JP2012113243A - Fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device capable of suppressing application of great shear force to an interface between a core bar of a driving rotating body and an elastic layer during start up operation thereof, and further to provide an image forming device provided with the fixing device.SOLUTION: A fixing device comprises: a driving rotating body, which comprises a core bar and an elastic layer and is rotatably supported; a counter member disposed opposite to the driving rotating body; energization means for pressing the driving rotating body against the counter member by energizing one of the driving rotating body and the counter member toward the other thereof; driving means for rotationally driving the driving rotating body; and heating means for heating at least one of the counter member and the driving rotating body. In the fixing device, during a time period from commencement of startup operation thereof until completion of the startup operation thereof, the energization force generated by the energization means and applied to the driving rotating body or the counter member is increased stepwise up to the energization force applied thereto during fixing operation and a revolution speed of the driving rotating body is further increased stepwise by the driving means up to the revolution speed during the fixing operation.

Description

  The present invention relates to a fixing device used in an image forming apparatus such as a printer, a facsimile machine, and a copying machine, and an image forming apparatus including the fixing device.

  Conventionally, in an image forming apparatus, a latent image on an image carrier is developed with toner supplied from a developing device, and a toner image as a visible image is formed on the image carrier. The toner image on the image carrier is transferred to a recording material by a transfer device and fixed on the recording material by a fixing device.

  In the fixing device described in Patent Document 1, a pressure roller provided with an elastic layer on the outer side of a core metal that is a rotating shaft, and a fixing belt that is a facing member provided facing the pressure roller are attached. A fixing nip is formed by urging one of the pressure roller and the fixing belt toward the other by the urging force from the urging spring. Further, when the fixing belt and the pressure roller are brought into pressure contact with each other, a good fixing nip can be formed by elastic deformation of the elastic layer of the pressure roller.

  In such a fixing device, in the start-up operation for raising the temperature of the fixing belt to a predetermined temperature, the pressure roller is driven to rotate by a driving device while the fixing belt is heated by a heater as a heat source. The fixing belt is rotated by following the rotation of. Then, after the fixing belt reaches a predetermined temperature and the start-up operation is completed, the recording paper on which the toner image is adhered is sandwiched and conveyed by the nip portion, so that the toner image on the recording material is transferred by the heat or pressure. To be established.

  However, when the pressure roller is rotated from the stopped state, a static frictional force corresponding to the coefficient of static friction between the fixing belt and the pressure roller is generated in the fixing nip, and the pressure roller is driven by a driving device. A static frictional force acts in the direction opposite to the rotational drive direction. Therefore, if the fixing belt and the pressure roller are in pressure contact with the pressure at the time of fixing at the start of the start-up operation of the fixing device, a large static frictional force is generated, which is large at the interface between the pressure roller core metal and the elastic layer. There is a possibility that the elastic layer is peeled off from the cored bar due to the shearing force. Similarly, even when the pressure roller is stopped at the start of the start-up operation of the fixing device and is rapidly increased to the rotation speed during the fixing operation and rotated, the interface between the elastic layer of the pressure roller and the core metal is maintained. A large shearing force may work, and the elastic layer may peel off from the cored bar.

  Also, after the toner image on the image carrier is primarily transferred to the intermediate transfer belt, the toner image on the intermediate transfer belt is secondarily transferred to the recording material, and the toner image is fixed on the recording material by a fixing device. The same problem as described above also occurs in the fixing device used in the image forming apparatus of the type.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a fixing device capable of suppressing a large shearing force from acting on the interface between the cored bar and the elastic layer of the driving rotating body during the rising operation, and the fixing device therefor. Is provided.

In order to achieve the above-mentioned object, the invention of claim 1 comprises a drive rotating body comprising a cored bar and an elastic layer and rotatably supported, a counter member provided facing the drive rotating body, An urging means for urging one of the driving rotator and the opposing member toward the other to press-contact the driving rotator and the opposing member, a driving means for rotationally driving the driving rotator, and the opposing Heating means for heating at least one of a member and the drive rotator, and at least one of the opposing member and the drive rotator is heated by the heating means, and the drive rotator is rotated by the drive means. And fixing the toner image on the recording medium by heat or pressure while nipping and conveying the recording medium to which the toner image sent to the nip formed by the driving rotating body and the opposing member is adhered. Equipment The urging force applied to the drive rotator or the opposing member by the urging means is gradually increased to the urging force during the fixing operation between the start time and the completion time of the rising operation. The rotation speed is increased stepwise by the driving means up to the rotation speed during the fixing operation.
According to a second aspect of the present invention, in the fixing device according to the first aspect, after the last recording medium passes through the nip portion in response to an arbitrary print request, the urging means drives the driving rotary body or the opposing member. The urging force is reduced stepwise.
According to a third aspect of the present invention, in the fixing device of the first or second aspect, after the last recording medium passes through the nip portion in response to an arbitrary print request, the rotational speed of the driving rotating body is adjusted by the driving means. It is characterized by being made smaller in stages.
According to a fourth aspect of the present invention, in the fixing device according to the first, second, or third aspect, the driving means transmits driving to both axial ends of the driving rotating body via a driving transmission member. To do.
According to a fifth aspect of the present invention, in the fixing device of the first, second, third, or fourth aspect, the fixing device includes a temperature detecting unit that detects a surface temperature of the driving rotating body. Accordingly, the drive means adjusts the rotational speed of the drive rotator.
According to a sixth aspect of the present invention, in the fixing device of the first, second, third, fourth, or fifth aspect, the elastic layer of the driving rotating body is made of foamed silicone rubber.
According to a seventh aspect of the present invention, in the fixing device according to the first, second, third, fourth, or sixth aspect, the facing member is an endless belt member having flexibility, and the belt member is disposed at both ends. It is provided with a support member that can rotate, and a nip forming member that is provided inside the belt member and faces the driving rotating body via the belt member to form the nip portion.
Further, the invention of claim 8 is a latent image carrier, a latent image forming means for forming a latent image on the latent image carrier, and a toner made of an image forming material by developing the latent image on the latent image carrier. 8. An image forming apparatus comprising: a developing unit that forms an image; and a fixing unit that fixes the toner image to a recording medium. The fixing unit according to claim 1, wherein the fixing unit is a fixing unit. An apparatus is used.

  In the present invention, since the urging force of the urging means to the driving rotating body or the opposing member is gradually increased from the start of the rising operation to the completion of the operation until the urging force at the time of fixing operation, The pressure between the driving rotator and the opposing member increases stepwise up to the pressure during the fixing operation. As a result, the static frictional force generated between the drive rotator and the counter member is smaller than when the drive rotator and the counter member are in pressure contact with the pressure during the fixing operation at the start of the rising operation. Therefore, the shearing force generated at the interface between the cored bar of the driving rotating body and the elastic layer can be reduced by the amount of the static frictional force. In addition, from the start of the start-up operation to the completion of the operation, the rotational speed of the drive rotator is gradually increased to the rotation speed at the fixing operation by the driving means, so that the rotation speed at the fixing operation at the start of the start-up operation is increased. The shearing force generated at the interface between the core of the drive rotator and the elastic layer can be reduced as compared with the case where the drive rotator rotates.

  As described above, according to the present invention, it is possible to suppress a large shearing force from acting on the interface between the cored bar and the elastic layer of the driving rotating body during the rising operation.

The graph which shows the relationship between rise time, applied pressure, and process linear velocity. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment. 1 is a schematic configuration diagram of a fixing device according to an embodiment. FIG. 3 is a schematic diagram of the fixing device during a rising operation of the fixing device. The graph which shows the relationship between stop time, pressurizing force, and process linear velocity. The perspective view of a fixing belt, a pressure roller, and a drive roller.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 2 is a schematic configuration diagram of the image forming apparatus according to the present embodiment. As shown in FIG. 2, the image forming apparatus is an intermediate transfer that is an image carrier on which a color toner image composed of a plurality of colors of yellow (Y), cyan (C), magenta (M), and black (K) is formed. The intermediate transfer belt 1 as a body and toner bottles 2Y, 2C, 2M, and 2K that replenish each color toner for color toner images are accommodated in the image forming apparatus main body. The intermediate transfer belt 1 is rotatably stretched by a tension roller 1a, an intermediate transfer belt drive roller 1b, and the like, and the intermediate transfer belt 1 is also illustrated by rotating the intermediate transfer belt drive roller 1b counterclockwise in the drawing. Rotates counterclockwise.

  Further, the image forming apparatus conveys the transfer paper S loaded and stored in the paper feed tray 8 at the lower part of the image forming apparatus main body to the secondary transfer position facing the intermediate transfer belt 1 at a predetermined timing. The color toner image on the transfer belt 1 is transferred to the transfer paper S, the color toner image on the transfer paper S is fixed, and the fixed transfer paper S is discharged from above. That is, the sheet feeding roller 7 that feeds one sheet of transfer paper S, the registration roller pair 6 that secures the transfer timing for toner image transfer, and the intermediate transfer belt 1 are in contact with each other from the lower part to the upper part of the image forming apparatus. As described above, the secondary transfer roller 5 that is disposed opposite to the intermediate transfer belt driving roller 1b and that forms a secondary transfer nip that secures a predetermined pressure between the intermediate transfer belt 1 and a fixing device 4 that heats and pressurizes in a predetermined manner, A pair of paper discharge rollers 3 for discharging the transfer paper S to the outside of the apparatus is disposed, and in the course of transporting the transfer paper S along the transport path formed by these rollers and rollers, the secondary transfer nip is sequentially formed. Thus, the toner image is transferred from the intermediate transfer belt 1, and the toner image transferred onto the transfer paper S by the fixing device 4 is fixed.

  The process cartridges 101Y, 101C, 101M, and 101K are slanted to the left in the figure as image stations, which are four color image forming units that are responsible for each color for forming a color image and form a toner image of that color. The intermediate transfer belt 1 is disposed along the longitudinal direction of the intermediate transfer belt 1. Each image station including these process cartridges 101Y, 101C, 101M, and 101K has photosensitive drums 21Y, 21C, 21M, and 21K as image carriers.

  Further, the photosensitive drums 21Y, 21C, 21M, and 21K are in contact with the primary transfer rollers 11Y, 11C, 11M, and 11K through the intermediate transfer belt 1 with a predetermined pressure. Around the photosensitive drums 21Y, 21C, 21M, and 21K, dedicated charging devices 15Y, 15C, 15M, and 15K, developing devices 10Y, 10C, 10M, and 10K as developing units, and cleaning for cleaning the photosensitive members, respectively. And photosensitive member cleaning devices 14Y, 14C, 14M, and 14K as means.

  Below the process cartridges 101Y, 101C, 101M, and 101K, there is arranged a writing unit 9 that writes the electrostatic latent image by exposing the surface of each of the photosensitive drums 21Y, 21C, 21M, and 21K with laser light. .

  A belt cleaning device 12 that is a cleaning unit that collects and cleans residual toner on the intermediate transfer belt 1 is stretched through the intermediate transfer belt 1 on one end side in the longitudinal direction of the intermediate transfer belt 1. It is provided to face the gantry roller 1a.

  A plurality of toner bottles 2Y, 2C, 2M, and 2K that supply toner to the developing devices 10Y, 10C, 10M, and 10K are sequentially arranged from the left side to the right side in the drawing in the upper part of the apparatus, and are disposed on the main body of the image forming apparatus. It is provided to be detachable and replaceable. Each of the plurality of toner bottles 2Y, 2C, 2M, and 2K is filled with toners of yellow, cyan, magenta, and black, respectively. The toner bottles 2Y, 2C, 2M, and 2K are connected to each color developing device 10Y, 10C, 10M, and 10K corresponding to the toner bottles 2Y, 2C, 2M, and 2K through a conveyance path (not shown) so that toner can be supplied. The toner of each color is replenished by a predetermined replenishment amount.

  In the image forming apparatus configured as described above, when the transfer paper S is fed by the paper feed roller 7 and the leading edge reaches the registration roller pair 6, the leading edge of the transfer paper S is detected by a sensor (not shown). The transfer sheet S is conveyed to the nip formed by the secondary transfer roller 5 and the intermediate transfer belt 1 by the registration roller pair 6 while taking the synchronization timing based on the detection signal, and is transferred from the intermediate transfer belt 1 to the transfer sheet S. The image formed on the intermediate transfer belt 1 is secondarily transferred.

  The photosensitive drums 21Y, 21C, 21M, and 21K are uniformly charged in advance by the charging devices 15Y, 15C, 15M, and 15K, and then laser light is exposed and scanned by the writing unit 9 based on the image data. Electrostatic latent images are created on 21Y, 21C, 21M, and 21K. The electrostatic latent images are developed by the developing devices 10Y, 10C, 10M, and 10K for the respective colors, thereby forming yellow, cyan, magenta, and black toner images on the surfaces of the photosensitive drums 21Y, 21C, 21M, and 21K. Is done. Next, a voltage is applied to the primary transfer rollers 11Y, 11C, 11M, and 11K, and the toner on the photosensitive drums 21Y, 21C, 21M, and 21K is sequentially transferred onto the intermediate transfer belt 1. At this time, the image forming operation of each color is shifted in timing from the upstream side to the downstream side in the feeding direction of the intermediate transfer belt 1 so that the toner image is transferred to the same position on the intermediate transfer belt 1. Executed. The toner image formed on the intermediate transfer belt 1 is conveyed to the secondary transfer position where the secondary transfer roller 5 faces and is secondarily transferred to the transfer paper S. The transfer sheet S on which the color toner image of each color is transferred is conveyed to the fixing device 4, and the toner image is fixed by pressure and heat, and is discharged by the discharge roller pair 3.

  FIG. 3 shows an enlarged view of the fixing device 4. In the fixing device 4, a pressure roller 41 that is a rotatable pressure member, a fixing belt 42 that is an endless belt that is rotatably stretched by a support member, and the like are provided. Further, in the fixing belt 42, a nip forming member 43 is provided from the heat insulating material 45 so as to face the inner surface of the belt so as to be supported by the support body 46 via the heat insulating material 45, and through the mesh-like lubricating sheet 44. Thus, the inner surface of the belt and the nip forming member 43 are slid indirectly. Note that the nip forming member 43 and the inner surface of the belt may slide directly without using the lubricating sheet 44. The fixing belt 42 is heated by a halogen heater 47 which is a heat source, and the temperature of the fixing belt 42 is detected by a thermist 48.

  In FIG. 3, the shape of the fixing nip, which is a nip portion formed by pressure contact between the pressure roller 41 and the fixing belt 42, is a concave shape, but may be a flat shape or other shapes. When the fixing nip has a concave shape, the discharge direction of the leading edge of the sheet is closer to that of the pressure roller 41, and the separation of the sheet due to the curvature of the pressure roller 41 is improved, so that jamming is suppressed.

  The pressure roller 41 is obtained by adhering an elastic layer 41b made of a silicone rubber layer to the surface of a hollow metal roller that is a core metal 41a, and is released from the outer surface of the elastic layer 41b in order to obtain releasability. A layer (PFA or PTFE layer) is provided.

  The pressure roller 41 is rotated by a driving force transmitted by a driving device such as a motor, a driving roller, or a gear (not shown) provided in the image forming apparatus, and includes a CPU, a memory, and the like provided in the image forming apparatus main body. By controlling the drive device by the control unit, the process linear speed, which is the rotation speed of the pressure roller 41, can be freely changed at a predetermined timing.

  The pressure roller 41 is pressed against the fixing belt 42 by a spring or the like (not shown), and the elastic layer 41b is crushed and deformed by the pressure roller 41 and the fixing belt 42 being pressed against each other. A predetermined nip width is obtained. The pressure applied to the pressure roller 41 by the spring can be changed by expanding and contracting the spring by a general-purpose cam mechanism (not shown), and the cam mechanism is controlled and moved by the control unit. Thus, the pressure applied to the pressure roller 41 by the spring can be changed at a desired timing.

  A configuration is adopted in which the fixing belt 42 is pressed against the pressure roller 41 side via a nip forming member 43 by a spring or the like, and the pressure roller 41 and the fixing belt 42 are pressed against each other to form a fixing nip. Also good.

  The metal roller, which is the core metal 41a of the pressure roller 41, may be a solid roller instead of being hollow, but the hollow may have a smaller heat capacity. The pressure roller 41 may have a heating source such as a halogen heater.

  The silicone rubber layer used as the elastic layer 41b may be solid rubber, but if there is no heater inside the pressure roller 41, sponge rubber may be used. Sponge rubber is more preferable because it has higher heat insulating properties than the silicone rubber layer or solid rubber, and heat from the fixing belt 42 is less likely to be taken away.

  The fixing belt 42 is a metal belt such as nickel or stainless steel (SUS), or an endless belt or film using a resin material such as polyimide. The surface layer of the fixing belt 42 has a release layer such as a PFA or PTFE layer, and has a release property so that toner does not adhere.

  There may be an elastic layer formed of a silicone rubber layer or the like between the base material of the fixing belt 42 and the release layer. When there is no elastic layer between the substrate and the release layer, the heat capacity of the fixing belt 42 is reduced and the fixing property is improved. However, when the unfixed image is crushed and fixed, subtle irregularities on the belt surface are imaged. May cause a defect that a crusty skin-like mark remains on the solid portion of the image. In order to improve this, it is necessary to provide an elastic layer of 100 [μm] or more between the substrate and the release layer. By providing an elastic layer of 100 [μm] or more between the substrate and the release layer, the deformation of the elastic layer absorbs subtle irregularities on the belt surface and leaves a crusty skin-like mark on the solid portion of the image. Can be suppressed.

  The heat source for raising the temperature of the fixing belt 42 may be the illustrated halogen heater 47, but may be IH, a resistance heating element, a carbon heater, or the like.

  The fixing belt 42 is rotated by an external roller. In this embodiment, the pressure roller 41 is rotated by the driving device, and a driving force is transmitted from the pressure roller 41 to the fixing belt 42 at the fixing nip. The fixing belt 42 rotates. The fixing belt 42 is sandwiched and rotated by the nip forming member 43 and the pressure roller 41 at the fixing nip, but is guided by holding members that are held from both ends except for the fixing nip, and the cross-sectional shape of the fixing belt 42 is stable. The circular shape is maintained.

FIG. 4 is a schematic diagram of the fixing device 4 during the rising operation of the fixing device 4.
During the rising operation of the fixing device 4, a large shearing force acts on the bonding interface between the cored bar 41 a and the elastic layer 41 b of the pressure roller 41 due to the pressure at the fixing nip. Therefore, only during this rising operation, pressurization is performed with a pressure lower than the normal pressure for securing a predetermined nip width so that the normal pressure is gradually applied as shown in FIG.

  In the fixing device 4 of the present embodiment, as shown in FIG. 1, the rotation operation at the time of rising of the fixing device 4 is set to F [MPa] for the normal pressure during the fixing operation and T [s] for the rising time. In this case, pressure is applied with F / 3 [Mpa] from 0 [s] to T / 3 [s], and with 2F / 3 [Mpa] from T / 3 [s] to 2T / 3 [s], Until the subsequent rising operation is completed (from 2T / 3 [s] to T [s]), the pressure is rotated with the normal pressure F [Mpa]. That is, the pressurizing force is increased by F / 3 [MPa] in three stages from the start of the rising operation so that the pressurizing force becomes the normal pressing force F [MPa] during the fixing operation when the rising operation is completed. ing. Ideally, it is desirable that the pressure increase with respect to the rise time is directly proportional. However, since there is a concern that the mechanism and control become complicated, the fixing device 4 of the present embodiment performs control by dividing time and pressure into three stages.

  From the start of the start-up operation of the fixing device 4 to the completion of the operation, the pressure (biasing force) applied to the pressure roller 41 by the spring is increased stepwise up to the pressure applied during the fixing operation so that the pressure is pressed at the fixing nip. The pressure between the pressure roller 41 and the fixing belt 42 increases stepwise up to the pressure during the fixing operation. As a result, the stationary state generated between the pressure roller 41 and the fixing belt 42 is greater than when the pressure roller 41 and the fixing belt 42 are in pressure contact with the pressure during the fixing operation at the start of the rising operation of the fixing device 4. The frictional force is reduced. Therefore, the shear force generated at the interface between the cored bar 41a and the elastic layer 41b of the pressure roller 41 can be reduced by the amount of the static frictional force.

  Further, even in a configuration in which the fixing belt 42 is pressed against the pressure roller 41 side via the nip forming member 43 by a spring or the like and the pressure roller 41 and the fixing belt 42 are pressed against each other, the object to be pressed by the spring only changes. As described above, the above-described effect can be obtained by changing the applied pressure stepwise from the start of the rising operation to the completion of the operation.

  The minimum value (F / 3) of the pressing force is set to be equal to or higher than the minimum pressing force that causes the fixing belt 42 to rotate. Further, the change of the applied pressure is performed by controlling the cam mechanism by the control unit so that the spring contracts at every predetermined timing.

  The rotation operation of the fixing device 4 at the time of rising is defined as 0 [s] to T / 3 when the normal process linear velocity at the time of the fixing operation is V [mm / s] and the rising time is T [s]. Rotates at V / 3 [mm / s] until [s], and rotates at 2V / 3 [mm / s] from T / 3 [s] to 2T / 3 [s] until the subsequent start-up operation is completed ( 2T / 3 [s] to T [s]) at a normal process linear velocity V [mm / s]. That is, the process linear velocity is increased in three steps from the start of the start-up operation of the fixing device 4 in increments of V / 3 [mm / s], and when the start-up operation of the fixing device 4 is completed, the process linear velocity is The normal process linear velocity V [mm / s] is set.

  From the start of the start-up operation of the fixing device 4 to the completion of the operation, the control unit controls the driving device at a predetermined timing to set the process linear speed, which is the rotation speed of the pressure roller 41, to the process linear speed during the fixing operation. As the pressure roller 41 rotates at the process linear speed at the time of the fixing operation at the start of the rising operation of the fixing device 4, the core metal 41 a and the elastic layer 41 b of the pressure roller 41 are increased. The shearing force generated at the interface can be reduced.

  Further, by starting up at a low pressure and a low speed, the inflow of heat from the fixing belt 42 to be heated to the pressure roller 41 is reduced, and the rise time of the fixing device 4 can be shortened. It becomes possible.

  As shown in FIG. 5, in response to an arbitrary print request, when the time when the trailing edge of the final recording paper has passed through the fixing nip is 0 [s] and the time until operation stop is t [s], From 0 [s] to t / 2 [s], pressurization is performed with 2F / 3 [Mpa]. From t / 2 [s] to t [s], pressurization is performed with F / 3 [Mpa], and after t [s]. Is completely separated and stops operating.

  Also, in response to an arbitrary print request, when the time when the trailing edge of the final recording sheet passes through the fixing nip is 0 [s] and the time until the operation is stopped is t [s] Rotates at 2V / 3 [mm / s] until t / 2 [s], rotates at V / 3 [mm / s] from t / 2 [s] to t [s], and after t [s] Stop operation completely.

  In general, since the adhesive has a problem in heat resistance, the strength of the adhesive interface between the elastic layer 41b of the pressure roller 41 and the cored bar 41a becomes weak when the fixing device 4 is at a high temperature such as at the end of a printing request. Yes. For this reason, it is preferable to gradually decrease the applied pressure and the process linear velocity as in the fixing device 4 of the present embodiment.

  Even in the case where the fixing belt 42 is pressed against the pressure roller 41 via the nip forming member 43 by a spring or the like and the pressure roller 41 and the fixing belt 42 are pressed against each other, the object to be pressed by the spring only changes. As described above, in response to an arbitrary print request, the above-described change is made so that the pressure is gradually reduced from when the final trailing edge of the recording paper passes through the fixing nip until the operation is stopped. An effect can be obtained.

  As described above, the load on the bonding interface between the elastic layer 41b of the pressure roller 41 and the cored bar 41a is reduced by changing the pressing force and the process linear velocity step by step. In the case of one-side driving in which only one side of the pressure roller 41 in the axial direction is driven, twisting is likely to occur between the axial driving side and the non-driving side of the pressure roller 41. When such a twist occurs, the load on the bonding interface between the elastic layer 41b of the pressure roller 41 and the cored bar 41a increases.

  In order to further reduce the load on the bonding interface between the elastic layer 41b and the cored bar 41a of the pressure roller 41, it is desirable to eliminate this twist, and the driving roller provided in the driving device as shown in FIG. Rotational driving force is transmitted from the drive gears 52 provided at both ends in the axial direction of the shaft 51, which is the rotational axis of the shaft 51, to the pressure roller 41 via the transmission gears 53 provided on both sides in the axial direction of the pressure roller 41. Thus, the drive roller 50 can be equally driven from the pressure roller 41. Thereby, the twist of the pressure roller 41 as described above can be eliminated, and the load on the bonding interface between the elastic layer 41b of the pressure roller 41 and the cored bar 41a can be reduced.

  In the fixing device 4 of the present embodiment, the fixing nip width is ensured by pressing the nip forming member 43 processed with a resin or a metal material and the pressure roller 41 provided with the elastic layer 41b. In a configuration in which one member is hard and does not elastically deform, it is difficult to ensure a sufficient amount of nip width unless the elastic layer 41b of the pressure roller 41 is thickened.

  However, by increasing the thickness of the elastic layer 41b of the pressure roller 41, the change in the outer diameter of the pressure roller 41 due to thermal expansion increases. Since it is driven by the pressure roller 41, this change in the outer diameter is a change in the process linear velocity as it is, paper conveyance becomes unstable, and conveyance problems such as wrinkles and jams may occur. Therefore, the fixing device 4 of the present embodiment is provided with a thermistor 49 which is a temperature detecting means for detecting the surface temperature of the pressure roller 41. The thermistor 49 detects the temperature of the pressure roller surface and detects the detected temperature. By adjusting the process linear velocity (rotational speed) of the pressure roller 41 according to the temperature, it is possible to suppress a change in the process linear velocity due to the expansion of the pressure roller 41.

  Further, as the process linear speed of the fixing device 4 is increased, it is necessary to increase the thickness of the elastic layer 41b of the pressure roller 41 in order to ensure the nip width. Therefore, foamed silicone rubber having a low heat capacity is used for the elastic layer 41b. Thus, energy saving of the fixing device 4 can be achieved.

As described above, according to the present embodiment, the pressure roller 41 which is a driving rotating body composed of the core metal 41 a and the elastic layer 41 b and is rotatably supported, and the opposing member provided to face the pressure roller 41. The fixing belt 42, the spring that is an urging unit that urges one of the pressure roller 41 and the fixing belt 42 toward the other to press the pressure roller 41 and the fixing belt 42, and the pressure roller The driving device that is a driving unit that rotationally drives 41 and a halogen heater 47 that is a heating unit that heats at least one of the fixing belt 42 and the pressure roller 41 are provided. At least one of the roller 41 is heated, and the pressure roller 41 is rotated by the driving device, and fixing is a nip portion formed by the pressure roller 41 and the fixing belt 42. In the fixing device 4 for fixing the toner image on the transfer sheet S by heat or pressure while nipping and conveying the transfer sheet S as a recording medium to which the toner image sent to the toner image adheres, from the start of the rising operation. Until the completion of the process, the pressure applied to the pressure roller 41 or the fixing belt 42 by the spring is increased stepwise up to the pressure applied during the fixing operation, and the process line representing the rotation speed of the pressure roller 41. The speed is increased stepwise by the driving device up to the process linear speed during the fixing operation. As a result, the pressure between the pressure roller 41 and the fixing belt 42 in pressure contact with each other at the fixing nip gradually increases to the pressure during the fixing operation. Therefore, the static frictional force generated between the pressure roller 41 and the fixing belt 42 at the start of the rising operation is smaller than when the pressure roller 41 and the fixing belt 42 are in pressure contact with each other during the fixing operation. Therefore, the shearing force generated at the interface between the cored bar 41a and the elastic layer 41b of the pressure roller 41 can be reduced by the amount of the static frictional force. Further, by increasing the process linear speed of the pressure roller 41 in a stepwise manner from the start to the completion of the rising operation to the process linear speed during the fixing operation by the driving device, the core metal of the pressure roller 41 is increased. The shear force generated at the interface between 41a and the elastic layer 41b can be reduced.
In addition, according to the present embodiment, after the last transfer sheet S has passed through the fixing nip in response to an arbitrary print request, the pressure applied to the pressure roller 41 by the spring is reduced stepwise, thereby the fixing nip. The pressure between the pressure roller 41 and the fixing belt 42 that are in pressure contact with each other gradually decreases, and the shearing force generated at the interface between the core metal 41a of the pressure roller 41 and the elastic layer 41b can be reduced. Even when the strength of the adhesive interface between the elastic layer 41b of the pressure roller 41 and the cored bar 41a is weak at high temperatures, the elastic layer can be prevented from peeling off from the cored bar.
Further, according to the present embodiment, after the last transfer sheet S has passed through the fixing nip in response to an arbitrary print request, the process linear velocity of the pressure roller 41 is reduced stepwise by the driving device, thereby applying pressure. The shearing force generated at the interface between the cored bar 41a and the elastic layer 41b of the roller 41 can be reduced, and the strength of the bonding interface between the elastic layer 41b of the pressure roller 41 and the cored bar 41a is weak at high temperatures. The elastic layer can be prevented from peeling off from the cored bar.
Further, according to the present embodiment, the driving roller 50 provided in the driving device transmits the driving to the both ends in the axial direction of the pressing roller 41 via the driving gear 51 that is a driving transmission member, so that the pressing roller It is possible to suppress the occurrence of twisting in the axial direction of 41, and to reduce the load on the bonding interface between the elastic layer 41b of the pressure roller 41 and the cored bar 41a.
In addition, according to the present embodiment, the thermistor 49 that is a temperature detection unit that detects the surface temperature of the pressure roller 41 is provided, and the process line of the pressure roller 41 is driven by the driving device according to the detection result of the thermistor 49. By adjusting the speed, a change in the process linear speed due to the expansion of the pressure roller 41 can be suppressed.
Further, according to the present embodiment, the elastic layer 41b of the pressure roller 41 is made of foamed silicone rubber, so that energy saving of the fixing device 4 can be achieved.
In addition, according to the present embodiment, the driven rotating body is the fixing belt 42 that is a flexible endless belt member, and includes the halogen heater 47 that is a heat source for heating the fixing belt 42 and the fixing belt 42. A support 46 that is a support member that is rotatably supported at both ends, and a nip forming member 43 that is provided inside the fixing belt 42 and faces the pressure roller 41 via the fixing belt 42 to form the fixing nip. The configuration of the fixing device 4 can be employed.
Further, according to the present embodiment, the photosensitive drum 21 that is a latent image carrier, the writing unit 9 that is a latent image forming unit that forms a latent image on the photosensitive drum 21, and the latent image on the photosensitive drum 21. An image forming apparatus comprising: a developing device 10 that is a developing unit that develops an image to form a toner image made of an image forming substance; and a fixing unit that fixes the toner image to the transfer paper S. By using the fixing device 4 employing the above, it is possible to reduce the shearing force generated at the interface between the cored bar 41a and the elastic layer 41b of the pressure roller 41 and to suppress the peeling of the elastic layer from the cored bar. it can.

DESCRIPTION OF SYMBOLS 1 Intermediate transfer belt 1a Tension roller 1b Intermediate transfer belt drive roller 2 Toner bottle 3 Paper discharge roller pair 4 Fixing device 5 Secondary transfer roller 6 Registration roller pair 7 Paper feed roller 8 Paper feed tray 9 Writing unit 10 Developing device 11 Primary Transfer roller 12 Belt cleaning device 14 Photoconductor cleaning device 15 Charging device 21 Photoconductor drum 41 Pressure roller 41a Core metal 41b Elastic layer 42 Fixing belt 43 Nip forming member 44 Lubrication sheet 45 Heat insulating material 46 Support body 47 Halogen heater 101 Process cartridge

JP 2009-151118 A

Claims (8)

A driving rotating body composed of a mandrel and an elastic layer and rotatably supported;
A facing member provided to face the drive rotating body;
An urging means for urging one of the drive rotator and the opposing member toward the other to press-contact the drive rotator and the opposing member;
Drive means for rotationally driving the drive rotator;
Heating means for heating at least one of the facing member and the driving rotating body,
At least one of the opposing member and the driving rotator is heated by the heating means, and the driving rotator is rotated by the driving means, and is fed into a nip formed by the driving rotator and the opposing member. In a fixing device for fixing the toner image to the recording medium by heat or pressure while nipping and conveying the recording medium to which the toner image is adhered,
During the period from the start to the completion of the rising operation, the urging force applied to the drive rotator or the opposing member by the urging means is increased stepwise to the urging force during the fixing operation to rotate the drive rotator. A fixing device characterized in that the speed is increased stepwise by the driving means up to a rotational speed during a fixing operation. The fixing device according to claim 1.
A fixing device characterized in that, after the last recording medium passes through the nip portion in response to an arbitrary print request, the urging force of the urging means on the driving rotating body or the opposing member is reduced stepwise. The fixing device according to claim 1 or 2,
A fixing device characterized in that, after the last recording medium passes through the nip portion in response to an arbitrary print request, the rotational speed of the driving rotating body is reduced stepwise by the driving means. The fixing device according to claim 1, 2 or 3.
The fixing device according to claim 1, wherein the driving unit transmits driving to both axial ends of the driving rotating body via a driving transmission member. The fixing device according to claim 1, 2, 3 or 4.
It has a temperature detection means for detecting the surface temperature of the drive rotator,
A fixing device, wherein the driving means adjusts the rotational speed of the driving rotating body in accordance with a detection result of the temperature detecting means. The fixing device according to claim 1, 2, 3, 4 or 5.
The fixing device according to claim 1, wherein the elastic layer of the drive rotor is made of foamed silicone rubber. The fixing device according to claim 1, 2, 3, 4, 5 or 6.
The opposing member is a flexible endless belt member,
A support member that can rotate the belt member at both ends;
A fixing device, comprising: a nip forming member provided inside the belt member and facing the driving rotating body via the belt member to form the nip portion. A latent image carrier;
A latent image forming means for forming a latent image on the latent image carrier;
Developing means for developing a latent image on the latent image carrier and forming a toner image made of an image forming substance;
In an image forming apparatus comprising a fixing unit that fixes the toner image on a recording medium,
An image forming apparatus using the fixing device according to claim 1, as the fixing unit.

Images