JP7310431B2 - image forming device - Google Patents

Description

The present invention relates to an image forming apparatus.

2. Description of the Related Art An electrophotographic image forming apparatus includes a fixing device for fixing a toner image onto a sheet as a recording medium by applying heat and pressure. As a technique related to such an image forming apparatus, Japanese Patent Application Laid-Open No. 2002-200002 discloses that a heat insulating duct is provided between a fixing device and an image forming section to prevent heat generated from the fixing device from reaching the image forming section. is disclosed. In this case, by providing a plurality of openings in the heat insulating duct, the air sent into the heat insulating duct can be discharged to the cleaner provided in the image forming section, thereby cooling the cleaner and the intermediate transfer body. It is said that it can be expected (see Patent Document 1 below).

JP 2018-180452 A

By the way, in recent years, the number of sheets on which an image can be formed per unit time tends to increase in an image forming apparatus. For this reason, before the heated sheet and toner that have passed through the fixing device are cooled, the next sheet that has passed through the fixing device is stacked, and toner transfer between sheets, so-called tacking, occurs. becomes easier. In order to prevent tacking, an air supply fan is additionally provided for blowing air to cool the sheet that has passed through the fixing device.

However, when an air supply fan for taking in cooling air is added to the inside of the image forming apparatus, the inside of the apparatus is pressurized, heat stays inside the apparatus, and the temperature rises. This temperature rise causes damage to parts inside the apparatus and melting of toner in the image forming unit.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an image forming apparatus capable of preventing the temperature inside the housing from rising by exhausting the heat without allowing the heat to stay in the housing.

In order to achieve such an object, the present invention provides a sheet nipped between a transfer belt having an image bearing surface on which a toner image is formed, and the image bearing surface of the transfer belt disposed below the transfer belt. a secondary transfer roller for transferring the toner image onto the transfer belt; a cleaning unit for removing toner from the image bearing surface of the transfer belt; and a housing that houses the transfer belt, the secondary transfer roller, the cleaning unit, and the fixing device, and the top plate of the housing is positioned above the cleaning unit. The image forming apparatus includes an opening, and an exhaust fan provided on the top of the top plate for exhausting air from the housing through the opening.

According to the present invention, it is possible to provide an image forming apparatus capable of preventing temperature rise in the housing by exhausting heat without causing heat to stay in the housing.

1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment viewed from the front side; FIG. 2 is a configuration diagram of the essential parts of the image forming apparatus according to the first embodiment, viewed from the sheet discharge side; FIG. 4A and 4B are diagrams for explaining a control method of the image forming apparatus according to the first embodiment; FIG. 1 is a schematic diagram showing the overall configuration of an image forming apparatus according to a second embodiment; FIG. FIG. 11 is a schematic diagram showing the overall configuration of an image forming apparatus according to a third embodiment;

Hereinafter, each embodiment to which the present invention is applied will be described in detail based on the drawings. In addition, the same code|symbol is attached|subjected to the component which is common in each embodiment, and the overlapping description is abbreviate|omitted.

<<First embodiment>>
-Configuration of image forming apparatus-
FIG. 1 is a schematic configuration diagram of the image forming apparatus 1 according to the first embodiment viewed from the front side [W1]. The front side [W1] is the side facing the operator who operates the image forming apparatus 1 . The image forming apparatus 1 shown in this figure is of an electrophotographic type that forms a toner image on a sheet St as a recording medium. A device 40 and a sheet supply section 50 are provided. The image forming apparatus 1 also includes a plurality of air supply fans Af and a plurality of exhaust fans Ef. Further, the image forming apparatus 1 includes a temperature sensor 60 , a control section 70 connected to these components, and an operation section 80 connected to the control section 70 .

In FIG. 1, the right hand side of the drawing is the sheet supply side [L1], and the left hand side of the drawing is the sheet discharge side [L2]. Here, the sheet ejection side [L2] is the side on which the sheet St is ejected from the housing 100 . The side opposite to the sheet discharge side [L2] is the sheet supply side [L1]. Hereinafter, the details of each member constituting the image forming apparatus 1 will be described in order, starting with the configuration of the housing 100 and the ceiling housing 200 .

<Case 100>
The housing 100 is box-shaped. The box-shaped casing 100 is provided with a door (not shown) on the front side [W1].

A top plate 101 forming a ceiling surface of the housing 100 also serves as a bottom plate of the ceiling housing 200 . Such a top plate 101 partitions between the housing 100 and the ceiling housing 200 . An opening 101a is provided in the top plate 101, and the inside of the housing 100 and the inside of the ceiling housing 200 communicate with each other through the opening 101a. The formation position of the opening 101a in the top plate 101 is preferably above the fixing device 40, which will be described later, and is close to the front side [W1] of the housing 100, for example. The formation position of the opening 101a is assumed to be closer to the front side [W1] than the intermediate position between the front side [W1] and the reverse depth side of the housing 100 .

<Ceiling housing 200>
The ceiling housing 200 is a box-shaped one arranged above the housing 100 . The ceiling housing 200 is arranged at a position covering at least the opening 101 a of the top plate 101 . Such a ceiling housing 200 is composed of an exterior top plate 201 provided to form an internal space with the top plate 101 and an exterior 202 covering the exterior top plate 201 . These exterior top plate 201 and exterior 202 are provided with exhaust holes 200a communicating with the outside.

As a result, the inside of the housing 100 communicates with the outside through the opening 101a of the top plate 101, the inside of the ceiling housing 200, and the exhaust hole 200a. The exhaust hole 200a is located, for example, on the depth side opposite to the front side [W1] of the ceiling housing 200, that is, on the depth side of an intermediate position between the front side [W1] of the housing 100 and the opposite depth side. shall be provided.

<Image forming unit 20>
The image forming section 20 has four image forming units 20y, 20m, 20c, and 20k for forming toner images of yellow (Y), magenta (M), cyan (C), and black (K), for example. . These image forming units 20y, 20m, 20c, and 20k are stacked and arranged in the vertical direction inside the housing 100, and each of the photoreceptor 21 and the charging section 23 and the exposure section 25 arranged around the photoreceptor 21 are arranged. , and a developing section 27 .

Of these, the photosensitive member 21 is in the shape of a drum that is rotated by a drive motor, and the side peripheral surface of the drum shape serves as an image bearing surface on which a toner image is formed. The drum-shaped photoreceptor 21 is arranged substantially horizontally from the front side [W1] of the housing 100 toward the depth direction. Around the photoconductor 21, a charging section 23, an exposure section 25, and a developing section 27 are arranged in this order from the upstream side in the rotation direction of the photoconductor 21. As shown in FIG.

The image bearing surface of the photoreceptor 21 is uniformly charged by the charging unit 23, and an electrostatic latent image is formed on the charged image bearing surface by exposure scanning by the exposure unit 25. FIG. The exposure scanning by the exposure unit 25 is performed, for example, based on image data received from an external device.

The developing unit 27 supplies charged toner to the image bearing surface of the photoreceptor 21 on which the electrostatic latent image is formed, thereby applying toner of each color to the electrostatic latent image formed on the image bearing surface of the photoreceptor 21 . is attached. As a result, a yellow toner image is formed on the image bearing surface 21a of the photosensitive member 21 in the image forming unit 20y, a magenta toner image is formed on the surface of the photosensitive member 21 in the image forming unit 20m, and a magenta toner image is formed on the photosensitive member 21 in the image forming unit 20c. A cyan toner image is formed, and a black toner image is formed on the photosensitive member 21 of the image forming unit 20k.

The image forming units 20y, 20m, 20c, and 20k configured as described above are arranged with the axes of the photosensitive members 21 parallel to each other. In the arranged state, the image bearing surfaces of the photoreceptors 21 are directed in the same direction between the developing section 27 and the charging section 23 of each photoreceptor 21 .

<Transfer section 30>
The transfer section 30 is arranged in parallel with the image forming section 20 within the housing 100 . The transfer section 30 includes an intermediate transfer belt 31 configured as a rotating endless belt, a plurality of rollers 32 inscribed in the intermediate transfer belt 31 , and a primary transfer section 33 . The transfer section 30 also includes a secondary transfer roller 33 a , a neutralization roller 34 and a cleaning unit 35 . These are arranged substantially horizontally from the front side [W1] of the housing 100 toward the depth direction.

Among them, the intermediate transfer belt 31 is arranged so as to rotate in the vertical direction while being stretched over a plurality of rollers 32, and its outer peripheral surface serves as an image bearing surface 31a. Such an intermediate transfer belt 31 rotates in a direction opposite to the rotation of the photoreceptors 21 of the image forming units 20y, 20m, 20c, and 20k, and the image bearing surface 31a contacts all the photoreceptors 21 sequentially. are placed.

A plurality of rollers 32 are arranged on the inner peripheral side of the intermediate transfer belt 31 so that the image carrying surface 31a of the intermediate transfer belt 31 is in contact with all the photosensitive members 21 . One of these rollers 32 is configured as a drive roller for rotating the intermediate transfer belt 31 .

The primary transfer portions 33 are arranged on the inner peripheral side of the intermediate transfer belt 31 at respective positions facing the photoreceptors 21 of the image forming units 20y, 20m, 20c, and 20k. 31 are arranged. A voltage having a polarity opposite to that of the toner is applied to these primary transfer portions 33 , thereby transferring the toner adhering to the image bearing surface of the photoreceptor 21 to the image bearing surface 31 a of the intermediate transfer belt 31 .

The secondary transfer roller 33 a is arranged below the intermediate transfer belt 31 at a position facing one of the plurality of rollers 32 so as to sandwich the intermediate transfer belt 31 between itself and the roller 32 . . At the nip portion where the secondary transfer roller 33a and the roller 32 are in contact with each other, the toner image formed on the image bearing surface 31a of the intermediate transfer belt 31 is transferred to the sheet St conveyed from the sheet supply portion 50 described below. It becomes a transfer position to transfer.

Further, the neutralization roller 34 is provided downstream of the secondary transfer roller 33 a in the rotation direction of the intermediate transfer belt 31 and upstream of the primary transfer portion 33 so as to sandwich the intermediate transfer belt 31 . remove the charge of

The cleaning unit 35 faces the image bearing surface 31a of the intermediate transfer belt 31 at a position above the fixing device 40 on the outer peripheral side of the intermediate transfer belt 31 between the neutralization roller 34 and the primary transfer portion 33. are arranged as follows. The cleaning unit 35 removes and collects toner remaining on the image bearing surface 31a of the intermediate transfer belt 31. As shown in FIG.

<Fixing Device 40>
The fixing device 40 is located below the cleaning unit 35 in the housing 100 and downstream of the secondary transfer roller 33a in the transfer section 30 with respect to the conveying direction x of the sheet St conveyed from the sheet supply section 50 described below. placed on the side. The fixing device 40 includes a heating roller 41 , a driving roller 43 and a pressing roller 45 . These are arranged substantially horizontally from the front side [W1] of the housing 100 toward the depth direction.

The heating roller 41 incorporates, for example, heating control means. Further, the driving roller 43 has a structure in which a fixing belt 43a is stretched between itself and the heating roller 41, and rotates the heating roller 41 via the fixing belt 43a. The pressing roller 45 constitutes a nip portion that nips the sheet St between itself and the heating roller 41 via the fixing belt 43a.

The fixing device 40 having such a configuration applies pressure and heat to the sheet St conveyed from the secondary transfer roller 33a, thereby fixing the toner image transferred to the sheet St to the sheet St.

<Sheet supply unit 50>
The sheet supply unit 50 is arranged inside the housing 100 and includes a plurality of supply trays 51 and a transport path 53 for transporting the sheets St. Among them, a plurality of supply trays 51 are provided according to the size and type of the sheet St. Each supply tray 51 accommodates the sheets St and supplies the accommodated sheets St to the transport path 53 one by one.

The transport path 53 includes an individual transport path 53a that transports the sheets St supplied from the supply trays 51 one by one to the secondary transfer roller 33a. Further, the transport path 53 includes a reversing transport path 53b for reversing and supplying the sheet St that has passed through the fixing device 40 to the secondary transfer roller 33a.

The individual transport path 53a and the reversing transport path 53b merge on the upstream side of the secondary transfer roller 33a, and the combined transport path 53g supplies the sheet St to the secondary transfer roller 33a. The transport path 53 also includes a discharge path 53 c for discharging the sheet St that has passed through the fixing device 40 from the housing 100 .

The sheet supply unit 50 as described above supplies and conveys the sheet St along the front side [W1] of the housing 100 .

<Air supply fan Af>
The air supply fan Af is a fan for supplying air into the housing 100 of the image forming apparatus 1, and is driven mainly when an image forming job is performed. Such air supply fans Af are provided at a plurality of locations within the housing 100 , particularly a plurality of them arranged around the fixing device 40 . The plurality of air supply fans Af arranged around the fixing device 40 are here, for example, a separation fan Af1, a sheet cooling fan Af2, and a cleaning unit cooling fan Af3. Each of these air supply fans Sf is connected to a duct (not shown) or arranged in the middle of the duct, and supplies air outside the housing 100 to each position inside the housing 100. supply to Next, each of these air supply fans Af will be described.

[Separation fan Af1]
The separation fan Af1 is for separating the sheet St from the fixing belt 43a of the fixing device 40 by blowing air. Such a separation fan Af1 is arranged, for example, on the downstream side of the fixing device 40, and the air supply end side of a duct (not shown) is arranged close to the discharge portion of the sheet St in the fixing device 40. . A plurality of sheet cooling fans Af2 may be provided for the fixing device 40 .

Here, depending on the rigidity of the sheet St, the separation fan Af1 may not need to be driven in the execution of the image forming job. That is, since the sheet St, which has low rigidity due to its small thickness or non-rigid material, is easily attracted to the fixing belt 43a of the fixing device 40, it is necessary to separate it from the fixing belt 43a by blowing air from the separation fan Af1. be. On the other hand, the sheet St, which has high rigidity due to its large thickness and high rigidity material, is difficult to be attracted to the fixing belt 43a of the fixing device 40, and thus is not easily attached to the fixing belt 43a by the separation fan Af1. To separate. Therefore, the separation fan Af1 may not be driven in the execution of the image forming job when the sheet St on which the image is to be formed has rigidity.

[Seat cooling fan Af2]
The sheet cooling fan Af2 is for cooling the sheet St discharged in a heated state by the fixing device 40 by supplying air. Such a sheet cooling fan Af2 is arranged, for example, in the vicinity of the discharge path 53c of the sheet supply section 50 so that the air supply end side of the duct (not shown) blows air toward the discharge path 53c. are placed. A plurality of sheet cooling fans Af2 may be provided for the discharge path 53c.

[Cleaning unit cooling fan Af3]
The cleaning unit cooling fan Af3 is for cooling the cleaning unit 35 provided in the transfer section 30 . Such a cleaning unit cooling fan Af3 is arranged close to the cleaning unit 35 in the transfer section 30, and is provided so that the air supply end side of a duct (not shown) blows air toward the cleaning unit 35. It is A plurality of cleaning unit cooling fans Af3 may be provided for the cleaning unit 35 .

<Exhaust fan Ef>
FIG. 2 is a configuration diagram of the main part of the image forming apparatus 1 of the first embodiment viewed from the sheet discharge side [L2], and is a diagram for explaining the arrangement state of the exhaust fan Ef. In FIG. 2, the right hand side of the housing 100 is the front side [W1] of the housing 100 and the side on which the door 102 is provided. 2, the left-hand side of the housing 100 is the depth side [W2] of the housing 100, which is opposite to the front side [W1]. The direction from the front side [W1] to the depth side [W2] is the conveying width direction y of the sheet St perpendicular to the conveying direction x of the sheet St. FIG. 2 illustrates part of the duct 103, which is omitted from FIG. 1, and the air flow is indicated by arrows. The configuration of the exhaust fan Ef will be described below with reference to FIGS. 1 and 2. FIG.

The exhaust fan Ef is a fan for exhausting the air in the vicinity of the fixing device 40 inside the housing 100 of the image forming apparatus 1 to the outside of the housing 100 . Such an exhaust fan Ef is provided inside the housing 100 and inside the ceiling housing 200 . Such an exhaust fan Ef is, for example, an internal exhaust fan Ef1 arranged in the housing 100 and a ceiling surface exhaust fan Ef2 arranged in the ceiling housing 200, and a plurality of each may be provided.

[Internal exhaust fan Ef1]
The internal exhaust fan Ef1 is arranged in the housing 100 on the depth side [W2] of the housing 100 at one end in the transport width direction y perpendicular to the transport direction x of the sheet St. As a result, installation of the internal exhaust fan Ef1 does not become an obstacle during maintenance with the door 102 open. The internal exhaust fan Ef<b>1 is arranged, for example, in the middle of the duct 103 as illustrated or arranged at the end of the duct 103 to exhaust the air around the fixing device 40 to the outside of the housing 100 .

In particular, the duct 103 provided with the internal exhaust fan Ef1 has an air intake end 103a arranged near the depth side [W2] of the fixing device 40 in the housing 100 . That is, the intake end 103a of the duct 103 is provided on the depth side [W2] of the intermediate position between the front side [W1] and the depth side [W2] of the housing 100. FIG. The duct 103 is arranged such that an air discharge end 103b communicates with the outside of the housing 100 on the surface of the housing 100 on the depth side [W2]. As a result, when the built-in exhaust fan Ef1 is driven, the air around the fixing device 40 is sucked from the depth side [W2] of the housing 100, and is drawn from the depth side [W2] of the housing 100. It is discharged outside.

The internal exhaust fan Ef1 arranged in this way preferably has an air blowing capacity that can be adjusted stepwise, but is not limited to this. Further, when a plurality of internal exhaust fans Ef1 are provided, each internal exhaust fan Ef1 may be provided in parallel or in series.

[Top exhaust fan Ef2]
The ceiling exhaust fan Ef2 is arranged inside the ceiling housing 200 so as to face the opening 101a of the ceiling plate 101 . As a result, installation of the internal exhaust fan Ef1 does not become an obstacle during maintenance with the door 102 open. Such a top surface exhaust fan Ef2 uses the ceiling housing 200 as a duct, takes in the air in the housing 100 from the opening 101a of the top plate 101, and exhausts the air inside the housing 100 from the exhaust hole 200a provided in the ceiling housing 200. of air is exhausted to the outside of the housing 100 . The opening 101 a of the top plate 101 is provided in the top plate 101 above the fixing device 40 and near the front side [W1] of the housing 100 .

As a result, when the top surface exhaust fan Ef2 is driven, the air near the fixing device 40 is sucked from the front side [W1] of the housing 100, and passes through the ceiling housing 200 and reaches the depth from the exhaust hole 200a. It will be discharged to the outside of the side [W2].

At the same time as the built-in exhaust fan Ef1 that sucks the air near the fixing device 40 from the depth side [W2] of the housing 100, the top surface exhaust fan Ef2 is driven to move the air near the fixing device 40 to the conveying width. A more uniform suction can be achieved in the direction y. Therefore, the exhaust heat near the fixing device 40 and the temperature adjustment of the fixing device 40 thereby becomes more uniform in the transport width direction y, and the fixing of the toner image by the fixing device 40 on the sheet St is more uniform in the transport width direction y. can be homogenized with As a result, the toner image can be uniformly fixed on the sheet St in the transport width direction y.

It is preferable that the air blowing capacity of the top surface exhaust fan Ef2 as described above is, for example, equal to or greater than the total air blowing capacity of the air supply fans Af. Also, it is preferable that the air blowing capacity is adjustable in steps, but the present invention is not limited to this.

In addition, the top surface exhaust fan Ef2 is not limited to one arranged facing the opening 101a of the top plate 101 . That is, the top surface exhaust fan Ef2 may have a configuration capable of discharging the air taken in from the opening 101a through the exhaust hole 200a using the ceiling housing 200 as a duct. Further, when a plurality of top surface exhaust fans Ef2 are provided, each top surface exhaust fan Ef2 may be provided in parallel or in series.

<Temperature sensor 60>
The temperature sensors 60 are provided, for example, on the front side [W1] and the depth side [W2] inside the housing 100 . These temperature sensors 60 may be provided, for example, close to the fixing device 40 or may be provided above the fixing device 40 and close to the cleaning unit 35 . The temperature sensor 60 may be provided at only one position, either near the fixing device 40 or near the cleaning unit 35 above the fixing device 40 .

<Control unit 70>
The control unit 70 shown in FIG. 1 controls driving of the image forming unit 20, the transfer unit 30, the fixing device 40, the sheet supply unit 50, the air supply fan Af, and the exhaust fan Ef based on the operation of the operation unit 80. Then, a toner image is formed on the sheet St. Further, the control unit 70 may refer to the temperature information from the temperature sensor 60 to control the driving of the air supply fan Af and the exhaust fan Ef. Such a control unit 70 is configured by a calculator such as a microcomputer. The computer includes a CPU (Central Processing Unit), ROM (Read Only Memory), and RAM (Random Access Memory).

In particular, the control unit 70 is characterized by driving control of the exhaust fan Ef when forming a toner image on the sheet St. This control will be described in the control method of the image forming apparatus 1 below.

<Operation unit 80>
The operation unit 80 is for inputting settings such as start and stop of the image forming apparatus 1 and image forming job settings by the image forming apparatus 1 . Such an operation unit 80 may be, for example, an operation key including a power switch provided on the upper surface of the housing 100, or a touch panel provided on the display surface of the display unit. Also, the operation unit 80 may be an external device such as a personal computer connected to the image forming apparatus 1 .

-Control Method of Image Forming Apparatus 1-
Next, a method for controlling the image forming apparatus 1 as described above will be described. FIG. 3 is a diagram for explaining the control method of the image forming apparatus according to the first embodiment. This figure is a graph showing over time the air blowing capacity [pw] of the air supply fan Af and the exhaust fan Ef provided in the image forming apparatus 1 described with reference to FIGS. 1 and 2 . In the graph of FIG. 3, the broken line indicates the total blowing capacity of the air supply fan Af. In the graph of FIG. 3, the solid line indicates the total blowing capacity of the exhaust fan Ef.

Also, in FIG. 3, each period during which the image forming apparatus 1 is powered on and in an active state but an image forming job is not executed is referred to as a waiting period [Tw]. Also, each period during which the image forming apparatus 1 executes an image forming job is defined as a job period [T1] to [T3].

The control method described above using the graph of FIG. It is implemented by the CPU executing a program recorded in ROM or RAM. Hereinafter, the control method of the image forming apparatus 1 will be described along the graph of FIG. 3 while referring to FIGS. 1 and 2 above.

<Control of waiting period [Tw]>
In each waiting period [Tw], the control section 70 controls the heating control means of the heating roller 41 in the fixing device 40 to heat the heating roller 41 . Further, the control unit 70 drives the exhaust fan Ef to exhaust the surroundings of the fixing device 40, exhaust the heat around the fixing device 40 to the outside of the housing 100, and heat the heating roller 41 to a predetermined level. keep at temperature. On the other hand, the control unit 70 controls heating control means of the heating roller 41 and other members of the exhaust fan Ef, that is, the image forming unit 20, the transfer unit 30, the sheet supply unit 50, the driving roller 43 of the fixing device 40, and the air supply fan. Af is kept stopped without being driven.

In this case, the control unit 70 adjusts the output of each exhaust fan Ef and drives it so as to achieve the first air blowing capacity [P1] set for the standby period [Tw] of the image forming apparatus 1 . The first air-blowing capacity [P1] is the air-blowing capacity for temperature adjustment exhaust gas required to keep the heating roller 41 of the fixing device 40 within a predetermined temperature range. Such a first blowing capacity [P1] is assumed to be a value lower than the sum of the maximum values of the blowing capacities of the exhaust fans Ef.

In order to obtain such a first air blowing capacity [P1], the control unit 70, for example, sets only one of the internal exhaust fan Ef1 and the top surface exhaust fan Ef2 to the first air blowing capacity [P1]. , while the other is kept stationary. In addition, the control unit 70 controls the internal exhaust fan Ef1 and the ceiling exhaust fan Ef1 so that the total air blowing capability when both the internal exhaust fan Ef1 and the ceiling exhaust fan Ef2 are driven becomes the first air blowing capability [P1]. Both of the surface exhaust fans Ef2 may be driven.

<Control of job period [T1] to [T3]>
During the job period [T1] to [T3], the control section 70 controls the heating control means of the heating roller 41 in the fixing device 40 to continue heating the heating roller 41 . Further, the control unit 70 controls driving of the driving rollers 43 of the image forming unit 20 , the transfer unit 30 , the sheet feeding unit 50 , and the fixing device 40 based on the setting of the image forming job input from the operation unit 80 . , a toner image is formed on the set number of sheets St.

Also, at this time, the control unit 70 controls the driving of the air supply fan Af and the exhaust fan Ef based on the settings of the job. The job settings here are, for example, the number of sheets St to be processed and the rigidity of the sheets St to be processed. Hereinafter, control of the air supply fan Af and the exhaust fan Ef by the control unit 70 in each job period [T1] to [T3] with different job settings will be described.

[First job period [T1]]
In the first job period [T1], the control unit 70 executes an image forming job for processing a predetermined number or more of sheets St having low rigidity, for example, based on the operation of the operation unit 80 .

Here, the sheet St having low rigidity is a sheet St whose rigidity is equal to or less than a predetermined value due to its thickness being small to a preset extent or being made of a material having no rigidity. The sheet St having such low rigidity is easily attracted to the fixing belt 43 a of the fixing device 40 . Therefore, it is necessary to separate the sheet St from the fixing belt 43a by blowing air from the separation fan Af1.

Further, the predetermined number of sheets is the minimum number of sheets to be processed that causes the temperature inside the housing 100 to rise due to the driving of the air supply fan Af. That is, when air is supplied into the housing 100 by driving the air supply fan Af, if the amount of air exhausted in the housing 100 is insufficient, heat stays in the housing 100 and the temperature inside the housing 100 rises. Rise. However, it takes a considerable amount of time from when the air supply fan Af starts to be driven until the temperature inside the housing 100 starts to rise. Therefore, the temperature inside the housing 100 does not rise until the minimum number of sheets to be processed at which the temperature rise is reached. Such a minimum number of processed sheets is set as a predetermined number of sheets.

During the first job period [T1], the control unit 70 turns off all the air supply fans Af that were stopped during the waiting period [Tw], that is, the separation fan Af1, the sheet cooling fan Af2, and the cleaning unit cooling fan Af3. Start driving. These air supply fans Af are driven at timing based on a preset program.

Further, the control unit 70 increases the blowing capacity of the exhaust fan Ef, which was driven at the first blowing capacity [P1] during the standby period [Tw], and changes the blowing capacity of the exhaust fan Ef to the second blowing capacity [P2]. do. This second blowing capacity [P2] is a value obtained by adding the total blowing capacity [pd] generated by driving the air supply fan Af in the first job period [T1] to the first blowing capacity [P1]. It is assumed that As a result, the pressure inside the housing 100 , particularly around the fixing device 40 , is maintained at the same level as the standby period [Tw], and the heating roller 41 of the fixing device 40 is maintained within a predetermined temperature range.

In order to obtain such a second air blowing capacity [P2], the control unit 70 drives both the internal exhaust fan Ef1 and the top surface exhaust fan Ef2. Also, the control unit 70 increases the blowing capacity of the exhaust fan Ef at the same time as the start of the first job period [T1], that is, at the same time as the start of driving the air supply fan Af, or after that. In this case, the blowing capacity of the exhaust fan Ef may be increased after the start of driving the air supply fan Af until the temperature inside the housing 100 begins to rise.

[second job period [T2]]
In the second job period [T2], the control unit 70 executes an image forming job for processing less than a predetermined number of sheets St having low rigidity, for example, based on the operation of the operation unit 80 .

In this case, the control unit 70 controls all the air supply fans Af that were stopped during the waiting period [Tw] immediately before the second job period [T2], that is, the separation fan Af1, the sheet cooling fan Af2, and the cleaning unit cooling fan. Start driving the fan Af3. This is similar to the case of the first job period [T1].

On the other hand, the control unit 70 keeps the output of the exhaust fan Ef at the same first blowing capacity [P1] as during the standby period [Tw]. Here, air is supplied into the housing 100 by driving the air supply fan Af, but the number of processed sheets St is less than the predetermined number. Therefore, even if the exhaust amount is temporarily insufficient, the temperature inside the housing 100 does not rise. Therefore, the blowing capacity of the exhaust fan Ef should be maintained at the same first blowing capacity [P1] as during the standby period [Tw].

[Third job period [T3]]
In the third job period [T3], the control unit 70 executes an image forming job for processing a predetermined number or more of sheets St having a rigidity equal to or higher than a predetermined number based on the operation of the operation unit 80 .

In this case, the control unit 70 starts driving the sheet cooling fan Af2 and the cleaning unit cooling fan Af3 among the air supply fans Af that were stopped during the waiting period [Tw], and stops driving the separation fan Af1. Keep These sheet cooling fan Af2 and cleaning unit cooling fan Af3 are driven at timing based on a preset program. Further, since the sheet St has rigidity, the sheet St is easily separated from the fixing belt 43a of the fixing device 40, and it is not necessary to drive the separation fan Af1.

On the other hand, the control unit 70 keeps the output of the exhaust fan Ef at the same first blowing capacity [P1] as during the standby period [Tw]. Here, air is supplied into the housing 100 by driving the sheet cooling fan Af2 and the cleaning unit cooling fan Af3. not reach.

In the third job period [T3], the air blowing ability of the exhaust fan Ef is increased by the total air blowing ability when the sheet cooling fan Af2 and the cleaning unit cooling fan Af3 are driven. You may raise from 1st ventilation capacity [P1].

In addition to the control in each job period [T1] to [T3] as described above, the control unit 70 controls the exhaust fan Ef when the total blowing capacity of the air supply fan Af reaches a predetermined blowing capacity. The blowing capacity may be increased from the first blowing capacity [P1] during the standby period [Tw]. In this case, the amount of increase in the air blowing capacity of the exhaust fan from the first air blowing capacity [P1] is the total air blowing capacity of the air supply fan Af.

Further, the control unit 70 drives the exhaust fan Ef based on the temperature information from the temperature sensor 60 in conjunction with the driving state of the air supply fan Af or independently of the driving state of the air supply fan Af. may In this case, when the temperature inside the housing 100 measured by the temperature sensor 60 reaches a predetermined value, the blowing capacity of the exhaust fan Ef is increased from the first blowing capacity [P1] during the standby period [Tw].

Moreover, when the temperature difference in the housing 100 measured by the temperature sensors 60 provided at two locations exceeds a predetermined temperature difference (for example, 10° C.), the temperature difference in the housing 100 becomes uniform. Thus, the blowing capacity of either the internal exhaust fan Ef1 or the ceiling exhaust fan Ef2 may be increased. As a result, the blowing capacity of the exhaust fan Ef increases from the first blowing capacity [P1] during the standby period [Tw].

<Effects of the first embodiment>
According to the first embodiment described above, heat is retained in the housing 100 by providing the top surface exhaust fan Ef2 that exhausts the air in the housing 100 from the opening of the top plate 101 of the housing 100. It is possible to prevent the temperature inside the housing 100 from rising by exhausting the heat inside the housing 100 . As a result, even when the air supply fan Af is driven based on the job settings, heat is retained in the housing 100 by increasing the air blowing capacity of the exhaust fan Ef including the top surface exhaust fan Ef2. It is possible to prevent the temperature inside the housing 100 from rising by exhausting the heat inside the housing 100 without causing the heat to rise. As a result, it is possible to prevent problems such as damage to electronic components due to temperature rise in the housing 100 and melting of toner on the image bearing surface 31 a of the intermediate transfer belt 31 and the cleaning unit 35 .

<<Second embodiment>>
-Configuration of image forming apparatus-
FIG. 4 is a schematic configuration diagram of the image forming apparatus 2 according to the second embodiment viewed from the front side [W1]. The front side [W1] is the side facing the operator who operates the image forming apparatus 2 . The image forming apparatus 2 of the second embodiment shown in this figure differs from the image forming apparatus 1 of the first embodiment in that a shutter 104 is provided in the opening 101a of the top plate 101. It is the same as the image forming apparatus 1 of the first embodiment.

The shutter 104 has an opening/closing driving portion 104a, and can freely open and close the opening 101a. The opening/closing driving portion 104a of the shutter 104 is preferably a solenoid from the viewpoint of saving space, but an electric motor may be used.

In the image forming apparatus 2 configured as described above, the control unit 70 controls the blowing capacity of the top surface exhaust fan Ef2 depending on the open/closed state of the shutter 104 .

-Control Method of Image Forming Apparatus 2-
Such a control method of the image forming apparatus 2 may be the same as the control method of the image forming apparatus of the first embodiment. Capability control is performed by controlling the open/close state of the shutter 104 .

<Effects of Second Embodiment>
Even with such a second embodiment, the same effects as those of the first embodiment can be obtained. Further, according to the second embodiment, control of the blowing capacity of the top surface exhaust fan Ef2 is performed by controlling the open/closed state of the shutter 104 . Therefore, the exhaust in the housing 100 by the top exhaust fan Ef2 can be performed with good responsiveness to the control by the control unit 70 .

<<Third Embodiment>>
-Configuration of image forming apparatus-
FIG. 5 is a schematic configuration diagram of the image forming apparatus 3 according to the third embodiment viewed from the front side [W1]. The front side [W1] is the side facing the operator who operates the image forming apparatus 3 . The image forming apparatus 3 of the third embodiment shown in this figure differs from the image forming apparatus of the first embodiment in that the exhaust fan Ef arranged around the fixing device 40 is connected to the top plate 101 of the housing 100 Only the top surface exhaust fan Ef2 provided in the opening 101a of the housing 100 is not provided. Other configurations are the same as those of the image forming apparatus 1 of the first embodiment.

This top surface exhaust fan Ef2 is not limited to one arranged facing the opening 101a of the top plate 101, and can exhaust the air taken in from the opening 101a using the ceiling housing 200 as a duct from the exhaust hole 200a. It is the same as the top surface exhaust fan Ef2 of the first embodiment that any configuration is sufficient. The air blowing capacity of the top surface exhaust fan Ef2 is adjustable stepwise, and the maximum value of the air blowing capacity is the maximum air blowing capacity [P2] shown in FIG.

As in the first embodiment, a plurality of top surface exhaust fans Ef2 may be provided. In this case, the stepwise adjustment of the blowing capacity of the top surface exhaust fan Ef2 may be realized by controlling the driving of the plurality of top surface exhaust fans Ef2.

-Control Method of Image Forming Apparatus 3-
Such a control method for the image forming apparatus 3 may be the same as the control method for the image forming apparatus of the first embodiment. However, the control unit 70 controls step by step the blowing capacity of one top exhaust fan Ef2, controls the on/off of driving of a plurality of top exhaust fans Ef2, or controls a plurality of top exhaust fans Ef2. The exhaust described with reference to FIG.

<Effects of the third embodiment>
Even in such a third embodiment, it is possible to obtain the same effect as in the first embodiment. Note that the third embodiment can be implemented in combination with the second embodiment, and the opening 101a of the top plate 101 may be provided with a shutter. effect can also be obtained.

Reference Signs List 1, 2, 3, 4 image forming apparatus 31 intermediate transfer belt 31a image bearing surface 33a secondary transfer roller 35 cleaning unit 40 fixing device 60 temperature sensor 70 control unit 100 housing 101 top plate 101a opening 102 Door 104 Shutter Af Air supply fan Af1 Separation fan Af2 Seat cooling fan Af3 Cleaning unit cooling fan Ef Exhaust fan Ef1 Internal exhaust fan Ef2 Top surface exhaust fan [W1] Front side (door side)
[W2]...Depth side [pw]...Blowing capacity [Tw]...Waiting period x...Conveyance direction y...Conveyance width direction

Claims (15)

a transfer belt having an image bearing surface on which a toner image is formed;
a secondary transfer roller disposed below the transfer belt and nipped between the transfer belt and the image bearing surface of the transfer belt to transfer the toner image onto the sheet;
a cleaning unit for removing toner from the image bearing surface of the transfer belt;
a fixing device disposed below the cleaning unit for fixing the toner image onto the sheet to which the toner image has been transferred;
a plurality of image forming units that form the toner image on the image bearing surface;
a housing that accommodates the transfer belt, the secondary transfer roller, the cleaning unit, the fixing device, and the image forming unit ;
the top plate of the housing has an opening above the cleaning unit,
An exhaust fan for exhausting air from the housing through the opening is provided on the top of the top plate,
wherein the plurality of image forming units are stacked vertically in the housing,
The transfer belt is arranged in parallel with the plurality of image forming units,
The cleaning unit is provided downstream of a position facing the secondary transfer roller and upstream of a position facing the plurality of image forming units in the rotation direction of the transfer belt.
Image forming device. A shutter that can be freely opened and closed is provided at the opening of the top plate,
2. The image forming apparatus according to claim 1, wherein control of the exhaust in the housing by the exhaust fan is performed by opening and closing the opening by the shutter. 3. The image forming apparatus according to claim 2, wherein the shutter includes an opening/closing driving section including a solenoid. 4. The image forming apparatus according to any one of claims 1 to 3, wherein an exterior top plate is provided above the top plate to cover the exhaust fan. The image forming apparatus according to claim 4, further comprising an exterior covering the exterior top plate and fixed to the exterior top plate. The image forming apparatus according to any one of claims 1 to 5, further comprising an air supply fan for supplying air into the housing. 7. The air supply fan according to claim 6, wherein the air supply fan is at least one of a separation fan that separates the sheet from the fixing device, a cooling fan for the sheet that has passed through the fixing device, and a cooling fan for the cleaning unit. Image forming device. A control unit that controls driving of the exhaust fan,
8. The image forming apparatus according to claim 6, wherein when the drive of the air supply fan is changed, the controller changes the blowing capacity of the exhaust fan in accordance with the change in the drive of the air supply fan. a control unit that controls driving of the exhaust fan;
A temperature sensor that measures the temperature in the housing,
The image forming apparatus according to any one of claims 1 to 8, wherein the control section controls driving of the exhaust fan based on the temperature inside the housing obtained from the temperature sensor. 10. The image forming apparatus according to claim 9, wherein the controller increases the blowing capacity of the exhaust fan when the temperature inside the housing obtained from the temperature sensor exceeds a predetermined temperature. 9. The image forming apparatus according to any one of claims 1 to 8, further comprising an internal exhaust fan that exhausts air from inside the housing. a transfer belt having an image bearing surface on which a toner image is formed;
a secondary transfer roller disposed below the transfer belt and nipped between the transfer belt and the image bearing surface of the transfer belt to transfer the toner image onto the sheet;
a cleaning unit for removing toner from the image bearing surface of the transfer belt;
a fixing device disposed below the cleaning unit for fixing the toner image onto the sheet to which the toner image has been transferred;
a housing that accommodates the transfer belt, the secondary transfer roller, the cleaning unit, and the fixing device;
the top plate of the housing has an opening above the cleaning unit,
An exhaust fan for exhausting air from the housing through the opening is provided on the top of the top plate,
The housing has an internal exhaust fan for exhausting the air in the housing,
The housing has a door on one side in a conveying width direction perpendicular to the conveying direction of the sheet,
Either one of the exhaust fan and the internal exhaust fan is arranged on the door side in the conveying width direction,
The image forming apparatus, wherein the other of the exhaust fan and the internal exhaust fan is arranged on the depth side opposite to the door in the transport width direction. The top plate has the opening on the door side,
The exhaust fan has an air intake end disposed on the door side through the opening to exhaust the air in the housing,
13. The image forming apparatus according to claim 12, wherein the internal exhaust fan is arranged on the depth side, and an air intake end is arranged on the depth side to exhaust the inside of the housing. a control unit that controls driving of the exhaust fan and the internal exhaust fan;
A temperature sensor arranged on the door side and the depth side in the housing,
14. The image forming apparatus according to claim 13, wherein the controller controls driving of the exhaust fan and the internal exhaust fan based on a temperature difference between the door-side temperature and the depth-side temperature detected by the temperature sensor. Device. 15. The image forming apparatus according to claim 14, wherein when the temperature difference exceeds a predetermined temperature difference, the controller controls driving of the exhaust fan and the internal exhaust fan so that the temperature difference becomes small. Device.

Images