JP2001272876A - Fixing device and image forming apparatus provided with the fixing device - Google Patents

Abstract

(57) Abstract: The present invention has an inexpensive configuration, maintains the surface temperature of a fixing body and a pressing body at a predetermined temperature even after a long standby state, and generates paper wrinkles and low-temperature offset. The present invention provides a fixing device capable of preventing an image and obtaining a good fixed image, and an image forming apparatus including the fixing device. SOLUTION: During standby for fixing, rotation and stop of a fixing roller 10a and a pressure roller 10b are intermittently rotated or stopped in two minutes and three minutes, and a control device 40 controls the fixing roller 10a and the pressure during standby for fixing. The main heater 37 and the sub-heater 38 are alternately turned on for 2 seconds and 6 seconds when the roller 10b rotates, only the sub-heater 38 is turned on when the fixing roller 10a and the pressure roller 10b are stopped during fixing standby, and the fixing roller 10a is turned on during fixing standby. Set to maintain the surface temperature at the target temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for fixing a non-fixed image to the recording medium by heating and pressing a recording medium holding an unfixed image by nipping and transporting the recording medium between a fixing member and a pressing member. The present invention relates to an image forming apparatus including the fixing device.

[0002]

2. Description of the Related Art Many conventional image forming apparatuses such as electrophotographic copying machines and printers use a heat fixing type fixing device as fixing means.

Such a fixing device is composed of a fixing roller as a fixing member in which a heat-resistant release layer is coated on the surface of an aluminum or iron core, and a pressing member with a heat-resistant elastic layer formed around a core such as stainless steel. And a pressure roller, and the fixing roller is heated by a halogen heater serving as a heating unit disposed in a core metal of the fixing roller.

In such a fixing device, a pressure roller is pressed against the fixing roller by a spring or the like to form a nip, and a recording material as a recording medium carrying an unfixed toner image is formed by the nip. The toner image is fixed on the recording material by being nip-conveyed, heated and pressed.

As such a fixing device, a fixing device having a halogen heater only in the fixing roller and a fixing device having a halogen heater in both the fixing roller and the pressure roller are generally known. The fixing device having the halogen heater only has a simpler configuration, and is advantageous in terms of downsizing and low cost of the fixing device.

[0006]

However, in such a fixing device, when the temperature distribution on the surface of the fixing roller is adjusted by a single halogen heater having a uniform light distribution in the axial direction of the fixing roller, small-size paper is used. It was difficult to suppress the temperature rise in the non-sheet passing portion when the sheet was continuously passed through the nip. It is necessary to apply heat to the entire roller longitudinal direction to make the longitudinal temperature distribution on the fixing roller uniform when passing the maximum size paper. In order to suppress the temperature rise in the non-sheet passing area when the sheet is not passed, it is necessary to not apply heat to the non-sheet passing section, and contradiction will occur if these are satisfied at the same time. I had to do it.

Therefore, as a means for solving this contradiction,
A method has been proposed in which two halogen heaters having different light distributions in the axial direction of the fixing roller are provided, and each heater is turned on by time division control. In this method, a halogen heater that mainly heats the central portion in the axial direction and a halogen heater that heats both end portions in the axial direction are provided in the fixing roller, and each heater is driven and controlled by a CPU. Each heater can be turned on alternately. Then, independent control of each heater is performed so as to obtain the optimal temperature distribution in the axial direction according to the size of the paper to be passed.

However, in the case of a fixing device having a halogen heater only in the fixing roller, since the pressing roller does not have a heating source, in fixing, the heat of the fixing roller is applied to the pressing roller rather than to the unfixed image. And the problem of low temperature offset occurs.

In order to solve this problem, if the fixing roller temperature during standby is set to a high temperature, the fixing roller has a short life due to high temperature, so that a standby state in which no fixing operation is performed (fixing standby state). At
By intermittently repeating the rotation or stop of the fixing roller and the pressure roller, a method of transmitting the heat of the fixing roller to the pressure roller and maintaining the surface temperature of the pressure roller to some extent may be adopted.

However, unevenness in the temperature distribution in the longitudinal direction (axial direction) of the fixing roller and the pressure roller occurs due to the difference in the heat radiation condition of the fixing roller when the fixing roller and the pressure roller rotate and when the rotation is stopped. When the recording material nip is passed after the standby state continues for a long time, problems such as paper wrinkles and low-temperature offset at the ends occur.

Accordingly, the present invention provides an inexpensive configuration that maintains the surface temperatures of the fixing body and the pressing body at a predetermined temperature even after a long standby state, thereby preventing paper wrinkles and low-temperature offset from occurring. It is an object of the present invention to provide a fixing device capable of obtaining a stable fixed image and an image forming apparatus including the fixing device.

[0012]

According to the present application, the object is to provide a fixing member and a pressing member which are pressed against each other and are rotatably disposed, a heating means for heating the fixing member, and a fixing device. A fixing unit temperature detecting unit that detects a surface temperature; a control unit that controls heating of a heating unit so that the fixing unit surface temperature detected by the fixing unit temperature detecting unit becomes a target temperature; and a fixing unit and a pressing unit. A fixing device for fixing the unfixed image on the recording medium by heating and pressurizing the recording medium carrying the unfixed image by nipping and transporting the recording medium holding the unfixed image between the fixing body and the pressing body. The heating means includes a first heating element and a second heating element which are disposed in the fixing body and have different light distributions in the axial direction of the fixing body, and the first heating element is disposed in the central portion in the axial direction. The second heating element having a light peak; In a fixing device having a light distribution peak on the axial end side, the control unit turns on the first heating element and the second heating element alternately at a predetermined lighting time ratio. During standby, the fixing member and the pressure member are intermittently rotated or stopped every predetermined time, and the control means controls the first heating element and the first heating member at a first lighting time ratio when the fixing member and the pressure member rotate during the fixing standby. The second heating element is turned on, and the first heating element and the second heating element are set to be turned on at the second lighting time ratio when the fixing body and the pressure body are stopped during the fixing standby, and the first lighting time ratio is The lighting time of the first heating element is set longer than the lighting time of the first heating element according to the second lighting time ratio, and the lighting time of the second heating element is set shorter than the lighting time of the second heating element according to the second lighting time ratio. This is achieved by the first invention.

Further, according to the present invention, the above object is achieved in the first aspect of the present invention, wherein the control means controls the fixing member surface temperature during rotation of the fixing member and the pressure member during standby for fixing to be higher than when stopped. This is also achieved by the second invention in which the target temperature is set.

Further, according to the present application, the object is to provide a fixing member and a pressurizing member which are pressed against each other and are rotatably arranged, a heating means for heating the fixing member, and a surface temperature of the fixing member. Fixing unit temperature detecting unit, a pressing unit temperature detecting unit for detecting the surface temperature of the pressing unit, and heating the heating unit so that the fixing unit surface temperature detected by the fixing unit temperature detecting unit becomes the target temperature. A control unit for controlling the fixing unit and a driving unit for driving the fixing unit and the pressing unit to rotate. The recording medium holding the unfixed image is nipped and conveyed by the fixing unit and the pressing unit, and heated and pressurized. A fixing device for fixing an image on the recording medium, wherein the heating unit includes a first heating element and a second heating element that are disposed in the fixing body and have different light distributions in the axial direction of the fixing body. The first heating element is The second heating element has a light distribution peak at the axial end portion side, and the control means alternately lights the first heating element and the second heating element at a predetermined lighting time ratio. In the fixing device, the driving unit rotates the fixing unit and the pressing body when the surface temperature of the pressing body detected by the pressing body temperature detection unit is equal to or lower than a predetermined temperature during fixing standby. The control unit turns on the first heating element and the second heating element at the first lighting time ratio when the fixing body and the pressing body rotate during the fixing standby, and stops the fixing body and the pressing body during the fixing standby. Sometimes, the first heating element and the second heating element are set to be turned on at the second lighting time ratio, and the first lighting time ratio is the lighting time of the first heating element according to the second lighting time ratio. The second firing time is longer than the time and the lighting time of the second heating element is based on the second lighting time ratio. Also achieved by a third aspect of the present invention that is set to be shorter than the lighting time of the body.

According to the present application, the above object is achieved in the third aspect of the present invention, wherein the control means controls the fixing member surface temperature during rotation of the fixing member and the pressure member during fixing standby to be higher than at the time of stop. This is also achieved by the fourth invention in which the target temperature is set.

Further, according to the present application, the above object is to provide an image forming apparatus for recording an image formed by a series of image forming processes on a recording medium, which is provided with a fixing device of the first invention. The invention is also achieved by the invention of (1).

According to the present invention, the above object is achieved in the fifth aspect of the present invention, wherein the control means controls the fixing body surface temperature during rotation of the fixing body and the pressure body during fixing standby to be higher than at the time of stopping. This is also achieved by the sixth invention in which the target temperature is set.

Further, according to the present application, an object of the present invention is to provide an image forming apparatus for recording an image formed by a series of image forming processes on a recording medium, comprising a fixing device according to the third invention. The invention is also achieved by the invention of (1).

According to the present invention, the above object is achieved in the seventh aspect of the present invention, wherein the control means controls the fixing member so that the surface temperature of the fixing member during rotation of the fixing member and the pressure member during standby for fixing is higher than when the fixing member is stopped. This is also achieved by the eighth invention in which the target temperature is set.

That is, in the first invention according to the present application, heat of the surface of the fixing body is transmitted to the surface of the pressing body by rotation of the fixing body and the pressing body during the fixing standby state, and The heating unit is heated while the heating unit balances the heat generation in the axial direction of the fixing body of the first heating element and the second heating element during rotation and stoppage of the fixing body and the pressure body during standby for fixing. Heat the fixing body.

According to the second aspect of the present invention, the heat of the surface of the fixing member is transmitted to the surface of the pressing member by the rotation of the fixing member and the pressing member during standby for fixing, and the pressure of the pressing member is reduced. The heating unit is heated while the heating unit balances the heat generation in the axial direction of the fixing body of the first heating element and the second heating element during rotation and stoppage of the fixing body and the pressure body during standby for fixing. Heat the fixing body.

Further, in the third invention according to the present application, the heat of the surface of the fixing body is transmitted to the surface of the pressing body by rotation of the fixing body and the pressing body during the fixing standby, so that the pressing is performed. The body is heated and maintained at a predetermined temperature, and the balance of heat generation in the axial direction of the first heating element and the second heating element during rotation and stoppage of the fixing body and the pressurizing body during fixing standby. The heating means heats the fixing body while trying.

According to the fourth aspect of the present invention, the heat of the surface of the fixing member is transmitted to the surface of the pressing member by rotation of the fixing member and the pressing member during the fixing standby state, so that the pressure is reduced. The body is heated and maintained at a predetermined temperature, and the balance of heat generation in the axial direction of the first heating element and the second heating element during rotation and stoppage of the fixing body and the pressurizing body during fixing standby. The heating means heats the fixing body while trying.

Further, in the fifth invention according to the present application, the heat of the surface of the fixing member is transmitted to the surface of the pressing member by rotation of the fixing member and the pressing member during the fixing standby, so that the pressure The heating unit is heated while the heating unit balances the heat generation in the axial direction of the fixing body of the first heating element and the second heating element during rotation and stoppage of the fixing body and the pressure body during standby for fixing. Heat the fixing body.

In the sixth invention according to the present application, heat of the surface of the fixing member is transmitted to the surface of the pressing member by rotation of the fixing member and the pressing member during standby for fixing, so that the pressure The heating unit is heated while the heating unit balances the heat generation in the axial direction of the fixing body of the first heating element and the second heating element during rotation and stoppage of the fixing body and the pressure body during standby for fixing. Heat the fixing body.

Further, in the seventh invention according to the present application, the heat of the surface of the fixing member is transmitted to the surface of the pressing member by the rotation of the fixing member and the pressing member during the fixing standby, so that the pressing The body is heated and maintained at a predetermined temperature, and the balance of heat generation in the axial direction of the first heating element and the second heating element during rotation and stoppage of the fixing body and the pressurizing body during fixing standby. The heating means heats the fixing body while trying.

According to the eighth aspect of the present invention, the heat of the surface of the fixing member is transmitted to the surface of the pressing member by the rotation of the fixing member and the pressing member during the fixing standby state, so that the pressure is reduced. The body is heated and maintained at a predetermined temperature, and the balance of heat generation in the axial direction of the first heating element and the second heating element during rotation and stoppage of the fixing body and the pressurizing body during fixing standby. The heating means heats the fixing body while trying.

[0028]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

(First Embodiment) First, a first embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing a schematic configuration of a digital four-color full-color image forming apparatus as an example of an image forming apparatus using a fixing device according to the present invention.

The image forming apparatus shown in FIG. 1 has a digital color image printer unit (hereinafter simply referred to as "printer unit") I provided at the lower part of the apparatus main body and a digital color image reader provided at the upper part of the apparatus main body. (Hereinafter simply referred to as a “reader unit”) II, for example, based on an image of the document D read by the reader unit II.
Thus, an image is formed on the recording material P.

Next, the configuration of the printer unit I and then the configuration of the reader unit II will be briefly described. The printer section I has a photosensitive drum 1 as an image carrier that is driven to rotate in the direction of arrow R1. Around the photosensitive drum 1, a primary charger (charging means) 2, an exposure means 3,
A developing device (developing means) 4, a transfer device 5, a cleaning device 6, a pre-exposure lamp 7, and the like are arranged. Below the transfer device 5, that is, in the lower half of the printer unit I, a paper feed / conveyance unit 8 for the recording material P is disposed. Further, above the transfer device 5, a separating unit 9 is provided. On the downstream side (downstream side in the transport direction of the recording material P), a fixing device 10 as a fixing device and a paper discharge unit 11 are arranged.

The photosensitive drum 1 has a drum-shaped base 1a made of aluminum and a photosensitive member 1b of OPC (organic optical semiconductor) covering the back side thereof, and is driven in a predetermined direction in the direction of arrow R1 by driving means (not shown). Process speed (peripheral speed)
It is configured to be driven to rotate. The photosensitive drum 1 will be described later in detail.

The primary charger 2 includes a shield 2a having an opening at a portion facing the photosensitive drum 1, and a discharge wire 2b disposed inside the shield 2a in parallel with the bus of the photosensitive drum 1.
And a grid 2c disposed at the opening of the shield 2a to regulate the charging potential. or,
A charging bias is applied to the primary charger 2 by a power supply (not shown), whereby the surface of the photosensitive drum 1 is uniformly charged to a predetermined polarity and a predetermined potential.

Exposure means 3 includes a laser output section (not shown) for emitting a laser beam based on an image signal from a reader section II described later, and a polygon mirror 3 for reflecting the laser beam.
a, a lens 3b, and a mirror 3c. The exposure means 3 is configured to irradiate the surface of the photosensitive drum 1 with the laser beam to expose the photosensitive drum 1 and remove an electric charge of an exposed portion to form an electrostatic latent image. In the present embodiment, the electrostatic latent image formed on the surface of the photosensitive drum 1 is separated into four colors of yellow, cyan, magenta, and black based on the image of the original, and the electrostatic latent image corresponding to each color is separated. Images are sequentially formed.

The developing device 4 includes four developing units in order from the upstream side along the rotation direction of the photosensitive drum 1 (the direction of arrow R1), that is, each color of yellow, magenta, cyan, and black, each of which is made of resin. Developing devices 4Y, 4C, 4M, and 4Bk containing the toner (developer). Each of the developing units 4Y, 4C, 4M, and 4Bk has a developing sleeve 4a for attaching toner to an electrostatic latent image formed on the surface of the photosensitive drum 1, and has a predetermined color used for developing the electrostatic latent image. The developing unit is alternatively arranged at a developing position close to the surface of the photosensitive drum 1 by the eccentric cam 4b, and the toner is attached to the electrostatic latent image via the developing sleeve 4a, and a toner image (visible image) Image). The three color developing units other than the developing unit used for the development are retracted from the developing position.

The transfer device 5 includes a transfer drum (recording material carrier) 5a having a recording material P on its surface, a transfer charger 5b for transferring the toner image on the photosensitive drum 1 to the recording material P, and a recording material P.
Charger 5c for attracting the toner to the transfer drum 5a, a suction roller 5d opposed thereto, an inner charger 5e, and an outer charger 5f, and the transfer is rotatably driven in the direction of arrow R5. A recording material carrying sheet 5g composed of a dielectric pair is integrally stretched in a cylindrical shape in a peripheral opening area of the drum 5a. As the recording material supporting sheet 5g, a dielectric sheet such as a polycarbonate film is used. Further, the transfer device 5 is configured to adsorb and carry the recording material P on the surface of the transfer drum 5a.

The cleaning device 6 includes a cleaning blade 6a for scraping off residual toner remaining on the surface of the photosensitive drum 1 without being transferred to the recording material P, and a cleaning container 6b for collecting the scraped toner.

The pre-exposure lamp 7 is disposed adjacent to the upstream side of the primary charger 2 and removes unnecessary charges on the surface of the photosensitive drum 1 cleaned by the cleaner 6.

The paper feeder 8 is provided with recording materials P of different sizes.
Paper feed cassette 8a for stacking and storing paper, a paper feed roller 8b for feeding the recording material P in the paper feed cassette 8a, a number of transport rollers, a registration roller 8c, and the like, and a recording material of a predetermined size. P is supplied to the transfer drum 5a.

The separating means 9 is provided for the recording material P after the transfer of the toner image.
Charger 9a for separating the toner from the transfer drum 5a,
It has a separation claw 9b and a separation push-up roller 9c.

The fixing device 10 includes a fixing roller 10 as a fixing member.
a main heater 3 which is a halogen heater and is a first heating element disposed inside the fixing roller 10a and serving as a heating means.
7, the sub-heater 38 as the second heating element, and the fixing roller 10
and a pressure roller 10b, which is a pressure member, which is disposed below the recording medium P and presses the recording material P against the fixing roller 10a.

The paper discharge unit 11 includes a conveyance path switching guide 11 a and a discharge roller 11 disposed downstream of the fixing device 10.
b, a paper discharge tray 11c and the like. Further, below the conveyance path switching guide 11a, a conveyance vertical path 11d, a reversing path 11e, a stacking member 11f, an intermediate tray 11g, and a conveyance roller for forming an image on both sides of one recording material P. 11h, 11i, a reversing roller 11j and the like are arranged.

Further, between the primary charger 2 and the developing device 4 around the photosensitive drum 1, a potential sensor S1 for detecting the charged potential on the surface of the photosensitive drum 1 is provided, and between the developing device 4 and the transfer drum 5a. Between them, density sensors S2 for detecting the density of the toner image on the photosensitive drum 1 are arranged.

Next, the reader section II will be described.
The reader unit II disposed above the printer unit I includes a document table glass 12a on which the document D is placed.
Exposure lamp 12b for exposing and scanning the image surface, a plurality of mirrors 12c for further reflecting light reflected from document D, a lens 12d for condensing the reflected light, and a color separation image signal based on the light from lens 12d. Is formed. The color-separated image signal is processed by a video processing unit (not shown) through an amplifier circuit (not shown), and is sent to the above-described printer unit I. Next, the operation of the image forming apparatus having the above-described configuration will be briefly described while adding some components. In the following description, it is assumed that four full-color images are formed in the order of yellow, cyan, magenta, and black.

The image of the original D placed on the original platen glass 12a of the reader unit II is irradiated by an exposure lamp 12b, color-separated, and a yellow image is first read by a full-color sensor 12e and subjected to predetermined processing. The image data is sent to the printer unit I as an image signal.

On the other hand, in the printer section I, the photosensitive drum 1 is driven to rotate in the direction of the arrow Rl, and the surface of the photosensitive drum 1 is uniformly charged by the primary charger 2. Reader unit I described above
A laser beam is emitted from a laser output unit of the exposure unit 3 based on the image signal sent from I, and the surface of the charged photosensitive drum 1 is exposed by a light image E via a polygon mirror 3a and the like. The exposed portion of the surface of the photosensitive drum 1 has its charge removed, whereby an electrostatic image corresponding to yellow is formed. In the developing device 4, the yellow developing device 4Y is arranged at a predetermined developing position, and the other developing devices 4C, 4M, and 4Bk are retracted from the developing position. The electrostatic latent image on the photosensitive drum 1 has yellow toner attached thereto by the developing device 4Y and is visualized to be a toner image.
The yellow toner image on the photosensitive drum 1 is transferred to the recording material P carried on the transfer drum 5a. The recording material P is supplied to the transfer drum 5a at a predetermined timing from a predetermined paper feeding cassette 8a having a size suitable for a document image via a paper feeding roller 8b, a conveying roller, a registration roller 8c, and the like. It is a thing. The recording material P supplied in this manner is attracted so as to wind around the surface of the transfer drum 5a, rotates in the direction of arrow R5, and the yellow toner image on the photosensitive drum 1 is transferred by the transfer charger 5b.

On the other hand, the photosensitive drum 1 after the transfer of the toner image
The residual toner on the surface is removed by the cleaning device 6, and unnecessary charges are further removed by the pre-exposure lamp 7 to be used for the next image formation starting from the primary charger.

The processes from the reading of the document image by the reader unit II, the transfer of the toner image carried on the recording material P on the transfer drum 5a, the cleaning of the photosensitive drum 1, and the elimination of the charge are performed in a process other than yellow. The same applies to other colors, that is, cyan, magenta, and black.
A toner image of four colors is transferred onto the recording material P on a in such a manner as to overlap.

Recording material P to which four color toner images have been transferred
Is separated from the transfer drum 5a by a separation charger 9a, a separation claw 9b, and the like, and is conveyed to the fixing device 10 with an unfixed toner image carried on the surface. The recording material P is a fixing device 1
At 0, the sheet is nipped and conveyed by the fixing roller 10a and the pressure roller 10b, heated and pressed, and the toner image on the surface is fused and fixed. The recording material P after fixing is fed to a discharge roller 11.
b discharges onto the paper discharge tray 11c. When images are formed on both sides of the recording material P, the fixing device 10 immediately transfers the discharged recording material P to the transport path switching guide 11a.
, And once guided to the reversing path 11e via the transport vertical path 11d, and then retreated in a direction opposite to the direction in which the sheet was fed by the reverse rotation of the reversing roller 11j with the rear end leading to the intermediate tray. Store in 11g. After that, an image is formed on the other surface again by the above-described image forming process, and then discharged onto the discharge tray 11c.

In the transfer drum 5a after the separation of the recording material P, in order to prevent the powder from adhering to the recording material supporting sheet 5g and the oil from adhering to the recording material P, the recording material supporting sheet 5g Fur brush 1 facing each other through
Cleaning is performed by 3a and the backup brush 13b, and by the oil removing roller 14a and the backup brush 14b. Note that such cleaning is performed before or after image formation, and is performed as needed when a jam (paper jam) occurs.

Next, the fixing device 10 will be described with reference to FIG.

In the figure, a fixing roller 10a which comes into contact with the toner image is a hollow iron core metal 31 having a thickness of 0.7 mm.
A 1.2 mm thick silicone rubber layer 32 and a 50 μm thick PFA (tetrafluoroethylene-perfluoroalkylvinyl ether copolymer) tube layer 3 on the outside
3 having a diameter of 40 mm.

On the other hand, the pressure roller 10b has a 5 mm thick silicone rubber layer 35 on a solid iron core 34 and a 50 μm thick PFA tube layer 36 thereon.
It is formed to have a diameter of 30 mm.

The fixing roller 10a has a main heater 37 and a sub-heater 38 disposed in the metal core 31. The fixing roller 10a is fixed by a thermistor 39 which is a fixing member temperature detecting means disposed in contact with the fixing roller 10a.
The main heater 37 and the sub-heater 38 are controlled by the control device 40 as control means based on the detected temperature, and the surface temperature of the fixing roller 10a is controlled to be maintained at a constant (target temperature). You. The fixing roller 10a and the pressure roller 10b are pressed by a pressing mechanism (not shown) with a total pressure of about 30 kg.
The fixing roller 10a and the pressure roller 10b rotate at a process speed of 110 mm / sec. Further, the control temperature of the surface temperature of the fixing roller 10a is 190 ° C.

In the fixing device 10, the recording material P carrying an unfixed toner image on its surface is nipped and conveyed by a fixing nip between the fixing roller 10a and the pressure roller 10b, and is heated and pressed at this time. The toner image is fixed on the recording material P.

Next, the main heater 37 and the sub-heater 38 used in this embodiment will be described with reference to FIG.

The main heater 37 has a power consumption of 500 W
When the light distribution in the longitudinal direction is 100% at both ends in the longitudinal direction from the range of 160 mm at the central portion in the longitudinal direction, the range is 150%. On the other hand, the sub-heater 38 is configured such that the power is 600 W and the light distribution in the longitudinal direction is 100% within a range of 140 mm at the central portion in the longitudinal direction, and 230% at both ends in the longitudinal direction outside the range. ing. In this embodiment, since the thermistor 39 is in contact with the substantially central portion of the surface of the fixing roller 10a in the longitudinal direction with respect to the installation positions of the main heater 37 and the sub heater 38, there is a heat generation peak at the central portion. By installing the main heater 37 at a position close to the thermistor 39, the accuracy of temperature control is improved.

Next, the rotational driving of the fixing roller 10a and the pressure roller 10b of the present embodiment will be described.

In the present embodiment, the fixing roller 10a and the pressure roller 10b are rotated and driven alternately for 2 minutes and for 3 minutes during standby. This is to prevent the temperature of the fixing roller 10a from being lowered by the pressing roller 10b during fixing.
In addition, the fixing roller 10a and the pressure roller 1
The peripheral speed of 0b is 25 mm / sec.

Next, the main heater 3 in the present embodiment
The time division control of the sub heater 7 and the sub heater 38 will be described.

The time division control of the main heater 37 and the sub-heater 38 in this embodiment is based on the first lighting time ratio of 2 seconds for the main heater 37 and 6 for the sub-heater 38 during the rotation of the fixing roller 10a and the pressure roller 10b during standby. The fixing roller 10a lights up alternately in seconds, and is in the standby state.
When the pressure roller 10b is stopped, only the sub-heater 38 is turned on as a second lighting time ratio. or,
In the time-division control during the nip passing of the recording material P, the lighting time of the main heater 37 and the sub-heater 38 varies depending on the paper width. For example, in the present embodiment, when the recording material P is A4 horizontal (paper width 297 mm), the main heater Are alternately turned on for 300 ms and the sub-heater for 125 ms.

In the fixing device of this embodiment, when the sheet was continuously passed for 1000 sheets of A4 width paper after being left for one hour in the standby state, a good fixed image free of paper wrinkles and low-temperature offset was obtained.

As a comparative example, when the lighting time ratio between the main heater and the sub-heater is not changed when the fixing roller and the pressure roller are rotating or stopped during standby, the main heater and the sub-heater alternate with 2 seconds and 6 seconds. In case of lighting, A4 horizontal 1
When 000 sheets were continuously passed, a low-temperature offset occurred at both ends of the recording material P in the axial direction of the fixing roller.
Similarly, when only the sub-heater is turned on during standby, if 1000 sheets are continuously passed, the initial to approximately 2
Paper wrinkling occurred between 00 sheets.

In the present embodiment, the fixing roller 10
a and the rotation of the pressure roller 10b
Considering that the heat of a is taken by the pressure roller 10b,
The control temperature of the fixing roller 10a may be changed between when the fixing roller 10a and the pressure roller 10b rotate and when the fixing roller 10a stops.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIG. Note that the same components as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

In the fixing device according to this embodiment shown in FIG. 4, the pressure roller 1 is controlled by a second thermistor 41 serving as pressure body temperature detecting means disposed in contact with the pressure roller 10b.
0b, the rotation of the fixing roller 10a and the pressure roller 10b is controlled by the rotation control device 42 as a driving means based on the detected temperature.
The temperature b is controlled so as to be kept constant.

Next, the rotation and stop sequence of the fixing roller and the pressure roller in this embodiment will be described.

In this embodiment, when the detected temperature of the second thermistor 41 falls below a predetermined rotation start temperature (100 ° C. in this embodiment) during standby, the fixing roller 10a
The rotation of the pressure roller 10 b is started by the rotation control device 42 at a peripheral speed of 25 mm / sec. Fixing roller 1
By the rotation of the pressure roller 10a and the pressure roller 10b, the surface of the pressure roller 10b is heated by the fixing roller 10a, and the detected temperature of the second thermistor 41 rises above a predetermined rotation stop temperature (150 ° C. in the present embodiment). Then, the rotation of the fixing roller 10a and the pressure roller 10b is stopped by the rotation control device 42.

On the other hand, the surface temperature of the fixing roller 10a is maintained by turning on only the sub-heater 38 as the second lighting time ratio when the rotation of the fixing roller 10a and the pressure roller 10b in the standby state is stopped. When the rotation of the pressure roller 10b is started, the main heater 37 is turned on by the control device 40 as the first lighting time ratio for 2 seconds,
The surface temperature of the fixing roller 10a is maintained by alternately lighting the sub heater 38 for 6 seconds. Then, when the rotation of the fixing roller 10a and the pressure roller 10b is stopped, only the sub-heater 38 is turned on again.

In the fixing apparatus of the present embodiment, when the sheet was left standing for one hour in the standby state and continuous A4 width 1000 sheets were passed, a good fixed image free of paper wrinkles and low-temperature offset was obtained.

As a comparative example, when the lighting time of the main heater and the sub-heater is not changed when the fixing roller and the pressure roller are rotating or stopped during standby, the main heater and the sub-heater are alternately turned on for 2 seconds and the sub-heater for 6 seconds. , A4 horizontal 100
When zero sheets were continuously passed, a low-temperature offset occurred at both ends of the recording material in the axial direction of the fixing roller. Similarly, when only the sub-heater is turned on during standby, when 1000 sheets are continuously passed, paper wrinkling occurs between the initial time and about 200 sheets.

In this embodiment, the fixing roller 1
0a and the rotation of the pressure roller 10b, the fixing roller 1
The control temperature of the fixing roller 10a may be changed between when the fixing roller 10a and the pressing roller 10b are rotating and when the fixing roller 10a is stopped, in consideration of the fact that the heat of 0a is taken by the pressing roller 10b.

[0074]

As described above, according to the first invention of the present application, the heat of the surface of the fixing body is transferred to the surface of the pressing body by the rotation of the fixing body and the pressing body during the fixing standby. While being transmitted and the pressurizing body is heated, the balance of the heat generation in the axial direction of the fixing body of the first heating body and the second heating body during rotation and stoppage of the fixing body and the pressurizing body during standby for fixing is adjusted. Since the heating means heats the fixing body while aiming, the surface temperature of the fixing body and the pressing body is maintained at a predetermined temperature even after a long fixing standby state with an inexpensive configuration,
A good fixed image can be obtained by preventing the occurrence of paper wrinkles and low-temperature offset.

According to the second invention of the present application,
The heat of the surface of the fixing member is transmitted to the surface of the pressing member by the rotation of the fixing member and the pressing member during the fixing standby, and the pressing member is heated. Since the heating means heats the fixing body while balancing the heat generation in the axial direction of the fixing body between the first heating element and the second heating element during rotation and at the time of stopping, the configuration is inexpensive,
Even after the fixing standby state for a long time, the surface temperature of the fixing body and the pressing body is maintained at a predetermined temperature, and the occurrence of paper wrinkling and low-temperature offset can be prevented, and a good fixed image can be obtained.

Further, according to the third aspect of the present invention, the heat of the surface of the fixing member is transmitted to the surface of the pressing member by the rotation of the fixing member and the pressing member during the fixing standby, so that the pressing member is Is heated and maintained at a predetermined temperature, and the balance of heat generation in the axial direction of the fixing body of the first heating element and the second heating element during rotation and stoppage of the fixing body and the pressurizing body in the fixing standby state. Since the heating means heats the fixing member, the surface temperature of the fixing member and the pressure member is maintained at a predetermined temperature even after a long fixing standby state, and the paper wrinkles are reduced. The occurrence of low-temperature offset can be prevented, and a good fixed image can be obtained.

According to the fourth invention of the present application,
During the fixing standby, heat of the surface of the fixing body is transmitted to the surface of the pressing body by rotation of the fixing body and the pressing body, and the pressing body is heated and maintained at a predetermined temperature. In addition, the heating means heats the fixing body while balancing the heat generation in the axial direction of the fixing body between the first heating element and the second heating element during rotation and stop of the pressing body, so that the cost is low. Even after a long fixing standby state, the surface temperature of the fixing body and the pressure body is maintained at a predetermined temperature,
A good fixed image can be obtained by preventing the occurrence of paper wrinkles and low-temperature offset.

Further, according to the fifth aspect of the present invention, the heat of the surface of the fixing member is transmitted to the surface of the pressing member by the rotation of the fixing member and the pressing member during the fixing standby, so that the pressing member is rotated. Is heated, and the heating unit performs fixing while balancing the heat generation in the axial direction of the fixing body of the first heating element and the second heating element during rotation and stoppage of the fixing body and the pressing body during standby for fixing. Because the body is heated, the surface temperature of the fixing body and the pressing body is maintained at a predetermined temperature even after a long fixing standby state, and the occurrence of paper wrinkles and low-temperature offset is achieved with an inexpensive configuration. And a good fixed image can be obtained.

According to the sixth invention of the present application,
The heat of the surface of the fixing member is transmitted to the surface of the pressing member by the rotation of the fixing member and the pressing member during the fixing standby, and the pressing member is heated. Since the heating means heats the fixing body while balancing the heat generation in the axial direction of the fixing body between the first heating element and the second heating element during rotation and at the time of stopping, the configuration is inexpensive,
Even after the fixing standby state for a long time, the surface temperature of the fixing body and the pressing body is maintained at a predetermined temperature, and the occurrence of paper wrinkling and low-temperature offset can be prevented, and a good fixed image can be obtained.

Further, according to the seventh aspect of the present invention, the heat of the surface of the fixing member is transmitted to the surface of the pressing member by the rotation of the fixing member and the pressing member during standby for fixing, so that the pressing member is rotated. Is heated and maintained at a predetermined temperature, and the balance of heat generation in the axial direction of the fixing body of the first heating element and the second heating element during rotation and stoppage of the fixing body and the pressurizing body in the fixing standby state. Since the heating means heats the fixing member, the surface temperature of the fixing member and the pressure member is maintained at a predetermined temperature even after a long fixing standby state, and the paper wrinkles are reduced. The occurrence of low-temperature offset can be prevented, and a good fixed image can be obtained.

According to the eighth invention of the present application,
During the fixing standby, heat of the surface of the fixing body is transmitted to the surface of the pressing body by rotation of the fixing body and the pressing body, and the pressing body is heated and maintained at a predetermined temperature. In addition, the heating means heats the fixing body while balancing the heat generation in the axial direction of the fixing body between the first heating element and the second heating element during rotation and stop of the pressing body, so that the cost is low. Even after a long fixing standby state, the surface temperature of the fixing body and the pressure body is maintained at a predetermined temperature,
A good fixed image can be obtained by preventing the occurrence of paper wrinkles and low-temperature offset.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a schematic configuration of a fixing device provided in the image forming apparatus of FIG.

FIG. 3 is a diagram showing a light distribution of a first heating element and a second heating element of a heating unit provided in the fixing device of FIG. 2;

FIG. 4 is a sectional view illustrating a schematic configuration of a fixing device according to a second embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 10 fixing device (fixing device) 10a fixing roller (fixing member) 10b pressure roller (pressing member) 37 main heater (first heating member) 38 sub heater (second heating member) 39 thermistor (fixing member temperature detecting means) 40 Control device (control means) 41 Second thermistor (pressurized body temperature detecting means) 42 Rotation control device (drive means) P Recording material (recording medium)

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H033 AA03 AA09 AA15 BB05 BB14 BB18 BB29 CA02 CA04 CA23 CA45 3K058 AA34 AA71 BA18 CA16 CB02 CB19 CB27 CE17 CE21 CE24 DA02 DA06 GA06

Claims (8)

[Claims] 1. A fixing member and a pressure member which are rotatably disposed in pressure contact with each other, a heating unit for heating the fixing member, a fixing member temperature detecting unit for detecting a surface temperature of the fixing member, and the fixing unit. A fixing unit configured to control heating of the heating unit so that the surface temperature of the fixing member detected by the body temperature detecting unit reaches a target temperature; and a driving unit configured to rotationally drive the fixing unit and the pressing unit, and carry an unfixed image. A fixing device for fixing the unfixed image to the recording medium by heating and pressing the recording medium to be nipped and transported by a fixing body and a pressure body,
The heating unit includes a first heating element and a second heating element that are disposed in the fixing body and have different light distributions in the axial direction of the fixing body, and the first heating element is disposed at a central portion in the axial direction. Having a peak, the second heating element has a light distribution peak at the axial end side, and the control means alternately lights the first heating element and the second heating element at a predetermined lighting time ratio. In the fixing device, the driving unit intermittently rotates or stops the fixing body and the pressing body at predetermined intervals during the fixing standby, and the control unit performs the first rotation during the rotation of the fixing body and the pressing body during the fixing standby. The first heating element and the second heating element are turned on at one lighting time ratio, and the first heating element and the second heating element are turned on at a second lighting time ratio when the fixing body and the pressure body are stopped during standby for fixing. The first lighting time ratio is set to the second lighting time of the first heating element. Longer than the lighting time of the first heating element by time ratio, and a fixing device, characterized in that the lighting time of the second heating element is set shorter than the lighting time of the second heating element by the second turn-on time ratio. 2. The control device according to claim 1, wherein the control unit sets the target temperature such that the surface temperature of the fixing body during rotation of the fixing body and the pressure body during standby for fixing is higher than when the fixing body is stopped.
3. The fixing device according to claim 1. 3. A fixing member and a pressure member which are pressed against each other and are rotatably disposed, a heating means for heating the fixing member, a fixing member temperature detecting means for detecting a surface temperature of the fixing member, Pressurizing body temperature detecting means for detecting the surface temperature of the body, control means for controlling heating of the heating means so that the fixing body surface temperature detected by the fixing body temperature detecting means becomes a target temperature,
A driving unit for rotationally driving the fixing body and the pressing body,
A fixing device for fixing the unfixed image to the recording medium by nipping and conveying the recording medium carrying the unfixed image between the fixing member and the pressing member, and heating and pressing the recording medium. A first heating element and a second heating element having different light distributions in the axial direction of the fixing member, wherein the first heating element has a light distribution peak at the center in the axial direction, and In a fixing device in which the body has a light distribution peak on the axial end side, and the control means alternately lights the first heating element and the second heating element at a predetermined lighting time ratio, the driving means includes During the fixing standby, when the pressure body surface temperature detected by the pressure body temperature detection means is below a predetermined temperature, the fixing body and the pressure body are rotated, the control means,
The first heating element and the second heating element are turned on at the first lighting time ratio when the fixing body and the pressure body rotate during the fixing standby, and the second lighting time ratio when the fixing body and the pressure body are stopped during the fixing standby. In the first heating element and the second heating element are set to be lit, the first lighting time ratio is longer than the lighting time of the first heating element by the lighting time of the first heating element by the second lighting time ratio, and A fixing device wherein the lighting time of the second heating element is set shorter than the lighting time of the second heating element based on the second lighting time ratio. 4. The control device according to claim 3, wherein the control unit sets the target temperature such that the surface temperature of the fixing body during rotation of the fixing body and the pressure body during standby for fixing is higher than when the fixing body is stopped.
3. The fixing device according to claim 1. 5. An image forming apparatus for recording an image formed by a series of image forming processes on a recording medium,
An image forming apparatus comprising the fixing device according to claim 1. 6. The control device according to claim 5, wherein the control unit sets the target temperature such that the surface temperature of the fixing member during rotation of the fixing member and the pressure member during standby for fixing is higher than when the fixing member is stopped.
An image forming apparatus according to claim 1. 7. An image forming apparatus for recording an image formed by a series of image forming processes on a recording medium,
An image forming apparatus comprising the fixing device according to claim 3. 8. The control means sets a target temperature such that the surface temperature of the fixing member during rotation of the fixing member and the pressure member during standby for fixing is higher than when the fixing member is stopped.
An image forming apparatus according to claim 1.