JP5492541B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copier, a printer, a facsimile, or a complex machine of these.

  Conventionally, as an apparatus for printing (forming) an image on a sheet as a transfer material, an image forming apparatus such as a copier, a printer, or a complex machine of these is known. Generally, in an image forming apparatus, a pair of registration rollers is provided on the upstream side in the sheet transport direction in an image forming unit that forms an image on a sheet. The registration roller pair is a pair of rollers for correcting skew of the paper (oblique feeding) and adjusting timing with the toner image before sending the paper to the image forming unit.

In a stopped state, the registration roller pair temporarily contacts the leading end of the sheet to bend the sheet, and then rotates to send the sheet to the image forming unit.
Specifically, the sheet that is in contact with the stopped registration roller pair is sent out to the registration roller pair side by a conveyance roller disposed on the upstream side of the registration roller pair in the sheet conveyance direction. As a result, the sheet is curved in a state in which the leading end is pressed toward the registration nip formed in the registration roller pair. Here, a reaction force is generated on the sheet in contact with the registration roller pair in a direction opposite to the sheet conveyance direction. Due to the reaction force of the paper, a force is generated on the paper to press the front end portion toward the registration nip. The registration roller pair performs paper skew (oblique feeding) correction before the paper is sent to the image forming unit by pressing the front end of the paper toward the registration nip.

  In the skew (diagonal feeding) correction using the registration roller pair, if the force with which the leading edge of the paper is pressed against the registration roller pair is weak, the paper skew (oblique feeding) correction may not be suitably performed. is there. In addition, when the force with which the leading edge of the paper is pressed against the registration roller pair is strong, the paper enters the registration nip, and thus the paper skew (oblique paper feeding) correction may not be suitably performed.

  Incidentally, the force with which the leading edge of the paper is pressed against the registration roller pair is caused by the size and shape of the curve formed on the paper. Further, the size and shape of the curve formed on the paper are adjusted by the amount of paper fed by the transport roller.

  As a technique for adjusting the paper feed amount, an image forming apparatus that includes a guide member that guides the paper to the registration nip and adjusts the paper feed amount by the conveyance roller according to the thickness and rigidity (stretch strength) of the paper. Has been proposed (see, for example, Patent Document 1).

In the image forming apparatus described in Patent Document 1, the guide member abuts on the sheet so as to press down the curved convex side of the curved sheet, and guides the sheet to the registration nip.
In the image forming apparatus described in Patent Document 1, the guide member is provided with a sheet in order to ensure a space in which the curved shape is formed when the curved shape formed on the paper comes into contact with and is applied with a predetermined force. It swings so as to be expanded in the direction in which the curved shape formed becomes larger. Thereby, the image forming apparatus described in Patent Document 1 secures a space in which a curved shape is formed on the sheet.

Japanese Patent Laid-Open No. 7-172639

  However, the image forming apparatus described in Patent Document 1 swings so that the guide member is pushed and spread in a direction in which the curved shape formed on the paper increases, thereby creating a space where the curved shape is formed on the paper. It is configured to ensure. For this reason, in the image forming apparatus described in Patent Document 1, no further contrivance has been made regarding the force with which the leading edge of the sheet is pressed against the pair of registration rollers.

  The present invention suitably performs paper skew (oblique paper feeding) correction in an image forming apparatus including a registration roller pair that feeds paper to an image forming unit and a guide member that guides the paper to a registration nip of the registration roller pair. An object of the present invention is to provide an image forming apparatus that can perform the above-described process.

  The present invention relates to an image forming unit that forms an image on a sheet-like transfer material and a registration roller pair that forms a registration nip, and in a stopped state, the tip of the transfer material is once applied to the registration roller pair. After the contacted material is bent and curved, the registration roller pair that rotationally drives the transfer material to the image forming unit and the upstream of the registration roller pair in the conveyance direction of the transfer material A conveying roller capable of conveying the transferred material in the conveying direction and stopping the transferred material by holding the transferred material in contact with a pair of registration rollers while holding the transferred material; and the resist The transfer material that is disposed between the roller pair and the transport roller and has a guide surface that contacts the curved transfer material so as to press the convex side of the curved shape, and that contacts the guide surface Before A guide member that guides to a registration nip, a guide angle changing unit that changes a guide angle that is an angle of the guide surface with respect to a registration nip plane including the registration nip when viewed from the axial direction of the registration roller pair, and the registration A guide angle that controls the guide angle changing unit so as to change the guide angle after the material to be transferred comes into contact with the guide surface so that the convex side of the curved shape can be pressed down when the roller pair is stopped. And an image forming apparatus including a change control unit.

  Further, the guide member is formed in a planar shape that approaches the registration nip side as the guide surface moves from the upstream side to the downstream side in the transport direction, and on the downstream side of the guide member in the transport direction. The guide roller is supported so as to be rotatable about a first rotation axis parallel to the axial direction of the registration roller pair, and the guide angle changing unit rotates the guide member about the first rotation axis to thereby guide the guide. It is preferable to change the angle.

  In addition, the guide angle change control unit may be configured such that the material to be transferred has a curved convex shape based on type information including thickness information on the thickness of the material to be transferred and / or stiffness information on the rigidity of the material to be transferred. When abutting against the guide surface so that the side can be pressed, the guide angle changing unit is controlled so that the guide angle is the first guide angle, and the transferred material is pressed against the convex side of the curved shape. Thus, it is preferable to control the guide angle changing unit so that the guide angle becomes a second guide angle smaller than the first guide angle after contacting the guide surface.

  According to the present invention, in an image forming apparatus including a registration roller pair that feeds paper to an image forming unit and a guide member that guides the paper to a registration nip of the registration roller pair, correction of paper skew (oblique feeding) is preferable. An image forming apparatus that can be used in the present invention can be provided.

FIG. 3 is a diagram for explaining an arrangement of each component in the copier 1 of the present embodiment. FIG. 6 is a side view showing a detailed configuration of a registration mechanism unit RK including a registration roller pair 80 in the copier 1 of the present embodiment, and is a view when a guide angle is a first guide angle α1. FIG. 7 is a side view showing a detailed configuration of a registration mechanism unit RK including a registration roller pair 80 in the copying machine 1 of the present embodiment, and is a view when a guide angle is a second guide angle α2. FIG. 5 is a perspective view illustrating the configuration of a registration guide member 130 and a guide angle changing unit 140 that are components of the registration mechanism unit RK in the copier 1 of the present embodiment. 6 is a flowchart showing an operation flow of skew correction by a registration mechanism unit RK in the copier 1 of the present embodiment. It is a perspective view which shows the structure of the resist guide member 130 and the guide angle change part 140 which are the components of the registration mechanism part RK in other embodiment.

Hereinafter, embodiments of an image forming apparatus of the present invention will be described with reference to the drawings.
With reference to FIG. 1, the overall structure of a copier 1 as an image forming apparatus in the embodiment will be described. FIG. 1 is a diagram for explaining the arrangement of each component in the copier 1 of this embodiment.

  As shown in FIG. 1, a copier 1 as an image forming apparatus is disposed on an upper side in the vertical direction Z of the copier 1 and on a lower side of the copier 1 in the vertical direction Z. An apparatus main body M that forms a toner image on a sheet T as a sheet-like transfer material based on image information read by the image reading apparatus 300.

  In the description of the copying machine 1, the rotation axis direction of various rotating bodies (rollers, belts, etc.) in the photosensitive drum 2, the fixing unit 9, etc. is referred to as “Y direction” (direction passing through FIG. 1). The Y direction is also a direction orthogonal to the transport direction D1 of the paper T as a transfer material (see FIGS. 2A to 3). In the Y direction, the front side in FIG. 1 is also referred to as “+ (plus) side”, and the rear side in FIG. 1 is also referred to as “− (minus) side”. The direction that is horizontal and orthogonal to the Y direction is referred to as the “X direction”. The vertical direction Z of the copier 1 is orthogonal to the X direction and the Y direction. A direction perpendicular to the transport direction D1 of the paper T and perpendicular to the Y direction is referred to as a “second direction D2” (see FIGS. 2A to 3). In the second direction D2, a registration guide member 130 side described later is also referred to as a “+ (plus) side”, and a conveyance guide member 120 side described later is also referred to as a “− (minus) side” (see FIGS. 2A to 3).

First, the image reading apparatus 300 will be described.
As shown in FIG. 1, the image reading apparatus 300 includes a lid member 70 and a reading unit 301 that reads an image of a document G.
The lid member 70 is connected to the reading unit 301 so as to be opened and closed by a connecting unit (not shown). The lid member 70 has a function of protecting a reading surface 302A described later.

Next, the apparatus main body M will be described.
The apparatus body M includes an image forming unit GK that forms a predetermined toner image on the paper T based on predetermined image information, and a fixing unit that fixes the toner image formed on the paper T in the image forming unit GK to the paper T. 9 and a paper supply / discharge unit KH that supplies the paper T to the image forming unit GK and discharges the paper T on which the toner image is formed.

As shown in FIG. 1, the image forming unit GK includes a photosensitive drum 2, a charging unit 10, a laser scanner unit 4 as an exposure device, a developing device 16, a toner cartridge 5, a toner supply device 6, A drum cleaning device 11 and a transfer roller 8 are provided.
The paper supply / discharge unit includes a paper feed cassette 52, a registration roller pair 80, a transport path L for paper T, a paper discharge unit 50, and a manual paper feed unit 64.

  The photosensitive drum 2 is made of a cylindrical member and functions as a photosensitive member or an image carrier. The photosensitive drum 2 is disposed so as to be rotatable in the direction of an arrow about an axis extending in a direction orthogonal to the conveyance direction of the paper T in the conveyance path L. An electrostatic latent image can be formed on the surface of the photosensitive drum 2.

  The charging unit 10 is disposed to face the surface of the photosensitive drum 2. The charging unit 10 uniformly charges the surface of the photosensitive drum 2 to be negative (minus polarity) or positive (plus polarity).

  The laser scanner unit 4 functions as an exposure unit, and is disposed away from the surface of the photosensitive drum 2. The laser scanner unit 4 includes a laser light source (not shown), a polygon mirror, a polygon mirror driving motor, and the like.

  The laser scanner unit 4 scans and exposes the surface of the photosensitive drum 2 based on image information input from a CCD substrate (not shown). By scanning exposure with the laser scanner unit 4, the charge on the exposed portion of the surface of the photosensitive drum 2 is removed. As a result, an electrostatic latent image is formed on the surface of the photosensitive drum 2.

  The developing device 16 is provided corresponding to the photosensitive drum 2 and is disposed to face the surface of the photosensitive drum 2. The developing device 16 attaches a single color (usually black) toner to the electrostatic latent image formed on the photoconductive drum 2 to form a single color toner image on the surface of the photoconductive drum 2. The developing device 16 includes a developing roller 17 disposed opposite to the surface of the photosensitive drum 2, a stirring roller 18 for stirring the toner, and the like.

  The toner cartridge 5 is provided corresponding to the developing device 16 and stores toner supplied to the developing device 16.

  The toner supply device 6 is provided corresponding to the toner cartridge 5 and the developing device 16, and supplies the toner stored in the toner cartridge 5 to the developing device 16. The toner supply device 6 and the developing device 16 are connected by a toner supply path (not shown).

  The transfer roller 8 transfers the toner image developed on the surface of the photosensitive drum 2 to the paper T. A transfer bias for transferring the toner image formed on the photosensitive drum 2 to the paper T is applied to the transfer roller 8 by a transfer bias applying unit (not shown). The transfer roller 8 is configured to be rotatable while being in contact with the photosensitive drum 2.

  A sheet T conveyed on the conveyance path L is sandwiched between the photosensitive drum 2 and the transfer roller 8. The sandwiched paper T is pressed against the surface of the photosensitive drum 2. A transfer nip N is formed between the photosensitive drum 2 and the transfer roller 8. In the transfer nip N, the toner image developed on the photosensitive drum 2 is transferred onto the paper T.

  The drum cleaning device 11 is disposed to face the surface of the photosensitive drum 2. The drum cleaning device 11 removes toner and deposits remaining on the surface of the photosensitive drum 2 and conveys the removed toner and the like to a predetermined collection mechanism for collection.

  The fixing unit 9 melts and presses the toner constituting the toner image transferred to the paper T and fixes the toner on the paper T. The fixing unit 9 includes a heating rotator 9a heated by a heater and a pressure rotator 9b pressed against the heating rotator 9a. The heating rotator 9a and the pressure rotator 9b sandwich and pressurize the paper T on which the toner image has been transferred, and convey the paper T. By transporting the paper T while being sandwiched between the heating rotator 9a and the pressure rotator 9b, the toner transferred onto the paper T is melted and pressurized, and is fixed to the paper T.

Next, the paper supply / discharge unit KH will be described.
As shown in FIG. 1, the paper supply / discharge unit KH includes a cassette paper supply unit 51, a paper supply cassette 52, a manual paper supply unit 64, a transport path L of paper T, a registration roller pair 80, and paper discharge. Part 50. As will be described later, the transport path L includes the first transport path L1, the second transport path L2, the third transport path L3, the fourth transport path L4, the fifth transport path L5, and the sixth transport. This is an assembly of the path L6 and the return transport path LB.

  As shown in FIG. 1, in the lower part of the apparatus main body M, two paper feed cassettes 52 that store paper T are arranged in the left and right (X direction). The paper feed cassette 52 is configured to be drawable in the horizontal direction from the front side (the front side in FIG. 1) of the apparatus main body M. The paper feed cassette 52 includes a placement plate 60 on which the paper T is placed, and is accommodated in a state where the paper T is stacked on the placement plate 60. When an image is formed on the paper T, the paper T placed on the placement plate 60 is placed at the paper feed side end of the paper feed cassette 52 (right end in FIG. 1). 51 is sent out to the conveyance path L. The cassette paper feed unit 51 includes a forward feed roller 61 for taking out the paper T on the placement plate 60 and a paper feed roller pair 63 for feeding the paper T one by one to the first transport path L1 of the transport path L. A double feed prevention mechanism.

  A manual paper feed unit 64 is provided on the right side of the apparatus main body M (on the right side in FIG. 1) and above the paper feed cassette 52. The manual paper feed unit 64 is provided mainly for supplying the apparatus main body M with a paper T of a size and type different from the paper T set in the paper feed cassette 52. The manual paper feed unit 64 includes a manual feed tray 65 that forms a part of the front surface of the apparatus main body M in the closed state, and a paper feed roller 66. The lower end of the manual feed tray 65 is attached to the vicinity of the paper feed roller 66 so as to be rotatable (openable and closable). The paper T is placed on the open manual feed tray 65. The paper feed roller 66 feeds the paper T placed on the open manual feed tray 65 to the first transport path L1.

The conveyance path L includes a first conveyance path L1 from the cassette paper feeding unit 51 to the registration roller pair 80, a second conveyance path L2 from the registration roller pair 80 to the transfer roller 8, and a transfer roller 8 to the fixing unit 9. The third transport path L3, the fourth transport path L4 from the fixing unit 9 to the first branching section Q1, the fifth transport path L5 from the first branching section Q1 to the paper discharge section 50, and the fourth transport path L4 A return transport path LB for transporting the paper T transported from the upstream side to the downstream side from the first branching portion Q1 to the second joining portion P2, and a sixth transport for transporting the paper T reversed upside down to the paper discharge portion 50. And a road L6.
Details of the registration mechanism RK including the registration roller pair 80 will be described later.

  A first junction P1, a second junction P2, and a third junction P3 are disposed in the first transport path L1. The first joining portion P1 is a joining portion from the cassette paper feeding portion 51 of the two paper feeding cassettes 52 to the first transport path L1. The second junction P2 is a junction from the return conveyance path LB to the first conveyance path L1. The third merging portion P3 is a merging portion from the manual sheet feeding portion 64 to the first transport path L1.

  The return conveyance path LB includes a bent conveyance path La that conveys the sheet T branched at the first branching portion Q1 while being bent obliquely downward, and a sheet T that is turned upside down by the bending conveyance through the second branching portion Q2. After that, the horizontal receiving portion Lb received in a horizontal posture, and the paper T that is once received by the horizontal receiving portion Lb and then fed in the reverse direction are branched at the third branching portion Q3, and again are reversed upside down. And a horizontal return transport path Lc for transporting toward the second junction P2. A roller pair 28 that forcibly conveys the paper T that is turned upside down to the horizontal return conveyance path Lc or the sixth conveyance path L6 through the third branching section Q3 is provided at the delivery end of the horizontal receiving section Lb. Yes. Further, the first branch part Q1, the second branch part Q2, and the third branch part Q3 are provided with transport path switching members 30, 31, and 32, respectively.

  When the double-sided printing of the paper T is performed, the return transport path LB reverses the front and back and the front and back of the paper T after being fixed by the fixing unit 9, thereby reversing the surface that has been printed (non-printing). This is a transport path for transporting so that the surface) faces the photosensitive drum 2. Further, the sixth transport path L6 passes through the bent transport path La in the return transport path LB, and is discharged in a state where the paper T once received by the horizontal receiving portion Lb is turned upside down (in a state where the printing surface is down). This is a conveyance path for carrying out to the paper unit 50.

  A paper discharge unit 50 is provided above the left side (left side in FIG. 1) of the apparatus main body M. The paper discharge unit 50 opens toward the left side of the apparatus main body M. The paper discharge unit 50 discharges the paper T transported through the fifth transport path L5 or the paper T transported through the sixth transport path L6 onto a paper discharge tray 54 outside the apparatus main body M by the roller pair 53.

  Hereinafter, a configuration related to the registration mechanism unit RK, which is a characteristic part of the copier 1 of the present embodiment, will be described with reference to the drawings. FIG. 2A is a side view showing a detailed configuration of the registration mechanism unit RK including the registration roller pair 80 in the copier 1 of the present embodiment, and is a view when the guide angle is the first guide angle α1. FIG. 2B is a side view showing a detailed configuration of the registration mechanism unit RK including the registration roller pair 80 in the copier 1 of the present embodiment, and is a view when the guide angle is the second guide angle α2. FIG. 3 is a perspective view showing configurations of the registration guide member 130 and the guide angle changing unit 140 which are components of the registration mechanism unit RK in the copying machine 1 of the present embodiment.

  As shown in FIGS. 2A and 2B, the registration mechanism portion RK of the present embodiment includes a registration roller pair 80, a first conveyance roller pair 90 as a conveyance roller, a conveyance guide member 120, and a registration guide as a guide member. A member 130, a pre-registration sensor S, and a guide angle changing unit 140 are provided.

The registration roller pair 80 is disposed on the upstream side in the transport direction D1 of the paper T in the transfer nip N of the image forming unit GK (see FIG. 1).
The registration roller pair 80 is composed of two roller members facing each other. The two roller members in the registration roller pair 80 are configured to be rotatable around a rotation axis parallel to the Y direction. A motor (not shown) is connected to the registration roller pair 80. The registration roller pair 80 rotates or stops by driving a motor.

A registration nip RN is formed between the two roller members in the registration roller pair 80. The paper T conveyed on the first conveyance path L1 is conveyed toward the registration nip RN.
The leading end T1 of the paper T that is transported through the first transport path L1 contacts the registration roller pair 80 that is stopped. The sheet in contact with the registration roller pair 80 is sent out in the conveyance direction D1 by a first conveyance roller pair 90 described later, and in the second direction on the upstream side of the conveyance direction D1 of the registration nip RN in the first conveyance path L1. Curved convexly on the plus side in D2.
In this way, when the registration roller pair 80 is in the stopped state, the registration roller pair 80 bends the paper T by once contacting the leading end T1 of the paper T conveyed on the first conveyance path L1. .

  After the leading end T1 of the paper T once comes into contact with the registration roller pair 80, the registration roller pair 80 is driven to rotate. Thereby, the paper T is introduced into the registration nip RN. The paper T introduced into the registration nip RN is sent out to the second conveyance path L2 by the registration roller pair 80 while being sandwiched between two roller members in the registration roller pair 80. As described above, the registration roller pair 80 sends the paper T toward the transfer nip N in the image forming unit GK.

  As shown in FIGS. 2A and 2B, the first transport roller pair 90 is disposed on the upstream side in the transport direction D1 of the paper T in the registration roller pair 80. Specifically, the first conveyance roller pair 90 is a conveyance roller pair that is positioned closest to the registration roller pair 80 among a plurality of conveyance roller pairs that convey the paper T toward the image forming unit GK.

  The first transport roller pair 90 is composed of two roller members facing each other. The two roller members in the first conveying roller pair 90 are configured to be rotatable around a rotation axis parallel to the rotation axis direction of the registration roller pair 80. A conveyance roller driving unit 910 configured by a motor or the like is connected to the first conveyance roller pair 90. The first conveyance roller pair 90 rotates or stops by driving the conveyance roller driving unit 910. As a result, the first transport roller pair 90 feeds the paper T toward the registration roller pair 80 in a state where the paper T is sandwiched between the two roller members.

The first transport roller pair 90 transports the paper T in the transport direction D1, and brings the leading end T1 of the paper T into contact with the registration roller pair 80 in a state where the paper T is sandwiched. The first transport roller pair 90 feeds the paper T in a state where the paper T is sandwiched by driving of the transport roller driving unit 910, and causes the leading end T 1 of the paper T to contact the registration roller pair 80. The first conveying roller pair 90 bends the paper T by feeding the paper T in contact with the registration roller pair 80 further to the registration roller pair 80 side. The first transport roller pair 90 sends out the paper T, whose tip T1 is in contact with the registration roller pair 80, so as to bend in a convex shape in the second direction D2.
The first conveying roller pair 90 stops rotating after the paper T is sent out for a predetermined length.

The delivery length of the paper T in the first conveying roller pair 90 is set for each apparatus according to various design conditions. In the present embodiment, the first transport roller pair 90 is based on a passage signal of the paper T output by a pre-registration sensor S (described later) disposed on the upstream side of the registration roller pair 80 in the transport direction D1 of the paper T. Then, it is driven to rotate for a predetermined time by the transport roller driving unit 910. Thereby, the paper T is sent out for a predetermined length in the transport direction D1. Further, the first transport path L1 is convexly curved toward the plus side in the second direction D2. As a result, the paper T is curved in a convex shape on the plus side in the second direction D2.
As described above, the first conveying roller pair 90 presses the leading end T1 of the paper T against the registration roller pair 80, thereby correcting the skew (oblique feeding) of the paper T before sending the paper T to the image forming unit GK. Is going.

  As shown in FIGS. 2A and 2B, the conveyance guide member 120 and the registration guide member 130 are arranged so that the distance between them becomes narrower as it approaches the position immediately before the registration roller pair 80 in the first conveyance path L1. As a result, the paper T sent out from the first conveyance roller pair 90 is guided by the conveyance guide member 120 and the registration guide member 130 and conveyed toward the registration nip RN.

The conveyance guide member 120 is a planar plate member. The conveyance guide member 120 is disposed on one surface side (minus side in the second direction D2) of the sheet T to be conveyed between the first conveyance roller pair 90 and the registration roller pair 80.
The conveyance guide member 120 is directed toward the registration roller pair 80 while guiding the sheet T fed from the first conveyance roller pair 90 on one surface side (the surface opposite to the printing surface) of the sheet T being conveyed. Transport.

  The resist guide member 130 is a planar plate member. The registration guide member 130 is arranged between the registration roller pair 80 and the first conveyance roller pair 90 and is arranged on the other surface side (printing surface side) of the conveyed paper T. The registration guide member 130 is positioned in the vicinity of the registration nip RN at the downstream end in the transport direction D1, and approaches the transport guide member 120 toward the downstream end in the transport direction D1 (second direction D2). (Minus side).

  Specifically, the resist guide member 130 has a resist guide surface 130a as a guide surface that comes into contact with the curved paper T so as to press the convex side of the curved shape. The resist guide surface 130a is formed in a planar shape that approaches the resist nip RN side from the upstream side to the downstream side in the transport direction D1.

  When viewed from the axial direction of the registration roller pair 80, the registration guide member 130 is disposed with a guide angle α (an angle of the registration guide surface 130 a with respect to the registration nip plane 810) with respect to the registration nip plane 810. The resist nip plane 810 is a virtual plane formed including the resist nip RN. Specifically, the registration nip plane 810 is a plane including the tangent lines of the two roller members of the registration roller pair 80 in the registration nip RN.

  The resist guide member 130 is configured such that the guide angle α can be changed by a guide angle changing unit 140 described later. The resist guide member 130 is configured such that the guide angle α can be changed by the guide angle changing unit 140 within a range of 20 ° to 30 °, for example.

  The registration guide member 130 abuts against the paper T curved in a convex shape when the leading end T1 of the paper T abuts against the registration roller pair 80 so that the registration guide surface 130a presses the convex side of the curved shape. The paper T is guided to the registration nip RN.

  The pre-registration sensor S is disposed along the first conveyance path L1 between the registration roller pair 80 and the first conveyance roller pair 90. The pre-registration sensor S detects that the paper T has passed and outputs a detection signal to the control unit 200.

As shown in FIGS. 2A to 3, the guide angle changing unit 140 includes a support shaft 141 and a guide angle changing drive unit 147.
The support shaft 141 is a member coaxial with the first rotation axis J1 extending in parallel to the rotation axis direction of the registration roller pair 80. The support shaft 141 is disposed along the Y direction, and is fixed to an end portion of the registration guide member 130 on the downstream side in the transport direction D1.

  The support shaft 141 is configured to be rotatable about the first rotation axis J1. The guide angle changing unit 140 rotates the support shaft 141 to rotate the registration guide member 130 fixed to the support shaft 141 around the first rotation axis J1, thereby changing the guide angle α.

  As shown in FIG. 3, the negative end of the support shaft 141 in the Y direction is supported via a bearing (not shown) in the apparatus body M or the like so as to be able to rotate (turn). A first gear 142 is fixed to the positive end of the support shaft 141 in the Y direction. The first gear 142 meshes with the second gear 143 that is fixed to the output shaft 148 of the guide angle change drive unit 147. The output shaft 148 of the guide angle change drive unit 147 is driven to rotate about an axis parallel to the first rotation axis J1.

The guide angle change drive unit 147 drives the support shaft 141 via the first gear 142 and the second gear 143 by driving the output shaft 148 to rotate. As a result, the guide angle change drive unit 147 rotates (rotates) the registration guide member 130 about the first rotation axis J1.
The guide angle change drive unit 147 is constituted by, for example, a stepping motor.

  The guide angle changing unit 140 rotates and drives the output shaft 148 of the guide angle changing drive unit 147 to rotate the support shaft 141, whereby the guide angle α (the registration nip plane when viewed from the axial direction of the registration roller pair 80). The angle of the resist guide surface 130a with respect to 810 is changed. Specifically, the guide angle changing unit 140 can change the guide angle α to be in the range of 20 ° to 30 °, for example.

Next, a configuration related to the control of the copy machine 1 will be described.
As shown in FIGS. 2A to 3, the copier 1 includes a control unit 200 and a storage unit 250. The control unit 200 includes a guide angle change control unit 210 and a conveyance roller drive control unit 220.
The guide angle change control unit 210 changes the guide angle α based on the type information of the paper T including the thickness information about the thickness of the paper T and the rigidity information about the rigidity of the paper T. To control.

  The guide angle change control unit 210 converts the sheet T type information including the thickness information about the thickness of the sheet T selected by the sheet type selection button (not shown) of the copier 1 and the rigidity information about the rigidity of the sheet T. Based on the information stored in the storage unit 250 to be described later, the operation amount (angle change amount) of the guide angle changing unit 140 is determined, and the determined operation amount is output to the guide angle changing unit 140.

  The guide angle change control unit 210 guides the guide angle α to be changed after the registration roller pair 80 is stopped, after the paper T abuts the registration guide surface 130a so as to press the convex side of the curved shape. The angle changing unit 140 is controlled.

  For example, the guide angle change control unit 210 sets the guide angle α to the first guide angle α1 (see FIG. 2A) when the sheet T comes into contact with the registration guide surface 130a so as to press the curved convex side. After the guide angle changing unit 140 is controlled as described above and the sheet T comes into contact with the registration guide surface 130a so as to press the curved convex side, the guide angle α is smaller than the first guide angle α1. The guide angle changing unit 140 is controlled to have an angle α2 (see FIG. 2B).

  The transport roller drive control unit 220 is configured to stop the rotation of the first transport roller pair 90 after a predetermined time based on the information of the detection signal of the paper T detected by the pre-registration sensor S. To control. As a result, the first transport roller pair 90 feeds the paper T, the front end of which is in contact with the registration roller pair 80, to the registration roller pair 80 side by a predetermined length. As a result, the sheet T is curved in a state where the leading end T1 is in contact with the registration roller pair 80.

The storage unit 250 stores information related to the operation amount of the guide angle changing unit 140 corresponding to the paper type.
In the present embodiment, the storage unit 250 stores information regarding the operation amount of the first guide angle α1 and information regarding the operation amount of the second guide angle α2. For example, the first guide angle α1 is a guide angle larger than the second guide angle α2. In other words, the second guide angle α2 is a guide angle smaller than the first guide angle α1.

Specifically, the first guide angle α1 is a guide angle when, for example, the sheet T comes into contact with the registration guide surface 130a so that the convex side of the curved shape is pressed while the registration roller pair 80 is stopped. The second guide angle α2 is, for example, a guide angle that is changed after the sheet T comes into contact with the registration guide surface 130a so as to press the convex side of the curved shape.
Information stored in the storage unit 250 is referred to by the guide angle change control unit 210.

Incidentally, the paper T having various thicknesses is used in the copying machine 1. When the thickness of the paper T is different, the rigidity (strength of the waist) is different corresponding to the thickness of the paper T. Further, even for the paper T having the same thickness, various types (stiffness) of paper T are selectively used such that the rigidity (strength) differs depending on the material. .
Then, depending on the type (rigidity) of the paper T to be used, a difference occurs in the force (hereinafter, also referred to as “front end pressing force”) by which the front end T1 of the paper T is pressed against the registration roller pair 80. This difference is one of the factors that prevent skew correction from being performed properly.

  The registration mechanism unit RK in the present embodiment has a function of adjusting the tip pressing force that varies depending on the type (rigidity) of the paper T to be used. Specifically, the registration mechanism unit RK adjusts the tip pressing force by changing the size of the curved shape formed on the paper T using the registration guide member 130.

  In this embodiment, by rotating the registration guide member 130 about the first rotation axis J1, a guide angle α (the registration guide surface 130a relative to the registration nip plane 810 when viewed from the axial direction of the registration roller pair 80) is obtained. Change the angle. When the paper T is the same type and the guide angle α is small when the paper T is in contact with the resist guide surface 130a of the resist guide member 130 (for example, the second guide angle α2, see FIG. 2B). When the guide angle α is large (for example, the first guide angle α1, see FIG. 2A), the amount of bending of the paper T in the second direction D2 is smaller.

  Therefore, when the guide angle α when the paper T is brought into contact with the registration guide surface 130a is small, the convex shape of the curved shape of the paper T becomes small, and the guide when the paper T is brought into contact with the registration guide surface 130a. When the angle α is large, the convex shape of the curved shape of the paper T becomes large.

  As a result, the paper T abutted on the resist guide surface 130a when the guide angle α is small (the paper T on which the curved convex portion is formed small) abuts on the resist guide surface 130a when the guide angle α is large. The leading edge pressing force of the paper T is larger than that of the paper T to be printed (paper T on which the curved convex is formed larger).

  Further, the guide angle changing unit 140 changes the size of the curved shape formed on the paper T, so that the front end pressing force when the front end T1 of the paper T comes into contact with the registration roller pair 80 is changed. Adjust so that it is within the set range without being affected by the type. Specifically, the guide angle changing unit 140 responds to the difference in the type (rigidity) of the paper T to be used with respect to the registration angle with respect to the registration nip plane 810 when viewed from the axial direction of the registration roller pair 80. The angle of the guide surface 130a is changed.

  Further, the guide angle change control unit 210 determines the angle change amount of the guide angle change unit 140 with reference to information stored in the storage unit 250 based on the type information of the paper T to be used. Then, the guide angle change control unit 210 controls the guide angle change unit 140.

  Specifically, for example, the guide angle change control unit 210 makes the guide angle α larger than the second guide angle when the sheet T abuts on the registration guide surface 130a so as to press the convex side of the curved shape. The guide angle changing unit 140 is controlled so as to be the first guide angle α1.

  Therefore, the resist guide members 130 in the case of the first guide angle α1 are spaced closer to each other on the end side in the transport direction D1 than in the case where the distance between the transport guide member 120 and the resist guide member 130 is the second guide angle α2. Is arranged to be wide. Thereby, in the case of the first guide angle α1, the paper T carried in from the transport direction D1 by the first transport roller pair 90 is more easily guided to the registration guide member 130 than in the case of the second guide angle α2. The first guide angle α1 is preferably set to a suitable guide angle for guiding the paper T to the registration nip RN, for example.

  Further, the guide angle change control unit 210 sets the guide angle α to a second guide angle smaller than the first guide angle α1 after the sheet T abuts against the registration guide surface 130a so that the curved convex side is pressed. The guide angle changing unit 140 is controlled so as to be α2.

  Therefore, the leading edge pressing force of the sheet T is the first to the leading edge pressing force at the first guide angle α1 (the pressing force smaller than the second guide angle α2) in a state where the leading end of the sheet T is pressed toward the registration nip RN. It is increased to the tip pressing force at the two guide angles α2 (tip pressing force larger than the first guide angle α1).

  Thus, after correcting the skew of the paper T with the leading edge pressing force at the first guide angle α1 (pressing force smaller than the second guide angle α2), the leading edge pressing force at the second guide angle α2 (first guide angle α1). The skew correction of the paper T can be appropriately performed with a larger leading edge pressing force.

Next, with reference to FIG. 1, the operation of the copier 1 of the present embodiment will be briefly described.
First, a case where single-sided printing is performed on the paper T stored in the paper feed cassette 52 will be described.
The paper T accommodated in the paper feed cassette 52 is sent out to the first transport path L1 by the forward feed roller 61 and the paper feed roller pair 63, and then the registration rollers via the first junction P1 and the first transport path L1. Transported to pair 80.
In the registration roller pair 80, skew correction of the paper T and timing adjustment with the toner image are performed. The skew correction operation by the registration mechanism RK including the registration roller pair 80 will be described later.

The paper T discharged from the registration roller pair 80 is introduced into the transfer nip N between the photosensitive drum 2 and the transfer roller 8 via the first conveyance path L1. In the transfer nip N, the toner image developed on the photosensitive drum 2 is transferred onto the paper T.
Thereafter, the sheet T is discharged from the transfer nip N between the photosensitive drum 2 and the transfer roller 8 to the second conveyance path L2, and is added to the heating rotator 9a in the fixing unit 9 via the second conveyance path L2. It is introduced into the fixing nip with the pressure rotating body 9b. Then, in the fixing nip, the toner TN is melted and pressed, and the toner TN is fixed on the paper T.

Next, the paper T is transported to the paper discharge unit 50 through the third transport path L3, and is discharged from the paper discharge unit 50 onto the paper discharge tray 54 outside the apparatus main body M by the roller pair 53.
In this way, single-sided printing of the paper T stored in the paper feed cassette 52 is completed.

  When single-sided printing is performed on the paper T placed on the manual feed tray 65, the paper T placed on the manual feed tray 65 is sent out to the manual feed path L by the paper feed roller 66, and then the third joining portion. It is transported to the first transport path L1 via P3, and transported to the registration roller pair 80 via the first transport path L1. Subsequent operations are the same as the one-side printing operation of the paper T accommodated in the paper feed cassette 52 described above, and a description thereof will be omitted.

Next, the operation of the copier 1 when performing duplex printing will be described.
In the case of single-sided printing, as described above, the paper T on which single-sided printing has been performed is discharged from the paper discharge unit 50 to the outside of the apparatus main body M, and the printing operation is completed.
On the other hand, when performing double-sided printing, the paper T on which single-sided printing has been performed is reversed from the time of single-sided printing and conveyed again to the registration roller pair 80 via the return conveyance path LB. Then, printing is performed on the surface (non-printing surface) opposite to the surface on which the paper T has already been printed, and the double-sided printing is completed.

  Next, a specific operation of skew correction by the registration mechanism unit RK, which is a characteristic part of the copier 1 of the present embodiment, will be described with reference to FIGS. 2A to 4. FIG. 4 is a flowchart showing an operation flow of skew correction by the registration mechanism unit RK in the copier 1 of the present embodiment.

In step ST1, the type of paper T used for printing is selected by a paper type selection button (not shown) of the copier 1.
In step ST2, the guide angle change control unit 210 determines the operation amount (angle change amount) of the guide angle change unit 140 with reference to the storage unit 250 based on the type (rigidity) information of the selected paper T. To do. The guide angle change control unit 210 outputs information on the operation amount of the guide angle change unit 140 to the guide angle change unit 140.

  In step ST3, the guide angle change control unit 210 controls the guide angle change unit 140 so that the guide angle α is set to the first guide angle α1.

  Based on the operation amount information relating to the first guide angle α1 determined and output by the guide angle change control unit 210, the guide angle change drive unit 147 drives the support shaft 141 to rotate forward and backward in the guide angle change unit 140. Do. Therefore, the registration guide member 130 rotates around the first rotation axis J1. As a result, the guide angle α (the angle of the registration guide surface 130a with respect to the registration nip plane 810 when viewed from the axial direction of the registration roller pair 80) is changed (maintained) to the first guide angle α1.

In step ST <b> 4, the paper T is sent out along the transport direction D <b> 1 of the paper T by the first transport roller pair 90.
The paper T sent to the first conveyance roller pair 90 is detected by a pre-registration sensor S disposed along the first conveyance path L1 between the registration roller pair 80 and the first conveyance roller pair 90. The pre-registration sensor S outputs information on the detection signal of the paper T to the transport roller drive control unit 220. Thereafter, the paper T sent out to the first conveyance roller pair 90 is conveyed from the upstream end side in the conveyance direction D1 of the registration guide member 130 toward the registration roller pair 80.

  Here, for example, the first guide angle α1 is set to a more suitable guide angle for guiding the paper T to the registration nip RN than the second guide angle α2. Thereby, in the case of the first guide angle α1, the paper T carried in from the transport direction D1 by the first transport roller pair 90 is more easily guided to the registration guide member 130 than in the case of the second guide angle α2.

  In step ST5, the sheet T comes into contact with the registration roller pair 80 in which the leading end T1 of the sheet T is stopped. Then, a portion (curved portion) Ta following the leading end T1 of the paper T is curved in a convex shape on the plus side in the second direction D2 (see FIG. 2A).

  Then, the curved sheet T abuts on the resist guide surface 130a having the first guide angle α1. The skew correction of the paper T is performed with the leading edge pressing force at the first guide angle α1 (the pressing force smaller than the second guide angle α2 described later). The curved sheet T is guided toward the registration nip RN in a state where the convex side of the curved shape is pressed by the registration guide member 130.

  In step ST <b> 6, based on the information output from the pre-registration sensor S, the conveyance roller drive control unit 220 causes the conveyance roller driving unit 910 to stop the rotation of the first conveyance roller pair 90 after a predetermined time.

In step ST7, as shown in FIG. 2B, the guide angle change control unit 210 controls the guide angle change unit 140 to change the guide angle α from the first guide angle α1 to the second guide angle α2. The second guide angle α2 is a guide angle smaller than the first guide angle α1.
When the guide angle α is large, the curved shape of the paper T is formed large in the second direction D2. On the other hand, when the guide angle α is small, the curved shape of the paper T is formed small in the second direction D2.

  When the guide angle α is changed from the first guide angle α1 to the second guide angle α2, the curved convexity formed on the sheet T abutting against the registration guide surface 130a at the second guide angle α2 is It becomes smaller than the convex of the curved shape formed on the paper T in contact with the registration guide surface 130a at the one guide angle α1.

  Thereby, the leading edge pressing force of the sheet T is from the leading edge pressing force at the first guide angle α1 (the pressing force smaller than the second guide angle α2) in a state where the leading end of the sheet T is pressed toward the registration nip RN. The tip pressing force at the second guide angle α2 is increased (tip pressing force larger than the first guide angle α1).

  Thus, after correcting the skew of the paper T with the leading edge pressing force at the first guide angle α1 (pressing force smaller than the second guide angle α2), the leading edge pressing force at the second guide angle α2 (first guide angle α1). The skew correction of the paper T can be appropriately performed with a larger leading edge pressing force.

  As described above, the leading edge pressing force is suitably adjusted, the leading edge pressing force is insufficient, and skew (diagonal feeding) correction cannot be performed accurately, or the leading edge pressing force is excessive, and the leading edge of the paper T is excessive. It is suppressed that T1 enters the registration nip RN and skew (oblique feeding) correction cannot be performed accurately. Therefore, it is difficult to be affected by the type (rigidity) of the paper T, and appropriate skew correction is performed.

  In step ST8, after skew correction of the paper T performed by the leading edge pressing force at the first guide angle α1 and the second guide angle α2, the registration roller pair 80 is rotationally driven. The paper T is sent out toward the transfer nip N of the image forming unit GK. In this case, the skew-corrected paper T is guided to the registration nip RN with an appropriate leading edge pressing force.

According to the copying machine 1 of the present embodiment, the following effects are produced.
In the copying machine 1 of the present embodiment, in a stopped state, the leading end T1 of the paper T is once brought into contact with the registration roller pair 80 to bend the paper T, and then rotated to drive the paper T to the image forming unit GK. A pair of registration rollers 80 to be sent out, a conveyance roller 90 that conveys the paper T in the conveyance direction D1, and that can stop by bringing the leading end T1 of the paper T into contact with the registration roller pair 80 in a state where the paper T is sandwiched, and a registration roller The registration guide member 130 that guides the paper T that contacts the guide surface 130a to the registration nip RN, the guide angle changing unit 140 that changes the guide angle α, and the registration roller pair 80 are stopped, and the paper T is curved. A guide for controlling the guide angle changing unit 140 to change the guide angle α after contacting the resist guide surface 130a so as to press the convex side. And an angle change control unit 210.

  Therefore, the tip pressing force can be adjusted by changing the guide angle α after the paper T abuts the resist guide surface 130a so that the curved convex side can be pressed. Thus, after the skew correction of the paper T is performed with the leading edge pressing force at the predetermined guide angle α, the skew correction of the paper T can be appropriately performed with the appropriate leading edge pressing force by changing the guide angle α.

  Specifically, after correcting the skew of the paper T with the leading edge pressing force at a predetermined guide angle α, the leading edge pressing force is increased by changing the guide angle α to appropriately correct the skew of the paper T. Can do.

  For example, in the case of using the paper T with low rigidity (low stiffness), the front end pressing force is insufficient after the paper T comes into contact with the resist guide surface 130a so as to press the curved convex side. And the skew correction of the paper T can be suitably performed.

  Further, in the copier 1 in the present embodiment, the registration guide member 130 is formed in a planar shape that approaches the registration nip RN side as the registration guide surface 130a moves from the upstream side to the downstream side in the transport direction D1. The registration guide member 130 is supported so as to be rotatable about a first rotation axis J1 parallel to the axial direction of the registration roller pair 80 on the downstream side in the conveyance direction D1. Is rotated about the first rotation axis J1 to change the guide angle α.

  Therefore, the sheet T is appropriately guided toward the registration nip RN by rotating the registration guide member 130 to change the guide angle α. Thereby, the leading edge pressing force of the paper T can be adjusted, and the skew correction of the paper T can be performed reliably and appropriately.

  In the copier 1 according to the present embodiment, the guide angle change control unit is configured to bend the paper T based on the type information including the thickness information about the thickness of the paper T and / or the rigidity information about the rigidity of the paper T. When contacting the registration guide surface 130a so that the convex side of the shape can be pressed, the guide angle changing unit 140 is controlled so that the guide angle α is set to the first guide angle α1, and the paper T has a curved convex side. After the contact with the resist guide surface 130a so as to be pressed, the guide angle changing unit 140 is controlled so that the guide angle α is set to the second guide angle α2 smaller than the first guide angle α1.

  Therefore, when using a wide variety of sheets T having different thicknesses and stiffnesses, the guide angle α is changed so that it is not easily affected by the type of the sheet T, and the leading end T1 of the sheet T contacts the registration roller pair 80. It is possible to suitably adjust the tip pressing force at the time. For example, by performing a button operation for selecting the type of the paper T to be used, the front end pressing force when the front end T1 of the paper T abuts against the registration roller pair 80 is suitably set based on the type information of the paper T. It is possible to adjust.

  Further, the leading edge pressing force of the paper T is the first pressing force at the first guide angle α1 (the pressing force smaller than the second guide angle α2) in a state where the leading edge of the paper T is pressed toward the registration nip RN. It is increased to the tip pressing force at the two guide angles α2 (tip pressing force larger than the first guide angle α1).

  Thus, after correcting the skew of the paper T with the leading edge pressing force at the first guide angle α1 (pressing force smaller than the second guide angle α2), the leading edge pressing force at the second guide angle α2 (first guide angle α1). The skew correction of the paper T can be appropriately performed with a larger leading edge pressing force.

  Thus, even when using various types (stiffness) of paper T, it is possible to prevent skew correction due to insufficient tip pressing force or excessive tip pressing force. Appropriate skew correction can be performed.

  The first guide angle α1 is preferably set to a suitable guide angle for guiding the paper T to the registration nip RN. Thereby, in the case of the first guide angle α1, the paper T carried in from the transport direction D1 by the first transport roller pair 90 is more easily guided to the registration guide member 130 than in the case of the second guide angle α2.

As mentioned above, although preferred embodiment of this invention was described, this invention can be implemented with a various form, without being limited to embodiment mentioned above. For example, as shown in FIG. 5, it can also be configured as another embodiment. FIG. 5 is a perspective view showing the configuration of the registration guide member 130 and the guide angle changing unit 140, which are components of the registration mechanism unit RK in another embodiment.
For example, in the above-described embodiment, the support shaft 141 is rotated by rotating the guide angle changing drive unit 147, and the registration guide member 130 is rotated about the first rotation axis J1, but this is not limitative. Not.

  For example, the guide angle changing unit 140A in another embodiment shown in FIG. 5 may include a support shaft 141, an arm member 145, and a guide angle changing drive unit 147A. Specifically, the arm member 145 is configured by a plate-like member that is long in a direction orthogonal to the axial direction of the support shaft 141. One end of the arm member 145 is connected to the plus end of the support shaft 141 in the Y direction. The other end of the arm member 145 is connected to the output shaft 148A of the guide angle change drive unit 147A. The arm member 145 is supported in a substantially central portion so as to be rotatable about a shaft member 146 coaxial with the first rotation axis J1A parallel to the axial direction of the registration roller pair.

  The guide angle change drive unit 147A is configured to be drivable so that the output shaft 148A reciprocates linearly along the transport direction D1. Therefore, the guide angle change drive unit 147A rotates the registration guide member 130 around the first rotation axis J1A via the arm member 145. Thus, the guide angle changing unit 140A changes the guide angle α. The guide angle change drive unit 147A is configured by, for example, a solenoid.

  In the above-described embodiment, the guide angle change control unit 210 performs the skew correction of the paper T at the first guide angle α1, and then performs the skew correction of the paper T at the second guide angle α2. However, the present invention is not limited to this. The guide angle change control unit 210 may be configured to control the guide angle change unit 140 so that the skew correction of the paper T is performed at the first guide angle α1 after the skew correction of the paper T is performed at the second guide angle α2. Good.

  The guide angle change control unit 210 is configured to control the guide angle change unit 140 based on information such as the rigidity of the paper T stored in the storage unit 250, but is not limited thereto. For example, the guide angle change control unit 210 acquires information such as the rigidity of the paper T by detecting the size of the curved shape formed on the paper T with a sensor or the like, and changes the guide angle based on this information. The configuration may be such that the unit 140 is controlled.

The type of the image forming apparatus of the present invention is not particularly limited, and may be a copier, a printer, a facsimile, or a complex machine thereof.
Further, the sheet-like transfer material is not limited to paper, and may be a film sheet, for example.

  DESCRIPTION OF SYMBOLS 1 ... Copy machine (image forming apparatus), 80 ... Registration roller pair, 90 ... 1st conveyance roller pair (conveyance roller), 130 ... Registration guide member (guide member), 130a ... Registration guide surface (guide) Surface), 140... Guide angle change unit, 210... Guide angle change control unit, 810... Registration nip plane, .alpha.... Guide angle, T .. paper (transfer material), T1. ... Regist nip, GK ... Image forming part

Claims (3)

An image forming unit for forming an image on a sheet-like transfer material;
A pair of registration rollers that form a registration nip, and in a stopped state, the tip of the material to be transferred is once brought into contact with the pair of registration rollers to bend the material to be transferred, and then rotated to drive the material to be transferred. A pair of registration rollers for feeding the material to the image forming unit;
The registration roller pair is disposed upstream of the transfer material in the conveyance direction, conveys the transfer material in the conveyance direction, and holds the transfer material in a state where the tip of the transfer material is nipped. A transport roller that can be stopped by contacting the registration roller pair;
The guide surface, which is disposed between the registration roller pair and the conveyance roller and is formed in a planar shape that approaches the registration nip side as it goes from the upstream side to the downstream side in the conveyance direction, and is curved. A guide member that contacts the transfer material so as to press the convex side of the curved shape, and guides the transfer material that contacts the guide surface to the registration nip; and
A guide angle changing unit that changes a guide angle that is an angle of the guide surface with respect to a registration nip plane including the registration nip when viewed from the axial direction of the registration roller pair;
When the registration roller pair is in a stopped state, a part of the material to be transferred comes into contact with the guide surface after the material to be transferred comes into contact with the guide surface so as to press the curved convex side. A guide angle change control unit that controls the guide angle change unit to change the guide angle in a state;
An image forming apparatus comprising: The guide member is supported to be rotatable about a first rotation axis parallel to the axial direction of the resist roller pair on the downstream side of the conveying direction of the guide member,
The image forming apparatus according to claim 1, wherein the guide angle changing unit changes the guide angle by rotating the guide member about the first rotation axis. The guide angle change control unit is configured to set the guide angle to a first guide angle when the material to be transferred comes into contact with the guide surface so as to press the convex side of the curved shape. And the guide material is set to a second guide angle smaller than the first guide angle after the material to be transferred comes into contact with the guide surface so as to press the convex side of the curved shape. The image forming apparatus according to claim 1, wherein the guide angle changing unit is controlled.

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