JPH10282867A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of giving a photoreceptor a uniform temperature distribution in its longitudinal direction even in the use of one or a small number of small type dew-condensation preventing heaters. SOLUTION: The one small type dew-condensation preventing heater 104 is disposed on the wall surface 102 of a partition 102, which is on the side situated far away from a photoreceptive drum 12, and in the lower part of the wall surface in the middle of the photoreceptive drum 12 in its longitudinal direction. Also, an opening 106 extending in the longitudinal direction of the photoreceptive drum 12 is made in the partition 102 above the dew-condensation preventing heater 104. The middle part 106a of the opening 106 is smaller in width W than its both ends 106b, and the width of the middle part 106 is about half the width of each end 106b. Also, on the upper edge of the opening 106, a projecting cover 108 extending in the longitudinal direction of the photoreceptive drum 12 is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, image forming apparatuses such as copying machines and printers using an electrophotographic system have been widely used.
FIG. 1 shows an example of a conventional electrophotographic image forming apparatus.
The copier will be described with reference to FIG.

FIG. 17 is a schematic diagram showing an example of a conventional copying machine.

The copying machine 10 includes a scanner unit 20 for reading an image recorded on a document, and a printer unit 30 for forming a toner image on a transfer target such as recording paper. In the scanner section 20, an image recorded on the original is read by the original illumination lamp 22, and light representing this image passes through the optical path L1 and is applied to the photosensitive drum 12 via the plurality of mirrors 24 and the lens unit 26. .

In the printer section 30, first, the photosensitive drum 12 rotating in the direction of the arrow 12a is uniformly charged by a corona discharger 32 utilizing corona discharge. Next, the photosensitive drum 12 is moved from the developing device 34 filled with the toner 34a.
The toner 34a charged to the opposite polarity to the charged polarity flies, and this toner 34a adheres to the electrostatic latent image formed on the photosensitive drum 12 to form a toner image (developed image). The image is visualized. On the other hand, recording paper 40 is fed by a pickup roller 38 from a cassette 36 in which the recording paper is stored, and the recording paper 40 is guided by a guide 42 and reaches a registration roller 44. The registration roller 44 conveys the recording paper 40 while nipping it at a predetermined timing, and the recording paper 40 is transferred to the lower transfer guide 46 and the upper transfer guide 4.
8 and is guided to a transfer area 52 sandwiched between the transfer charger 50 and the photosensitive drum 12. In transferring the toner image on the photosensitive drum 12 to the recording paper 40 guided to the transfer area 52, a voltage having a polarity opposite to that of the toner is applied to the corona wire 50a of the transfer charger 50. The recording paper 40 to which the toner image has been transferred is conveyed to the fixing device 56 by the conveyance unit 54. In the fixing device 56, the toner image on the recording paper 40 is heated and fixed by the heated roller pair 58. The recording paper on which the toner image has been fixed is discharged and stacked on a paper discharge tray 60.

A cleaner 62 for removing the toner remaining on the photosensitive drum 12 after the transfer is disposed downstream of the transfer charger 50 in the rotation direction of the photosensitive drum 12. On the opposite side of the photosensitive drum 12 across the corona charger 32, a pre-exposure / blank exposure unit 66 having a light source 64 and a mirror 68 is arranged. The pre-exposure / blank exposure unit 66 irradiates the photosensitive drum 12 with light passing through the optical path L2 in order to gradually reduce the charge remaining on the photosensitive drum 12 (pre-exposure), and forms left and right margins of the recording paper. In this case, the photosensitive drum 12 is irradiated with light passing through L3 and L3 'to the optical path (size blank exposure).
In many models, the light source for pre-exposure and the light source for size blank exposure are used in this way.

[0007] An exhaust unit 70 for discharging ozone generated by corona charging to the outside of the apparatus is disposed on the left side of the paper surface of the cleaner 62 and the pre-exposure / blank exposure unit 66. The exhaust unit 70 includes an ozone filter 72 that adsorbs ozone to lower the ozone concentration, and an exhaust fan 74 that guides the generated ozone outside the device.

Next, a structure for preventing dew condensation on the photosensitive drum 12 of the copying machine 10 will be described with reference to FIG.

FIG. 18 is a perspective view showing the lower portion of the photosensitive drum 12 described above, and the same components as those shown in FIG. 17 are denoted by the same reference numerals.

The transfer guide section 80 includes a registration roller 44.
Upper and lower transfer guides 48 and 46 for guiding the recording paper conveyed to the transfer area 52, a partition wall 82 integrally formed with the lower transfer guide 46, and the photosensitive drum 1.
2, dew condensation prevention heaters 84 and 86 for preventing dew condensation
And heat convection air 8 generated from the condensation prevention heaters 84 and 86
8 comprises an opening 90 and an eave 92 for leading the photosensitive drum 8 to the photosensitive drum 12 side. The partition wall 82 partitions the atmosphere around the photosensitive drum 12 into a portion near the photosensitive drum 12 and a portion far from the photosensitive drum 12.

For the dew condensation prevention heaters 84 and 86, self-regulating type thermistors and the like are often used in consideration of safety and reliability.
Is controlled so as to have a surface temperature of 40 to 70 ° C. Further, most of the dew condensation prevention heaters 84 and 86 are provided on the wall surface 8 of the partition wall 82 on the side remote from the photosensitive drum 12.
2a. The reason is that the condensation prevention heater 8
The convection of heat generated from the 4,86
2 in order to disperse them in the longitudinal direction. Partition wall 82
When the dew condensation prevention heaters 84 and 86 are arranged on the wall surface close to the photosensitive drum 12 among the wall surfaces, the convection heat acts directly on the surface of the photosensitive drum 12, and the temperature distribution may not be uniform. .

Next, a method for preventing dew condensation on the photosensitive drum 12 will be described.

Usually, the dew condensation prevention heaters 84 and 86 are energized when the main power supply of the copying machine 10 is turned off to perform fusing. In many cases, when the main power is on, the fixing device 56 is operating, so that the inside of the apparatus is heated to a considerable extent, and the dew condensation prevention heaters 84 and 86 are not required. However, in many cases where the user does not use the copying machine 10, the main power is turned off. In this case, when the environmental temperature and humidity suddenly change between daytime and nighttime (particularly when the humidity changes from low to high), dew condensation may occur on the photosensitive drum 12. As described above, the dew condensation prevention heaters 84 and 86 are provided to prevent such a problem. When the main power supply of the copying machine 10 is turned off, the energization starts and the futting is performed. The heat generated by the dew condensation prevention heaters 84 and 86 rises by convection, is blocked by the eaves 92, and is guided to the opening 90. Thereafter, the convection heat passes below the lower transfer guide 46 and warms the atmosphere near the sensitivity drum 12. . Thereby, dew condensation on the photosensitive drum 12 is prevented. Although depending on the size of the copying machine 10, a plurality of dew condensation preventing heaters 84 and 86 are usually used to make the temperature distribution on the surface of the photosensitive drum 12 uniform in the longitudinal direction.

[0014]

However, in the case of a photoreceptor, particularly a drum-shaped photoreceptor, the length is longer than the diameter and a uniform temperature distribution is required in the longitudinal direction.
A plurality of dew condensation prevention heaters are required along the longitudinal direction of the photosensitive drum, or a large dew condensation prevention heater sufficiently long in the longitudinal direction is required. In particular, in the case of a large-format copying machine or the like that uses a large-size recording paper, many have the above configuration, and a large number of dew condensation prevention heaters are used.

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide an image forming apparatus capable of providing a photosensitive member with a uniform temperature distribution in its longitudinal direction even if one or a small number of small condensation prevention heaters are used. I do.

[0016]

In order to achieve the above object, a first image forming apparatus of the present invention comprises a photosensitive drum on which an electrostatic latent image is formed, and a transfer for transferring the electrostatic latent image to a recording medium. A transfer guide for guiding a recording medium to an area, and partitioning the atmosphere around the photosensitive drum, which extends in the longitudinal direction of the photosensitive drum below the photosensitive drum and the transfer guide, into a portion near and far from the photosensitive drum. An image forming apparatus for forming an image on a recording medium, the image forming apparatus comprising: (1) a wall surface of the partition wall that is farther from the photosensitive drum and that is located at a central portion in a longitudinal direction of the photosensitive drum; And (2) the partition wall extends in the longitudinal direction above the dew condensation preventing heater and has an area at both ends in the longitudinal direction. In the center Wider than the product, is characterized in that in which at least one opening directing heat generated by the condensation prevention heater to the photosensitive drum is formed.

In order to achieve the above object, a second image forming apparatus according to the present invention comprises: a photosensitive drum on which an electrostatic latent image is formed;
A transfer guide that guides the recording medium to a transfer area where the electrostatic latent image is transferred to the recording medium, and an atmosphere around the photosensitive drum that extends in a longitudinal direction of the photosensitive drum below the photosensitive drum and the transfer guide. An image forming apparatus for forming an image on a recording medium, comprising a partition wall for partitioning a portion close to the photosensitive drum and a portion far from the photosensitive drum, (3) a wall surface of the partition wall that is farther from the photosensitive drum. (4) a dew condensation preventing heater disposed at a central portion in the longitudinal direction of the photosensitive drum to prevent dew condensation on the photosensitive drum.
The partition wall has at least one opening extending in the longitudinal direction above the dew condensation preventing heater and guiding heat generated by the dew condensation preventing heater to the photosensitive drum, and an upper end of the opening among the partition walls. And an eaves formed at the two ends in the longitudinal direction, the eaves being wider than the area at the center.

Here, (5) the partition wall has at least two openings vertically separated from each other, and an eave is formed at the upper end of the upper opening wider than the upper end of the lower opening. May be done.

In order to achieve the above object, a third image forming apparatus according to the present invention comprises: a photosensitive drum on which an electrostatic latent image is formed;
A transfer guide that guides the recording medium to a transfer area where the electrostatic latent image is transferred to the recording medium, and an atmosphere around the photosensitive drum that extends in a longitudinal direction of the photosensitive drum below the photosensitive drum and the transfer guide. In an image forming apparatus for forming an image on a recording medium, the image forming apparatus includes a partition wall for partitioning a portion close to the photosensitive drum and a portion far from the photosensitive drum. (7) a dew condensation prevention heater for preventing dew condensation on the photosensitive drum, which is disposed at a central portion in the longitudinal direction of the photosensitive drum.
The partition wall extends above the dew condensation prevention heater so as to be higher from both ends in the longitudinal direction toward both ends, and at least one opening for guiding heat generated by the dew condensation prevention heater to the photosensitive drum. The partition wall has an eave formed at the upper end of the opening and extending along the opening.

According to a fourth aspect of the present invention, there is provided a photosensitive drum on which an electrostatic latent image is formed;
A transfer guide that guides the recording medium to a transfer area where the electrostatic latent image is transferred to the recording medium, and an atmosphere around the photosensitive drum that extends in a longitudinal direction of the photosensitive drum below the photosensitive drum and the transfer guide. An image forming apparatus for forming an image on a recording medium, comprising a partition wall for partitioning a portion closer to the photosensitive drum and a portion farther from the photosensitive drum, (8) a wall surface of the partition wall that is farther from the photosensitive drum. (9) a dew condensation preventing heater disposed at a central portion of the photosensitive drum in a longitudinal direction for preventing dew condensation on the photosensitive drum.
The partition wall is formed with at least one opening that extends in the longitudinal direction above the dew condensation prevention heater and guides heat generated by the dew condensation prevention heater to the photosensitive drum. An opening width varying means for varying the width of the opening between the central portion and both end portions in the longitudinal direction is provided.

Here, the opening portion width changing means includes (1)
1) It may have a shape memory element in which the width of the opening is made different between the central part and both ends in the longitudinal direction according to temperature.

According to a fifth aspect of the present invention, there is provided an image forming apparatus comprising: a photosensitive drum on which an electrostatic latent image is formed;
A transfer guide that guides the recording medium to a transfer area where the electrostatic latent image is transferred to the recording medium, and an atmosphere around the photosensitive drum that extends in a longitudinal direction of the photosensitive drum below the photosensitive drum and the transfer guide. An image forming apparatus for forming an image on a recording medium, comprising: a partition wall for partitioning a portion close to the photosensitive drum and a portion far from the photosensitive drum, wherein (12) a wall surface of the partition wall that is farther from the photosensitive drum. A dew condensation preventing heater disposed at a central portion of the photosensitive drum in a longitudinal direction for preventing dew condensation on the photosensitive drum.
3) The partition wall has at least one opening extending in the longitudinal direction above the dew condensation prevention heater and guiding heat generated by the dew condensation prevention heater to the photosensitive drum, and the opening of the partition wall. An eaves extending along the opening is formed at the upper end of the
(14) An eaves width varying means for varying the width of the eaves at the central portion and both end portions in the longitudinal direction is provided.

Here, (15) the eaves width varying means includes:
There may be provided a shape memory element which makes the width of the eaves different between the center and both ends in the longitudinal direction in accordance with the temperature.

According to a sixth aspect of the present invention, there is provided a photosensitive drum on which an electrostatic latent image is formed;
A transfer guide that guides the recording medium to a transfer area where the electrostatic latent image is transferred to the recording medium, and an atmosphere around the photosensitive drum that extends in a longitudinal direction of the photosensitive drum below the photosensitive drum and the transfer guide. An image forming apparatus for forming an image on a recording medium, comprising a partition wall for partitioning a portion close to the photosensitive drum and a portion far from the photosensitive drum, wherein (16) the wall surface of the partition wall that is farther from the photosensitive drum. A dew condensation preventing heater disposed at a central portion of the photosensitive drum in a longitudinal direction for preventing dew condensation on the photosensitive drum.
7) The partition wall has at least one opening extending in the longitudinal direction above the dew condensation preventing heater and guiding heat generated by the dew condensation preventing heater to the photosensitive drum, and the opening of the partition wall. An eaves extending along the opening is formed at the upper end of the
(18) There is provided a variable means for changing the width of the opening and / or the width of the eaves at the center in the longitudinal direction and at both ends.

According to a seventh aspect of the present invention, there is provided an image forming apparatus comprising: a photosensitive drum on which an electrostatic latent image is formed;
A transfer guide that guides the recording medium to a transfer area where the electrostatic latent image is transferred to the recording medium, and an atmosphere around the photosensitive drum that extends in a longitudinal direction of the photosensitive drum below the photosensitive drum and the transfer guide. An image forming apparatus comprising a partition wall for partitioning a portion close to the photosensitive drum and a portion far from the photosensitive drum, wherein (19) a wall surface of the partition wall that is farther from the photosensitive drum among the wall surfaces of the partition wall. And a dew condensation preventing heater disposed at a central portion of the photosensitive drum in a longitudinal direction for preventing dew condensation on the photosensitive drum.
0) The partition wall has at least one opening extending in the longitudinal direction above the dew condensation prevention heater and having an area at both ends in the longitudinal direction larger than an area at a central part. (21) The air conditioner further comprises (21) an air duct which substantially seals the dew condensation prevention heater and connects the dew condensation prevention heater to the opening.

According to an eighth aspect of the present invention, there is provided an image forming apparatus comprising: a photosensitive drum on which an electrostatic latent image is formed;
A transfer guide that guides the recording medium to a transfer area where the electrostatic latent image is transferred to the recording medium, and an atmosphere around the photosensitive drum that extends in a longitudinal direction of the photosensitive drum below the photosensitive drum and the transfer guide. An image forming apparatus for forming an image on a recording medium, comprising a partition wall for partitioning a portion close to the photosensitive drum and a portion far from the photosensitive drum, (22) a wall surface of the partition wall that is farther from the photosensitive drum. And a dew condensation preventing heater disposed at a central portion of the photosensitive drum in a longitudinal direction for preventing dew condensation on the photosensitive drum.
3) The partition wall is formed at the center in the longitudinal direction above the dew condensation prevention heater, and has a central opening for guiding heat generated by the dew condensation prevention heater to the photosensitive drum, and above the dew condensation prevention heater. And has both end openings formed at both ends in the longitudinal direction.
4) An air duct connecting the dew condensation prevention heater and the openings at both ends is provided.

In order to achieve the above object, a ninth image forming apparatus according to the present invention comprises: a photosensitive drum on which an electrostatic latent image is formed;
A transfer guide that guides the recording medium to a transfer area where the electrostatic latent image is transferred to the recording medium, and an atmosphere around the photosensitive drum that extends in a longitudinal direction of the photosensitive drum below the photosensitive drum and the transfer guide. An image forming apparatus for forming an image on a recording medium, comprising a partition wall for partitioning a portion close to the photosensitive drum and a portion far from the photosensitive drum, (25) a wall surface of the partition wall that is farther from the photosensitive drum. And a dew condensation preventing heater disposed at a central portion of the photosensitive drum in a longitudinal direction for preventing dew condensation on the photosensitive drum.
6) The partition wall extends in the longitudinal direction above the dew condensation preventing heater and has at least one opening formed therein, the area at both ends in the longitudinal direction being equal to the area at the center. (27) The air conditioner further comprises (27) an air duct which substantially seals the dew condensation prevention heater and connects the dew condensation prevention heater and the opening.

The tenth aspect of the present invention for achieving the above object.
An image forming apparatus includes a photosensitive drum on which an electrostatic latent image is formed, a transfer guide for guiding a recording medium to a transfer area for transferring the electrostatic latent image to the recording medium, and a transfer guide below the photosensitive drum and the transfer guide. (28) An image forming apparatus for forming an image on a recording medium, comprising: a partition wall extending in a longitudinal direction of the photosensitive drum and partitioning an atmosphere around the photosensitive drum into a portion close to the photosensitive drum and a portion far from the photosensitive drum. A temperature measuring device for measuring a surface temperature of the photosensitive drum; and (29) a wall surface of the partition wall that is farther from the photosensitive drum and is disposed at a central portion in a longitudinal direction of the photosensitive drum. (30) the partition wall extends in the longitudinal direction above the dew condensation prevention heater and transfers heat generated by the dew condensation prevention heater to the photosensitive drum. And (31) adjusting means for adjusting the amount of heat guided to the opening based on the temperature measured by the temperature measuring device. It is characterized by having.

[0029]

Embodiments of the present invention will be described below with reference to the drawings.

The schematic configuration of the copying machine of each of the following embodiments is as follows.
This is the same as the conventional one shown in FIG. 17, and the same applies to the energization control of the dew condensation prevention heater. Therefore, the characteristic portions of each embodiment will be described here. In the drawings showing the embodiments, the same components as those shown in FIGS. 17 and 18 are denoted by the same reference numerals.

First, a first embodiment will be described with reference to FIG.

FIG. 1 is a perspective view showing the transfer guide unit 100 and the photosensitive drum 12 of the copying machine according to the first embodiment.

The partition wall 102 of the transfer guide section 100
It is formed integrally with the lower transfer guide 46 below the lower transfer guide 46, and partitions the atmosphere around the photosensitive drum 12 into a portion near the photosensitive drum 12 and a portion far from the photosensitive drum 12. One small-sized dew condensation prevention heater 104 is arranged on the wall surface 102 a of the partition wall 102, which is farther from the photosensitive drum 12, and at the lower part of the longitudinal center of the photosensitive drum 12. In the partition wall 102, the dew condensation prevention heater 10
An opening 106 extending in the longitudinal direction of the photosensitive drum 12 is formed in a portion above the photosensitive drum 12. The width 106 of the central portion 106a of the opening 106 is smaller than that of both ends 106b,
The width of the central portion 106a is about half the width of both ends 106b. Therefore, the area of both ends 106b of the opening 106 is larger than the area of the central part 106a. An eave 108 extending in the longitudinal direction of the photosensitive drum 12 is provided at an upper end of the opening 106.
Are formed. The width of the eaves 108 is almost equal in any part.

The heat generated by the dew condensation prevention heater 104 rises by convection, is blocked (caught) by the eaves 108, passes through the opening 106, and flows into the photosensitive drum 12 side. As described above, since the width W of the central portion 106a of the opening 106 is smaller than that of both ends 106b, the amount of convective heat passing through the opening 106 is smaller at both ends 1 than at the center 106a.
06b is more. For this reason, the amount of convective heat flowing into the photosensitive drum 12 is relatively larger at both ends 106b than at the center 106a of the opening 106. As a result, the ambient temperature in the vicinity of the photosensitive drum 12 becomes substantially uniform over the longitudinal direction of the photosensitive drum 12.

The dew condensation prevention heater 104 is controlled at 60 ° C.
The surface temperature of the photosensitive drum 12 (of the lower transfer guide 46,
(Near the tip closest to the photosensitive drum 12)
Was examined in the longitudinal direction. Central part 10 of opening 106
In the vicinity of the leading end of the transfer lower guide 46 corresponding to 6a and both end portions 106b, the temperature was higher than room temperature by about 2 ° C., and good results were obtained.

The second embodiment will be described with reference to FIG.

FIG. 2 is a perspective view showing the transfer guide portion 110 and the photosensitive drum 12 of the copying machine according to the second embodiment.
The same reference numerals are given to the same components as those of the above.

The partition wall 112 of the transfer guide section 110 is
It is formed integrally with the lower transfer guide 46 below the lower transfer guide 46, and partitions the atmosphere around the photosensitive drum 12 into a portion near the photosensitive drum 12 and a portion far from the photosensitive drum 12. The dew condensation prevention heater 1 at the center of the partition wall 112
Above 04, a first opening 114 is formed.
At the upper end of the first opening 114, a first eave 116 extending in the longitudinal direction of the photosensitive drum 12 is formed. The width of the first eave 116 is substantially equal in any part. Convection heat generated by the dew condensation prevention heater 104 passes through the first opening 114 and flows into the vicinity of the center of the photosensitive drum 12 in the longitudinal direction.

The first opening 114 of the partition wall 112
The second opening portions 118 and 120
Are formed. At the upper ends of the second openings 118 and 120, a second eave 122 extending in the longitudinal direction of the photosensitive drum 12 is formed continuously. The width of the second eave 122 is the first eave 1
16 is larger than the width. Also, the second openings 118, 12
0 was not formed at the center of the partition wall 112, but was formed only at the left and right sides. For this reason, an increase in convective heat generated by the dew condensation prevention heater 104 is only partially blocked because the width of the first eave 116 is relatively small. The unblocked heat rises further by convection, is blocked by the second eaves 122, and passes through the second openings 118 and 120.

As described above, the first eave 116 of the first opening 114 formed at the center of the partition wall 112 is made smaller,
The amount of heat passing through the first opening 114 is relatively suppressed, and heat is convected on both sides of the first opening 114, while the second opening 1
18 and 120, the second eaves 122
To increase. Thus, excess heat not blocked by the first eave 116 can be efficiently distributed to both ends. Also in the present embodiment, the photosensitive drum 12
, A uniform temperature distribution was obtained in the longitudinal direction.

The third embodiment will be described with reference to FIG.

FIG. 3 is a perspective view showing the transfer guide section 130 and the photosensitive drum 12 of the copying machine according to the third embodiment.
The same reference numerals are given to the same components as those of the above.

The partition wall 132 of the transfer guide section 130 is
It is formed integrally with the lower transfer guide 46 below the lower transfer guide 46, and partitions the atmosphere around the photosensitive drum 12 into a portion near the photosensitive drum 12 and a portion far from the photosensitive drum 12. One small-sized dew condensation prevention heater 104 is arranged on the partition wall 132 on the wall surface 132a farther from the photosensitive drum 12 and at the lower portion of the longitudinal center of the photosensitive drum 12. Of the partition wall 132, the condensation prevention heater 10
An opening 136 that extends in the longitudinal direction of the photosensitive drum 12 is formed in a portion above 4. The central portion 136a of the opening 136 has a width W smaller than that of both ends 136b,
The width of the central portion 136a is about half the width of both ends 136b. Therefore, the area of both ends 136b of the opening 136 is larger than the area of the central part 136a. An eave 138 extending in the longitudinal direction of the photosensitive drum 12 is provided at an upper end of the opening 136.
Are formed. The width of the central portion 138a of the eave 138 is narrow, and gradually increases toward both ends. That is, the area of both ends 138b of the eave 138 is larger than the area of the central part 138a. Also, the tip 1 of the eave 138
38c is bent inward to make it difficult to escape convective heat.

The heat generated from the dew condensation prevention heater 104 rises by convection, and the rise is blocked by the eaves 138 so that the opening 13
6 and flows into the photosensitive drum 12 side. As described above, the area of both ends 138b of the eaves 138 is the center 138a.
And the central portion 136 of the opening 136
a is smaller in width W than both ends 136b,
The amount of convective heat passing through 6 is greater at both ends 136b than at central portion 136a. For this reason, the amount of convective heat flowing into the photosensitive drum 12 side depends on the central portion 136a of the opening 136.
Both ends 136b are relatively larger than those at both ends. As a result, the ambient temperature in the vicinity of the photosensitive drum 12 becomes substantially uniform over the longitudinal direction of the photosensitive drum 12.

The dew condensation prevention heater 104 is controlled at 60 ° C.
The surface temperature of the photosensitive drum 12 (of the lower transfer guide 46,
(Near the tip closest to the photosensitive drum 12)
Was examined in the longitudinal direction. Central part 13 of opening 136
In the vicinity of the leading end of the lower transfer guide 46 corresponding to 6a and both end portions 136b, the temperature was higher than room temperature by about 2 ° C., and good results were obtained.

The fourth embodiment will be described with reference to FIGS.

FIG. 4 is a front view showing a state where the second eave is open, and FIG. 5 is a front view showing a state where the second eave is closed. In these drawings, the same components as those in FIG. 1 are denoted by the same reference numerals.

The partition wall 142 of the transfer guide section 140
It is formed integrally with the lower transfer guide 46 below the lower transfer guide 46, and partitions the atmosphere around the photosensitive drum 12 into a portion near the photosensitive drum 12 and a portion far from the photosensitive drum 12. One small-sized dew condensation prevention heater 104 is arranged on the wall surface 142 a of the partition wall 142 on the side farther from the photosensitive drum 12 and at the lower portion of the central portion in the longitudinal direction of the photosensitive drum 12. In the partition wall 142, the dew condensation prevention heater 10
An opening 144 extending in the longitudinal direction of the photosensitive drum 12 is formed in a portion above the photosensitive drum 12. The opening 144 extends so as to be higher from the center toward both ends. The central portion 144a of the opening 144 is at both ends 14a.
4b is narrower than the width W, and the width of the central portion 144a is
It is about half the width of 44b. At the upper end of the opening 144, an eave 146 extending along the opening 144 in the longitudinal direction of the photosensitive drum 12 is formed. The width of the eaves 146 is almost equal in any part. Thus, the opening 144
The width of both ends 144b is smaller than the width of the central portion 144a, and the eaves 146 are formed at the upper end of the opening 144, so that convection flows toward the both ends 144b rather than the central portion 144a of the opening 144. Heat passes easily.

An opening 148 having a length approximately equal to the length of the central portion 144a and a width approximately equal to the width of both ends 144b is formed below the central portion 144a of the opening 144. At the upper end of the opening 148, a movable eave 150 made of a shape memory element is provided. When the temperature of the environment reaches 50 ° C., the movable eaves 150 changes into a shape stored in the element. As a result, when the temperature of the environment reaches 50 ° C., as shown in FIG.
Changes the shape from the state where the opening 148 is opened to the state where it is closed.

The flow of heat generated from the dew condensation prevention heater 104 will be described.

The surface temperature of the condensation prevention heater 104 is self-regulated to 70 ° C. As shown in FIG. 4, when the dew condensation prevention heater 104 starts to generate heat, the movable eaves 150
Is the temperature equal to the ambient temperature, so that the opening 148 is open. In this case, much convection heat 88 flows into the opening 148. The convection heat 89 not blocked by the movable eave 150 is blocked by the eave 146. Eaves 146
Is gradually increased toward the end in the longitudinal direction, so that the convective heat 89 easily moves toward the end. Further, since the central portion 144a of the opening 144 is narrower than the both ends 144b, the inflow of the convective heat 89 is larger at the both ends 144b than at the central portion 144a. Therefore, when the temperature of the movable eaves 150 does not reach 50 ° C. (a relatively short time after the power supply to the dew condensation prevention heater 104 is started), much of the convection heat flows into the opening 148 and In the longitudinal direction, the central portion has a slightly higher temperature distribution.

When the temperature of the movable eaves 150 reaches 50 ° C. after energization of the dew condensation prevention heater 104 is started, the movable eaves 150 return to the memorized shape. Here, as shown in FIG. 5, the movable eave 150 has a shape in which the opening 148 is closed. In this case, since the eaves 146 block most of the convective heat, the convective heat is applied to the central portion 1 of the opening 144 as described above.
It flows into both ends 144b more than 44a.

As described above, the movable eaves 150 have the threshold temperature of 50 ° C.
Repeat the opening and closing operation with. As a result, the condensation prevention heater 10
For a relatively short time after the energization start time of No. 4, the photosensitive drum 12
In this case, the temperature distribution in the central portion in the longitudinal direction is slightly higher, but in a long time such as at night when the power of the copying machine 10 is turned off, the photosensitive drum 12 has a substantially uniform temperature distribution in the longitudinal direction.

The fifth embodiment will be described with reference to FIG.

FIG. 6 is a perspective view showing the transfer guide section 160 and the photosensitive drum 12 of the copying machine according to the fifth embodiment.
The same reference numerals are given to the same components as those of the above.

The partition wall 162 of the transfer guide section 160
It is formed integrally with the lower transfer guide 46 below the lower transfer guide 46, and partitions the atmosphere around the photosensitive drum 12 into a portion near the photosensitive drum 12 and a portion far from the photosensitive drum 12. One small-sized dew condensation prevention heater 104 is disposed on the wall surface 162 a of the partition wall 160, which is farther from the photosensitive drum 12, and at the lower portion of the longitudinal center of the photosensitive drum 12. Of the partition wall 162, the dew condensation prevention heater 10
An opening 164 extending in the longitudinal direction of the photosensitive drum 12 is formed in an upper portion of the photosensitive drum 12. The opening 164 is inclined such that its position becomes higher from the center toward both ends, and the inclination angle is in the range of 10 ° to 30 °.
An eave 166 is formed at the upper end of the opening 164 and extends along the opening 164 in the longitudinal direction of the photosensitive drum 12. The eave 166 is positioned such that its position becomes higher toward both ends in the longitudinal direction of the photosensitive drum 12. It is inclined. This eaves 1
The width of 46 is almost equal in any part.

In the partition wall 162, the opening 16
Two openings 168 and 170 are separately formed symmetrically at a portion between the heater 4 and the dew condensation prevention heater 104. Therefore, the two openings 168 and 170 are not connected,
An opening is not formed in a part of the partition wall 162 directly below the center of the opening 164. Two openings 168, 17
0 are provided with eaves 172 and 174 along the openings 168 and 170, respectively.
74 is inclined so that the position becomes higher toward both ends in the longitudinal direction of the photosensitive drum 12.

The convective heat generated by the dew condensation prevention heater 104 is first blocked by the eaves 172 and 174 and the openings 168 and 17 are opened.
0 and is mainly distributed to both ends of the photosensitive drum 12 in the longitudinal direction. Although the convection heat not blocked by the eaves 172 and 174 rises, it rises along the eaves 166 while passing through the opening 164 while being blocked by the eaves 166, and flows into the photosensitive drum 12. In this manner, the eaves 166, 172, and 172 are positioned such that the position becomes higher toward both ends in the longitudinal direction of the photosensitive drum 12.
By providing the 174 and the openings 164, 168, 170, a uniform temperature distribution was obtained in the photosensitive drum 12 in the longitudinal direction.

The sixth embodiment will be described with reference to FIGS.

FIG. 7 is a perspective view showing a state where the center opening is open, and FIG. 8 is a perspective view showing a state where the center opening is closed. In these drawings, the same components as those in FIG. 1 are denoted by the same reference numerals.

The partition wall 182 of the transfer guide section 180
It is formed integrally with the lower transfer guide 46 below the lower transfer guide 46, and partitions the atmosphere around the photosensitive drum 12 into a portion near the photosensitive drum 12 and a portion far from the photosensitive drum 12. One small-sized dew condensation prevention heater 104 is arranged on the wall surface 182 a of the partition wall 182 on the side farther from the photosensitive drum 12 and at the lower portion of the longitudinal center of the photosensitive drum 12. In the partition wall 142, the dew condensation prevention heater 10
Four small openings 184a and 184b extending in the longitudinal direction of the photosensitive drum 12 are formed in the upper part of the photosensitive drum 12. Further, an eave 186 extending in the longitudinal direction of the photosensitive drum 12 is formed above the openings 184a and 184b. The width of this eave 186 is almost equal in any part.

Of the six openings 184a and 184b,
Below the two openings 184a located at the center, a slide shutter 188 that opens and closes the openings 184a is arranged. A rack 190 is fixed to one end of the slide shutter 188, and a pinion 192 meshes with the rack 190. The pinion 192 is rotated by a driving source (not shown) such as a motor to
0 is moved up and down, and the slide shutter 188 is moved up and down to open and close the opening 184a.

The open position of the slide shutter 188 (FIG. 7)
And the closed position of the slide shutter 188 (FIG. 8) is controlled by the open ratio when open: close = 1: 2. For example, open: closed = 5
Minutes: 10 minutes. Accordingly, the amount of heat distribution to the four openings 184b at both ends can be increased, and a uniform temperature distribution in the longitudinal direction of the photosensitive drum 12 can be obtained.

The seventh embodiment will be described with reference to FIGS.

FIG. 9 is a perspective view showing a state before the eaves move, and FIG. 10 is a perspective view showing a state after the eaves move. In these drawings, the same components as those in FIG. 1 are denoted by the same reference numerals.

The partition wall 202 of the transfer guide section 200
It is formed integrally with the lower transfer guide 46 below the lower transfer guide 46, and partitions the atmosphere around the photosensitive drum 12 into a portion near the photosensitive drum 12 and a portion far from the photosensitive drum 12. One small-sized dew condensation prevention heater 104 is arranged at a lower part of the partition wall 202 on a wall surface 202 a on a side far from the photosensitive drum 12 and at a central portion in a longitudinal direction of the photosensitive drum 12. Of the partition wall 202, the dew condensation prevention heater 10
An opening 204 extending in the longitudinal direction of the photosensitive drum 12 is formed in a portion above the photosensitive drum 12. Also, the opening 204
The eaves 20 extending in the longitudinal direction of the photosensitive drum 12
6 are formed. The eaves 206 have an L-shaped cross section, and have a shape obtained by bending two plates. One of the two plates 208 is in contact with the wall surface 202a,
The other piece 210 is substantially perpendicular to the wall surface 202a. The eaves 206 include an eaves portion 206a at both ends made of a metal plate or a plastic plate, and an eaves portion 206b at the center made of a shape memory element whose shape changes. At the threshold temperature of 40 ° C.,
An element that changes its shape is used.

When the temperature of the eaves portion 206b is lower than 40 ° C.,
As shown in FIG. 9, the eaves 206 are flat, and the width of the opening 204 is constant in the longitudinal direction. This shape is used for a certain period of time after the power supply to the dew condensation prevention heater 104 is turned off or when the power supply is started, and the amount of convective heat flowing into the central portion of the opening 204 is slightly larger. When a certain period of time has elapsed after the start of energization, the temperature of the eaves portion 206b exceeds 40 ° C. and the shape memory function is activated, and as shown in FIG. Changes to As a result, the opening 204 changes to an opening 204 'as shown in FIG. 10, and the width gradually increases from the center to both ends of the opening 204'. With the shapes of the eaves 206 and the opening 204 ′ shown in FIG. 10, a substantially uniform temperature distribution can be obtained in the longitudinal direction of the photosensitive drum 12.

The above-described seventh embodiment is effective for a copying machine in which the size of the copying machine is not relatively large. In the flat eaves 206 shown in FIG.
Although a certain time from the start of energization is longer, the photosensitive drum 12
A good effect can be obtained when it is necessary to rapidly increase the temperature in the vicinity of.

The eighth embodiment will be described with reference to FIG.

FIG. 11 is a front view showing a partition wall provided with an air duct, and the same components as those in FIG. 1 are denoted by the same reference numerals.

The partition wall 212 of the transfer guide section 210 is
It is formed integrally with the lower transfer guide 46 below the lower transfer guide 46, and partitions the atmosphere around the photosensitive drum 12 into a portion near the photosensitive drum 12 and a portion far from the photosensitive drum 12. One small-sized dew condensation prevention heater 104 is arranged on the wall surface 212 a of the partition wall 212 on the side farther from the photosensitive drum 12 and at the lower portion of the longitudinal center of the photosensitive drum 12. Of the partition wall 212, the dew condensation prevention heater 10
An opening 214 extending in the longitudinal direction of the photosensitive drum 12 is formed in a portion above the photosensitive drum 12. The width of the opening 214 is substantially equal in the longitudinal direction.

The dew condensation preventing heater 104 is roughly sealed by a case 216 made of a plastic material or the like. The case 216 has an air inlet 216 a and a convection heat outlet 21 for sending convection heat to the air duct 218.
6b and 216c are formed. Air duct 218
Is arranged to be routed from the case 216 to both left and right ends, and then to the center. The air duct 218 covers the opening 214 and the opening 21
4 and the dew condensation prevention heater 104 are connected. Therefore, the heat generated by the dew condensation prevention heater 104 is
18 flows from both ends of the opening 214 to the center. Therefore, much heat passes through both ends of the opening 214, and the remaining heat passes through the center. As a result, the photosensitive drum 12 has a uniform temperature distribution in the longitudinal direction.

The ninth embodiment will be described with reference to FIG.

FIG. 12 is a front view showing a partition wall provided with an air duct, and the same components as those in FIG. 1 are denoted by the same reference numerals.

The partition wall 222 of the transfer guide section 220
It is formed integrally with the lower transfer guide 46 below the lower transfer guide 46, and partitions the atmosphere around the photosensitive drum 12 into a portion near the photosensitive drum 12 and a portion far from the photosensitive drum 12. One small dew condensation prevention heater 104 is disposed on the wall surface 222 a of the partition wall 222 on the side farther from the photosensitive drum 12 and at the lower portion of the longitudinal center of the photosensitive drum 12. Of the partition wall 222, the condensation prevention heater 10
An opening 224 slightly longer than the length of the dew condensation prevention heater 104 and substantially equal in width is formed directly above the dew condensation preventing heater 104. An eave 226 is provided at the upper end of the opening 224.

In the partition wall 222, two openings 2 are formed obliquely above the left and right sides of the dew condensation preventing heater 104.
28 and 230 are formed. These two openings 22
8, 230, the width of the photosensitive drum 12 is increased stepwise toward both ends in the longitudinal direction.

The dew condensation prevention heater 104 is covered by a frame 232 so as to be substantially sealed. The frame 232 has an air inlet 232a at its lower part, a convective heat outlet 232b at its upper part, and convective heat outlets 232c and 232d for connecting to the air duct 234 on the left and right, respectively. The air duct 234 is connected to the dew condensation prevention heater 104.
And the two openings 228 and 230 are connected.

The heat generated from the dew condensation prevention heater 104 is
Air is sucked in from the air inlet 232a, which causes heat convection. There are three outflow directions of convection heat, one of which flows out of the convection outlet 232b. The convection heat flowing out of the convection outlet 232b is directly transmitted to the eaves 226.
And flows into the opening 224 to heat mainly the central portion of the photosensitive drum 12 in the longitudinal direction. Convection heat also flows out of the convection heat outlets 232c and 232d. Convection heat outlet 2
As shown in FIG. 12, heat flowing out of the openings 228 and 232d passes through the air duct 234 drawn from the longitudinal end of the photosensitive drum 12 to the center thereof.
Reach 230. As described above, the openings 228 and 23
Since 0 is gradually narrowed from the longitudinal end to the center, much heat flows in from the longitudinal end. As a result, the photosensitive drum 12 has a uniform temperature distribution in the longitudinal direction.

Although it is easy to apply convection heat directly to the center of the photosensitive drum 12 in the longitudinal direction, it is difficult to apply convection heat directly to both ends of the photosensitive drum 12 in the longitudinal direction. Convection heat is distributed through it through to both ends. At this time, in order to prevent too much convective heat from flowing out to both ends, the air duct 2 is moved from both ends to the center.
34, and the end portions of the openings 228 and 230 were widened. With such a configuration, the photosensitive drum 12
, A substantially uniform temperature distribution was obtained in the longitudinal direction.

The tenth embodiment will be described with reference to FIG.

FIG. 13 is a front view showing a partition wall provided with an air duct, and the same components as those in FIG. 1 are denoted by the same reference numerals.

The partition wall 242 of the transfer guide 240 is
It is formed integrally with the lower transfer guide 46 below the lower transfer guide 46, and partitions the atmosphere around the photosensitive drum 12 into a portion near the photosensitive drum 12 and a portion far from the photosensitive drum 12. One small-sized dew condensation prevention heater 104 is disposed on the wall 242 a of the partition wall 242 on the side farther from the photosensitive drum 12 and at the lower part of the center of the photosensitive drum 12 in the longitudinal direction. Of the partition wall 242, the dew condensation prevention heater 10
An opening 244 is formed in a portion above 4.
In the opening 244, the central portion in the longitudinal direction of the photosensitive drum 12 is the narrowest, and the width increases stepwise toward both ends.

The dew condensation prevention heater 104 is roughly sealed by a case 246 around it. Case 24
6 has an air inlet 246 for feeding air.
a is formed, while the upper part of the case 246 is
A convection heat outlet 246b for sending convection heat to the air duct 248 is formed. The air duct 248 extends upward from the center, and branches off to both ends to connect to the opening 244 on the way. When convection heat is sent through a closed channel such as the air duct 248,
The convective heat flow gradually decreases from upstream to downstream.
However, in the present embodiment, since the width of the opening 244 is increased stepwise from the center to both ends, the photosensitive drum 12
, A uniform temperature distribution was obtained in the longitudinal direction.

The eleventh embodiment will be described with reference to FIG.

FIG. 14 is a front view showing a partition wall provided with an air duct, and the same components as those in FIG. 1 are denoted by the same reference numerals.

The partition wall 252 of the transfer guide section 250
It is formed integrally with the lower transfer guide 46 below the lower transfer guide 46, and partitions the atmosphere around the photosensitive drum 12 into a portion near the photosensitive drum 12 and a portion far from the photosensitive drum 12. One small-sized dew condensation prevention heater 104 is arranged on the wall surface 252 a of the partition wall 252 on the side far from the photosensitive drum 12 and at the lower part of the central portion in the longitudinal direction of the photosensitive drum 12. Of the partition wall 252, the dew condensation prevention heater 10
Four openings 254, 256 and 258 are formed in the upper part of the photosensitive drum 12 along the longitudinal direction of the photosensitive drum 12.

The dew condensation prevention heater 104 is roughly sealed by a case 260 around it. Case 26
0, an air inlet 260 for feeding air is provided.
a is formed. On the other hand, at the top of the case 260,
Three convection heat outlets 260b and 26 serving as convection heat outlets
0c and 260d are formed. These three convective heat outlets 260b, 260c, 260d are connected to an end air duct 262, a center air duct 264, and an end air duct 266, respectively. End air duct 262,
The center air duct 264 and the end air duct 266 are connected to the openings 254, 256, 258, respectively. The central air duct 264 is provided with a valve 268 in the middle of the flow path. When the handle of the valve 268 is at the position 268a indicated by the solid line, the valve 268 is open, and when the handle is at the position 268b indicated by the broken line, the valve 268 is closed.

A central thermistor 270 and an end thermistor 272 are disposed at the end of the lower transfer guide 46 on the photosensitive drum 12 side.
The ambient temperature near the photosensitive drum 12 is measured.

Next, the control of this embodiment will be described.

When the dew condensation prevention heater 104 is energized,
Self-regulate so that the temperature becomes ℃. The valve 268 provided in the central air duct 264 has a solid line position 26 at the start of energization.
8a. In this case, the central air duct 264
Convection heat is supplied to the end air ducts 262 and 266. The central thermistor 270 and the end thermistor 272 detect the ambient temperature near the photosensitive drum 12 in real time. For example, when the detection value of the center thermistor 270 is higher than the detection value of the end thermistor 272,
Valve 268 is moved to position 268b by valve drive means (not shown).
(Closed state) and the convection heat to the end air ducts 262 and 266 is increased. When the detection value of the end thermistor 272 becomes higher than the detection value of the center thermistor 270, the valve 268 is returned to the position 268a (open state).

Thus, by comparing the detection values of the central thermistor 270 and the end thermistor 272 and controlling the position of the valve 268, a uniform temperature distribution in the longitudinal direction of the photosensitive drum 12 can be accurately obtained. The present embodiment has an effect that an accurate temperature distribution can be obtained even for a large-sized copying machine. In this embodiment, one temperature detecting element is provided at each of the center and the end. However, if there is experimental data of a certain temperature distribution, one temperature detecting element may be provided at the end or the center. ,
The temperature can be controlled to be uniform in the longitudinal direction of the photosensitive drum 12.

The twelfth embodiment will be described with reference to FIG.

FIG. 15 is a perspective view showing the transfer guide portion 280 and the photosensitive drum 12 of the copying machine according to the twelfth embodiment.
The same components as those in FIG. 1 are denoted by the same reference numerals.

The partition wall 282 of the transfer guide section 280
It is formed integrally with the lower transfer guide 46 below the lower transfer guide 46, and partitions the atmosphere around the photosensitive drum 12 into a portion near the photosensitive drum 12 and a portion far from the photosensitive drum 12. One small-sized dew condensation prevention heater 104 is disposed on the wall surface 282 a of the partition wall 282, which is farther from the photosensitive drum 12, and below the photosensitive drum 12 in the center in the longitudinal direction. Of the partition wall 282, the dew condensation prevention heater 10
An opening 284 having substantially the same width and extending in the longitudinal direction of the photosensitive drum 12 is formed in an upper part of the photosensitive drum 12. Also,
At the upper end of the opening 284, an eave 286 having substantially the same width and extending in the longitudinal direction of the photosensitive drum 12 is formed.

An opening variable member 288 (an example of an adjusting means or a variable means according to the present invention) for changing the width of the central portion 284a of the opening 284 is disposed below the opening 284. The opening variable member 288 is moved by a driving means such as a solenoid 290 between a position distant from the opening 284 (position at 288) and a position closing the central portion 284a of the opening 284 (position at 288 '). Reciprocating between Further, a thermistor 292 is arranged in a portion of the partition wall 282 on the photosensitive drum 12 side, and detects an ambient temperature on the photosensitive drum 12 side above the opening 284.

The control of the opening varying means 288 will be described.

The condensation prevention heater 104 has a surface temperature of 7
The temperature is self-regulated to be 0 ° C. Opening variable means 2
When the heater 88 is in the open state and power is continuously supplied to the dew condensation prevention heater 104, the temperature distribution in the longitudinal direction of the photosensitive drum 12 below the lower transfer guide 46 is higher by about 10 ° C. at the center than at the ends. Become. That is, for example, when the room temperature is 20 ° C. and the temperature is saturated, the output value of the thermistor 292 is 30 ° C., and the measured value at the center is 40 ° C. Referring to this experimental value, when the output value of the thermistor 292 reaches 25 ° C., the central portion 284 a of the opening 284 is closed by the opening variable member 288 for a predetermined time, and the output value of the thermistor 292 becomes 35 °.
When the temperature reaches ° C., the position of the opening variable means 288 is lowered to open the central portion 284 a of the opening 284. By repeating such control, a substantially uniform temperature distribution was obtained in the longitudinal direction of the photosensitive drum 12.

Referring to FIG. 16, the temperature distribution in the longitudinal direction of the photosensitive drum 12 obtained in each of the above embodiments will be described together with a comparative example.

FIG. 16 is a graph showing the temperature distribution of the photosensitive drum 12 in the longitudinal direction.

The horizontal axis of the graph indicates the longitudinal direction of the photosensitive drum 12, where C indicates the center and E indicates the end. The vertical axis indicates the temperature measured by bringing a thermocouple into contact with the surface of the photosensitive drum 12. The solid line is the temperature distribution according to each embodiment described above, and the dashed line is the temperature distribution of the conventional one. As can be seen from this graph, the temperature at the central portion in the longitudinal direction of the photosensitive drum 12 is conventionally about 10 ° C. higher than room temperature (RT), but according to the present invention, it is only slightly higher by 2 ° C. A substantially uniform temperature distribution was obtained in the longitudinal direction of the photosensitive drum 12.

[0101]

As described above, in the image forming apparatus of the present invention, the width of the opening formed in the partition wall and the size of the eaves are changed, and the air duct is provided. A substantially uniform temperature distribution is obtained in the longitudinal direction.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a transfer guide unit and a photosensitive drum of a copying machine according to a first embodiment of the image forming apparatus of the present invention.

FIG. 2 is a perspective view showing a transfer guide section and a photosensitive drum of a copying machine according to a second embodiment of the image forming apparatus of the present invention.

FIG. 3 is a perspective view illustrating a transfer guide unit and a photosensitive drum of a copying machine according to a third embodiment of the image forming apparatus of the present invention.

FIG. 4 shows a fourth embodiment of the image forming apparatus of the present invention.
It is a front view of the state where the 2nd eaves are open.

FIG. 5 shows a fourth embodiment of the image forming apparatus of the present invention.
It is a front view in the state where the 2nd eaves were closed.

FIG. 6 is a perspective view illustrating a transfer guide section and a photosensitive drum of a copying machine according to a fifth embodiment of the image forming apparatus of the present invention.

FIG. 7 shows a sixth embodiment of the image forming apparatus of the present invention.
It is a perspective view in the state where the central part opening was open.

FIG. 8 shows a sixth embodiment of the image forming apparatus of the present invention.
It is a perspective view in the state where the central part opening was closed.

FIG. 9 shows a seventh embodiment of the image forming apparatus of the present invention.
It is a perspective view of the state before an eave moves.

FIG. 10 is a perspective view showing a seventh embodiment of the image forming apparatus according to the present invention, in a state after an eave has moved.

FIG. 11 is a front view of a partition wall provided with an air duct, showing an eighth embodiment of the image forming apparatus of the present invention.

FIG. 12 is a front view of a partition wall provided with an air duct, showing a ninth embodiment of the image forming apparatus of the present invention.

FIG. 13 is a front view of a partition wall provided with an air duct, showing a tenth embodiment of the image forming apparatus of the present invention.

FIG. 14 is a front view of a partition wall provided with an air duct, showing an eleventh embodiment of the image forming apparatus of the present invention.

FIG. 15 is a perspective view showing a transfer guide section and a photosensitive drum of a copying machine according to a twelfth embodiment of the present invention.

FIG. 16 is a graph showing a comparison between a temperature distribution in a longitudinal direction of a photosensitive drum according to an embodiment of the present invention and a temperature distribution according to a conventional technique.

FIG. 17 is a schematic view showing a conventional copying machine.

18 is a perspective view showing a lower part of a photosensitive drum of the copying machine shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Copier 12 Photosensitive drum 102,112,132,142,162,182,2
02, 212, 222, 242, 252, 282 Partition wall 104 Dew condensation prevention heater 106, 114, 118, 136, 144, 148, 1
64, 170, 184a, 184b, 204, 214,
228, 230244, 254, 256, 258284
Openings 108, 122, 138, 146, 166, 172, 1
74, 186, 206 Eaves 218, 234, 248, 262, 264, 266 Air duct 288 Opening variable member

Claims (13)

[Claims] 1. A photosensitive drum on which an electrostatic latent image is formed, a transfer guide for guiding a recording medium to a transfer area for transferring the electrostatic latent image to the recording medium, and a transfer guide below the photosensitive drum and the transfer guide. An image forming apparatus that extends in the longitudinal direction of the photosensitive drum and partitions an atmosphere around the photosensitive drum into a portion close to the photosensitive drum and a portion far from the photosensitive drum, wherein the image forming apparatus forms an image on a recording medium. Of the wall surfaces, a dew condensation prevention heater for preventing dew condensation on the photosensitive drum is provided on a wall surface on a side farther from the photosensitive drum and disposed at a central portion in a longitudinal direction of the photosensitive drum. Extending in the longitudinal direction above the dew condensation preventing heater, the area at both ends in the longitudinal direction is larger than the area at the central part,
An image forming apparatus, wherein at least one opening for guiding heat generated by the condensation prevention heater to the photosensitive drum is formed. 2. A photosensitive drum on which an electrostatic latent image is formed, a transfer guide for guiding a recording medium to a transfer area for transferring the electrostatic latent image onto a recording medium, and a transfer guide below the photosensitive drum and the transfer guide. An image forming apparatus that extends in the longitudinal direction of the photosensitive drum and partitions an atmosphere around the photosensitive drum into a portion close to the photosensitive drum and a portion far from the photosensitive drum, wherein the image forming apparatus forms an image on a recording medium. Of the wall surfaces, a dew condensation prevention heater for preventing dew condensation on the photosensitive drum is provided on a wall surface on a side farther from the photosensitive drum and disposed at a central portion in a longitudinal direction of the photosensitive drum. At least one opening extending in the longitudinal direction above the dew condensation prevention heater and guiding heat generated by the dew condensation prevention heater to the photosensitive drum; and a partition wall formed at an upper end of the opening. An eaves having a larger area at both ends in the longitudinal direction than an area at a center. 3. The partition wall has at least two openings vertically separated from each other, and an upper end of the upper opening is formed with a wider eave than an upper end of the lower opening. The image forming apparatus according to claim 2, wherein: 4. A photosensitive drum on which an electrostatic latent image is formed, a transfer guide for guiding a recording medium to a transfer area for transferring the electrostatic latent image to a recording medium, and a transfer guide below the photosensitive drum and the transfer guide. An image forming apparatus that extends in the longitudinal direction of the photosensitive drum and partitions an atmosphere around the photosensitive drum into a portion close to the photosensitive drum and a portion far from the photosensitive drum, wherein the image forming apparatus forms an image on a recording medium. Of the wall surfaces, a dew condensation prevention heater for preventing dew condensation on the photosensitive drum is provided on a wall surface on a side farther from the photosensitive drum and disposed at a central portion in a longitudinal direction of the photosensitive drum. At least one of heat guides extending from the central portion in the longitudinal direction to both ends above the dew condensation prevention heater, the heat generated by the dew condensation prevention heater being guided to the photosensitive drum.
An image forming apparatus, comprising: an opening; and an eave formed at an upper end of the opening and extending along the opening. 5. A photosensitive drum on which an electrostatic latent image is formed, a transfer guide for guiding a recording medium to a transfer area for transferring the electrostatic latent image onto a recording medium, and a transfer guide below the photosensitive drum and the transfer guide. An image forming apparatus that extends in the longitudinal direction of the photosensitive drum and partitions an atmosphere around the photosensitive drum into a portion close to the photosensitive drum and a portion far from the photosensitive drum, wherein the image forming apparatus forms an image on a recording medium. Of the wall surfaces, a dew condensation prevention heater for preventing dew condensation on the photosensitive drum is provided on a wall surface on a side farther from the photosensitive drum and disposed at a central portion in a longitudinal direction of the photosensitive drum. At least one opening that extends in the longitudinal direction above the dew condensation preventing heater and guides heat generated by the dew condensation preventing heater to the photosensitive drum is formed. An image forming apparatus comprising a breadth that having an opening size varying means for varying at said longitudinal center portion and both end portions. 6. The opening width varying means includes a shape memory element that varies the width of the opening between the center and both ends in the longitudinal direction according to temperature. The image forming apparatus according to claim 5, wherein: 7. A photosensitive drum on which an electrostatic latent image is formed, a transfer guide for guiding a recording medium to a transfer area for transferring the electrostatic latent image to the recording medium, and a transfer guide below the photosensitive drum and the transfer guide. An image forming apparatus that extends in the longitudinal direction of the photosensitive drum and partitions an atmosphere around the photosensitive drum into a portion close to the photosensitive drum and a portion far from the photosensitive drum, wherein the image forming apparatus forms an image on a recording medium; Of the wall surfaces, a dew condensation prevention heater for preventing dew condensation on the photosensitive drum is provided on a wall surface on a side farther from the photosensitive drum and disposed at a central portion in a longitudinal direction of the photosensitive drum. At least one opening extending in the longitudinal direction above the dew condensation prevention heater and guiding heat generated by the dew condensation prevention heater to the photosensitive drum; and a partition wall formed at an upper end of the opening. The eaves extending along the opening is formed, and further provided is an eaves width changing means for making the eaves width different between the central portion and both end portions in the longitudinal direction. An image forming apparatus comprising: 8. The eaves width varying means includes a shape memory element that varies the width of the eaves at the center and both ends in the longitudinal direction according to temperature. Item 8. The image forming apparatus according to Item 7. 9. A photosensitive drum on which an electrostatic latent image is formed, a transfer guide for guiding a recording medium to a transfer area for transferring the electrostatic latent image to a recording medium, and a transfer guide below the photosensitive drum and the transfer guide. An image forming apparatus that extends in the longitudinal direction of the photosensitive drum and partitions an atmosphere around the photosensitive drum into a portion close to the photosensitive drum and a portion far from the photosensitive drum, wherein the image forming apparatus forms an image on a recording medium; Of the wall surfaces, a dew condensation prevention heater for preventing dew condensation on the photosensitive drum is provided on a wall surface on a side farther from the photosensitive drum and disposed at a central portion in a longitudinal direction of the photosensitive drum. At least one opening extending in the longitudinal direction above the dew condensation prevention heater and guiding heat generated by the dew condensation prevention heater to the photosensitive drum; and a partition wall formed at an upper end of the opening. The eaves extending along the opening are formed, and the width of the opening and / or the width of the eaves are different between the central portion and the both ends in the longitudinal direction. An image forming apparatus comprising variable means. 10. A photosensitive drum on which an electrostatic latent image is formed,
A transfer guide that guides the recording medium to a transfer area where the electrostatic latent image is transferred to the recording medium, and an atmosphere around the photosensitive drum that extends in a longitudinal direction of the photosensitive drum below the photosensitive drum and the transfer guide. An image forming apparatus for forming an image on a recording medium, comprising a partition wall for partitioning a portion closer to the photosensitive drum and a portion farther from the photosensitive drum, wherein, among the wall surfaces of the partition wall, A dew condensation prevention heater for preventing dew condensation on the photosensitive drum, which is disposed at a central portion in a longitudinal direction of the drum, wherein the partition wall extends in the longitudinal direction above the dew condensation prevention heater and has both ends in the longitudinal direction. At least one opening having an area larger than the area at the center is formed at the portion, and the dew condensation preventing heater is substantially sealed. An image forming apparatus comprising an air duct connected to the opening. 11. A photosensitive drum on which an electrostatic latent image is formed,
A transfer guide that guides the recording medium to a transfer area where the electrostatic latent image is transferred to the recording medium, and an atmosphere around the photosensitive drum that extends in a longitudinal direction of the photosensitive drum below the photosensitive drum and the transfer guide. An image forming apparatus for forming an image on a recording medium, comprising a partition wall for partitioning a portion closer to the photosensitive drum and a portion farther from the photosensitive drum, wherein, among the wall surfaces of the partition wall, A dew condensation preventing heater for preventing dew condensation on the photosensitive drum is provided at a central portion in a longitudinal direction of the drum, and the partition wall is formed at a central portion in the longitudinal direction above the dew condensation preventing heater, One having a central opening for guiding the heat generated by the dew condensation prevention heater to the photosensitive drum, and both end openings formed at both ends in the longitudinal direction above the dew condensation prevention heater. There further image forming apparatus comprising the air duct by connecting the said and the dew condensation prevention heater openings at both ends. 12. A photosensitive drum on which an electrostatic latent image is formed;
A transfer guide that guides the recording medium to a transfer area where the electrostatic latent image is transferred to the recording medium; and An image forming apparatus for forming an image on a recording medium, comprising a partition wall for partitioning a portion closer to the photosensitive drum and a portion farther from the photosensitive drum, wherein, of the wall surfaces of the partition wall, A dew condensation prevention heater for preventing dew condensation on the photosensitive drum, which is disposed at a central portion in a longitudinal direction of the drum, wherein the partition wall extends in the longitudinal direction above the dew condensation prevention heater and has both ends in the longitudinal direction. At least one opening having an area equal to the area at the center and the area at the center is further formed. An image forming apparatus comprising an air duct connected to the opening. 13. A photosensitive drum on which an electrostatic latent image is formed;
A transfer guide that guides the recording medium to a transfer area where the electrostatic latent image is transferred to the recording medium; and An image forming apparatus that includes a partition wall that separates a portion close to the photosensitive drum and a portion that is far from the photosensitive drum, and that forms an image on a recording medium. A dew condensation prevention heater for preventing dew condensation on the photosensitive drum, the dew condensation prevention heater being disposed on a wall surface on a side remote from the photosensitive drum and in a longitudinal central portion of the photosensitive drum; At least one opening that extends in the longitudinal direction above the heater and guides heat generated by the dew condensation prevention heater to the photosensitive drum; Based on the measured temperature in Joki, the image forming apparatus characterized by comprising adjustment means for adjusting the amount of the heat which leads to the opening.