JP2014178586A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device capable of suppressing driving means from being broken due to continuous application of a high load to the driving means during warm-up operation, and an image forming apparatus.SOLUTION: A fixing device includes a fixing belt that has a lubricant applied on an inner peripheral surface, heating means for heating a portion of the fixing belt other than a fixing nip, a pressure roller that is brought into contact with the fixing belt, driving means for at least one of the fixing belt and the pressure roller, and a nip forming member that is arranged on an inner peripheral side of the fixing belt. The fixing device performs at least once or more times a series of controls of: first control to control, with control means, the driving means and the heating means to heat the fixing belt during warm-up operation for a predetermined time while the rotation of the fixing belt is stopped; second control to rotate, after the completion of the first control, the fixing belt for a predetermined time, bring a heated portion of the fixing belt to reach the fixing nip, and stop the rotation of the fixing belt; and third control to maintain the rotation stop state of the fixing belt for a predetermined time.

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.

  As a fixing device used in various image forming apparatuses such as a copying machine, a printer, a facsimile, or a composite machine of these, there is known a fixing device having a thin fixing belt having a smaller heat capacity than a fixing roller. As described above, by providing the thin fixing belt having a low heat capacity, the energy required for heating the fixing belt can be greatly reduced, and the warm-up time and the first print time can be shortened.

  In the fixing device described in Patent Document 1, an endless fixing belt, a pressure roller in contact with the outer peripheral surface of the fixing belt, and an inner peripheral side of the fixing belt are in contact with the pressure roller via the fixing belt. A nip portion is formed between the fixing belt and the pressure roller by the nip forming member. Further, a heat source that is a heating means for heating the fixing belt by radiant heat is provided on the inner peripheral side of the fixing belt, and a portion other than the fixing nip that contacts the nip forming member of the fixing belt is heated by the radiant heat from the heat source. The

  In such a fixing device, when the fixing belt is rotated during the printing operation, the driving torque for rotating the fixing belt due to the sliding load between the fixing belt and the nip forming member is higher than that when the fixing roller is used. Get higher. Therefore, a lubricant such as grease or oil is applied to the inner peripheral surface of the fixing belt, the frictional resistance between the fixing belt and the nip forming member is lowered to reduce the sliding load, and the driving torque is reduced during the printing operation. Is planned.

  However, since the use temperature of the lubricant is usually assumed to be around the fixing temperature, the viscosity of the lubricant is high when the fixing device is cooled. Therefore, when the warm-up operation of the fixing device is started, the sliding load between the fixing belt and the nip forming member is increased due to the presence of a low-temperature and high-viscosity lubricant, and the driving torque at the start of the warm-up operation is very high. It will be high.

  In the fixing device described in Patent Document 1, while the fixing belt is heated at the start of the warm-up operation, the driving roller rotates the pressure roller at a lower rotational speed than during the normal printing operation. The fixing belt is rotated by being driven by the rotation. Thus, by reducing the rotation speed of the pressure roller, it is said that the driving torque can be reduced as compared with the case where the pressure roller is rotated at the same rotation speed as in the normal printing operation.

  However, even if the rotation speed of the pressure roller is slowed at the start of the warm-up operation, the pressure roller remains in a state where the drive torque is high from the start of the warm-up operation until the lubricant is warmed and the viscosity is sufficiently lowered. Will continue to be driven. For this reason, a problem may occur that a high load is continuously applied to the drive gear and the drive motor of the drive device that drives the pressure roller, and the drive gear and the drive motor are broken.

  The same problem as described above can also occur in the configuration in which the fixing belt is rotationally driven by the driving device, and in the configuration in which both the pressure roller and the fixing belt are rotationally driven by the driving device.

  The present invention has been made in view of the above problems, and an object of the present invention is to fix a fixing device that can prevent the driving unit from being broken due to a high load being continuously applied to the driving unit during a warm-up operation, and the fixing device. Is provided.

  In order to achieve the above object, the invention according to claim 1 is a rotatable endless fixing belt having an inner peripheral surface coated with a lubricant, and a rotatable pressure roller in contact with the outer peripheral surface of the fixing belt. And a driving means for rotationally driving at least one of the fixing belt and the pressure roller, and disposed on the inner peripheral side of the fixing belt to contact the pressure roller via the fixing belt to form a fixing nip. In a fixing device including a nip forming member and a heating unit that heats a portion other than the fixing nip of the fixing belt, the heating of the fixing belt by the heating unit is performed for a predetermined time while the fixing belt is stopped. At least after the first control for controlling the heating means and the execution of the first control, the fixing belt is rotated for a predetermined time, and the heated portion of the fixing belt reaches the fixing nip. And at least the second control for controlling the driving means so as to stop the rotation of the fixing belt, and at least so as to maintain the rotation stop state of the fixing belt for a predetermined time after the execution of the second control. And a third control unit for controlling the driving unit. The first control is performed during a warm-up operation for raising the temperature of the fixing belt before feeding the recording medium to the fixing nip. After the execution, a series of control of the second control and the third control is performed at least once.

In the present invention, during the warm-up operation, the drive means and the heating means are controlled by the control means, and a series of control of the second control and the third control is performed at least once. As a result, heat is transmitted from the fixing belt to the nip forming member and the pressure roller at the fixing nip, and the lubricant existing between the fixing belt and the nip forming member is warmed to reduce the viscosity. Therefore, the sliding load between the fixing belt and the nip forming member due to the viscosity of the lubricant can be reduced, and the driving torque for rotating the fixing belt can be reduced.
Further, during the warm-up operation, the lubricant existing between the fixing belt and the nip forming member is removed while intermittently rotating the fixing belt in the series of controls of the second control and the third control. The viscosity is lowered by warming. Accordingly, it is possible to shorten the time for rotating the fixing belt while the viscosity of the lubricant existing between the fixing belt and the nip forming member is higher than when the fixing belt continues to rotate during the warm-up operation. Therefore, it is possible to reduce the load applied to the driving unit, and to prevent the driving unit from being broken.

  As described above, according to the present invention, there is an excellent effect that it is possible to prevent the drive unit from being broken due to a high load continuously applied during the warm-up operation.

The control flowchart of warm-up operation | movement. 1 is a schematic configuration diagram of a printer according to an embodiment. FIG. 3 illustrates a configuration of a fixing device. FIG. 4 is an explanatory diagram of a state in which the fixing device is in a drive stop state and is not performing a heating operation. FIG. 4 is an explanatory diagram when the fixing device starts a warm-up operation from an initial state. Normal warm-up operation control flowchart Explanatory drawing in the state which driven the pressure roller only for the fixed time, continuing heating operation. FIG. 3 is an explanatory diagram in a state where a heated fixing belt region A is stopped at a position in contact with a fixing nip N; (A) Graph when heater output is not limited, (b) Graph showing when heater output is limited. A graph when the heater output is limited to 50% of the maximum output value.

  FIG. 2 is a schematic configuration diagram of a color laser printer (hereinafter simply referred to as a printer) which is an image forming apparatus according to the present embodiment.

  The printer shown in FIG. 2 is provided with four process cartridges 102Y, 102M, 102C, and 102Bk that are detachably attached to the printer main body 100 in the center of the printer main body 100. Each process cartridge 102Y, 102M, 102C, 102Bk contains developers of different colors of yellow (Y), magenta (M), cyan (C), and black (Bk) corresponding to the color separation components of the color image. The configuration is the same except that. Therefore, in the case where the colors are not particularly distinguished, description of Y, M, C, Bk, etc. is omitted after the reference numerals of the respective members.

  Each process cartridge 102 includes a photoconductor 108 that is an image carrier, a charging device 110 that charges the surface of the photoconductor, a developing device 111 that includes a developing roller 111a that carries a developer, and a cleaning device that cleans the surface of the photoconductor. 112 and the like.

  Above each process cartridge 102, an exposure device 103 that exposes the surface of the photoreceptor 108 is provided. The exposure device 103 includes a light source, a polygon mirror, an f-θ lens, a reflection mirror, and the like, and irradiates the surface of each photoreceptor 108 with laser light based on image data.

  A transfer device 130 is disposed below each process cartridge 102. The transfer device 130 includes an intermediate transfer belt 120, four primary transfer rollers 101, a secondary transfer roller 123, a secondary transfer backup roller 122, a cleaning backup roller 133, a tension roller 121, and a belt cleaning device 135. Is provided.

  The intermediate transfer belt 120 is an endless belt and is stretched by a secondary transfer backup roller 122, a cleaning backup roller 133, and a tension roller 121.

  In the present embodiment, the secondary transfer backup roller 122 is driven to rotate by a drive device (not shown), so that the intermediate transfer belt 120 rotates in the direction indicated by the arrow in the drawing. Further, both ends in the axial direction of the tension roller 121 are pressed by a spring to apply tension to the intermediate transfer belt 120.

  Each of the four primary transfer rollers 101 forms a primary transfer nip by sandwiching the intermediate transfer belt 120 with each photoconductor 108. Each primary transfer roller 101 is connected to a single high-voltage power supply (not shown), and a predetermined transfer bias of +400 [V] to +2500 [V] is applied from this high-voltage power supply to form a transfer electric field. To do.

  The secondary transfer roller 123 sandwiches the intermediate transfer belt 120 between the secondary transfer backup roller 122 and forms a secondary transfer nip. Similarly to the primary transfer roller 101, the secondary transfer roller 123 is also connected to a high voltage power source (not shown), and a predetermined transfer bias is applied from the high voltage power source to form a transfer electric field.

  The belt cleaning device 135 has a cleaning blade disposed so as to contact the intermediate transfer belt 120.

  On the other hand, a lower portion of the printer main body 100 is provided with a paper feed tray 104 that stores paper P as a recording medium, a paper feed roller 105 that carries the paper P out of the paper feed tray 104, and the like. Here, the recording medium includes thick paper, postcard, envelope, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, OHP sheet and the like in addition to plain paper. Although not shown, a manual paper feed mechanism may be provided.

  In the printer main body 100, a conveyance path R is disposed for discharging the paper P from the paper feed tray 104 through the secondary transfer nip and out of the apparatus. In the conveyance path R, a registration roller pair 107 as a conveyance unit that conveys the paper P to the secondary transfer nip is disposed upstream of the position of the secondary transfer roller 123 in the paper conveyance direction.

  Further, a fixing device 200 for fixing the unfixed image transferred onto the paper P is disposed downstream of the position of the secondary transfer roller 123 in the paper transport direction.

  Further, a discharge roller pair 109 for discharging the paper P to the outside of the apparatus is provided on the downstream side in the paper conveyance direction of the conveyance path R from the fixing device 200. Further, on the upper surface of the printer main body 100, a paper discharge tray (not shown) for stocking the paper P discharged outside the apparatus is provided.

  Further, a toner mark sensor (TM sensor) 124 disposed opposite to the tension roller 121 via the intermediate transfer belt 120 measures the density of the toner image on the intermediate transfer belt 120 by using a regular reflection type sensor or a diffusion type sensor. Measure the position of the toner image. Then, based on the result measured by the toner mark sensor 124, the image forming conditions are changed at a predetermined timing, and the image density and color matching are adjusted.

The basic operation of the image forming apparatus having the above configuration is as follows.
When the image forming operation is started, each photoconductor 108 in each process cartridge 102 is rotationally driven in a clockwise direction in the drawing by a driving device (not shown). A roller-shaped charging device 110 is pressed against the surface of each photoconductor 108, and the charging device 110 rotates as the photoconductor 108 rotates. Then, a DC voltage or a bias in which an AC voltage is superimposed on the DC voltage is applied to the charging device 110 by a high voltage power source (not shown), so that the surface of the photoconductor 108 is uniformly charged to a predetermined polarity by the charging device 110. .

  The surface of each charged photoconductor 108 is irradiated with writing light from the exposure device 103 to form an electrostatic latent image on the surface of each photoconductor 108. At this time, the image information to be exposed to each photoconductor 108 is single-color image information obtained by separating a desired full-color image into color information of yellow, magenta, cyan, and black. This exposure process is performed by a laser beam scanner or LED using a laser diode.

  Thus, the electrostatic latent image formed on each photoconductor 108 is visualized as a toner image by supplying the toner carried on the developing roller 111a by each developing device 111. (Visualized). In this developing step, a predetermined developing bias is applied to the developing roller 111a of the developing device 111 from a high voltage power source (not shown).

  When the image forming operation is started, the secondary transfer backup roller 122 is rotationally driven in the counterclockwise direction in the drawing, and the intermediate transfer belt 120 is run in the direction indicated by the arrow in the drawing. Then, each primary transfer roller 101 is applied with a predetermined transfer bias controlled by a constant voltage or a constant current having a polarity opposite to the charging polarity of the toner. As a result, a transfer electric field is formed at the primary transfer nip between each primary transfer roller 101 and each photoconductor 108.

  Thereafter, when each color toner image on the photoconductor 108 reaches the primary transfer nip as each photoconductor 108 rotates, the toner image on each photoconductor 108 is generated by the transfer electric field formed in the primary transfer nip. Are sequentially superimposed and transferred onto the intermediate transfer belt 120. In this way, a full-color toner image is carried on the surface of the intermediate transfer belt 120.

  Further, the toner on each photoconductor 108 that could not be transferred to the intermediate transfer belt 120 is removed by the cleaning device 112. Thereafter, the surface of each photoconductor 108 is neutralized by a neutralizing device (not shown), and the surface potential is initialized.

  There is also a cleanerless system in which the developing device 111 collects the transfer residual toner without providing a cleaning device around the photoconductor 108, and the printer of this embodiment employs various known cleaning methods for cleaning the surface of the photoconductor. it can.

  In the lower part of the printer main body 100, the paper feed roller 105 starts to rotate, and the paper P is sent from the paper feed tray 104 to the transport path R. The sheet P sent to the conveyance path R is timed by the registration roller pair 107 and sent to the secondary transfer nip between the secondary transfer roller 123 and the secondary transfer backup roller 122. At this time, a transfer bias having a polarity opposite to the toner charging polarity of the toner image on the intermediate transfer belt 120 is applied to the secondary transfer roller 123, thereby forming a transfer electric field in the secondary transfer nip. Yes.

  Thereafter, when the toner image on the intermediate transfer belt 120 reaches the secondary transfer nip as the intermediate transfer belt 120 rotates, the transfer electric field formed in the secondary transfer nip causes a transfer on the intermediate transfer belt 120. The toner images are collectively transferred onto the paper P.

  At this time, the residual toner on the intermediate transfer belt 120 that could not be transferred onto the paper P is removed by the belt cleaning device 135, and the removed toner is conveyed to a waste toner container (not shown) and collected.

  Thereafter, the paper P is conveyed to the fixing device 200, and the toner image on the paper P is fixed on the paper P by the heat and pressure by the fixing device 200. Then, the paper P is discharged out of the apparatus by a pair of paper discharge rollers 109 and stocked on a paper discharge tray (not shown).

  In this way, a series of image forming processes in the printer according to the present embodiment is completed.

FIG. 3 is a diagram illustrating the configuration of the fixing device 200.
The fixing device 200 includes a pressure roller 201, an endless fixing belt 202, a nip forming member 205, a heat transfer member 203, a reinforcing member 206, a heater 204, a first stay, a second stay (not shown), a sheet-like member (seal member). ), A temperature sensor 207, a pressure contact mechanism, and the like.

  The pressure roller 201 has a diameter of about 20 [mm] to 40 [mm] and has an elastic layer formed on a hollow cored bar. The elastic layer of the pressure roller 201 is made of a material such as foamable silicone rubber, silicone rubber, or fluorine rubber. A thin release layer made of PFA, PTFE or the like may be provided on the surface of the elastic layer.

  The pressure roller 201 is pressed against the fixing belt 202 to form a desired fixing nip N between the pressure roller 201 and the fixing belt 202.

  A driving gear (not shown) is installed at the axial end of the pressure roller 201, and the pressure roller 201 is rotationally driven in the direction of the arrow (clockwise direction) in FIG. Further, a heat source such as a halogen heater may be provided inside the pressure roller 201.

  Next, the fixing belt 202 is a thin and flexible endless belt, and rotates in the arrow direction (counterclockwise direction) in FIG.

  The fixing belt 202 has a base material layer, an elastic layer, and a release layer sequentially laminated from the inner peripheral surface side that is a sliding contact surface with the nip forming member 205, and the total thickness thereof is 500 [μm] or less. Is set to

  The base material layer of the fixing belt 202 has a layer thickness of 30 [μm] to 100 [μm], and is formed of a metal material such as nickel or stainless steel, or a resin material such as polyimide.

  The elastic layer of the fixing belt 202 has a layer thickness of 100 [μm] to 300 [μm], and is formed of a rubber material such as silicone rubber, foamable silicone rubber, or fluororubber.

  By providing an elastic layer on the fixing belt 202, minute irregularities on the surface of the fixing belt 202 in the fixing nip N are not formed, and heat is uniformly transmitted to the toner image on the paper P, thereby suppressing the generation of a scum-skin image.

  The release layer of the fixing belt 202 has a layer thickness of 5 [μm] to 50 [μm]. And PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), PTFE (polytetrafluoroethylene), PI (polyimide), PAI (polyamideimide), PEI (polyetherimide), PES (polyethersulfide), It is made of a material such as PEEK (polyether ketone).

  The diameter of the fixing belt 202 is set to be 15 [mm] to 120 [mm]. In the present embodiment, the diameter of the fixing belt 202 is about 30 [mm].

  On the inner peripheral surface side of the fixing belt 202, a heater 204, a nip forming member 205, a heat transfer member 203, a reinforcing member 206, a first stay, a second stay, a sheet-like member (not shown), and the like are fixed. ing. Note that a halogen heater or a carbon heater can be used as the heater 204.

  The nip forming member 205 is fixed so as to be in sliding contact with the inner peripheral surface of the fixing belt 202, and is pressed against the pressure roller 201 via the fixing belt 202, thereby forming a fixing nip N in which the paper P is conveyed. The

  Further, lubrication with fluorine grease, silicone oil, or the like is provided between the fixing belt 202 and the heat transfer member 203 so that the wear of the fixing belt 202 is reduced even if the heat transfer member 203 and the fixing belt 202 are in sliding contact with each other. The agent is applied.

  The cross-sectional shape of the heat transfer member 203 is a cross-sectional shape obtained by cutting off a part of a circle from the viewpoint of heat transfer efficiency and sliding resistance, thereby reducing the contact area with the fixing belt 202 and sliding resistance. Can be lowered.

  Further, the fixing belt 202 is stretched by a temperature sensor 207 such as a thermistor from the fixing nip N and an edge portion of the heat transfer member 203 on the downstream side in the conveying direction of the fixing nip N (upper portion of the fixing nip N in FIG. 3). Is realized.

  The heat transfer member 203 is heated by the radiant heat of the heater 204 that is supplied with power from the power supply unit of the printer main body 100 and whose output is controlled by a control unit (not shown). The radiant heat heats only a part of the heat transfer member 203 by the reflecting member 210, and the fixing belt 202 contacting the same portion is indirectly heated.

  As a material of the heat transfer member 203, a metal heat conductor (a metal having heat conductivity) such as aluminum, iron, and stainless steel is used, and the thickness of the heat transfer member 203 is set to 0.2 mm or less. By setting, the heating efficiency of the fixing belt 202 can be improved.

  The heat transfer member 203 is close to or in contact with the inner peripheral surface of the fixing belt 202 at a position excluding the fixing nip N, and a concave portion that is formed in a concave shape and has an opening at the position of the fixing nip N. Is provided.

  Here, the gap G (gap at a position excluding the fixing nip N) between the fixing belt 202 and the heat transfer member 203 at normal temperature is set to be greater than 0 [mm] and 2 [mm] or less (0 mm <G ≦ 2 mm). It is preferable.

  As a result, the area in which the heat transfer member 203 and the fixing belt 202 are in sliding contact with each other is suppressed, and acceleration of wear of the fixing belt 202 is suppressed, and the heat transfer member 203 and the fixing belt 202 are too far apart from each other. It can suppress that heating efficiency falls.

  In addition, since the heat transfer member 203 is placed close to the fixing belt 202, the heat transfer member 203 maintains the circular posture of the flexible fixing belt 202 to some extent, so that deterioration due to deformation of the fixing belt 202 is caused. And damage can be reduced.

  Further, in order to reduce the sliding resistance between the heat transfer member 203 and the fixing belt 202, the sliding contact surface of the heat transfer member 203 is formed of a material having a low coefficient of friction with respect to the fixing belt 202, or the inner periphery of the fixing belt 202. A surface layer made of a material containing fluorine may be formed on the surface.

  Further, when a means for uniformly transferring the heat from the heater 204 to the fixing belt 202 and ensuring the running stability of the fixing belt 202 during driving is prepared, the heat transfer member 203 is provided. It is also possible to configure a fixing device that directly heats the fixing belt 202. In that case, since the heat capacity of the heat transfer member 203 is excluded from the heat capacity of the entire fixing device, there is an advantage that it is possible to configure a fixing device with more excellent temperature rise performance and energy saving performance.

  Note that the output control of the heater 204 is performed based on the detection result of the surface temperature of the fixing belt by the temperature sensor 207 such as a thermistor disposed to face the surface of the fixing belt 202. Further, the temperature of the fixing belt 202 (fixing temperature) can be set to a desired temperature by such output control of the heater 204.

  As shown in FIG. 3, the fixing device 200 is provided with a pressing mechanism that presses the pressure roller 201 against the fixing belt 202. This pressure contact mechanism includes a pressure lever 208, a pressure spring 209, and the like.

  The pressure lever 208 is rotatably supported on a side plate (not shown) of the fixing device 200 around a support shaft 208a provided on one end side of the pressure lever 208. The central portion of the pressure lever 208 is in contact with the rotation shaft of the pressure roller 201 that is movably held in a long hole formed in the side plate.

  One end of a pressure spring 209 is connected to the other end side of the pressure lever 208, and the other end of the pressure spring 209 is connected to a holding plate 211 provided in the fixing device 200. With such a configuration, the pressure lever 208 pulled by the pressure spring 209 rotates around the support shaft 208a toward the rotation shaft of the pressure roller 201, and the pressure roller 201 moves toward the fixing belt 202. Will move. As a result, the pressure roller 201 presses the fixing belt 202 to form a desired fixing nip N.

  Hereinafter, the normal operation of the fixing device 200 configured as described above will be briefly described.

  When the power switch of the printer main body 100 is turned on, electric power is supplied to the heater 204, and rotation of the pressure roller 201 in the clockwise direction in FIG. 3 by a driving device (not shown) is started. The drive device is provided with a drive motor as a drive source, a drive gear for transmitting the drive force of the drive motor to the pressure roller 201, and the drive motor is driven by a control unit (not shown). Is controlled. Further, as the pressure roller 201 rotates, the fixing belt 202 is driven to rotate counterclockwise in FIG. 3 by a frictional force generated between the pressure roller 201 and the pressure roller 201.

  Thereafter, the paper P is fed from the paper feed tray 104, and the paper P on which the toner image is transferred at the secondary transfer nip is conveyed in the direction of the arrow in FIG. It enters the fixing nip N between the fixing belt 202 and the pressure roller 201 in the state.

  The sheet P is heated by the fixing belt 202 heated by the heat transfer member 203 that receives the radiant heat from the heater 204 and the pressing force of the nip forming member 205 reinforced by the reinforcing member 206 and the pressure roller 201. A toner image is fixed on the surface of the toner.

  Thereafter, the paper P is sent out from the fixing nip N, discharged to the outside of the apparatus by the paper discharge roller pair 109, and stocked on the paper discharge tray. Thus, a series of fixing processes in the fixing device 200 is completed.

  Next, features of the fixing device 200 provided in the printer according to the present embodiment will be described.

  FIG. 4 is an explanatory diagram of a state in which the fixing device 200 is in a drive stopped state and is not performing a heating operation.

  In the initial state shown in FIG. 4 in which the fixing device 200 is in a drive stop state and in a state where no heating operation is performed, the fixing belt 202 is stretched by the heat transfer member 203 as follows. That is, in the fixing belt rotation direction, the fixing belt 202 is stretched by the heat transfer member 203 from the position facing the temperature sensor 207 through the fixing nip N to the edge portion of the heat transfer member 203 on the downstream side in the sheet conveyance direction. .

  In addition, since a lubricant such as fluorine grease or silicone grease is applied between the fixing belt 202 and the heat transfer member 203, the fixing belt 202 and the heat transfer member 203 are in contact with each other without any gap. This lubricant is used for the purpose of reducing wear between the fixing belt 202, the heat transfer member 203 and the nip forming member 205 during the operation of the fixing device 200.

  Here, in Patent Document 2, in order to acclimatize the grease applied between the fixing belt and the metal pipe (corresponding to the heat transfer member 203 of the present embodiment), the fixing belt is heated and rotated to obtain the grease. Has been disclosed to reduce the driving torque during the printing operation.

  However, in the warm-up operation, when the driving is started from the state in which the fixing device 200 is cold, a highly viscous lubricant at a low temperature is applied to the contact surfaces of the fixing belt 202, the heat transfer member 203, and the nip forming member 205. It spreads evenly. Therefore, a sliding load between the fixing belt 202 and the heat transfer member 203 and a sliding load between the fixing belt 202 and the nip forming member 205 are increased, and a driving torque for rotating the fixing belt 202 is increased.

  Since the viscosity of the lubricant decreases as the temperature rises, the driving torque gradually decreases with time due to driving with heating.

  FIG. 5 is an explanatory diagram when the fixing device 200 starts a warm-up operation from the initial state. FIG. 6 shows an example of a control flowchart of a normal warm-up operation.

  When the fixing device 200 starts the warm-up operation from the initial state (S1), first, the heating operation by the heater 204 is performed in the drive stopped state (S2). Temperature control during heating is performed by the temperature sensor 207, the set temperature is set to 50 [° C.], and the output of the heater 204 is limited to 50 [%] of the maximum output value (see FIG. 10). And the damage of the member by it is prevented.

  Note that the output of the heater 204 is not limited to 50 [%] of the maximum output value, and may be 80 [%] or less of the maximum output value. In addition, intermittent output is performed at the maximum output value so that the total heater output per unit time is 80 [%] or less, preferably 50 [%] or less when the maximum output value is continuously output. Thus, the output of the heater 24 may be limited (see FIG. 9).

  By the heating operation, the fixing belt 202 that contacts the heat transfer member 203 in the region A shown in FIG. 5 in the same region is indirectly heated by the heat of the heater 204. Then, it is determined whether the temperature detected by the temperature sensor 207 facing the surface of the fixing belt 202 within the range of the region A in the fixing belt rotation direction is 50 [° C.] or more (S3). Then, when the temperature detected by the temperature sensor 207 reaches 50 [° C.] or higher (Yes in S3), the heating operation in the stopped state is terminated.

  In the heating operation in the stop state, the set temperature, the condition for finishing the heating, and the limit value of the maximum output of the heater 204 are not limited to the above conditions, but are combined conditions such as the heat resistance temperature of the fixing belt 202, the heater output, and the environmental temperature Can be set as appropriate.

  In the normal warm-up operation, after the heating operation in the drive stop state shown in FIG. 5 is completed, normal drive is started (S4). The normal drive is a state in which the heating operation and the drive are performed in parallel, and is a drive state that is performed until the start of printing or the shift to the energy saving standby state.

  FIG. 7 is an explanatory diagram in a state where the pressure roller 201 is driven for a predetermined time while the heating operation is continued.

  As shown in FIG. 7, while the heating operation by the heater 204 is continued, the pressure roller 201 is driven for a certain period of time, whereby the fixing belt 202 is driven to rotate and heated in the driving stop state. Is stopped at the fixing nip N. At this time, the rotation speed of the pressure roller 201 is set to 60 [mm / sec], and the pressure roller 201 is driven for a time sufficient to rotate the fixing belt 202 by 1/4. The output of the heater 204 may be 80% or less of the maximum output value.

  By continuing the heating operation while the pressure roller 201 is being driven (while the fixing belt 202 is rotating), it is possible to reduce the drive torque while shortening the warm-up time. However, the pressure roller 201 is driven without the heating operation. Even if the fixing belt 202 is rotated, the effect of torque reduction can be obtained.

  Note that the control of the operation described with reference to FIG. The rotation speed and driving time of the pressure roller 201 are not limited to those described above. That is, it can be set as appropriate depending on the positional relationship between the heating portion of the heat transfer member 203 (fixing belt 202) by the heater 204 and the fixing nip N. For example, the rotation speed of the pressure roller 201 may be slower than the maximum rotation speed at which the pressure roller 201 can rotate, and the driving time may be within one rotation of the fixing belt 202.

  Moreover, since the drive load at the time of a rotation start can be reduced, so that the rotational speed of the pressure roller 201 becomes slow, it is not limited to 60 [mm / sec], It can set freely in the range within 100 [mm / sec]. .

  In the fixing device 200 of the present embodiment, the fixing belt 202 is configured to rotate following the rotation of the pressure roller 201, but is not limited thereto. A similar effect can be obtained by separately providing a driving means for rotationally driving the fixing belt 202 to drive either or both of the pressure roller 201 and the fixing belt 202.

  FIG. 8 is an explanatory diagram in a state where the region A of the heated fixing belt 202 is stopped at a position in contact with the fixing nip N. FIG.

  As shown in FIG. 8, the region A of the heated fixing belt 202 stops at a position in contact with the fixing nip N. By maintaining this driving stop state for 3 seconds, heat is transferred from the fixing belt 202 to the pressure roller 201 and the nip forming member 205 in the region C in the drawing at the fixing nip N. As a result, the lubricant present in the fixing nip N is warmed, the viscosity of the lubricant can be lowered, and the sliding load caused by the lubricant can be reduced.

  Further, while the driving stop state is maintained for 3 seconds, the heating operation by the heater 204 is also performed in parallel, and the fixing belt 202 that contacts the heat transfer member 203 in the region B shown in FIG. It is indirectly heated by the heat of the heater 204. At this time, the output of the heater 204 may be 80% or less of the maximum output value.

  Note that the control of the operation described with reference to FIG. Further, the stop time in the drive stop state is not limited to 3 seconds, and can be set as appropriate according to the thermal conductivity of the fixing belt 202, the nip forming member 205, the pressure roller 201, etc., and may be 0.1 seconds or longer.

  FIG. 1 shows an example of a control flowchart of the warm-up operation.

  When the fixing device 200 starts the warm-up operation from the initial state (S1), first, the heating operation by the heater 204 is performed in the drive stopped state (S2). Temperature control at the time of heating is performed by the temperature sensor 207, the set temperature is set to 50 [° C.], and the maximum output of the heater 204 is limited to 50 [%]. It is preventing.

  By the heating operation, the fixing belt 202 that contacts the heat transfer member 203 in the region A shown in FIG. 5 in the same region is indirectly heated by the heat of the heater 204. Then, it is determined whether the temperature detected by the temperature sensor 207 facing the surface of the fixing belt 202 within the range of the region A in the fixing belt rotation direction is 50 [° C.] or more (S3). Then, when the temperature detected by the temperature sensor 207 reaches 50 [° C.] or higher (Yes in S3), the heating operation in the stopped state is terminated.

  Next, the control A is executed. That is, while the heating operation by the heater 204 is continued, the pressure roller 201 is driven for a certain period of time (0.4 seconds in this case), whereby the fixing belt 202 is driven to rotate and heated in a driving stopped state. Is stopped at the fixing nip N (S4). As described above, the fixing roller 202 may be rotated by driving the pressure roller 201 without the heating operation by the heater 204.

  Then, the control B is executed. In other words, the drive stop state in which the region A of the heated fixing belt 202 is stopped at a position in contact with the fixing nip N is maintained for 3 seconds, and during this time, the heating operation by the heater 204 is also performed in parallel (S5). As a result, in the fixing nip N, heat is transferred from the fixing belt 202 to the pressure roller 201 and the nip forming member 205, and the lubricant present in the fixing nip N is indirectly warmed to reduce the viscosity of the lubricant and lubricate. The sliding load caused by the agent can be reduced. Further, the fixing belt 202 that is in contact with the heat transfer member 203 in the region B of the fixing belt 202 shown in FIG. 5 is indirectly heated by the heat of the heater 204.

  Thereafter, it is determined whether each of the control A and the control B has been executed four times (S6). If the control A and the control B are not executed four times (NO in S6), the control A and the control B are repeated again. At this time, the control A may be performed so that the region B of the fixing belt 202 heated in the driving stop state of the control B is stopped at the fixing nip N. Thereby, the warm-up time can be shortened.

  On the other hand, if the control A and the control B are executed four times (YES in S6), after the heating operation in the drive stop state in the control B is finished, normal driving is started (S7), and the warm-up operation control is performed. Exit.

  As shown in FIG. 1, the above-described control A and control B are sequentially executed as a series of operations, and are executed four times each. By repeatedly executing the control A and the control B, the temperature of the fixing nip N increases with the number of executions of the control A and the control B, and is present in the fixing nip N by four repeated executions. The lubricant can be heated sufficiently.

  Further, the temperature of the heat transfer member 203 that is directly heated from the heater 204 also increases with the number of executions of the control A and the control B, and the lubricant present on the surface of the heat transfer member 203 can be sufficiently heated. it can.

  In addition, the normal driving is performed after each of the control A and the control B is executed four times. However, since the viscosity of the sufficiently heated lubricant is reduced, the driving torque of the fixing device 200 is reduced. ing.

  Note that the number of repetitions of the series of control of the control A and the control B is not limited to four, and can be appropriately set according to the viscosity of the lubricant, its thermal characteristics, and the driving distance in the control A. A series of control with B may be performed at least once.

  A temperature detection sensor that detects the temperature of the pressure roller 201 may be provided separately. When the temperature detection result when the rotation of the pressure roller 201 by the temperature detection sensor is not more than a predetermined temperature (for example, 50 [° C.] or less), at least one series of control A and control B is performed. It may be performed more than once. Even in this case, the viscosity of the lubricant can be reduced, and the sliding load caused by the lubricant present in the fixing nip N can be reduced.

  The effect obtained by limiting the output of the heater 204 when the heating operation is performed in parallel in the control A and the control B will be described with reference to FIG.

  FIG. 9A is a graph when the heater output is not limited, and FIG. 9B is a graph when the heater output is limited. By limiting the heater output as shown in FIG. 9B, the temperature increase gradient [° C./sec] of the fixing belt 202 can be made smaller than that in FIG. 9A. When heating is performed in the drive stopped state, only a part of the fixing belt 202 is heated, and the fixing belt temperature excessively increases, exceeds the heat resistance temperature of the fixing belt 202, and may be damaged.

  Therefore, rather than performing the heating operation without limiting the heater output as shown in FIG. 9A, the heater output per unit time is limited as shown in FIG. It is possible to safely perform the heating operation in the drive stop state while suppressing breakage.

What has been described above is merely an example, and the present invention has a specific effect for each of the following modes.
(Aspect A)
A fixing belt such as a rotatable endless fixing belt 202 having an inner peripheral surface coated with a lubricant, a pressure roller such as a rotatable pressure roller 201 in contact with the outer peripheral surface of the fixing belt, and a fixing belt; A driving unit that rotationally drives at least one of the pressure roller, and a nip forming member such as a nip forming member 205 that is disposed on the inner peripheral side of the fixing belt and contacts the pressure roller via the fixing belt to form a fixing nip. In a fixing device such as a fixing device 200 provided with a heating means such as a heater 204 for heating a portion other than the fixing nip of the fixing belt, heating of the fixing belt by the heating means is performed for a predetermined time while the fixing belt is stopped. The first control for controlling at least the heating means to perform and after the execution of the first control, the fixing belt is rotated for a predetermined time to determine the heated portion of the fixing belt. After reaching the nip, after the execution of the second control such as the control A for controlling at least the driving means so as to stop the rotation of the fixing belt and the second control, the rotation stop state of the fixing belt is maintained for a predetermined time. And a control unit such as a control unit capable of executing at least a third control such as a control B for controlling the driving unit, and before feeding a recording medium such as paper P into the fixing nip, a fixing belt is provided. After the first control is executed during the warm-up operation for raising the temperature, a series of control of the second control and the third control is performed at least once. According to this, as described in the above embodiment, it is possible to suppress the drive unit from being broken due to a high load being continuously applied to the drive unit during the warm-up operation.
(Aspect B)
In (Aspect A), in the second control, when the fixing belt is rotated, the fixing belt is heated by the heating unit. According to this, as described in the above embodiment, it is possible to reduce the drive torque while shortening the warm-up time.
(Aspect C)
In (Aspect A) or (Aspect B), in the third control, the fixing belt is heated by the heating means while the rotation stop state of the fixing belt is maintained for a predetermined time. According to this, as described in the above embodiment, the warm-up time can be shortened.
(Aspect D)
In (Aspect B) or (Aspect C), it has fixing belt temperature detection means such as a temperature sensor 207 for detecting the temperature of the fixing belt, and at least one of the second control and the third control, When the fixing belt is heated by the heating means, the control means controls the heating means so that the detection result of the fixing belt temperature detecting means is lower than a preset fixing temperature. According to this, as explained about the above-mentioned embodiment, excessive heating and the damage of the member by it can be controlled.
(Aspect E)
In (Aspect D), when the fixing belt is heated by the heating unit in at least one of the second control and the third control, the output of the heating unit is set to 80% or less of the maximum output value. To do. According to this, as explained about the above-mentioned embodiment, excessive heating and the damage of the member by it can be controlled.
(Aspect F)
In (Aspect A), (Aspect B), (Aspect C), (Aspect D) or (Aspect E), the driving means rotates the pressure roller and is driven by the rotation of the pressure roller. Thus, a configuration in which the fixing belt is rotated can be suitably employed.
(Aspect G)
In (Aspect F), the rotation speed of the pressure roller in the second control is slower than the maximum rotation speed at which the pressure roller can rotate. According to this, as described in the above embodiment, the drive load at the start of rotation can be reduced as the rotation speed of the pressure roller is decreased.
(Aspect H)
In (Aspect A), (Aspect B), (Aspect C), (Aspect D), (Aspect E), (Aspect F) or (Aspect G), the predetermined time in the second control is the fixing. A time corresponding to one revolution of the belt may be used.
(Aspect I)
In (Aspect A), (Aspect B), (Aspect C), (Aspect D), (Aspect E), (Aspect F), (Aspect G) or (Aspect H), the predetermined time in the third control Is 0.1 seconds or more. According to this, as described in the above embodiment, the lubricant present in the fixing nip is warmed, the viscosity of the lubricant is lowered, and the sliding load caused by the lubricant present in the fixing nip can be reduced. .
(Aspect J)
In (Aspect A), (Aspect B), (Aspect C), (Aspect D), (Aspect E), (Aspect F), (Aspect G), (Aspect H) or (Aspect I), the pressure roller Pressure roller temperature detection means for detecting the temperature of the pressure roller, and when the temperature detection result by the pressure roller temperature detection means in a state where the rotation of the pressure roller is stopped is equal to or lower than a predetermined temperature, A series of control of the second control and the third control is performed at least once. According to this, as described in the above embodiment, the viscosity of the lubricant can be lowered, and the sliding load caused by the lubricant present in the fixing nip can be reduced.
(Aspect K)
An image carrier such as the photoconductor 108, a toner image forming unit that forms a toner image on the image carrier, a transfer unit such as a transfer device 130 that transfers the toner image from the image carrier onto a recording medium, and a recording In an image forming apparatus including a fixing unit such as a fixing device 200 that fixes a toner image transferred onto a medium to a recording medium, the fixing unit includes (Aspect A), (Aspect B), (Aspect C), The fixing device of (Aspect D), (Aspect E), (Aspect F), (Aspect G), (Aspect H), (Aspect I) or (Aspect J) is used. According to this, as described in the above embodiment, it is possible to suppress the drive unit from being damaged due to a high load being continuously applied to the drive unit during the warm-up operation, and to perform good image formation.

DESCRIPTION OF SYMBOLS 100 Printer body 101 Primary transfer roller 102 Process cartridge 103 Exposure device 104 Paper feed tray 105 Paper feed roller 107 Registration roller pair 108 Photoreceptor 109 Paper discharge roller pair 110 Charging device 111 Developing device 111a Developing roller 112 Cleaning device 120 Intermediate transfer belt 121 Tension roller 122 Secondary transfer backup roller 123 Secondary transfer roller 124 Toner mark sensor 130 Transfer device 133 Cleaning backup roller 135 Belt cleaning device 200 Fixing device 201 Pressure roller 202 Fixing belt 203 Heat transfer member 204 Heater 205 Nip forming member 206 Reinforcement Member 207 temperature sensor 208 pressure lever 208a support shaft 209 pressure spring 210 reflecting member 211 holding plate

JP 2004-286929 A JP 2011-191520 A

Claims (11)

A rotatable endless fixing belt having a lubricant applied to the inner peripheral surface;
A rotatable pressure roller in contact with the outer peripheral surface of the fixing belt;
Drive means for rotationally driving at least one of the fixing belt and the pressure roller;
A nip forming member that is disposed on the inner peripheral side of the fixing belt and forms a fixing nip by contacting the pressure roller via the fixing belt;
In a fixing device comprising a heating means for heating a portion other than the fixing nip of the fixing belt,
A first control for controlling at least the heating unit so that the heating of the fixing belt by the heating unit is performed for a predetermined time while the fixing belt is stopped;
After the execution of the first control, the fixing belt is rotated for a predetermined time, the heated portion of the fixing belt reaches the fixing nip, and at least the driving unit is controlled to stop the rotation of the fixing belt. Said second control to
After the execution of the second control, it has control means capable of executing at least a third control for controlling the drive means so as to maintain the rotation stop state of the fixing belt for a predetermined time,
After executing the first control in the warm-up operation for raising the temperature of the fixing belt before feeding the recording medium to the fixing nip, a series of control of the second control and the third control is performed at least once or more A fixing device characterized by performing. The fixing device according to claim 1.
In the second control, when the fixing belt is rotated, the fixing belt is heated by the heating unit. The fixing device according to claim 1 or 2,
In the third control, the fixing device heats the fixing belt by the heating means while maintaining the rotation stop state of the fixing belt for a certain time. The fixing device according to claim 2 or 3,
A fixing belt temperature detecting means for detecting the temperature of the fixing belt;
When at least one of the second control and the third control heats the fixing belt by the heating unit, the detection result of the fixing belt temperature detection unit is a temperature lower than a preset fixing temperature. The fixing device is characterized in that the control means controls the heating means. The fixing device according to claim 4.
When at least one of the second control and the third control, the fixing belt is heated by the heating means, the output of the heating means is set to 80 [%] or less of the maximum output value. Fixing device to do. The fixing device according to claim 1, 2, 3, 4 or 5.
The fixing device is characterized in that the driving means rotates the pressure roller, and the fixing belt is rotated by the rotation of the pressure roller. The fixing device according to claim 6.
The fixing device according to claim 2, wherein a rotation speed of the pressure roller in the second control is lower than a maximum rotation speed at which the pressure roller can rotate. The fixing device according to claim 1, 2, 3, 4, 5, 6 or 7.
The fixing device according to claim 2, wherein the predetermined time in the second control corresponds to within one rotation of the fixing belt. The fixing device according to claim 1, 2, 3, 4, 5, 6, 7 or 8.
The fixing device, wherein the predetermined time in the third control is 0.1 second or more. The fixing device according to claim 1, 2, 3, 4, 5, 6, 7, 8, or 9.
Having pressure roller temperature detecting means for detecting the temperature of the pressure roller;
When the temperature detection result by the pressure roller temperature detecting means in a state where the rotation of the pressure roller is stopped is equal to or lower than a predetermined temperature, a series of control of the second control and the third control is performed at least once. A fixing device characterized by the above. An image carrier;
Toner image forming means for forming a toner image on the image carrier;
Transfer means for transferring the toner image from the image carrier onto a recording medium;
An image forming apparatus comprising: a fixing unit that fixes the toner image transferred onto the recording medium to the recording medium;
An image forming apparatus using the fixing device according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 as the fixing unit.

Images