JP5146191B2 - Transfer fixing apparatus and image forming apparatus - Google Patents

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrophotographic or ink jet copying machine, a printer, or a facsimile, and a transfer fixing apparatus that transfers and fixes a toner image formed on an image carrier onto a recording medium, and an image using the same. The present invention relates to a forming apparatus.

In a conventional image forming apparatus such as an electrophotographic copying machine, a printer, or a facsimile, a copy or a recorded product can be obtained by heat-fixing an unfixed toner image transferred from an image carrier to a recording medium. During fixing, the unfixed image is heated while nipping and pressing the recording medium carrying the unfixed toner image, whereby the developer contained in the unfixed image, in particular, the toner is melted and softened and penetrated into the recording medium. By fixing the toner, the toner is fixed on the recording medium. In view of this, there has been proposed a transfer fixing device that integrally transfers and fixes an unfixed image formed on an image carrier onto a recording medium (see, for example, Patent Document 1 and Patent Document 2).
Among them, the one disclosed in Patent Document 1 is a type that performs secondary transfer fixing from the intermediate transfer member to the transfer material, and the one disclosed in Patent Document 2 is the secondary transfer from the intermediate transfer member to the transfer fixing member. After fixing, the transfer fixing member is of a type that is third-transfer-fixed to a transfer material. In these techniques, as a member constituting an image, a chargeable powder mainly composed of a resin called toner is generally used.
These toners have higher hot offset generation temperatures (good hot offset resistance) and lower fixing temperatures (low temperature fixing) as energy savings and miniaturization of devices such as copiers are being studied. There is a need for toners with good properties. In particular, when the fixing temperature (belt temperature) rises in transfer fixing, heat is transferred to the drum in contact with the transfer fixing belt and further to the developing unit, and image defects due to belt deformation and problems such as toner solidification are more likely to occur. Since it is more likely to occur, a toner having a lower temperature fixability is required.

Conventionally, wax has been added to the toner in order to impart releasability. In general, many release agents such as wax have a low melting point, which causes stains on the developing member due to seepage, and causes turbidity due to the formation of an interface with the resin when melted, thereby impairing color reproducibility. There is. In addition, there is a problem in compatibility with the resin, developability deteriorates as the addition amount increases, and spent with the carrier also occurs, so the charge amount is insufficient and charging instability occurs, so it is not used or the use amount is reduced Preferably it can be done.
In a conventional electrophotographic image forming apparatus, it is a transfer process to a transfer material that easily deteriorates the image quality. As the transfer material, paper is mainly used. However, even if the paper is used, there are various thicknesses ranging from plain paper to cardboard, and the surface properties vary from high quality to rough. In particular, on paper with rough surface properties, the intermediate transfer member cannot follow the surface properties of the paper and forms a minute gap, so abnormal discharge occurs in the minute gap part and the image is not transferred normally. As a whole, there is a problem that the image is likely to be a rough image.

In this regard, as described in the above-mentioned Patent Document 1 or Patent Document 2, an image forming apparatus having a transfer and fixing process performs transfer and fixing at the same time, so that an image in which the transfer process and the fixing process are performed separately is performed. Compared to a forming apparatus (hereinafter, referred to as a normal apparatus), the image quality is hardly deteriorated even when paper having a rough surface is used. This is because heat is applied at the same time as the transfer, and the toner is softened and melted by the heat to form block-like lumps with viscoelasticity, so that the image at the minute gap portion of the paper is easily transferred as lumps. From such advantages, it can be said that an image forming apparatus having a transfer fixing unit is a system suitable for achieving high image quality.
Furthermore, the advantages of the transfer-fixing method are different from the usual electrophotographic method, because there is no powder on the transfer material, a conveyance guide that can define the paper passing direction with a small curvature is installed just before the transfer-fixing part. It is possible, and stable conveyance from thin paper to thick paper is possible regardless of the paper type. Incidentally, in normal electrophotography, since powder is placed on the transfer material before fixing, the conveyance guide can guide the paper passing direction only with a gap so as not to rub the powder.
In many cases, paper jam occurs due to the paper becoming unstable in the gap. As a result of the high degree of freedom in the sheet passing direction in the transfer fixing method, it is possible to realize an image forming apparatus having a wide compatibility with paper types and an extremely low occurrence rate of sheet passing.

By the way, in the above-described transfer fixing method, from the viewpoint of maximizing the thermal efficiency of transfer fixing, it is necessary to increase the temperature of the surface where the paper and the toner are fused, that is, the interface between the paper and the toner. For this reason, a method in which the toner is pressed against the paper in a sufficiently heated and softened state has already been proposed. Such devices are disclosed in, for example, Patent Literature 3, Patent Literature 4, Patent Literature 5, and the like.
However, in this known method, it is necessary not only to heat the toner but also to heat the transfer fixing member. Therefore, when the transfer fixing member is as thick as, for example, 300 μm, the peripheral length of the transfer fixing member such as a four-tandem image forming method. If the length is long, the thermal efficiency is not always good. In addition to the transfer fixing member heating process, the conventional transfer fixing apparatus has a cooling process for cooling the transfer fixing member after the transfer / fixing process in order to reduce thermal damage of the image forming unit. There are many cases.
In particular, because cooling is required, heating the same member on the one hand and cooling on the other hand is very inefficient from an energy standpoint. Further, the heating and cooling cycle is not only wasteful in terms of energy, but also disadvantageous in terms of durability of the transfer fixing member due to a repeated heat cycle.

In addition, Patent Document 6 and Patent Document 7 disclose a method of performing transfer fixing by heating a transfer fixing member, a transfer material, and a pressure member, respectively. In this method, the temperature of the transfer fixing member is heated to a temperature equal to or lower than the toner melting temperature, and the transfer material is heated to a temperature equal to or higher than the toner melting temperature, so that the transfer fixing member is not heated so much.
However, in this method, the transfer material is heated on both the front and back surfaces, and preheating the paper to the back side, which is a non-image surface, is also performed in the conventional transfer fixing, but this clearly does not contribute to fixing. Energy is wasted by warming up to the back. In addition, there is a possibility of causing a first-surface image defect during double-sided printing. In addition to energy inefficiency, the image on the first side (the back side of the paper) is remelted particularly during the second side printing in double-sided printing, leading to image degradation. Further, even after the transfer and fixing, the high-temperature transfer material is conveyed together with the transfer and fixing member, and the high-temperature transfer material is in contact with the transfer and fixing member for a long time, which is disadvantageous in terms of durability of the transfer and fixing member by heat cycle.

  Considering the above points, as a transfer and fixing method with better thermal efficiency, paper that selectively heats the paper surface (transfer surface) just before contact with the toner and transfers and fixes it before the heat is transferred to the back of the paper. A heat transfer fixing method has already been proposed. With regard to paper heating transfer fixing in which only one side (the paper surface) is heated, Japanese Patent Application Laid-Open No. H10-260260 proposes a method of selectively heating paper immediately before transfer fixing. In the case of transfer fixing, unlike the previous electrophotographic method, no toner is placed on the transfer material. Therefore, in the above-mentioned paper heating transfer fixing method, the member for heating and conveying the transfer material can be installed in a narrow and limited place. For this reason, a heating member for heating the surface of the transfer material can be installed immediately before the transfer fixing nip, and sent to the transfer fixing nip before the temperature of the transfer material surface decreases. As a result, particularly thick paper can be fixed without wastefully heating the back side of the paper.

In general, a transfer fixing method for heating paper does not require large energy for cooling compared to a transfer fixing method for heating a transfer fixing member. However, even in the transfer fixing method in which paper is selectively heated as in Patent Document 8, since the heated recording medium comes into contact with the transfer fixing belt and is transferred and fixed, the transfer fixing belt is in contact with the paper. The temperature will rise. Further, in the transfer and fixing method in which the paper is selectively heated, only the portion of the transfer and fixing belt that is in contact with the paper is heated, so the width of the transfer and fixing belt that is heated varies depending on the paper width. In particular, when continuous paper feeding is performed, the temperature difference between the portion of the transfer fixing member that contacts the heated recording medium and the non-paper feeding portion becomes significant.
This temperature unevenness in the width direction of the transfer / fixing member (direction perpendicular to the recording medium conveyance direction) adversely affects the next image forming process and degrades the image quality. Specifically, if such temperature unevenness remains, temperature unevenness also occurs on the photoconductor in contact with the transfer fixing member, and as a result, heat is transmitted to the development process parts, image defects, toner solidification, etc. It becomes easy to generate the trouble. In the conventional transfer fixing apparatus, in addition to the above-described heating process of the transfer fixing member, a cooling process for cooling the transfer fixing member after the transfer / fixing process is performed in order to reduce thermal damage of the image forming unit. In many cases, since the transfer and fixing member is cooled uniformly, the temperature unevenness has not been solved even after the cooling process.
Japanese Patent Laid-Open No. 10-63121 JP 2004-145260 A JP 2003-91201 A JP-A-11-65330 JP 2005-140994 A Japanese Examined Patent Publication No. 3-63756 Japanese Patent Publication No. 3-63757 JP 2005-37879 A

The present invention has been made in view of the above circumstances, and its object is to employ a transfer fixing method is an optimal image forming means image quality achieved, the toner image and Symbol recording medium on the transfuse member In the transfer fixing device in which the surface of the sheet is heated in advance before the transfer fixing, the transfer fixing member is efficiently cooled so as to eliminate the temperature unevenness, and the problem due to the remaining temperature unevenness is eliminated, and a good image is obtained. It is an object of the present invention to provide a transfer fixing device and an image forming apparatus that are always obtained.

In order to solve the above-mentioned problems, the invention of claim 1 is a transfer and fixing device for transferring and fixing a toner image onto a transfer and fixing surface of a recording medium, wherein the transfer and fixing member has an unfixed toner image formed on the surface. Heating means for heating the unfixed toner image on the transfer fixing member, recording medium heating means for preheating the surface of the recording medium before transferring and fixing the unfixed toner image to the recording medium, and the transfer fixing A pressure fixing member that forms a nip portion that pressurizes the recording medium with the member, and the transfer fixing member after the unfixed toner image is transferred and fixed to the recording medium at the nip portion. Control the cooling width of the transfer and fixing member based on either the cooling means configured to adjust the cooling width for cooling and the paper width of the recording medium or the print image width determined by the print image data A cooling control unit that, characterized by comprising a.
According to a second aspect of the present invention, in the transfer / fixing apparatus according to the first aspect, the image forming apparatus further includes a paper width detecting unit that detects a width of the recording medium and outputs a paper width signal. The cooling width of the transfer and fixing member is controlled based on either the sheet width signal or the print image width signal obtained from the print image data.

According to a third aspect of the present invention, in the transfer fixing device according to the first or second aspect, the cooling means is an ion wind cooling device that cools using an ion wind generated by corona discharge. To do.
According to a fourth aspect of the present invention, in the transfer fixing device according to the first or second aspect, the cooling means uses a gas flow generated by a blower for cooling.
According to a fifth aspect of the present invention, in the transfer / fixing device according to the third or fourth aspect, a heat exchanger for cooling a gas is provided, and the gas flow or the ionic wind cooled by the heat exchanger is supplied to the transfer / fixing member. It is used for cooling.
According to a sixth aspect of the present invention, in the transfer fixing device according to any one of the first to fifth aspects, the image forming apparatus further includes an exhaust unit for discharging air to the outside of the main body of the transfer fixing device incorporating apparatus. To do.
According to a seventh aspect of the present invention, there is provided an electrophotographic image forming apparatus comprising the transfer fixing apparatus according to any one of the first to fifth aspects.

  According to the present invention, there is provided a transfer fixing device and an image forming apparatus that can efficiently cool a transfer fixing member so as to eliminate temperature unevenness, eliminate problems caused by residual temperature unevenness, and always obtain a good image. can do.

[First Embodiment]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Hereinafter, as an example of the present invention, an embodiment adapted to a tandem type electrophotographic color copying machine as an image forming apparatus will be described and described with reference to the drawings.
FIG. 1 is a side view showing an essential part of a four-tandem electrophotographic color copier as an image forming apparatus according to an embodiment of the present invention. This apparatus employs a transfer and fixing system, which is an image forming means that is optimal for achieving high image quality, and heats both paper and toner images from the viewpoint of energy efficiency. Since this type of color copying machine is well known, detailed description of the overall configuration is omitted.
An outline of the configuration and operation of the four-tandem color copying machine of this embodiment will be described with reference to FIG. The color copying machine includes an image forming unit 1A positioned at the center of the apparatus main body, a paper feeding unit 1B positioned below the image forming unit 1A, and an image reading unit (not shown) positioned above the image forming unit 1A. Have.
With this apparatus, image formation is possible at a linear velocity of 300 mm / s. In the image forming unit 1A, a transfer fixing belt 2 is disposed as a transfer fixing member that is provided so as to be able to circulate and provide a transfer surface extending in the horizontal direction. And a configuration for forming images of colors that are complementary to each other. That is, the photoreceptors 3Y, 3M, 3C, and 3K as image carriers capable of carrying toner images of complementary color toners (yellow, magenta, cyan, and black) are along the transfer surface portion of the transfer fixing belt 2. Are juxtaposed in order.

The alphabets attached to the numbers with the respective symbols correspond to the toner colors. A typical structure of the transfer and fixing belt 2 is a laminated structure of polyimide resin 80 μm, silicone rubber 160 μm, and fluorine rubber 7 μm as a base material. The rubber layer is necessary to follow the irregularities of the recording medium, and the fluororesin on the surface is unnecessary if the release property of the rubber to toner and paper powder is excellent.
Each of the photoconductors 3Y, 3M, 3C, and 3K is composed of a drum that can be driven to rotate in the same direction. Around the drum, a charging device 4 that performs image forming processing in the rotation process, and writing as optical writing means A device 5, a developing device 6, a primary transfer device 7, and a cleaning device 8 are arranged in this order. The alphabets attached to the reference numerals correspond to the colors of the toners as in the photoconductor 3.
Each developing device 6 accommodates a respective color toner. The transfer fixing belt 2 is configured to be wound around the driving roller 11 and the driven rollers 9 and 10 so as to be movable in the same direction at a position facing the photoconductors 3Y, 3M, 3C, and 3K. A cleaning device 12 that cleans the surface of the transfer and fixing belt 2 is provided at a position facing the drive roller 11.
The surface of the photoreceptor 3Y is uniformly charged by the charging device 4, and an electrostatic latent image is formed on the photoreceptor 3Y based on optical image information from the image reading unit. The electrostatic latent image is visualized as a toner image by a developing device 6Y containing yellow toner, and the toner image is transferred onto the fixing belt 2 by a primary transfer device 7Y to which a predetermined bias is applied. Next transferred. The other photoconductors 3M, 3C, and 3K also form similar images only with different toner colors, and the toner images of the respective colors are sequentially transferred and superimposed on the transfer and fixing belt 2. The toner remaining on the photoreceptor 3 after the transfer is removed by the cleaning device 8, and after the transfer, the electric potential of the photoreceptor 3 is initialized by a charge-removing lamp (not shown) to prepare for the next image forming process.

The transfer fixing device according to the present embodiment includes the transfer fixing belt 2, the pressure roller 24, the heating body 13, the cooling means 20, the discharge fan 26, a paper width detection unit, and a cooling control unit.
That is, the transfer and fixing device is in pressure contact with the image carrying surface of the transfer and fixing belt 2 at the position where the transfer and fixing belt 2 as a transfer and fixing member that is also an intermediate image carrier that carries a toner image on the surface and the driven roller 9 are disposed. Then, a pressure roller 24 as a pressure member (opposing member) forming a nip N serving as a transfer and fixing unit that sandwiches and presses the recording medium, and the inside of the transfer fixing belt on the upstream side of the nip N in the belt circumferential direction. After the toner 13 (planar heating element or halogen heater) as a heating means for heating the toner image arranged to face the peripheral surface and the recording medium are transferred and fixed at the nip (N), the transfer fixing belt 2 is transferred. The cooling means 20 using the air blower (winding device) which generates the gas flow for cooling is provided.
Further, a discharge fan 26 is provided on the downstream side of the cooling unit 20 as an exhaust unit for discharging the gas flow sent from the cooling unit 20 and cooling the transfer fixing belt 2 to the outside of the apparatus housing. In addition, a paper width detection unit that detects the paper width of the transfer paper as a recording medium and outputs a paper width signal, and a cooling control unit (not shown in the figure) for adjusting the cooling width of the cooling unit 20 are provided. Yes.
As the paper width detection unit, a conventional one provided for the purpose of optimizing the image forming process or the like can be diverted, and a signal associated with selection switching of the paper tray can be used as it is. The cooling control unit is realized as one function executed by the CPU of the device control unit that controls the entire device, and the paper width output from the paper width detection unit corresponding to the paper width of the recording medium, as will be described in detail later. The effective cooling width in the belt width direction of the cooling means 20 is controlled according to the signal (in the embodiment, the cooling region is a line object in the belt transfer direction, and at the same time the position in the broad sense).

The configuration of the transfer fixing unit will be described in detail. In the vicinity of the driven roller 9, a pressure roller 24 is provided as a pressure member or an opposing member that forms a nip N (hereinafter also referred to as a nip or a transfer nip) with the transfer fixing belt 2. The pressure roller 24 is formed in a pipe shape from a metal such as aluminum, and a release layer is coated on the surface.
After the latent image is formed by a known method, each color toner image developed in the development process, that is, the toner transferred from the photoreceptors 3Y, 3M, 3C, 3B to the transfer fixing belt 2 serving as an intermediate transfer body, respectively. The image T is heated by the heating unit 13 until it is fixed on the paper P at the fixing nip portion N, and is fixed on the paper P preheated by the heating unit 120 at the nip N. At this time, the transferred toner image T is heated from the inside of the belt by a heating element (planar heating element or halogen heater) in FIG. 1, but non-contact heating (halogen heater or the like) is applied from the outside of the belt. (Radiant heat).

A paper feeding unit 1B in FIG. 1 feeds paper by feeding the paper P as a recording medium in a stacked manner and the paper P in the paper feeding tray 14 one by one in order from the top. The paper roller 16, the transport roller pair 17 that transports the fed paper P, and the fed paper P are temporarily stopped and the skew is corrected, and then the leading edge of the image on the transfer fixing belt 2 and the transport direction The registration roller pair 18 is fed toward the nip N at a timing that coincides with the predetermined position.
In the embodiment, a heating roller 120 as a paper heating unit for heating the paper surface is provided immediately before the transfer fixing unit in the transfer paper conveyance path. The heating roller 120 is controlled in a range of 140 to 200 ° C. to heat the paper surface. At this time, when an experiment was performed with a thermocouple fixed to the back side of the paper, it was confirmed that the temperature of the back side of the paper had only changed within 15 ° C. after 0 to 60 ms after contact with the heating roller 120 (measurement was made on the Ricoh copy paper 6200). Using). Here, the paper heating is performed by the heating roller 120, but other methods may be used.

Another configuration example of the paper heating means is shown in FIGS. The paper heating means in FIG. 8 is provided with a small-diameter roller 131 in contact with the paper separately from the high-temperature roller 130 serving as a heating source. In this configuration, the diameter of the small-diameter roller 131 that contacts the paper can be reduced, so that the distance from the paper heating position to the transfer nip N is shortened, and transfer and fixing can be performed before heat is transmitted to the back side of the paper as compared with the case of FIG. The high-temperature roller 130 is an aluminum thin roller and contains a heat source such as a halogen heater, and the small-diameter roller 131 is a silicon rubber roller having high heat conduction.
In the paper heating means of FIG. 9, an endless metal SUS belt 132 is stretched between a high-temperature metal roller 130 and a small-diameter roller 131. In this configuration, heating can be performed up to the vicinity of the transfer nip N, and the contact time with the paper can be made longer than in the configuration of FIG. In order to ensure contact between the paper and the SUS belt 132, a pressing member such as a roller or a leaf spring may be provided from the back of the paper.
The paper heating means shown in FIG. 10 includes a heating element 134 having PTC characteristics capable of self-temperature control as a heating source and a SUS leaf spring 133 extending from the heating element. The leaf spring 133 and the paper surface are in contact with each other and heated. The heating element 134 is a resistance heating element whose resistance rapidly increases when a predetermined Curie point is reached. For this reason, the self-temperature control function can safely prevent an accident in which the temperature of the paper is abnormally increased. Instead of the SUS leaf spring, a metal brush in which metal fibers are bundled may be used so as to follow the uneven surface of the paper and overheat.

The paper heating means shown in FIG. 11 heats the paper surface by bringing a heating element 134 having a PTC characteristic into contact with the upper surface of the paper as a heating source and pressing the pressing member 122 having fibers implanted into the lower surface of the paper. Since the paper heating time can be made longer than in FIG. 10, the heating time can be secured even if the paper speed is increased. The fibers of the pressing member 122 are polyimide fibers. Further, a fiber intrusion preventing member 123 is provided to prevent the fiber from being caught.
Further, in the transfer section from the paper heating means to the transfer nip N, the auxiliary heating means (radiation overheating) can suppress the decrease in the paper surface temperature, and the paper can be heated more stably. At this time, for safety, it is preferable to provide a shutter that blocks radiation when abnormal.
Returning to FIG. 1, the paper P that has passed through the heating roller 120 as a paper heating unit (recording medium heating unit) is supported by the driven roller 9 and is formed by the transfer fixing belt 2 and the pressure roller 24. The toner image T on the image carrying surface of the transfer and fixing belt 2 is transferred and fixed onto the surface of the paper P by passing through the nip while being pressed and heated by being entered into the fixing unit).
After the above-described transfer fixing step, the transfer fixing belt 2 is cooled by the cooling means 20 between the transfer portion for the transfer fixing belt 2 and the transfer portion for the most upstream photoconductor 3K. As a result, the temperature rise of the transfer fixing belt 2 can be suppressed, and the thermal effect on the photoreceptor is eliminated. The cooling means 20 is controlled so as to selectively and strongly cool a region where the temperature is particularly high, thereby effectively preventing temperature unevenness from remaining on the transfer fixing belt 2.
In addition, as shown in FIG. 1, in combination with the cooling means 20, a leveling roller 210 is provided at a downstream position of the cooling means 20 so as to level the temperature distribution as an auxiliary. We are trying to do it more reliably. The leveling roller 210 will be described later separately.

Next, the cooling means 20 which is a characteristic point of this embodiment will be described in detail with reference to FIG. FIG. 2 shows a cooling device in which a plurality of fans according to this embodiment are arranged. As the cooling device, a plurality of fans (axial fans, cross flow fans, etc.) arranged in alignment along the belt width direction (direction orthogonal to the moving direction) are used.
Then, a control unit (not shown) performs individual air volume control or ON / OFF control of each fan based on a paper width signal from an existing paper width detection unit (not shown), thereby transferring and fixing the fan in contact with high-temperature paper. The belt is selectively cooled in the width direction (the cooling width of the transfer fixing member is controlled). That is, the portion where the temperature has increased due to contact with the paper is selectively cooled. Only the fan corresponding to the paper width is turned on by a signal from the paper width detection unit. For example, in the case of A4 length, the transfer and fixing belt in the portion (band-like region) corresponding to the 210 mm width through which the paper has passed can be selectively concentrated and cooled to efficiently cool the transfer and fixing belt.
In the case of forced air cooling using gas for cooling as described above, the ventilation air volume is important. In the present embodiment, a fan is disposed as an exhaust means (air blowing means) for discharging the air used for cooling outside the apparatus as a configuration for assisting the cooling means 20 described above and enhancing the cooling efficiency. One or more exhaust fans may be provided. In the case of forced air cooling using a gas for cooling, the following formula is generally applicable.
q = ΔT · (ρ · Cp · Q / 60)
Here, q: apparatus heat generation amount (W) = heat amount received from paper ΔT: internal temperature increase (K) = transfer fixing belt temperature increase ρ: air density (kg / m3) = about 1.2 kg / m3 at room temperature
Cp: constant pressure specific heat of air (J / (kg · K)) = about 1007 J / (kg · K)
Q: Necessary ventilation (m3 / min).

The flow of cooling air will be described with reference to FIG. Cooling air from the cooling device 20 is blown to a transfer fixing belt (width based on a paper width signal from a paper width detection unit) that is an object to be cooled. At this time, in order to make the air flow smooth, it is better to slightly tilt in the transfer fixing belt conveyance direction. The air that has cooled the transfer fixing belt flows in the transfer fixing belt conveyance direction, and is discharged outside the apparatus by a discharge fan 26 that functions as an exhaust unit (blow unit) installed on the downstream side of the transfer fixing belt.
For example, as the discharge fan 26, an axial fan is disposed at an appropriate position of the apparatus housing. An appropriate duct may be provided on the gas suction side and / or the gas delivery side of the exhaust fan 26. Thus, more effective cooling is possible by always using fresh air as cooling air and increasing the ventilation air volume with a smooth air flow. As will be described later as another embodiment, ozone is generated when ion wind is used as a cooling device (cooling means) (see FIGS. 5 and 6). It is desirable to attach a filter.
The leveling roller 210 disposed downstream of the cooling unit 20 and in contact with the transfer and fixing belt 2 also assists in reducing temperature unevenness. It is made of a material such as a heat pipe or graphite having high thermal conductivity, and rotates in contact with the transfer fixing belt 2. In addition, it is also possible to use the roller 11 as a heat pipe roller without providing the leveling roller 210 separately, and to also serve as the leveling roller. Then, the residue (attached matter such as residual toner) on the cooled transfer and fixing belt is collected by the belt cleaning device 12, and a series of transfer and fixing processes is completed.

As the cooling means 20, it is possible to adopt a configuration different from the above-described example, and the same effects as the above-described configuration can be obtained. Different embodiments of the cooling means 20 using air flow are given.
FIG. 3 is a schematic configuration diagram showing a cooling unit 20A according to a modification. The cooling means 20A is equipped with a louver that is configured to be variable in a direction extending to a fan outlet of a single cooling device (long sirocco fan) by an appropriate drive mechanism. In the case of this configuration, the cooling control unit drives the louver by a signal from the paper width detection unit to control the posture so that air is intensively blown to the transfer fixing belt region corresponding to the paper width. Since the toner image is formed at the center of the transfer and fixing belt 2 symmetrically in the width direction, it is only necessary to move the louver group near the side end of the transfer and fixing belt 2 in the width direction.
FIG. 4 shows another configuration example, in which air supplied from a compressor or a fan is ejected from an air nozzle having a large number of aperture groups (air ejection holes) distributed in the belt width direction to cool the transfer fixing belt. . This is also possible by selectively opening and closing the nozzles at positions corresponding to the paper width by opening and closing the air ejection holes in accordance with a signal from the paper width detection unit, thereby selectively cooling the portion of the transfer fixing belt where the temperature has increased. it can.

As described above, according to the first embodiment, the transfer fixing belt after transfer fixing is performed by selectively cooling the width of the transfer fixing belt in contact with the paper based on the paper width signal from the paper width detecting unit. Temperature unevenness, in particular, an increase in the paper width temperature of the transfer and fixing belt during continuous paper feeding can be suppressed, and a good image can always be provided.
Note that the present embodiment employs a paper heating transfer fixing method with respect to a conventional fixing device that simply heats and presses a sheet holding an unfixed toner image, and thus has an energy saving characteristic as a known effect. Briefly describing this point, in the conventional color image forming apparatus, in order to obtain a sufficient gloss, the heat amount about 1.5 times that of the black and white image forming apparatus is given in consideration of the temperature drop due to the paper. For this reason, the paper is heated more than necessary, and the adhesion between the toner and the paper is increased more than necessary.
In contrast, in the present embodiment, the temperature for transferring and fixing belt 2 and the paper temperature can be set independently as temperatures for obtaining sufficient gloss, so the temperature of fixing and fixing belt 2 (fixing set temperature) is lowered. it can. Further, since the paper P is heated immediately before, it is not excessively heated and the adhesion between the toner T and the paper is not increased more than necessary.
Thus, in this embodiment, since heat transfer to the intermediate transfer member can be suppressed, durability can be improved. Further, since the cooling means described above is provided, the temperature of the intermediate transfer member can be reduced, and thermal deterioration on the intermediate transfer member side can be further suppressed. Depending on the specifications and ratings of the apparatus, such as in the case of a low speed machine, only the selective cooling means 20 immediately after the fixing described above may be used, and a practically sufficient cooling performance can be secured.

[Second Embodiment]
In the second embodiment, in addition to the configuration of the first embodiment described above, a heat exchanger is attached to the gas suction side of the cooling means 20 described above. Although illustration is omitted, by using a heat exchanger in combination, it is possible to further increase the cooling effect by taking in the cooled gas and applying the cooled gas to the transfer fixing belt that is the object to be cooled. .
A heat exchanger is used for applications such as heating, evaporation, cooling, and condensation by transferring heat between two fluids through a partition wall. .
B) Multi-tubular cylindrical heat exchanger b) Double pipe heat exchanger c) Plate heat exchanger d) Other heat exchangers Use any of these heat exchangers to cool the cooled air By using it, the transfer fixing belt can be cooled more effectively than air at normal temperature.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. In this embodiment, an ion wind cooling device is used as the cooling means 20 instead of the fan in the first embodiment shown in FIG. 1, and an air current is generated using the ion wind generated by corona discharge. The transfer fixing belt, which is a cooled portion, is cooled by the air flow.
The image forming apparatus (copier) according to the third embodiment is different from the first embodiment only in the configuration of the other parts except that the cooling device 20 as a cooling unit is different. Description of each part equivalent to the illustration of the entire configuration is omitted, and the cooling device will be mainly described below.
The fan used as the cooling means in the first embodiment generates noise during its operation, and requires a large space for installation. In addition, since the air from the fan becomes a turbulent flow that diffuses, there is a limit to cooling at a pin point. In view of these various points, in this embodiment, an ion wind is generated as a cooling means and is used to cool the transfer fixing belt. Compared to a cooling device such as a fan, noise is not generated and the size can be reduced.
In other words, the ion wind cooling device used in the third embodiment functions as a cooling unit and can neutralize residual charges of the transfer fixing belt and untransferred toner, so that the cleaning and the next image forming process are excellent. There are also side effects that can be achieved.

A cooling device using ion wind will be described in detail with reference to the drawings. The ion wind cooling device illustrated in FIG. 5 uses a tungsten wire 21 (about 60 μm) extended in the width direction of the transfer and fixing belt 2 as a discharge electrode, and is positioned on the transfer and fixing belt side from the tungsten wire 21. A plurality of electrode plates 22 are provided. These electrode plates 22 are made of a plate-like conductor such as metal, and are installed so that the surface direction intersects the surface of the transfer and fixing belt 2 and is movable so that the angle of intersection can be adjusted. A high voltage (about 5 to 10 kV) is applied to a tungsten wire (hereinafter simply referred to as a wire) 21 by a discharge power source 23, and each electrode plate 22 is grounded.
When a high voltage is applied to the wire 21 by the discharge power source 23, a corona discharge is generated between the wire 21 and the electrode plate 22, and a current flows from the wire 21 toward the electrode plate 22. As a result, nitrogen and oxygen are ionized. These ionized molecules flow while colliding with the surrounding neutral molecules in the direction of the electric field generated radially from the discharge electrode 2, and in association therewith, after the ionized molecules are released, the nearby air Flows in and acts to push out air in the vicinity of the wire 21 and the electrode plate 22 in the direction of the transfer and fixing belt 2, thereby generating an air flow and generating an ion wind. At that time, the electrode plate on the end side is moved like a louver (controlled by the signal from the paper width detecting unit) (in the direction of the arrow in FIG. 5), and ion wind is applied to the transfer fixing belt in the portion corresponding to the paper width. It has come to be guided.

By this operation, there is no temperature unevenness in the longitudinal direction of the transfer and fixing belt, and the transfer and fixing belt can be efficiently cooled. At this time, since the ion wind generated by corona discharge contains ozone, it is desirable to remove ozone with an ozone filter or the like. In the above configuration, either positive or negative voltage may be applied to the wire. However, it is advantageous to apply a positive voltage because the efficiency of airflow generation can be increased.
The advantage of using the ionic wind is that there is little turbulence of the air flow and it is possible to flow uniformly to the object to be cooled. In addition, it requires less installation space than a fan and does not generate noise. In addition, it has the effect of improving the thermal conductivity of the nearby air (air layer), and the ionized gas comes into contact with it, so that residual charge on the transfer fixing belt and residual toner can be removed, which also promotes the cooling effect. Can be achieved.

FIG. 6 shows a different configuration of the ion wind cooling device, in which a needle electrode 31 is used as a discharge electrode and a high voltage is applied between the annular plate electrode 32 and a corona discharge is generated. The transfer fixing belt 2 is cooled by using ion wind generated from the tip of the needle electrode toward the flat plate electrode 32 and flowing through the central circular hole portion.
In this configuration, a small hole is provided in the flat plate electrode 32 as shown in FIG. FIG. 6B is a specific configuration diagram of an actual ion wind cooling device. As shown in the drawing, electrode pairs (needle electrode 31 and flat plate electrode 32) that can be individually controlled to energize are transferred to the transfer and fixing belt 2 as shown in FIG. The ion wind cooling device is configured by arranging a plurality of sets in a line in the width direction. During operation, the bias corresponding to the paper width of the transfer fixing belt is selectively pinpointed by controlling so that a bias is applied only to the discharge electrode at the position corresponding to the paper width in accordance with a signal from the paper width detector. Can be cooled.
The ionic wind generated by this configuration is excellent in intensive property (directivity) and can be blown locally. For this reason, it is possible to cool the portion (area) corresponding to the paper width of the transfer fixing belt pinpoint. FIG. 6B shows a state where power is selectively supplied to four electrode pairs near the center, and cooling is concentrated in a high-temperature region where the paper contacts.
In the present embodiment, one or more exhaust means (air blowing means) for releasing the air used for cooling to the outside of the apparatus in addition to the cooling means are the same as in the case of the first embodiment. It is equipped with a fan to increase the cooling effect.

According to the third embodiment described above, the temperature of the transfer fixing belt after the transfer fixing is performed by selectively cooling the appropriate width of the transfer fixing belt in contact with the paper based on the paper width signal from the paper width detecting unit. Unevenness, in particular, an increase in the paper width temperature of the transfer and fixing belt due to continuous paper feeding can be suppressed, and a good image can be provided without problems.
In particular, since the ion wind cooling device is employed, the cooling airflow is less disturbed than the fan cooling, and the cooling gas can be flowed uniformly to the object to be cooled. Moreover, noise is not generated because it takes less installation space than a fan. Further, since the gas is ionized, residual charges on the transfer and fixing belt and residual toner can be removed, and the thermal conductivity of air can be improved. This can also promote the cooling effect.
In this embodiment, the heat exchanger is attached to the gas suction side of the cooling means in the same manner as in the case of the second embodiment, so that the cooled gas is taken in and the transfer fixing that is the object to be cooled is performed. By applying the cooled gas to the belt, the cooling effect can be further enhanced. On the contrary, depending on the rating of the device and the guaranteed quality, if a sufficient cooling effect can be obtained with only the ion wind cooling device, the fan as an exhaust means provided in combination may be omitted. .

[Fourth Embodiment]
The system of the image forming unit to which the present invention is applied is not limited to the quadruple tandem system as in the above embodiments. In addition to the case shown in FIG. 1, the same advantages as described above can be obtained when the present invention is applied to an image forming apparatus of the color superimposing type on the photoconductor. FIG. 7 is a side view showing the main part of the image forming apparatus of the color superimposing type on the photoreceptor according to the fourth embodiment. The overall configuration of the image forming apparatus is well known, and only the main internal parts are shown. In addition, the same code | symbol is attached | subjected to the functional part equivalent to FIG.
In this system, the surface of a single rotating photoreceptor is uniformly charged by a charging means, and image data of a plurality of colors is sequentially written by a laser writing means to form an electrostatic latent image. Thereafter, toners of different colors are attached by a plurality of developing means to form and visualize the toner images, and the respective toner images are sequentially primary-transferred and superposed on an intermediate transfer belt as a toner image carrier. Thereafter, the transfer and fixing are collectively performed on the recording medium by a transfer fixing device.

The image forming unit of the color-superimposing method on the photoreceptor shown in FIG. 7 is a general one, and the configuration and function of each unit are well known, so the description is simplified, and only the cooling device for the transfer fixing belt 2 is described in detail. explain.
The color copier shown in FIG. 7 also has an image forming unit 1A located at the center of the apparatus main body, a sheet feeding unit 1B located below the image forming unit 1A, and an image reading unit not shown located above. Yes. The image forming unit 1A is provided with a transfer fixing belt 2 as an intermediate transfer member that is provided so as to be able to circulate and provide a transfer surface extending in the horizontal direction. A configuration is provided for forming each color image having a complementary color relationship with the color.
That is, a single photoconductor 3 </ b> A is disposed in pressure contact with the transfer surface portion of the transfer fixing belt 2. A transfer roller 7A is a primary transfer device. On the circumference of the transfer roller 7A, developing devices 6Y, 6M, 6C and 6K as image carriers capable of carrying toner images of complementary colors (yellow, magenta, cyan, black) are transferred surface portions. Are juxtaposed in order. Further, around the photoreceptor 3A, a charging device and a cleaning device (not shown) for performing image forming processing in the rotation process are arranged. Above the photoreceptor 3A, writing devices 5Y, 5M, 5C, and 5K as optical writing means are arranged.

The surface of the photoreceptor 3A is uniformly charged by a charging device (not shown), and then an electrostatic latent image is sequentially formed on the photoreceptor 3A for each color based on image information from the image reading unit, and development for each color is performed. The toner image is formed by the apparatus 6 in an overlapping manner. The color visible image (toner image) formed in such a manner is superimposed on the transfer fixing belt 2 by the primary transfer device 7A to which a predetermined bias is applied. The toner remaining on the photoconductor 3A after the transfer is removed by a cleaning device (not shown), and the potential of the photoconductor 3A is initialized by a charge eliminating lamp (not shown) after the transfer to prepare for the next image forming process. The color toner image on the transfer fixing belt 2 that has been primarily transferred is directed to the transfer fixing portion while being heated by the heating unit 13, and is transferred and fixed to the transfer sheet P when passing through the nip, and is conveyed to the discharge path. On the other hand, after the transfer and fixing, the belt-like portion corresponding to the width of the transfer paper is intensively cooled by the downstream cooling means 20 in the same manner as in the first embodiment.
The transfer fixing device in the present embodiment has the same configuration as that of the first embodiment (differences in the size of each part, strict arrangement position size, etc.), and the pressure fixing roller 24 forming the transfer fixing belt 2 and the nip N. , A heating means (heating body) 13, a blower fan 20 as a cooling means (which may of course be an ion wind cooling device as described above), an exhaust fan (exhaust means) 26, and a paper width detection means not shown The image processing unit and the cooling control unit are functioning.

In this embodiment, the paper width detection is formed in the image processing unit from an input image signal (image information from the image reading unit or a print job from an external client device) or from image data obtained by rasterizing the input image signal. The width of the image to be detected is detected and the paper width signal is generated and output. Other configurations and functions of the above-described units are the same as those of the first embodiment described above, and thus description thereof will not be repeated. The cooling means 20 (for example, an axial fan, see FIG. 2) concentrates air only on a belt-like portion corresponding to the transfer sheet width of the transfer fixing belt 2 to cool the transfer fixing belt 2 efficiently. Most of the air that has cooled the transfer fixing belt 2 is discharged out of the apparatus by the exhaust fan 26.
Incidentally, the color superimposing method on the photoconductor of the fourth embodiment is a series of processes from charging, exposure (writing), and development to one color toner as an image forming operation on a single photoconductor. For toner, the same process is performed individually on the same photoconductor. On the other hand, the quadruple tandem system in each of the above embodiments performs an image forming process on one photoconductor for each color, performs secondary transfer fixing from the intermediate transfer member to the transfer fixing member, and then transfers from the transfer fixing member. The material is tertiary-transfer-fixed on the material, and a plurality of photoreceptors for each color are required. Compared to this method, the on-photoreceptor color superposition method shown in this embodiment is also suitable for high-speed compatibility, and further, because it is composed of a single photoconductor, it is possible to save space. There is an advantage that leads to low cost of the machine.

  The present invention has been described with reference to a plurality of embodiments. However, the present invention is not limited to the above-described embodiments, and within the scope of the technical idea of the present invention, other than suggested in the above-described embodiments. However, it is obvious that the above embodiments can be modified as appropriate. In addition, the number, position, shape, and the like of the constituent members are not limited to the above embodiments, and can be set to a number, position, shape, and the like that are suitable for carrying out the present invention. Further, the present invention is applied to a transfer fixing device including only one of the heating unit and the recording medium heating unit when temperature unevenness in the width direction of the transfer fixing member may occur. Thus, it is possible to reliably prevent adverse effects on the next image forming process.

FIG. 2 is a side view showing an internal essential part of the image forming apparatus (color copying machine) according to the first embodiment. It is a typical block diagram which shows the cooling means which concerns on 1st Embodiment. It is a block diagram which shows typically the modification of the cooling means which concerns on 1st Embodiment. It is a block diagram which shows typically the another modification of the cooling means which concerns on 1st Embodiment. It is a block diagram which shows the ion wind cooling device in 3rd Embodiment. (A) (b) is a block diagram which shows the aspect from which an ion wind cooling device differs. FIG. 2 is a side view illustrating a main part of the image forming apparatus of the color superimposing type on the photoreceptor according to the exemplary embodiment. FIG. 6 is an enlarged view of the vicinity of a transfer fixing portion according to another paper heating unit according to the embodiment. It is an enlarged view explaining another paper heating means. It is an enlarged view explaining another paper heating means. It is an enlarged view explaining another paper heating means.

Explanation of symbols

1A Image forming unit 1B Paper feeding unit 2 Transfer fixing belt (transfer fixing member)
3Y, 3M, 3C, 3K, (3A) Photoconductor 4 (4Y, 4M, 4C, 4K) Charging device 5 (5Y, 5M, 5C, 5K) Writing device 6 (6Y, 6M, 6C, 6K) Developing device 7 7A Primary transfer device (transfer roller)
DESCRIPTION OF SYMBOLS 8 Cleaning apparatus 9, 10 Driven roller 11 Drive roller 12 Cleaning apparatus 13 Heating apparatus (heating means)
20 Cooling means (transfer fixing member cooling means)
21 Tungsten wire (discharge electrode)
22 Electrode plate 23 Discharge power supply 24 Pressure roller (pressure member)
26 Exhaust means (exhaust fan)
31 Needle electrode 32 Plate electrode,
120 Heating roller (paper heating means)
210 Leveling roller (Temperature leveling means)
N nip P recording medium

Claims (7)

A transfer fixing device for transferring and fixing a toner image to a transfer fixing surface of a recording medium,
A transfer and fixing member on which an unfixed toner image is formed on the surface;
Heating means for heating an unfixed toner image on the transfer fixing member;
A recording medium heating means for preheating the surface of the recording medium before transferring and fixing the unfixed toner image to the recording medium ;
A pressure member that forms a nip portion that pressurizes the recording medium with the transfer fixing member;
In the transfer fixing device comprising:
For cooling said transfuse member after transferring fixed on the recording medium an unfixed toner image in the previous SL nip, and adjustably configured cooling means a cooling width,
And a cooling control unit that controls a cooling width of the transfer fixing member based on either a paper width of a recording medium or a print image width determined by print image data. A paper width detector that detects the width of the recording medium and outputs a paper width signal;
The cooling control unit controls the cooling width of the transfer fixing member based on either a paper width signal from the paper width detection unit or a print image width signal obtained from print image data. The transfer fixing device according to claim 1.   The transfer fixing device according to claim 1, wherein the cooling unit is an ion wind cooling device that cools using ion wind generated by corona discharge.   The transfer fixing device according to claim 1, wherein the cooling unit uses a gas flow generated by a blower for cooling.   5. The transfer fixing device according to claim 3, further comprising a heat exchanger that cools a gas, wherein a gas flow or an ionic wind cooled by the heat exchanger is used for cooling the transfer fixing member.   6. The transfer fixing device according to claim 1, further comprising an exhaust unit for discharging air to the outside of the main body of the transfer fixing device built-in apparatus.   An electrophotographic image forming apparatus comprising the transfer fixing apparatus according to claim 1.

Images