JP2012037545A - Image gloss controller, fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image gloss controller by a cooling and peeling method for preventing the decrease of the gloss of a fixed image by making it possible to closely hold a recording medium and an endless belt for imparting the gloss and to provide a fixing device and an image forming apparatus.SOLUTION: The image forming apparatus includes: an endless belt 1 stretched on a plurality of rollers 2a, 2b and 2c; a pressure roller 3 coming into press-contact with the two rollers 2a and 2b through the endless belt 1 to form a nip portion N through which the recording medium on which a toner image is fixed passes; non-contact thermistors 5a and 5b detecting the surface temperature of the endless belt 1; a heat source 2h heating the endless belt 1 based on the detection results of the non-contact thermistors 5a and 5b at a nip portion entrance N1; and cooling devices 4a and 4b cooling the endless belt 1 and the pressure roller 3 in an intermediate nip portion N2 formed in such a manner that the endless belt 1 between the two rollers 2a and 2b forming the nip portion N and the pressure roller 3 are brought into close contact with each other.

Description

  The present invention relates to an image gloss control device that controls image gloss on a recording medium on which an image is fixed, a fixing device including the image gloss control device, a copier, a printer, a facsimile including the fixing device, or a combination thereof. In particular, the present invention relates to an image forming apparatus that forms an image on various recording media having different glossiness levels.

  Conventionally, an image forming apparatus using an electrophotographic method has been put into practical use and has become a publicly known technique. In the image forming process, an electrostatic latent image is formed on the surface of the photosensitive drum as an image carrier, and the electrostatic latent image on the photosensitive drum is developed with a toner as a developer to be visualized and developed. The transferred image is transferred to a recording medium (also referred to as recording paper, recording material, paper, or transfer paper) by a transfer device to carry the image, and the toner image on the recording medium is fixed by a fixing device using pressure, heat, or the like. It is established by the process.

  The fixing device is provided with a fixing rotator constituted by opposing rollers or belts or a combination thereof, and sandwiches the recording medium and applies heat and pressure to fix the toner image on the recording medium.

As an example of the fixing method, FIG. 1 shows a known belt fixing method.
A fixing belt (fixing body) 91c including a heating roller 91f having a heater 91e as a heat source, a fixing roller 91b having a rubber layer on the surface, and a pressure roller (pressing body) in contact with the fixing belt 91c Reference numeral 91a denotes a fixing rotator. The toner-transferred recording medium that has reached the fixing device enters the nip between the fixing belt 91c and the pressure roller 91a, and the transferred toner image is heated and pressed and fixed in the process of passing the recording medium through the fixing nip. It is like that.

  However, the gloss of an image obtained with a general fixing device is often insufficient. This is presumably because the toner once melted in the fixing nip is naturally cooled after passing through the fixing nip, and aggregates and generates undulation in this cooling process.

In order to prevent such a decrease in gloss, the following methods (1) to (3) are often used in the prior art.
(1) Multistage fixing method (2) Cooling and peeling method (3) Method of applying a processing sheet to a recording medium

  However, (1) the multi-stage fixing method has a drawback that it is difficult to control the gloss, although the gloss can be increased. Also, even if the image is fixed multiple times and the image surface is sufficiently smooth, the gloss of the image tends to decrease due to the aggregation of the toner during cooling. It was difficult to do. Similarly, (3) even when the processing sheet is applied to the recording medium, the output gloss is uniform and cannot be controlled. Although it is possible to increase the range of gloss control by increasing the types of processing sheets, it is not a good solution because it leads to an increase in size and complexity of the apparatus.

  For these problems, (2) In the cooling and peeling method, the recording medium is brought into close contact with a belt having a smooth surface layer, and the toner is peeled off after cooling and solidifying. Therefore, the gloss is controlled by the peeling temperature compared with the above two methods. It is considered possible. However, the cooling and peeling method has a problem of maintaining the adhesion between the recording medium and the belt.

  Further, all of the above three conventional techniques have a problem that the glossiness of the first surface is reduced when the paper is passed on both sides, or the glossiness of the first surface and the second surface is not uniform. At the time of double-sided paper passing to form an image on both sides of the recording medium, the recording medium passes through the fixing device twice. For example, the conveyance path is “fixing device (first surface fixing) → gloss applying device ( In the case of “first surface gloss imparting) → fixing device (second surface fixing) → gloss imparting device (second surface gloss imparting)”, the gloss of the first surface may be lost by fixing the second surface. Even if the gloss of the first surface is not greatly lost, the gloss differs because the history of the amount of heat absorbed by the toner on the recording medium is different on the first and second surfaces of the output recording medium, They cannot be controlled.

  The ideal conveyance path for double-sided paper passing is that after fixing the first surface and the second surface, the recording medium is inserted into the gloss applying device to obtain a desired gloss on both sides simultaneously. This shortens the transport path and increases productivity. Even in this case, since the history of the amount of heat absorbed by the toner on the first surface and the second surface immediately before the recording medium is inserted into the gloss applying device is different, multi-stage fixing is performed by further applying heat from here. In the method, it is considered difficult to make both sides have the same gloss.

  In contrast to the above-described problems of the prior art relating to gloss application, in Patent Document 1, as shown in FIG. 2, as shown in FIG. A configuration has been proposed that is arranged at the subsequent stage of the attaching means 10, and the gloss control of the first surface and the second surface during the double-sided sheet passing is enabled by the image gloss adjusting means. However, in this method, there is no means for applying pressure between the belts (reference numerals 31 and 41) between the stretching members, and the adhesion between the upper and lower belts is insufficient, that is, the adhesion between the recording medium and the endless belt surface is insufficient. It becomes insufficient. In the cooling and peeling method, if the adhesion between the smooth belt surface and the recording medium is insufficient, uneven glossiness occurs.

  Further, in Patent Document 2, as shown in FIG. 3, the pressure member (reference numeral 154) of the glossing device is separated at the time of double-sided paper passing, and the first surface that has already been glossed is heated and melted again without being melted again. There has been proposed a structure in which a smoothing device that imparts gloss only to a fixing device is incorporated in a fixing device. However, when the pressurizing members are separated, there is a concern about deterioration in transportability, deterioration in adhesion to the belt member for imparting gloss, and the like.

  Further, in both of the inventions described in Patent Document 1 and Patent Document 2, when the recording medium is thick or the surface property is poor, the adhesion to the endless belt member is further deteriorated, resulting in abnormal images such as gloss unevenness. It seems to be connected.

  In particular, when the recording medium is thick, the heat capacity of the recording medium itself becomes large. Therefore, in the case of the gloss applying device using the cooling and peeling means as in Patent Document 1, the cooling time must be increased or the cooling capacity must be improved. I must. When the cooling time is lengthened, the cooling application area must be lengthened or the conveyance speed of the recording medium must be reduced. Further, in the configuration of Patent Document 1, since the cooling application region cannot be lengthened, in order to lengthen the cooling time, it is necessary to reduce the conveyance speed of the recording medium, which has the disadvantage of reducing productivity. is there. Further, in order to improve the cooling capacity, it is necessary to improve the performance of a cooling device such as a heat sink or a cooling fan, so there are disadvantages such as an increase in cost and an increase in the size of the device.

The present invention has been made in view of the above-described problems in the prior art, and allows the recording medium and the endless belt for giving glossiness to be held in close contact with each other. It is an object of the present invention to provide a gloss control device, a fixing device including the image gloss control device, and an image forming apparatus including the fixing device.
In addition, the present invention prevents a decrease in gloss on the first side during double-sided printing, controls the in-image gloss on the first side and the second side to a uniform and desired level, and further, for example, the recording medium is cardboard. Thus, an object of the present invention is to provide an image gloss control apparatus that can cope with a large heat capacity and a long time for cooling without reducing productivity.

The present invention provided to solve the above problems is as follows. In addition, the site | part and code | symbol etc. which respond | correspond in the form for implementing this invention in a parenthesis are shown.
[1] An endless belt (endless belt 1) stretched around a plurality of stretching members (rollers 2a, 2b, 2c) and at least two of the plurality of stretching members via the endless belt A pressure member (pressure roller 3) that forms a nip portion (nip portion N) through which a recording medium having a toner image fixed thereon is pressed against the two stretching members (rollers 2a and 2b); and the endless belt Temperature detection means (non-contact thermistors 5a, 5b) for detecting the surface temperature of the nip, and the endless based on the detection result of the temperature detection means upstream of the nip inlet (nip inlet N1) or the nip. An intermediate nip region (intermediate nip region) formed by the belt heating means (heat source 2h) for heating the belt and the endless belt and the pressure member between the two stretch members forming the nip portion. Nip part N 2) an image gloss control device (image gloss control device 10, FIG. 4), comprising: an endless belt; and cooling means (cooling devices 4a and 4b) for cooling at least one of the pressure member. ).
[2] The image gloss control device according to [1], wherein a mean square roughness Rq of the surface of the endless belt is 0.3 μm or less.
[3] The image gloss control device according to [1], wherein a root mean square roughness Rq of the surface of the pressure member is 0.3 μm or less.
[4] The image gloss control according to [1], further comprising a pressure member heating unit (induction heating device 3h) that heats the pressure member at the inlet of the nip portion or upstream of the nip portion. Device (Figure 4).
[5] An intermediate nip width changing mechanism for changing the nip width of the intermediate nip region by moving the stretching member (roller 2b) on the nip outlet (nip outlet N3) side in the outer circumferential direction of the pressure member. The image gloss control device according to any one of [1] to [4], wherein the image gloss control device (FIGS. 5 and 6) is provided.
[6] The temperature detection means is a non-contact thermometer (non-contact thermistor 5b) disposed at the nip outlet, so that the distance from the endless belt at the nip outlet is constant. The image gloss control device according to [5], wherein the image gloss control device moves in conjunction with a change in the nip width of the intermediate nip region by the intermediate nip width change mechanism (FIG. 7).
[7] Separation member (separation member 12) that moves in conjunction with the nip width change of the intermediate nip region by the intermediate nip width change mechanism so that the distance between the nip portion outlet portion and the endless belt is constant. The image gloss control device according to [5] or [6] (FIG. 8), comprising:
[8] The system according to [1], further comprising an inlet nip width changing mechanism that changes a nip width of the nip portion inlet by changing a pressure contact state of the tension member on the nip portion inlet side with the pressure member. To [7] The image gloss control device (FIG. 9).
[9] A fixing device (fixing device 100, FIG. 10) including the image gloss control device (image gloss control device 10) according to any one of [1] to [8].
[10] An image forming apparatus (image forming apparatus 200, FIG. 11) comprising the fixing apparatus (fixing apparatus 100) according to [9].

According to the image gloss control device of the present invention, the pressure member presses the two tension members to form a nip portion, and the endless belt and the pressure member between the two tension members are in the intermediate nip region. Therefore, the nip region having a predetermined nip width can be secured as a region for cooling the recording medium, and after the recording medium heated at the nip portion entrance is appropriately cooled, the recording medium is peeled off from the endless belt, It is possible to prevent a reduction in gloss of the image. In addition, by changing the nip width of the intermediate nip region, it is possible to deal with recording media having various thicknesses and obtain desired gloss.
Further, according to the fixing device of the present invention, since the image gloss control device of the present invention is provided, it is possible to prevent a decrease in gloss of the fixed image immediately after fixing and to obtain a desired gloss.
Further, according to the image forming apparatus of the present invention, since the fixing device 100 of the present invention is provided, an image controlled to have a desired gloss can be formed.

It is sectional drawing which shows the structure of the conventional belt fixing apparatus. FIG. 6 is a cross-sectional view illustrating a configuration of a conventional fixing device having an image gloss adjusting unit. It is sectional drawing which shows the structure of the conventional fixing device which has a smoothing apparatus. It is sectional drawing which shows the structure of the image gloss control apparatus which concerns on this invention. It is sectional drawing which shows the structure of the intermediate nip width change mechanism provided in the image gloss control apparatus of this invention. It is sectional drawing which shows the mode of the intermediate nip width change by the intermediate nip width change mechanism of FIG. It is sectional drawing which shows the structure of the non-contact thermistor holding | maintenance bracket provided in the image gloss control apparatus of this invention. It is sectional drawing which shows the structure of the separation member holding | maintenance bracket provided in the image gloss control apparatus of this invention. It is sectional drawing which shows the structure of the entrance nip width change mechanism provided in the image gloss control apparatus of this invention. FIG. 2 is a cross-sectional view illustrating a configuration of a fixing device according to the present invention. 1 is a cross-sectional view illustrating a configuration of an image forming apparatus according to the present invention.

The configuration of the image gloss control device according to the present invention will be described below.
FIG. 4 is a cross-sectional view showing the configuration of the image gloss control device according to the present invention.
As shown in FIG. 4, the image gloss control device 10 includes an endless belt 1 that is stretched between rollers 2 a, 2 b, and 2 c that are a plurality of belt stretching members, and a plurality of rollers 2 a via the endless belt 1. , 2b, 2c, a pressure member that is a pressure member that forms a nip portion N that presses against at least two rollers 2a, 2b to pass a recording medium on which a toner image (hereinafter also simply referred to as an image) is fixed. Based on the detection results of the roller 3, the non-contact thermistors 5a and 5b, which are temperature detecting means for detecting the surface temperature of the endless belt 1, and the detection results of the non-contact thermistors 5a and 5b, rather than the nip inlet N1 or the nip inlet N1. The heat source 2h, which is a belt heating means for heating the endless belt 1 on the upstream side, and the endless belt 1 and the pressure roller 3 between the two rollers 2a, 2b forming the nip portion N are in close contact with each other. Cooling apparatus 4a in the intermediate nip portion N2 is a cooling means for cooling the endless belt 1 and the pressure roller 3 is provided with a 4b, and.

  Here, the endless belt 1 has, as a cross-sectional structure, a releasability so that a base material using a metal material such as nickel or stainless steel or a resin material such as polyimide and a toner provided on the surface layer do not adhere. And a release layer made of a fluororesin such as perfluoroalkoxy (PFA) or polytetrafluoroethylene (PTFE).

  Further, the surface of the endless belt 1 needs to be sufficiently smooth in order to give gloss to an image to be adhered, for example, the root mean square roughness Rq of the surface of the endless belt 1 is 0.3 μm or less. Is preferable, and it is more preferable that it is 0.1 micrometer or less.

  In the gloss imparting by the cooling and peeling method employed in the present invention, the surface in contact with the image surface, that is, the front surface of the endless belt 1 (the first surface of the recording medium in the case of second surface fixing by double-sided printing) When the image on the side is a problem, the roughness of the surface of the pressure roller 3 is also important. For example, to achieve a glossiness of about 70%, the root mean square roughness (Rq) needs to be about 0.3 μm. To achieve a glossiness of 90% or more, the root mean square roughness (Rq) is 0. .1 or less is desirable.

  If the endless belt 1 is composed only of the base material and the release layer, the heat capacity of the endless belt 1 is reduced, and the temperature followability at the time of heating by the heat source 2h and cooling by the cooling device 4a is improved. As a result, there is a problem in that fine unevenness on the surface of the endless belt 1 is transferred to an image on a recording medium in which the endless belt 1 is in close contact, and a crusty skin-like mark remains on the solid portion of the image. Therefore, an elastic layer made of silicone rubber or the like having a thickness of 100 μm or more may be provided between the base material of the endless belt 1 and the release layer. As a result, when the image is brought into close contact with the endless belt 1, the elastic layer is deformed and fine unevenness on the surface of the endless belt 1 is absorbed.

  The rollers 2a, 2b and 2c are aluminum or iron hollow rollers, and the rollers 2a and 2b are in contact with the pressure roller 3 via the endless belt 1, respectively, and enter the nip portion N1 and the nip portion outlet. N3 is formed. The roller 2a has a built-in heat source 2h which is a halogen heater for heating the endless belt 1 therein. The heat source 2h may be an induction heating device (IH), and the installation location in that case may be either inside or outside the roller 2a.

  The pressure roller 3 is a cylindrical roller in which a release layer made of PFA, PTFE or the like or a heat-resistant layer made of polyimide (PI) or the like is usually provided on a core metal made of aluminum or iron.

  Further, the pressure roller 3 presses the rollers 2 a and 2 b via the endless belt 1 by a pressing means (not shown), thereby forming a nip portion N.

  The nip portion N includes a nip portion inlet N1 formed by the pressure roller 3 pressing the roller 2a, a nip portion outlet N3 formed by the pressure roller 3 pressing the roller 2b, and two rollers 2a. , 2b, and an intermediate nip portion N2 which is an intermediate nip region having a predetermined nip width formed by the endless belt 1 and the pressure roller 3 being in close contact with each other. Since the pressure roller 3 is pressed against the rollers 2a and 2b at the nip inlet N1 and the nip outlet N3, a predetermined nip pressure is provided. On the other hand, since the pressure roller 3 is pressed against only the flexible endless belt 1 at the intermediate nip portion N2, the pressure is relatively lower than the nip portion inlet N1 and the nip portion outlet N3. However, since the pressure roller 3 is in pressure contact with the endless belt 1 to which a predetermined tension is applied, the endless belt 1 is in close contact with the pressure roller 3 at the intermediate nip portion N2.

  The cooling device 4a cools the endless belt 1 in the intermediate nip portion N2 from the inner peripheral side, and may be, for example, a general heat sink or a cooling fan. The cooling device 4b cools the pressure roller 3 in the intermediate nip portion N2 from the inside, and may be a general heat sink, a cooling fan, or the like.

  4 shows a configuration in which the cooling devices 4a and 4b are arranged to cool the endless belt 1 and the pressure roller 3 in the intermediate nip portion N2, respectively. As long as the performance of cooling and solidifying is obtained, either one or a configuration of natural cooling may be used. However, in the case of double-sided printing, since the images are in close contact with the endless belt 1 and the pressure roller 3, the cooling devices 4a and 4b are arranged in order to give the same gloss to both sides of the recording medium. Is preferred.

  Further, the temperature detecting means for detecting the surface temperature of the endless belt 1 is premised on imparting image gloss to the surface of the endless belt 1, so that the temperature of the endless belt 1 is not contacted with the surface of the endless belt 1. Detectable non-contact thermistors 5a and 5b are employed. Although a contact-type temperature detecting means may be used, in that case, it is necessary to install the temperature detecting means outside the image contact range (image forming range) of the endless belt 1, which reduces the size of the apparatus. It is not preferable from the point.

In the image gloss control apparatus 10 having the above configuration, when the image gloss control apparatus 10 is driven, first, the pressure roller 3 discharges the recording medium P on which the image is fixed (counterclockwise direction in FIG. 4). And the endless belt 1 is swung around. Alternatively, the endless belt 1 is rotated in the direction in which the recording medium P is ejected (in the clockwise direction in FIG. 1) in a state where an appropriate tension is applied by rotating the roller 2a in the clockwise direction in the drawing. Also good.
In addition, predetermined power is supplied to the heat source 2h based on the detection result of the non-contact thermistor 5b (temperature of the endless belt 1 at the nip portion outlet N3), and the heat generation of the heat source 2h causes the endless belt 1 to be non-contact. Heating is performed until the temperature detected by the thermistor 5a reaches a predetermined temperature (for example, a high temperature (100 ° C. to 130 ° C.) at which the toner does not aggregate).
Further, the cooling devices 4a and 4b are activated to cool the endless belt 1 and the pressure roller 3 in the intermediate nip portion N2.

When a recording medium on which an image is fixed (in this case, a recording medium printed on one side) is carried into the image gloss control apparatus 10 in such a state, first, the recording medium is heated from the endless belt 1 at the nip portion entrance N1. In response, the image on the recording medium is softened. At the same time, since the softened image is pressed against the smooth surface of the endless belt 1, it is smoothed.
Subsequently, the recording medium is sandwiched between the endless belt 1 and the pressure roller 3 at the intermediate nip portion N2, and is conveyed while being cooled while the image is in close contact with the endless belt 1. Therefore, toner aggregation proceeds while the image on the recording medium is leveled on the smooth surface of the endless belt 1.
Next, the recording medium is peeled off from the endless belt 1 by the curvature of the roller 2 b at the nip exit N <b> 3 and discharged from the image gloss control device 10. At this time, the recording medium is cooled to a predetermined temperature (peeling temperature), and the glossiness of the image can be prevented from being lowered.

  In addition, when controlling the gloss of the image on each side of the recording medium on which images are formed on both sides (printed on both sides), the image gloss control device 10 detects the surface temperature of the pressure roller 3. Non-contact thermistors 6a and 6b, and pressure member heating means for heating the heating roller 3 upstream of the nip inlet N1 or the nip inlet N1 based on the detection results of the non-contact thermistors 6a and 6b. And an induction heating device 3h.

  As a result, the surface of the pressure roller 3 needs to be sufficiently smooth in order to give gloss to an image that adheres. For example, the root mean square roughness Rq of the surface of the pressure roller 3 is 0.3 μm or less. Preferably, it is 0.1 μm or less. This is because the image on the first surface side of the recording medium in the case of the second surface fixing in duplex printing is in close contact with the pressure roller 3 in the image gloss control device 10.

  As in the case of the endless belt 1, in order to prevent the generation of a crushed skin image when the image on the recording medium is in close contact, the elasticity made of silicone rubber or the like that absorbs subtle irregularities on the surface of the pressure roller 3. A layer (thickness of 100 μm or more) is preferably provided between the cored bar and the release layer (or heat-resistant layer).

  Further, in order to improve the temperature followability when heating by the pressure member heating means (induction heating device 3h) of the pressure roller 3 or cooling by the cooling device 4b, it is desirable to reduce the heat capacity of the heating roller 3. Specifically, it is preferable to reduce the heat capacity by hollowing the core metal part constituting the pressure roller 3 or thinning the surface layer material.

  Accordingly, the temperatures of the endless belt 1 and the pressure roller 3 at the nip portion entrance N1 can be made exactly equal, and the recording medium that is in pressure contact with the endless belt 1 and the pressure roller 3 at the nip portion entrance N1 can be used. The image can be smoothed in the same way, and the same gloss can be imparted.

  Although FIG. 4 shows a configuration in which the induction heating device 3h is disposed outside the pressure roller 3 as the pressure member heating means, the present invention is not limited to this. For example, the pressure member heating means may be a normal halogen heater or a directional carbon heater, and may be disposed inside or outside the pressure roller 3. However, since it is necessary to strictly control the temperature at the nip inlet N1 of the image gloss control device 10, it is added to the position near the nip inlet N1 as shown in FIG. It is preferable to arrange a pressure member heating means.

  Further, the image gloss control device 10 moves the roller 2b, which is a belt stretching member on the nip portion outlet N3 side, in the outer peripheral direction of the pressure roller 3 to change the nip width of the intermediate nip portion N2. It is preferable to provide.

FIG. 5 shows the configuration of the intermediate nip width changing mechanism.
The intermediate nip width changing mechanism has an eccentric cam 7b that supports the roller shaft 2bj of the roller 2b and one end connected to the roller shaft 2bj, and its elastic force acts in a direction to press the roller shaft 2bj toward the eccentric cam 7b. A spring member 8b, which is a spring with the other end fixed thereto, a groove 9b in which the roller shaft 2bj can slide and move, an eccentric cam 7c for supporting the roller shaft 2cj of the roller 2c, and one end connected to the roller shaft 2cj. A spring member 8c, which is a spring with the other end fixed so that the elastic force acts in a direction to press the roller shaft 2cj toward the eccentric cam 7c, and a groove 9c in which the roller shaft 2cj is slidably movable. . The spring members 8b and 8c are arranged so that an elastic force acts so as to push the roller shafts 2bj and 2cj in a direction in which tension is applied to the endless belt 1.

  Here, the roller 2b is positioned in a state where the roller shaft 2bj inserted into the groove 9b is sandwiched between the eccentric cam 7b and the spring member 8b. That is, the roller shaft 2bj is stationary while being pressed against the eccentric cam 7b by the elastic force of the spring member 8b, and the groove 9b remains sandwiched between the eccentric cam 7b and the spring member 8b by the rotation of the eccentric cam 7b. To move. At this time, the groove 9b is provided so that the roller shaft 2bj moves with the distance from the rotation shaft center of the pressure roller 3 kept constant (r), so as shown in FIG. Moves along the outer circumference of the pressure roller 3. Therefore, when the eccentric cam 7b is rotated by a predetermined angle, the nip width of the intermediate nip portion N2 can be changed by a predetermined width without changing the contact force between the endless belt 1 and the pressure roller 3 at the intermediate nip portion N2. it can.

  On the other hand, the roller 2c is positioned in a state where the roller shaft 2cj inserted into the groove 9c is sandwiched between the eccentric cam 7c and the spring member 8c. That is, the roller shaft 2cj is stationary while being pressed against the eccentric cam 7c by the elastic force of the spring member 8c, and the groove 9c remains sandwiched between the eccentric cam 7c and the spring member 8c by the rotation of the eccentric cam 7c. To move. At this time, the groove 9c is provided so that the roller shaft 2cj can move in the direction in which the roller shaft 2cj approaches the pressure roller 3, and the roller 2c approaches the pressure roller 3 as the roller 2b moves as shown in FIG. To move in the direction. Thereby, even if the roller 2b moves along the roller outer periphery of the pressure roller 3, the tension of the endless belt 1 having almost no ductility can be kept constant.

According to such an intermediate nip width changing mechanism, the distance between the endless belt 1 and the pressure roller 3 is conveyed while being cooled while being in close contact with the endless belt 1, that is, the nip of the intermediate nip portion N2. The width can be arbitrarily changed. As a result, the temperature (peeling temperature) at which the recording medium is peeled from the endless belt 1 can be adjusted by the curvature of the roller 2b, and a desired image gloss can be obtained. Obtainable. That is, if the peeling temperature is a temperature at which the toner of the image is completely aggregated, a highly glossy image according to the smoothness of the surface of the endless belt 1 is obtained. If the toner is a temperature at which the toner is aggregated halfway, aggregation proceeds thereafter. As a result, the image becomes slightly less glossy.
Alternatively, the nip width of the intermediate nip portion N2 may be changed according to the heat capacity of the recording medium. That is, when a recording medium having a thickness greater than the standard thickness is passed, the nip width is changed so as to be longer than the nip width of the intermediate nip portion N2 when the recording medium having a standard thickness is passed. Good. This makes it possible to obtain the same glossy image even if the recording media have different thicknesses.

  In addition, although the eccentric cam is used in FIG. 5 as a means for changing the position of the rollers 2b and 2c, it may be replaced with a position changing mechanism by a linear motion using a solenoid.

  Further, since the position of the endless belt 1 at the nip portion outlet N3 is also moved by the intermediate nip width changing mechanism, the non-contact thermistor 5b disposed on the nip portion outlet N3 side is connected to the endless portion of the nip portion outlet N3. It is preferable to provide a non-contact thermistor holding bracket that moves in conjunction with the nip width change of the intermediate nip portion N2 by the intermediate nip width changing mechanism so that the distance from the belt 1 is constant.

FIG. 7 is a schematic view showing the configuration of the non-contact thermistor holding bracket.
The non-contact thermistor holding bracket 11 is an arm member in which the rotation center 11a is attached to the roller shaft 3j of the pressure roller 3, and the roller shaft 2bj of the roller 2b is connected to the rotating arm portion 11b. The arm portion 11b holds a non-contact thermistor 5b so that the distance from the roller shaft 2bj is constant (L).

  Here, when the roller 2b moves so as to change the nip width of the intermediate nip portion N2 by the intermediate nip width changing mechanism, the arm member 11 moves around the roller shaft 3j of the pressure roller 3 as the roller shaft 2bj moves. It starts to rotate. At this time, the non-contact thermistor 5b held by the arm portion 11b also rotates while maintaining the distance L from the center of the roller shaft 2bj, so that the distance between the nip portion outlet N3 portion and the endless belt 1 is also constant. To be kept.

  Thereby, even if the nip width of the intermediate nip portion N2 is changed, the non-contact thermistor 5b can accurately detect the surface temperature of the endless belt 1, and by extension, the stable endless belt 1 of the heat source 2h can be detected. Heating can be performed.

  By the way, at the nip exit N3, the recording medium peels off from the endless belt 1 due to the curvature of the roller 2b. However, when a wide paper handling ability from thin paper to thick paper is required, especially in the thin paper, the image gloss control device 10 is used. In addition, a recording medium separating mechanism is necessary, and it is preferable to provide a separating member that is arranged close to the endless belt 1 in a non-contact state.

  However, since the position of the endless belt 1 at the nip portion outlet N3 is moved with the change of the nip width of the intermediate nip portion N2 by the intermediate nip width changing mechanism, the distance between the nip portion outlet N3 and the endless belt 1 is constant. It is preferable that a separation member that moves in conjunction with the nip width change of the intermediate nip portion N2 by the intermediate nip width change mechanism is provided. More specifically, the separation member 12 arranged on the nip portion outlet N3 side is niped by the intermediate nip portion N2 by the intermediate nip width changing mechanism so that the distance between the nip portion outlet N3 portion and the endless belt 1 is constant. A separation member holding bracket that moves in conjunction with the width change may be provided.

FIG. 8 is a schematic view showing the configuration of the separation member holding bracket.
The separation member holding bracket 11 ′ is an arm member in which the rotation center 11a ′ is attached to the roller shaft 3j of the pressure roller 3 and the roller shaft 2bj of the roller 2b is connected to the rotating arm portion 11b ′. The arm portion 11b ′ holds the separation member 12 so that the distance between the tip portion and the roller shaft 2bj is constant (L ′).

  Here, when the roller 2b moves so as to change the nip width of the intermediate nip portion N2 by the intermediate nip width changing mechanism, the arm member 11 ′ is centered on the roller shaft 3j of the pressure roller 3 as the roller shaft 2bj moves. To rotate. At this time, since the separation member 12 held by the arm portion 11b ′ also rotates and maintains the distance L ′ between the tip portion and the center of the roller shaft 2bj, the endless belt 1 at the nip portion outlet N3 portion The distance (separation plate gap) is also kept constant.

  As a result, even if the nip width of the intermediate nip portion N2 is changed, the leading end portion of the separation member 12 is accurately placed close to the endless belt 1 at the nip portion outlet N3, and the recording medium is reliably endless. It can be peeled from the belt 1.

  In the arm portion 11b ′ of the separation member holding bracket 11 ′, as shown in FIG. 8, the portion other than the portion that holds the separation member 12 and the distance from the roller shaft 2bj is constant (L ″). It is preferable to hold the non-contact thermistor 5b. Thereby, similarly to the case of FIG. 7, even if the nip width of the intermediate nip portion N2 is changed, the non-contact thermistor 5b can detect the surface temperature of the endless belt 1 with high accuracy.

  The image gloss control device 10 preferably includes an inlet nip width changing mechanism that changes the nip width of the nip inlet N1 by changing the pressure contact state of the roller 2a on the nip inlet N1 side with the pressure roller 3. .

FIG. 9 shows the configuration of the inlet nip width changing mechanism.
The entrance nip width changing mechanism includes an eccentric cam 7a disposed on the opposite side of the nip portion (nip portion entrance N1) with the pressure roller 3 of the roller 2a, and both ends of the roller between the roller 2a and the eccentric cam 7a. 2a, and a spring member 8a that is a spring connected to (or in contact with) the eccentric cam 7a. The spring member 8a is arranged so that an elastic force acts so as to push the roller shaft of the roller 2a toward the nip portion entrance N1 side. Further, the roller 2a has the elastic force of the spring member 8a acting on the roller shaft so that the roller 2a is directed toward the nip inlet N1 (downward in FIG. 9) or away from the nip inlet N1 (upward in FIG. 9). ) Is arranged to be movable.

  Here, when the pressure roller 3 presses the roller 2a to form the nip portion N, for example, the roller 2a is first moved to the standard position (the eccentric position of the eccentric cam 7a is higher in the contact / separation direction with respect to the nip portion inlet N1). After the nip portion N (that is, the nip portion inlet N1) is formed, the nip width of the nip portion inlet N1 is changed by the inlet nip width changing mechanism. Become so.

FIG. 9A shows a case where the nip width of the nip portion entrance N1 is narrowed by the entrance nip width changing mechanism.
When the nip portion entrance N1 is first formed, the eccentric cam 7a rotates so that the contact portion with the spring member 8a becomes the bottom dead center, and thereby the pressing force of the roller 2a by the spring member 8a is weakened. The roller 2a moves slightly away from the nip entrance N1 (upward in the figure), and the nip width of the nip entrance N1 becomes narrower.
This state is suitable when a recording medium having a small heat capacity such as thin paper is more likely to be wrinkled.

FIG. 9B shows a case where the nip width of the nip portion inlet N1 is widened by the inlet nip width changing mechanism.
When the nip portion entrance N1 is first formed, the eccentric cam 7a rotates so that the contact portion with the spring member 8a becomes the top dead center, and thereby the pressing force of the roller 2a by the spring member 8a is increased. The roller 2a moves in a direction toward the nip portion entrance N1 (downward in the figure), and the nip width of the nip portion entrance N1 is increased.
This state is suitable when a recording medium having a large heat capacity such as cardboard is passed through or when it is better to apply heat to the recording medium as much as possible.

Next, the configuration of the fixing device according to the present invention will be described.
FIG. 10 is a cross-sectional view showing the configuration of the fixing device according to the present invention.
The fixing device 100 has a configuration in which a fixing mechanism unit 20 that performs a fixing process as a first process and an image gloss control device 10 that performs an image gloss control process as a second process are arranged in that order in the conveyance direction of the recording medium. It has become.

Here, the fixing mechanism unit 20 presses the fixing belt 21 spanned between the fixing roller 22a and the heating roller 22b with a constant tension, and presses the fixing belt 21 so as to be freely rotatable downward to form a fixing nip portion. And a pressure roller 23.
The image gloss control device 10 is configured as described above.

  During the fixing process of the fixing mechanism 20, the surface of the fixing belt 21 is heated to a predetermined temperature by the heater 22h while the fixing belt 21 and the pressure roller 23 are rotationally driven. The recording medium on which the toner is formed is passed (paper passing from the right side to the left side in FIG. 10), and fixing is performed by thermally fusing unfixed toner onto the recording medium by pressurization and heating in the fixing nip portion. . Next, the recording medium on which the image is fixed is discharged from the fixing nip portion and conveyed to the image gloss control device 10.

  In the image gloss control device 10, when a recording medium on which an image is fixed is carried in from the fixing mechanism unit 20, first, the image on the recording medium is pressed against the smooth surface of the endless belt 1 at the nip portion entrance N <b> 1 and smoothed. Then, the image smoothed at the intermediate nip portion N2 is conveyed while being cooled in close contact with the endless belt 1, and the recording medium is peeled off from the endless belt 1 at the nip portion exit N3. 10 is discharged. At this time, the recording medium is cooled to a predetermined temperature (peeling temperature), and the gloss reduction of the smoothed image can be prevented. Further, if necessary, the gloss of the image is adjusted by adjusting the nip width of the intermediate nip portion N2.

Next, the configuration of the image forming apparatus according to the present invention will be described.
FIG. 11 shows the configuration of a tandem type color copier which is an embodiment of the image forming apparatus according to the present invention.
An image forming apparatus (color copying machine) 200 according to the present invention includes an image forming unit 200A positioned at the center of the apparatus main body, a paper feeding unit 200B positioned below the image forming unit 200A, and an upper side of the image forming unit 200A. The image forming unit is a high-speed machine having an image reading unit (not shown), and the fixing device 100 of the present invention is incorporated in the image forming unit 200A.

  The image forming unit 200A is provided with a transfer belt 210 having a transfer surface extending in the horizontal direction, and a configuration for forming an image of a color complementary to the color separation color on the upper surface of the transfer belt 210. Is provided. That is, photoconductors 205Y, 205M, 205C, and 205K as image carriers that can carry images of toners of complementary colors (yellow, magenta, cyan, and black) are juxtaposed along the transfer surface of the transfer belt 210. ing.

  Each of the photoconductors 205Y, 205M, 205C, and 205K is configured by a drum that can rotate in the same direction (counterclockwise direction). An apparatus, a developing device, a primary transfer device, and a cleaning device are arranged (all not shown). In addition, each color toner is accommodated in each developing device.

  The transfer belt 210 is configured to be able to move in the same direction at a position facing the photoconductors 205Y, 205M, 205C, and 205K by being wound around a driving roller and a driven roller. Further, a transfer roller 212 is provided at a position facing a roller 211 that is one of the driven rollers. Further, the conveyance path of the recording medium P from the transfer roller 212 to the fixing device 100 is a horizontal path.

  The paper feed unit 200B separates the paper feed tray 220 on which the recording medium P as a recording medium is stacked and the recording medium P in the paper feed tray 220 from the top one by one in order from the transfer roller 212. It has a transport mechanism that transports it to a position.

  In image formation in the image forming apparatus 200 of the present invention, the surface of the photoreceptor 205Y is uniformly charged by the charging device, and an electrostatic latent image is formed on the photoreceptor 205Y based on image information from the image reading unit. The The electrostatic latent image is visualized as a toner image by a developing device containing yellow toner, and the toner image is primarily transferred onto the transfer belt 210 by a primary transfer device to which a predetermined bias is applied. . The other photoconductors 205M, 205C, and 205K also form similar images only with different toner colors, and the toner images of the respective colors are sequentially transferred onto the transfer belt 210 by the electrostatic force and superimposed.

Next, the toner image primarily transferred onto the transfer belt 210 from the photoconductors 205Y, 205M, 205C, and 205K is transferred to the recording medium P conveyed by the roller 211 and the transfer roller 212. The recording medium P onto which the toner image T has been transferred is further conveyed to the fixing device 100, and is first fixed at the fixing nip portion between the fixing belt 21 and the pressure roller 23 in the fixing mechanism portion 20. Next, the image gloss control device 10 adjusts the gloss of the image on the recording medium P.
Next, the recording medium P discharged from the fixing device 100 is sent out to the stacker along the discharge path.

  As described above, in the present invention, an image controlled to a desired gloss can be formed by the image forming apparatus having the fixing device 100.

  In the image gloss control device 10, the heat source 2 h is provided in the roller 2 a that forms the nip with the pressure roller 3 at the nip portion entrance N <b> 1 through which the recording medium enters, so that the recording medium conveyance speed is provided for each image forming apparatus. Even if they are different, the gloss control device 10 (or the fixing device 100) of the present invention can be applied to any image forming apparatus.

  For example, when the roller 2a is not provided with the heat source 2h, the temperature when the recording medium passes through the fixing mechanism unit 20 and enters the image gloss control device 10 depends on the set temperature of the fixing mechanism unit 20 and the conveyance speed. It becomes a value. Therefore, in an image forming apparatus having a high conveyance speed (for example, a conveyance speed of 250 mm / sec or more), the time required to enter the image gloss control apparatus 10 after passing through the fixing mechanism unit 20 is short. It is possible to maintain a high temperature (100 ° C. to 130 ° C.) at which the toner does not aggregate as the recording medium temperature when entering the printer, but in an image forming apparatus with a low conveyance speed, the temperature of the recording medium itself during conveyance Therefore, the toner enters the image gloss control device 10 in a state where toner aggregation has already occurred, and it is difficult to perform appropriate gloss imparting. When the roller 2a does not have the heat source 2h, the fixing mechanism unit 20 and the image gloss control device 10 must be brought close to each other to reduce the distance between the devices as much as possible. However, there is a limit due to restrictions on the size of the device.

  On the other hand, when the roller 2a is provided with the heat source 2h as in the present invention, even if the recording medium enters the image gloss control device 10 with the temperature lowered, the roller 2a is endless as a heating roller by the heat source 2h. Since the belt 1 is heated to a predetermined temperature (a high temperature (100 ° C. to 130 ° C. at which the toner does not aggregate)), appropriate gloss can be imparted, and it can be applied to an image forming apparatus of any conveyance speed. be able to.

  Although the present invention has been described with the embodiments shown in the drawings, the present invention is not limited to the embodiments shown in the drawings, and other embodiments, additions, modifications, deletions, etc. Can be changed within the range that can be conceived, and any embodiment is included in the scope of the present invention as long as the effects and advantages of the present invention are exhibited.

  For example, in FIGS. 10 and 11, the fixing mechanism 100 and the image gloss control device 10 are arranged side by side in the horizontal direction and the horizontal conveyance fixing device 100 that passes the recording medium in the horizontal direction is shown. Thus, the fixing mechanism unit 20 and the image gloss control device 10 may be arranged side by side in the vertical direction so as to be a vertical conveyance fixing device that passes the recording medium in the vertical direction.

1 Endless belt 2a, 2b, 2c Roller (belt stretch member)
2bj, 2cj, 3j Roller groove 2h Heat source 3 Pressure roller 3h Induction heating device 4a, 4b Cooling device 5a, 5b, 6a, 6b Non-contact thermistor 7a, 7b, 7c Eccentric cam 8a, 8b, 8c Spring member 9b, 9c Groove DESCRIPTION OF SYMBOLS 10 Image gloss control apparatus 11 Non-contact thermistor holding bracket 11a, 11a 'Rotation center 11b, 11b' Arm part 11 'Separating member holding bracket 20 Fixing mechanism part 21 Fixing belt 22a Fixing roller 22b Heating roller 22h Heater 23 Pressure roller 100 Fixing Device 200 Image forming device (color copier)
200A Image forming unit 200B Paper feeding unit 205Y, 205M, 205C, 205K Photoconductor 210 Transfer belt 211 Roller 212 Transfer roller 220 Paper feed tray N Nip part N1 Nip part inlet N2 Intermediate nip part N3 Nip part outlet P Recording medium

JP 2004-325934 A JP 2009-014823 A

Claims (10)

An endless belt spanned across a plurality of tension members;
A pressure member that forms a nip portion through which the recording medium on which the toner image is fixed is brought into pressure contact with at least two tension members among the plurality of tension members via the endless belt;
Temperature detecting means for detecting the surface temperature of the endless belt;
Belt heating means for heating the endless belt based on the detection result of the temperature detection means at the nip portion inlet or upstream of the nip portion;
At least one of the endless belt and the pressure member is cooled in an intermediate nip region where the endless belt and the pressure member are in close contact with each other between the two stretching members forming the nip portion. Cooling means to
An image gloss control device comprising:   2. The image gloss control device according to claim 1, wherein a mean square roughness Rq of the surface of the endless belt is 0.3 [mu] m or less.   2. The image gloss control device according to claim 1, wherein a mean square roughness Rq of the surface of the pressure member is 0.3 [mu] m or less.   The image gloss control device according to claim 1, further comprising a pressure member heating unit configured to heat the pressure member at the nip portion inlet or upstream of the nip portion.   The intermediate nip width changing mechanism for changing the nip width of the intermediate nip region by moving the stretching member on the nip portion outlet side in the outer peripheral direction of the pressure member. An image gloss control device according to claim 1.   The temperature detecting means is a non-contact type thermometer disposed at the nip portion outlet, and the intermediate nip width changing mechanism is configured to make the distance between the nip portion outlet portion and the endless belt constant. 6. The image gloss control device according to claim 5, wherein the image gloss control device moves in conjunction with a change in the nip width of the intermediate nip region.   A separation member that moves in conjunction with a change in the nip width of the intermediate nip region by the intermediate nip width changing mechanism is provided so that the distance between the end portion of the nip portion and the endless belt is constant. Item 7. The image gloss control device according to Item 5 or 6.   8. The inlet nip width changing mechanism for changing the nip width of the nip portion inlet by changing the pressure contact state of the tension member on the nip portion inlet side with the pressure member. An image gloss control device according to claim 1.   A fixing device comprising the image gloss control device according to claim 1.   An image forming apparatus comprising the fixing device according to claim 9.