JP6816484B2 - Fixing device and image forming device - Google Patents

Description

The present invention relates to an image forming apparatus including a fixing device and a fixing device.

In recent years, there has been an increasing market demand for energy saving and high speed for image forming devices such as copiers, printers, facsimiles, or multifunction devices having at least two functions thereof.

Among the image forming devices, the fixing device consumes a large amount of power and has a lot of room for energy saving. Therefore, various proposals have been made. For example, in Patent Document 1, the fixing device has a low heat capacity, a thin film shape, and flexibility. A nip forming unit is fixedly arranged inside the endless belt (inside the loop), and a fixing nip is formed between the belt and the pressurized rotating body by the contact pressure between the nip forming unit and the pressurized rotating body. Fixing devices are known.

In a fixing device having such a configuration, in order to prevent excessive temperature rise at the end of the belt when passing small size paper while supporting recording materials of various sizes, the width direction of the belt (paper width direction). ), A plurality of halogen heaters (radiant heat sources) having different light distributions are provided inside the belt, and heat is transferred to the surface of the nip forming member constituting the nip forming unit facing the belt in the longitudinal direction of the belt. It is disclosed in Patent Document 2 that it is covered with a heat transfer assisting member.

In the fixing device having the above configuration equipped with a thin-walled endless belt, the fixing belt is directly heated by a radiant heat source such as a halogen heater. Therefore, when the fixing belt is heated unnecessarily, the portion of the fixing belt facing the heater is directly heated by the heater. It is heated and the temperature rises rapidly. On the other hand, the temperature of the portion of the fixing belt that does not face the heater remains relatively low because it is not directly heated by the heater. When the thin belt is partially or locally heated in this way, a temperature difference may occur in the circumferential direction or the longitudinal direction of the fixing belt. Such a temperature difference becomes "temperature spots" in the circumferential direction of the fixing belt, and when a temperature spot having a large temperature difference occurs, the fixing belt is fixed by local thermal expansion (difference in the amount of expansion from other parts). The surface of the belt may be distorted. Further, if the strain exceeds the yield stress of the fixing belt, buckling fracture (kink) may occur in the fixing belt. In particular, in a film-shaped fixing belt, the temperature rises rapidly, so even if the heating is controlled according to the detection of the belt temperature, the actual belt temperature may rise more than necessary. Then, when the surface of the fixing belt is distorted, there is a problem that a good fixing nip is not formed and an image with deteriorated quality is formed.

Further, in the fixing device having the above configuration, the belt is sandwiched between the pressurized rotating body and the nip forming unit by the fixing nip and rotates, and the belt is guided by the flanges arranged at both ends to run except for the fixing nip. Therefore, ensuring stable running performance of the belt is also a problem. In particular, if the diameter of the belt is reduced in order to reduce the size of the fixing device, the durability of the belt may be lowered by rubbing against the inner circumference of the belt at the circumferential inlet and outlet of the nip forming unit during rotation. Then, when the fixing belt is rotated in a low temperature state, the rubbing resistance at the fixing nip becomes large, and the fluctuation of the trajectory of the traveling belt becomes large.

An object of the present invention is to provide a fixing device in which temperature spots and buckling fracture do not occur in the fixing belt and the fixing belt and the nip forming unit do not rub against each other.

The subject is a flexible endless belt, a pressure member provided on the outside of the belt and facing the belt, and a pressure member provided on the inside of the belt and the belt and the pressure member. It has a nip forming unit that forms a fixing nip between them, a heat source that heats the belt, and a temperature detection unit that detects the temperature of the belt, and the temperature detected by the temperature detection unit is the first predetermined temperature. When the heat source generates heat under lighting conditions that do not reach the above temperature and the detected temperature reaches the second predetermined temperature, the belt starts to rotate, and the nip forming unit forms the nip forming member and the nip. The member has a heat transfer assisting member arranged so as to cover the surface of the member facing the inner peripheral surface of the belt, and further, the longitudinal direction of the surface of the nip forming member facing the heat transfer assisting member. A plurality of contact heat transfer type heat sources provided at both ends and heating the end portions in the width direction of the belt are provided, and the lighting conditions of the plurality of contact heat transfer type heat sources are lighting of the heat source which is a radiation type heat source. The contact heat transfer type heat source is also lit so as to reach the second predetermined temperature at the timing when the second predetermined temperature of the belt is reached by the radiation type heat source, which is determined by the temperature of the belt at the start of control. that are controlled conditions, it is solved by a fixing device.

In the present invention, the heat source is heated with the first predetermined temperature as the target temperature, which does not cause a temperature difference in the circumferential direction and the longitudinal direction of the belt so as to cause temperature spots and kinks, and the belt reaches the second predetermined temperature. Since the belt rotation starts when the temperature is reached, the belt and the nip forming unit do not rub against each other.

It is a schematic cross-sectional block diagram which shows one Embodiment of a fixing device. It is a perspective view which shows the basic structure of the nip formation unit. It is a figure which shows schematic layout of a laser displacement meter when measuring a belt locus during rotation. It is a figure which shows the belt locus obtained from the measurement result. It is an enlarged view near the fixing nip. It is a graph which shows the relationship between the belt temperature of a fixing belt and the belt displacement amount. It is a flowchart which shows the heating control of a fixing belt. It is a graph which showed an example of the relationship between the lighting rate of a heater, the lighting time, and the fixing belt temperature. It is a graph which shows an example of the temperature rise characteristic by the applied voltage of a ceramic heater. FIG. 10a is a graph showing an example of a temperature rise profile when the temperature rise of the end heater is changed according to the temperature of the fixing belt at the start of operation of the fixing device. FIG. 10a shows a case where the fixing device starts operation from a cold state. FIG. 10b shows a case where the operation is started from a state where the temperature is higher than when it is cold. It is a graph which shows that the displacement amount of a belt track also increases relatively when the belt line speed is fast. It is a schematic diagram which shows the image forming apparatus which concerns on one Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a schematic cross-sectional configuration diagram showing a fixing device 20 according to an embodiment of the present invention. The fixing device 20 has an endless fixing belt 21 which is a thin and flexible tubular fixing member, and a pressure roller 22 which is a pressure member which abuts from the outer peripheral side of the fixing belt 21. ing. The fixing belt 21 is heated by the radiant heat of the halogen heaters 23A and 23B (hereinafter, also referred to as the first halogen heater 23A and the second halogen heater 23B) as a plurality of fixing heat sources arranged inside (inside the loop). The halogen heater represents a radiant heat source as a fixing heat source which is a main heat source.

Further, inside the fixing belt 21, a nip forming member 24 that forms a fixing nip N with a pressure roller 22 via the fixing belt 21 and a stay member 25 (supporting member) that supports the nip forming member 24 are arranged. Has been done. The nip forming member 24 arranged in the width direction of the fixing belt 21 is fixedly supported by the stay member 25 to prevent the nip forming member 24 from bending due to the pressure from the pressure roller 22. A uniform nip width can be obtained over the axial direction (longitudinal direction) of the pressure roller 22. The nip forming member 24 is a heat-resistant member having high mechanical strength and a heat-resistant temperature of 200 ° C. or higher, particularly a heat-resistant resin such as a polyimide (PI) resin or a polyetheretherketone (PEEK) resin, which is reinforced with glass fiber. It is composed of the plastic. As a result, deformation of the nip forming member 24 due to heat is prevented in the toner fixing temperature range, a stable fixing nip state is ensured, and output image quality is stabilized. Further, the stay member 25 and the halogen heaters 23A and 23B are fixedly held at both ends in the longitudinal direction by a side plate of the fixing device 20 or a holder provided separately.

A heat transfer assisting member 27, which is also called a heat equalizing member that facilitates heat transfer in the longitudinal direction of the fixing belt, is arranged so as to cover the surface of the nip forming member 24 facing the inner peripheral surface of the fixing belt 21. This prevents heat from staying in the end region of the fixing belt 21 when passing small-sized paper, and actively transfers heat in the width direction of the fixing belt 21, that is, in the longitudinal direction of the heat transfer assisting member 27. This eliminates the temperature non-uniformity in the longitudinal direction. Therefore, the heat transfer assisting member 27 is made of a material having high thermal conductivity, such as copper (398 W / mk) or aluminum (236 W / mk), which enables heat transfer in a short time. In the description of FIG. 2, the surface of the heat transfer assisting member 27 facing the inner peripheral surface of the fixing belt 21 is a surface that directly contacts the fixing belt 21, is a nip forming surface, and is formed flat. However, it may have a concave shape or other shape. With the concave nip-forming surface, the discharge direction of the tip of the paper, which is the recording material, is closer to the pressure roller, the separability is improved, and the occurrence of jam is suppressed. Here, the recording material includes, in addition to plain paper, thick paper, postcards, envelopes, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, OHP sheets, and the like.

Temperature sensors 29A and 29B, which are temperature detection units for detecting the belt temperature, are provided at appropriate positions on the outer peripheral side of the fixing belt 21, for example, positions facing the halogen heaters 23A and 23B, and the paper of the fixing device 20 is provided. A separation member 41 that separates the paper P from the fixing belt 21 is arranged on the downstream side in the transport direction. Further, as is well known, a releaseable pressurizing means for pressurizing the pressurizing roller 22 onto the fixing belt 21 is provided.

In order to reduce the heat capacity, the endless fixing belt 21 which is thin and has a small diameter like a film has an inner peripheral side base material made of a metal material such as nickel or SUS or a resin material such as polyimide, and PFA. It is composed of a release layer on the outer peripheral side formed of (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer), PTFE (polytetrafluoroethylene), or the like. An elastic layer made of a rubber material such as silicone rubber, foamable silicone rubber, or fluororubber may be interposed between the base material and the release layer. If the thickness of the elastic layer is set to about 100 μm, minute irregularities on the belt surface can be absorbed due to the elastic deformation of the elastic layer when the unfixed toner is crushed and fixed, and the occurrence of uneven gloss can be avoided. From the viewpoint of reducing the heat capacity, the fixing belt 21 is set to have a thickness of 1 mm or less and a diameter of 20 to 40 mm as a whole. The thicknesses of the base material, the elastic layer, and the release layer constituting the fixing belt 21 are set in the ranges of 20 to 50 μm, 100 to 300 μm, and 10 to 50 μm, respectively. In order to further reduce the heat capacity, it is desirable that the thickness of the entire fixing belt 21 is 0.2 mm or less, and more preferably 0.16 mm or less, and the diameter is 30 mm. It is desirable to do the following.

The stay member 25 having a T-shaped cross section has an upright portion 25a on the side opposite to the fixing nip N side, and halogen heaters 23A and 23B as main heat sources are arranged so as to be separated by the upright portion 25a. One of the halogen heaters 23A and 23B has heat generating portions in the central portion in the longitudinal direction corresponding to the small size paper, and the other has heat generating portions in both ends in the longitudinal direction corresponding to the large size paper. By arranging the two halogen heaters 23A and 23B separated from each other by the stay member 25 having a T-shaped cross section, the problem of mutual heating of the heaters can be avoided as compared with the conventional fixing device in which a plurality of halogen heaters are arranged side by side. , The heating efficiency can be increased. The halogen heaters 23A and 23B are configured to generate heat by controlling the output by a power supply unit provided in the printer main body of the image forming apparatus described later, and the output control is the temperature provided on the outer periphery of the fixing belt 21. This is performed based on the temperature detection result of the belt surface by the sensors 29A and 29B. By controlling the output of such a heater, the temperature of the fixing belt 21 (fixing temperature) can be set to a desired temperature.

Further, reflective members 28A and 28B are arranged between the stay member 25 and the halogen heaters 23A and 23B. As a result, the heating efficiency of the halogen heaters 23A and 23B for the fixing belt 21 can be increased, and wasteful energy consumption due to the stay member 25 being heated by the radiant heat from the halogen heaters 23A and 23B can be suppressed. The same effect can be obtained by performing heat insulation or mirror surface treatment on the surface of the stay member 25 instead of providing the reflective members 28A and 28B.

The pressure roller 22 is composed of a core metal, an elastic layer made of foamable silicone rubber or fluororubber provided on the surface of the core metal, and a release layer made of PFA or PTFE provided on the surface of the elastic layer. It is configured. At a position where the pressure roller 22 is pressed against the fixing belt 21 by a pressure means such as a spring and is in pressure contact with the fixing belt 21, the elastic layer of the pressure roller 22 is crushed to form a fixing nip N having a predetermined width. Ru. The pressurizing roller 22 is rotationally driven by a drive source such as a motor provided in the printer body. When the pressurizing roller 22 is rotationally driven, the driving force is transmitted to the fixing belt 21 by the fixing nip N, and the fixing belt 21 is driven to rotate. The fixing belt 21 is sandwiched between the fixing nip N and rotates, and is guided by the side plate flanges arranged at both ends and travels except for the fixing nip N.

In the present embodiment, the pressure roller 22 is a solid roller, but it may be a hollow roller. In that case, a heat source such as a halogen heater may be arranged inside the pressurizing roller 22. The elastic layer may be solid rubber, but if there is no heat source inside the pressure roller, sponge rubber may be used. Sponge rubber is more preferable because it has higher heat insulating properties and is less likely to take away heat from the fixing belt 21.

FIG. 2 is a perspective view showing a basic configuration of the nip forming unit. As shown in FIG. 2, the nip forming unit is composed of a nip forming member 24, a stay member 25, and a heat transfer assisting member 27. In the nip forming unit, the surface of the nip forming member 24 opposite to the fixing nip N side is integrated with the plane of the stay member 25 on the fixing nip N side. At this time, uneven shapes such as bosses and pins may be formed on each surface, and these may be fitted in a shape-constrained manner. The heat transfer assisting member 27 is fitted and integrated so as to cover the surface of the substantially rectangular parallelepiped nip forming member 24 facing the inner peripheral surface of the fixing belt 21. The heat transfer assisting member 27 and the nip forming member 24 may be integrally formed by providing claws or the like to engage with each other, but adhesive or the like may be used.

Recesses 24a and 24b as stepped portions are formed at both ends of the nip forming member 24 in the longitudinal direction, and end heaters 26a as end heat sources different from the main heat source (fixing heat source) are formed at these portions. , 26b are housed, mounted integrally, and used to heat both ends of a novi size paper width larger than the maximum standard size. As the end heater, a contact heat transfer type heat source which is a resistance heating element such as a ceramic heater is generally used.

The surface of the heat transfer assisting member 27 facing the inner peripheral surface of the fixing belt 21 is configured as the belt sliding contact surface 27a, but in terms of mechanical strength, the nip forming member 24 is substantially the nip forming surface. 24c of the surface facing the pressure roller 22.

As described above, in the present embodiment, the end heaters 26a and 26b are integrally provided with the nip forming member 24 necessary for forming the fixing nip, so that the end heaters 26a and 26b are provided on the fixing belt 21. It can be placed inside in a space-saving manner. Further, the surfaces of the end heaters 26a and 26b facing the inner surface of the fixing belt 21 are configured to be located at the same height (on the same plane) as the surfaces of the nip forming member 24 facing the fixing belt 21. , Sufficient pressing force by the pressurizing roller 22 can be applied via the heat transfer assisting member 27. As a result, the fixing belt 21 is in a state of being indirectly in close contact with the end heaters 26a and 26b, and stable belt running is possible. Further, the fixing belt 21 and the end heaters 26a and 26b are in contact with each other with a sufficient contact pressure, and good heating is maintained.

By the way, in the fixing device 20 of the present embodiment, as described above, the fixing belt 21 is sandwiched between the fixing nip N and rotates, and other than the fixing nip N, the fixing belt 21 is guided by the side plate flanges arranged at both ends and travels. It was confirmed that when the temperature of the fixing belt 21 changed, the traveling track of the belt changed. FIG. 3 schematically shows the layout of the measuring instrument when measuring the belt locus during rotation. As a measuring instrument, a high-speed, high-precision laser displacement meter L-KG3000 manufactured by KEYENCE was used to measure the amount of displacement of the outer circumference of the belt with respect to the temperature of the fixing belt. FIG. 4 shows the belt locus obtained from the measurement result by the laser displacement meter. In the figure, 21a (solid line) is a belt locus when the paper is passed at the target control temperature, 21b is a belt locus when the belt temperature is low, and 21c is a belt locus when the belt temperature is high. It was found that even if the belt temperature changed, there was no large displacement near the exit of the fixing nip N, and the displacement amount near the entrance of the fixing nip N was absorbed as the fixing nip N proceeded.

FIG. 5 is an enlarged view of the vicinity of the fixing nip N. In the belt locus 21a when the paper is passed at the target fixing temperature, the inner circumference of the fixing belt and the nip forming unit (heat transfer assisting member 27 in the figure) are not rubbed except for the nip width. However, in the belt locus 21b when the belt temperature is low, the rigidity of the belt itself becomes high due to the low belt temperature and tends to be close to a perfect circle. Therefore, as can be seen from FIG. 5, the inlet side of the fixing nip N Then, the inner circumference of the belt may rub against the nip forming unit.

FIG. 6 shows the relationship between the belt temperature of the fixing belt and the amount of belt displacement. Here, as can be seen from FIG. 5, the "+ (plus)" side of the displacement amount is the displacement toward the heat transfer assisting member 27 side (belt inner circumference side), and the "-(minus)" side is the belt outer circumference side. Is the displacement to. It can be seen that in the temperature range of the fixing belt practical for the fixing process, the displacement is almost linear, and the displacement is about 0.3 mm per 50 deg.

A lubricant such as fluorine grease is interposed between the surface of the heat transfer assisting member 27 and the inner peripheral surface of the fixing belt 21 to improve slidability, but lubrication is provided in areas other than the fixing nip N such as the nip inlet. Since it does not have a mechanism for positively holding the agent, when the fixing belt 21 rotates in a low temperature state, it comes into contact with the heat transfer assisting member 27 and causes wear, which shortens the life of the fixing device. ing. Therefore, in order to avoid such a situation, the heating and rotation of the fixing belt 21 are controlled. If the inner circumference of the fixing belt 21 and the heat transfer assisting member 27 do not come into contact with each other at a portion other than the fixing nip N, the life of the fixing device can be extended.

First, in the configuration of the fixing device according to the present embodiment, the fixing belt 21 is directly heated by the halogen heaters 23A and 23B which are radiant heat sources. Therefore, when the fixing belt 21 is heated unnecessarily, the fixing belt 21 faces the halogen heaters 23A and 23B. The surface (inner peripheral surface) is partially heated to a very high temperature by the heater. As a result, a temperature difference is generated in the circumferential direction and the longitudinal direction (width direction) of the fixing belt 21, and such a temperature difference causes "temperature spots" in the circumferential direction of the fixing belt, and the temperature spots are large when the temperature difference is large. If this occurs, the surface of the fixing belt may be distorted due to the difference in the local thermal expansion amount of the fixing belt. Further, if the strain exceeds the yield stress of the fixing belt, buckling fracture (kink) may occur in the fixing belt. When the surface of the fixing belt is distorted, a good fixing nip is not formed, and an image with deteriorated quality is formed.

In the present embodiment, the halogen heaters 23A and 23B are lit at a low lighting rate, and "a temperature that does not cause a temperature difference in the circumferential direction or the longitudinal direction of the fixing belt 21 so as to cause temperature unevenness or kink" ("first predetermined" By raising the temperature while controlling it below (called "temperature"), it is possible to avoid the occurrence of temperature spots and buckling fracture (kinks).

In FIG. 7, under a lighting condition in which the fixing belt does not reach the first predetermined temperature, the halogen heaters 23A (small size paper) or the halogen heaters 23A and 23B (large size paper) are heated and fixed at a low lighting rate. The belt 21 is heated (step 1). While the fixing belt 21 is being heated until it approaches the first predetermined temperature, "the inner circumference of the fixing belt 21 and the heat transfer assisting member 27 do not come into contact with each other except for the fixing nip N (the rigidity of the belt is increased). (Becomes less than or equal to the predetermined temperature) ”(the second predetermined temperature <the first predetermined temperature), so whether or not the temperature detected by the temperature sensors 29A and 29B is higher than the second predetermined temperature is determined. After making a judgment (step 2) and the fixing belt 21 reaches the second predetermined temperature, the fixing belt 21 is rotated at a predetermined rotation speed (step 3). After the rotation of the fixing belt 21 starts, the fixing belt 21 is heated at a higher lighting rate (predetermined lighting rate) (step 4). When the fixing belt 21 reaches the first predetermined temperature, the image drawing preparation is completed or the warm-up operation is completed.

FIG. 8 is a graph showing an example of the relationship between the lighting rate of the heater, the lighting time, and the fixing belt temperature. When the light is turned on at a lighting rate of 10% every 50 [msec], a gentle temperature rise curve (solid line) is shown, and control can be performed so that temperature spots do not occur. On the other hand, when the lighting rate is set to 30%, a sharp temperature rise curve (dotted line) is formed, temperature control becomes difficult, and temperature spots and buckling fracture (kink) may occur. Therefore, in the temperature rise control at the stage of "heating at a low lighting rate" in the flow of FIG. 7, a method of repeating a very low lighting rate in a short time is effective.

As described above, the more uniform the temperature of the entire fixing belt 21, the less likely it is that temperature spots and buckling fractures (kinks) occur. Therefore, when passing large-sized paper, the halogen heaters 23A and 23B are lowered, respectively. When lighting at the lighting rate, the belt temperature is detected by the corresponding temperature sensors 29A and 29B, and the lighting rate of each halogen heater 23A and 23B is individually controlled, so that the temperature of the entire fixing belt 21 is uniform. It is desirable to raise the temperature to a second predetermined temperature in the state. However, even in this case, it is necessary to control the temperature below the first predetermined temperature that does not cause temperature unevenness or buckling fracture (kink).

Further, in the present embodiment, end heaters 26a and 26b, which are contact heat transfer type heat sources, are provided to heat both ends of a novi size paper width larger than the maximum standard size. The ceramic heater, which is a contact heat transfer type heat source, has a temperature rising characteristic that is substantially linear with respect to the applied voltage, and hardly causes an overshoot unlike a halogen heater. FIG. 9 shows the temperature rising characteristics of the ceramic heater when 100 [V], 80 [V], and 60 [V] are applied, respectively. It can be seen that the calorific value is proportional to the square of the applied voltage. In order to slowly raise the temperature of the fixing belt by the halogen heaters 23A and 23B, it is necessary to repeat a low lighting rate in a short time as shown in FIG. 8, but the end heaters 26a and 26b, which are ceramic heaters, are at the applied voltage. The rate of temperature rise can be controlled.

Therefore, by determining the voltage applied to the end heaters 26a and 26b, the end heaters 26a and 26b can reach the second predetermined temperature at the timing when the fixing belt 21 reaches the second predetermined temperature. It will be possible. Therefore, when fixing the novi size paper, it is difficult to heat the halogen heaters 23A and 23B by simultaneously lighting the end heaters 26a and 26b in addition to the halogen heaters 23A and 23B when the temperature is raised to the second predetermined temperature. The vicinity of the fixing nip N of the fixing belt 21, particularly the end of the belt can also be heated, and the temperature can be controlled to be uniform over the entire circumference of the fixing belt 21. However, even in this case, it is necessary to control the temperature below the first predetermined temperature that does not cause temperature unevenness or buckling fracture (kink).

Due to the linear temperature rise characteristic of the ceramic heater with respect to the applied voltage, the optimum application to the end heaters 26a and 26b is based on the result of detecting the belt temperature by the temperature sensors 29A and 29B at the start of lighting of the halogen heaters 23A and 23B. The voltage can be estimated. FIG. 10a shows the temperature rise curve of the fixing belt when the fixing device starts operating from the cold state (hence, when the lighting control of the halogen heater starts), and FIG. 10b shows the temperature is higher than that when the fixing device is cold, such as after passing paper. The temperature rise curve when the fixing device starts operation from a high state is shown. When the temperature of the fixing belt 21 at the start of operation is equal to or lower than the second predetermined temperature, the end heaters 26a and 26b are also lit at the same time, so that it is difficult to heat the fixing belts 23A and 23B. The vicinity can also be heated. Here, by determining the voltage applied to the end heaters 26a and 26b according to the belt temperature at the start of operation, the determined voltage is the detection temperature of the temperature sensors 29A and 29B facing the halogen heaters 23A and 23B. By applying the voltage to the end heaters 26a and 26b until the temperature rises to the second predetermined temperature, the entire circumference and width of the fixing belt 21 can be uniformly raised to the second predetermined temperature.

As described above, the belt trajectory fluctuates depending on the temperature of the fixing belt 21, but when measuring the rotating belt trajectory with the layout of the laser displacement meter shown in FIG. 3, if the belt rotation line speed is high, the belt trajectory It was also clarified that the amount of displacement also increased relatively (Fig. 11). Therefore, in order to reduce the amount of fluctuation in the belt trajectory of the fixing belt 21, the belt linear velocity is set low after reaching the second predetermined temperature until the reload temperature (predetermined temperature at which fixing is possible) is reached. That is also effective.

In the present embodiment, the temperature of the fixing belt is detected by a plurality of temperature sensors, but if there is a difference in the detected temperatures by both sensors, the halogen corresponding to the belt portion that has reached the second predetermined temperature first. By further lowering or turning off the lighting rate of the voltage applied to the heater, the temperature of the belt portion is kept near the second predetermined temperature, and the belt portion corresponding to the other halogen heater reaches the second predetermined temperature. Wait to do. Then, when the detection temperature of each temperature sensor reaches the second predetermined temperature, the rotation of the fixing belt is started. At this time, the applied voltage of the end heater is controlled based on the higher detection temperature when the image forming apparatus issues a command to start image formation.

Finally, the image forming apparatus according to the embodiment of the present invention will be described. FIG. 12 is a schematic view showing an image forming apparatus according to an embodiment of the present invention, which is equipped with the above-mentioned fixing device. The image forming apparatus 1 is a color laser printer, and four image forming portions 4Y, 4C, 4M, and 4K are juxtaposed in the center of the printer body along the extension direction of the intermediate transfer belt 30. There is. Each image forming unit 4Y, 4C, 4M, 4K accommodates developers of different colors of yellow (Y), cyan (C), magenta (M), and black (K) corresponding to the color separation components of the color image. Other than that, it has the same configuration.

Specifically, each image processing unit 4Y, 4C, 4M, 4K constituting the image station includes a drum-shaped photoconductor 5 as a latent image carrier, a charging device 6 for charging the surface of the photoconductor 5. A developing device 7 that supplies toner to the surface of the photoconductor 5 and a cleaning device 8 that cleans the surface of the photoconductor 5 are provided. In FIG. 12, only the photoconductor 5, the charging device 6, the developing device 7, and the cleaning device 8 included in the black image forming unit 4K are assigned color codes, and the other image forming units 4Y, 4C, and 4M have a color code. The code is omitted.

An exposure device 9 that exposes the surface of the photoconductor 5 is arranged below the image-creating portions 4Y, 4C, 4M, and 4K. The exposure device 9 includes a light source, a polygon mirror, an f−θ lens, a reflection mirror, and the like, and irradiates the surface of each photoconductor 5 with laser light based on image data.

A transfer device 3 is arranged above the image forming portions 4Y, 4C, 4M, and 4K. The transfer device 3 includes an intermediate transfer belt 30 as a transfer body, four primary transfer rollers 31 as primary transfer means, and a secondary transfer roller 36 as secondary transfer means. Further, the transfer device 3 includes a secondary transfer backup roller 32, a cleaning backup roller 33, a tension roller 34, and a belt cleaning device 35.

The intermediate transfer belt 30 is an endless belt, and is stretched by a secondary transfer backup roller 32, a cleaning backup roller 33, and a tension roller 34. Here, the secondary transfer backup roller 32 is rotationally driven so that the intermediate transfer belt 30 orbits (rotates) in the direction indicated by the arrow in the figure.

Each of the four primary transfer rollers 31 has an intermediate transfer belt 30 sandwiched between the four primary transfer rollers 31 and each of the photoconductors 5 to form a primary transfer nip. Further, a power supply of the printer main body is connected to each primary transfer roller 31, and a predetermined DC voltage (DC) and / or AC voltage (AC) is applied to each primary transfer roller 31. ..

The secondary transfer roller 36 sandwiches the intermediate transfer belt 30 with the secondary transfer backup roller 32 to form a secondary transfer nip. Further, similarly to the primary transfer roller 31, the power supply of the printer main body is also connected to the secondary transfer roller 36, and a predetermined DC voltage (DC) and / or AC voltage (AC) is applied to the secondary transfer roller 36. It is supposed to be done.

The belt cleaning device 35 has a cleaning brush and a cleaning blade arranged so as to come into contact with the intermediate transfer belt 30.

A bottle accommodating portion 2 is provided on the upper portion of the printer main body, and four toner bottles 2Y, 2C, 2M, and 2K accommodating replenishing toner are detachably attached to the bottle accommodating portion 2. As is well known, a replenishment path is provided between each toner bottle 2Y, 2C, 2M, 2K and each developing device 7, and each development is performed from each toner bottle 2Y, 2C, 2M, 2K via this replenishment path. Toner is replenished to the device 7.

On the other hand, at the lower part of the printer main body, a paper feed tray 10 containing the paper P as a recording material, a paper feed roller 11 for carrying out the paper P from the paper feed tray 10, and the like are provided. As is well known, a manual paper feed mechanism may be provided.

A transport path R for passing the paper P from the paper feed tray 10 through the secondary transfer nip and discharging the paper P to the outside of the apparatus is provided in the printer main body. In the transport path R, a pair of resist rollers 12 as transport means for transporting the paper P to the secondary transfer nip are arranged on the upstream side in the paper transport direction from the position of the secondary transfer roller 36.

Further, the fixing device 20 described in detail is arranged on the downstream side in the paper transport direction from the position of the secondary transfer roller 36, and the unfixed image transferred to the paper P is fixed. Further, a pair of paper ejection rollers 13 for ejecting the paper to the outside of the apparatus are provided on the downstream side of the transport path R in the paper transport direction with respect to the fixing device 20. Further, on the upper surface of the printer body, a paper ejection tray 14 for stocking the paper ejected outside the apparatus is provided.

The basic operation of the printer according to this embodiment is as follows. When the image-drawing operation is started, each of the photoconductors 5 in each image-forming unit 4Y, 4C, 4M, and 4K is rotationally driven clockwise in the figure, and the surface of each photoconductor 5 is brought to a predetermined polarity by the charging device 6. It is uniformly charged. The surface of each charged photoconductor 5 is irradiated with laser light from the exposure device 9, and an electrostatic latent image is formed on the surface of each photoconductor 5. At this time, the image information to be exposed to each photoconductor 5 is monochromatic image information obtained by decomposing a desired full-color image into yellow, cyan, magenta, and black color information. By supplying toner to the electrostatic latent image formed on each photoconductor 5 in this way by each developing device 7, the electrostatic latent image is visualized (visualized) as a toner image. ..

Further, when the image-drawing operation is started, the secondary transfer backup roller 32 is rotationally driven counterclockwise in the drawing to rotate the intermediate transfer belt 30 in the direction indicated by the arrow in the figure. Then, a constant voltage or a constant current controlled voltage having a polarity opposite to the charging polarity of the toner is applied to each primary transfer roller 31. As a result, a transfer electric field is formed at the primary transfer nip between each primary transfer roller 31 and each photoconductor 5.

After that, when the toner image of each color on the photoconductor 5 reaches the primary transfer nip with the rotation of each photoconductor 5, the toner image on each photoconductor 5 is generated by the transfer electric field formed in the primary transfer nip. The intermediate transfer belt 30 is sequentially superposed and transferred. Thus, a full-color toner image is supported on the surface of the intermediate transfer belt 30. Further, the toner on each photoconductor 5 that could not be completely transferred to the intermediate transfer belt 30 is removed by the cleaning device 8. The surface of each photoconductor 5 is then statically eliminated to initialize the surface potential.

At the lower part of the image forming apparatus, the paper feed roller 11 starts rotational driving, and the paper P is sent out from the paper feed tray 10 to the transport path R. The paper P sent out to the transport path R is timed by the resist roller 12 and sent to the secondary transfer nip between the secondary transfer roller 36 and the secondary transfer backup roller 32. At this time, a transfer voltage having a polarity opposite to the toner charging polarity of the toner image on the intermediate transfer belt 30 is applied to the secondary transfer roller 36, whereby a transfer electric field is formed in the secondary transfer nip.

After that, when the toner image on the intermediate transfer belt 30 reaches the secondary transfer nip as the intermediate transfer belt 30 goes around, the transfer electric field formed at the nip causes the toner image on the intermediate transfer belt 30. Is collectively transferred onto the paper P. Further, the residual toner on the intermediate transfer belt 30 that could not be transferred to the paper P at this time is removed by the belt cleaning device 35, and the removed toner is conveyed to the waste toner container placed in the printer main body. , Will be recovered.

After that, the paper P is conveyed to the fixing device 20, and the toner image on the paper P is fixed to the paper P by the fixing device 20. Then, the paper P is discharged to the outside of the device by the paper ejection roller 13 and is stocked on the paper ejection tray 14.

The above description is an image forming operation when forming a full-color image on paper, but a monochromatic image can be formed by using any one of four image forming units 4Y, 4C, 4M, and 4K. It is also possible to form a two-color or three-color image using two or three image-forming sections.

The present invention has been described above based on the embodiments. The present invention is not limited to the embodiments, and can be appropriately modified within the scope of the present invention. Further, the image forming apparatus provided with the fixing apparatus of the present invention is not limited to a copying machine or a printer, but may be a facsimile or a multifunction device having a plurality of functions.

1 Image forming device 2 Bottle housing 2C, 2K, 2M, 2Y toner bottle 3 Transfer device 4C, 4K, 4M, 4Y Image forming unit 5 Photoreceptor 6 Charging device 7 Developing device 8 Cleaning device 9 Exposure device 10 Paper feed tray 11 Paper Feed Roller 12 Resist Roller 13 Paper Discharge Roller 14 Paper Discharge Tray 20 Fixing Device 21 Fixing Belt 22 Pressurizing Roller 23A, 23B Halogen Heater 24 Nip Forming Member 24a, 24b Recess 24c Surface 25 Stay Member 25A First Member 25B Second Member 25a Standing part 26a, 26b End heater 27 Thermal transfer assisting member 27a Nip forming surface 28A, 28B Reflective member 29A, 29B Temperature sensor (temperature detector)
30 Intermediate transfer belt 31 Primary transfer roller 32 Secondary transfer backup roller 33 Cleaning backup roller 34 Tension roller 35 Belt cleaning device 36 Secondary transfer roller 41 Separation member N Fixing nip P Paper α β Irradiation angle

Japanese Unexamined Patent Publication No. 2010-32631 Japanese Unexamined Patent Publication No. 2016-145961

Claims (4)

With a flexible, endless belt,
A pressure member provided on the outside of the belt and facing the belt,
A nip forming unit provided inside the belt and forming a fixing nip between the belt and the pressurizing member, and a nip forming unit.
A heat source for heating the belt and
It has a temperature detection unit that detects the temperature of the belt, the heat source generates heat under lighting conditions where the temperature detected by the temperature detection unit does not reach the first predetermined temperature, and the detected temperature is the second. When the predetermined temperature is reached, the rotation of the belt is started, and the nip forming unit is arranged so as to cover the nip forming member and the surface of the nip forming member facing the inner peripheral surface of the belt. A plurality of heat transfer assisting members provided at both ends in the longitudinal direction of the surface of the nip forming member facing the heat transfer assisting member to heat the widthwise ends of the belt. A contact heat transfer type heat source is provided, and the lighting conditions of the plurality of contact heat transfer type heat sources are determined by the temperature of the belt at the start of lighting control of the heat source, which is a radiation type heat source, and the belt by the radiation type heat source. the second at the timing reaches a predetermined temperature, the contact heat transfer-type heat source is also controlled lighting conditions to reach the second predetermined temperature, characterized in Rukoto, fixing device. The heat source is a plurality of radiant heat sources having different light distributions in the longitudinal direction, and each of the plurality of radiant heat sources is lit so as to have a uniform temperature until the belt reaches the second predetermined temperature. The fixing device according to claim 1, wherein the fixing device is controlled by conditions. The fixing device according to claim 1 or 2 , wherein the belt has a plurality of rotation linear speeds, and the belt is rotated at a low rotation linear speed at least until the reload temperature is reached. An image forming apparatus comprising the fixing apparatus according to any one of claims 1 to 3 .

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