JP5098952B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus, and more particularly to a technique for effectively cooling the inside of the apparatus.

An electrophotographic image forming apparatus scans a photosensitive drum with laser light emitted from an exposure unit to form an electrostatic latent image, and forms a toner image by developing the electrostatic latent image. The toner image on the photosensitive drum is transferred to a recording sheet and then thermally fixed at a fixing unit.
In such an image forming apparatus, the in-machine temperature tends to increase due to the heat of the fixing unit. However, if the in-machine temperature increases more than necessary, the image process conditions may change and the image quality may deteriorate. As a result, deterioration of members having low heat resistance progresses and the life of the apparatus is shortened.

Therefore, conventionally, the fixing unit is arranged as much as possible in the corner of the machine, and an exhaust port is provided in the vicinity of the fixing unit, and the fan is attached to the exhaust port to cool the interior.
However, the above configuration is not sufficient to suppress the temperature rise in other parts of the machine. In particular, a plurality of photosensitive drums are arranged along the running direction of the intermediate transfer belt, and toner images of different colors formed by the photosensitive drums are transferred onto the intermediate transfer belt to form a color toner image. In the so-called tandem type image forming apparatus, the optical elements such as the scanning lens are thermally expanded as the temperature in the exposure unit is increased due to the heat generated by the polygon motor or the laser diode, which causes color misregistration. Therefore, for example, in Patent Document 1, an exhaust port is also provided in the vicinity of the exposure scanning unit, and cooling is performed by another fan device.
Japanese Patent Laid-Open No. 2004-361792

However, according to the configuration of Patent Document 1, since the positions of the plurality of fan devices are in the vicinity of the exhaust port, there is a problem that driving sounds such as wind noises and motor sounds leak to the outside.
On the other hand, it is understood that the thermal expansion of the intermediate transfer belt also affects the occurrence of the color misregistration. However, as the image forming apparatus becomes more compact, the distance between the fixing unit and the intermediate transfer belt in the machine becomes smaller. Therefore, the intermediate transfer belt is easily affected by the temperature of the fixing unit, and in the case of a model having a double-sided printing function, the temperature is increased due to thermal fixing when an image is formed on the first surface. When the recording sheet is secondarily transferred to the second surface, heat is applied to the intermediate transfer belt. Therefore, it is desirable to efficiently cool the intermediate transfer belt.

  The present invention has been made in view of the above circumstances, and effectively cools the periphery of the exposure unit, the intermediate transfer member, and the fixing device without providing a fan device at a plurality of locations, and is excellent in quietness. An object is to provide an image forming apparatus.

To solve the above problem, an image forming apparatus according to the present onset Ming, an exposure unit for forming an electrostatic latent image by exposing and scanning the surface of the image bearing member, unfixed toner to develop the electrostatic latent image An image forming developing unit, a transfer unit for transferring the unfixed toner image to an intermediate transfer member, and then transferring the image onto a recording sheet; and an unfixed toner image transferred on the recording sheet for heat fixing an image forming apparatus having a fixing unit, the air flowing from the outside of the machine is, the via exposed portions of some of said intermediate transfer member after I proceeds along the front side, of the fixing portion A ventilation path is formed so as to be discharged to the outside of the apparatus again through the periphery of the housing, and an air flow in the direction from the exposure section to the fixing section is generated on the way from the exposure section to the fixing section of the ventilation path. and a fan device is provided to generate said intermediate transfer member, first and second An endless belt stretched substantially horizontally by a roller, wherein an exposure unit is disposed so as to face a surface of a lower traveling unit of the endless belt via the image carrier, and an upper side of the endless belt. A fixing unit is disposed in the vicinity of a portion of the traveling unit that is wound around the first roller, and the airflow path is configured such that the airflow is generated on the surface of the traveling unit below the endless belt and the exposure unit. U-turns at the portion of the endless belt wound around the second roller and traveling from the first roller side to the second roller side between the housing and the inside of the exposure portion housing And it is characterized by including the folding | returning path | route which guides so that it may advance along the surface of the upper running part of an endless belt .

According to the above configuration, the fan device is provided in the middle of the ventilation path from the exposure unit to the fixing unit, and is located away from the air intake and exhaust ports. Etc. are less likely to leak out of the apparatus and have excellent quietness, and the periphery of the exposure unit, the intermediate transfer member, and the fixing device can be effectively cooled only by the fan device .

In other words, the fan device is provided between the exposure unit on the ventilation path and a part of the surface of the intermediate transfer member, and is located further away from the exhaust port. It is hard to leak from the mouth .

Since the ventilation path has a U-turn, the distance of the ventilation path can be set longer even in a small space machine, so that the fan device can be easily moved away from the intake position and the exhaust position, and the noise can be further reduced.
Moreover, it is preferable that the fan device is disposed in a U-turn portion in the folding path.

Here, before SL and the developing unit is provided at a position adjacent to the exposure unit, the ventilation path may include a path between the developing unit and the exposure unit.
In the developing unit, new toner is supplied as the toner is consumed. Here, when the supplied toner is stirred and mixed, heat may be generated. This heat generation generates toner condensate and causes development failure.

  Since the ventilation path includes a path between the exposure unit and the development unit, it is possible to prevent overheating of the development unit and to suppress development failure.

FIG. 1 is a schematic cross-sectional view illustrating a configuration of a printer 1 according to the present embodiment.
As shown in the figure, the printer 1 includes an image processing unit 3, a feeding unit 4, a fixing unit 5, a blower unit 14, a control unit 7, and the like, and is connected to a network such as a LAN and connected to an external terminal. When an execution instruction for a print job is received from an apparatus (not shown), color image formation including yellow, magenta, cyan, and black is executed based on the instruction.

Here, the reproduction colors of yellow, magenta, cyan, and black are represented as Y, M, C, and K, and Y, M, C, and K are added as subscripts to numbers associated with the reproduction colors.
A temperature sensor 8 composed of a thermistor or the like is provided below the fixing unit 5, and the temperature detected here is used for temperature control in the machine as a representative value of the machine temperature.
The contents of the temperature control in the machine will be described later.

The image processing unit 3 includes image forming units 3Y, 3M, 3C, and 3K corresponding to Y to K colors, an exposure unit 10, an intermediate transfer belt 11, toner storage units 20Y, 20M, 20C, and 20K. .
The image forming unit 3Y includes a photosensitive drum 31, a charger 32, a developing device 33, a primary transfer roller 34, a cleaner 35 for cleaning the photosensitive drum 31, and the like disposed around the photosensitive drum 31. A Y-color toner image is formed on the drum 31. The other image forming units 3M to 3K have the same configuration as the image forming unit 3Y, and the reference numerals are omitted in FIG.

The toner storage units 20Y to 20K are containers for storing Y to K color replenishment toner called so-called hoppers, and supply the toner to the developing devices 33 of the image forming units 3Y to 3K as necessary.
The exposure unit 10 includes a light emitting element such as a laser diode, a polygon mirror, a motor (not shown) that rotates the polygon mirror, and the like, and a laser for exposing and scanning the photosensitive drum 31 of the image forming units 3Y to 3K. Light L is emitted.

The intermediate transfer belt 11 is an endless belt. The intermediate transfer belt 11 is stretched substantially horizontally by the driving roller 12 and the driven roller 13 and circulates in the direction of arrow A.
The fixing unit 5 is rotatably driven by a motor (not shown) in pressure contact with the fixing roller 5a by a rotatable fixing roller 5a heated by a heat source such as a halogen heater 5c and a pressure mechanism such as a spring. It consists of a pressure roller 5b and the like.

The feeding unit 4 includes a paper feed cassette 41 that stores a recording sheet S as a recording sheet, a feeding roller 42 that feeds the recording sheets S in the paper feeding cassette 41 one by one onto the conveyance path 43, and a fed recording. A timing roller pair 44 for taking the timing of feeding the sheet S to the secondary transfer position 46, a secondary transfer roller 45, and the like are provided.
The exposure unit 10 emits laser light L for image formation of Y to K colors in response to a drive signal from the control unit 7, and exposes and scans the photosensitive drums 31 of the image forming units 3Y to 3K. By this exposure scanning, an electrostatic latent image is formed on the photosensitive drum 31 uniformly charged by the charger 32 for each of the image forming units 3Y to 3K. Each electrostatic latent image is visualized with negatively charged toner by the developing device 33, and Y to K color toner images are formed on the respective photosensitive drums 31.

  The toner images of the respective colors are sequentially transferred onto the intermediate transfer belt 11 by electrostatic force acting on the primary transfer roller 34. At this time, the image forming operations for the respective colors are executed at different timings so that the toner images are primarily transferred at the same position on the intermediate transfer belt 11. Each color toner image superimposed on the intermediate transfer belt 11 moves toward the secondary transfer position 46 by the circular movement of the intermediate transfer belt 11 in the direction of arrow A. Hereinafter, the direction of arrow A is referred to as a belt rotation direction.

  On the other hand, the recording sheet S is fed from the feeding unit 4 via the timing roller pair 44 in accordance with the timing at which the superimposed color toner images move to the secondary transfer position 46. S is sandwiched and conveyed between the intermediate transfer belt 11 and the secondary transfer roller 45 that make a circular motion, and the electrostatic force acting between the intermediate transfer belt 11 and the secondary transfer roller 45 causes the S on the intermediate transfer belt 11. The toner images are secondarily transferred onto the recording sheet S at once.

The recording sheet S that has passed the secondary transfer position 46 is conveyed to the fixing unit 5, and after the toner image (unfixed image) on the recording sheet S is fixed to the recording sheet S by heating and pressing in the fixing unit 5, The paper is discharged onto a discharge tray 72 via a discharge roller pair 71.
<Configuration of blower unit 14>
The blower unit 14 generates an air flow from the exposure unit 10 toward the fixing unit 5 and disperses the air flow in a direction (Y-axis direction) orthogonal to the XZ plane of the air flow. As shown in FIG.

FIG. 2 is a schematic configuration diagram showing the configuration of the blower unit 14, and FIG. 3 is a BB ′ cross section in FIG. 2.
As shown in FIG. 2, the air blowing unit 14 includes a fan device 115 and a duct 114.
The duct 114 has a rectangular tube-shaped fan guide portion 114a covering the outer periphery of the fan device 115, and a width of about 180 in the X-axis direction as shown in FIG. 3 while expanding the width in the Y-axis direction as shown in FIG. It has a U-turn part 114b that turns around and an opening 114c at the tip.

The fan device 115 includes a fan 115b that is rotationally driven by a motor 115a provided at the center.
The motor 115a is turned on / off in accordance with an instruction from the controller 7, and is fixed to a seat 114d at the center of the fan guide 114a.
<About ventilation path 6>
Returning to FIG. 1, the blower unit 14 is provided around the driven roller 13 as described above, and forms a part of the ventilation path 6 that guides the airflow for cooling the inside of the machine.

The ventilation path 6 is not a ventilation path formed by intentionally providing a duct except for the portion of the blower unit 14. For example, a machine frame such as the image processing unit 3, the feeding unit 4, and the fixing unit 5, or an intermediate frame A gap formed between the transfer belt 11 and the transfer belt 11 is utilized.
But you may provide a duct in the location which wants to improve airtightness except the periphery part of cooling object.

The negative pressure side of the ventilation path 6, that is, the path upstream of the blower unit 14, is a path 61 passing through the inside of the feeding unit 4 from the inlet 2 a provided near the feeding unit 4 of the housing 2, After that, it consists of two branch paths that branch in two directions and merge immediately before the blower unit 14.
More specifically, one of these branch paths enters the inside of the exposure unit 10 through an opening provided in the frame (housing) of the exposure unit 10, advances through the frame of the exposure unit 10, and The path 62 reaches the blower unit 14 after moving from another opening provided in the machine frame to the outside of the machine frame, and the other proceeds along the outer surface of the machine frame of the exposure unit 10 to the blower unit 14. This is a route 63 to reach.

Here, the path 63 includes a path between the exposure unit 10 and the adjacent image processing unit 3, that is, a path along the upper outer surface of the exposure unit 10. Therefore, not only overheating of the exposure unit 10 but also overheating of the image processing unit 3 can be prevented by the airflow in the path 63.
In addition, the air blowing unit 14 located in the transition section between the negative pressure side and the positive pressure side of the ventilation path 6 has a sudden pressure fluctuation from negative pressure to positive pressure inside, and as described above, the positive pressure side. Is turned about 180 degrees in the X-axis direction.

Further, the positive pressure side path of the ventilation path 6 includes a path 64 extending from the blower unit 14 along the upper surface of the intermediate transfer belt 11 and then two branch paths heading in different directions.
More specifically, one of these branch paths is a path 65 that extends upward (Z direction) between the fixing unit 5 and the toner storage unit 20K and extends from the exhaust port 2c to the outside of the apparatus. The other path 66 has a smaller ventilation resistance than the path 65, which passes between the fixing section 5 and the intermediate transfer belt 11 and extends from the exhaust port 2 b provided near the fixing section 5 of the housing 2 to the outside of the apparatus. It has become.

The path 66 is temporarily blocked when the recording sheet S passes through the secondary transfer position 46 and when the recording sheet S passes through the reverse path 47 during double-sided printing, but leads to the outside of the apparatus. The presence of the path 65 prevents the motor 115a from being overloaded.
In the path 65, even when the path 66 is not blocked, an airflow is flowing, and this airflow prevents heat conduction between the fixing unit 5 and the toner storage unit 20K. 20K is hard to be heated.

Similarly, the air flow is flowing through the path 66 except for a case where it is temporarily blocked for the above-described reason, and this air flow prevents heat conduction between the fixing unit 5 and the intermediate transfer belt 11. The intermediate transfer belt 11 is not easily heated.
Note that the flow velocity of the airflow in the path 66 is about 1 m / s. If the airflow is at this level, the image quality is not affected even if the unfixed toner image is sprayed onto the transferred recording sheet S.

In addition, the airflow flowing through the path 64 flows in a direction (counter direction) that is opposite to the circumferential direction of the intermediate transfer belt 11, and heat exchange is performed with the surface of the intermediate transfer belt 11. Since the counter direction is higher than the counter direction, it is desirable that the air flow is made to flow in the counter direction with respect to the intermediate transfer belt 11.
<Configuration of control unit 7>
FIG. 4 is a functional block diagram showing the contents of the control unit 7.

The control unit 7 mainly includes a CPU 171, an interface (I / F) unit 172, a RAM 173, a ROM 174, and an EEPROM 175, and is electrically connected to the exposure unit 10, the image processing unit 3, the fixing unit 5, the temperature sensor 8, the fan device 115, and the like. Connected.
The interface unit 172 is a LAN card, a LAN board, or the like for connecting the CPU 171 and a network such as a LAN. The interface unit 172 receives a print job transmitted from a client terminal via the LAN or the like and sends it to the CPU 171.

A RAM (Random Access Memory) 173 is a volatile memory and serves as a work area when the CPU 171 executes a program.
A ROM (Read Only Memory) 174 stores various programs such as a program related to print processing in the image forming unit 20 and a program related to image stabilization processing.

An EEPROM (Electronically Erasable and Programmable Read Only Memory) 175 is a non-volatile memory and serves as a data storage area when the CPU 171 executes a program.
The control unit 7 converts an image signal from an external terminal device into a digital signal for Y to K colors, generates a drive signal for driving the light emitting element of the exposure unit 10, and the like to perform an image forming operation. In addition to controlling a series of processes related to the above, a process for suppressing the temperature rise in the machine (hereinafter referred to as “temperature control process”) is performed.

Hereinafter, the operation of the temperature control process in the control unit 7 will be described.
<Temperature control process>
FIG. 5 is a flowchart showing the contents of a subroutine of the temperature control process executed by the control unit 7 according to the present embodiment, and the CPU 171 executes the following contents.
First, it is determined whether or not the temperature detected by the temperature sensor 8 exceeds a value obtained by subtracting β from a predetermined temperature α (step S100).

Here, the predetermined temperature α is a target upper limit value of the in-machine temperature, and β is a target upper limit value of the in-machine temperature due to a time lag from when the fan device 115 is turned on until the in-machine cooling is started. This is a correction value provided to prevent overshoot.
If the temperature detected by the temperature sensor 8 exceeds the value obtained by subtracting β from the predetermined temperature α (step S100: YES), the fan device 115 is in a driving state because the inside of the apparatus tends to rise in temperature (step S101). ), The process returns to the first step S100 of this subroutine.

On the other hand, when the temperature detected by the temperature sensor 8 does not exceed the value obtained by subtracting β from the predetermined temperature α (step S100: NO), the temperature detected by the temperature sensor 8 is changed from the predetermined temperature α to γ. It is determined whether it is below the value obtained by subtracting (step S102).
Here, γ is a value set to be larger than β by several degrees, and the value of γ−β is a so-called differential value. By providing such a differential value, the chattering of the fan device 115 is performed. Is preventing.

If the temperature detected by the temperature sensor 8 is lower than the value obtained by subtracting γ from the predetermined temperature α (step S102: YES), the internal temperature tends to decrease, so the fan device 115 is stopped ( Step S103), the process returns to the first step S100 of this subroutine.
If the temperature detected by the temperature sensor 8 is not lower than the value obtained by subtracting γ from the predetermined temperature α (step S102: NO), the in-machine temperature t is α−γ ≦ t ≦ α−β. Since there is a relationship and it is in the transitional period of the condition judgment, nothing is done and the process returns to the first step S100 of this subroutine.

  As described above, in the present embodiment, the blower unit 14 travels along the upper surface of the intermediate transfer belt 11 via the exposure unit 10 having a heat source such as a polygon mirror driving motor, and has the highest temperature. Since it is provided in the middle of the ventilation path 6 formed so as to extend from the exhaust port 2b to the outside of the apparatus after moving in the direction in which the fixing unit 5 becomes higher, it is away from the intake port 2a and the exhaust port 2b. Wind noise and motor noise of the fan device 115 are difficult to leak outside the machine, and noise is hardly generated.

Furthermore, since the two cooling objects on the upper surface of the exposure unit 10 and the intermediate transfer belt 11 can be cooled at once by one fan device 115, it is possible to contribute to power saving.
<Modification>
(1) In the said embodiment, although the ventilation unit 14 had one fan apparatus 115, it may have not only this but two or more fan apparatuses.

Even in such a case, since the positions of these fan devices are far from the intake and exhaust ports, the sound of the fan devices leaks to the outside as compared with the case where the same number of fan devices is provided as in the past. Difficult to contribute to noise reduction.
(2) In the above-described embodiment, the printer 1 is provided with the intake port 2a. However, such an intake port 2a is not necessarily provided. You may make it the structure which does not raise airtightness and breathes in outside air naturally.
(3) Furthermore, in the above embodiment, the printer 1 has the path 61 passing through the inside of the feeding unit 4, but it is not always necessary to provide the path 61 and flow the airflow on the recording sheet S. For example, an air inlet may be provided in part C of FIG. 1 so that airflow does not flow into the path 61.
(4) Further, in the above embodiment, the printer 1 advances in the machine frame of the exposure unit 10 and advances along the path 62 to the blower unit 14 and the upper outer surface of the machine frame of the exposure unit 10. Although a branch path that branches to the path 63 leading to the unit 14 is provided, it is not always necessary to provide a branch path as long as a cooling effect can be obtained, and only one of the paths may be provided.
(5) In the above embodiment, the intermediate transfer belt 11 is stretched substantially horizontally by the drive roller 12 and the driven roller 13, but it does not have to be stretched horizontally as described above. Furthermore, an intermediate transfer drum may be provided instead of the intermediate transfer belt 11.

When an intermediate transfer drum is provided, the path 64 may be formed along a partial surface of the arc-shaped intermediate transfer drum.
(6) In the above embodiment, the toner image is transferred to the recording sheet S by the secondary transfer. However, the present invention is not limited to this, and as disclosed in Japanese Patent Application Laid-Open No. 2004-361792, the photosensitive member is used. The toner image may be sequentially transferred to the belt, the intermediate transfer drum, and the recording sheet S, that is, the toner image may be transferred to the recording sheet S by tertiary transfer.

As described above, since there are various variations in the configuration of the image forming apparatus, it is considered that there are various variations in the position of the fixing unit. There is no doubt that it is provided in the vicinity of a transfer portion such as a transfer roller for transferring to an intermediate transfer member or an intermediate transfer member (hereinafter referred to as “final intermediate transfer member”) facing the transfer portion.
Therefore, when there are a plurality of intermediate transfer members, it is desirable to actively cool the final intermediate transfer member that is susceptible to the heat of the fixing unit.
(7) In the above embodiment, an example in which the image forming apparatus according to the present invention is applied to a tandem color digital printer has been described. However, the present invention is not limited to this. Regardless of color or monochrome image formation, a toner image formed on an image carrier such as a photosensitive drum is transferred to an intermediate transfer member such as an intermediate transfer belt, and the toner image transferred onto the intermediate transfer member is recorded on a recording sheet. Any image forming apparatus that transfers and forms an image can be applied to, for example, a copying machine, a FAX, and an MFP (Multiple Function Peripheral).

  The contents of the above embodiment and the above modification may be combined.

  The present invention can be widely applied to an image forming apparatus having an intermediate transfer member such as an intermediate transfer belt, and an exposure unit and a fixing unit.

1 is a schematic cross-sectional view illustrating a configuration of a printer according to an embodiment. It is a schematic block diagram which shows the structure of the ventilation unit which concerns on this Embodiment. It is a cross-sectional view of the blower unit according to the present embodiment. It is a functional block diagram which shows the content of the control part which concerns on this Embodiment. It is a flowchart which shows the content of the subroutine of the temperature control process performed with the control part which concerns on this Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Printer 2 Case 2a Intake port 2b Exhaust port 2c Exhaust port 3 Image process part 3Y, 3M, 3C, 3K Image forming part 4 Feeding part 5 Fixing part 6 Ventilation path 8 Temperature sensor 10 Exposure part 11 Intermediate transfer belt 12 Drive Roller 13 Followed roller 14 Blower unit 20Y, 20M, 20C, 20K Toner storage unit 20 Image forming unit 31 Photosensitive drum 33 Developer 41 Paper feed cassette 47 Reverse path 71 Discharge roller pair

Claims (3)

An exposure unit that exposes and scans the surface of the image carrier to form an electrostatic latent image, a developing unit that develops the electrostatic latent image to form an unfixed toner image, and an intermediate transfer of the unfixed toner image once An image forming apparatus comprising: a transfer portion that is transferred to a recording sheet and then transferred onto a recording sheet; and a fixing portion that thermally fixes an unfixed toner image transferred onto the recording sheet.
The air flowing from outside the apparatus travels along the surface of a part of the intermediate transfer member via the exposure unit, and is then discharged again outside the periphery of the fixing unit housing. And form a ventilation path as
A fan device that generates an airflow in a direction from the exposure unit to the fixing unit is provided in the middle of the ventilation path from the exposure unit to the fixing unit.
The intermediate transfer member is an endless belt stretched substantially horizontally by first and second rollers, and an exposure unit is disposed so as to face a surface of a traveling portion below the endless belt via the image carrier. And a fixing unit is disposed in the vicinity of a portion of the upper traveling portion of the endless belt that is wound around the first roller.
In the ventilation path, the air current flows between the surface of the lower running portion of the endless belt and the housing of the exposure unit or inside the housing of the exposure unit from the first roller side to the second roller side. And a turn-back path that guides the U-turn at the portion of the endless belt wound around the second roller and advances along the surface of the upper running portion of the endless belt. Image forming apparatus. The image forming apparatus according to claim 1 , wherein the fan device is disposed in a U-turn portion in the folding path. And wherein the developing unit is provided at a position adjacent to the exposed portion, the ventilation path image according to claim 1 or 2, Tokute' that it contains a path between the developing unit and the exposure unit Forming equipment.

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