JP2008145520A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a user with an image forming apparatus configured such that the drum drive gear of an image forming apparatus main body and the photoreceptor drum of a toner cartridge are drive-connected by a coupling mechanism and a toner cartridge drive system is not interposed in transfer roller drive transmission, the image forming apparatus being designed so as to ensure high reliability, a noise reduction, and high image quality by preventing the photoreceptor drum from being rotated by the friction drive of a transfer roller before the rotation of the photoreceptor drum after the drive transmission and the coupling of them, resulting in coupling failure, overload on the transfer roller drive gear, and hence a tooth skip. <P>SOLUTION: Upstream of the drive transmission system of a transfer roller drive gear, the plurality of gears on the same axis are disposed, and an energizing member is disposed between the upstream and downstream coaxial gears. Thereby, a time-lag is set until the drive is transmitted from the upstream coaxial gear to the downstream coaxial gear. This prevents the transfer roller from rotating before the photoreceptor drum and the drum drive gear couple to each other. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus having a replaceable toner cartridge, such as a copying machine, a facsimile, a printer, and a composite device thereof.

  In recent image forming apparatuses, various measures are taken to improve image quality.

  FIG. 4 is a perspective view illustrating the image forming apparatus A and the toner cartridge B. FIG.

  For example, in the past, in the photosensitive drum on the toner cartridge side and the transfer roller drive transmission system on the image forming apparatus main body side, the drive was transmitted to the transfer roller drive gear by a gear provided coaxially with the photosensitive drum. There is also an example in which the drive path to the photosensitive drum and the drive path to the transfer roller drive gear are separated in order to reduce as much as possible the gear meshing vibration to the roller (see Patent Document 1, for example).

  Such a conventional image forming apparatus will be described with reference to FIGS.

  Here, the operation and configuration until the toner cartridge B is mounted on the image forming apparatus main body A and the drive is transmitted will be described.

  FIG. 9 is a drive transmission system perspective view of the image forming apparatus main body A before the toner cartridge B is mounted. The right drive gear train 2 is driven and transmitted by the motor 1 as a drive source, and the left drive gear train 4 is rotated by connecting the left and right drive transmissions by the conveying roller 3. A transfer roller drive gear 6 that transmits drive to the transfer roller 5 is provided on the most downstream side of the left drive gear train 4.

  The right drive gear train 2 has a drum drive gear 7 and has a polygonal coupling hole 9 connected to the photosensitive drum 8 of the toner cartridge B at the center.

  FIG. 10 is a perspective view of the drive transmission system of the image forming apparatus main body A after the toner cartridge B is mounted, and a drive transmission polygon fixed to the photosensitive drum 8 is provided on the right end surface of the photosensitive drum 8. A coupling shaft 10 is provided.

  In the above configuration, when the toner cartridge B is mounted on the image forming apparatus A, the photosensitive drum 8 contacts the transfer roller 5. At this time, since the coupling shaft 10 on the end face of the photosensitive drum 8 and the coupling hole 9 in the center of the drum drive gear 7 are polygonal to each other, they are usually not engaged normally.

  Next, when the main body drive transmission system is driven by the start of the motor 1, the transfer roller 5 is rotated by the drive transmission to the right drive gear train 2, the transport roller 3, the left drive gear train 4, and the transfer roller drive gear 6. start.

At this time, the coupling hole 9 of the drum drive gear 7 also rotates, but there is a time difference until it engages with the polygon of the coupling shaft 10 of the photosensitive drum 8. When the coupling hole 9 and the coupling shaft 10 are connected, the photosensitive drum 8 rotates, the rotation speed difference with the transfer roller 5 becomes appropriate, and the image forming apparatus A becomes operable.
JP 9-297473 A

  However, the conventional image forming apparatus has the following problems.

The first challenge is
Before the photosensitive drum of the toner cartridge and the drum driving gear of the main body of the image forming apparatus are coupled, the photosensitive drum is frictionally driven and rotated by the frictional force of the transfer roller that has been rotated first. Since the ring shaft also rotates in the same direction as the coupling hole of the drum drive gear, there is a possibility that the time until the mutual coupling is delayed. In the worst case, when the initial operation check of the main body of the image forming apparatus is not performed, there is a possibility that the user may be warned as a defective mounting of the toner cartridge, and the user may be concerned about the malfunction of the main body. There was a problem.

The second issue is
Before the photosensitive drum of the toner cartridge and the drum driving gear of the image forming apparatus are coupled, the photosensitive drum is frictionally driven and rotated by the frictional force of the transfer roller that has been rotated first. At this time, since the photosensitive drum has a high load, a considerable load is required for the transfer roller to rotate by friction. For this reason, there is a possibility that the transfer roller drive gear will be overloaded, causing tooth jumps with the previous gear, and if tooth jumps occur, the abnormal noise may cause the user to be concerned about malfunction of the main body. there were.

The third issue is
In order to prevent the transfer roller drive gear from being overloaded and tooth jumping with the preceding gear, it is also possible to have a positional relationship such that the preceding gear is bitten by driving rotation with respect to the transfer roller driving gear. However, there are problems in that the number of gears increases and the space efficiency decreases due to restrictions due to the combination of the transfer roller drive gear and the transmission gear from the drive source and the combination of the shaft position and the rotation direction.

The present invention has been made in view of the above problems, and its object is to
A first object is to provide an image forming apparatus excellent in reliability with a margin in operation performance without delaying the time until the photosensitive drum and the drum driving gear are coupled.

  Second, avoid the possibility of tooth jumping between the transfer roller drive gear and its predecessor gear, prevent abnormal noise due to tooth jumping and the occurrence of image defects due to gear scratches, and provide low-noise, high-quality image forming devices There is to do.

  A third object is to provide a small and low-priced image forming apparatus by minimizing the number of gears used and improving space efficiency.

In order to achieve the above object, the first invention according to the present application,
A removable toner cartridge is mounted on the main body of the image forming apparatus, and a drive transmission unit of the main body of the image forming apparatus that drives the photosensitive drum of the toner cartridge is configured by a coupling. In the image forming apparatus in which the roller drive is transmitted from the drive system of the image forming apparatus main body without passing through the drive transmission system of the toner cartridge,
A plurality of gears are coaxially provided upstream of the drive transmission system of the transfer roller drive gear, the upstream coaxial gear is connected to a drive transmission gear from a drive source, and the downstream coaxial gear is a drive transmission gear to the transfer roller. Connected, the upstream coaxial gear and the downstream coaxial gear have a stopper portion that can connect and transmit each rotation, and a biasing member is provided between the upstream coaxial gear and the downstream coaxial gear, The biasing member biases the drive transmission of the upstream coaxial gear and the downstream coaxial gear away from each other when the transfer roller is unloaded, and when the load is applied to the transfer roller, The biasing member is charged by the drive rotation of the upstream coaxial gear, and the drive transmission is enabled when the upstream coaxial gear and the stopper portion of the downstream coaxial gear abut against each other.

In the above configuration,
In a state where the toner cartridge is mounted on the image forming apparatus main body and a load is applied to the transfer roller, the upstream coaxial gear rotates idly until it abuts against the stopper portion of the downstream coaxial gear by the drive rotation of the upstream coaxial gear. When the stopper portion comes into contact, drive transmission to the downstream coaxial gear is possible, and the drive transmission to the transfer roller is transmitted with a time difference. At this time, the biasing member acts to be charged.

  Further, when the toner cartridge is pulled out from the image forming apparatus main body and no load is applied in a state where the photosensitive drum is loaded on the transfer roller, the charged biasing member is connected to the upstream coaxial gear and the downstream coaxial gear. The gear drive transmission is urged in a separating direction, and the downstream coaxial gear rotates to cause the transfer roller to rotate idly to release the charge of the urging member.

Next, in order to achieve the above object, the second invention according to the present application is:
The image forming apparatus according to claim 1,
From the state where the upstream coaxial gear and the downstream coaxial gear are separated by the biasing member, the number of teeth intervening in the rotation angle at which both the stopper portions abut is equal to or greater than the total number of teeth of the transfer roller driving gear. It is characterized by being.

In the above configuration,
By making the number of teeth from the start of rotation of the upstream coaxial gear to the transmission of the drive to the downstream coaxial gear equal to or greater than the total number of teeth of the transfer roller drive gear, the transfer roller rotates at least for the time of one transfer roller. Thus, the transfer roller does not rotate until the drive transmission portion of the image forming apparatus main body and the coupling portion provided on the photoconductive drum are connected without frictionally rotating the photoconductive drum.

Next, in order to achieve the above object, the third invention according to the present application is:
The image forming apparatus according to claim 1, wherein
The downstream coaxial gear is a pre-stage gear that meshes with the transfer roller driving gear.

In the above configuration,
In a state where the photosensitive drum is loaded on the transfer roller, the toner cartridge is pulled out from the main body of the image forming apparatus. When no load is applied, the charged biasing member drives the upstream coaxial gear and the downstream coaxial gear. The transfer roller is energized in the direction of separation, and the downstream coaxial gear rotates so that the transfer roller idles and the charge of the biasing member is released. By using the front gear, the meshing position of the gears becomes one place. As a result, the drive transmission efficiency can be used most effectively, so that the urging force of the urging member can be set to a minimum, and the stress on the upstream coaxial gear and the downstream coaxial gear can be minimized.

Next, in order to achieve the above object, the fourth invention according to the present application is:
The image forming apparatus according to claim 1, wherein
The biasing member is a torsion coil spring.

In the above configuration,
By installing a torsion coil spring between the upstream coaxial gear and the downstream coaxial gear, it is possible to increase the rotation angle until the drive transmission stopper portion of the upstream coaxial gear contacts the stopper portion of the downstream coaxial gear. . This acts so that the time from when the upstream coaxial gear rotates to when the drive is transmitted to the downstream coaxial gear can be set longer.

  As described above, according to the first aspect of the present application, when the toner cartridge is attached to the main body of the image forming apparatus and the main body starts driving transmission, the main body driving transmission portion and the photosensitive drum are connected to the cup. The time until ringing is the time when the upstream coaxial gear does not transmit the driving force to the downstream coaxial gear. That is, the transfer roller can be configured not to rotate until the coupling is completed.

  As a result, the transfer roller does not frictionally drive the photoconductive drum, and the coupling between the main body drive transmission unit and the photoconductive drum is completed in an expected time, thereby providing a highly reliable image forming apparatus. be able to.

  Next, according to the second invention of the present application, in addition to the first invention, the time until the drive of the upstream coaxial gear is transmitted to the downstream coaxial gear is ensured more than the time required for the transfer roller to make one round. Therefore, the coupling between the main body drive transmission unit and the photosensitive drum can be connected in that time.

  As a result, the coupling between the main body drive transmission unit and the photosensitive drum is completed in the expected time, so that a highly reliable image forming apparatus can be provided.

  Next, according to the third invention of the present application, in addition to the first to second inventions, the urging member is charged by setting the upstream gear that meshes with the transfer roller driving gear as the downstream coaxial gear. Since the loss of gear transmission efficiency for rotating the transfer roller serving as an opening load can be minimized when released from the above state, the minimum and optimum urging force can be set on the urging member.

  As a result, it is possible to provide a highly reliable image forming apparatus with excellent operation performance.

  Next, according to the fourth invention of the present application, in addition to the first to third inventions, the drive of the upstream coaxial gear is transmitted to the downstream coaxial gear by configuring the biasing member with a torsion coil spring. Rotation angle until it can That is, the time until the coupling between the main body drive transmission unit and the photosensitive drum is connected can be increased.

  As a result, the coupling between the main body drive transmission unit and the photosensitive drum is completed in the expected time, so that a highly reliable image forming apparatus can be provided.

(Example 1)
1 to 4 are perspective views for explaining a drive transmission system and a toner cartridge B of a laser beam printer A which is an image forming apparatus according to a first embodiment of the present invention.

  In the drive transmission system of the laser beam printer A of FIGS. 1 to 4, 1 is a motor as a drive source, 2 is a right drive gear train, 3 is a transport roller, 4 is a left drive gear train, 5 is a transfer roller, 6 is The transfer roller driving gear, 7 is a drum driving gear, 8 is a photosensitive drum inside the toner cartridge B, 9 is a triangular coupling hole provided at the center of the drum driving gear 7, and 10 is a photosensitive drum 8. This is a triangular coupling shaft that is fixed to the end face of the shaft and transmits drive.

  Next, 11 is the most characteristic feature of the present invention, in which two gears are provided coaxially, 11 is an upstream coaxial gear that meshes with the left drive gear train 4, and 12 is a downstream coaxial gear that meshes with the transfer roller drive gear 6. The internal configuration will be described with reference to FIGS.

  In FIGS. 5 to 6, reference numeral 13 denotes a torsion coil spring built between the upstream coaxial gear 11 and the downstream coaxial gear 12, and 14 is provided on the upstream coaxial gear 11 so as to drive to the downstream coaxial gear 12. An upstream stopper portion 15 for transmission is provided inside the downstream coaxial gear 12, and a downstream stopper portion 16 is provided in contact with the upstream stopper portion 14 for driving transmission, and a torsion coil spring 13 is provided on the upstream coaxial gear 11. Reference numeral 17 denotes an upstream spring receiving portion that receives the torsion coil spring 13 provided on the downstream coaxial gear 12.

  Here, in the drive transmission path to the transfer roller 5, the right drive gear train 2 including the drum drive gear 7 is rotated by the activation of the motor 1 which is a drive source. The drive of the right drive gear train 2 is transmitted to the left drive gear train 4 by the conveying roller 3. The left drive gear train 4 is driven up to the upstream coaxial gear 11. The upstream coaxial gear 11 and the downstream coaxial gear 12 are connected with a time difference described later, and the transfer roller 5 rotates when the downstream coaxial gear 12 drives the transfer roller drive gear 6.

  On the other hand, when the toner cartridge B is mounted on the laser beam printer A, the triangular coupling shaft 10 for driving transmission fixed to the end surface of the photosensitive drum 8 of the toner cartridge B exists at the center of the drum driving gear 7. The connection preparation is completed next to the hole 9. When the door C for the toner cartridge B shown in FIG. 4 is closed, the drum driving gear 7 is urged toward the photosensitive drum 8, so that the coupling hole 9 comes into contact with the coupling shaft 10.

  However, since the triangular shape of the coupling hole 9 and the coupling shaft 10 is often out of phase when the toner cartridge B is normally mounted on the main body A, the drum driving gear 7 is rotated by the starting rotation of the motor 1. As a result, the phases of each triangular shape are matched and coupled.

  In other words, the coupling shaft 10 and the coupling hole 9 are coupled when the drum driving gear 7 rotates 1/3 at the worst, that is, until the drum driving gear 7 rotates 1/3 at the worst even when the motor 1 starts to rotate. During this time, the photosensitive drum 8 remains stopped.

[Drive transmission to transfer roller]
Hereinafter, the mechanism operation from the state where the toner cartridge B is attached to the laser beam printer A until the transfer roller 5 is driven will be described.

  In the drive transmission path to the transfer roller 5, the right drive gear train 2 including the drum drive gear 7 is rotated by the start rotation of the motor 1, and the drive of the right drive gear train 2 is transmitted to the left drive gear train 4 by the transport roller 3. Is done. Then, it is driven to the upstream coaxial gear 11 by transmission by the left drive gear train 4.

  Here, the state after the upstream coaxial gear 11 is driven will be described with reference to the left side cross-sectional view of the upstream coaxial gear 11 and the downstream coaxial gear 12 in FIG.

  As shown in FIG. 7A, the torsion coil spring 13 is released from the spring force while being received by the downstream spring receiving portion 17 of the downstream coaxial gear 12 and the upstream spring receiving portion 16 of the upstream coaxial gear 11. Yes.

  When the upstream coaxial gear 11 starts rotating in this state, the transfer roller driving gear 6 that is drivingly transmitted to the transfer roller 5 on which the load of the photosensitive drum 8 is applied and the downstream coaxial that is engaged with the transfer roller driving gear 6 are engaged. The gear 12 does not rotate with an easy force. Therefore, as shown in FIG. 7B, only the upstream stopper portion 14 and the upstream spring receiving portion 16 that are part of the upstream coaxial gear 11 rotate about the rotation axis.

  When the upstream coaxial gear 11 further rotates, the upstream stopper portion 14 and the downstream stopper portion 15 come into contact with each other as shown in FIG. At this time, the torsion coil spring 13 is fully charged.

  When the upstream coaxial gear 11 further rotates, as shown in FIG. 7D, the upstream stopper portion 14 pushes the downstream stopper portion 15 and the downstream coaxial gear 12 starts rotating around the rotation axis. That is, from this state, the upstream coaxial gear 11 and the downstream coaxial gear 12 start to rotate together, the transfer roller drive gear 6 meshed with the downstream coaxial gear 12 also starts rotating, and the transfer roller 5 rotates. .

  In the present embodiment, the specifications of each part are assumed as follows.

-Photosensitive drum diameter: φ30
・ Transfer roller diameter: φ15
Transfer roller drive gear teeth number: 15 teeth Downstream coaxial gear teeth number: 50 teeth Upstream coaxial gear and downstream coaxial gear rotation angle: 180 deg.
From the above specifications, in order for the photosensitive drum and the drum driving gear to be coupled, the coupling shape is a triangle, and therefore, a maximum of 1/3 of the photosensitive drum (= 30π / 3) is required. Assuming that the peripheral speed ratio between the photosensitive drum and the transfer roller is substantially equal, this time corresponds to a time equivalent to 0.7 (= (30π / 3) / 15π) circumference of the transfer roller from the ratio with the transfer roller diameter.

  On the other hand, a rotation angle of 180 deg. Is set until the drive of the upstream coaxial gear is transmitted to the downstream coaxial gear by the mechanism of this embodiment. When this angle is converted into the number of teeth of the downstream coaxial gear, 25 teeth (= 50 teeth × (180 deg./360 deg.)) Are obtained. That is, since the downstream coaxial gear does not rotate for a time corresponding to the rotation of 25 teeth, the transfer roller does not rotate for a time equivalent to about 1.7 (= 15 teeth / 25 teeth) by the gear ratio of the transfer roller driving gear. Become.

  Therefore, the time until the photosensitive drum is coupled and starts to rotate is a time corresponding to 0.7 rotation of the longest transfer roller from the start of the motor, and the time for the transfer roller to start rotating is the transfer roller 1 from the start of the motor. Since this is a time corresponding to 0.7 rotation, and 0.7 <1.7, it can be explained that the rotation of the photosensitive drum is started before the transfer roller starts rotating by the motor activation.

[Release drive to transfer roller]
Next, the state when the toner cartridge B is pulled out from the state shown in FIG. 7D where the toner cartridge B in the laser beam printer A is once driven and stopped is shown in FIG. The side coaxial gear 12 will be described with reference to the left arrow cross-sectional view.

  FIG. 8A shows a state in which the toner cartridge B in the laser beam printer A is once driven. Here, the upstream stopper portion 14 and the downstream stopper portion 15 are in contact with each other, and the torsion coil spring 13 is sufficiently charged with the spring force while being received by the downstream spring receiving portion 17 and the upstream spring receiving portion 16. Yes.

  When the toner cartridge B is pulled out from the main body A in this state, the load on the photosensitive drum 8 that is in contact with the transfer roller 5 is eliminated. On the other hand, since the upstream coaxial gear 11 is always meshed with the left drive gear train 4 and cannot rotate, the downstream spring receiving portion 17 is pressed by the spring force of the sufficiently charged torsion coil spring 13. As a result, as shown in FIG. 8B, the downstream coaxial gear 12 starts rotating, the transfer roller driving gear 6 meshing with the downstream coaxial gear 12 also starts rotating, that is, the transfer roller 5 also rotates idly. .

  The rotation continues as shown in FIG. 8C, and finally the downstream coaxial gear 12 and the transfer roller are driven at the position where the spring force of the torsion coil spring 13 is completely opened as shown in FIG. 8D. The rotation of the gear 6 and the transfer roller 5 is stopped.

Therefore, even when the toner cartridge B is next installed in the main body A, the transfer roller does not rotate until the photosensitive drum is coupled as described above. Two gears are provided, and a torsion coil spring, which is an urging member, is provided between the upstream coaxial gear and the downstream coaxial gear to provide a time difference from the upstream coaxial gear to the downstream coaxial gear. By waiting for the time until the body drum and the drum drive gear are coupled, the transfer roller does not rotate first after the main body drive system is activated, and the photosensitive drum is not rotated by frictional force. The toner cartridge can be reliably coupled to the beam printer main body, and a highly reliable main body can be provided to the user.

  In addition, since the transfer roller is not rotated first after the main body drive system is driven and the photosensitive drum is not rotated by the frictional force, the transfer roller drive gear and the front gear are skipped by overload. This eliminates the possibility, and can provide the user with a low-noise and high-quality main body that does not have image defects due to abnormal sounds or gear scratches.

  In addition, by setting two coaxial gears as the pre-stage gear of the transfer roller drive gear, the mechanism can be configured without increasing the number of gear arrangements and without using extra space, thus providing the user with an inexpensive and compact body. it can.

  In this embodiment, a torsion coil spring is used as the urging member. However, depending on the rotation angle and the size of the upstream coaxial gear and the downstream coaxial gear, a tension coil spring, a compression coil spring, a leaf spring, a spring, or a rubber is used. Even if it is composed of members, the same effect is obtained.

1 is a perspective view illustrating a drive transmission system of an image forming apparatus and a photosensitive drum of a toner cartridge according to a first embodiment of the present invention. 1 is a perspective view illustrating a drive transmission system of an image forming apparatus according to a first embodiment of the present invention. 1 is a perspective view illustrating a drive transmission system and a toner cartridge of an image forming apparatus according to a first embodiment of the present invention. 1 is a perspective view illustrating an image forming apparatus and a toner cartridge according to a first exemplary embodiment of the present invention. It is a perspective view explaining the inside of the coaxial upstream coaxial gear and downstream coaxial gear which concern on 1st Example of this invention. It is sectional drawing explaining the left side drive gear train which concerns on 1st Example of this invention. It is sectional drawing explaining the internal operation | movement at the time of the drive transmission of the coaxial upstream coaxial gear and downstream coaxial gear which concern on 1st Example of this invention. It is sectional drawing explaining the internal operation | movement at the time of drive cancellation | release of the coaxial upstream coaxial gear and downstream coaxial gear which concern on 1st Example of this invention. FIG. 7 is a perspective view of a drive transmission system of an image forming apparatus for explaining a conventional example before mounting a toner cartridge. FIG. 10 is a perspective view of an image forming apparatus drive transmission system for explaining a conventional example after the toner cartridge is mounted.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Motor 2 Right side drive gear train 3 Conveyance roller 4 Left side drive gear train 5 Transfer roller 6 Transfer roller drive gear 7 Drum drive gear 8 Photosensitive drum 9 Coupling hole 10 Coupling shaft 11 Upstream coaxial gear 12 Downstream coaxial gear 13 Torsion coil spring 14 Upstream stopper 15 Downstream stopper 16 Upstream spring receiver 17 Downstream spring receiver A Laser beam printer body B Toner cartridge C Cartridge door

Claims (4)

A removable toner cartridge is mounted on the main body of the image forming apparatus, and a drive transmission unit of the main body of the image forming apparatus that drives the photosensitive drum of the toner cartridge is configured by a coupling. In the image forming apparatus in which the roller drive is transmitted from the drive system of the image forming apparatus main body without passing through the drive transmission system of the toner cartridge,
A plurality of gears are coaxially provided upstream of the drive transmission system of the transfer roller drive gear, and the upstream coaxial gear of the plurality of gears is connected to the drive transmission gear from the drive source, and the downstream coaxial gear is driven to the transfer roller. Connected to the transmission gear, the upstream coaxial gear and the downstream coaxial gear have a stopper portion that can transmit the drive rotation by connecting each of them, and urged between the upstream coaxial gear and the downstream coaxial gear When the transfer roller is unloaded, the urging member urges the upstream coaxial gear and the downstream coaxial gear in a direction to separate the drive transmission, and the transfer roller is loaded. In the image forming apparatus, the urging member is charged when the drive is transmitted to the upstream coaxial gear, and the drive can be transmitted when the stopper portions of the upstream coaxial gear and the downstream coaxial gear come into contact with each other.   The number of teeth intervening in the rotation angle from when the stopper portions of the upstream coaxial gear and the downstream coaxial gear are separated by the urging member until the stopper portions abut against each other by driving the body is the transfer number The image forming apparatus according to claim 1, wherein the number of teeth is equal to or greater than the total number of teeth of the roller drive gear.   The image forming apparatus according to claim 1, wherein the downstream coaxial gear is a front gear that meshes with the transfer roller driving gear.   The image forming apparatus according to claim 1, wherein the biasing member is a torsion coil spring.

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