JPH09311516A - Image forming device - Google Patents

Abstract

(57) Abstract: An image forming defect caused by deformation of an image carrier is prevented. SOLUTION: A thin-walled cylindrical image carrier 50 on which an image is formed on the outer periphery, and the image on the image carrier 50 are recorded on a recording medium P.
Transfer roller 53 disposed in contact with the image carrier 50 for transferring the image to the image carrier 50, a first gear 570 coupled to the image carrier 50 for transmitting the rotation to the image carrier 50, and the image carrier 50.
Image carrier 50 for transmitting the rotation from the transfer roller 53 to the transfer roller 53.
And a pair of second gears 564 and 581 respectively connected to the transfer roller 53 and an image forming apparatus such as a laser beam printer, the first gear 570 and the second gear 5
64 and 581 are arranged on the same side in the axial direction of the image carrier 50.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a laser beam printer, a facsimile and a copying machine.

[0002]

2. Description of the Related Art In an image forming apparatus of this type, an electrostatic latent image is formed on the surface of a photosensitive drum as an image carrier, and the image is developed with a developer to be converted into a visible image. The image is transferred to a recording medium such as a sheet using a transfer roller arranged so as to be in contact with the photosensitive drum. In this image forming process, it is necessary to rotate the photosensitive drum and the transfer roller in opposite directions around their respective axes. Therefore, a gear for transmitting rotation from a drive source provided in the image forming apparatus is attached to each of the photosensitive drum and the transfer roller.

[0003]

In the above-mentioned image forming apparatus, it is desirable that the mechanism for transmitting the rotation from the drive source of the apparatus to each gear of the photosensitive drum and the transfer roller be as simple as possible. In view of the fact that and are arranged adjacent to each other, it is appropriate to connect them with a pair of gears and transmit the rotation between the photosensitive drum and the transfer roller. As one mode of such a rotating mechanism, for example, a rotation is transmitted from a drive source in the image forming apparatus to a gear on one end side of the photosensitive drum, and the rotation is transmitted to a pair of gears provided on the opposite side of the drive drum. It is conceivable to transmit to the transfer roller at.

However, since the photosensitive drum is generally formed in a thin cylindrical shape, in the above structure, the photosensitive drum receives a rotational torque and is twisted and deformed. As a result, the image on the photosensitive drum is distorted and an image formation failure occurs. May invite.
In order to rotate the photosensitive drum and the gear integrally, it is necessary to connect the photosensitive drum and the gear to each other by using a fixing means such as press fitting. However, if such fixing is performed at both ends of the image carrier. However, there is a high possibility that the image carrier will be distorted to cause uneven rotation. Also, it takes time to attach the gears.

An object of the present invention is to provide an image forming apparatus capable of driving an image carrier and a transfer roller with a simple mechanism and preventing defective image formation due to deformation of the image carrier.

[0006]

Hereinafter, the present invention will be described with reference to the drawings showing embodiments of the present invention. However, the present invention is not limited to the illustrated embodiment.

According to the first aspect of the present invention, a thin-walled cylindrical image carrier 50 on which an image is formed, and an image carrier 50 which is in contact with the image carrier 50 for transferring the image on the image carrier 50 to the recording medium P. And the transfer roller 53, and a first gear 570 connected to the image carrier 50 for transmitting rotation to the image carrier 50.
And a pair of second gears 564 and 581 respectively coupled to the image carrier 50 and the transfer roller 53 for transmitting rotation from the image carrier 50 to the transfer roller 53. The first gear 570 and the second gear Reference numerals 564 and 581 denote the image carrier 50.
The above-mentioned object is achieved by the image forming apparatus arranged on the same side in the axial direction of.

According to the present invention, when the rotation is transmitted from the drive source of the image forming apparatus to the first gear 570, the first gear 5
The image carrier 50 rotates with the rotation of 70, and at the same time, the rotation is transmitted to the transfer roller 53 via the second gears 564 and 581. The first gear 570 and the second gear 564,
Since 581 is arranged on the same side in the axial direction of the image carrier 50, the first gear 570 does not have to interpose the image carrier 50.
The rotation can be transmitted from the second gear 564 to the second gear 581. Therefore, the twist of the image carrier 50 can be prevented. Image carrier 5
It is sufficient to mount the gears 570 and 564 only on one end side of 0, and it is not necessary to fix the gears on the opposite side, so that the deformation of the image carrier 50 can be suppressed.

According to a second aspect of the invention, in the image forming apparatus according to the first aspect, the support shaft 560 for supporting the image carrier 50.
And a pair of support members 561 and 562 mounted between both ends of the image carrier 50 and the support shaft 560 to hold the image carrier 50 coaxially with the support shaft 560. And
One support member 561 is integrally rotatably attached to one end of the image carrier 50, the second gear 564 is integrally attached to the one support member 561, and the first gear 570 is attached.
Is provided so as to be separable from the one support member 561 and engageable with the one support member 561 in the circumferential direction.

According to the present invention, one of the second gears 564 is
The support member 561 provided with is attached to the image carrier 50,
The rotation can be transmitted from the first gear 570 to the image carrier 50 and the transfer roller 53 by merely engaging the first gear 570 with the support member 561 in the circumferential direction. Since the support member 561 provided with the second gear 564 and the first gear 570 are provided separately, the second gear 564 and the first gear 5 are provided.
70 can be manufactured accurately.

According to a third aspect of the invention, in the image forming apparatus according to the second aspect, the support shaft 560 is made of a conductive material, and the inner periphery of the image carrier 50 is made of a conductive material. The rotated transmission member 563 is mounted so as to bite into the inner peripheral surface of the image carrier 50 and to be in contact with the support shaft 560. The rotation transmission member 563 and the one support member 561 engage in the circumferential direction. It is what

According to the present invention, the one support member 561 and the image carrier 50 are integrally rotatably connected to each other via the rotation transmission member 563, and at the same time, the image carrier is supported via the support shaft 560 and the rotation transmission member 563. The body 50 can be set to a desired potential.

In the invention of claim 4, at least one of the first gear 570 and the pair of second gears 564 and 581 is a helical gear. Therefore, the first gear 570
Necessary for narrowing the gear width while suppressing a decrease in the torque that can be transmitted from the transfer roller 53 to the transfer roller 53, thereby arranging both the first gear 570 and the second gears 564 and 581 on one axial side of the image carrier 50. Space can be kept small.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 4 and 5 show the overall configuration of a laser beam printer 1 as an embodiment of the present invention. In the following, the arrow F direction in FIG. 4 corresponds to the front of the laser beam printer 1, and the arrow U direction corresponds to the top. The illustrated laser beam printer 1 includes a main body case 2 and a paper feed unit 3 for feeding a paper P.
A laser scanner unit 4 for forming an electrostatic latent image, a process unit 5 for converting the electrostatic latent image into a visible image and transferring it to the paper P, and fixing the image transferred on the paper P. The fixing unit 6 and the paper discharge tray 7 on which the paper P after printing is stacked are provided.

As is apparent from FIG. 5, the main body case 2
Includes a case frame 20 and an upper cover 21 mounted on the upper side of the case frame 20. The upper cover 21 is connected to the case frame 20 in a vertically openable and closable state around a connecting portion (not shown) provided on the rear end side (the left end side in FIG. 4). Inside the left side of the case frame 20, a drive unit 8 incorporating a motor and a gear train (not shown) is inserted from below the case frame 20 into a storage recess and fixed. At this time, it meshes with a drive gear train (not shown) provided in the main body case 2.

As shown in FIGS. 4 and 5, the paper feeding unit 3 includes a paper feeding cassette 30 which is detachably attached to the main body case 2. Paper P is placed in the paper cassette 30.
A push-up plate 31 on which is loaded is provided. The paper P stacked on the push-up plate 31 is pressed against the paper feed roller 33 and the paper pressing collar 34 by the force of the spring 32. In this state, the paper feed roller 33 rotates in the arrow direction of FIG. It is sent out from the paper feed cassette 30. A separation wall 35 is provided in front of the paper feed cassette 30. The inclination of the separation wall 35 and the force of the spring 36 that presses the separation wall 35 toward the paper feed roller 33 promote the separation of the paper sheets P from each other, and as a result, the uppermost paper sheet P in the paper feed cassette 30 is separated. The sheet P is separated from the sheet P and is sent to the downstream side by the registration rollers 37 and 38. Note that the movement path of the sheet P to reach the sheet discharge tray 7 is indicated by a chain line PP in the figure.

The laser scanner unit 4 is attached to the bottom of the body case 2. A laser light generator 40 is provided inside the laser scanner unit 4, and the laser light emitted from the laser generator 40 is a polygon mirror 41, a lens 42, and a mirror 4 as shown by arrows in FIG.
3, through the lens 44 and the mirror 45, it is guided onto the photosensitive drum 50 of the process unit 5. The polygon mirror 41 is rotationally driven around its vertical axis in synchronization with the emission of the laser light, and the laser light is scanned in the axial direction of the photosensitive drum 50 (the direction orthogonal to the paper surface of FIG. 4) along with the rotation. .

The process unit 5 is accommodated in the main body case 2 so as to cover the upper side of the laser scanner unit 4. The process unit 5 can be attached to and detached from the main body case 2 by opening and closing the upper cover 21. Inside the case 5a of the process unit 5, a photosensitive drum 50, a charger 51, a developing device 52, and a transfer roller 53 are provided. The photosensitive drum 50 and the transfer roller 53 are rotationally driven in the directions of the arrows in the drawing around their respective axes by the driving force supplied from the driving unit 8 (see FIG. 5) described above. The configuration for rotating these will be described later. The charger 51 causes corona discharge to charge the photosensitive drum 50. The outer periphery of the charged photosensitive drum 50 is irradiated with the laser light from the laser scanner unit 4 described above, and a potential difference is generated between the irradiated portion and the non-irradiated portion to form an electrostatic latent image.

The developing device 52 supplies the toner 521 contained in the toner box 520 to the outer peripheral side of the photosensitive drum 50 via the supply roller 522 and the developing roller 523. The supplied toner 521 adheres to the photosensitive drum 50 according to the charged state of the photosensitive drum 50, thereby forming a visible image corresponding to the electrostatic latent image on the photosensitive drum 50 (development).
Is done.

The transfer roller 53 is arranged in contact with the upper end of the photosensitive drum 50, and the paper P is guided to these contact positions. A constant electric field is formed between the photosensitive drum 50 and the transfer roller 53, and the electric field causes the photosensitive drum 5 to move.
The toner image on 0 is transferred to the paper P. After the transfer, the cleaning roller 54 removes the residual toner on the photosensitive drum 50 in preparation for the formation of the next electrostatic latent image.
At 5, the residual charge on the photosensitive drum 50 is removed. In addition,
The residual toner transferred to the cleaning roller 54 is returned to the photosensitive drum 50 at an appropriate timing (timing that does not interfere with the formation of an electrostatic latent image, etc.), and the returned toner is transferred to the developing device 52 via the developing roller 523. Will be collected.

The fixing unit 6 is arranged adjacent to the process unit 5 on the downstream side in the conveying direction of the paper P.
The fixing unit 6 is provided with a pair of rollers 60 and 61. The paper P on which the toner image is transferred is these rollers 6
The sheet P is guided and pressed between 0 and 61, and in that state, the sheet P is heated by a heating means (not shown) such as a halogen lamp provided on one roller (for example, 60). The toner image on the paper P is fixed by this pressing and heating. The paper P after fixing is discharged onto the paper discharge tray 7 by the pair of discharge rollers 62, 62. The discharge tray 7 is opened and closed centering on the connecting portions 70 provided at both ends of the main body 20.
Is connected to the front side of the (see FIG. 5).

Next, referring to FIGS. 1 to 3, the photosensitive drum 5
Details of 0 and the transfer roller 53 will be described. As shown in FIG. 2, the photosensitive drum 50 is formed by covering the outer circumference of a thin-walled cylindrical sleeve 500 made of a conductive material with a photosensitive layer 501. For the sleeve 500, for example, an aluminum tube having a thickness of about 0.8 mm is used.
Various types of organic photoconductors are used for the photosensitive layer 501, but for example, a polycarbonate in which a photoconductive resin is dispersed is preferably used. The photosensitive drum 50 has a support mechanism 56.
Is supported by the case 5a of the process unit 5 (see FIGS. 4 and 5).

The support mechanism 56 includes a support shaft 560 which is inserted through the center of the photosensitive drum 50, and a first flange 561 and a second flange 562 which are supported by the support shaft 560 and are fitted to the shaft ends of the photosensitive drum 50, respectively. Have and. The support shaft 560 is made of a conductive material, and is supported by the case 5a of the process unit 5 (see FIGS. 4 and 5) at both ends thereof. As shown in FIG. 3, a leaf spring 563 is provided at the portion where the first flange 561 is inserted into the photosensitive drum 50. The leaf drum 563 has a photosensitive drum 5
A plurality of claw portions 563a that bite into the inner peripheral surface of 0 are provided,
These claw portions 563a and the concave portion 56 of the first flange 561.
1a meshes with the first flange 561 and the photosensitive drum 5
0 and 0 can rotate together. The leaf spring 563 is made of a conductive material, and the support shaft 56 is provided on the inner peripheral side thereof.
A conducting portion 563b that contacts 0 is provided. Support shaft 560 when the process unit 5 is attached to the main body case 2
Comes into contact with a ground electrode (not shown) in the body case 2, whereby the photosensitive drum 50 causes the leaf spring 563 and the support shaft 560 to move.
To ground.

A transmission gear 564 for transmitting rotation to the transfer roller 53 side is integrally formed at a portion of the first flange 561 protruding from the photosensitive drum 50. Also, the first
A drum gear 57 is provided outside the flange 561 in the axial direction.
0 is provided. The drum gear 570 is supported by the support shaft 560, and the engaging protrusion 561b provided on the first flange 561 is fitted into the through hole 570a. This allows
The drum gear 570 and the first flange 561 can rotate integrally. When the process unit 5 is attached to the main body case 2, the drum gear 570 meshes with the drum drive gear 200 provided in the main body case 2 (see FIG. 1).
The drum drive gear 200 includes the drive unit 8 shown in FIG.
The rotation is transmitted from the drum gear 570 to the photosensitive drum 50 via the first flange 561 and the leaf spring 563.

The second flange 562 is mounted between the inner circumference of the photosensitive drum 50 and the support shaft 560 to hold the photosensitive drum 50 and the support shaft 560 coaxially. Since the transmission gear 560 and the drum gear 570 are provided on the first flange 561 side, it is not necessary to provide a gear or the like on the second flange 562 side. Therefore, a plate is not provided between the second flange 562 and the photosensitive drum 50. No rotation transmission means such as the spring 563 is provided. The flanges 561 and 562 and the drum gear 570 may be rotatable with respect to the support shaft 560. The flanges 561 and 562 and the drum gear 570 are made of resin, for example.

The transfer roller 53 is made of a conductive foam elastic material, for example, a foam rubber made of silicon or urethane. As shown in FIGS. 1 and 3, a support shaft 580 is rotatably fixed to the center of the transfer roller 53, and the support shaft 580 is rotatably supported by the case 5 a of the process unit 5. Support shaft 580
A transmission gear 581 is fixed to the shaft end of the so as to rotate integrally. When the transmission gear 581 meshes with the transmission gear 564 on the photosensitive drum 50 side, the transfer roller 5
3 rotates around the support shaft 580 in the opposite direction to the photosensitive drum 50 in synchronization with the photosensitive drum 50.

As is apparent from FIGS. 1 and 3, the drum drive gear 200, the drum gear 570, and the pair of transmission gears 564 and 581 are helical gears. Although at least one set of these may be replaced with spur gears, when a helical gear is used, a large torque can be transmitted while the gear width is narrower than when a spur gear is used. The rotation speeds of the photosensitive drum 50 and the transfer roller 53 can be appropriately adjusted by the number of teeth of the gears 200, 570, 564, 581. Desirably, the peripheral speed on the outer peripheral surface of the photosensitive drum 50 is on the outer peripheral surface of the transfer roller 53. Set to be slightly faster than the peripheral speed of.

In the above embodiment, the transmission gear 56 is assumed.
If 4, 581 are provided on the second flange 562 side, the rotation transmitted to the drum gear 570 is transmitted to the transfer roller 53 side via the photosensitive drum 50, and in that case, the photosensitive drum 50 is twisted to form an image. Formation failure occurs. However, since the drum gear 570 and the transmission gears 564 and 581 are arranged on the same side in the axial direction of the photosensitive drum 50, the transfer roller from the drum gear 570 via the transmission gears 564 and 581 and the shaft 580 without passing through the photosensitive drum 50. The rotation is transmitted to 53. Therefore, there is no possibility that the photosensitive drum 50 will be twisted. Also, as mentioned above,
Since it is not necessary to engage the second flange 562 with the photosensitive drum 50 in the circumferential direction via the rotation transmitting member such as the leaf spring 563, the number of parts is reduced, and the labor for mounting the second flange 562 is also reduced. Therefore, the cost can be reduced. Since the first flange 561 and the second flange 562 are provided separately, the transmission gear 564 and the drum gear 57
0 can be manufactured with high precision.

In the above embodiment, the paper P is the recording medium, the photosensitive drum 50 is the image carrier, and the drum gear 57.
0 is the first gear, and transmission gears 564 and 581 are the pair of second gears.
The gear, the leaf spring 563 correspond to the rotation transmitting member, the first flange 561 and the second flange 562 correspond to a pair of supporting members, and the first flange 561 corresponds to one supporting member. The first flange 561 may be press-fitted into the photosensitive drum 50 without being mounted via the plate spring 563. Drum gear 5
The 70 and the first flange 561 can be engaged with each other in the circumferential direction by using various engaging members such as a key. The shaft end of the support shaft 560 may be formed in a polygonal shape in cross section, and the drum gear 570 may be fitted therein.

The present invention is not limited to the one in which the transfer roller is arranged directly above the photosensitive drum, but can be applied to image forming apparatuses of various configurations.

[0031]

As described above, according to the image forming apparatus of the present invention, since the rotation can be transmitted to the transfer roller without passing through the image carrier, the torsional deformation of the image carrier due to the rotational torque can be prevented. . Further, since it suffices to connect the gear to only one end side of the image carrier, the deformation of the image carrier due to the fixing of the gear can be suppressed as compared with the case where the gear is connected to both ends of the image carrier. Therefore, it is possible to prevent defective image formation due to the deformation of the image carrier. Compared with the case where the gears are fixed on both sides of the image carrier, the labor required for fixing the gears is reduced, so that the cost reduction can be achieved.

In addition, in the second aspect of the present invention, the support member provided with the second gear and the first gear are provided separately, so that the second gear and the first gear can be manufactured with high precision. it can. According to the third aspect of the invention, members are shared by the mechanism for transmitting the rotation to the image carrier and the mechanism for setting the potential of the image carrier, and the number of parts can be reduced to achieve cost reduction. According to the invention of claim 4, the width of each gear is reduced while suppressing the reduction of the torque that can be transmitted from the first gear to the transfer roller, whereby the first gear and the second gear are provided on one side in the axial direction of the image carrier. It can contribute to downsizing of the device by suppressing the space required for arranging both of them.

[Brief description of drawings]

FIG. 1 is an enlarged view showing a periphery of a photosensitive drum and a transfer roller of a laser beam printer according to an embodiment of the present invention.

FIG. 2 is an axial sectional view of the photosensitive drum of FIG. 1 and a structure for supporting the photosensitive drum.

FIG. 3 is an exploded perspective view of the configuration shown in FIG.

FIG. 4 is a sectional view of a laser beam printer according to an embodiment of the present invention.

FIG. 5 is an exploded perspective view of the laser beam printer according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Laser beam printer 2 ... Main body case 3 ... Paper feeding unit 4 ... Laser scanner unit 5 ... Process unit 6 ... Fixing unit 7 ... Paper ejection tray 8 ... Driving unit 50 ... Photosensitive drum (image carrier) 53 ... Transfer roller 560 ... Support shaft 561 ... First flange (support member) 562 ... Second flange (support member) 563 ... Leaf spring (rotation transmission member) 564, 581 ... Transmission gear (second gear) 570 ... Drum gear (first gear) P ... Paper (recording medium)

Claims (4)

[Claims] 1. A thin-walled cylindrical image carrier having an image formed on its outer periphery, and a transfer roller arranged in contact with the image carrier for transferring the image on the image carrier to a recording medium. A first gear connected to the image carrier for transmitting rotation to the image carrier; and a first gear connected to the image carrier and the transfer roller for transmitting rotation from the image carrier to the transfer roller. And a pair of second gears, wherein the first gear and the second gear are arranged on the same side in the axial direction of the image carrier. 2. A support shaft that supports the image carrier, and a pair of supports that are mounted between both ends of the image carrier and the support shaft to hold the image carrier coaxially with the support shaft. A member, one supporting member is integrally rotatably attached to one end of the image carrier, the second gear is integrally attached to the one supporting member, and the first gear is the one supporting member. 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is provided so as to be separable from the supporting member and to be engageable with the one supporting member in the circumferential direction. 3. The inner peripheral surface of the image carrier, wherein the support shaft is made of a conductive material, and the rotation transmitting member made of a conductive material is provided on the inner circumference of the image carrier. It is installed so as to bite into and contact the support shaft,
The image forming apparatus according to claim 2, wherein the rotation transmitting member and the one supporting member are engaged with each other in the circumferential direction. 4. The image forming apparatus according to claim 1, wherein at least one of the first gear and the pair of second gears is a helical gear.