JPH11194656A - Fixing device and image forming apparatus provided with the fixing device - Google Patents

Abstract

(57) An object of the present invention is to provide a fixing device capable of easily suppressing an excessive temperature rise of a pressure body during a continuous fixing process on a plurality of recording media, or an image forming apparatus including the fixing device. It is intended to provide a device. SOLUTION: In a continuous fixing process for a plurality of N recording media, the target temperature of the ceramic heater 15 from the end of the fixing process of the Mth recording medium to the start of the fixing process of the (M + 1) th recording medium. The inter-sheet temperature is set lower than the fixing temperature, which is the target temperature of the ceramic heater 15 during the fixing process of the Mth recording medium, and the difference between the fixing temperature and the inter-sheet temperature is determined by the size, type, and thickness of the recording medium. And at least one of the temperature inside and outside the main body of the fixing device 7 is set.

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 sheet-shaped recording medium carrying an unfixed image to the recording medium by heating and pressurizing, and an image forming apparatus having the fixing device. is there.

[0002]

2. Description of the Related Art Conventionally, as the fixing device,
Heating means while passing a recording medium carrying an unfixed image in a nip portion formed between an endless belt-shaped film serving as a fixing member and a cylindrical rotatable pressure roller serving as a pressing member pressed against each other. JP-A-63-313182 and the like disclose a mode in which a fixing process step of heating by a barrel ceramic heater is performed.

The ceramic heater provided in the fixing device has a heating resistor provided on one surface of a thin substrate mainly composed of ceramics, which generates heat by being supplied with electricity from a commercial power supply. A thermistor temperature sensing sensor (hereinafter, abbreviated as a thermistor) serving as a temperature detecting body is disposed in contact with the other surface.

That is, in the fixing device, energization from the commercial power supply to the heating resistor is controlled so that the detected temperature of the thermistor falls within a predetermined range from the target temperature.

Next, the temperature control of the ceramic heater in the process of continuously processing a plurality of transfer materials in the fixing device will be described with reference to FIG.

FIG. 11 is a graph showing a change in the temperature detected by the thermistor over a continuous processing step for a plurality of transfer materials.

First, when the operation of the fixing device is stopped for about 5 to 6 hours, the main body of the fixing device and various devices supported by the main body have cooled down to room temperature or almost room temperature. The temperature detected by the thermistor indicates a temperature a that matches or almost matches room temperature.

Next, as the image forming apparatus including the fixing device starts an image forming process on a series of N recording media, a current supply from the commercial power supply to the heating resistor is started. Thus, the temperature detected by the thermistor rises from temperature a to temperature b and temperature c.

Therefore, the detected temperature of the thermistor is raised to a fixing temperature d by the time immediately before the time T1 at which the first recording medium carrying the unfixed image enters the nip portion, and the fixing process is performed on the recording medium. The power supply from the commercial power supply to the heating resistor is controlled such that the detected temperature is maintained at a value within a predetermined range from the temperature d from time T1 to time T2, which is a period during which the process is performed.

Next, during the period from the end of the fixing processing of the first recording medium to the start of the fixing processing of the second recording medium, as disclosed in JP-A-6-149103, the temperature d The power supply from the commercial power supply to the heating resistor is controlled to maintain the temperature detected by the thermistor within a predetermined range from the temperature e, which is a lower inter-sheet temperature, which is a lower value.

In the following, the difference between the fixing temperature and the sheet-to-sheet temperature over the continuous fixing process is reduced uniformly while the set value of the fixing temperature is reduced every time the number of recording mediums subjected to the fixing process reaches a predetermined value. By keeping this, the power consumption of the ceramic heater is reduced, and the excessive temperature rise in the non-sheet passing area such as the outer peripheral surface of the pressure roller is achieved.

[0012]

However, in the fixing device, regardless of the size, type, thickness, etc. of the recording medium, the fixing temperature and the fixing temperature are continuously changed over a plurality of N recording media. The difference from the sheet-to-sheet temperature is taken uniformly.

Therefore, depending on the size, type, thickness, etc. of the recording medium to be subjected to the continuous fixing process, the pressure is applied from the end of the fixing process of the Mth recording medium to the start of the fixing process of the (M + 1) th recording medium. There is a possibility that excessive temperature rise in the non-sheet passing area such as the outer peripheral surface of the roller may not be sufficiently eliminated.

Therefore, it is necessary to improve the heat resistance of the pressure roller and the like as a countermeasure against the above-mentioned fear, so that there is a problem that the cost of the pressure roller and the like is increased.

Accordingly, the present invention provides a fixing device or a fixing device capable of suppressing an excessive temperature rise in a non-sheet passing area such as a pressure member during a continuous fixing process on a plurality of recording media without increasing the cost. It is an object to provide an image forming apparatus including a fixing device.

[0016]

According to the present invention, an object of the present invention is to provide a sheet-like recording medium carrying an unfixed image formed by a nip formed between a fixing member and a pressing member pressed against each other. A fixing device for heating the recording medium by a heating unit while passing the sheet through a unit, comprising a temperature detector for detecting the temperature of the heating unit, and M in a process for continuously fixing a plurality of N recording media. M + from the end of the fixing process of the recording medium
The inter-sheet temperature, which is the target temperature of the heating unit until the fixing process of the first recording medium is started, is set lower than the fixing temperature, which is the target temperature of the heating unit during the fixing process of the Mth recording medium. In the fixing device, the difference between the fixing temperature and the inter-sheet temperature is set according to at least one of the size, type, and thickness of the recording medium and the temperature inside or outside the main body of the fixing device. This is achieved by the invention.

Further, according to the present application, the object is that the M-th recording medium and M + 1
A second invention in which the distance between the sheets, which is the distance between the sheet and the recording medium, is set according to at least one of the size, type, and thickness of the recording medium and the temperature inside or outside the main body of the fixing device. Is also achieved by

Further, according to the present application, the above object is achieved in the first invention or the second invention according to the present application, wherein the fixing of the (M + 1) th recording medium from the end of the fixing processing of the Mth recording medium is completed. The inter-sheet temperature in the inter-sheet interval until the start of the process is set to a plurality of values according to the temperature increase rate of the temperature detected by the temperature detector within a specified time until the Mth recording medium enters the nip portion. The present invention is also achieved by the third invention in which the inter-sheet temperature is switched stepwise over the inter-sheet period from a low value to a high value among the set values according to the temperature increase rate. You.

Further, according to the present application, the above object is achieved in any one of the first invention to the third invention according to the present application, wherein the fixing temperature is determined by the size, type, thickness and fixing of the recording medium. The present invention is also achieved by the fourth invention in which the temperature is set according to at least one of the temperature inside or outside the main body of the device.

Further, according to the present application, the above object is achieved in any one of the first to fourth inventions according to the present application, wherein the set value of the fixing temperature is set to the value of the recording medium after the fixing process. This is also achieved by the fifth invention in which the number decreases as the number of sheets increases.

Further, according to the present application, the above object is achieved in any one of the first to fifth inventions according to the present application, wherein the heating means is a thin plate-shaped substrate mainly composed of ceramics. A heating resistor is provided on one surface of the substrate and generates a heat by receiving electricity from a commercial power supply, and a temperature detector is disposed on the other surface of the substrate in contact with the heating resistor. The present invention is also achieved by the sixth invention in which the endless belt-like film is pressed against the one surface by a pressure member via a recording medium carrying an unfixed image.

Further, according to the present application, the object is to form an image forming apparatus comprising: a fixing device according to the first invention of the present application; and an energization control unit that controls energization from a commercial power supply to a heating unit. In the apparatus, the difference between the fixing temperature and the inter-sheet temperature is a value set according to at least one of the size, type, and thickness of the recording medium and the temperature inside or outside the main body of the fixing device. The present invention is also achieved by the seventh invention in which the power supply control means controls the power supply from the commercial power supply to the heating means.

Further, according to the present application, the above object is achieved by the seventh invention according to the present application, wherein the M-th recording medium and M + 1
An eighth aspect of the invention is that the distance between the sheets, which is the interval between the sheet and the recording medium, is set according to at least one of the size, type, and thickness of the recording medium and the temperature inside or outside the main body of the fixing device. Is also achieved by

Further, according to the present application, the above object is achieved in the seventh or eighth invention according to the present application, wherein the fixing of the (M + 1) th recording medium after the completion of the fixing processing of the Mth recording medium is completed. The inter-sheet temperature in the inter-sheet interval until the start of the process is set to a plurality of values according to the temperature increase rate of the temperature detected by the temperature detector within a specified time until the Mth recording medium enters the nip portion. The present invention is also achieved by a ninth invention in which the sheet interval temperature is switched stepwise over the sheet interval from a low value to a high value among the set values according to the temperature increase rate.

Further, according to the present application, the above object is achieved in any one of the seventh to ninth inventions according to the present application, wherein the set value of the fixing temperature is: The present invention is also achieved by the tenth invention in which the setting is made in accordance with at least one of the size, type, thickness, and the temperature inside or outside the main body of the fixing device.

Further, according to the present application, the object is reduced with an increase in the number of fixed recording media in any one of the seventh to tenth inventions according to the present application. This is also achieved by the eleventh invention.

Further, according to the present application, the above-mentioned object is achieved according to any one of the seventh to eleventh inventions according to the present application, wherein the heating means comprises a thin plate mainly composed of ceramics. A heating resistor is provided on one surface of the substrate to generate heat when supplied with electricity from a commercial power supply, and a temperature heater is disposed in contact with a temperature detector on the other surface of the substrate. The invention is also achieved by a twelfth invention in which the film is an endless belt-shaped film which is pressed against the one surface by a pressure member via a recording medium carrying an unfixed image.

That is, according to the first invention of the present application, the distance between the M-th recording medium and the (M + 1) -th recording medium is the size, type, thickness, and fixing device of the recording medium. Is set according to at least one of the internal and external temperatures of the main body.

In the second invention according to the present application,
The difference between the fixing temperature and the sheet temperature is set according to at least one of the size, type, and thickness of the recording medium and the temperature inside or outside the main body of the fixing device.

In the fourth invention according to the present application,
The fixing temperature is set according to at least one of the size, type, and thickness of the recording medium and the temperature inside or outside the main body of the fixing device.

Further, in the third invention according to the present application, the sheet-to-sheet temperature in the sheet-to-sheet period from the end of the fixing processing of the Mth recording medium to the start of the fixing processing of the (M + 1) th recording medium is:
After a plurality of values are set in accordance with the temperature increase rate of the temperature detected by the temperature detector within a specified time until the Mth recording medium enters the nip portion, a set value corresponding to the temperature increase rate is set. The inter-sheet temperature is switched stepwise from the low value to the high value over the inter-sheet period.

Further, in the fifth invention according to the present application, the set value of the fixing temperature decreases as the number of recording media subjected to the fixing process increases.

In the sixth invention according to the present application,
The recording medium carrying the unfixed image is heated by a ceramic heater via the film while being passed through a nip formed between the film and the pressure member pressed against each other.

Further, in the seventh invention according to the present application, the difference between the fixing temperature and the sheet-to-sheet temperature is the size of the recording medium,
The energization control unit controls energization from the commercial power supply to the heating unit so that the value becomes a value set according to at least one of the type, thickness, and the temperature inside or outside the main body of the fixing device.

In the eighth invention according to the present application,
The distance between the Mth recording medium and the (M + 1) th recording medium is set in accordance with at least one of the size, type, and thickness of the recording medium and the temperature inside or outside the fixing device main body. Is done.

Further, in the ninth invention according to the present application, the sheet interval temperature in the sheet interval from the end of the fixing process of the Mth recording medium to the start of the fixing process of the (M + 1) th recording medium is as follows:
After a plurality of values are set in accordance with the temperature increase rate of the temperature detected by the temperature detector within a specified time until the Mth recording medium enters the nip portion, a set value corresponding to the temperature increase rate is set. The inter-sheet temperature is switched stepwise from the low value to the high value over the inter-sheet period.

In the tenth invention according to the present application,
The fixing temperature is set according to at least one of the size, type, and thickness of the recording medium and the temperature inside or outside the main body of the fixing device.

Further, in the eleventh invention according to the present application, the set value of the fixing temperature decreases with an increase in the number of recording media having undergone the fixing process.

In the twelfth invention according to the present application, a recording medium carrying an unfixed image is passed through a nip formed between a film and a pressure member pressed against each other. While being heated by the ceramic heater through the film.

[0040]

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

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

FIG. 1 is a schematic cross-sectional view showing a schematic configuration of a laser beam printer 1 (hereinafter abbreviated as printer 1), which is a preferred example of the image forming apparatus of the present embodiment.

The printer 1 forms an image on a sheet-shaped recording medium P in accordance with image information provided from an image information providing device (not shown) such as a host computer provided outside the main body of the printer 1. This is an image forming apparatus in which a series of image forming processes of recording is performed according to a known electrophotographic method.

As shown in FIG. 1, the printer 1 includes a drum-shaped rotatable photosensitive member 2 as a latent image carrier and a process cartridge 4 for holding a developing device 3 and a process cartridge 4 for storing image information from an image information providing device. A transfer process is performed on the recording medium P, and a laser scanner unit 5 (hereinafter, abbreviated as a scanner 5) that forms an electrostatic latent image corresponding to the image information on the outer peripheral surface of the photoconductor 2 by an appropriate exposure process. The image forming apparatus includes a roll-shaped rotatable transfer member 6 and a fixing device 7 for performing a fixing process on the recording medium P after the transfer process by applying heat and pressure.

The process cartridge 4 provided in the printer 1 includes, in addition to the photosensitive member 2 and the developing device 3, a primary charging mechanism 8 for charging the outer peripheral surface of the photosensitive member 2 to a specified potential distribution before the exposure process by the scanner 5. And is detachably supported by the main body of the printer 1. When maintenance such as repair of the photoconductor 2 and replenishment of the developer to the developing device 3 is required, the main body can be freely opened and closed by the main body. After the supported cover 9 is opened, the entire process cartridge 4 is replaced to speed up and simplify maintenance.

The primary charging mechanism 8 held in the process cartridge 4 charges the outer peripheral surface of the photoreceptor 2 to a specified potential distribution by applying a specified bias from a commercial power supply or the like before the exposure processing step by the scanner 5. It has become.

The scanner 5 provided in the printer 1 is driven by a laser La corresponding to a time-series electric digital pixel signal of image information from the image information providing device through a window provided in the main body of the process cartridge 4. By scanning and exposing a charged portion of the outer peripheral surface of the photoconductor 2 and exposing the same, an electrostatic latent image corresponding to the image information is formed on the portion.

Next, a series of image forming processes in the printer 1 will be described.

First, a start button or the like (not shown) provided on the main body of the printer 1 is pressed to instruct the printer 1 to start a series of image forming processes.
The photoreceptor 2 starts rotating at a specified peripheral speed in the direction of arrow K1, and the outer peripheral surface of the photoreceptor 2 is charged to a specified potential distribution by a primary charging mechanism 8 to which a specified bias is applied.

Next, the charged portion of the outer peripheral surface of the photoreceptor 2 is scanned and exposed by the scanner 5 according to the image information from the image information providing device, so that an electrostatic latent image corresponding to the image information is obtained. Is formed on the portion, the electrostatic latent image is visualized into a visible image by the developer of the developing device 3, and the printer 1 can accommodate a predetermined number of recording media P.
The recording has been conveyed at a predetermined timing or the like from a cassette 11 detachably supported by the main body to a space formed between the photoreceptor 2 and the transfer body 6 by a rotatable paper feed roller 12 or the like. The visual image is transferred onto the medium P by the transfer body 6.

The recording medium P on which the transfer processing has been performed is subjected to fixing processing by the fixing device 7 and then discharged outside the apparatus by a discharge roller 13 rotatably supported by the main body of the printer 1. By stacking on the tray 14 attached to one side of the main body, a series of image forming processes is completed.

Next, the fixing device 7 provided in the printer 1
Will be described with reference to FIG. FIG. 2 is a schematic sectional view showing a schematic configuration of the fixing device 7.

As shown in FIG. 2, the fixing device 7 includes a ceramic heater 15 as a heating unit, an endless belt-like film 16 as a fixing member, and a cylindrical or substantially cylindrical rotatable pressure roller as a pressure member. 17 and a thermistor temperature sensing sensor 18 (hereinafter, abbreviated as the thermistor 18) as a temperature detecting body.

The ceramic heater 15 provided in the fixing device 7 includes a holder 19 attached to the main body of the fixing device 7.
Supported by

As shown in FIG. 3, the ceramic heater 15 is a thin substrate 15A mainly composed of alumina or the like.
A heating resistor 15 having Ag / Pd (silver palladium) or the like as a main component on one surface and having a thickness in the vertical direction of the paper of about 10 μm and a width in the horizontal direction of the paper of 1 to 3 mm.
B is provided on the other surface of the substrate 15A.
Are arranged in contact with each other, and the one surface is coated with a protective layer 15C mainly composed of glass or fluororesin so as to be protected from sliding contact with the film 16.

FIG. 3 is a partially transparent perspective view showing a schematic configuration of the ceramic heater 15.

As shown in FIG. 4, the heating resistor 15B constituting the ceramic heater 15 receives power from a commercial power supply 21 through a triac 20.
Thus, the heating resistor 15 that has been energized from the commercial power source 21
When B generates heat, heating by the ceramic heater 15 is performed.

FIG. 4 is a block diagram showing the connection relationship between the ceramic heater 15 and its peripheral means.

The film 16 provided in the fixing device 7 is
As shown in FIG. 2, the inner peripheral length of the fixing device 7 is longer than the outer peripheral length of the holder 19 by a predetermined length, for example, about 3 mm. The guide is guided in a predetermined direction by a holder while being driven by the rotation of a pressure roller 17 which is rotationally driven by a driving mechanism (not shown) provided outside the main body.

Therefore, the recording medium P carrying the unfixed image
Means that the unfixed image is melted and recorded by being heated by the ceramic heater 15 while being passed through the nip portion N formed between the film 16 and the pressure roller 17 pressed against each other. Become.

In the present embodiment, in order to improve the rate of temperature rise of the nip portion N and the like by lowering the heat capacity, the film 16 has an outer peripheral surface of an endless belt-like body mainly composed of polyimide. Has a two-layer structure in which an endless band mainly composed of PTFE is coated, and the total layer thickness is 1
The thickness is set to 00 μm or less.

The structure of the film 16 is not limited to the present embodiment. As another effective structure for reducing the heat capacity, for example, PTFE, PFA or FE which is a heat-resistant material is used.
A single-layer structure that is an endless band mainly composed of P or the like,
Alternatively, polyimide, polyamideimide, PEEK, P
There is a two-layer structure in which the outer peripheral surface of an endless band mainly composed of ES or PPS is coated with an endless band mainly composed of PTFE, PFA, FEP or the like.

The total thickness of the film 16 is not limited to this embodiment, but is preferably 100 μm or less, more preferably 20 μm or more and 50 μm or more in order to efficiently reduce the heat capacity.
μm or less is more preferable.

The pressure roller 17 provided in the fixing device 7
The outer peripheral surface of a cylindrical or substantially cylindrical rotatable core bar 17A mainly composed of aluminum or the like is covered with an elastic layer 17B mainly composed of silicone rubber or the like having good releasability. The core metal 17A is driven to rotate by receiving a driving force at an end in the roller axis direction.

Thermistor 18 provided in fixing device 7
Is connected to a CPU 23 as an energization control unit via an analog-to-digital conversion circuit 22 (hereinafter, abbreviated as an A / D conversion circuit 22) that digitizes and outputs input analog information, as shown in FIG. Have been.

The CPU 23 to which digital information corresponding to the temperature detected by the thermistor 18 is input controls the power supply from the commercial power supply 21 to the heating resistor 15B so that the temperature detected by the thermistor 18 becomes a value within a predetermined range from the target temperature. It is supposed to.

In this embodiment, the CPU 23 controls the energization of the heating resistor 15B from the commercial power supply 21 by generating heat from the commercial power supply 21 every half-wave period of the AC power output from the commercial power supply 21. Phase control for changing the phase range provided for energizing the resistor 15B in accordance with the temperature detected by the thermistor 18, or from the commercial power supply 21 in accordance with the temperature detected by the thermistor 18 for each half-wave period. Wave number control or the like in which energization to 15B is switched to either conduction or interruption is adopted.

Next, a fixing temperature (a target temperature of the ceramic heater 15 at the time of the fixing process of the Mth recording medium) in the process of continuously fixing a plurality of N recording media in the present embodiment, and The setting of the difference between the fixing temperature and the inter-sheet temperature (the target temperature of the ceramic heater 15 from the end of the fixing process of the Mth recording medium to the start of the fixing process of the (M + 1) th recording medium) will be described.

In this embodiment, as shown in FIG. 5, the size and basis weight (mass of the recording medium per unit area) of the recording medium subjected to the continuous fixing process are B5 or more and 60 g / m2, respectively. m ² or less, the difference between the fixing temperature and the sheet-to-sheet temperature over the continuous fixing process is 10 ° C.
On the other hand, when the size and basis weight of the recording medium are B5 or less and 60 g / m ² or more, respectively, the difference is set to 40 ° C.

FIG. 5 is a graph showing the transition of the temperature detected by the thermistor 18 in the continuous fixing process in this embodiment.

That is, when a recording medium of B5 or more and 60 g / m ² or less is subjected to the continuous fixing process, the difference between the fixing temperature and the sheet-to-paper temperature in the continuous fixing process is 10 ° C.
The CPU 23 from the commercial power supply 21
The power supply to 5B is controlled.

On the other hand, when a recording medium of B5 or less and 60 g / m ² or more is subjected to the continuous fixing process, the difference between the fixing temperature and the sheet-to-sheet temperature in the continuous fixing process is 40 ° C.
The CPU 23 from the commercial power supply 21
The power supply to 5B is controlled.

Next, the temperature control of the ceramic heater 15 in the process of continuously processing a plurality of recording media in this embodiment will be described with reference to FIG.

First, when the operation of the fixing device 7 is stopped for about 5 to 6 hours, the main body of the fixing device 7 and various devices supported by the main body have cooled down to room temperature or almost room temperature. , The detected temperature of the thermistor 18 indicates a temperature a which coincides with or substantially coincides with the room temperature.

Next, as the printer 1 starts an image forming process on a series of N recording media, the power supply from the commercial power supply 21 to the heating resistor 15B is started, and the thermistor 18 is turned on. The detected temperature rises from temperature a to temperature b and temperature c, and the difference between the fixing temperature and the sheet-to-sheet temperature over the continuous fixing process is 10 ° C. or Set to any value of 40 ° C.

Therefore, the detected temperature of the thermistor 18 is raised to the fixing temperature d by the time T1 at which the first recording medium carrying the unfixed image enters the nip portion N, and the fixing process is performed on the recording medium. From the commercial power supply 21 to the heating resistor 15B so that the detected temperature is maintained at a value within a predetermined range from the temperature d from time T1 to time T2, which is a period during which the heating is performed.
Is controlled.

Next, the size and basis weight of the recording medium subjected to the continuous fixing process are B5 or less and 60 g / m2, respectively.
When it is ² or more, the detection of the thermistor 18 from the temperature e, which is the sheet interval temperature, to a value within a predetermined width from the end of the fixing process of the first recording medium to the start of the fixing process of the second recording medium. Power supply from the commercial power supply 21 to the heating resistor 15B is controlled to maintain the temperature.

The difference between the fixing temperature and the sheet-to-sheet temperature over the continuous fixing process is uniformly reduced while the set value of the fixing temperature is reduced every time when the number of sheets of the recording medium subjected to the fixing process reaches a predetermined value. Kept at ° C.

Here, a comparison result performed by the inventor for confirming the effects and the like in the present embodiment will be described with reference to FIGS.

FIG. 6 as the present embodiment is a graph showing the temperature transition of the non-sheet passing area on the outer peripheral surface of the pressure roller 17 in the continuous fixing process in the present embodiment.

On the other hand, FIG. 7 as a comparative example shows that the difference between the fixing temperature and the sheet-to-paper temperature during the continuous fixing process is uniformly 10 ° C. regardless of the size and basis weight of the recording medium subjected to the continuous fixing process. Is a graph showing the temperature transition of the non-sheet passing area on the outer peripheral surface of the pressure roller 17 in the continuous fixing process step obtained by setting the value to "1", and corresponds to the conventional continuous fixing process step.

In the present embodiment, the temperature of the non-sheet passing area on the outer peripheral surface of the pressure roller 17 indicates a value within the range of 160 ° C. to 240 ° C. On the other hand, in the comparative example, Since the temperature of the non-sheet passing area on the outer peripheral surface of the pressure roller 17 indicates a value within the range of 180 ° C. to 260 ° C., according to the present embodiment, the temperature increase of the non-sheet passing area over the continuous fixing process is suppressed. Was obtained.

In the comparative measurement, an envelope having a size of B5 or less and a basis weight of 105 g / m 2 was used as a recording medium, and a temperature of 25 ° C. and a humidity of 45% were used.
In the environment of the above, the peripheral speed of the pressure roller is 24 mm / s
This was done by setting ec.

Therefore, in the present embodiment, the difference between the fixing temperature and the sheet-to-sheet temperature is set according to the size and thickness of the recording medium. It is possible to sufficiently suppress an excessive temperature rise in a non-sheet passing area such as an outer peripheral surface of the pressure roller 17 over a continuous fixing process on a plurality of recording media.

In the present embodiment, the set value of the fixing temperature decreases with an increase in the number of recording media having undergone the fixing process, so that the set value is stable regardless of the number of recording media subjected to the continuous fixing process. The advantage is that it is possible to execute the fixed fixing process.

Further, in the present embodiment, the recording medium carrying the unfixed image is heated by the ceramic heater 15 via the film 16 while being passed through the nip portion N. Therefore, there is an advantage that the fixing process can be performed in a short time after the energization of the heating resistor 15B from the commercial power supply 21 is started.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIGS.

The schematic configuration of the image forming apparatus and the fixing device in the present embodiment is the same as that of the laser beam printer 1 and the fixing device 7 and the like.
The description is omitted instead of the above.

In the present embodiment, in the same manner as in the first embodiment, the difference between the fixing temperature and the sheet-to-paper temperature in the process of continuously fixing a plurality of N recording media is set, and M The inter-paper distance, which is the distance between the first recording medium and the (M + 1) th recording medium, is set according to the type of recording medium.

That is, in the present embodiment, when a recording medium of B5 or more and 60 g / m ² or less is subjected to the continuous fixing process, the difference between the fixing temperature and the sheet-to-sheet temperature over the continuous fixing process is determined. The CPU 23 controls the energization from the commercial power supply 21 to the heating resistor 15B so that the temperature becomes 10 ° C., and also sets the inter-paper time corresponding to the inter-paper distance between the Mth recording medium and the (M + 1) th recording medium. (Time T3 in FIG. 8
From T4 to T4) is set to about 2 sec.

On the other hand, when a recording medium of B5 or less and 60 g / m ² or more is subjected to the continuous fixing process, the difference between the fixing temperature and the sheet temperature over the continuous fixing process is 40 ° C.
The CPU 23 from the commercial power supply 21
5B and the M-th recording medium and the M
The sheet interval time corresponding to the sheet interval which is the interval from the (+1) th recording medium is set to about 0.5 sec.

FIG. 8 is a graph showing changes in the temperature detected by the thermistor 18 in the continuous fixing process in this embodiment.

Therefore, when a recording medium of B5 or more and 60 g / m ² or less is subjected to the continuous fixing process, FIG.
As shown in (2), the fixing process of the (M + 1) th recording medium is started about 2 seconds after the fixing process of the Mth recording medium is completed.

Then, when the present inventor measured the temperature change in the non-sheet passing area on the outer peripheral surface of the pressure roller 17 in order to confirm the effects and the like in the present embodiment, the result shown in FIG. 9 was obtained.

FIG. 9 is a graph showing the temperature transition of the non-sheet passing area on the outer peripheral surface of the pressure roller 17 over the period of the continuous fixing process in this embodiment.

That is, as shown in FIG. 9, in the present embodiment, the temperature of the non-sheet passing area on the outer peripheral surface of the pressure roller 17 indicates a value within the range of 140 ° C. to 220 ° C. Thus, a result was obtained in which the temperature increase in the non-sheet passing area over the continuous fixing process was suppressed more than in the first embodiment.

Therefore, in the present embodiment, the effects obtained by the first embodiment can be achieved in a more suitable state.

(Third Embodiment) Next, a third embodiment of the present invention will be described with reference to FIG.

Since the schematic configuration of the image forming apparatus and the fixing device in this embodiment is the same as that of the laser beam printer 1 and the fixing device 7, FIGS.
The description is omitted instead of the above.

In the present embodiment, the sheet interval temperature during the sheet interval from the end of the fixing process of the Mth recording medium to the start of the fixing process of the (M + 1) th recording medium is the Mth recording medium. After the two are set according to the rate of increase in the detected temperature of the temperature detector within the specified time until the rush enters the nip portion, from the low value to the high value of the set values according to the temperature increase rate The inter-sheet temperature is switched stepwise over the inter-sheet period.

That is, in the present embodiment, as shown in FIG. 10, the commercial power supply is determined based on the temperature rise rate of the detected temperature of the thermistor 18 within a specified time until the Mth recording medium enters the nip portion. When it is determined from 21 that the power supplied to the heating resistor 15B is equal to or less than the rated power, the inter-paper period from the end of the fixing process of the Mth recording medium to the start of the fixing process of the (M + 1) th recording medium. The inter-sheet temperature is switched stepwise from a low value (first inter-sheet temperature) to a high value (second inter-sheet temperature) among the set values according to the temperature increase rate, so that the recording medium The fixing property of the tip is guaranteed.

FIG. 10 is a graph showing changes in the temperature detected by the thermistor 18 in the continuous fixing process in this embodiment.

Therefore, when the present inventor measured the temperature transition of the paper passing area on the outer peripheral surface of the pressure roller 17 to confirm the effects and the like in the present embodiment, the supply from the commercial power supply 21 to the heating resistor 15B was performed. Regardless of whether the power is equal to or lower than the rated power, the result that the fixing property of the leading end of the recording medium is guaranteed was obtained.

Therefore, in the present embodiment, the same effects as those of the first embodiment or the second embodiment can be obtained, and the (M + 1) th recording medium after the fixing processing of the Mth recording medium is completed. The inter-sheet temperature in the inter-sheet period until the fixing process starts is changed to two values in accordance with the temperature rise rate of the detected temperature of the thermistor 18 within a specified time until the Mth recording medium enters the nip portion N. After the setting, the set value corresponding to the temperature increase rate is set in a stepwise manner from a low value (first inter-sheet temperature) to a high value (second inter-sheet temperature) over the inter-sheet period. Since the sheet-to-sheet temperature is switched, a stable fixing process can be performed even when the power supply from the commercial power supply 21 to the heating resistor 15B is equal to or less than the rating.

[0105]

As described above, according to the first aspect of the present invention, the difference between the fixing temperature and the sheet-to-sheet temperature depends on the size, type, and thickness of the recording medium and the main body of the fixing device. Since the temperature is set in accordance with at least one of the internal and external temperatures, there is no cost increase and the excessive pressure in the non-sheet passing area such as the pressure member over the continuous fixing process to a plurality of recording media is always performed. It is possible to provide a fixing device in which a rise in temperature is sufficiently suppressed.

According to the second invention of the present application, M
The sheet distance, which is the distance between the first recording medium and the (M + 1) th recording medium, is set according to at least one of the size, type, and thickness of the recording medium and the temperature inside or outside the fixing device main body. Therefore, it is possible to provide a fixing device in which an excessive temperature increase in a non-sheet passing area such as a pressure body over a continuous fixing process on a plurality of recording media is always suppressed without increasing the cost. be able to.

Furthermore, according to the third invention of the present application,
From the end of the fixing process of the M-th recording medium to the start of the fixing process of the (M + 1) -th recording medium, the sheet-to-sheet temperature in the sheet-to-sheet period is within a specified time until the M-th recording medium enters the nip portion. After being set to a plurality of values in accordance with the temperature rise rate of the temperature detected by the temperature detector, the set value corresponding to the temperature rise rate is gradually changed from a low value to a high value over the sheet interval. Since the sheet-to-sheet temperature is switched, it is possible to provide a fixing device capable of performing a stable fixing process even when the power supply from the commercial power supply to the heating unit is equal to or less than the rating.

According to the fourth aspect of the present invention, the fixing temperature is set according to at least one of the size, type, and thickness of the recording medium and the temperature inside or outside the main body of the fixing device. Therefore, it is possible to provide a fixing device capable of executing a stable fixing process irrespective of at least one of the size, type, and thickness of the recording medium and the temperature inside or outside the main body of the fixing device. .

Further, according to the fifth invention of the present application,
Since the set value of the fixing temperature decreases as the number of recording media subjected to the fixing process increases, a fixing device capable of performing a stable fixing process regardless of the number of recording media subjected to the continuous fixing process is provided. can do.

According to the sixth aspect of the present invention, a recording medium carrying an unfixed image is passed through a nip formed between a film and a pressure member pressed against each other. While being heated by the ceramic heater through the film, the nip portion can be quickly heated to the target temperature and maintained, so that the electric power from the commercial power supply to the heating means is started in a short time. A fixing device capable of performing a fixing process can be provided.

Furthermore, according to the seventh invention of the present application,
The energization control means is set to a commercial value so that the difference between the fixing temperature and the sheet-to-sheet temperature becomes a value set according to at least one of the size, type, and thickness of the recording medium and the temperature inside or outside the fixing device main body. Since the power supply from the power supply to the heating means is controlled, it is possible to sufficiently suppress the excessive temperature rise in the non-sheet passing area such as the pressurized body during the continuous fixing processing step on a plurality of recording media without increasing the cost. An image forming apparatus including the intended fixing device can be provided.

Further, according to the eighth invention of the present application, M
The sheet distance, which is the distance between the first recording medium and the (M + 1) th recording medium, is set according to at least one of the size, type, and thickness of the recording medium and the temperature inside or outside the fixing device main body. Therefore, an image provided with a fixing device in which excessive temperature increase in a non-sheet passing area such as a pressure body over a continuous fixing process on a plurality of recording media is always suppressed without increasing cost. A forming device can be provided.

Further, according to the ninth invention of the present application,
From the end of the fixing process of the M-th recording medium to the start of the fixing process of the (M + 1) -th recording medium, the sheet-to-sheet temperature in the sheet-to-sheet period is within a specified time until the M-th recording medium enters the nip portion. After being set to a plurality of values in accordance with the temperature rise rate of the temperature detected by the temperature detector, the set value corresponding to the temperature rise rate is gradually changed from a low value to a high value over the sheet interval. Since the sheet-to-sheet temperature is switched, it is possible to provide an image forming apparatus including a fixing device capable of performing a stable fixing process even when the power supply from the commercial power supply to the heating unit is equal to or less than the rating.

According to the tenth aspect of the present invention, the fixing temperature is set in accordance with at least one of the size, type, and thickness of the recording medium and the temperature inside or outside the main body of the fixing device. Therefore, an image forming apparatus including a fixing device capable of performing a stable fixing process irrespective of at least one of the size, type, thickness of the recording medium and the internal or external temperature of the main body of the fixing device. Can be provided.

Further, according to the eleventh aspect of the present invention, since the set value of the fixing temperature decreases with an increase in the number of fixed recording mediums, the recording medium subjected to the continuous fixing processing can be used. It is possible to provide an image forming apparatus including a fixing device capable of performing a stable fixing process regardless of the number of sheets.

Further, according to the twelfth invention of the present application,
Since the recording medium carrying the unfixed image is heated by the ceramic heater through the film while being passed through the nip formed between the film and the pressing body pressed against each other, the nip is heated to the target temperature. The image is provided with a fixing device capable of quickly raising and maintaining the temperature, thereby shortening the time from when the power is supplied from the commercial power supply to the heating unit to when the fixing process is started. A forming device can be provided.

[Brief description of the drawings]

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

FIG. 2 is a schematic sectional view showing a schematic configuration of the fixing device shown in FIG.

FIG. 3 is a schematic perspective view showing a schematic configuration of the ceramic heater shown in FIG.

FIG. 4 is a block diagram showing a connection relationship between the ceramic heater shown in FIG. 3 and its peripheral means.

FIG. 5 is a graph showing an example of a change in a detected temperature of a thermistor in a continuous fixing process in the first embodiment according to the present application.

FIG. 6 is a graph showing an example of a temperature change in a non-sheet passing area on an outer peripheral surface of a pressure roller in a continuous fixing process according to the first embodiment of the present application.

FIG. 7 is a graph showing an example of a temperature change in a non-sheet passing area on an outer peripheral surface of a pressure roller in a continuous fixing process in a comparative example with respect to the first embodiment according to the present application.

FIG. 8 is a graph showing an example of a change in the temperature detected by a thermistor in a continuous fixing process in the second embodiment according to the present application.

FIG. 9 is a graph showing an example of a temperature change in a non-sheet passing area on an outer peripheral surface of a pressure roller in a continuous fixing process in a second embodiment according to the present application.

FIG. 10 is a graph showing an example of a change in a detected temperature of a thermistor in a continuous fixing process in a third embodiment according to the present application.

FIG. 11 is a graph showing an example of a change in the temperature detected by a thermistor in a conventional continuous fixing process.

[Explanation of symbols]

 Reference Signs List 1 laser beam printer (image forming apparatus) 7 fixing device 15 ceramic heater (heating means) 16 film (fixing member) 17 pressure roller (pressing member) 18 thermistor temperature sensing sensor (temperature detecting member) 19 holder 22 analog digital Conversion circuit 23 CPU (energization control means) 15A Substrate 15B Heating resistor 15C Protective layer 20 Triac 21 Commercial power supply N Nip section P Recording medium

Claims (12)

[Claims] 1. A sheet-like recording medium carrying an unfixed image is heated by a heating unit while passing through a nip formed between a fixing body and a pressing body pressed against each other. A fixing device, comprising a temperature detector for detecting a temperature of a heating unit, and recording the (M + 1) th sheet from the end of the fixing processing of the Mth recording medium in a continuous fixing process on a plurality of N recording media. A fixing device in which the sheet interval temperature, which is the target temperature of the heating unit until the start of the fixing process of the medium, is lower than the fixing temperature, which is the target temperature of the heating unit in the fixing process of the Mth recording medium, A fixing device wherein the difference between the fixing temperature and the sheet-to-sheet temperature is set according to at least one of the size, type, and thickness of the recording medium and the temperature inside or outside the main body of the fixing device. 2. The paper distance, which is the distance between the Mth recording medium and the (M + 1) th recording medium, is determined by the size, type,
2. The image forming apparatus according to claim 1, wherein the temperature is set according to at least one of a thickness and a temperature inside or outside the main body of the fixing device.
3. The fixing device according to claim 1. 3. After the fixing process of the M-th recording medium is completed, M
The sheet-to-sheet temperature in the sheet-to-sheet period up to the start of the fixing process of the +1 sheet recording medium is determined by the rate of increase in the detected temperature of the temperature detector within a specified time until the Mth sheet of recording medium enters the nip portion. The inter-sheet temperature is set in a stepwise manner over the inter-sheet period from a low value to a high value among the set values according to the temperature increase rate. The fixing device according to claim 1, wherein: 4. The fixing temperature is determined by the size, type,
2. The image forming apparatus according to claim 1, wherein the temperature is set according to at least one of a thickness and a temperature inside or outside the main body of the fixing device.
The fixing device according to claim 3. 5. The fixing temperature setting value decreases with an increase in the number of recording media on which fixing processing has been performed.
The fixing device according to claim 4. 6. A heating means includes: a heating resistor provided on one surface of a thin plate made of ceramics as a main component to generate heat when supplied with electric power from a commercial power supply; The detection body is a ceramic heater that is disposed in contact with or in proximity to the fixing body, and the fixing body is an endless belt-shaped film that is pressed against the one surface by a pressing body via a recording medium that carries an unfixed image. The fixing device according to claim 1, wherein the fixing device is provided. 7. An image forming apparatus comprising: the fixing device according to claim 1; and an energization control unit that controls energization from a commercial power supply to the heating unit, wherein a difference between a fixing temperature and a sheet-to-sheet temperature is recorded. The power supply control means controls the power supply from the commercial power supply to the heating means so as to have a value set according to at least one of the size, type, thickness of the medium and the temperature inside or outside the fixing device body. An image forming apparatus, comprising: 8. The distance between the M-th recording medium and the (M + 1) -th recording medium, which is the distance between sheets, is determined by the size, type,
8. The setting according to at least one of the thickness and the temperature inside or outside the main body of the fixing device.
An image forming apparatus according to claim 1. 9. The image forming apparatus according to claim 1, wherein after the fixing process of the Mth recording medium is completed,
The inter-sheet temperature until the fixing process of the +1 sheet recording medium starts is
A plurality of values are set according to the temperature rise rate of the temperature detected by the temperature detector within a specified time until the Mth recording medium enters the nip portion. 9. The paper interval temperature is switched stepwise from a low value to a high value.
An image forming apparatus according to claim 1. 10. The fixing temperature is set according to at least one of the size, type, and thickness of the recording medium and the temperature inside or outside the main body of the fixing device. The image forming apparatus according to claim 1. 11. The image forming apparatus according to claim 7, wherein the set value of the fixing temperature decreases as the number of recording media on which the fixing process has been performed increases. 12. A heating means includes a heating resistor provided on one surface of a thin plate mainly composed of ceramics, which generates heat by being supplied with electricity from a commercial power supply, and a heating resistor on the other surface of the substrate. The detection body is a ceramic heater that is disposed in contact with or in proximity to the fixing body, and the fixing body is an endless belt-shaped film that is pressed against the one surface by a pressing body via a recording medium that carries an unfixed image. The image forming apparatus according to any one of claims 7 to 11, wherein: