WO2019235649A1

WO2019235649A1 - Cooling device, image forming apparatus, and image forming system

Info

Publication number: WO2019235649A1
Application number: PCT/JP2019/023388
Authority: WO
Inventors: 明日菜深町; 昭吉品川; 充長谷川; 傑竹内; 宏樹河合
Original assignee: キヤノン株式会社
Priority date: 2018-06-08
Filing date: 2019-06-06
Publication date: 2019-12-12

Abstract

A first belt 21 that is cooled by a heat sink has, on the upstream side of a cooling nip T4, a flat surface 21a for guiding a recording material S conveyed from a belt conveying device 70 to the cooling nip T4. The belt conveying device 70 is disposed such that an angle θ2 formed between a surface F parallel to a guide direction in which the recording material S is guided and the flat surface 21a becomes an acute angle, and guides the recording material S such that the leading end thereof hits against the flat surface 21a. The recording material S is brought into contact with the flat surface 21a over a predetermine range Y on the upstream side from an upstream end T4a of the cooling nip T4a, and the recording material S is guided to the cooling nip T4 while being cooled. In doing so, cooling of the recording material S is started before an entry into the cooling nip T4, thereby making it possible to suppress temperature increase of a second belt 25 due to heat of the recording material S, and consequently, toner, wax, and the like do not easily adhere to the second belt 25 from the recording material S.

Description

Cooling device, image forming apparatus, and image forming system

The present invention relates to a recording material cooling apparatus that cools a recording material that has passed through a fixing device that fixes a toner image by heating, an image forming apparatus including the recording material cooling apparatus, and an image forming system.

In an electrophotographic image forming apparatus, a toner image formed on a recording material such as paper is heated and pressed by a fixing device to fix the toner image on the recording material. The fixing of the toner image is performed by the recording material being nipped and conveyed by a fixing roller heated by a halogen heater or the like and a pressure roller pressed against the fixing roller. Since the recording material is heated when the toner image is fixed, the temperature of the recording material conveyed from the fixing device is likely to be higher than before the fixing. Then, after a toner image is fixed, there is a possibility that the stacked recording materials stick to each other as the recording materials conveyed at a temperature higher than a predetermined temperature are stacked on the stacking unit. In order to suppress such sticking of the recording material during loading, a recording material cooling device for cooling the recording material after fixing the toner image conveyed from the fixing device is provided in order to lower the temperature of the recording material after fixing the toner image. (Japanese Patent No. 5272424). In the recording material cooling apparatus described in Japanese Patent No. 5272424, one of a pair of conveying belts that pinch and convey the recording material conveyed from the fixing device is cooled by a heat sink, and the temperature of the recording material passes through the cooled conveying belt. This is a belt cooling system device that lowers the temperature.

In recent years, image forming apparatuses are compatible with various types of recording materials such as plain paper, thick paper, rough paper (rough paper), uneven paper (embossed paper, etc.), coated paper, etc. High speed is required. Further, in order to fix the toner to the recording material even at a low temperature, a toner containing a wax that melts at a low temperature is used. With such a toner, especially when a large amount of cardboard or coated paper is printed at a high speed, the recording material cooling device conventionally has a toner or wax from the recording material to one of the conveying belts not provided with a heat sink. Sometimes it was transferred and adhered. This is because the heat of the heated recording material is more easily transferred to the conveyance belt without the heat sink than the conveyance belt with the heat sink, and is stored in the conveyance belt without the heat sink. This is because the belt temperature rises. The toner and wax adhering to the conveyance belt can cause image unevenness and image smearing on the recording material to be cooled thereafter, and can cause the recording material to become dirty when paper wax or dust adheres to the wax.

The present invention has been made in view of the above problems, and has a configuration in which a recording material after toner image fixing is cooled using a belt-cooling type recording material cooling device, suppressing an increase in belt temperature due to the heat of the recording material, and recording. It is an object of the present invention to provide a cooling device and an image forming apparatus in which toner or wax hardly adheres from a material to a belt.

The cooling device according to the present invention includes a first belt, a second belt that abuts against the first belt and forms a nip portion with the first belt, and sandwiches and conveys the recording material together with the first belt. A cooling unit that cools the first belt, and a guide unit that guides the recording material that has passed through the fixing device to abut on the first belt on the upstream side of the nip portion in the conveyance direction of the recording material. With.

According to the present invention, since the cooling of the recording material by the first belt can be started before the recording material enters the nip portion, the temperature increase of the second belt due to the heat of the recording material can be suppressed. Therefore, it becomes difficult for toner or wax to adhere to the second belt.

FIG. 1 is a schematic diagram showing the configuration of the image forming apparatus of the present embodiment.

FIG. 2 is a schematic diagram showing the image forming unit.

FIG. 3 is a schematic view showing the recording material cooling device of the first embodiment.

FIG. 4 is a control block diagram illustrating the control unit.

FIG. 5 is an enlarged view showing the upstream side of the nip portion in an enlarged manner.

FIG. 6 is an enlarged view showing, on an enlarged scale, the upstream side of the nip portion when the guide member is provided.

FIG. 7 is a schematic view showing a recording material cooling device of the second embodiment.

FIG. 8 is a graph showing the relationship between the number of continuous sheets passed and the temperature of the second belt in the conventional case.

FIG. 9 is a schematic diagram showing an example of an image forming system.

FIG. 10 is a schematic diagram showing an example of another image forming system.

[First embodiment]
<Image forming apparatus>
A schematic configuration of the image forming apparatus according to the present exemplary embodiment will be described with reference to FIGS. An image forming apparatus 100 shown in FIG. 1 is an electrophotographic tandem type full-color printer. The image forming apparatus 100 includes image forming units PY, PM, PC, and PK that form yellow, magenta, cyan, and black images, respectively. The image forming apparatus 100 records a toner image in accordance with an image signal from a document reading device (not shown) connected to the apparatus main body 100A or an external device such as a personal computer connected to the apparatus main body 100A. S is formed. Examples of the recording material S include various types of sheet materials such as plain paper, thick paper, rough paper, uneven paper, coated paper, plastic film, cloth, and the like.

As shown in FIG. 1, the image forming portions PY, PM, PC, and PK are arranged side by side along the moving direction of the intermediate transfer belt 8 in the apparatus main body 100A. The intermediate transfer belt 8 is stretched around a plurality of rollers and is configured to travel in the direction of arrow R2. The intermediate transfer belt 8 carries and conveys the toner image that has been primarily transferred. A secondary transfer roller 10 is disposed at a position facing the roller 9 that stretches the intermediate transfer belt 8 with the intermediate transfer belt 8 in between, and a secondary image that transfers the toner image on the intermediate transfer belt 8 to the recording material S. The transfer portion T2 is configured. A fixing device 11 is disposed downstream of the secondary transfer portion T2 in the recording material conveyance direction.

Under the image forming apparatus 100, a cassette 12 in which the recording material S is accommodated is disposed. The recording material S is conveyed by the conveyance roller 13 from the cassette 12 toward the registration roller 14 through a conveyance path 600 that forms a path of the recording material S in the apparatus main body 100A. Thereafter, the registration roller 14 starts to rotate in synchronization with the toner image formed on the intermediate transfer belt 8 as will be described later, whereby the recording material S is conveyed through the conveyance path 600 to the secondary transfer portion T2. The Although only one cassette 12 is shown here, a plurality of cassettes 12 may be arranged so that recording materials S of different sizes and thicknesses can be accommodated. The recording material S is selectively conveyed to the conveyance path 600. Further, not only the recording material S accommodated in the cassette 12, but also the recording material S placed on the manual feeding unit (not shown) may be transported to the transport path 600. In the case of the present embodiment, the conveyance path 600 is a reverse conveyance that reverses the front and back of the recording material S cooled by the recording material cooling device 20 and carries it again to the image forming units PY, PM, PC, and PK during double-sided printing. Part 600a.
<Image forming unit>

The four image forming units PY, PM, PC, and PK included in the image forming apparatus 100 have substantially the same configuration except that development colors are different. Accordingly, here, the image forming unit PK will be described as a representative, and description of the other image forming units PY, PM, and PC will be omitted.

As shown in FIG. 2, a cylindrical photosensitive drum 1 is disposed as a photosensitive member in the image forming unit PK. The photosensitive drum 1 is rotationally driven in the arrow R1 direction. Around the photosensitive drum 1, a charging device 2, an exposure device 3, a developing device 4, a primary transfer roller 5, and a drum cleaning device 6 are arranged.

A process for forming a full color image, for example, by the image forming apparatus 100 will be described. First, when the image forming operation is started, the surface of the rotating photosensitive drum 1 is uniformly charged by the charging device 2. The charging device 2 is, for example, a corona charger that irradiates charged particles accompanying corona discharge to charge the photosensitive drum 1 to a uniform negative dark potential. Next, the photosensitive drum 1 is scanned and exposed with a laser beam L corresponding to the image signal emitted from the exposure device 3. As a result, an electrostatic latent image corresponding to the image signal is formed on the surface of the photosensitive drum 1. The electrostatic latent image formed on the photosensitive drum 1 is visualized by toner (developer) accommodated in the developing device 4 and becomes a visible image.

The toner image formed on the photosensitive drum 1 is primarily transferred to the intermediate transfer belt 8 at a primary transfer portion T1 configured with the primary transfer roller 5 disposed with the intermediate transfer belt 8 interposed therebetween. At this time, a primary transfer bias is applied to the primary transfer roller 5. The toner remaining on the surface of the photosensitive drum 1 after the primary transfer is removed by the drum cleaning device 6.

Such an operation is sequentially performed in each of the yellow, magenta, cyan, and black image forming units PY to PK, and the four color toner images are superimposed on the intermediate transfer belt 8. Thereafter, the recording material S accommodated in the cassette 12 is conveyed to the secondary transfer portion T2 in accordance with the toner image formation timing. Then, by applying a secondary transfer bias to the secondary transfer roller 10, the full-color toner image formed on the intermediate transfer belt 8 is secondarily transferred onto the recording material S all at once.

Next, the recording material is conveyed to the fixing device 11. The fixing device 11 includes a fixing roller 11a that is rotatably arranged, and a pressure roller 11b that rotates while being pressed against the fixing roller 11a. The fixing roller 11a is rotated at a predetermined rotation speed (for example, 400 mm / s) by a driving motor (not shown) while being in pressure contact with the pressure roller 11b (for example, a pressure contact force of about 784 N (about 80 kg)). A halogen heater 11c is disposed in the fixing roller 11a, and the fixing device 11 can heat the recording material S when the surface temperature of the fixing roller 11a is increased by the halogen heater 11c (for example, 180 ° C.).

The fixing device 11 heats and presses the conveyed recording material S by nipping and conveying the recording material S on which the toner image is formed in the fixing nip T3 formed by the fixing roller 11a and the pressure roller 11b. The toner image is fixed on the recording material S. That is, the toner of the toner image formed on the recording material S by heating and pressurization is melted and mixed, and fixed to the recording material S as a full-color image. In this way, a series of image forming processes is completed. Then, the recording material S that has passed through the fixing device 11 is conveyed to the recording material cooling device 20 by the belt conveying device 70. The belt conveying device 70 is configured such that the recording material S is transferred from the fixing device 11 to the recording material cooling device 20 when the belt carrying the recording material S is rotated at a predetermined rotation speed (for example, 400 mm / s) by air adsorption or the like. (Refer to FIG. 5 described later). The recording material cooling device 20 cools the recording material S conveyed by the belt conveyance device 70. The recording material cooling device 20 will be described later (see FIG. 3).

In this embodiment, a toner having a melt viscosity of 1.0 × 10 ⁶ Pa · s and a glass transition temperature of 56 ° C. is used. A polyester resin was used as the binder resin that becomes the base of the toner. The method for producing the toner is a pulverization method, but is not limited thereto, and a suspension polymerization method, an interfacial polymerization method, a dispersion polymerization method, or the like may be used. The toner contains wax in order to improve the releasability from the fixing device 11 and the toner fixability when the toner image is fixed on the recording material S. As the wax, for example, polyolefin wax, long chain hydrocarbon wax, dialkyl ketone wax, ester wax, amide wax and the like are used. The melting point of the wax is usually 40 to 160 ° C, preferably 50 to 120 ° C. If the melting point is within this range, the heat resistance of the toner is ensured, while image formation is performed without causing image defects such as cold offset even when fixing is performed at a low temperature. The wax content in the toner is preferably 3% by mass to 30% by mass.
<Recording material cooling device>

Next, the recording material cooling device 20 of the first embodiment will be described with reference to FIG. The recording material cooling device 20 of the present embodiment is a belt cooling type cooling device. As shown in FIG. 3, the recording material cooling device 20 includes an endless first belt 21 and an endless second belt 25 that sandwiches and conveys the first belt 21 and the recording material S. For example, the first belt 21 and the second belt 25 are made of high-strength polyimide and have a thickness of 100 μm and a circumferential length of 942 mm. The recording material cooling device 20 has a heat sink 30 for cooling the first belt 21. In the case of this embodiment, the heat sink 30 is in contact with the first belt 21 that is in contact with the recording material S on the surface side on which the toner image is formed by the fixing device 11. Note that the first belt 21 is not necessarily cooled by the heat sink 30. For example, a belt fan that can cool the first belt 21 by blowing air to the first belt 21 may be used.

As shown in FIG. 3, the first belt 21 is wound around a plurality of first belt stretching rollers (22a to 22e), and at least one of the first belt stretching rollers (22a to 22e) is not shown. It is rotated by a drive motor. As a result, the first belt 21 rotates in the direction of arrow B in the figure. On the other hand, the second belt 25 is wound around a plurality of second belt stretching rollers (26 a to 26 e) and is in contact with the first belt 21. The second belt 25 rotates following the first belt 21. Although not shown here, a plurality of pressure rollers for pressing the second belt 25 toward the heat sink 30 may be provided on the inner peripheral side of the second belt 25. The pressure roller, for example, pressurizes the second belt 25 with a pressurizing force of 9.8 N (1 kgf), so that the first belt 21 is reliably attached to the heat sink 30 (specifically, a heat receiving portion 30a described later) via the second belt 25. Make contact.

Here, the first belt 21 is driven and the second belt 25 is driven by the first belt 21, but the second belt 25 is driven and the first belt 21 is driven by the second belt 25. You may let them. Alternatively, both the first belt 21 and the second belt 25 may be driven.

The recording material S on which the toner image is fixed is sandwiched between the first belt 21 and the second belt 25, and is conveyed in the conveying direction (the direction of arrow C in the figure) according to these rotations. At that time, the recording material S passes through a cooling nip T4 as a nip portion formed by the contact between the first belt 21 and the second belt 25. In the case of this embodiment, the first belt 21 is cooled by the heat sink 30. In order to efficiently cool the recording material S, the heat sink 30 is disposed so as to be in contact with the inner surface of the first belt 21 at a location where the cooling nip T4 is formed. The recording material S is cooled via the first belt 21 when passing through the cooling nip T4.

The heat sink 30 as a cooling unit is a heat sink made of a metal such as aluminum. The heat sink 30 conducts heat from the heat receiving portion 30a to the heat radiating portion 30b, a heat receiving portion 30a for contacting the first belt 21 and removing heat from the first belt 21, a heat radiating portion 30b for radiating heat, and the heat receiving portion 30a. A fin base 30c. The heat dissipating part 30b is formed by a large number of heat dissipating fins in order to increase the contact area with air and promote efficient heat dissipating. For example, the radiating fin has a thickness of 1 mm, a height of 100 mm, and a pitch of 5 mm, and the fin base 30c has a thickness of 10 mm. Further, in order to forcibly cool the heat sink 30 itself, a cooling fan 40 that blows air toward the heat sink 30 (specifically, the heat radiating portion 30b) is provided. The air volume of the cooling fan 40 is set to 2 m ³ / min, for example.
<Control unit>

As shown in FIG. 1, the image forming apparatus 100 includes a control unit 300. The control unit 300 will be described with reference to FIGS. 4 and 4 with reference to FIGS. However, various devices such as a motor and a power source for operating the image forming apparatus 100 are connected to the control unit 300 other than those shown in the drawing, but the illustration and description thereof are omitted here because they are not the gist of the invention.

The control unit 300 performs various controls of the image forming apparatus 100 such as an image forming operation, and includes a CPU 301 (Central Processing Unit), a memory 302 such as a ROM, a RAM, or a hard disk device. The memory 302 stores, for example, various programs such as an image forming job for forming an image on the recording material S, various data, and the like. The control unit 300 can execute various programs stored in the memory 302, and can execute the various programs to operate the image forming apparatus 100. Note that the memory 302 can also temporarily store calculation processing results and the like accompanying the execution of various programs.

The control unit 300 can execute, as an image forming job, a single-sided print job for fixing a toner image on only one side (one side) of the recording material S and a double-sided printing job for fixing a toner image on both sides of the recording material S. . In the case of a single-sided printing job, the recording material S cooled by the recording material cooling device 20 is discharged out of the apparatus main body 100A by the paper discharge roller 15 and stacked on the stacking unit 60. On the other hand, in the case of a double-sided printing job, the recording material S cooled by the recording material cooling device 20 is reversed by the reversing conveyance unit 600a, so that the front and back of the recording material S are switched. The reversed recording material S is returned to the conveyance path 600 and is conveyed along the conveyance path 600 toward the registration roller 14, and the surface side (second surface side) not printed by the registration roller 14 is the intermediate transfer belt 8. The sheet is conveyed to the secondary transfer portion T2 in a state directed toward the side. In the secondary transfer portion T2, the full-color toner image formed on the intermediate transfer belt 8 is secondarily transferred collectively to the recording material S (second surface side). Thereafter, the recording material S is fixed with the toner image by the fixing device 11 and cooled by the recording material cooling device 20, and the cooled recording material S is discharged out of the apparatus main body 100 </ b> A and stacked on the stacking unit 60.

The control unit 300 is connected to an operation unit 400, a belt drive motor 401, a fan drive motor 402, and a transport motor 403 via an input / output interface. The operation unit 400 is, for example, an operation panel or an external terminal that accepts execution instructions of various programs and various data inputs by a user (user). The user can use the operation unit 400 to record, for example, the size and type of the recording material S, recording material information such as basis weight and surface property, image information such as density, printing information such as the number of prints and double-sided / single-sided printing. Settings are possible.

The control unit 300 controls the belt drive motor 401 that drives at least one of the first belt stretching rollers (22a to 22e), and controls the start and stop of the driving of the first belt 21, the moving speed, and the like. To do. That is, any one of the first belt stretching rollers (22a to 22e) driven by the belt drive motor 401 also serves as a driving roller that drives the first belt 21 while stretching it. Further, the control unit 300 controls the fan drive motor 402 to control the start and stop of the cooling fan 40 and the air volume. Further, the control unit 300 controls the conveyance motor 403 to control the start and stop of driving of the recording material S by the belt conveyance device 70, the rotation speed, and the like.

By the way, in the conventional image forming apparatus using the recording material cooling device (see FIG. 3) having the heat sink 30 only on the first belt 21 described above, the toner of the recording material S is applied to the second belt 25 where the heat sink 30 is not provided. And wax may stick. For example, when double-sided printing is performed on a recording material S having a low thermal conductivity such as thick paper or coated paper, toner or wax may adhere to the second belt 25 while toner does not adhere to the first belt 21. This is because, compared with the first belt 21 that is in direct contact with the heat sink 30, the second belt 25 that is not in direct contact with the heat sink 30 is less likely to lose heat stored in the belt itself. Therefore, when the recording material S is nipped and conveyed by the cooling nip T4 to be cooled, the heat of the recording material S heated by the fixing device 11 is easily stored in the second belt 25 rather than the first belt 21. The second belt 25 is warmed. As the high-temperature recording material S continuously passes through the cooling nip T4 in this way, heat is stored in the second belt 25, and the temperature of the second belt 25 rises. In the case of the recording material S having a low thermal conductivity, such as thick paper or coated paper, even if the recording material S is cooled by the first belt 21 while being held in the cooling nip T4, the first belt 21 and the recording material S are used. The second belt 25 that is cooled by the heat sink 30 via the above is difficult to be cooled. Therefore, if the time for passing through the cooling nip T4 of the recording material S is short, the temperature of the second belt 25 is not sufficiently lowered by the heat sink 30. In this way, the temperature of the second belt 25 becomes higher than the temperature of the first belt 21.

Here, regarding the conventional image forming apparatus, the relationship between the number of continuous sheets and the temperature of the second belt 25 is shown in FIG. As can be understood from FIG. 8, the temperature of the second belt 25 increases as the number of continuous sheets of the recording material S increases, and reaches 65 ° C. after passing the first sheet from 40 ° C. to the 50th sheet. When the temperature of the second belt 25 is equal to or higher than the glass transition temperature of the toner, the toner and wax on the recording material S are softened by the heat of the second belt 25 on the side of the surface on which the toner image has already been fixed in double-sided printing. obtain. For example, when a toner having a glass transition temperature of 56 ° C. is used, as shown in FIG. 8, the toner or wax may be in a softened state from at least the 20th continuous sheet.

The glass transition temperature of the toner is determined based on a loss tangent (tan δ = loss elastic modulus / storage elastic modulus) measured by a viscoelasticity measuring device (trade name: Rhegel-E4000 manufactured by UBM). The viscoelasticity measurement device is a vertical dynamic viscoelasticity measurement device based on the forced vibration non-resonance method, and detects the stress response generated by applying sinusoidal distortion to a sample such as toner, using a quartz piezoelectric stress detector. To do. Then, the dynamic stress waveform and dynamic displacement waveform at that time can be calculated by calculating the loss elastic modulus, storage elastic modulus, loss tangent by obtaining the amplitude and phase difference angle of each frequency using FFT calculation etc. It is.

As described above, when the toner wax on the recording material S is softened due to the temperature rise of the second belt 25, the toner and wax on the recording material S partially adhere to the second belt 25, and recording is performed. The toner image on the material S has uneven gloss (so-called gloss unevenness). Alternatively, the toner or wax adhering to the second belt 25 may cause the recording material S that subsequently passes through the cooling nip T4 to become dirty. Therefore, in the present embodiment, in view of the above-described points, the temperature of the second belt 25 that has not been cooled can be suppressed so as not to rise above the glass transition temperature of the toner on the recording material S. Hereinafter, a configuration for doing so will be described with reference to FIG. In the following description, the terms “upstream” and “downstream” refer to upstream and downstream, respectively, with respect to the rotation direction of the first belt 21 (the conveyance direction of the recording material S by the first belt 21 and the second belt 25). Shall.

As shown in FIG. 5, the first belt 21 has a flat surface 21a for guiding the recording material S conveyed from the belt conveying device 70 to the cooling nip T4 on the upstream side of the cooling nip T4. The flat surface 21a includes a first roller 22a disposed at the upstream end T4a (upstream end in the rotation direction) of the cooling nip T4 among the plurality of first belt stretching rollers (22a to 22e), and the upstream side of the first roller 22a. The belt part stretched between the 2nd rollers 22e arrange | positioned in this is pointed out. The first belt 21 is stretched so that an angle θ1 formed by a virtual surface G obtained by extending the surface formed in the cooling nip T4 upstream in the conveyance direction of the recording material S and the flat surface 21a is an acute angle. In the case of the present embodiment, the second roller 22e is disposed closer to the belt conveyance device 70 than the cooling nip T4 and above the first roller 22a, whereby the angle θ1 formed by the virtual surface G and the flat surface 21a. Has an acute angle.

The belt conveying device 70 includes an endless belt 71 that carries the recording material S and two

rollers

72 and 73 that bridge the belt 71, and the belt 71 is rotated by the rotation of the

rollers

72 and 73. The recording material S is conveyed while being guided toward the flat surface 21a. The belt conveyance device 70 as a guide unit is arranged such that an angle θ2 formed by a virtual line F extending from a guide surface parallel to the guide direction for guiding the recording material S and the flat surface 21a is an acute angle. The angle θ2 formed by the plane F parallel to the guide direction for guiding the recording material S and the flat surface 21a can take various values depending on conditions such as the rigidity of the recording material S and the rotational speed of the first belt 21. Further, the guide surface of the recording material S of the belt 71 is located between the first roller 22a and the second roller 22e in the vertical direction. As a result, the belt conveyance device 70 guides the front end of the recording material S so as to abut against the flat surface 21a.

However, the angle θ2 is the same as that of the recording material S on the flat surface 21a even when the recording material S such as coated paper having higher rigidity than that of the plain paper is conveyed from the belt conveyance device 70 toward the first belt 21. This is an angle at which the contact start position (intersection point O) can be maintained on the flat surface 21a. That is, when the angle θ2 formed by the plane F parallel to the guide direction for guiding the recording material S and the flat surface 21a is larger than a predetermined angle, the recording material S having high rigidity reaches the contact start position of the flat surface 21a. Then, a force starts to be applied to the recording material S in a direction away from the first belt 21. Thereby, the recording material S is curved away from the flat surface 21a, and the leading end of the recording material S is hardly guided to the cooling nip T4. Therefore, in the present embodiment, even when the recording material S having a particularly high rigidity is used by reducing the angle θ2 as much as possible, the contact state of the recording material S on the flat surface 21a is maintained and the contact state is maintained. The recording material S is guided to the cooling nip T4. For example, when the recording material S is a device that uses mirror coat platinum having a basis weight of 256 g / m ² , the upper limit of the angle at which the first belt 21 and the recording material S can be kept in contact is 40 °. is there. Therefore, the angle θ2 may be greater than 0 and not more than 40 °, and preferably not less than 5 ° and not more than 10 °.

On the flat surface 21a, the recording material S abuts at least in a predetermined range Y upstream from the upstream end T4a of the cooling nip T4, and the recording material S is cooled by the first belt 21 that is easily cooled by the heat sink 30. It is guided to the cooling nip T4. The recording material S is abutted against the flat surface 21a at the contact start position (intersection O). The first belt 21, the second belt 25, and the belt conveying device 70 are arranged so that the cooling nip T4 is started from a contact start position (intersection point O) and a position sandwiching at least the predetermined range Y in the rotation direction. Has been.

The predetermined range Y is maintained in a state in which the recording material S is in contact with the flat surface 21a from when the recording material S starts to contact the flat surface 21a until it reaches the cooling nip T4. Is set to a range in which can be reduced. That is, the recording material S is preliminarily cooled by the flat surface 21a before reaching the cooling nip T4, and the temperature of the recording material S decreases. If the temperature of the recording material S can be lowered before reaching the cooling nip T4 in this way, the temperature increase of the second belt 25 caused by the recording material S reaching the cooling nip T4 and contacting the second belt 25 is achieved. Is less likely to occur. That is, it is possible to suppress the temperature of the second belt 25 from rising due to the heat of the recording material S. In the case of this embodiment, for example, when the control temperature control of the fixing roller 11a is 190 ° C. and the rotational speed of the belt 71 of the belt conveyance device 70 is 400 mm / s, the temperature of the recording material S is lowered to the toner remelting temperature or lower. The cooling time required for this is 0.05 s. In order to secure the cooling time of 0.05 s, it is desirable that the predetermined range Y is 20 mm or more (Y ≧ 0.05 × rotational speed of the belt 71).

On the other hand, if the predetermined range Y is too long, the behavior of the recording material S tends to become unstable until the recording material S enters the cooling nip T4, and it becomes difficult to maintain the state in contact with the flat surface 21a. Alternatively, the leading end of the recording material S is buckled toward the second belt 25 and is difficult to enter the cooling nip T4. For example, when the recording material S is an apparatus that uses mirror-coated platinum having a basis weight of 256 g / m ^2, a predetermined range Y in which the contact state between the first belt 21 and the recording material S can be maintained on the flat surface 21a. The upper limit is 60 mm. Accordingly, the predetermined range Y may be 20 mm or more and 60 mm or less, and in this embodiment, the predetermined range Y is set to 40 mm as a range in which the temperature of the recording material S can be sufficiently lowered.

As described above, in this embodiment, before the recording material S heated by the fixing device 11 enters the cooling nip T4, the first belt 21 that is in direct contact with the heat sink 30 covers a predetermined range Y. Are in contact. That is, the recording material S is guided toward the cooling nip T4 while maintaining the contact with the first belt 21 from the cooling nip T4 to the contact start position (intersection point O). In this way, since the cooling of the recording material S by the first belt 21 is started before the recording material S enters the cooling nip T4, the recording material S enters the cooling nip T4 and directly contacts the heat sink 30. The temperature rise of the second belt 25 due to contact with the second belt 25 that is not present can be suppressed. Thus, since the temperature rise of the second belt 25 due to the heat of the recording material S can be suppressed, toner, wax, and the like are hardly attached from the recording material S to the second belt 25.

In the above-described embodiment, the example in which the belt conveyance device 70 is used to convey the recording material S to the recording material cooling device 20 has been described, but the present invention is not limited thereto. For example, the guide member may be arranged so as to guide the recording material S conveyed by the belt conveying device 70 toward the recording material cooling device 20. Alternatively, a guide member may be arranged so that the recording material S conveyed from the fixing device 11 is directly guided to the recording material cooling device 20. FIG. 6 shows the case where the guide member is arranged. Here, the same components as those in the first embodiment described above are denoted by the same reference numerals, and description thereof is simplified or omitted.

As shown in FIG. 6, the guide member 80 as a guide unit is a lower guide member that supports the lower surface side of the recording material S, and guides the recording material S toward the flat surface 21a. The guide member 80 is disposed so that an angle θ2 formed by a plane F1 parallel to the guide direction for guiding the recording material S and the flat surface 21a is an acute angle, and the leading end of the recording material S abuts against the flat surface 21a. To guide. Even in this case, the predetermined range Y is maintained in a state in which the recording material S is in contact with the flat surface 21a from when the recording material S starts to contact the flat surface 21a until it reaches the cooling nip T4. Thus, the temperature of the recording material S is set in a range where the temperature can be lowered. In this way, since the temperature rise of the second belt 25 due to the heat of the recording material S can be suppressed, even when double-sided printing is performed at high speed, the toner on the second belt 25 is caused by the temperature rise of the second belt 25. Can be difficult to adhere.
[Second Embodiment]

Next, the recording material cooling device 20A of the second embodiment will be described. In the recording material cooling device 20 of the first embodiment described above (see FIG. 3), the recording material S is cooled on the surface side on which the toner image is formed by the fixing device 11, but the invention is not limited to this. For example, the recording material S may be cooled from the surface opposite to the surface on which the toner image is formed by the fixing device 11. FIG. 7 shows a recording material cooling device 20 </ b> A that cools the recording material S from the surface opposite to the surface on which the toner image is formed by the fixing device 11. In the recording material cooling device 20A shown in FIG. 7, the same components as those of the recording material cooling device 20 of the first embodiment are denoted by the same reference numerals, and description thereof is simplified or omitted. Here, the case where the recording material S is guided toward the recording material cooling device 20 by the guide member 80 is shown as an example.

In this embodiment, the heat sink 30 is in contact with the first belt 21 that is in contact with the recording material S from the surface opposite to the surface on which the toner image is formed by the fixing device 11. That is, in the present embodiment, the first belt 21 having the heat sink 30 inside is located on the same side as the pressure roller 11b with respect to the conveyance path of the recording material S, and the heat sink 30 is located on the same side as the fixing roller 11a. The second belt 25 that is not included in the position is located. In this case, each time the recording material S having a low thermal conductivity such as cardboard passes through the cooling nip T4, the temperature of the second belt 25 is increased by the recording material S, and the toner adheres to the second belt 25. There is a fear. Therefore, as shown in FIG. 7, the recording material S is guided to the first belt 21 side by the guide member 80. Even in this case, as in the first embodiment described above, the recording material S is brought into contact with the first belt 21 over a predetermined range from the upstream end of the cooling nip T4 to the upstream side in the rotational direction of the first belt 21. 21 is guided to the cooling nip T4 while being cooled. As a result, an increase in the temperature of the second belt 25 through the recording material S can be suppressed, so that the effect that the toner, wax, etc. of the recording material S hardly adhere to the second belt 25 can be obtained.

In the above-described embodiment, the fixing device 11 and the cooling device 20 are included in one housing (the apparatus main body 100A) of the image forming apparatus 100. However, the image forming units PY, PM, PC, PK, The intermediate transfer belt 8 and the secondary transfer roller 10 are provided in a first casing, the fixing device 11 and the cooling device 20 are provided in a second casing different from the first casing, and the first casing and the second casing The image forming apparatus that constitutes one apparatus may be provided with the cooling device 20 described above.

Further, the configuration is not limited to the above as long as the configuration includes a cooling device provided downstream of the fixing device 11 in the recording material conveyance direction. For example, as shown in FIG. 9, the cooling device 20 may be provided in the external cooling device 101 connected to the image forming apparatus 100. In the image forming system 1X shown in FIG. 9, each of the image forming apparatus 100 and the external cooling apparatus 101 is installed on an installation surface such as a floor by a plurality of installation units 800. Here, the installation unit 800 is a caster, an installation leg, or the like.

Further, in the image forming system, a cooling device provided on the downstream side of the fixing device is connected to the downstream side in the recording material conveyance direction with respect to the image forming device 100 as in the image forming system 1X shown in FIG. The cooling device 20 may be provided in the external cooling device 101 connected to the further downstream side of the external fixing device 500.

According to the present invention, since the cooling of the recording material by the first belt can be started before the recording material enters the nip portion, the temperature increase of the second belt due to the heat of the recording material can be suppressed. There are provided a cooling device, an image forming apparatus, and an image forming system for an image forming apparatus that make it difficult for toner, wax, and the like to adhere to the second belt.

The present invention is not limited to the above embodiment, and various changes and modifications can be made without departing from the spirit and scope of the present invention. Therefore, in order to make the scope of the present invention public, the following claims are attached.

This application claims priority on the basis of Japanese Patent Application No. 2018-110728 filed on June 8, 2018 and Japanese Patent Application No. 2019-094690 filed on May 20, 2019, All the descriptions are incorporated herein.

Claims

A cooling device that cools a recording material that has passed through a fixing device that heats and fixes the toner image formed by the image forming unit to the recording material,
The first belt,
A second belt that abuts against the first belt to form a nip portion with the first belt, and sandwiches and conveys the recording material together with the first belt;
A cooling unit for cooling the first belt;
And a guide unit that guides the recording material that has passed through the fixing device so as to contact the first belt on the upstream side of the nip portion with respect to the conveyance direction of the recording material.
A plurality of stretching rollers for stretching the first belt;
The plurality of stretching rollers include a first roller disposed at an upstream end of the nip portion in the transport direction, and a second roller disposed on the upstream side of the first roller in the transport direction,
The first belt is stretched between the first roller and the second roller to form a guide surface for guiding the recording material to the nip portion,
The cooling device according to claim 1, wherein the guide unit guides the recording material so that a leading end of the recording material that has passed through the fixing device contacts the guide surface.
The cooling device according to claim 2, wherein the guide surface is a flat surface.
The first belt stretches the plurality of stretching rollers so that an angle formed between a virtual surface obtained by extending a surface formed in the nip portion upstream in the conveyance direction of the recording material and the flat surface is an acute angle. The cooling device according to claim 3, which is mounted.
The cooling device according to claim 3 or 4, wherein the guide unit guides the recording material such that an angle of the recording material with respect to the flat surface when the tip comes into contact with the flat surface becomes an acute angle.
The cooling device according to claim 5, wherein the guide unit guides the recording material such that an angle of the recording material with respect to the flat surface when the tip comes into contact with the flat surface is greater than 0 ° and equal to or less than 40 °. .
The guide unit is a belt conveyance unit that conveys a recording material,
The cooling device according to any one of claims 2 to 6, wherein a downstream end portion of the belt conveyance unit in the conveyance direction is located between the first roller and the second roller in the conveyance direction.
The cooling device according to any one of claims 1 to 4, wherein the guide unit is a lower guide member that supports a lower surface side of a recording material conveyed from the fixing device and guides the recording material.
The cooling device according to any one of claims 1 to 8, wherein the cooling unit is a heat radiating plate that contacts the inner peripheral surface of the first belt and radiates heat.
The cooling device according to claim 9, wherein the nip portion is formed in a contact region of the heat radiating plate with respect to the first belt.
The image forming unit for forming a toner image on a recording material;
A fixing device that heats and fixes the toner image formed by the image forming unit to the recording material;
An image forming apparatus comprising the cooling device according to claim 1.
12. The image forming apparatus according to claim 11, further comprising a reversing conveyance unit that reverses the front and back of the recording material on which the toner image is fixed by the fixing device and re-conveys the recording material to the image forming unit.
The image forming apparatus according to claim 12, further comprising: a control unit capable of executing an image forming job for reversing the recording material on which the toner image is fixed by the fixing device by the reversing conveyance unit and fixing the toner image on both surfaces of the recording material. apparatus.
The fixing device includes a heating unit having a heating source, and a pressurizing unit that can sandwich and convey the recording material together with the heating unit and pressurizes the recording material against the heating unit,
The image forming apparatus according to claim 10, wherein the first belt is provided on a side where the heating unit is provided with respect to a conveyance path in which the recording material that has passed through the fixing device is conveyed. .
A storage unit for storing a recording material conveyed to the image forming unit;
The image forming apparatus according to claim 11, wherein the storage unit stores mirror-coated platinum having a basis weight of 256 g / m 2 as a recording material.
An image forming apparatus comprising: the image forming unit that forms a toner image on a recording material; and a fixing device that heats and fixes the toner image formed by the image forming unit to the recording material;
An image forming system comprising the cooling device according to claim 1.