JP6852370B2 - Fixing device and image forming device - Google Patents

Description

The present invention relates to a fixing device and an image forming 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, and multifunction devices having at least two functions thereof.

Among the image forming devices, the fixing device consumes a large amount of power and there is a lot of room for energy saving. Therefore, various proposals have been made, but in order to realize energy saving and improvement of the first print time, the heat capacity of the member is reduced. As I proceeded, further problems arose. In the fixing device, when passing a recording material (small size paper) whose width is narrower than the heating width of the heat source (heater) that heats the fixing belt, the temperature in the width direction of the fixing belt (direction orthogonal to the paper conveying direction). With respect to the above, a so-called edge temperature rise occurs in which the temperature rise becomes remarkable in the region outside the paper passing range. This is because the thinning of the fixing belt hinders heat transfer in the width direction of the fixing belt. In addition, the members constituting the fixing device such as the pressure roller / belt may reach the heat resistant temperature or higher, and the temperature in the region outside the paper passing range must be suppressed in order to protect the members. There was a problem (CPM down) that the productivity of paper passing had to be reduced. Further, there is also a problem that the toner is hot-offset near the end of the recording material (near the end in the width direction) due to the temperature rise at the end. In order to deal with these problems, for example, Patent Document 1 proposes a configuration in which a good heat conductive member is arranged in the fixing nip and the temperature gradient in the axial direction is relaxed by the fixing nip.

In order to improve the axial temperature uniformity in the fixing nip, it is preferable to use a good heat transfer member such as copper or aluminum as a heat transfer auxiliary member, but since it has good heat conductivity when warming up from room temperature, it heats. There is a problem that the heat of the fixing belt is absorbed by the entire movement assisting member, the temperature rise of the fixing belt is delayed, and the warm-up time is delayed. Since the above-mentioned end temperature rise is longer than the warm-up time on the time axis, a large delay in warm-up time can be prevented by providing a thin thermal resistance layer on the surface of the heat transfer assisting member. It will be a negative factor to ensure the uniformity of the axial temperature.

Further, the fixing nip is a portion where the toner is fixed to the recording material by the pressing force, and sliding resistance is generated between the fixing belt and the heat transfer assisting member, so that it is necessary to reduce the friction. Conventionally, as a means for this, a sliding contact sheet made of a thin film and a material such as fluorine is provided on the surface of the heat transfer assisting member. Such means can reduce the sliding resistance, but if the adhesion to the heat transfer assisting member is poor, the temperature gradient relaxation function may be impaired. Further, as a thin film sliding contact sheet, a porous or fibrous sliding contact material that holds a lubricant and can maintain a low torque for a long period of time is known. The heat conduction was poor because it was high. On the other hand, the non-porous material has a problem that the retention of the lubricant is poor, and the lubricant flows out from the end face of the fixing belt and the torque increases with time.

Of these problems, the problem of adhesion can be solved by coating the heat transfer auxiliary member with a sliding contact sheet or a low friction material, but regarding the retention of the lubricant, the low viscosity lubricant is the end face of the fixing belt. The high-viscosity lubricant tends to flow out from the lubricant, and the outflow from the lubricant supply means is not stable. Further, when the lubricant is exposed to a high temperature for a long period of time, the oil component volatilizes and the viscosity of the lubricant increases, so that the torque (sliding resistance) increases. On the other hand, Patent Document 2 discloses a technique in which a lubricant supply means is always in contact with the inner surface of a fixing belt to replenish and adjust the lubricant.

However, even if the lubricant supply means holds the excess lubricant, if it is always in contact with the fixing belt, it is not possible to prevent the fixing belt from being deteriorated due to the outflow and volatilization of the lubricant and the mixing of abrasion powder, and the torque. There was a problem that the increase was suppressed and the life-prolonging effect obtained by the suppression was small.

Therefore, the present invention suppresses the lubrication function from being impaired due to the outflow of the lubricant from the fixing member and the nip forming member, the volatilization of the lubricant itself, and the increase in viscosity due to the mixing of wear powder, thereby driving the fixing member. An object of the present invention is to provide a fixing device capable of suppressing an increase in torque required for rotation for a long period of time.

In order to solve this problem, a flexible endless fixing member, a pressure member provided outside the fixing member and facing the fixing member, and a heat source provided inside the fixing member are used. In a fixing device having a nip forming member provided inside the fixing member and forming a fixing nip between the fixing member and the pressurizing member, a first lubricant is applied to an inner peripheral surface of the fixing member. The second lubricant, which is applied to and is a replenishing lubricant, is provided inside the fixing member so as not to come into contact with the fixing member in the normal control state, and the number of rotations in the normal control state. We propose a fixing device characterized in that the fixing member and the second lubricant come into contact with each other by a predetermined control in which the fixing member is rotated and controlled at a higher rotation speed.

According to the present invention, since the second lubricant, which is a replenishing lubricant, can be supplied to the inner peripheral surface of the fixing member as needed, an increase in the viscosity of the lubricant can be suppressed. Further, since the second lubricant is not in contact with the inner peripheral surface of the fixing member under normal control conditions, it is possible to minimize the mixing of wear debris and the outflow of oil and to supply a fresh lubricant. Therefore, the torque increase can be suppressed for a long period of time.

It is a schematic diagram which shows the image forming apparatus which concerns on one Embodiment of this invention. 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 perspective view which shows the structure of the nip formation unit and the halogen heater. It is a schematic diagram which shows the arrangement of the heat generating part of two halogen heaters. It is a graph which shows the relationship between the apparent viscosity of a lubricant and the drive rotation torque of a fixing belt. It is a figure which shows the measuring method of the locus of a fixing belt during rotation. It is a figure which shows the fluctuation of the locus of a fixing belt roughly. It is a figure which shows the actual belt displacement amount when the belt control temperature is changed. It is a figure which shows the normal control state of a fixing belt. It is a figure which shows the belt locus at the time of the low temperature belt temperature control.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a schematic view showing an image forming apparatus according to an embodiment of the present invention. 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 spreading 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 of the image forming units 4Y, 4C, 4M, and 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. 1, only the photoconductor 5, the charging device 6, the developing device 7, and the cleaning device 8 included in the black image forming section 4K are designated by reference numerals, and the other image forming sections 4Y, 4C, and 4M are designated by reference numerals. It is omitted.

An exposure device 9 that exposes the surface of the photoconductor 5 is arranged below the image forming 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 forms an intermediate transfer nip by sandwiching an intermediate transfer belt 30 with each photoconductor 5. 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. 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. Further, 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, a fixing device 20 for fixing the unfixed image transferred to the paper P is arranged on the downstream side in the paper transport direction from the position of the secondary transfer roller 36. 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, a paper ejection tray 14 for stocking the paper ejected outside the apparatus is provided on the upper surface of the printer main body.

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 on the intermediate transfer belt 30 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 orbits travel, the toner image on the intermediate transfer belt 30 is generated by the transfer electric field formed at the nip. 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.

FIG. 2 is a schematic cross-sectional configuration diagram showing an embodiment of the fixing device 20. The fixing device 20 includes an endless fixing belt 21 which is a thin and flexible tubular fixing member, and a pressure roller 22 which is a pressure member provided on the outside of the fixing belt 21 and facing the fixing belt 21. And have. 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 heat sources arranged inside (inside the loop). .. The halogen heater is representative of a radiant heat source as a fixing 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 soaking member that relaxes the temperature gradient in the width direction (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 belt. Prevents heat from staying in the end region of the fixing belt 21 when passing small-sized paper, and positively transfers heat in the width direction of the fixing belt 21, that is, in the longitudinal direction of the heat transfer assisting member 27. , Eliminates 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 or aluminum, 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, and is a nip forming surface, which is formed flat. However, it may have a concave shape or other shape. With the concave nip forming surface, the discharge direction of the paper tip is closer to the pressure roller, the separability is improved, and the occurrence of jam is suppressed.

As is well known, a temperature sensor 29 for detecting the belt temperature is provided at an appropriate position on the outer peripheral side of the fixing belt 21, for example, on the upstream side of the fixing nip in the belt rotation direction, and is downstream of the fixing device 20 in the paper transport direction. On the side, a separating member 41 that separates the paper P from the fixing belt 21 is arranged. Further, a releaseable pressurizing means for pressurizing the pressurizing roller 22 onto the fixing belt 21 is also 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 a base material on the inner peripheral side 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 substantially L-shaped cross section, composed of the first member 25A and the second member 25B and having a T-shaped cross section as a whole, has an upright portion 25a on which the side opposite to the fixing nip N side stands up. Halogen heaters 23A and 23B as fixing heat sources are arranged so as to be separated by an upright portion 25a, and also function as a partition member. 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. As is well known, the elastic layer of the pressurizing roller 22 is crushed at a position where the pressurizing roller 22 is pressed against the fixing belt 21 by the spring of the pressurizing means and is in pressure contact with the fixing belt 21, so that the fixing nip having a predetermined width is formed. N is formed. 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 other than the fixing nip N, the fixing belt 21 is guided by the side plate flanges arranged at both ends and travels.

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. 3 is a perspective view showing the basic configuration of the nip forming unit (depiction of the portion accommodating the second lubricant is omitted). As shown in FIG. 3, 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, a concave-convex shape such as a boss and a pin 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 integral configuration of the heat transfer assisting member 27 and the nip forming member 24 may be provided with claws or the like so as to be engaged with each other. As shown in FIG. 2, a second lubricant 241 is arranged inside the fixing belt 21, which will be described later.

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 surface is substantially the nip forming surface. The surface 24c facing the compression roller 22.

FIG. 4 is a perspective view showing the configurations of the nip forming unit and the halogen heater. As shown in FIG. 4 and as described with respect to FIG. 2, the stay member 25 is composed of a first member 25A and a second member 25B having a substantially L-shaped cross section, and has a substantially T-shaped cross section. .. Therefore, the rigidity is high, and it is possible to prevent the nip forming member 24 from bending due to the stress from the pressure roller 22. Further, the stay member 25 (first member 25A and second member 25B) extends linearly in the longitudinal direction of the nip forming member 24 and is fixed to the nip forming member 24. Therefore, a good nip forming surface can be maintained over the entire longitudinal direction of the fixing nip N.

A first halogen heater 23A and a second halogen heater 23B are arranged on both sides of the upright portion 25a in the lateral direction, respectively. That is, the first halogen heater 23A and the second halogen heater 23B are mutually shielded by the upright portion 25a. Further, since the first halogen heater 23A and the second halogen heater 23B are not surrounded by the stay member 25 (the center of each halogen heater 23 is outside the space surrounded by the stay member 25), the first halogen heater 23A and the second halogen heater 23B are not surrounded by the stay member 25. The irradiation angles α and β (see FIG. 2) become obtuse angles, and the heating efficiency can be improved.

The cross-sectional shape of the stay member 25 is not limited to the substantially T shape. The halogen heaters 23A and 23B may be arranged so as to sandwich the upright portion 25a and partition the halogen heaters 23A and 23B from each other, and the first member 25A and the second member 25B may extend curvedly in the longitudinal direction of the halogen heater. Further, the first member 25A and the second member 25B may be erected in an oblique direction with respect to the nip forming surface of the nip forming member 24.

Further, as can be seen from FIGS. 4 and 5, the first halogen heater 23A has a heat generating portion (a portion in which the filament is spirally wound and the light distribution is dense) in the central portion in the longitudinal direction, and is fixed. It heats the central range of the belt 21 and corresponds to small size paper such as A4 vertical size. On the other hand, the second halogen heater 23B has heat generating portions at both ends in the longitudinal direction and heats the side portion range of the fixing belt 21. Then, when passing a large size paper such as A3 vertical size paper, not only the first halogen heater 23A but also the second halogen heater 23B is turned on to correspond to the large size paper. 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, and the output control is controlled by a temperature sensor 29 provided on the outer periphery of the fixing belt 21 on the surface of the belt. It is performed based on the temperature detection result. By controlling the output of such a heater, the temperature of the fixing belt 21 (fixing temperature) can be set to a desired temperature.

In this way, the two halogen heaters 23A and 23B correspond to different sizes of paper, but when paper of different sizes is used, heat is absorbed by the paper in the paper-passing area, while heat is absorbed in the non-paper-passing area. Instead, it is heated wastefully, and the problem of overheating may occur. However, in the present embodiment, the heat transfer assisting member 27 made of a material having high thermal conductivity positively transfers heat in the width direction of the fixing belt 21, that is, in the longitudinal direction of the heat transfer assisting member 27. , The temperature non-uniformity in the longitudinal direction is eliminated.

However, since the heat transfer assisting member 27 is in sliding contact with the inner peripheral surface of the fixing belt 21, if a material having high thermal conductivity such as copper or aluminum is directly brought into sliding contact with the inner peripheral surface of the fixing belt 21, the friction coefficient is increased. There are problems such as a large unit torque and a short life of the device. Therefore, it is also desirable to make the belt sliding contact surface 27a (see FIG. 3) of the heat transfer assisting member 27 facing (contacting) the fixing belt 21 as smooth as possible and to perform a low friction treatment. Specifically, a fluorine-based coating or coating such as PFA or PTFE is applied to the belt sliding contact surface 27a.

In the present embodiment, the sliding resistance is further reduced by interposing a lubricant between the heat transfer assisting member 27 and the inner peripheral surface of the fixing belt 21. At that time, a second lubricant 241 which is a further lubricant is added in order to suppress a defect due to abrasion powder generated with time between the heat transfer assisting member 27 and the inner peripheral surface of the fixing belt 21. It has become so. That is, as shown in FIG. 2, the first lubricant 240 is first applied to the inner peripheral surface of the fixing belt 21 in advance, and the fixing belt 21 is rotated by the rotation of the pressurizing roller 22 to generate heat. It also adheres to the surface of the movement assisting member 27. As this lubricant, a grease containing fluorine oil or silicone oil as the base oil, a thickener as an additive, or PTFE as a solid lubricant can be used, but in this example, the base oil is fluorine oil. .. Low torque is maintained by using semi-fluid or extremely soft grease with a consistency of about 0 to 0. When fluorine oil is used as the base oil, the heat resistance is higher and the chemical stability is higher than when silicone oil is used. Therefore, even if there is a heat source in the fixing belt 21, volatilization loss and deterioration can be suppressed. it can.

FIG. 6 is a graph showing the relationship between the apparent viscosity of the lubricant and the drive rotation torque of the fixing belt 21.
Here, the lubricant means, for example, the first lubricant 240. As shown in the figure, when the viscosity of the lubricant increases, the drive rotation torque (sliding resistance) of the fixing belt 21 increases. This is because when the liquid base oil in the lubricant volatilizes or flows out to the outside, the ratio of solid components increases and the lubricant thickens. Furthermore, the lubricant is thickened by the addition of abrasion powder to the lubricant.

FIG. 7 is a diagram showing a method of measuring the locus of the fixing belt 21 during rotation.
As shown in the figure, the displacement amount of the fixing belt 21 was measured by irradiating the outer circumference of the fixing belt 21 with the lasers of the laser displacement meters 51, 52, 53 from three directions. Specifically, the laser displacement meter 51 is the belt on the downstream side of the fixing nip N, the laser displacement meter 52 is the belt on the upstream side of the fixing nip N, and the laser displacement meter 53 is the displacement amount of the belt on the opposite side of the fixing nip N. It was measured. As the laser displacement meter, a high-speed, high-precision CCD laser displacement meter LK-G3000 manufactured by KEYENCE Corporation was used. As a result, it was found that the locus of the belt can be changed by causing the fixing belt 21 to perform a predetermined operation by control. FIG. 8 schematically shows the fluctuation of the locus of the fixing belt.

In FIG. 8, the locus 210 shown by the solid line shows the locus of normal belt rotation, and the loci 210a and 210b shown by the broken line show the locus of the belt during predetermined control. Here, the predetermined control refers to a control for changing the control temperature of the belt and a control for changing the control rotation speed of the belt. Specifically, by lowering the control temperature of the fixing belt 21 or increasing the rotation speed of the fixing belt 21, the belt portion on the upstream side of the fixing nip or near the entrance of the fixing nip is recessed inward (trajectory 210a). On the contrary, by raising the control temperature of the fixing belt 21 or lowering the rotation speed of the fixing belt 21, the belt portion on the upstream side of the fixing nip or near the entrance of the fixing nip swells outward (trajectory 210b). However, the belt portion on the downstream side of the fixing nip or near the exit of the fixing nip is not significantly displaced. This is because, as shown in the figure, the amount of belt displacement on the upstream side of the fixing nip is absorbed at the position facing the fixing nip.

FIG. 9 is a diagram showing an actual belt displacement amount when the belt control temperature is changed.
As shown in the figure, in the temperature range of 100 to 200 ° C., the amount of belt displacement on the upstream side of the fixing nip behaves substantially linearly. Specifically, the fixing belt 21 is displaced inward or outward with respect to the locus 210 (FIG. 8) when the belt rotates at a normal temperature by about 0.3 mm with a change of about 50 ° C. On the other hand, the amount of belt displacement on the downstream side of the fixing nip is substantially 0 regardless of the temperature change. In FIG. 9, the displacement amount is displayed with the case where the fixing belt 21 is displaced inward as positive. That is, when the temperature of the fixing belt 21 is lowered by about 50 ° C., it is displaced inward by about 0.3 mm (displacement amount is +0.3 mm), and when the temperature is raised by about 50 ° C., it is displaced outward by about 0.3 mm (displacement amount is −0). .3 mm).

Therefore, in the normal control state of the fixing belt 21 shown in FIG. 10, the replenishing lubricant holding member 26 holding the second lubricant 241 with a gap of, for example, 0.3 mm from the inner peripheral surface of the fixing belt 21 is provided. Deploy. That is, the replenishing lubricant holding member 26 and the second lubricant 241 are arranged inside the fixing belt so as not to come into contact with the fixing belt 21 in the normal belt temperature control state and the belt speed rotation. Here, the normal belt temperature control state and the normal belt speed rotation are referred to as "normal control states". The "normal control state" may include the non-rotating time of the fixing belt, that is, the replenishing lubricant holding member 26 and the second lubricant 241 do not come into contact with the fixing belt 21 during the non-rotating time. It may be arranged inside the fixing belt. Then, the fixing belt 21 and the second lubricant 241 come into contact with each other under predetermined control.

As described above, the lubricant decreases due to outflow and volatilization as it is used, which causes an increase in torque. If the lubricant is replenished, the life is extended, but if the second lubricant 241 is always in contact with the inner peripheral surface of the fixing belt 21, the second lubricant 241 also decreases with time. Therefore, in a normal control state, a gap is provided between the second lubricant 241 and the inner peripheral surface of the belt, and if necessary, the second lubricant 241 and the inner peripheral surface of the belt are brought into contact with each other by predetermined control. By supplying the lubricant, it is possible to suppress an increase in the sliding resistance and a decrease in the second lubricant 241.

The replenishing lubricant holding member 26 is fixed to the side plate of the fixing device 20 at both ends in the width direction (vertical direction on the paper surface). The second lubricant 241 preferably projects from the replenishing lubricant holding member 26 toward the inner peripheral surface of the fixing belt 21. Further, when it is necessary to replenish the second lubricant 241, in order to bring the fixing belt 21 and the second lubricant 241 into contact with each other, as a predetermined control, the fixing belt 21 is placed at a temperature higher than the temperature in the normal control state. The temperature is lowered by 50 ° C or more and the rotation is controlled. With such control, as shown in FIG. 11, the fixing belt 21 on the inlet side of the fixing nip can be displaced inward and brought into contact with the second lubricant 241 as compared with the normal time (trajectory 210). (Trajectory 210a), the second lubricant 241 can be replenished to the inner peripheral surface of the belt. Therefore, the sliding resistance can be reduced. FIG. 10 shows a belt locus under normal belt temperature control, and FIG. 11 shows a belt locus under low temperature belt temperature control.

Further, it is preferable that the replenishing lubricant holding member 26 and the second lubricant 241 are arranged within 180 ° on the upstream side with respect to the position of the fixing nip. This is because the amount of deformation of the fixing belt 21 on the upstream side of the fixing nip is large, so that the second lubricant 241 and the fixing belt 21 can be easily brought into contact with each other, which is particularly effective in the contact method using the belt deformation.

The viscosity of the second lubricant 241 as the replenishing lubricant is preferably lower than the viscosity of the first lubricant 240 applied to the inner peripheral surface of the fixing belt 21 from the beginning. By replenishing the low-viscosity lubricant, the original lubricant (first lubricant 240) that has thickened can be returned to the low-viscosity lubricant, suppressing the increase in rotational torque and sliding friction. be able to.

Further, in order to bring the fixing belt 21 into contact with the lubricant, belt speed control may be used in combination with or in addition to the belt temperature control of the fixing device 20. That is, as a predetermined control, the fixing belt 21 may be rotated and controlled at a rotation speed higher than the belt rotation speed in the normal control state in which the fixing belt 21 and the lubricant are not in contact with each other. When the belt rotation speed is increased, the fixing belt 21 on the inlet side of the fixing nip is deformed to the inner surface side of the belt, and comes into contact with the lubricant of the replenishing lubricant holding member 26 arranged close to the fixing belt, and the inner surface of the belt is contacted. Lubricant is supplied to the belt, and the sliding resistance can be reduced. That is, the belt locus when the fixing belt 21 is rotated at a rotation speed higher than the normal belt rotation speed is the same as the locus 210a shown in FIG. The combined use of belt speed control is particularly effective when it is desired to further increase the amount of belt displacement or when it is not desired to significantly reduce the belt temperature. By combining these, it is possible to reliably secure the amount of belt displacement required for supplying the lubricant to the inner peripheral surface of the belt.

As the replenishing lubricant holding member 26 and the second lubricant 241, it is desirable that the lubricant is held by a porous or fibrous sliding contact material, and the sliding contact material is sufficiently impregnated with the lubricant. Just leave it. Further, instead of the replenishing lubricant holding member 26 and the second lubricant 241 shown in FIG. 10, a cylindrical or cylindrical second lubricant is rotated with a gap from the inner peripheral surface of the fixing belt 21. It may be arranged as possible. Since the cylindrical or cylindrical lubricant rotates even when it comes into contact with the inner peripheral surface of the belt, the rotational resistance due to the contact with the inner peripheral surface of the belt can be minimized.

As described above, apart from the first lubricant 240 adhering to the inner peripheral surface of the fixing belt 21, the second lubricant 241 is brought into direct contact with the inner surface of the belt in the upstream region of the fixing nip inside the fixing belt 21. Place them with a gap. Then, if necessary, the belt locus is pulled inward by using some means (temperature control, rotation speed control, or both), and is brought into contact with the second lubricant 241 to additionally supply the lubricant to the inner surface of the belt. Therefore, it is possible to suppress an increase in the viscosity of the lubricant in the fixing belt. Therefore, the increase in torque can be suppressed for a long period of time.

Although 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 device 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. In addition, various changes can be made without departing from the gist of the present invention.

1 Image forming device 2 Bottle accommodating unit 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 210 Normal temperature control belt locus 210a Low temperature control locus 210b High temperature control locus 22 Pressurized rollers 23A, 23B Halogen heater 24 Nip forming member 24c Surface 25 Stay member 25A 1st member 25B 2nd member 25a Standing part 26 Replenishment lubricant holding member 27 Thermal transfer auxiliary member 27a Belt sliding contact surface 28A, 28B Reflective member 29 Temperature sensor 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

JP-A-2015-99352 Japanese Unexamined Patent Publication No. 2014-178520

Claims (6)

A flexible, endless fixing member and
A pressurizing member provided on the outside of the fixing member and facing the fixing member,
A heat source provided inside the fixing member and
In a fixing device having a nip forming member provided inside the fixing member and forming a fixing nip between the fixing member and the pressure member.
The first lubricant is applied to the inner peripheral surface of the fixing member.
A second lubricant, which is a replenishing lubricant, is provided inside the fixing member so as not to come into contact with the fixing member under normal control conditions.
A fixing device characterized in that the fixing member and the second lubricant come into contact with each other by a predetermined control in which the fixing member is rotated and controlled at a rotation speed higher than the rotation speed in the normal control state. A flexible, endless fixing member and
A pressurizing member provided on the outside of the fixing member and facing the fixing member,
A heat source provided inside the fixing member and
In a fixing device having a nip forming member provided inside the fixing member and forming a fixing nip between the fixing member and the pressure member.
The first lubricant is applied to the inner peripheral surface of the fixing member.
A second lubricant, which is a replenishing lubricant, is provided inside the fixing member so as not to come into contact with the fixing member under normal control conditions.
A fixing device characterized in that the fixing member is controlled to a temperature lower than the temperature in the normal control state, and the fixing member and the second lubricant come into contact with each other by a predetermined control of rotation. The fixing device according to claim 1 or 2, wherein the second lubricant is arranged within 180 ° on the upstream side with respect to the position of the fixing nip. The fixing device according to any one of claims 1 to 3, wherein the second lubricant is cylindrical or cylindrical and is rotatable. The fixing device according to any one of claims 1 to 4, wherein the viscosity of the second lubricant is lower than the viscosity of the first lubricant. An image forming apparatus comprising the fixing apparatus according to any one of claims 1 to 5.

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