JP2006194946A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus in which the length of an intermediate transfer belt is satisfactorily secured while reducing the size of the whole apparatus. <P>SOLUTION: The image forming apparatus is provided with: an exposure apparatus arranged in the lower part of the apparatus; also, a photoreceptor drum 12, a rotary developing unit 16; and the intermediate transfer belt 14 for transferring a toner image formed on the photoreceptor drum 12. The intermediate transfer belt 14 passes in between the photoreceptor drum 12 and an ejection tray on the way from a secondary transfer part 22 to a primary transfer part 20, further, extends to the lower side of the rotation center of the rotary developing unit 16 on the way from the primary transfer part 20 to the secondary transfer part 22, and the end closest to the rotary developing unit of the intermediate transfer belt 14 passes through the side closer to the rotary developing unit 16 than the rotation center of the photoreceptor drum 12. Then, a space between the photoreceptor drum 12 and the ejection tray, and also, a space between the paper P carrying path and a waste toner container 24 are used as a gap for letting the intermediate transfer belt 14 through, then, the length of the intermediate transfer belt 14 is secured without making the whole apparatus large in size. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that transfers a toner image on a photosensitive drum onto a sheet using an intermediate transfer belt.

Conventionally, there has been proposed an image forming apparatus in which an intermediate transfer belt is wrapped on a photosensitive drum and the primary transfer position to the secondary transfer position are arranged close to each other. However, when the belt length is increased, the belt must be stretched away from the secondary transfer position, and the apparatus size must be increased.

  For example, in the case of the image forming apparatus 100 arranged as shown in FIGS. 5 and 6, the primary transfer position 110 for transferring the toner image from the photosensitive drum 102 to the intermediate transfer belt 104, and the toner image from the intermediate transfer belt 104 to the sheet. Since the position of the secondary transfer position 112 to be transferred is close, when a thick transfer material such as thick paper or OHP is passed through the secondary transfer position 112, the impact transmitted to the intermediate transfer belt 104 by that thickness is easy. To the primary transfer position 110. For this reason, there is a possibility that the image quality may be affected, such as blurring in the primary transfer at the timing when the sheet is conveyed to the secondary transfer position 112.

  In addition, the intermediate transfer belt 104 forms a primary transfer position 110 between the intermediate transfer belt 104 and the photosensitive drum 102 so as to wrap around the photosensitive drum 102. However, the angle when the intermediate transfer belt 104 is separated from the photosensitive drum 102 is an acute angle. It is necessary to define the transport position of the intermediate transfer belt 104 by pressing with the wrap-out roll 114. Further, in order to increase the angle of the primary transfer position 110 formed by the photosensitive drum 102 and the intermediate transfer belt 104 on the photosensitive drum 102, the arrangement of FIG. The angle at the time of separation becomes an acute angle.

  Alternatively, a fixing device is provided above the device for the purpose of eliminating adverse effects on the primary transfer due to the heat of the fixing device and downsizing the device, and the drum developing device and the fixing device are arranged at a position separated by the length of the transfer belt. An image forming apparatus having a configuration has been proposed (see, for example, Patent Document 1).

  However, in the above configuration, as shown in FIG. 7, priority is given to separating the fixing unit 208 and the drum developing unit 206 over the downsizing of the apparatus 200, so the intermediate transfer belt 204 is substantially omitted from the photosensitive drum 202. While the primary transfer position 210 and the secondary transfer position 212 can be arranged apart from each other by spreading in the horizontal direction, the installation area of the entire apparatus 200 cannot be reduced.

  Alternatively, the rotary developing unit 306, the photosensitive drum 302, and the intermediate transfer belt 304 are arranged side by side in the horizontal direction, the primary transfer position 310 and the secondary transfer position 312 are arranged apart from each other, and the intermediate transfer belt 304 is placed in the intermediate transfer unit 316. An image forming apparatus having a configuration that can be integrally removed has been proposed (see, for example, Patent Document 2).

However, in the above configuration, as shown in FIG. 8, since the rotary developing device 306, the photosensitive drum 302, and the intermediate transfer belt 304 are arranged side by side in the horizontal direction, the overall size of the entire apparatus increases, and the intermediate transfer unit 316 is removed. When placed outside the machine, the shape is not self-supporting, so there are problems such as the operator holding it until the end of work or preparing a dedicated stand.
JP 2000-298382 A JP 2000-194203 A

  In view of the above facts, an object of the present invention is to provide an image forming apparatus in which the length of the intermediate transfer belt is sufficiently secured while suppressing the size of the entire apparatus.

The image forming apparatus according to claim 1, wherein a photosensitive drum on which an electrostatic latent image is formed by image exposure;
A rotary developing unit that develops the electrostatic latent image on the photosensitive drum with toner, an intermediate transfer belt that transfers the toner image on the photosensitive drum to a sheet as a transfer material, and a rotary developing unit A sheet accommodating portion that accommodates the sheet; a primary transfer portion that transfers the toner image from the photosensitive drum to the intermediate transfer belt; and a secondary transfer that transfers the toner image from the intermediate transfer belt to the sheet. In the image forming apparatus, comprising: a sheet conveying path provided substantially perpendicularly from the sheet storage unit to the secondary transfer unit; and a discharge tray for collecting the sheets discharged after image formation. The transfer belt passes between the photosensitive drum and the discharge tray between the secondary transfer portion and the primary transfer portion, and the intermediate transfer belt passes from the primary transfer portion to the secondary transfer portion. The end of the intermediate transfer belt that is closest to the rotary developer is extended to the lower side of the rotary developer than the center of rotation of the photosensitive drum. It is characterized by passing through.

  In the invention with the above configuration, the intermediate transfer belt is spread between the paper discharge tray and the photosensitive drum on the upper side and the lower side of the rotary developing unit on the lower side. In addition, the length of the intermediate transfer belt can be secured without increasing the size of the entire apparatus, and the distance between the primary transfer portion and the secondary transfer portion can be increased, so that even if thick paper is carried in, the impact is applied to the primary transfer portion. It is difficult to communicate and can prevent image quality deterioration.

  The image forming apparatus according to claim 2 is characterized in that the intermediate transfer belt is wrapped on the photosensitive drum to form the primary transfer portion.

  In the invention with the above configuration, the contact length between the intermediate transfer belt and the photosensitive drum can be increased, so that the toner image can be reliably transferred.

  According to a third aspect of the present invention, the intermediate transfer belt is separated from the photosensitive drum in a substantially tangential direction on the downstream side of the photosensitive drum in the primary transfer portion.

  In the invention with the above configuration, when the intermediate transfer belt is separated from the photosensitive drum, an acute angle does not occur, and a wrap-out roll for pressing the intermediate transfer belt against the photosensitive drum can be eliminated.

  The image forming apparatus according to claim 4, wherein an exposure device is provided below the photosensitive drum and performs image exposure on the photosensitive drum, and a waste toner container that stores waste toner collected from the photosensitive drum. The waste toner container is disposed between the intermediate transfer belt and the optical path of the exposure device, and two sides of the outer shape of the waste toner container are formed along the intermediate transfer belt and the optical path, respectively. It is characterized by.

  In the invention with the above configuration, the waste toner container can be enlarged because the outer mold of the waste toner container is configured along the intermediate transfer belt and the optical path of the exposure apparatus.

  6. The image forming apparatus according to claim 5, further comprising an exchange unit that accommodates the waste toner container and the intermediate transfer belt and is replaceable from a main body of the image forming apparatus, wherein the bottom surface of the waste toner container is substantially horizontal and the exchange is performed. It is characterized by being substantially parallel to the bottom surface of the unit.

  In the invention with the above configuration, since the bottom surface of the replacement unit is substantially horizontal and substantially parallel to the bottom surface of the waste toner container, the replacement unit can be mounted on the apparatus while being placed on the desk or on the floor, so that waste toner leaks. Accidents can be prevented.

  The image forming apparatus according to claim 6, further comprising: a cleaning device that forms a linear portion of the intermediate transfer belt above the photosensitive drum and cleans the intermediate transfer belt so as to face the linear portion. It is characterized by.

  In the invention having the above-described configuration, the height of the entire apparatus can be suppressed while securing the belt cleaning area by providing the cleaning device facing the linear portion of the intermediate transfer belt formed above the photosensitive drum. it can.

  According to a seventh aspect of the present invention, there is provided an image forming apparatus including a detecting unit that detects a toner image on the intermediate transfer belt in the vicinity of the lowermost end in the conveyance path of the intermediate transfer belt.

  In the invention with the above configuration, since the distance from the secondary transfer portion to the detection means can be increased, even if a cardboard is carried in, it is difficult for the impact to be transmitted to the detection means, and image quality deterioration can be prevented.

  9. The image forming apparatus according to claim 8, wherein a linear portion of the intermediate transfer belt is formed above the photosensitive drum, and a toner image on the intermediate transfer belt is detected so as to face the linear portion. Is provided.

  In the invention with the above configuration, since the distance from the secondary transfer portion to the detection means can be increased, even if a cardboard is carried in, it is difficult for the impact to be transmitted to the detection means, and image quality deterioration can be prevented.

  The image forming apparatus according to claim 9, wherein the intermediate transfer belt is extended to a lower side than a lower end position of the rotary developer between the primary transfer portion and the secondary transfer portion.

  In the invention with the above configuration, the effect of claim 1 can be further enhanced.

  Since the present invention is configured as described above, an image forming apparatus in which the length of the intermediate transfer belt is sufficiently secured while suppressing the size of the entire apparatus can be obtained.

  FIG. 1 shows an image forming apparatus according to a first embodiment of the present invention.

  As shown in FIG. 1, the image forming apparatus 10 includes a photosensitive drum 12 on the surface of which an electrostatic latent image is formed by performing image exposure by an exposure apparatus 28 provided substantially horizontally below the apparatus. A rotary developer 16 that develops the electrostatic latent image on the body drum 12 with toner and an intermediate transfer belt 14 that transfers the toner image on the photoreceptor drum 12 to a sheet P that is a transfer material.

  A sheet storage unit 28 for storing the sheet P is provided under the rotary developing unit 16, and the toner image is transferred from the intermediate transfer belt 14 to the sheet P transported along the transport path provided substantially vertically.

  The intermediate transfer belt 14 includes a primary transfer unit 20 that transfers a toner image from the photosensitive drum 12 to the intermediate transfer belt 14, and a secondary transfer unit 22 that transfers the toner image from the intermediate transfer belt 14 to the sheet P. The toner images are sequentially transferred from the photosensitive drum 12 to the sheet P via the transfer unit. After the image formation, the sheet P is discharged to a discharge tray 26 provided on the upper part of the image forming apparatus 10 and accumulated. The toner that has not been transferred from the photosensitive drum 12 to the intermediate transfer member 14 is collected in a waste toner container 24 provided immediately below the photosensitive drum 12.

  As shown in FIGS. 1 and 2, the intermediate transfer belt 14 passes between the photosensitive drum 12 and the discharge tray 26 between the secondary transfer portion 22 and the primary transfer portion 20. As a result, the space between the photosensitive drum 12 and the discharge tray 26, which has conventionally been a dead space, can be used as a gap for passing the intermediate transfer belt 14, and the intermediate transfer belt 14 can be formed without increasing the size of the entire apparatus. Length can be secured.

  Further, the intermediate transfer belt 14 extends between the primary transfer portion 20 and the secondary transfer portion 22 below the rotation center of the rotary developing device 16, and the end of the intermediate transfer belt 14 closest to the rotary developing device is photosensitive. It passes through the rotary developer 16 side of the center of rotation of the body drum 12. As a result, the space between the conveyance path of the sheet P and the waste toner container 24 can be used as a gap for passing the intermediate transfer belt 14, and the length of the intermediate transfer belt 14 can be secured without increasing the size of the entire apparatus. .

  That is, while the intermediate transfer belt 14 is partially extended from the photosensitive drum 12 toward the rotary developing device 16, most of the primary transfer portion 20 including the secondary transfer portion 22 is extended away from the rotary developing device 16 and downward. As a result, it is possible to effectively utilize a space that has not been used conventionally, and to secure the length of the intermediate transfer belt 14 without increasing the size of the entire apparatus.

  Further, the intermediate transfer belt 14 is wrapped around the photosensitive drum 12 to form a primary transfer portion 20. As a result, the contact length between the intermediate transfer belt 14 and the photosensitive drum 12 can be increased, so that the toner image can be reliably transferred. At this time, the intermediate transfer belt 14 is separated in the substantially tangential direction from the photosensitive drum 12 on the downstream side in the conveyance direction of the photosensitive drum 12 in the primary transfer unit 20. Accordingly, the angle when the intermediate transfer belt 14 is separated from the photosensitive drum 12 does not become an acute angle, and a wrap-out roll (114 in FIG. 6) for pressing the intermediate transfer belt 14 against the photosensitive drum 12 is not necessary. Can do.

  As shown in FIG. 1, the waste toner container 24 is disposed between the intermediate transfer belt 14 and the optical path L of the exposure device 26, and two sides of the outer shape of the waste toner container 24 are the intermediate transfer belt 14 and the optical path L, respectively. And is formed along. Thus, the size of the waste toner container 24 can be maximized by maximizing the outer mold of the waste toner container 24 along the intermediate transfer belt 14 and the optical path L of the exposure device 26.

  Further, a cleaning device 32 is provided that forms a linear portion of the intermediate transfer belt 14 above the photosensitive drum 12 and cleans the intermediate transfer belt 14 so as to face the linear portion. By providing the cleaning device 32 above the photosensitive drum 12, the vicinity of the upper end of the intermediate transfer belt 14 that has not been used in the past while maintaining a belt cleaning area is used, and the overall height of the device is suppressed. be able to.

  A sensor 30 for detecting a toner image on the intermediate transfer belt 14 is provided in the vicinity of the lowermost end in the conveyance path of the intermediate transfer belt 14.

  Accordingly, since the distance from the secondary transfer unit 20 to the sensor 30 can be increased, for example, a thick sheet is carried into the secondary transfer unit 20 as the sheet P, and a speed fluctuation corresponding to the thickness of the sheet P occurs in the secondary transfer unit 20. Even in this case, the speed fluctuation is absorbed and attenuated depending on the length of the intermediate transfer belt 14, and it is difficult to reach the sensor 30 portion, so that the image detection by the sensor 30 is hardly adversely affected, and the image quality is deteriorated due to the speed fluctuation caused by the thickness of the paper P. Can be prevented.

  In addition, since the sensor 30 is in the vicinity of the lowermost end in the conveyance path of the intermediate transfer belt 14, there is an advantage that the sensor 30 does not easily get in the way when the replacement unit 34 described later is replaced.

  FIG. 3 shows an image forming apparatus according to the second embodiment of the present invention.

  As shown in FIG. 3, the image forming apparatus 11 includes a photosensitive drum 12 on which an electrostatic latent image is formed by performing image exposure by an exposure device 28 provided below the apparatus, and a surface on the photosensitive drum 12. A rotary developing device 16 that develops the electrostatic latent image with toner, and an intermediate transfer belt 14 that transfers the toner image on the photosensitive drum 12 to a sheet P that is a transfer material.

  The difference from the first embodiment is that a linear portion of the intermediate transfer belt 14 is formed above the photosensitive drum 12, and a sensor 30 for detecting a toner image on the intermediate transfer belt 14 is provided opposite to the linear portion. There is in point.

  Thereby, in this embodiment, since the distance from the secondary transfer unit 20 to the sensor 30 can be increased, for example, a thick sheet is carried into the secondary transfer unit 20 as the sheet P, and the speed fluctuation corresponding to the thickness of the sheet P is caused by the secondary transfer unit. Even if it occurs at 20, the speed fluctuation is absorbed and attenuated depending on the length of the intermediate transfer belt 14, and it is difficult to reach the sensor 30 portion, so that the image detection by the sensor 30 is hardly adversely affected, and the speed generated by the thickness of the paper P Image quality deterioration due to fluctuations can be prevented. Further, since the position of the sensor 30 is directly below a maintenance hatch 36A that is opened when the replacement unit 34, which will be described later, is exchanged, there is an advantage that the accessibility is good and the operation is easy when trouble occurs.

  FIG. 4 shows an image forming apparatus according to the third embodiment of the present invention.

  As shown in FIG. 4, the image forming apparatus 13 includes a replacement unit 34 that allows the intermediate transfer belt 14, the photosensitive drum 12, the waste toner container 24, and the like to be replaced together.

  The replacement unit 34 opens and closes the maintenance hatches 36A and 36B and attaches and detaches in the direction of the white arrow in the figure. At this time, the waste toner collected in the waste toner container 24 exists in the replacement unit 34. For this reason, for example, when the replacement unit 34 has a shape as shown in FIG. 8B, when the replacement unit 34 is placed on the desk or the floor, there is a possibility that the waste toner inside spills out.

  In contrast, in the present embodiment, the bottom surface of the replacement unit 34 is substantially horizontal and substantially parallel to the bottom surface of the waste toner container 24, so that the image forming apparatus remains on the desk or the floor. Therefore, it is possible to prevent accidents such as waste toner leaking outside.

1 is a diagram illustrating a configuration of an image forming apparatus according to a first embodiment of the present invention. 1 is a diagram illustrating a configuration of an image forming apparatus according to a first embodiment of the present invention. It is a figure which shows the structure of the image forming apparatus which concerns on the 2nd form of this invention. It is a figure which shows the structure of the image forming apparatus which concerns on the 3rd form of this invention. It is a figure which shows the structure of the conventional image forming apparatus. It is a figure which shows the structure of the conventional image forming apparatus. It is a figure which shows the structure of the conventional image forming apparatus. It is a figure which shows the structure of the conventional image forming apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 11 Image forming apparatus 12 Photosensitive drum 13 Image forming apparatus 14 Intermediate transfer belt 16 Rotary developing device 18 Fixing device 20 Primary transfer part 22 Secondary transfer part 24 Waste toner container 26 Paper discharge tray 28 Sheet storage part 30 Sensor 32 Cleaning device 34 Replacement unit

Claims (9)

A photosensitive drum on which an electrostatic latent image is formed on the surface by image exposure;
A rotary developer for developing the electrostatic latent image on the photosensitive drum with toner; an intermediate transfer belt for transferring the toner image on the photosensitive drum to a sheet as a transfer material;
A sheet storage unit provided below the rotary developer unit for storing the sheet;
A primary transfer portion for transferring the toner image from the photosensitive drum to the intermediate transfer belt;
A secondary transfer portion for transferring the toner image from the intermediate transfer belt to the sheet;
A sheet conveyance path provided substantially perpendicularly from the sheet storage unit to the secondary transfer unit;
A discharge tray for collecting the sheets discharged after image formation;
In an image forming apparatus comprising:
The intermediate transfer belt passes between the photosensitive drum and the discharge tray between the secondary transfer portion and the primary transfer portion,
The intermediate transfer belt extends between the primary transfer portion and the secondary transfer portion to a lower side than the rotation center of the rotary developer,
An image forming apparatus, wherein an end of the intermediate transfer belt closest to the rotary developer passes through the rotary developer side with respect to a rotation center of the photosensitive drum.
The image forming apparatus according to claim 1, wherein the primary transfer portion is formed by wrapping the intermediate transfer belt on the photosensitive drum.
3. The image formation according to claim 1, wherein the intermediate transfer belt is separated in a substantially tangential direction from the photosensitive drum on the downstream side of the photosensitive drum in the primary transfer portion. apparatus.
An exposure device that is provided under the photosensitive drum and performs image exposure on the photosensitive drum;
A waste toner container containing waste toner collected from the photosensitive drum;
With
The waste toner container is disposed between the intermediate transfer belt and an optical path of the exposure device;
4. The image forming apparatus according to claim 1, wherein two sides of the outer shape of the waste toner container are formed along the intermediate transfer belt and the optical path, respectively. 5.
An exchange unit that accommodates the waste toner container and the intermediate transfer belt and is exchangeable from the image forming apparatus main body,
The image forming apparatus according to claim 1, wherein a bottom surface of the waste toner container is substantially horizontal and substantially parallel to a bottom surface of the replacement unit.
6. A cleaning device for forming a straight portion of the intermediate transfer belt above the photosensitive drum and cleaning the intermediate transfer belt opposite to the straight portion. The image forming apparatus according to any one of the above.
7. The image forming apparatus according to claim 1, further comprising a detecting unit that detects a toner image on the intermediate transfer belt in the vicinity of a lowermost end in a conveyance path of the intermediate transfer belt.
2. A detection unit for forming a linear portion of the intermediate transfer belt above the photosensitive drum and detecting a toner image on the intermediate transfer belt opposite to the linear portion. The image forming apparatus according to claim 6.
9. The intermediate transfer belt according to claim 1, wherein the intermediate transfer belt is extended to a lower side than a lower end position of the rotary developing unit between the primary transfer portion and the secondary transfer portion. Image forming apparatus.

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