JPH09319253A - Color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color image forming device which decreases startup temperature, exerts temperature control by a simple method, and obtains a color image of high image quality at a low cost. SOLUTION: The device is equipped with a fixing film 39 in which an elastic layer 39b and a releasing layer 39a are provided on a film base layer 39c, a ceramic heater 41, a pressure roller 31 disposed in pressure-contact with the ceramic heater 41 via the fixing film 39, and a halogen heater 28" disposed in the pressure roller 31. By using a thermister 42 on the ceramic heater 41, the temperatures of the pressure roller 31 and ceramic heater 41 are detected and controlled so that they have the specific temperatures.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus such as a color printer, a color copying machine and a color facsimile, which uses an electrophotographic method.

[0002]

2. Description of the Related Art Conventionally, in a color image forming apparatus using an electrophotographic recording method, one photoconductor is used as an image carrier, and a plurality of color toners such as yellow, cyan, magenta and black are placed on the photoconductor. Multiple development method for multiple development, multiple development for each color, and multiple transfer method for performing multiple transfer while holding a transfer material such as paper on the transfer drum by electrostatic attraction, insulation or medium resistance instead of paper There is an intermediate transfer method in which multiple transfer is performed on a transfer body and then batch transfer is performed on a transfer material. In addition to these methods, a combination of four color developing means and four transfer means on four photoconductors, There is a 4-drum system in which development and transfer of each color are sequentially performed in accordance with conveyance.

The characteristics of each of the above-mentioned methods are as follows. First, the multi-developing method can minimize the number of constituent elements. Is difficult to achieve. Next, in the multiple transfer method, the image quality is most stable, but the holding function of the transfer material is complicated, and there are many limitations on the paper types that can be held, and it is difficult to increase the speed.
Further, the intermediate transfer method is somewhat disadvantageous in terms of image quality as compared with the above-mentioned multiple transfer method, but the transfer material is easy to convey, the paper type is not selected, and the speed is higher than that of the above multiple transfer method. Also, 4
Although the drum method is the fastest, it requires high-precision control for superimposing each color and has a large number of parts, resulting in high cost and a large apparatus.

Further, a non-magnetic toner is used for colorization as a developer used in each system having such characteristics, and is roughly classified into a two-component non-magnetic toner and a one-component non-magnetic toner. Two types are used.

Since the two-component non-magnetic toner can hold the toner by a magnetic force, it is advantageous for the toner contamination in the machine, but since the magnetic carrier and the developing magnet are used,
Since the weight of the device becomes heavy, it is not suitable for applications such as small desktop printers that realize easy maintenance by making the peripheral members of the developing device into a cartridge. For these applications, the device using one-component non-magnetic toner is suitable. ing.

FIG. 10 is a cross-sectional view of a color printer using a one-component non-magnetic toner in a multiple transfer system as an example, and a photosensitive drum 1 as an image carrier is arranged at the center of the cross section of the apparatus. . The photosensitive drum 1 has a diameter of 40 m.
The organic photoconductor (O
It is constructed by applying a photoconductor consisting of PC).
Not limited to C, A-Si, CdS, Se or the like may be used. In addition, the photosensitive drum 1 is driven by a driving unit (not shown)
It is driven in the direction of the arrow shown in the drawing at a peripheral speed of 00 mm / scc.

Above the photosensitive drum 1, a polygon mirror 13, a lens 14, and a folding mirror 1 which are driven to rotate by a laser diode 11 and a high speed motor 12.
An optical system unit 16 including 5 is disposed, and a charging roller 3 is disposed above the photosensitive drum 1.

An AC voltage of Vpp (peak-to-peak): -1500V is superimposed on the charging roller 3 at a DC voltage of -700V at an AC frequency of 700Hz, and the photosensitive drum 1 is uniformly charged to about -700V. . .

Next, on the right side of the photosensitive drum 1, a plurality of non-magnetic developing devices 4a, 4b, 4c and 4d are carried by a rotatable support. Each developing device rotates counterclockwise along a cylindrical rail 9'provided at each end of the device about the support rotating shaft 9, while each developing device 4a,
b, 4c and 4d are set so as to rotate in the clockwise direction to maintain the horizontal positions of the developing opening surfaces 5a, 5b, 5c and 5d. Further, yellow toner, magenta toner, cyan toner, and black toner are stored in the developing units 4a, 4b, 4c, and 4d, respectively.
As shown in FIG. 6, there are coating rollers 6a, 6b, 6c, 6d and toner regulating members 7a, 7b, 7c, 7d, and the coating roller 6 is rotated as the developing rollers 8a, 8b, 8c, 8d rotate.
a, 6b, 6c, 6d on the developing rollers 8a, 8b, 8
The toner is applied onto the c and 8d, and the toner regulating member 7
The necessary tribo is imparted to the toner by a, 7b, 7c and 7d. The material of the regulating member is preferably nylon or the like when the toner has a negative polarity and is preferably silicone rubber or the like when the toner is positively charged, and is preferably a material that is charged opposite to the polarity of the toner. Further, the developing rollers 8a, 8
The peripheral speed of b, 8c, and 8d is 1.0 to the peripheral speed of the photosensitive drum 1.
It is preferable to select the peripheral speed in the range of 2.0 times.

Further, the developing devices 4a, 4b, 4c, 4d mounted around the support rotary shaft 9 have developing opening surfaces 5a, 5 of the developing devices 4a, 4b, 4c, 4d as shown in FIG.
b, 5c and 5d are always driven so as to face the surface of the photosensitive drum 1, and one driving method is disclosed in JP-A-50-9343.
This is described in detail in Japanese Patent Publication No.

Further, as shown in FIG. 10, the photosensitive drum 1
A transfer roller 10 as a transfer unit that holds a transfer material (not shown) and has a function of transferring an image on the photosensitive drum 1 onto the transfer material (not shown) is arranged on the left side of the. .

In the color printer having the above structure, when a signal according to the yellow image pattern is input to the laser diode 11, the photosensitive drum 1 is irradiated through the optical path indicated by the arrow, and the photosensitive drum 1 is , The area irradiated with light is about -100V, and an electrostatic latent image is formed.

Further, when the photosensitive drum 1 advances in the direction of the arrow, the electrostatic latent image is visualized by the yellow toner of the developing device 4a and is transferred onto the transfer material by the following transfer process. First, in synchronization with the image on the photosensitive drum 1, the transfer material is fed from the transfer material cassette 17 by the pickup roller 18 and adsorbed to the transfer roller 10. The transfer roller 10 is a metal cylinder 1 having a diameter of 156 mm.
The elastic layer 20 having a thickness of 2 mm is wound around the layer 9, and the PVDF 21 having a thickness of 100 μm is wound around the elastic layer 20. The elastic layer 20 rotates in the arrow direction at about the same speed as the photosensitive drum 1.

When the above-mentioned transfer material is supplied to the transfer roller 10, the transfer material (not shown) is moved by the gripper 22.
And the toner image on the photosensitive drum 1 is applied by a power source (not shown) to the photosensitive drum 1 and the transfer roller 1.
It is transferred onto a transfer material (not shown) by a voltage of 0, and at the same time, it is attracted to the transfer roller 10 by the charge injection into the transfer material (not shown). If necessary, a voltage may be applied between the suction rollers 23 to pre-suck them.

By performing the above steps for magenta, cyan, and black, toner images of a plurality of colors are formed on the transfer material, and the transfer material is peeled from the transfer roller 10 by the separation claw 24 and further transferred. The material is melted and fixed by a conventionally known heating and pressure fixing device 25 to obtain a color image. The transfer residual toner on the photosensitive drum 1 is cleaned by a cleaning device 26 such as a known fur brush and blade means. Further, it is preferable that the toner on the transfer roller 10 is also cleaned by a transfer roller cleaning device 27 such as a fur brush or a web if necessary. Further, when the transfer roller surface after the separation is still charged, a step of canceling the surface charge by the charge removing roller 23 'is required.

Next, the fixing device 25 in the above color printer will be described in detail with reference to FIG. In FIG. 12, 30 is a fixing roller, and the fixing roller 30 has a thickness of about 2 m on the surface of an aluminum cored bar 29.
m fixing silicone rubber 30a is formed, and the fixing halogen heater 28 is provided inside. This fixing roller 3
Below 0, a pressure roller 31 having a pressure-applying silicone rubber 31a having a thickness of about 1 mm on the surface of an aluminum cored bar 29 and having a fixing halogen heater 28 therein.
Is provided, and around the fixing roller 30,
Surface temperature detection thermistor 32, cleaning web 3
3, sponge roller 33a and take-up roller 33
Further, a cleaning means constituted by b is provided, and an oil applying mechanism for enhancing the surface releasability is further provided with an oil applying roller 34, an oil regulating blade 34a, an oil pumping roller 34b, an oil sump container 34c, a tube 34d, a pump. 34e, oil pan 34f, silicone oil 3
It is composed of 4 g or the like.

On the other hand, on the surface of the pressure roller 31, in addition to the surface temperature detecting thermistor 32, an oil cleaning blade 35 for scraping off unnecessary oil adhering to the surface is provided below the roller 35. The oil scraped off by is collected in an oil tray with an opening below and reused via a pump. A part of the entire fixing device serves as a fixing inlet and outlet fixing member. Covered by the unit frame 36,
If necessary, a heat insulating material is used for the frame 36 so as to have a function of preventing burns due to residual heat when the fixing device is replaced.

In the above-mentioned conventional example, a good color image is fixed by the above fixing device.

[0019]

However, in the above fixing device for a color image forming apparatus, an unfixed image in which a plurality of toners are overlapped with each other and the unevenness of the toner layer is severe is sufficiently melted and mixed in the fixing nip portion to form a color image. In order to improve reproducibility, a thick rubber layer having a high heat capacity is required above and below, so that it may take a long time to rise from room temperature to a desired fixing temperature.

Further, in order to maintain stable fixability by using a roller having a high heat capacity, which has poor responsiveness to a color image which causes a large change in image quality with a slight temperature change, the surface temperature of each roller is changed. In some cases, it has been necessary to detect finely and perform complicated control according to each temperature state.

Further, as a safety measure in the event that the heater goes out of control due to some failure in the temperature detecting portion, a bimetal or a thermal fuse having a function of shutting off a part of an electric circuit by heat in an excessive temperature range is used. In some cases, the constructed temperature switch also had to be provided on the upper and lower rollers, respectively.

Therefore, an object of the present invention is to provide a color image forming apparatus capable of obtaining a high quality color image at a low cost by shortening the start-up temperature and controlling the temperature by a simple method. is there.

[0023]

According to the first invention of the present application, the above object is to fix a color toner image formed on an image carrier on a transfer material by a transfer means and then to a fixing means. In the color image forming apparatus for applying heat and pressure to the color toner image to fix the color toner image on the transfer material,
The fixing means comprises a heat-resistant film having a small heat capacity, which has an elastic layer disposed on a side which comes into contact with an image surface of an unfixed color toner when heat and pressure are applied to the transfer material; A low-heat-capacity film-side heating element that is disposed so as to be in sliding contact with the surface opposite to the contact side with the image surface, and elasticity that is disposed so as to be in pressure contact with the heating element through the heat-resistant film. A pressing member having a body layer, a pressing-side heating body included in the pressing member, and a temperature detecting means provided on the side opposite to the sliding contact surface side of the film-side heating body with the heat-resistant film. The temperature control of the film-side heating body and the pressure member is performed based on the temperatures of the film-side heating body and the pressure member detected by the temperature detecting means.

According to the second aspect of the present invention,
The above-mentioned object is, in the above-mentioned first invention, the heat-resistant film is a film in which a heat-resistant thin elastic layer and a heat-resistant release layer are laminated in this order on a film base layer, and the film-side heating element generates heat on a ceramic substrate. This is achieved by being a ceramic heater that forms a body, and the pressing member is a pressing roller having a thick heat-resistant elastic body layer on a core metal.

Further, according to a third invention of the present application, in the above-mentioned first invention or the second invention, the pressure side heating element contained in the pressure member is driven at maximum output. It is a low output heater that saturates to a temperature sufficiently lower than the fixing temperature even if it continues to operate, and the temperature detection of the pressure member by the temperature detection means is performed only during the start-up period from the room temperature to the saturation temperature. When the failure of the pressurizing side heating element is judged based on the result of the above, and when the image forming operation start signal is received during the start-up period, the heat resistant film and the above-mentioned additive are added according to the temperature detection result at the time of reception. This is achieved by adjusting the driving time of the film-side heating body at the maximum output while rotating the pressure member to raise the film-side heating body to a desired fixing temperature.

According to the fourth invention of the present application,
In the first or second aspect of the invention described above, the pressure-side heating element contained in the pressure member is a high-output heater that rises to a temperature sufficiently higher than the fixing temperature when continuously driven at the maximum output. Yes, the temperature control of the pressure member is performed so as to maintain a predetermined temperature based on the temperature detection result of the temperature detection unit until the image forming operation start signal is received.
After the image forming operation start signal is received, the amount of heat absorbed by the transfer material is reduced to a level that compensates for it.The temperature control of the film-side heating element is performed in advance according to the temperature detection result when the image forming operation start signal is received. This is achieved by selecting a predetermined target temperature, starting heating, and sequentially switching to a plurality of predetermined target temperatures according to the number of transfer materials on which an image is formed.

Further, according to a fifth aspect of the present invention, in the above-mentioned fourth aspect, the film side heating element is provided with an excessive temperature rise preventing means, and the excessive temperature rise is carried out. The prevention means is achieved by also functioning as an excessive temperature rise prevention means for the heating body on the pressure side.

According to the sixth aspect of the present invention,
The above object is achieved in any one of the first to fourth inventions, wherein the film-side heating body is a heater for heating a magnetic metal plate having good thermal conductivity by using an electromagnetic induction heating method. To be done.

Further, according to the seventh invention of the present application, the object is to transfer the color toner image formed on the image carrier onto the transfer material by the transfer means, and then to fix the color toner image by the fixing means. In a color image forming apparatus for applying heat and pressure to an image to fix it on a transfer material, the fixing means is disposed on a side which comes into contact with an unfixed color toner image surface when heat and pressure are applied to the transfer material. A heat-resistant film having a heat-resistant thin elastic layer and a heat-resistant release layer laminated in this order on the surface of the magnetic metal film, so that the surface of the heat-resistant film on the opposite side of the contact side with the image side is in sliding contact. A film-side heating element that is arranged to heat the magnetic metal film using an electromagnetic induction heating method, and a thick heat-resistant element that is arranged so as to come into pressure contact with the heating element through the heat-resistant film. Elastic layer A pressure member having the pressure member, a low-output pressure-side heating member which is contained in the pressure member and is saturated to a temperature sufficiently lower than the fixing temperature even when continuously driven at the maximum output, and provided so as to contact the pressure member. Temperature detecting means,
The temperature control of the film side heating element and the pressure member is obtained by the temperature detecting means based on the correlation between the surface temperature change of the pressure element and the temperature of the film side heating element which are obtained in advance. This is achieved by estimating the temperature on the film rotating body side from the change in the surface temperature of the pressure member.

According to an eighth aspect of the present invention,
The above-mentioned object is, in any one of the above-mentioned first invention to the seventh invention, that as a means for preventing the fixing offset by increasing the releasability of the toner from the surface of the heat-resistant film and the pressing member during fixing. This is achieved by using a toner having a wax for improving releasability contained therein.

That is, in the first invention of the present application, since the heat-resistant film having a small heat capacity and the elastic layer is provided on the surface contacting with the color toner as the fixing means for forming the color image, the conventional meat is used. Faster start-up than a fixing roller using thick rubber is realized, and at the same time, responsiveness is improved, and heat resistance is improved by predetermining the target temperature according to the number of transfer materials for image formation and the transfer material supply interval. Stable temperature control is performed by the temperature detecting means provided on the side of the permeable film.

In the second invention of the present application, the heat-resistant film of the first invention is a film in which a heat-resistant thin elastic layer and a heat-resistant release layer are laminated in this order on a film base layer. The film-side heating element is a ceramic heater having a heating element formed on a ceramic substrate, and the pressure member is a pressure roller having a thick heat-resistant elastic layer on a core metal. With the elastic layer, the unfixed color image having severe unevenness is sufficiently melted and mixed in the fixing nip portion, while the heat-resistant film having a low heat capacity and the ceramic heater realize a quick start-up.

Further, in the third invention according to the present application, the pressure side heating element included in the pressure member of the first invention or the second invention is fixed at the fixing temperature even if it is continuously driven at the maximum output. It is a low output heater that saturates at a sufficiently lower temperature,
Since the temperature of the pressure member is detected by the temperature detecting means only during the start-up period from the room temperature to the saturation temperature, the start-up time can be shortened, and the above-mentioned addition can be performed based on the result of the temperature detection. Safety is ensured as the failure of the pressure side heating element is judged. Further, when the image forming operation start signal is received during the start-up period, the film-side heating body at the maximum output is rotated while rotating the heat resistant film and the pressing member according to the temperature detection result at the time of reception. The heating time of the film side heating element is raised to a desired fixing temperature by adjusting the driving time of
In addition to shortening the start-up time during continuous image forming operations, the responsiveness of the heat supply for compensating for the heat absorbed by the transfer material during the fixing operation is improved, so that the fixability and glossiness due to temperature decrease can be improved. Does not cause a drop.

In the fourth invention according to the present application, the pressure side heating element included in the pressure member of the first invention or the second invention is fixed at the fixing temperature when continuously driven at the maximum output. It is a high-output heater that raises to a sufficiently higher temperature, and the temperature control of the pressure member is such that a predetermined temperature is maintained based on the temperature detection result of the temperature detection means until the image forming operation start signal is received. After the image forming operation start signal is received, the amount of heat absorbed by the transfer material is reduced to a level that can be compensated for, so the start-up time is reduced with the assistance of heating from the pressure member while reducing power consumption. To improve the responsiveness of heat supply. In addition, the temperature control of the film-side heating element is performed by selecting a predetermined target temperature according to the temperature detection result at the time of receiving the image forming operation start signal and starting heating, depending on the number of transfer materials to be image-formed. The target temperature is sequentially switched to a plurality of predetermined target temperatures, so that stable and good fixability is maintained in continuous image forming operations.

Further, in the fifth invention according to the present application, the film-side heating body of the fourth invention is provided with an excessive temperature rise prevention means, and the excessive temperature rise prevention means heats the pressure side. Since it also serves as the excessive temperature rise prevention means for the body, one excessive temperature rise prevention means prevents runaway of the heating body on the film side and the pressure side.

Further, in the sixth invention according to the present application, the film-side heating body according to any one of the first to fourth inventions has a magnetic property of good thermal conductivity by using an electromagnetic induction heating system. Since it is a heater that heats a metal plate, it has a higher thermal conductivity than a ceramic heater, realizes high-speed heat transfer, and improves the responsiveness of the temperature detecting means and the control accuracy.

Further, in the seventh invention according to the present application, the temperature detecting means is used even when the method of heating the metal film by electromagnetic induction heating, which is difficult to provide the temperature detecting means in the vicinity of the fixing nip portion, is used. Provided on the pressure member side,
Since the control is performed based on the correlation between the change in the surface temperature of the pressure member and the temperature of the film-side heating body, accurate temperature control is performed even if local pressure or temperature unevenness occurs in the fixing nip portion.

Further, in the eighth invention according to the present application, in any one of the first invention to the seventh invention, the releasing property of the toner from the surface of the heat resistant film and the pressing member at the time of fixing is improved. As a means to prevent fixing offset by increasing the toner, a toner containing a wax for improving releasability is used inside the toner, so heat applied to the oil and the coating mechanism that has been generated in the conventional configuration requiring oil coating. Since the leak is suppressed, the detection accuracy and the rising characteristic are improved.

[0039]

BEST MODE FOR CARRYING OUT THE INVENTION 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 FIGS. FIG.
(A), (B), and (C) are a fixing device sectional view, a film sectional view, and a heater sectional view of the color image forming apparatus showing the first embodiment of the present invention. In FIG. 1A, members having the same numbers as those in FIG. 12 indicate the same constituent elements, and in the present embodiment, a film fixing system using a low heat capacity fixing film 39 as a heat resistant film instead of the fixing roller. Is used.

The fixing film 39 is conveyed by the driving roller 37 and the driven roller 38, and at a proper pressure applied to the heater holder 40 in the heating portion, the fixing side heater (hereinafter, referred to as a film side heater) in the fixing nip portion is used. Ceramic heater 4 newly provided as an upper heater)
1 is pressed against the pressure roller 31 as a pressure member.

As shown in FIG. 1 (B), the sectional structure is based on a polyimide film 39c having a thickness of about 50 μm as a base layer, and a thin silicone rubber layer 39b having a thickness of about 100 μm and a thickness of about 20 μm on the polyimide film 39c. The surface releasable layer 39a made of a fluororesin is laminated.

On the other hand, the sectional structure of the ceramic heater 41 is such that a heating element 41b is pattern-formed on the surface of the ceramic substrate 41a and a glass coat layer 41c is coated on the surface, and the back surface of the ceramic substrate 41a is a miniaturized chip shape. The thermistor 42 is adhered. A ceramic having a high thermal conductivity is used for the ceramic substrate 41a, and it is possible to accurately detect a temperature rise on the heating element side, and by combining it with a fixing film having a low heat capacity, the entire ceramic heater 41 can be sufficiently operated. In the cooled state, the temperature on the pressure roller 31 side can be transmitted almost as it is, and therefore the temperature on the surface of the pressure roller 31 can be detected.

In the present embodiment, the advantage of the above construction is utilized, and even when full power is applied as a heater (hereinafter referred to as a lower heater) on the pressure roller 31 side, the saturation temperature is a desired fixing temperature and fixing. By using the low power halogen heater 28 ″ of about 30 W, which can reach a temperature sufficiently lower than the heat resistant temperature of the peripheral members of the vessel, the pressure roller 31
It is possible to provide a color fixing device that has a faster rising characteristic and lower power consumption than a conventional fixing device while omitting the thermistor on the side, and controls the printing operation according to the flowchart shown in FIG. This is achieved with.

That is, as shown in the flow chart of FIG. 2, the lower heater is energized at the same time when the power source of the apparatus is turned on (step S1), and the input power is not controlled until the power source of the apparatus is turned off. It is saturated to a temperature Hp that equilibrates with the leak. Then, with only the lower heater operating in this manner, the thermistor 42 on the upper heater side
When the failure of the lower heater is detected based on the temperature detection result obtained by, and as a result, it is detected that there is no abnormality in the lower heater, the print signal can be received. Next, when the print signal is turned on (step S2), the temperature of the nip portion at that time is detected at the same time when the print signal is received, and a target temperature adjustment temperature predetermined by experiment is selected according to the value. (Step S3). If the detected temperature is lower than the saturation temperature 100 ° C. of the pressure roller 31,
It is determined that the start-up is in the initial stage, and the upper heater is heated with full power while rotating the fixing film 39 and the pressure roller 31 in accordance with the detected temperature (step S4). I will change it as follows). That is, the detected temperature is 0-10
In the case of ℃, the pre-multi-rotation time is 90 seconds, then 10 ℃
The temperature is shortened by 10 seconds each time the temperature rises, and fixed at 10 seconds when the temperature is 90 ° C. or higher (step S5).

Next, it is judged whether or not the desired fixing temperature of 180.degree. C. has been reached (step S6), and when the desired fixing temperature is reached, sheet feeding (step S7) to unfixed image formation (step S8) and fixing (step S9). ), A series of printing operations are performed to discharge the paper (step S10), and after discharging, the temperature control mode of the upper heater is set to the paper-interval temperature control mode (step S11), and then the counting of the paper-interval time is started. (Step S12).

If the time from the discharge of paper to the reception of the next print signal is longer than the predetermined time of 5 minutes,
It is determined that the upper heater is turned on and the energization of the upper heater is stopped (steps S13 to S14), and only the lower heater is turned on and waits for the next printing. On the other hand, when the time from the discharge of the paper to the reception of the next print signal is shorter than the predetermined time of 5 minutes, it is considered that the print period is in progress, and the temperature control temperature is set in advance according to the print time interval and the cumulative number of sheets. Is set and the printing operation is continued (step S15).

An example of temperature control according to the above flow chart is shown in FIG. In the graph above,
The rising characteristics of the fixing film 39 alone and the lower roller 31 alone are shown by thin lines, and the temperature locus of the nip portion is shown by thick lines. As shown in the figure, since the print signal is input immediately after the device is started and the lower heater is energized at the same time when the power is turned on, the upper heater is also energized.
Start-up faster than 0 minutes has been realized.

When the temperature of the nip portion reaches the fixing temperature during the starting of the lower roller, the energizing time of the upper heater (actually, finer ON / OFF control is performed within this period). 3) requires a longer time than the energization time of the upper heater in the case of fixing after the rising of the lower roller as shown in the timing chart of FIG. 3A. This is as shown in FIG. 3B. In addition, the results are changed according to the four-step set temperatures provided in the graph of the upper heater target temperature with respect to the number of passed sheets. In addition, even when the start-up is the same, at the time of start-up after a rest period, such as when the lower roller temperature is fully saturated and then start-up, the energizing time of the upper heater becomes shorter and the target temperature becomes lower. There is.

The start-up time at the time of continuous paper feeding using the above-mentioned control is such that the heat capacity of the fixing film is lower than that of the conventional fixing roller, and further, the heating of the pressure roller side assists the four-color Compared to the paper interval time during continuous printing in a color image forming apparatus that repeats the development and transfer steps, the time can be shortened sufficiently, and the amount of heat lost during one print can be fixed as well as fixing after the temperature stabilizes. Since the responsiveness of the heat supply for supplementing is also fast, it is easy to cause problems when using a fixing roller with a large heat capacity even when performing continuous printing. In this embodiment, the high-precision control can be realized by one detecting means, and a safety device in case the heater goes out of control is provided only on the fixing side. There.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIGS.
The same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 4 is a sectional view of a fixing device of a color image forming apparatus showing a second embodiment of the present invention. In FIG. 4, members having the same numbers as those in FIG. 1A indicate the same constituent elements. In the present embodiment, the pressure roller side heater can heat the pressure roller surface temperature to the fixing temperature or higher, and the start-up time can be increased. Conventional halogen heater for pressure roller 28 'which becomes faster
Is used.

In this embodiment, by using this high-output lower heater and performing control according to the flowchart shown in FIG. 5, a single thermistor on the upper heater side provides high accuracy,
In addition, it realizes a color fixing device that can be started up at a higher speed.

In the control of the present embodiment according to the flowchart of FIG. 5, the steps from the power-on to the temperature control target temperature determination by the first temperature detection (steps S1 to S3) are the same as those of the first embodiment, but In the embodiment, the temperature of the lower roller itself is rapidly increased thereafter, and the target temperature of 130 ° C. can be reached in 2 minutes. Therefore, it is not necessary to change the previous multi-rotation time after receiving the print signal, and the lower roller is 130 ° C. By heating with full power until the temperature reaches ℃ (Step S
20 to S22), it can be started up in about 10 seconds.

Then, the lower heater after reaching the target temperature is in the low output mode at the same level as the heat leak as in the first embodiment (ON / OFF time in which a ratio of a predetermined OFF time is increased). (Fixed to fixed ratio) (step S23), the subsequent heater control is stopped, and at the same time the upper heater is started up with full power according to the print signal (step S24), and the nip temperature is changed from 130 ° C. to the fixing temperature 180. The temperature is raised to ℃ (step S25).

After that, one fixing process is completed through the image forming process similar to that of the first embodiment (step S26).
(S31), if it is shorter than the predetermined waiting time T0 according to the length of the paper interval time to the next printing, it is considered to be during the printing period and the target temperature is determined again, and if it is longer than T0, the rest period is entered. Judge that the heaters are on and off
FF is performed (steps S32 to S34), and when the paper interval time count value becomes longer than 5 minutes and the predetermined temperature H2 shown in FIG.
The residual heat on the side of the fixing film is sufficiently radiated, and it is determined that the detected temperature matches the lower roller surface temperature, the control of the lower roller temperature is restarted, and the lower roller temperature is maintained (step S
35-S3).

FIG. 6A shows the time variation of the temperature around the nip portion of the fixing device controlled according to the above flow chart. In this embodiment, the starting speed is set by the high-power lower heater. Since the speed is increased, the temperature of the pressure roller side is always maintained at the predetermined temperature of 130 ° C. at the time of fixing, and the lower roller temperature at the time of fixing can be made higher than that of the first embodiment. The number of sheets to be switched can be reduced as shown in FIG. 6 (B).

Further, in this embodiment, as a means for preventing excessive temperature rise provided in the fixing device, a thermal fuse 44 having a melting temperature of 230 ° C. is brought into contact with the back surface of the substrate of the ceramic heater. Since the wires are connected as shown in FIG. 7, when the heater on the fixing side abnormally heats up, the temperature fuse 44 is blown to cut off the electric circuit, and also when the heater on the pressure roller side abnormally heats up. Since the abnormal temperature is transmitted to the back of the ceramic substrate via the fixing nip portion, the temperature fuse 44 is also blown and the temperature rise can be avoided.

As described above, by using this embodiment, the power consumption of the pressure roller side heater is increased by increasing the output and the low standby temperature of the pressure roller during the rest period. It is possible to reduce the electric power with only one temperature detecting means, and it is possible to prevent runaway of the upper and lower heaters with a single temperature fuse on the fixing side, which enables a low-cost safety design.

(Third Embodiment) Next, a third embodiment of the present invention will be described with reference to FIG. The first
The same parts as those of the above embodiment are designated by the same reference numerals and the description thereof will be omitted.

FIGS. 8A, 8B, and 8C are a sectional view of a fixing device, a fixing film thereof, and a heating means sectional view of a color image forming apparatus showing a third embodiment of the present invention.
In FIG. 1A, members having the same numbers as those in FIG. 1 indicate the same constituent elements, and in the present embodiment, a heating plate type electromagnetic induction heater 41 'is used as the heating means instead of the above ceramic heater. .

As shown in FIG. 6C, the structure is such that a coil 43 is wound around a U-shaped ferrite core 41'a and a magnetic metal plate 41'b having good heat conductivity is brought into contact with it. There is. Further, in the present embodiment, a wax toner (not shown) in which a highly releasable wax is included is used inside the toner, and the function of this toner eliminates the need to apply oil to the fixing roller, thereby applying oil. The mechanism is omitted. This heater can raise the temperature of the magnetic metal sheet uniformly and rapidly by passing an alternating current at a frequency of several tens to several hundreds of kHz of the coil, and has a thermal conductivity higher than that of the ceramic heater. Since this can be made extremely high, by using the present heater in each of the above-described embodiments, the heat transfer on the pressure roller side can be transmitted at a higher speed, and the response of the detection means and the accuracy of control can be improved. . In addition, since there is no oil application mechanism, downsizing and cost reduction are possible, and because there is no oil in the fixing nip, the effect of the heat capacity of the oil itself and the oil surface from the roller surface while the oil circulates between the upper and lower rollers The influence of the amount of heat taken away disappears,
The accuracy of temperature detection and the start-up characteristics of the fixing device are further improved.

(Fourth Embodiment) Next, a fourth embodiment of the present invention will be described with reference to FIG. The first
The same parts as those of the above embodiment are designated by the same reference numerals and the description thereof will be omitted.

FIGS. 9A, 9B, and 9C are a sectional view of a fixing device, a fixing film thereof, and a heating means sectional view of a color image forming apparatus showing a fourth embodiment of the present invention. . In FIG. 9 (A), the members having the same numbers as those in FIG. 8 indicate the same components, and in the present embodiment, a metal film type electromagnetic induction heater 41 ″ is used as the heating means instead of the heating plate type electromagnetic induction heater. Is used.

The structure of the film is, as shown in FIG. 7B, on the surface of the magnetic metal film 39'c having a thickness of about 50 μm, as shown in FIG.
The coil 43 is wound around a and the metal film itself is heated by generating an alternating magnetic field inside the metal film. The heat capacity can be further reduced as compared with the heater of the third embodiment. If it comes into direct contact with the back surface of the film in the nip part, local pressure and heat capacity unevenness will occur in the nip part, and the image quality change will appear sensitively to these changes. In the present embodiment, a thermistor is provided on the pressure roller side, and it is necessary to control the temperature of the upper and lower heaters by this one thermistor. Therefore, as the heater on the pressure roller side, a low temperature is required as in the first embodiment. Power halogen heater 28 "
Control of the lower heater is omitted, and the position of the thermistor that contacts the surface of the pressure roller is fixed near the downstream of the nip within the range that does not interfere with paper ejection, and when the upper heater heats up, it is transmitted from the upper heater. The temperature change of the lower roller surface, which rises due to the amount of heat generated, is monitored, and the conversion result obtained by inputting it into the conversion formula obtained from the correlation between the upper heater temperature and the lower roller surface temperature change measured in advance is used in reverse. A method of estimating and controlling the heater temperature is used.

[0066]

As described above, the first embodiment according to the present application is described.
According to the invention, since a heat-resistant film having a small heat capacity and an elastic layer is used on the surface in contact with the color toner as the fixing means for forming a color image, it is faster than the conventional fixing roller using thick rubber. Since the startup can be realized and the responsiveness can be improved at the same time, stable temperature control can be performed by the temperature detection means provided on the heat resistant film side, and good color image formation can be performed. You can Further, since the temperature detecting means may be provided only on the heat resistant film side, the cost can be reduced by reducing the number of parts.

According to the second aspect of the present invention,
The heat-resistant film of the first invention is a film in which a heat-resistant thin elastic layer and a heat-resistant release layer are laminated in this order on a film base layer, and the film-side heating element is a ceramic in which a heating element is formed on a ceramic substrate. Since it is a heater and the pressure member is a pressure roller that has a thick heat-resistant elastic layer on the core metal, the heat-resistant film and the elastic layer of the pressure roller fix the unfixed color image with severe unevenness. It is possible to sufficiently dissolve and mix colors in the nip portion, and it is possible to realize quick start-up due to the heat resistant film having a low heat capacity and the ceramic heater.

Further, according to the third invention of the present application, the pressure side heating element included in the pressure member of the first invention or the second invention is fixed even if it is continuously driven at the maximum output. It is a low output heater that saturates at a temperature well below the temperature,
Since the temperature of the pressure member is detected by the temperature detecting means only during the start-up period from the room temperature to the saturation temperature, the start-up time can be shortened, and the above-mentioned addition can be performed based on the result of the temperature detection. Since the failure of the pressure side heating element is judged, safety can be ensured. Further, the cost can be reduced by reducing the number of parts. Also,
When the image forming operation start signal is received during the start-up period, the film-side heating element is driven at the maximum output while rotating the heat resistant film and the pressure member according to the temperature detection result at the time of reception. By adjusting the time to raise the film-side heating element to a desired fixing temperature, it is possible to shorten the start-up time during continuous image forming operations by assisting the heating from the pressure member side. At the same time, it is possible to improve the responsiveness of the heat quantity supply for compensating for the heat quantity taken by the transfer material by the fixing operation, and it is possible to reliably prevent the decrease in the fixability and the glossiness due to the temperature decrease.

According to the fourth invention of the present application,
The pressurizing-side heating element included in the pressurizing member of the first invention or the second invention is a high-output heater that rises to a temperature sufficiently higher than the fixing temperature when continuously driven at the maximum output. The temperature control of the member is performed so as to maintain a predetermined temperature based on the temperature detection result of the temperature detecting means until the image forming operation start signal is received, and is absorbed by the transfer material after the image forming operation start signal is received. Since it is performed so as to reduce the amount of heat to be supplemented, it is possible to reduce the power consumption while assisting the heating from the pressure member to shorten the startup time and improve the responsiveness of the heat supply. . Also,
The temperature control of the film-side heating element is performed by selecting a predetermined target temperature according to the temperature detection result when the image forming operation start signal is received and starting heating, and according to the number of transfer materials to be image-formed in advance. Since it is performed so as to sequentially switch to a plurality of predetermined target temperatures, it is possible to maintain stable and good fixability in continuous image forming operations.

Further, according to the fifth invention of the present application, the film side heating body of the fourth invention is provided with an excessive temperature rise preventing means, and the excessive temperature rise preventing means is provided on the pressurizing side. Since it also functions as an excessive temperature rise prevention means for the heating body, one excessive temperature rise prevention means can prevent runaway of the heating body on the film side and the pressurizing side, and can reduce costs by reducing the number of parts. it can.

According to the sixth invention of the present application,
Since the film-side heating body according to any one of the first to fourth inventions is a heater that heats a magnetic metal plate having good thermal conductivity using an electromagnetic induction heating method, it has a higher thermal conductivity than a ceramic heater. It is possible to realize high temperature, high-speed heat transfer, improve the responsiveness of the temperature detecting means, and improve the control accuracy.

Further, according to the seventh invention of the present application, the temperature detecting means is provided on the pressurizing member side even when the method of heating the metal film by electromagnetic induction heating is used.
Since the control is performed based on the correlation between the change in the surface temperature of the pressure member and the temperature of the film side heating element, accurate temperature control should be performed even if local pressure or temperature unevenness occurs in the fixing nip part. You can

According to the eighth invention of the present application,
In any one of the first to seventh inventions described above, as a means for preventing the fixing offset by enhancing the releasing property of the toner from the surface of the heat resistant film and the pressing member at the time of fixing, the releasing agent is released inside the toner. Since the toner containing the property-improving wax is used, the heat leak factor is reduced, and the rise time can be shortened and the temperature detection accuracy can be improved as compared with the conventional method using the oil application mechanism.

[Brief description of drawings]

1A is a sectional view of a color fixing device according to a first embodiment of the present invention, FIG. 1B is a sectional view of a film, and FIG. 1C is a sectional view of a heater.

FIG. 2 is a flow chart diagram in the first embodiment of the present invention.

FIG. 3A is a temperature control history graph and a timing chart thereof in the first embodiment of the present invention, and FIG. 3B is a temperature control target temperature relationship graph with the number of passed sheets.

FIG. 4 is a sectional view of a color fixing device showing a second embodiment of the present invention.

FIG. 5 is a flow chart diagram in the second embodiment of the present invention.

FIG. 6A is a temperature control history graph and a timing chart thereof in the second embodiment of the present invention, and FIG. 6B is a graph showing the relationship between the number of passed sheets and the temperature control target temperature.

FIG. 7 is a conceptual diagram of an electric circuit of a heater that represents a second embodiment of the present invention.

8A is a sectional view of a color fixing device according to a third embodiment of the present invention, FIG. 8B is a sectional view of a film, and FIG. 8C is a sectional view of a heater.

9A is a sectional view of a color fixing device according to a fourth embodiment of the present invention, FIG. 9B is a sectional view of a film, and FIG. 9C is a sectional view of a heater.

FIG. 10 is a sectional view of a conventional color image forming apparatus.

FIG. 11 is an enlarged cross-sectional view of the inside of a developing device used in a conventional color image forming apparatus.

FIG. 12 is a sectional view of a fixing device used in a conventional color image forming apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Photosensitive drum (image carrier) 10 Transfer roller (transfer means) 25 Fixing device (fixing means) 28 'Pressurizing halogen heater (pressurizing side heating element, high output heater) 28 "Low power halogen heater (pressurizing side heating element, Low output heater) 29 Aluminum core (core of pressure member) 31 Pressure roller (Pressure member) 31a Silicone rubber for pressure application (heat resistant elastic layer) 32 Thermistor (temperature detection means) 39 Fixing film (heat resistance Film) 39a Surface release layer (heat resistant release layer) 39b Silicone rubber layer (heat resistant thin elastic layer) 39c Polyimide film (film base layer) 41 Ceramic heater (film side heating element) 41a Ceramic substrate 41b Heating element 41 'Heating plate type electromagnetic induction heating heater (heater using electromagnetic induction method) 41'b Magnetic metal plate 41 "Metal film Type electromagnetic induction heating heater (heater using electromagnetic induction method) 42 Thermistor (temperature detection means)

Claims (8)

[Claims] 1. A color image in which a color toner image formed on an image bearing member is transferred onto a transfer material by a transfer means, and then heat and pressure are applied to the color toner image by a fixing means to fix the color toner image on the transfer material. In the forming apparatus, the fixing unit includes a heat-resistant film having a small heat capacity, which has an elastic layer disposed on a side in contact with an image surface of an unfixed color toner when heat and pressure are applied to the transfer material; A film side heating element having a low heat capacity arranged so as to be in sliding contact with the surface of the heat-resistant film opposite to the contact side with the image surface, and arranged so as to be in pressure contact with the heating element through the heat resistant film. The pressing member having the elastic layer provided, the pressing-side heating member included in the pressing member, and the sliding contact surface side of the film-side heating member with the heat-resistant film are provided on the opposite side. Equipped with a temperature detecting means The temperature control of the film side heating body and the pressure member is performed based on the temperature of the film side heating body and the pressure member detected by the temperature detecting means. 2. The heat resistant film is a film in which a heat resistant thin elastic layer and a heat resistant release layer are laminated in this order on a film base layer, and the film side heating element is a ceramic heater having a heating element formed on a ceramic substrate. 2. The color image forming apparatus according to claim 1, wherein the pressure member is a pressure roller having a thick heat-resistant elastic layer on the cored bar. 3. The pressure-side heating element contained in the pressure member,
It is a low output heater that saturates to a temperature sufficiently lower than the fixing temperature even if it continues to be driven at the maximum output, and the temperature detection of the pressure member by the temperature detection means is performed only during the startup period from room temperature to the saturation temperature. When the failure of the pressurizing side heating element is judged based on the result of the temperature detection and the image forming operation start signal is received during the start-up period,
While rotating the heat resistant film and the pressure member according to the temperature detection result at the time of reception, the drive time of the film side heating element at the maximum output is adjusted to raise the film side heating element to the desired fixing temperature. The color image forming apparatus according to claim 1, wherein 4. The pressure-side heating element contained in the pressure member,
It is a high-output heater that keeps operating at the maximum output, and the temperature rises to a temperature sufficiently higher than the fixing temperature.The temperature control of the pressure member is based on the temperature detection result of the temperature detection means until the image forming operation start signal is received. It is performed so as to maintain a predetermined temperature on the basis of, and after the image forming operation start signal is received, the amount of heat absorbed by the transfer material is reduced to a level that can be supplemented.
The temperature control of the film-side heating element is performed by selecting a predetermined target temperature according to the temperature detection result when the image forming operation start signal is received and starting heating, and according to the number of transfer materials to be image-formed in advance. The color image forming apparatus according to claim 1, wherein the color image forming apparatus is configured to sequentially switch to a plurality of predetermined target temperatures. 5. The film side heating element is provided with an excessive temperature rise prevention means, and the excessive temperature rise prevention means also functions as an excessive temperature rise prevention means of the pressure side heating body. Color image forming apparatus. 6. The film-side heating body is a heater for heating a magnetic metal plate having good thermal conductivity by using an electromagnetic induction heating method, according to any one of claims 1 to 4. Color image forming apparatus. 7. A color image in which a color toner image formed on an image bearing member is transferred onto a transfer material by a transfer means, and then heat and pressure are applied to the color toner image by a fixing means to fix the color toner image on the transfer material. In the forming apparatus, the fixing means is disposed on the side in contact with the image surface of the unfixed color toner when the heat and pressure are applied to the transfer material, and the heat-resistant thin elastic layer and heat-resistant release property are provided on the surface of the magnetic metal film. The heat-resistant film in which the layers are laminated in this order and the heat-resistant film are arranged so as to be in sliding contact with the surface of the heat-resistant film opposite to the contact side with the image surface, and the magnetic metal film is heated by the electromagnetic induction heating method. A film-side heating element, a pressure member having a thick heat-resistant elastic layer on a core bar, which is disposed so as to be in pressure contact with the heating element through the heat-resistant film, and the pressure member includes Driven with maximum output A low-output pressure-side heating body that saturates at a temperature sufficiently lower than the fixing temperature even if it continues to move, and a temperature detecting means provided so as to contact the pressure-applying member. The temperature control of the member is based on the correlation between the change in the surface temperature of the pressure member obtained in advance and the temperature of the film-side heating body, and the surface temperature of the pressure member obtained by the temperature detecting means. And a temperature on the side of the film rotator is estimated from the change of the temperature. 8. A toner in which a releasing property improving wax is included in the toner is used as a means for preventing the fixing offset by enhancing the releasing property of the toner from the surface of the heat resistant film and the pressure member during fixing. The color image forming apparatus according to any one of claims 1 to 7.