position S (illustrated by a solid line). In other words, the presence of the reflection portion 125 is not detected by either the first photosensor 129a or the second photosensor 129b. As described above, when neither of the photosensors 129a and 129b detects the presence of the reflecting portion 125, the deflection amount detection unit 130 detects that the deflection amount L1 is less than the predetermined amount P.

  The deflection amount control unit 104 can control the deflection amount L1 to be equal to or greater than the predetermined amount P and less than the predetermined amount Q based on the detection by the deflection amount detection unit 130.

  Specifically, when the deflection amount detection unit 130 detects that the deflection amount L1 is less than the predetermined amount P, the deflection amount control unit 104 reduces the rotation speed of the fixing roller 50a under the control of the control unit 70. Thus, the deflection amount L1 is controlled to be equal to or greater than the predetermined amount P. Thereby, the distance D between the recording sheet 46 and the charge removal member 100 can be maintained at a predetermined value (for example, 5 mm) or less, insufficient discharge of the recording sheet 46 can be prevented, and occurrence of peeling discharge can be avoided.

  When the deflection amount detection unit 130 detects that the deflection amount L1 is equal to or greater than the predetermined amount P and less than the predetermined amount Q, the deflection amount L1 is an appropriate amount, and thus control by the deflection amount control unit 104 is unnecessary. is there.

  When the deflection amount detection unit 130 detects that the deflection amount L1 has reached the predetermined amount Q, the deflection amount control unit 104 increases the rotation speed of the fixing roller 50a under the control of the control unit 70, whereby the deflection amount. L1 is controlled to be less than the predetermined amount Q. Thereby, the distance D between the recording sheet 46 and the charge removal member 100 can be maintained to be larger than a predetermined value (for example, 3 mm), and the recording sheet 46 can be prevented from being excessively discharged.

  In addition to the two photosensors 129a and 129b, a further photosensor may be arranged to control the deflection amount L1 more precisely.

[Third Embodiment]
As shown in FIG. 5, in the deflection amount detection unit 140 according to the third embodiment, the actuator 128 includes two reflecting portions, that is, a first reflecting portion 126a and a second reflecting portion 126b.

  The two reflecting portions 126a and 126b are configured so that the photosensor 129 can determine which of the reflecting portions 126a and 126b is detected. The configuration for enabling discrimination in this way is not particularly limited, but specifically, irradiation is performed from the irradiation unit of the photosensor 129, for example, by coloring the two reflection units 126a and 126b in different colors. It is conceivable that the reflectance of the emitted light differs between the first photosensor 129a and the second photosensor 129b.

  By configuring the actuator 128 in this way, the deflection amount L1 increases to the predetermined amount Q, and accordingly, the actuator 128 rotates in the clockwise direction in the drawing, and the reflecting portions 126a and 126b become the same as those shown in FIG. ) Is detected by the photosensor 12 to detect the presence of the first reflecting portion 126a. When the presence of the first reflecting portion 126a is detected in this way, the deflection amount detection unit 140 detects that the deflection amount L1 has reached the predetermined amount Q.

  Further, when the deflection amount L1 is larger than the predetermined amount P and smaller than the predetermined amount Q, the reflecting portions 126a and 126b are arranged at the positions shown in FIG. At this time, the photosensor 129 does not detect the presence of either the first reflection unit 126a or the second reflection unit 126b. As described above, when the presence of either the first reflecting portion 126a or the second reflecting portion 126b is not detected, the deflection amount detecting means 140 determines that the deflection amount L1 is equal to or greater than the predetermined amount P and less than the predetermined amount Q. Detect.

  Further, the deflection amount L1 is reduced to a predetermined amount P, and accordingly, the actuator 128 is rotated counterclockwise in the drawing, and the reflecting portions 126a and 126b are arranged at the positions shown in FIG. At this time, the presence of the second reflecting portion 126b is detected by the photosensor 129. As described above, when the presence of the second reflecting portion 126b is detected, the deflection amount detection unit 140 detects that the deflection amount L1 is less than the predetermined amount P.

  Based on the detection by the deflection amount detection means 140, the deflection amount control means 104 can control the deflection amount L1 to be not less than the predetermined amount P and less than the predetermined amount Q.

  Specifically, when the deflection amount detection unit 140 detects that the deflection amount L1 is less than the predetermined amount P, the deflection amount control unit 104 reduces the rotation speed of the fixing roller 50a under the control of the control unit 70. Thus, the deflection amount L1 is controlled to be equal to or greater than the predetermined amount P. Thereby, the distance D between the recording sheet 46 and the charge removal member 100 can be maintained at a predetermined value (for example, 5 mm) or less, insufficient discharge of the recording sheet 46 can be prevented, and occurrence of peeling discharge can be avoided.

  When the deflection amount detection unit 130 detects that the deflection amount L1 is equal to or greater than the predetermined amount P and less than the predetermined amount Q, the deflection amount L1 is an appropriate amount, and thus control by the deflection amount control unit 104 is unnecessary. is there.

  When the deflection amount detection unit 130 detects that the deflection amount L1 has reached the predetermined amount Q, the deflection amount control unit 104 increases the rotation speed of the fixing roller 50a under the control of the control unit 70, whereby the deflection amount. L1 is controlled to be less than the predetermined amount Q. Thereby, the distance D between the recording sheet 46 and the charge removal member 100 can be maintained to be larger than a predetermined value (for example, 3 mm), and the recording sheet 46 can be prevented from being excessively discharged.

  In addition to the two reflection portions 126a and 126b, the actuator 128 may be provided with another reflection portion to control the deflection amount L1 more precisely.

  While the present invention has been described with reference to the above-described embodiments, the present invention is not limited to the above-described embodiments.

  For example, since the electrical resistance of the recording sheet changes depending on the temperature and humidity environment, the static elimination performance of the static elimination member changes accordingly. Further, the electric resistance of the static elimination member also changes due to durability, and the static elimination performance of the static elimination member also changes accordingly. When the charge removal performance of the charge removal member changes, the appropriate range of the distance D between the recording sheet and the charge removal member changes. Therefore, the deflection amount L1 of the recording sheet 46 is controlled based on at least one of the information on the temperature and humidity environment in the apparatus, the information on the electrical resistance of the static eliminator, and the information on the total usage time or the number of printed sheets of the image forming apparatus. The range may be changeable. Thereby, the control range of the distance D between the recording sheet and the charge removal member can be appropriately changed corresponding to the electrical resistance of the recording sheet or the charge removal member, and the charge removal amount of the recording sheet after transfer can be more appropriately controlled. .

  Further, in the above-described embodiment, the configuration in which the distance D between the recording sheet and the static elimination member is controlled only by controlling the deflection amount L1 of the recording sheet 46, but in the present invention, the static elimination member is provided to be movable, It is also possible to control the distance D between the recording sheet and the charge removal member by controlling the arrangement of the charge removal member together with the control of the deflection amount L1.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to the present invention. The figure which shows the distance control means which concerns on this invention. The perspective view which shows the deflection amount detection means which concerns on 1st Embodiment. The side view which shows the deflection amount detection means which concerns on 2nd Embodiment. The side view which shows the deflection amount detection means which concerns on 3rd Embodiment. The figure for demonstrating the amount of deflections.

Explanation of symbols

10: Image forming device, 12: Intermediate transfer belt, 18: Roller, 22: Photoconductor, 24: Charger, 26: Exposure device, 28: Developing device, 30: Primary transfer roller, 32: Cleaning unit, 36: Two Next transfer area, 42: paper feeding section, 46: recording sheet, 50a: fixing roller, 50b: fixing roller, 52: fixing area, 99: transport path, 100: static elimination member, 102: distance control means, 104: deflection amount Control means, 110: Deflection amount detection means, 121: Contact part, 123: Shaft part: 125: Reflection part, 126a: First reflection part, 126b: Second reflection part, 127: Actuator, 128: Actuator, 130 : Deflection amount detection means, 140: Deflection amount detection means.

Claims (6)

An image carrier for carrying a toner image;
A transfer member disposed opposite to the image carrier and forming a transfer region for transferring a toner image to a recording sheet at a nip portion with the image carrier;
A pair of fixing members provided on the downstream side of the transfer region in the recording sheet conveyance direction and arranged to face each other;
A neutralizing member disposed near a portion of the recording sheet straddling the fixing region formed in the nip portion of the pair of fixing members and the transfer region, and neutralizing the recording sheet;
A distance control means for controlling the distance between the recording sheet and the charge eliminating member;
The distance control means includes
A deflection amount detecting means for detecting that the deflection amount of the portion of the recording sheet straddling the transfer region and the fixing region is less than a predetermined amount or more than a predetermined amount;
An image forming apparatus comprising: a deflection amount control unit configured to control the deflection amount to at least one of the predetermined amount or more or less than the predetermined amount based on detection by the deflection amount detection unit. The deflection amount detecting means is
A movable member disposed so as to be in contact with the recording sheet portion straddling the transfer area and the fixing area, and movable while maintaining a contact state with the recording sheet in accordance with a change in the deflection amount; ,
A movable member detecting device for detecting whether or not the detected portion is present at a predetermined position where the detected portion included in the movable member is disposed when the deflection amount is a predetermined amount; The image forming apparatus according to claim 1.   The movable member detection device includes an irradiation unit that irradiates light in a predetermined direction and a light reception detection unit that detects reception of the light, and the light that is irradiated from the irradiation unit and reflected by the detection unit. 3. The image forming apparatus according to claim 2, wherein the light receiving detection unit detects that the detected unit is present at the predetermined position. 4. At least one of the fixing members is a fixing roller that can rotate in a predetermined direction,
The image forming apparatus according to claim 1, wherein the deflection amount control unit includes the fixing roller and a control unit that controls a rotation speed of the fixing roller. An image carrier for carrying a toner image;
A transfer member disposed opposite to the image carrier and forming a transfer region for transferring a toner image to a recording sheet at a nip portion with the image carrier;
A pair of fixing members provided on the downstream side of the transfer region in the recording sheet conveyance direction and arranged to face each other;
An image forming apparatus comprising: a fixing region formed at a nip portion of the pair of fixing members; and a neutralizing member disposed near a portion of the recording sheet straddling the transfer region and neutralizing the recording sheet. A method of forming an image,
Detecting that the amount of deflection of the portion of the recording sheet straddling the transfer area and the fixing area is less than a predetermined amount or more than a predetermined amount;
Based on the detection, by controlling the deflection amount to at least one of the predetermined amount or more or less than the predetermined amount,
An image forming method comprising controlling a distance between the recording sheet and the charge eliminating member. A fixing roller that can rotate in a predetermined direction is used as at least one of the fixing members,
6. The image forming method according to claim 5, wherein the deflection amount is controlled by controlling a rotation speed of the fixing roller.

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