JPH05273725A - Method for controlling nip mechanism of image forming device - Google Patents

Abstract

PURPOSE:To prevent the wasteful consumption of a photosensitive member by preventing the photosensitive member from being newly fed at the time of restarting heating and developing. CONSTITUTION:The photosensitive transfer type photosensitive member F fed from a supply cartridge 11 is exposed in an exposing part 10, passes through a nip mechanism 100, heated and developed in a heating and developing part 20, pressure-transferred on a paper P in a pressure transfer part 30, and taken up in a photosensitive material recovering part 40. When the member F is taken up to a take-up shaft 41 and allowed to approach and come in contact with a heating roller 21 while retreating rollers 22 and 23 are moved from the position of a dotted line to the position of a continuous line, rollers 103 and 104 are closed and rollers 101 and 102 are opened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a nip mechanism of an image forming apparatus (specifically, a copying machine, a printer, a plotter, a facsimile, etc.) for forming a color image using a so-called photosensitive transfer type photosensitive member. It is about.

[0002]

2. Description of the Related Art In this type of image forming apparatus, a photosensitive material supplying section, an exposing section, a heat developing section, a pressure transfer section, and a photosensitive material collecting section are provided inside a main body of the apparatus along a conveying path. The photosensitive material supply unit stores (rolls) a film-shaped photosensitive member around a supply shaft so that the photosensitive member can be supplied to the exposure unit. The exposure unit takes in the reflected light of the original and scan-exposes the image on the photosensitive surface of the photosensitive member to form a latent image. The heating and developing section heats the photosensitive member to heat and develop the latent image formed on the photosensitive member. The pressure transfer portion superimposes a photosensitive member and a transfer member such as a sheet, pressure transfers the developed image of the photosensitive member to the transfer member, and separates the photosensitive member and the transfer member. Then, in the sensitive material collecting portion, the photosensitive member after the transfer is collected. The transfer members are sequentially ejected and stocked in a stacked state.

The photosensitive member is constructed by using a plastic film or paper as a support and applying microcapsules encapsulating a photosensitive material, a coloring material or the like on the surface thereof. Using this photosensitive member, a photoreaction is caused in the photosensitive material in the exposed part (latent image formation), and the change in the state is influenced by the heating in the heating and developing part to affect the color material to selectively solidify the color material (development). Then, the pressure transfer section crushes the microcapsules to transfer the non-solidified color material onto the paper to form an output image.

More specifically, the microcapsule has a diameter of about 10 [μm]. For example, a microcapsule containing a yellow colorant, a microcapsule containing a magenta colorant, and a microcapsule containing a cyan colorant. There is a capsule. The photosensitive member is formed by mixing a large number of three color microcapsules and coating the mixture on a support. When the photosensitive member is exposed by the reflected light (optical image) of the original, the yellow microcapsules are blue (complementary color of yellow).
, The magenta microcapsules respond to green (magenta complementary color) light, the cyan microcapsules respond to red (cyan complementary color) light, and the photoreacted microcapsules form a latent image. To be done. After that, when the photosensitive member is heated (about 150 ° C.) in the heating and developing section, microcapsules that photo-react to form a latent image are cured (solidified), and those that are not are not cured. This is called selective solidification. When the photosensitive member and the paper are overlapped and pressed by the pressure transfer unit, the uncured microcapsules (which do not form a latent image) are crushed, and the color material in the microcapsules is transferred to the paper for color printing. .. Thus, high resolution dry color printing can be performed.

[0005]

In the heat developing section, heat development is carried out by winding the photosensitive member around the heat roller at a predetermined angle. When the heat development is completed, the retracting roller comes between the heating roller and the photosensitive member, and the photosensitive member separates from the heating roller. When heat development is performed again, the retracting roller escapes and the photosensitive member is wound up, and the photosensitive member comes into contact with the heating roller. By the way, when the heat development is carried out again, the photosensitive member is taken up, but after the photosensitive member comes into contact with the heating roller at this time, it is necessary to prevent the photosensitive member from being newly fed from the supply unit.
Conventionally, such a device has not been made.

In view of the above-mentioned conventional technique, the present invention provides a method for controlling a nip mechanism of an image forming apparatus which prevents the photosensitive member from being newly fed out from the supply portion when the heat development is restarted. With the goal.

[0007]

SUMMARY OF THE INVENTION According to the present invention for solving the above-mentioned problems, a photosensitive transfer type photosensitive member is exposed in an exposure section, heat-developed in a heat developing section, and pressure-transferred to a transfer member in a pressure transfer section. A nip mechanism installed between the exposure section and the heat development section of the image forming apparatus wound in the sensitive material collecting section, wherein a feed roller that is directly connected to a main motor and rotates, and a photosensitive member are sandwiched between them. And a feed nip roller that contacts and separates the feed roller, a tension roller that applies a back tension to the photosensitive member, and a tension nip roller that grips the photosensitive member and contacts and separates the tension roller, a nip motor, and a nip motor. As the rotational drive changes and the rotational position changes, the feed nip roller is separated from the feed roller and the tension nip roller is The first mode away from the Deployment roller,
The second mode in which the feed nip roller is in contact with the feed roller and the tension nip roller is separated from the tension roller, the third mode is in which the feed nip roller is in contact with the feed roller and the tension nip roller is in contact with the tension roller, and the feed nip roller is separated from the feed roller and the tension nip roller is in tension. In a method of controlling a nip mechanism including a cam mechanism that sequentially changes to a fourth mode in which the photosensitive member is in contact with a roller, a photosensitive member separated from the heating roller of the heating and developing unit in order to shift from the non-heated and developed state to the heated and developed state. Is brought into contact with the heating roller while being wound up in the sensitive material collecting section, the feed nip roller and the tension nip roller are set to the fourth mode.

[0008]

In order to shift from the non-heated development state to the heat development state, the photosensitive member is sandwiched by the tension roller and the tension nip roller when the heated development unit is wound by the photosensitive material collecting unit, so that the photosensitive member is newly supplied from the supply unit. It will not be paid out.

[0009]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 shows a copying machine according to an embodiment of the present invention. As shown in the figure, a document 2 is placed on a document table 1 provided so as to be movable in the direction of arrow A, and the document 2 is pressed by a document table cover 3. The light rays emitted from the red lamp 4, the green lamp 5, and the blue lamp 6, which are the light sources, illuminate the document 2. When the shutter 7 is opened, the reflected light from the original 2 passes through the lens 8 and forms an image on the photosensitive member F moving on the exposure table 9.
In this way, the exposure unit 10 that performs so-called scan exposure is formed.

The unexposed photosensitive member F housed in the supply cartridge 11 is sent out in accordance with the rotation of the supply shaft 12. The fed photosensitive member F is exposed on the exposure table 9 to form a latent image, and then passes through the feed roller 101 and the feed nip roller 102 of the nip mechanism 100 and between the tension roller 103 and the tension nip roller 104 to perform heat development. Sent to department 20. Although the detailed operation is omitted, the feed roller 101 and the feed nip roller 102 keep the conveyance speed of the photosensitive member F in the exposure unit 10 constant, and the tension roller 103 and the tension nip roller 104 cause the photosensitive member after the heat developing unit 20 to be conveyed. Absorb the looseness of F and prevent wrinkles from occurring. The detailed structure and operation of the nip mechanism 100 will be described later.

The heating roller 21 of the heating and developing section 20 is heated by a halogen lamp (not shown) incorporated therein. The photosensitive member F on which the latent image is formed is wound around the heating roller 21 for a predetermined angle to be heated and developed, and is also U-turned to be sent to the pressure transfer unit 30. The retracting rollers 22 and 23 of the heating and developing unit 20 are located at the positions indicated by the solid line in the drawing when the photosensitive member F is heated and developed, but when the heating and development is completed, the arc-shaped progress indicated by the arrow B in the drawing is reached. Then, the photosensitive member F is moved to the position shown by the dotted line in the figure, and the photosensitive member F is retracted from the heating roller 21.

The pressure transfer section 30 is constructed by adding a separation roller 34 and a pinch roller 35 to a pressure transfer device having an upper roller 31, an intermediate roller 32 and a lower roller 33. The middle roller 32 and the lower roller 33 can be moved in the vertical direction in the figure by the driving of a pressure rolling opening / closing motor (not shown in FIG. 1), and the upper roller 31 is driven by the pressure rolling driving motor (see FIG.
(Not shown) rotates by driving. Then, when the middle roller 32 is brought into contact with the upper roller 31 and the upper roller 31 is rotated, the photosensitive member F and the paper P that is the transfer member are transferred.
And are introduced between the rollers 31 and 32 in an overlapping manner, and the developed image on the photosensitive member F is transferred to the paper P. The separation roller 34 is provided in the vicinity of the downstream side of the pressure transfer device, and the conveyance path of the photosensitive member F is bent inward at this portion at an acute angle to forcibly separate the photosensitive member F and the paper P. It is like this. The pinch roller 35 is moved to the position indicated by the solid line in the figure when the photosensitive member F is conveyed by driving the pressure-change opening / closing motor, and sandwiches the photosensitive member F with the upper roller 31 to apply a conveying force thereto. The separated photosensitive member F is appropriately sent to the sensitive material collecting unit 40 via the pinch roller 35. In the copying machine of the present embodiment, the driving of the compression opening / closing motor causes the rollers 32 and 33 to open / close with respect to the roller 31 and the pinch roller 35 to move.

The photosensitive material collecting section 40 has a winding shaft 41, and the used photosensitive member F is wound around the winding shaft 41. When all the used photosensitive member F is wound up, the winding shaft 41 becomes free by switching the clutch. In this state, the supply shaft 12 of the supply unit is reversely driven, and the used photosensitive member F is finally collected in the supply cartridge 11.

On the other hand, the paper feed section 50 includes a paper feed cassette 51 for feeding the paper P as a cut paper and a paper feed cassette 51.
Half-moon roller 52 that feeds the sheets one by one from the sheet, and the sheet P
A guide roller 53 that changes the path of the sheet, a sheet feed roller 54 that guides the fed sheet P to the pressure transfer unit 30, and the like. The half-moon roller 52 has a straight line portion 52a and a circular arc portion 52.
b has a rubber peripheral surface consisting of
The leading edge of the paper P is scratched at the boundary between the a and the arc portion 52b, and the leading edge of the paper P is moved to the paper feed roller 5 at the succeeding arc portion 52b.
The sheet P can be sent out until the number of sheets reaches 4.
The feeding of the paper P is started in synchronization with the conveyance of the photosensitive member F so that it can be superposed on the exposed portion of the photosensitive member F. The paper discharge unit 60 includes a paper discharge cassette 61 that stores the paper P on which the image has been transferred, and a paper discharge roller 62 that guides the paper P from the pressure transfer unit 30 to the paper discharge cassette 61. The paper discharge roller 62 is configured to slightly overfeed the paper feed roller 54. The slip rotation of the paper discharge roller 62 causes the paper P to be fed out, and the paper P at the time of pressure transfer.
Tension is applied to prevent wrinkles and jams.

Next, the structure and operation of the nip mechanism 100 will be described with reference to FIGS. 2 shows a nip mechanism 10
FIG. 4 is a plan view showing 0 unfolded, and FIG. 3 is a front view showing each nip state mode. As shown in both figures, the support shaft 105
A lever 106, 107 is rotatably provided on the lever 106. The feed nip roller 10 is provided at the left end of the lever 106.
2, a tension nip roller 104 is pivotally supported at the left end of the lever 107. Cams 109 and 110 are fixed to the cam shaft 108. The cam 109 is in contact with the right end of the lever 106, and the cam 110 is in contact with the right end of the lever 107. Cam shaft 108 and cam 10
9, 110 are nip motors M via a gear mechanism 111.
It receives the rotational force from n and rotates. In this case lever 10
6, 107 are pulled by springs 112, 113 and swing according to the rotation of the cams 109, 110. The rotation supporting portions of the rollers 101 and 103 are fixedly installed.

The home positions of the cams 109 and 110 are accurately positioned by the cams 109 and 110 contacting the positioning member. When the home position is set, the mode 1 is set as shown in FIG. 3A, and the roller 102 separates from the roller 101 and the roller 104 separates from the roller 103. The nip motor Mn rotates normally and the cams 109, 1
When 10 rotates from the mode 1 by 90 °, the mode becomes the mode 2 as shown in FIG.
And the roller 104 is separated from the roller 103. When the cams 109 and 110 are further rotated by 90 ° from the mode 2, the mode is changed to the mode 3 as shown in FIG. 3B, and the roller 102 contacts the roller 101 and the roller 10
4 is in contact with the roller 103. Cam 109,1
When 10 further rotates 90 degrees from mode 3, FIG.
The mode 4 is set as shown in FIG.
01, and the roller 104 comes into contact with the roller 103. When the cams 109 and 110 are rotated in the reverse direction from the state of mode 4, the state sequentially changes from mode 3 to mode 2 to mode 1.

Next, the relationship between the main motors and the operating parts operated by the motors will be described with reference to FIG. Control unit 200
Controls the drive / stop of each motor Mm, Moc, Md, Mn, Mh, and each clutch C2. ON / OFF control of C3 and C4.

The supply shaft 12 is directly connected to the main motor Mm via a one-way clutch C1 to rotate. The winding shaft 41 is connected to the main motor Mm via the winding clutch C2, and rotates when the clutch C2 is on to wind up the photosensitive member F and becomes free when the clutch C2 is off. The feed roller 101 is directly connected to the main motor Mm and rotates. The document table 1 advances in the A1 direction (forward) when the normal rotation clutch C3 is turned on while the main motor Mm is normally rotated, and advances in the A1 direction (reverse) when the reverse rotation clutch C4 is turned on.

The middle roller 32 is brought into contact with and separated from the upper roller 31 by driving the pressure-change opening / closing motor Moc. The pinch roller 35 comes into contact with and separates from the upper roller 31 by driving the pressure-change opening / closing motor Moc. As shown in Table 1 below, the contact and separation states of the rollers 32 and 35 with respect to the upper roller 31 include fully open, half open, and fully closed.

[0021]

[Table 1]

Further, the upper roller 31 is rotated by the driving of the pressure driving motor Md.

The feed nip roller 102 and the tension nip roller 104 are brought into various modes as shown in FIG. 3 by driving the nip motor Mn.

The retract rollers 22 and 23 are the heat-current retract motor M.
By driving h, it moves between the position shown by the solid line and the position shown by the dotted line in FIG.

Next, the operation of the copying machine of the embodiment will be described separately for image formation and preparation.

First, the operation during image formation will be described with reference to FIG. When the image forming operation is started, the preparatory operation (described later) is completed, the nip rollers 102 and 104 are in the mode 4 (FIG. 3 (d)), and the evacuation rollers 22,
23 returns to the position shown by the solid line in FIG.
1 and the middle roller 32 and the pinch roller 35 are apart from each other and are in a fully opened state.

The shutter 7 opens after the time t1 in FIG. 5, and the reverse clutch C4 (see FIG. 4) at the times t2 to t3.
Is turned on, the main motor Mm is rotated in the forward direction, and the document table 1 is moved to A.
It retreats in two directions, and the right end of the document table 1 is located to the left of the lens 8 in FIG.

From time t4 to t5, the pressure-change open / close motor Moc rotates in the normal direction, and the middle roller 32 remains separated from the upper roller 31, but the pinch roller 35 comes into contact with the upper roller 31 to be in a half-open state. At times t5 to t6, the nip motor Mn rotates in the reverse direction and the state of the nip rollers 102 and 104 changes from mode 4 to mode 3. That is, as shown in FIG. 6A, the photosensitive member F is sandwiched between the feed nip roller 102 and the feed roller 101, and the photosensitive member F is sandwiched between the tension nip roller 104 and the tension roller 103.

At time t6, the main motor Mm and the compression drive motor Md start to rotate normally, the winding clutch C2 is turned on to feed the photosensitive member F, and the rotation clutch C
3 is turned on, the document table 1 begins to move forward in the A1 direction (moves to the right in FIG. 1), and exposure starts. Also, the photosensitive member F
As it is fed, it comes into contact with the heating roller 21, so that thermal development is also started.

From time t7 to t8, the pressure-change open / close motor Moc rotates in the normal direction, and the middle roller 32 and the pinch roller 35 come into contact with the upper roller 31 to be in a fully closed state. At time t8, the pressure transfer unit 30 is synchronized with the conveyance of the photosensitive member F by the paper feeding unit 50 so that the paper P overlaps the exposed portion of the photosensitive member F.
Sent to. Thus, pressure transfer is performed from time t8.

At time t9, the exposure is completed and the forward clutch C
3 is turned off, the reverse rotation clutch C4 is turned on, and the exposure table 1 is set to A.
When the exposure table 1 retreats in two directions and the exposure table 1 reaches the state shown in FIG. 1, the reverse rotation clutch C4 is turned off and the exposure table 1 returns to the initial position.

From time t9 to t10, the nip motor Mn rotates normally and the state of the nip rollers 102 and 104 changes to the mode 3 mode.
It changes to mode 4. That is, as shown in FIG. 6C, the feed roller 101 and the feed nip roller 10
2 and the tension roller 103 and the tension nip roller 104 remain closed.

At times t11 to t12, the thermal current retract motor M
When h is rotated in the normal direction, the retreat rollers 22 and 23 move from the position shown by the solid line to the position shown by the dotted line in FIG. 1, and the photosensitive member F separates from the heating roller 21 and enters the retracted state.

From time t12 to t13, the compression rolling opening / closing motor M
oc reverses and the middle roller 32 and the pinch roller 35 are separated from the upper roller 31 to be in a fully opened state, and the pressure transfer is completed.

After the pressure transfer is completed, the photosensitive member F is sent out until the paper P is completely discharged. Time t1
At 4, the sheet discharge is completed, the main motor Mm and the pressure transfer drive motor Md are stopped, the winding clutch C2 is turned off, and the feeding of the photosensitive member F is stopped.

From time t14 to t15, the nip motor Mn is
Is reversed to change the state of the nip rollers 102 and 104 from mode 4 to mode 1.

When exposure is performed during the above-described image formation (t6 to t9), the nip rollers 102 and 104 are in the mode 3 as shown in FIG. 6 (a). Therefore, the feed nip roller 102 and the main motor Mm
Thus, the photosensitive member F is sandwiched and pulled out by the feed roller 101 rotating at a constant speed, so that the feeding speed of the photosensitive member F in the exposure unit 10 is constant. Further, since the photosensitive member F is sandwiched by the tension roller 103 and the tension nip roller 104 to apply the back tension to the photosensitive member F, wrinkles do not occur after the heating and developing unit 20.

Since the tension roller 103 is set so that the rotation speed thereof is slightly slower than that of the feed roller 101, as the exposure progresses, as shown in FIG. Between
The photosensitive member F is loosened. However, the speed of the photosensitive member F in the exposure unit 10 is constant, and the optimum back tension is applied to the photosensitive member F after the heating and developing unit 20.

When the exposure is completed, the nip rollers 102, 1
Since 04 changes from mode 3 to mode 4 as shown in FIG. 6C (time t9 to t10), the slack decreases as the photosensitive member F is fed, and finally the slack disappears. Of course, at this time as well, the optimum back tension is applied to the heating and developing section 20 and thereafter.

After all, as shown in FIGS. 6A, 6B and 6C, the state of the nip rollers 102 and 104 is set to the mode 3 during the exposure, and the state of the nip rollers 102 and 104 is set to the mode 4 after the exposure is completed. In addition, good exposure can be performed, and wrinkles do not occur on the photosensitive member F, and high-quality copying can be performed. When a plurality of copies are made for one original drawing, the operations shown in FIGS. 6A, 6B and 6C are repeated. That is, the mode 3 is set at the time of heat development, and when the heat development for one sheet is shifted to the next heat development, the mode 4 is temporarily set to remove the slack, and then the next heat development is performed. To do.

Next, the operation at the time of preparation will be described with reference to FIG. At time t15, the nip rollers 102 and 104 are in the mode 1, the retracting rollers 22 and 23 are in the retracted state where the photosensitive member F is not in contact with the heating roller 21 at the position shown by the dotted line in FIG. 1, and the rollers 32 and 35 are the rollers 31. It is in the front open state, which is far away from.

From time t16 to t17, the winding clutch C
When the main mode Mm is reversed with 2 turned off, the photosensitive member F is rewound, and the portion of the unexposed portion that has been fed to the downstream side of the nip mechanism 100 is rewound. At time t17, the boundary between the thermal phenomenon portion and the non-thermal phenomenon portion reaches the position of the rollers 103 and 104, and when this state is reached, the rewinding ends.

From time t18 to t19, the nip motor Mn is
Is rotated in the normal direction, the rollers 102 and 104 are changed from the mode 1 to the mode 4, and the photosensitive member F is sandwiched by the rollers 103 and 104.

At times t20 to t21, the thermal current retract motor M
When h is reversed, the retracting rollers 22 and 23 are changed from the dotted line state in FIG. 1 to the solid line state. Take-up clutch C2
Is turned on and the main motor Mm rotates in the normal direction, so that as the photosensitive member F advances from the position indicated by the dotted line in FIG. 1 to the position where it comes into contact with the heating roller 21, the surplus thereof is taken up by the take-up shaft 41. To go.

When the photosensitive member F changes from the retracted state to the contact state, the surplus portion is wound around the winding shaft 41. At this time, the rollers 102 and 104 are set to the mode 4 and the rollers 103 and 104 are used. Since the photosensitive member F is sandwiched, the photosensitive member F is not newly fed from the supply shaft 12 after the surplus is wound. The reason is,
The winding clutch C2 has a built-in torque limiter so that when the tensile force acting on the winding shaft 41 exceeds a predetermined value, the rotational force is not transmitted to the winding shaft 41. This is because the back tension is larger than the above predetermined value.

The preparation operation is completed at time t22. Time t
The state 22 is the same as the state at time t1 in FIG.

[0047]

According to the present invention as described in detail with reference to the above embodiments, in order to shift from the non-heated development state to the heat development state, the photosensitive member is wound up in the sensitive material collecting section and brought close to the heating roller. Since the photosensitive member is sandwiched by the tension roller and the tension nip roller when they are brought into contact with each other, it is possible to prevent the photosensitive member from being newly fed from the supply unit. Therefore, the photosensitive member can be saved without being wasted.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a copying machine to which an embodiment of the present invention is applied.

FIG. 2 is a plan view showing a developed nip mechanism.

FIG. 3 is a front view showing each nip state mode of the nip mechanism.

FIG. 4 is an explanatory diagram showing a relationship between each motor and each operating portion.

FIG. 5 is a timing chart showing an operation at the time of image formation of the embodiment.

FIG. 6 is an explanatory diagram showing a nip operation during image formation.

FIG. 7 is a timing chart showing an operation at the time of preparation of the embodiment.

[Explanation of symbols]

 1 Document Plate 2 Document 3 Document Plate Cover 4, 5, 6 Lamp 7 Shutter 8 Lens 9 Exposure Plate 10 Exposure Unit 11 Supply Cartridge 12 Supply Shaft 20 Heat Development Unit 21 Heating Roller 22, 23 Retraction Roller 30 Pressure Transfer Unit 31 Upper Roller 32 Middle Roller 33 Lower Roller 34 Separation Roller 35 Pinch Roller 40 Sensitive Material Collecting Section 41 Take-up Shaft 50 Paper Feeding Section 51 Paper Feeding Cassette 52 Half Moon Roller 53 Guide Roller 54 Paper Feeding Roller 60 Paper Ejecting Section 61 Paper Ejecting Cassette 62 Ejecting Paper Roller 100 Nip mechanism 101 Feed roller 102 Feed nip roller 103 Tension roller 104 Tension nip roller 105 Support shaft 106,107 Lever 108 Cam shaft 109,110 Cam 111 Gear mechanism 112,113 Spring 200 Control unit F Photosensitive member P Paper Mm Inmota Moc 圧転 closing motor Md 圧転 Mn Nippumota Mh heat current recession motor C1, C2, C3, C4 clutch

Claims (1)

[Claims] 1. An image forming apparatus in which a photosensitive transfer type photosensitive member is exposed in an exposure unit, heat-developed in a heat developing unit, pressure-transferred to a transfer member in a pressure transfer unit, and wound in a sensitive material recovery unit. A nip mechanism installed between the exposure unit and the heat development unit, which is directly connected to a main motor and rotates,
A roller group including a feed nip roller that sandwiches the photosensitive member between them to contact and separate from the feed roller, a tension roller that applies a back tension to the photosensitive member, and a tension nip roller that sandwiches the photosensitive member into contact with and separate from the tension roller. The nip motor and the first mode in which the feed nip roller is separated from the feed roller and the tension nip roller is separated from the tension roller as the rotation position changes as the nip motor is rotationally driven. The second mode in which the feed nip roller is separated from the tension roller, the third mode in which the feed nip roller is in contact with the feed roller and the tension nip roller is in contact with the tension roller, and the feed nip roller is in the feed roller. In a method of controlling the nip mechanism, which comprises a cam mechanism that sequentially changes to a fourth mode in which the tension nip roller is brought into contact with the tension roller, the heating roller of the heating and developing unit is changed from the non-heated development state to the heat development state. The nip mechanism of the image forming apparatus is characterized in that the feed nip roller and the tension nip roller are set to the fourth mode when the photosensitive member which has been separated from Control method.