JP2002108133A - Fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a good heating mode for controlling start-up of a heater to a fixing temperature in accordance with a paper type and an environment of a recording material, thereby achieving a good heating regardless of the paper type and the environment. Fixing is to obtain a high quality image. SOLUTION: The fixing device is of a film heating type, a cylindrical fixing film is arranged outside a heater, and a pressure roller is pressed against the film to form a fixing nip portion. There are heating modes 1 and 2 in which the temperature control method is different for the rise from the start of energization to the fixing temperature of the heater from the time when the recording material enters the fixing nip. Mode 1 is a mode for fixing to a recording material such as thin paper or plain paper.
Start up. The mode 2 is a mode for fixing a recording material such as a thick paper requiring a high fixing temperature.
And then the fixing temperature T2.

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 heating and fixing a toner image on a recording material in an electrophotographic image forming apparatus, and an image forming apparatus equipped with the fixing device. Regarding control.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine, a printer, a facsimile machine or the like utilizing an electrophotographic system, a heat roller system, a film heating system and the like are used as a fixing device for heating and fixing a toner image on a recording material. And the like are widely used.

In these fixing devices, an electric current is applied to a heater such as a halogen lamp or a resistance heating element to generate heat, and the heat raised to the fixing temperature is applied to a toner image on a recording material via a roller or a film. This heat-fixes the toner image to the recording material. Further, even when the image forming apparatus is used under various types of recording materials and environments, the fixing apparatus performs good fixing, and the image forming apparatus needs to have a predetermined image quality performance. In contrast, a plurality of heating modes are provided so that the adjustment of the fixing temperature can be selected according to the type of paper and the environment.

[0004]

However, conventionally, even when the heating mode is selected, the control for starting up to the fixing temperature in the heating mode has not been finely controlled according to the type of recording material and the environment. Therefore, depending on the type of paper and the environment, good fixing cannot be performed, and a high-quality image cannot be obtained in some cases.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a heating mode for controlling the start-up of a heater to a fixing temperature in a fine manner in accordance with the type of recording material and the environment, thereby irrespective of the type of paper and the environment. An object of the present invention is to provide a fixing device capable of obtaining a high-quality image by performing good fixing, and an image forming apparatus equipped with the fixing device.

[0006]

The above object is achieved by a fixing device and an image forming apparatus according to the present invention. In summary, the present invention provides a fixing member having a heating element, a temperature detecting means for detecting a temperature of the heating element, and adjusting a power supply to the heating element based on a detection result of the temperature detecting means. Control means for controlling the heating element to the fixing temperature, and a pressure member that forms a fixing nip portion by pressing against the heating member,
In a fixing device in which a recording material on which a toner image is formed enters the fixing nip portion, the calorie of the heating element is applied to the recording material, and the toner image is fixed on the recording material by heating. A fixing device comprising a plurality of heating modes in which a method of raising the heating body to a fixing temperature from the start of energization of the body to the time when the recording material enters the fixing nip portion is different. According to another aspect of the present invention, there is provided an image forming apparatus including the above fixing device.

According to the present invention, the selection of the heating mode depends on the type of the recording material, the temperature of the environment where the image forming apparatus having the fixing device is placed, the humidity of the environment, and the temperature of the fixing device. Perform based on at least one. The fixing member includes a heating element and a cylindrical film disposed outside the heating element, and the pressing member includes an elastic roller pressed against the film at the heating element. Or
The fixing member includes a roller having a built-in heating element, and the pressing member includes an elastic roller pressed against the roller.

According to the present invention, there is provided a heating mode including at least two heating modes for two types of recording materials having different fixing temperatures, and the mode 1 for a recording material having a lower fixing temperature among the two modes is From the start of energization to the fixing temperature T1 in one stage, the mode 2 for the recording material having the higher fixing temperature is started in a plurality of stages from the start of energization to the fixing temperature T2.

A heating mode including at least two heating modes for two types of recording materials having different fixing temperatures in consideration of the temperature of the environment, and a mode 1 for a recording material having a lower fixing temperature among the two modes. When the temperature of the environment is low or room temperature, the start-up from the start of energization to the fixing temperature T1 is performed in one stage, and when the temperature of the environment is high, the fixing temperature is set to the fixing temperature T1.
The fixing temperature T1 ', which is lower than 1, is set in one step from the start of energization to the fixing temperature T1', and the mode 2 for the recording material having a higher fixing temperature is such that the environment temperature is low or room temperature. At some point, the fixing temperature T
2 is performed in one stage, and when the temperature of the environment is high, the fixing temperature is set to a fixing temperature T2 'lower than the fixing temperature T2, and the fixing temperature T2'
Up to multiple stages.

A heating mode including at least two heating modes for two types of recording materials having different fixing temperatures;
In the mode 1 for the recording material having the lower fixing temperature of the two modes, the rise from the start of energization to the fixing temperature T1 is performed in one step, and the one-step rise is performed from the fixing temperature T1 to the temperature. The heating up to a temperature (T1-D) lower by D was performed with a power input amount of 100% duty to the heating element, and the duty was gradually reduced from the temperature (T1-D) to the fixing temperature T1. The mode 2 for the recording material with the higher fixing temperature is performed with the power input amount.
The heating up from the start of energization to the fixing temperature T2 is started at a power input amount of less than 100% to the heating element by 1%.
Perform in steps.

A heating mode including at least two heating modes for two types of recording materials having different fixing temperatures;
Of the two modes, mode 1 for a recording material having a lower fixing temperature is performed in a plurality of steps from the start of energization to the fixing temperature T1, and mode 2 for a recording material having a higher fixing temperature is Starting from energization to the fixing temperature T2 is performed in one stage.

A heating mode including at least two heating modes for two types of recording materials having different fixing temperatures;
Mode 1 for the recording material having the lower fixing temperature of the two modes is performed in one stage from the start of energization to the fixing temperature T1. Mode 2 for the recording material having the higher fixing temperature is From the start of energization, the temperature rises in one step up to a temperature T21 higher than the fixing temperature T2, the temperature is kept at the temperature T21, and then the temperature falls in one step to the fixing temperature T2.

A heating mode including at least three heating modes in consideration of the temperature of the environment for two types of recording materials having different fixing temperatures, and a mode 1 for a recording material having a lower fixing temperature among the three modes Is a single-stage operation from the start of energization to the fixing temperature T1 irrespective of the temperature of the environment, and Mode 2 for a recording material having a higher fixing temperature is performed when the temperature of the environment is high or room temperature. , Starting from energization to fixing temperature T2 is 1
Mode 3 for recording material with higher fixing temperature
When the temperature of the environment is low, the temperature is raised in one step from the start of energization to a temperature T31 lower than the fixing temperature T2, and the temperature is maintained at the temperature T31 for a time equal to or longer than the startup end time in the mode 2. Thereafter, the temperature is raised in one step to the fixing temperature T2.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a fixing device and an image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

Embodiment 1 In the following embodiment, a case of a laser beam printer will be described as an example of an image forming apparatus.

FIG. 1 is a schematic sectional view showing an embodiment of the image forming apparatus of the present invention, and FIG. 2 is a schematic sectional view showing a fixing device mounted on the image forming apparatus of FIG. The present image forming apparatus is configured as a laser beam printer, and the present invention is characterized in controlling the temperature of a fixing device mounted thereon.

As shown in FIG. 1, the laser beam printer according to the present embodiment includes a process cartridge 18 having a photosensitive drum 20 at a substantially central portion of a printer body surrounded by an exterior 14. Below, a paper feed cassette 15 containing a recording material P such as paper or OHT as a recording medium is provided. The recording material P in the cassette 15 is fed by a feed roller 16 and is conveyed by a conveying roller 17 toward a transfer portion of the photosensitive drum 20. On the right side of the cartridge 18, an environment sensor 23 for detecting the temperature and humidity of the environment where the printer is placed is provided.

The process cartridge 18 forms an image on the photosensitive drum 20 by a known image forming process, and exposes and scans the photosensitive drum 20 with a laser beam generated from a laser unit 19 outside the cartridge 18. An electrostatic latent image is formed on the surface of the drum 20, and the latent image is developed by a developing unit in the cartridge 18 and is visualized as a toner image.

The toner image obtained on the photosensitive drum 20 is
On the recording medium P conveyed from the cassette 15 to the transfer section,
The image is transferred by the transfer roller 21 outside the cartridge 18. The recording material onto which the toner image has been transferred is conveyed to the fixing device 10, where the toner image is fixed on the recording material, and then discharged onto the upper surface of the printer body exterior 14 by the discharge roller 22.

According to this embodiment, the fixing device 10 is of a film heating type. As shown in FIG. 2, a heater 6 is fixed to a heat-resistant stay 2 and a heat-resistant cylinder is provided outside the heater 6. A fixing member is formed by arranging a film-shaped thin film (fixing film) 1, and an elastic pressure roller 7 is pressed against a heater 6 through the film 1 of the fixing member to press the film 1 and the pressure roller 7. And a fixing nip portion T having a predetermined width is formed therebetween.

The heater 6 has a resistance heating element 5 formed in one or a plurality of rows on the surface of a substrate 4 made of ceramic or the like by screen printing or the like. The temperature is detected by the thermistor 3 of the temperature detecting means provided on the back surface of the heater 6, and the amount of electricity supplied to the heater 6 (resistance heating element 5) is controlled based on the detected temperature, thereby controlling the amount of heat generated by the heater 6. Thus, the temperature of the heater 6 is adjusted to a predetermined fixing temperature. As shown in FIG. 3, the thermistor 3 is connected to a voltage detection circuit composed of a DC power supply E and a resistor R, and measures the voltage division of the constant voltage V0 of the power supply E by the thermistor resistance, thereby obtaining the thermistor 3.
Is obtained, and the heater temperature is measured.

The fixing film 1 is driven to rotate by the pressure roller 7, and the rotational force applied to the pressure roller 7 in the direction of the arrow is transmitted to the recording material P at the fixing nip T, and further transmitted to the fixing film 1. . The recording material P is introduced into the fixing nip portion T from the right side of FIG. 2, and when the recording material P enters the fixing nip portion, the recording material P comes into close contact with the surface of the fixing film 1,
The fixing nip portion is nipped and conveyed in one place with the film 1,
While passing through the fixing nip portion, the recording material P and the toner image 9 thereon are heated via the fixing film 1 by the heater 6 whose temperature has been raised to the fixing temperature, and the toner image 9 is fixed on the recording material P.

FIG. 4 is a flowchart showing the outline of the temperature control in the control means of the fixing device 10. The control means (control circuit) includes a CPU, an A / D converter, a triac, and the like.

As shown in FIG. 4, first, the heater temperature is detected by the thermistor 3 on the heater 6 (Step S).
1) The analog detection output is A / D converted into a digital value by an A / D converter (step S2), and the obtained digital detection output is taken into the CPU (step S3), and opened / closed based on the detected temperature information. A signal is output to a triac (energization control unit), and the AC voltage applied to the resistance heating element 5 is controlled by the triac so that the detected temperature matches the target heater temperature (target fixing temperature). (Step S4), and supplies electric power to the heating resistor 5 with the controlled voltage, whereby the heater 6
Is heated to maintain a predetermined heater temperature (step S5).

According to the present invention, as the heating mode of the fixing device 10, the heating of the heater 6 from the start of power supply to the heater 6 (start of starting) until the recording material enters the fixing nip portion, that is, the fixing temperature. There are a plurality of modes in which the temperature control methods for starting are different, and a heating mode is selected according to a predetermined selection condition during image formation. The selection of the heating mode is specified by the user from an operation panel attached to the printer main body, from a personal computer, automatically specified by the printer main body, or a combination thereof.

In this embodiment, two heating modes 1 and 2 are provided. Mode 1 is a heating mode (plain paper mode) for fixing a toner image on a recording material such as thin paper, plain paper, or smooth paper (including OHT). Mode 2 is a heating mode for thick paper or rough paper. This is the heating mode (thick paper mode) when the toner image is fixed on such a recording material.

FIG. 5 shows a heating mode of the fixing device of this embodiment. FIG. 5 is a graph showing a change in the output (analog value) of the thermistor 3 when the start-up temperature control in the heating mode of the present embodiment is performed. Since the resistance value of the thermistor 3 decreases as the temperature increases, the partial pressure of the thermistor 3 also decreases. Therefore, the output voltage of the thermistor in FIG. 5 decreases as the vertical axis increases, and the detected temperature of the heater increases. The unit of the vertical axis may be voltage or resistance, and may be considered as a value converted into temperature.

The heating mode 2 is a thick paper mode when the recording material is a thick paper or a paper having a rough surface, and therefore requires a high fixing temperature. The fixing temperature T2 is such that the recording material is thin paper, plain paper, or smooth paper. Heating mode (plain paper mode) 1
Is set to be higher than the fixing temperature T1.

As shown in FIG. 5, in mode 1, the fixing temperature is raised to the fixing temperature T1 by one-step startup, and when the power supply to the heater is started, the fixing temperature is increased to the fixing temperature T1 at a stretch. On the other hand, in the mode 2, the temperature rises up to the fixing temperature T2 by the two-stage rise, and once the temperature reaches the rise temperature T21 once the power supply to the heater is started, the fixing temperature T rises.
Increase to 2.

In this embodiment, as described above, the start-up control method up to the fixing temperature is changed depending on the type of the recording material. Since we started up in steps,
It is possible to start up while preventing a rapid temperature change, prevent damage to the fixing device and nearby components due to a rapid temperature change, and extend the service life of the components.

In the above, in the heating mode 2 for thick paper or the like, the heating mode is set to two stages in contrast to the heating mode 1 for plain paper, but as shown in FIG.
By setting a rising temperature T11 slightly lower than the above, the fixing temperature T1 can be raised in two steps from the start of energization to the heater. If the fixing temperature is raised in two steps as described above, there is a merit that a temperature control program can be easily assembled, but the merit can be obtained not only in mode 2 but also in mode 1.

Embodiment 2 FIG. 7 is an explanatory view showing a heating mode of a fixing device according to another embodiment of the present invention.

In the present embodiment, the heating mode is set in consideration of the temperature of the environment where the printer is placed, which is detected by the environment sensor 23 in FIG. FIG. 7 shows a change in the output (analog value) of the thermistor when the start-up temperature control in the heating mode is performed as in FIG.

In FIG. 7, a heating mode 1 is a heating mode (plain paper mode) for fixing a recording material such as thin paper, plain paper, or smooth paper. When the ambient temperature is high, the temperature around the heater and the temperature of the recording material are considered to be high.
The fixing temperature is raised to a fixing temperature T1 ′ lower than 1. In each case, the heating up to the fixing temperature is performed in one stage.

The heating mode 2 is a heating mode (fixed paper mode) for fixing on a recording material such as thick paper or paper having a rough surface.
It is. When the ambient temperature is high, the temperature around the heater and the temperature of the recording material also increase, so in the thick paper mode, the surface of the pressure roller 7 is excessively heated before the recording material enters the fixing nip, resulting in excessive fixing. Cheap. If the toner image on the recording material is excessively fixed, the toner is soft and viscous even after the toner image on the recording material has passed through the fixing nip portion. The toner that has made one round of adhesion to the film adheres to a portion of the recording material where there is no original toner image, causing image distortion (hot offset).

Therefore, in the mode 2, the fixing temperature and the starting method are made different depending on the environmental temperature. That is, when the temperature is low and at room temperature, the fixing temperature T2 is raised in one step.
In the present example, the starting temperatures T22 ', T2
After 1 '(T22'<T21'), it was started up in three steps.

According to the present embodiment, as described above, when the printer is used in a high-temperature environment, fixing to thick paper or the like can be performed without generating hot offset.

In the above, the heating mode is set in consideration of the temperature of the environment where the printer detected by the environment sensor 23 is placed. However, the heating mode is set in consideration of the humidity of the environment where the printer detected by the environment sensor 23 is placed. When a high-humidity environment is detected, the method of starting mode 2 may be different from that of mode 1 according to the present embodiment in order to prevent the recording material from slipping due to sudden startup.

Embodiment 3 In the present embodiment, whether the heater 6 is started up with the maximum power of 100% duty or the start-up with reduced duty is made different depending on the heating mode. The power supplied to the heater 6 was controlled by wave number control. Synchronization was set to 10 half-waves and one cycle.

FIG. 8 shows a heating mode of the fixing device in this embodiment. As in the case of FIG. 5, a change in the output (analog value) of the thermistor when the start-up temperature control in the heating mode is performed is shown.

In FIG. 8, a mode 1 is a heating mode (plain paper mode) for fixing on a recording material such as thin paper, plain paper, or smooth paper. When the temperature detected by the thermistor 3 is turned on, the heater 6 is energized. From the fixing temperature T1 to the temperature D
At (T1-D) just below (° C), the duty is 100
% Of the maximum power (power supply voltage) is inputted, and when the temperature becomes higher than (T1-D), the duty is reduced.

On the other hand, mode 2 is a heating mode (fixed paper mode) for fixing on a recording material such as thick paper or rough paper, and is started up with a small duty of less than 100% at the same time as the start of energization (PID control). . Rather than starting with the maximum power as in mode 1, 100 as in mode 2
Since the startup is started slowly with a small duty of less than%, hot offset can be prevented as in the second embodiment.

As in the case of mode 1, the graph drawn by the thin line in mode 2 shows (T2) which is lower than fixing temperature T2 by temperature D.
Until -D), when the temperature rises at the maximum power with a duty of 100%, and when the temperature becomes higher than (T2-D), the duty is reduced and the temperature is raised to the fixing temperature T2. In this case, , The temperature has risen too much and overshoots T2.

Particularly, in an image forming apparatus in which the fixing temperature of the fixing device is determined so that the fixing property can be sufficiently secured with a thick paper or a paper having a rough surface even in a low temperature environment, a heating mode having a high fixing temperature is used, In addition, when the maximum power is high, overshoot is likely to occur and hot offset is likely to occur. Therefore, in order to prevent overshoot, it is necessary to devise a method of starting up in a plurality of stages. However, as in mode 2 of this embodiment, starting up with a small duty of less than 100% can also be used.
Overshoot can be prevented.

Example 4 In this example, two-stage startup was performed in the heating mode 1 having a lower fixing temperature.

In FIG. 9, a heating mode 1 is a mode for fixing to a recording material such as thin paper, plain paper, or smooth paper (plain paper mode). In mode 1, the heating mode is started once to prevent overshoot. The temperature is raised to a temperature T11, and after the temperature is settled, the temperature is raised to a fixing temperature T1.

On the other hand, the heating mode 2 is a mode for fixing on a recording material such as a thick paper or a paper having a rough surface (thick paper mode). In this case, the heating is started up to the fixing temperature T2 at a stretch after the energization of the heater is started.

When the entire fixing device is cooled in a low-temperature environment, the quality of the fixing property is determined by how long the temperature of the pressure roller 7 can be increased before the recording material enters the fixing nip. Therefore, it is not advisable to start up the fixing temperature T2 in two steps to fix a considerably thick cardboard in a low-temperature environment.
It is good to start up.

In the present embodiment, as described above, good fixability can be obtained even when a considerably thick recording material is fixed in a low-temperature environment.

Embodiment 5 In this embodiment, a case will be described in which a heating mode for securing the fixing property of the recording material in a short time is provided.

In FIG. 10, a heating mode 1 is a mode for fixing to a recording material such as thin paper, plain paper, or smooth paper (plain paper mode), and a heating mode 2 is a mode for fixing thick paper or paper having a rough surface. In the mode (fixed paper mode) when fixing to a recording material, in mode 1, the fixing temperature T1 rises at a stretch, but in mode 2, it rises at a stretch to the rising temperature T21 higher than the fixing temperature T2, and the temperature rises for a while. The fixing temperature is returned to the fixing temperature T2 as the recording material enters the fixing nip.

By performing such control in the mode 2, the temperature of the pressure roller 7 can be increased even if the time from when the heater 6 is energized to when the recording material enters the fixing nip is the same. Therefore, even for a thick paper or a paper having a rough surface which needs to be fixed in the mode 2, the fixing property can be improved from the first sheet.

That is, when the heater is energized (cold start) from a state where the entire fixing device is cooled, the fixing property of the first sheet of the recording material is set to the same level as in the mode 1 for thin paper or OHT (smooth paper). This is effective when it is necessary to secure by the raising time.

This is because it is not sufficient to raise the fixing temperature only in order to secure the fixing property, and sufficient heat is applied to the pressure roller so that the recording material enters the fixing nip when the recording material enters the fixing nip. This is because it is necessary to heat the toner even from the non-printing surface (back surface) side. Otherwise, the temperature of the pressure roller rapidly drops during the fixing of the first sheet, and the fixing property may be deteriorated in the latter half of the first sheet.

If the same operation is performed on the thin paper or the OHT in the mode 1, a slip may occur in a high humidity environment.

Embodiment 6 In this embodiment, as a heating mode, there is provided a mode for preventing harmful effects of toner contamination on the pressure roller.

As one of the adverse effects of the fixing device, there is a phenomenon in which a lump of toner adheres to the pressure roller 7 and becomes large, which is transferred to a recording material. One of the causes is considered to be toner attached to the fixing film 1 when the toner image is fixed. When the temperature of the heater and the pressure roller is suddenly increased by rapidly heating the heater by controlling the rising temperature, the toner on the fixing film is transferred to the pressure roller, and this is repeated many times. Then, it is considered that a lump of toner is formed on the pressure roller.

Therefore, in addition to the plain paper mode 1 and the thick paper mode 2 in which normal fixing is performed, as a modification of the thick paper mode, the toner on the fixing film is not transferred to the pressure roller to prevent toner contamination of the pressure roller. For this purpose, a mode 3 for slowly starting up the heater is provided.

In FIG. 11, heating mode 2 and mode 3
The only difference is the startup temperature control. Even when the mode 2 is selected, when the environment sensor 23 detects a low temperature below a certain threshold, the mode automatically enters the mode 3. This is because, when the fixing temperature and the start-up time are determined, starting from a low temperature state and starting from a low temperature state are more abrupt when starting from a low temperature state because of the temperature difference. In order to prevent this, the mode is shifted to mode 3 in which the heater is slowly started.

In some of the embodiments described above, the heating mode is provided with a plurality of startup temperatures in order to slowly start the heater. In this embodiment, the startup time is extended. Thus, the heater was slowly started.

In FIG. 11, when the mode 2 is designated and the environment sensor 23 detects a temperature higher than the room temperature, the temperature rises up to the fixing temperature T2 in the same start-up time Ta as the mode 1 which does not change with the temperature of the environment. Then, the recording material enters.

On the other hand, if mode 2 is specified and the environment sensor detects a temperature lower than room temperature,
The temperature rises to a rising temperature T31 lower than the fixing temperature T2 by the start of energization of the heater, and the temperature rises for a time Tb.
After holding for a while until (Tb> Ta), the temperature is raised to the fixing temperature T2 by time Tc, and the recording material enters. In this way, by providing the rising temperature T31 lower than the fixing temperature T2 and maintaining the temperature T31, the rising time until the fixing temperature T2 is extended.

However, the mode automatically transitions from mode 2 to mode 3 when the environmental temperature is detected when the temperature is close to the environmental temperature detected by the fixing device (cold start).
For example, when the current printing is started shortly after the previous printing is completed (intermittent printing), the mode is shifted from the mode 2 to the mode 3 because the fixing device is warmed by the heat generated at the time of the previous printing. The effect of doing so is reduced.

In the present embodiment, as described above, depending on the heating mode, a rising temperature lower than the fixing temperature is set to extend the rising time. Thus, toner contamination of the pressure roller can be prevented.

In the above description, the start-up method has two steps in the mode 3 as compared to the mode 2, but as shown in FIG. 12, the start-up temperature T31 is lower than the fixing temperature T2 in the time Td as shown in FIG. Thereafter, the temperature can be raised in two stages so that the temperature rises to the fixing temperature T2 by the time Ta. If the fixing temperature is raised in two stages as described above, there is an advantage that a temperature control program can be easily set.

In the above description, the fixing device is a film heating system. However, the fixing device of the heating roller type has a fixing nip portion formed by pressing a pressure roller made of an elastic roller against a fixing roller having a built-in heater. The same effects can be obtained by applying the present invention in the same manner.

[0067]

As described above, according to the present invention,
The heating mode, which controls the start-up of the fixing device to the fixing temperature, is fine-grained according to the paper type and environment of the recording material, so that adverse effects such as offset and pressure roller contamination can be prevented. Regardless, good fixing can be performed, and a high-quality image can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing one embodiment of an image forming apparatus of the present invention.

FIG. 2 is a schematic sectional view showing a fixing device mounted on the image forming apparatus of FIG.

3 is a diagram illustrating a temperature detection circuit of a thermistor provided on a heater substrate of the fixing device of FIG. 2;

FIG. 4 is a flowchart illustrating an outline of temperature control performed by a control unit of the fixing device of FIG. 2;

FIG. 5 is an explanatory diagram illustrating a heating mode of the fixing device according to the first exemplary embodiment.

FIG. 6 is an explanatory diagram showing a modification of the heating mode of FIG. 5;

FIG. 7 is an explanatory diagram illustrating a heating mode of the fixing device according to the second exemplary embodiment.

FIG. 8 is an explanatory diagram illustrating a heating mode of a fixing device according to a third embodiment.

FIG. 9 is an explanatory diagram illustrating a heating mode of a fixing device according to a fourth embodiment.

FIG. 10 is an explanatory diagram illustrating a heating mode of a fixing device according to a fifth embodiment.

FIG. 11 is an explanatory diagram illustrating a heating mode of a fixing device according to a sixth embodiment.

FIG. 12 is an explanatory diagram showing a modification of the heating mode in FIG. 11;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixing film 2 Stay 3 Thermistor 4 Substrate 5 Resistance heating element 6 Heater 7 Pressure roller 10 Fixing device P Recording material

Continued on the front page F term (reference) 2H033 AA02 BA08 BA32 BB01 BB28 CA07 CA08 CA11 CA16 CA17 CA28 CA30 CA32 CA37 CA48 3K058 AA34 AA54 AA55 BA18 CA12 CA16 CA23 CA46 CA61 CA86 CB06 CB14 CB22 CB23 CB26 CB32 ACO3 CA06 CB02 DA02 DB04 EE06 FF03 FF06 GG04 HH02 JJ05 KK05 LL24 MM09

Claims (11)

[Claims] A fixing member having a heating element; a temperature detecting means for detecting a temperature of the heating element; and a power supply to the heating element being adjusted based on a detection result of the temperature detecting means. Control means for controlling the fixing temperature, and a pressure member for pressing the heating member to form a fixing nip portion,
A fixing device that applies a heat amount of the heating element to the recording material by causing a recording material having a toner image formed to enter the fixing nip portion and heat-fixes the toner image to the recording material is provided. A fixing device comprising a plurality of heating modes which differ in a method of raising the heating body to a fixing temperature from the start of energization of the body to the time when the recording material enters the fixing nip. 2. The method according to claim 1, wherein the selection of the heating mode is at least one of a type of the recording material, an environment temperature in which the image forming apparatus having the fixing device is placed, an environmental humidity, and a fixing device temperature. A fixing device characterized in that the fixing is performed on the basis of: 3. A heating mode including at least two heating modes for two types of recording materials having different fixing temperatures, and a mode 1 for a recording material having a lower fixing temperature among the two modes is from the start of energization. 4. The method according to claim 1, wherein the start up to the fixing temperature T1 is performed in one stage, and in the mode 2 for the recording material having a higher fixing temperature, the start up to the fixing temperature T2 is started in a plurality of stages. 1 or 2 fixing device. 4. A heating mode including at least two heating modes in consideration of the temperature of the environment for two types of recording materials having different fixing temperatures, wherein a recording material having a lower fixing temperature among the two modes is provided. In mode 1, when the temperature of the environment is low or room temperature, start-up from the start of energization to the fixing temperature T1 is performed in one stage, and when the temperature of the environment is high, the fixing temperature is set to the fixing temperature. Fixing temperature T lower than T1
1 ′, the rise from the start of energization to the fixing temperature T1 ′ is performed in one stage. In the mode 2 for the recording material having the higher fixing temperature, when the temperature of the environment is low or room temperature, When the temperature of the environment is high, the fixing temperature is set to a fixing temperature T2 'lower than the fixing temperature T2, and the temperature is raised from the start of energization to the fixing temperature T2'. 3. The fixing device according to claim 1, wherein the start-up is performed in a plurality of stages. 5. A heating mode including at least two heating modes for two types of recording materials having different fixing temperatures, wherein a mode 1 for a recording material having a lower fixing temperature among the two modes is from the start of energization. The start up to the fixing temperature T1 is performed in one stage, and the start up to the temperature (T1-D) lower than the fixing temperature T1 by the temperature D is performed at a duty of 100% to the heating element. The power supply amount is used, the temperature is raised from the temperature (T1-D) to the fixing temperature T1, and the duty is gradually reduced. The fixing device according to claim 1, wherein the heating up to the fixing temperature T <b> 2 is performed in one stage with a power input amount of less than 100% duty to the heating element. 6. A heating mode including at least two heating modes for two types of recording materials having different fixing temperatures, wherein a mode 1 for a recording material having a lower fixing temperature among the two modes is from the start of energization. 3. The method according to claim 1, wherein the start up to the fixing temperature T1 is performed in a plurality of stages, and in the mode 2 for the recording material having a higher fixing temperature, the start up to the fixing temperature T2 is started in a single stage. 1 or 2 fixing device. 7. A heating mode including at least two heating modes for two types of recording materials having different fixing temperatures, wherein a mode 1 for a recording material having a lower fixing temperature among the two modes is from the start of energization. In the mode 2 for the recording material having a higher fixing temperature, the temperature is raised in one step from the start of energization to a temperature T21 higher than the fixing temperature T2, and the temperature T21 is raised at the temperature T21. 3. The method according to claim 1, wherein the temperature is lowered in one step to the fixing temperature T2 after the holding.
Fixing device. 8. A heating mode including at least three heating modes in consideration of the temperature of the environment for two types of recording materials having different fixing temperatures, wherein a heating mode for a recording material having a lower fixing temperature among the three modes is provided. Mode 1 is a single-stage startup from the start of energization to the fixing temperature T1 irrespective of the temperature of the environment. Mode 2 is for a recording material having a higher fixing temperature, where the temperature of the environment is high or room temperature. In this case, the start-up from the start of energization to the fixing temperature T2 is performed in one stage, and the mode 3 for the recording material having a higher fixing temperature is such that when the temperature of the environment is low, the fixing temperature T2
Up to a lower temperature T31 in one stage, and the temperature T31
The fixing device according to claim 2, wherein the fixing device holds the fixing temperature for a time equal to or longer than the start-up end time in the mode 2 and then starts up the fixing temperature T2 in one step. 9. The image forming apparatus according to claim 1, wherein the fixing member includes a heating member and a cylindrical film disposed outside the heating member, and the pressing member includes an elastic roller pressed against the film at a portion of the heating member. The fixing device according to any one of claims 1 to 8, wherein 10. The fixing device according to claim 1, wherein the fixing member includes a roller having a built-in heating element, and the pressing member includes an elastic roller pressed against the roller. The fixing device as described in the above. 11. An image forming apparatus equipped with the fixing device according to claim 1.