JP2000221815A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve productivity by correcting the influence of the deterioration of the hardness of an elastic member due to thermal degradation by estimating the degree of the thermal degradation of the elastic member based on integrated total time which is the integrated value of energizing time for heating means and correcting a fixing condition in accordance with the degree of the thermal degradation. SOLUTION: Motors 17 and 28, a heating heater 27 and a temperature sensor 33 are connected to a control part 35 constituting a thermal degradation estimating means and a fixing condition correcting means. The temperature of the silicone rubber layer 26 of a pressure roller 15 is detected by the temperature sensor 33 when it is during energizing the heating heater 27. Next, a timer is started when detected temperature is equal to or above specified temperature, and time-measuring is continued until it is detected that it is not during energizing. When it is detected that it is not during the energizing, the timer is stopped, and the energizing time at this time is read, and the integrated value of the energizing time is calculated and stored. When a copying mode is set as an ordinary paper mode, the fixing speed of the ordinary paper mode is corrected, and fixing speed is corrected in accordance with an integrated heating time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer and a facsimile by an electrophotographic system, and a transfer sheet from an image carrier to a plain paper or a transparent resin sheet for OHP (sheet for OHP). The present invention relates to a fixing device for fixing a developer image transferred thereto by heating and melting the same.

[0002]

2. Description of the Related Art Conventionally, as a fixing device of this type, FIG.
As shown in FIG. 2, a heat fixing member 3 comprising a pair of rollers each having an elastic member 2 provided on the outer periphery of a metal cylindrical body 1,
4, a heating means 5 for heating these heat fixing members 3, 4, a driving means 6 for rotating at least one heat fixing member 3, and a spring 7 for pressing the heat fixing members 3, 4 against each other with a constant pressing force. There is a known one. The transfer sheet 9 is transported to the contact portion (nip portion 8) of the elastic member 2 of the pair of heat fixing members 3 and 4. The developer on the transfer sheet 9 is melted by heat supplied from the heat fixing members 3 and 4 and is fixed on the transfer sheet 9.

[0003]

In order to increase the productivity of a copying machine, a printer or the like, the rotational speed of the heat fixing members 3 and 4 is increased to increase the speed at which the transfer sheet 9 passes through the nip portion 8 (fixing speed). ) Needs to be increased.

However, in the conventional fixing device, the elastic member 2
The thermal conductivity of the silicone rubber that constitutes
The transfer sheet 9 passing through the nip portion 8 has a larger surface area than the efficiency of supplying heat from the heating means 5 to the surface of the elastic member 2 because of about 10 ⁻³ al / cm · sec · ° C. Efficiency of removing heat from is higher. Therefore, when the fixing speed is increased, a phenomenon occurs in which the surface temperature of the elastic member 2 temporarily decreases at the start of the continuous paper feeding. This decrease in surface temperature causes poor image gloss and poor fixing.

[0005] In order to increase the efficiency of heat supply from the heating means 5 to the surface of the elastic member 2, the thermal conductivity of the silicon rubber constituting the elastic member 2 is increased by using silica, iron oxide or the like added to the silicon rubber. May be replaced with a high thermal conductive filler such as alumina or magnesium oxide, and the amount of addition may be increased. However, high thermal conductive fillers do not have the effect of increasing heat resistance, and increasing the amount of fillers inevitably reduces the amount of polymer components having high heat resistance. Easy to wake up. As in the fixing device shown in FIG. 22, when the pressing force of the heat fixing members 3 and 4 is constant, the width (nip width) of the nip portion 8 increases when the hardness decreases due to thermal deterioration. When the nip width increases, the amount of heat supplied from the nip portion 8 to the transfer sheet 9 changes, and the image quality changes.

When the amount of the filler added increases, the hardness of the silicone rubber increases, and the elasticity of the elastic member 2 decreases. When the elasticity of the elastic member 2 is reduced, a very high pressure contact or elastic member 2 is used to secure the width of the nip portion 8.
It is necessary to increase the thickness of the sheet, which causes the image to be crushed, causes paper wrinkles, and causes poor fixing due to a decrease in the heat supply amount.

Further, if the crosslink density is increased by changing the polymer component, the decrease in hardness due to the thermal degradation can be reduced. However, the increase in the crosslink density causes the elasticity of the elastic member 2 to decrease.

As described above, it is difficult to increase all of the thermal conductivity, heat resistance and elasticity of the silicone rubber constituting the elastic member, and when the thermal conductivity is set to be high in order to enhance the productivity, A decrease in hardness due to thermal deterioration cannot be avoided.

In view of such a problem in the conventional fixing device, it is an object of the first invention to provide a fixing device having high productivity by correcting the effect of a decrease in hardness of an elastic member due to thermal deterioration. . Another object of the present invention is to prevent damage to a heat fixing member or the like due to a decrease in hardness of an elastic member due to thermal deterioration.

[0010]

SUMMARY OF THE INVENTION Accordingly, a first aspect of the present invention is to provide first and second heat-fixing members each having an elastic member and pressed against each other so that the elastic members come into contact with each other. Heating means for heating at least one of the first and second heat-fixing members, wherein the developer on the transfer sheet inserted into the contact portion between the first and second heat-fixing members is melted by heating; In a fixing device for fixing a sheet, the first and second heat fixing members are maintained at a fixed distance to maintain a constant width of the contact portion, and at least an integrated value of a current supply time to the heating unit. A heat deterioration estimating means for estimating the degree of thermal deterioration of the elastic member based on the integrated energizing time; and a fixing condition correcting means for correcting the fixing condition according to the degree of heat deterioration estimated by the heat deterioration estimating means. Characterized by There is provided a wearing device.

The thermal deterioration estimating means estimates that, for example, the longer the integrated energizing time is, the more the thermal deterioration is progressing.

The fixing condition correcting means corrects, for example, at least the fixing speed.

More specifically, the fixing condition correcting means reduces the fixing speed as the integrated energizing time is longer.

When the hardness of the elastic member decreases due to thermal deterioration, the fixing property decreases when the transfer sheet is plain paper, and
In the case of an HP sheet, the light transmission color reproducibility is reduced. However, if the fixing speed is reduced as described above, the amount of heat supplied to the transfer sheet increases, so that good fixing properties and translucent color reproducibility can be obtained even when the hardness of the elastic member decreases. Therefore, it is possible to use a material having low heat resistance and high thermal conductivity as the elastic member, and maintain image quality, fixing property, and the like while setting the fixing speed higher.

The fixing condition correcting means decreases the fixing speed stepwise with respect to, for example, the integrated energizing time.

The fixing condition correcting means may correct at least the fixing temperature.

In this case, the fixing condition correcting means increases the fixing temperature as the integrated energizing time is longer.

When the fixing temperature increases, the amount of heat supplied to the transfer sheet increases, so that even if the hardness of the elastic member decreases,
Good fixability and translucent color reproducibility are obtained. for that reason,
As the elastic member, a material having low heat resistance and high heat conductivity can be used, and the fixing speed can be kept high. For this reason, fixability and translucent color reproducibility can be maintained without lowering productivity.

The fixing condition correcting means increases the fixing temperature stepwise with respect to, for example, the integrated energizing time.

In the case where the fixing condition correcting means corrects the fixing temperature, the fixing condition correcting means includes means for switching the fixing temperature to a plurality of set values. The time interval of the integrated energization time for increasing the temperature may be set to be short. The higher the fixing temperature, the faster the decrease in hardness due to thermal degradation.
Therefore, by correcting the fixing temperature in this way, it is possible to more reliably prevent a decrease in the fixing property and the transmissive color reproducibility due to the thermal deterioration.

In the case where the fixing condition correcting means corrects the fixing temperature, the fixing condition correcting means includes means for switching the fixing temperature to a plurality of set values. Alternatively, the increase width of the fixing temperature at one time may be set to be large. Even when the fixing temperature is corrected in this way, it is possible to more reliably prevent the fixing property and the transmissive color reproducibility from being deteriorated due to thermal deterioration.

The fixing device has a temperature detecting means for detecting a surface temperature of at least one of the first and second heat fixing members, and the fixing condition correcting means has at least a detecting means for detecting the temperature of the elastic member. At least one of the fixing speed and the fixing temperature may be further corrected based on the temperature. The higher the temperature of the elastic member, the faster the hardness decrease due to thermal degradation. Therefore, if the fixing speed and the fixing temperature are corrected in consideration of the surface temperature of the elastic member as described above, it is possible to more reliably prevent the fixing property and the light transmission color reproducibility from being deteriorated due to the thermal deterioration.

According to a second aspect of the present invention, each has an elastic member,
A first and second heat fixing member pressed against each other so that these elastic members come into contact with each other; and a heating unit for heating at least one of the first and second heat fixing members, wherein the first and second heat fixing members are heated. In a fixing device that heats and melts a developer on a transfer sheet that is inserted into a contact portion of a second heat fixing member and fixes the developer on the transfer sheet, at least one of the first and second heat fixing members includes: An elastic means for urging the first and second heat fixing members in a direction in which the first and second heat fixing members are pressed, and a constant distance between the first and second heat fixing members against the pressing force of the elastic means. Means for maintaining the contact portion between the first and second heat fixing members at a constant width, and a degree of thermal deterioration of the elastic member based on at least an integrated energizing time which is an integrated value of energizing time to the heating means. Thermal degradation estimating means for estimating Depending on the degree of the estimated thermal deterioration of reduction estimating means, there is provided a fixing device, characterized in that it comprises a pressing force adjusting means for adjusting the pressing force of the elastic means.

More specifically, the press-contact force adjusting means reduces the press-contact force of the elastic means as the integrated energizing time increases.

In the fixing device according to the second aspect of the present invention, a plurality of transfer sheets superimposed on each other are supplied to the contact portion at one time, or foreign matters are supplied to the contact portion, and the first and second heat fixing members are provided. When the force in the direction away from each other increases, the first and second heat fixing members separate from each other against the pressure contact force of the elastic means, and damage to the heat fixing member and the like can be prevented.

When the hardness of the elastic member decreases due to thermal deterioration, the strength of the elastic member also decreases with the change. First
When the pressure contact distance of the second heat fixing member is kept constant, the stress acting on the contact portion changes due to the change in the elasticity of the elastic member of the heat fixing member. The pressure contact force between the members becomes relatively high. In particular, when a plurality of transfer sheets or the like are supplied to the contact portion as described above, the heat fixing member is likely to be damaged. But,
In the second invention, since the pressing force adjusting means adjusts the pressing force according to the degree of thermal deterioration, even if the hardness of the elastic member decreases due to the thermal deterioration, the pressing width between the heat fixing members is kept constant. The balance between the stress of the contact portion and the pressure contact force of the elastic means is maintained, and when a plurality of transfer sheets or foreign matters superimposed on each other are supplied to the contact portion, the pressure force against the pressure contact force of the elastic means is suppressed. As a result, the first and second heat fixing members are reliably separated from each other, and damage to the heat fixing members and the like can be prevented.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention shown in the drawings will be described in detail.

(First Embodiment) A fixing device according to the first embodiment of the present invention shown in FIGS. 1 and 2 includes an upper frame 12 and a lower frame 13 connected by a pivot pin 11. The upper frame 12 and the lower frame 13 rotatably support a fixing roller 14 and a pressure roller 15, which are heating and fixing members, respectively.

An eccentric cam 18 driven by a motor 17 is in contact with the lower frame 13. By changing the rotation angle of the eccentric cam 18, as shown in FIG. 2A, the fixing roller 14 and the pressing roller 15 are pressed against each other, and as shown in FIG. The state in which the roller 14 and the pressure roller 15 are separated can be switched. Further, by adjusting the rotation angle of the eccentric cam 18, the center distance X (shown in FIG. 2A) between the fixing roller 14 and the pressure roller 15 is kept constant, and a nip portion described later is provided. 32 can be kept constant.

As shown in FIG. 1, the upper frame 12 is provided with a fixing roller 14, a cleaning roller 19, an oil application mechanism 20, a separation claw 21, and the like. The lower frame 13 is provided with a temperature sensor 33 for detecting the surface temperature of the silicon rubber layer 26 of the pressure roller 15, a pre-fixing guide 22, an oil scraping blade 23, a separation claw 24, and the like.

Each of the fixing roller 14 and the pressure roller 15 has a silicon rubber layer 26 as an elastic member provided on the outer periphery of a metal cylindrical body 25. The thermal conductivity of the silicone rubber layer 26 is set to be not less than 1.2 × 10 ⁻³ (cal / cm · sec · ° C.) and not more than 2.4 × 10 ⁻³ (cal / cm · sec · ° C.). . The silicone rubber layer 26 is made of JISC212
The hardness evaluated based on No. 3 is 70 or less.

A heater 27 as a heating means is accommodated inside the metal cylinder 25. A motor 28 is connected to the pressure roller 15. When the motor 28 is operated in the pressure contact state shown in FIG.
Rotate counterclockwise in the figure, and the fixing roller 14 is driven to rotate.

In the figure, a transfer sheet 30 such as plain paper or an OHP sheet having a developer image formed on the upper surface is supplied to a nip portion 32, where the fixing roller 14 and the pressure roller 1 are transferred.
By the rotation of No. 5, it is transported to the left in the figure. During this time, the developer on the transfer sheet 30 is heated and melted by the heat supplied from the silicone rubber layer 26, and is fixed on the transfer sheet 30 by the pressing force between the fixing roller 14 and the pressure roller 15.

In FIG. 1, reference numeral 35 denotes a control unit which constitutes a thermal deterioration estimating unit and a fixing condition correcting unit in the present invention. The control unit 35 includes the motors 17 and 28, the heater 27 and the temperature sensor 33. It is connected.

In the fixing device of the first embodiment, the silicon rubber layer 26 of the fixing roller 14 and the pressure roller 15 has a heat transfer coefficient of 1.2 × 10 ⁻³ (cal / cm · sec ·
C) or more and 2.4 × 10 ⁻³ (cal / cm · sec · ° C.) or less, to increase the content of the high heat transfer filler, as shown in FIG. As the integrated value of the energization time to the heater 27 (integrated energization time) increases, the roller hardness decreases. As described above, since the axial distance X between the fixing roller 14 and the pressure roller 15 is set to be constant, the width of the nip width 32 is constant even if the roller hardness decreases. However, the pressing force acting on the nip portion 32 due to the elasticity of the fixing roller 14 and the pressure roller 14 is reduced due to a temporal decrease in hardness as shown in Table 1.

[0036]

[Table 1]

When the transfer sheet 30 is made of plain paper, the decrease in the pressing force causes a decrease in the fixing property.
When 0 is an OHP sheet, the transmissive color reproducibility is reduced. In the first embodiment, the control unit 35 executes the operations shown in the flowcharts of FIG. 4 to FIG. 7 in order to eliminate the influence of the decrease in hardness due to such thermal deterioration.

First, the control unit 35 measures the energization time shown in FIG. If the fixing operation is being performed in step S4-1 and the heater 27 is energized in step S4-2, the temperature of the silicon rubber layer 26 of the pressure roller 15 is detected by the temperature sensor 33 in step S4-3. To detect.

Next, in step S4-4, if the detected temperature t is equal to or higher than the predetermined temperature t _const , the process proceeds to step S4-4.
The timer is started at 4-5, and the time measurement is continued until it is detected at step S4-6 that power is not being supplied. If it is detected in step S4-6 that power is not being supplied, the timer is stopped in step S4-7, and step S4-8 is performed.
The current energizing time TM is read. Step S4-
In step 9, an integrated value of the energizing time TM (integrated energizing time ATM) is calculated and stored in step S4-10.

The fixing operation shown in FIG. 5 will be described.
First, in step S5-1, it is determined whether the copy mode is the plain paper mode or the OHP mode.

If the mode is the plain paper mode in step S5-1, the flow shifts to step S5-2 to execute fixing speed correction in the plain paper mode. In step S5-2, the fixing speed is corrected according to the integrated heating time ATM based on Table 2 below.

[0042]

[Table 2]

First, in step S6-1 of FIG.
Check the accumulated energizing time ATM. If the accumulated energization time ATM is less than 200 hours in step S6-2, it is determined in step S6-3 that the fixing speed is not corrected. If the accumulated energization time ATM is not less than 200 hours in step S6-2, the process proceeds to step S6-4. Step S6-
If the cumulative energizing time ATM is less than 800 hours in step 4, the fixing speed is reduced by 2% in step S6-5. Step S
If the accumulated energization time ATM is not less than 800 hours in 6-4, the process proceeds to step S6-6. If the accumulated energization time ATM is less than 2000 hours in step S6-6, the fixing speed is reduced by 4% in step S6-7. Step S6
If it is determined in step -6 that the accumulated energizing time ATM is not less than 2000 hours, the process proceeds to step S6-8. If the accumulated energization time ATM is less than 5000 hours in step S6-8, the fixing speed is reduced by 6% in step S6-9, and if not, the fixing speed is reduced by 8% in step S6-10.

On the other hand, if the copy mode is the OHP mode in step S5-1 in FIG. 5, the flow shifts to step S5-3 to execute the fixing speed correction in the OHP mode. In step S5-3, the fixing speed is corrected according to the integrated heating time ATM based on Table 3 below.

[0045]

[Table 3]

First, in step S7-1 in FIG.
Check the accumulated energizing time ATM. If the accumulated energization time ATM is less than 200 hours in step S7-2, it is determined in step S7-3 that the fixing speed is not corrected. If the accumulated energization time ATM is not less than 200 hours in step S7-2, the process proceeds to step S7-4. Step S7-
If the accumulated time ATM is less than 800 hours in step 4, the fixing speed is reduced by 3% in step S7-5. Step S7-
If the accumulated time ATM is not less than 800 hours in step 4, the process proceeds to step S7-6. If the accumulated time ATM is less than 2000 hours in step S7-6, step S7-7.
Reduces the fixing speed by 6%. If the accumulated time ATM is not less than 2,000 hours in step S7-6, step S7
Move to -8. In step S7-8, the integrated energizing time AT
If M is less than 5000 hours, the fixing speed is reduced by 9% in step S7-9, and if M is not less than 5000 hours, the fixing speed is reduced by 12% in step S7-10.

After the fixing speed is corrected in accordance with the integrated energizing time ATM by changing the conditions depending on the type of the transfer sheet as described above, the fixing operation is executed in step S5-4 in FIG.

In the first embodiment, as described above, the thermal conductivity of the silicone rubber layer 26 of the fixing roller 14 and the pressure roller 15 is set to 1.2 × 10 ⁻³ (cal / cm · sec · ° C.) or more. 4
Since it is set to a high value of × 10 ⁻³ (cal / cm · sec · ° C.) or less, the silicon rubber layer 26
Heat is efficiently transmitted to the surface. Therefore, it is possible to prevent the surface temperature of the elastic member 2 from temporarily lowering at the start of the continuous paper passing, and to set the fixing speed to a high speed.

In the first embodiment, as described above, the fixing speed is reduced as the integrated energizing time ATM increases, that is, as the hardness of the silicon rubber layer 26 decreases due to thermal deterioration. When the fixing speed is reduced, the transfer sheet 30 is moved to the nip portion 3 between the fixing roller 14 and the pressure roller 15.
2, the amount of heat supplied from the fixing roller 14 and the pressure roller 15 to the transfer sheet 30 increases. Therefore, in the first embodiment, as described above, the silicone rubber layer 2 of the fixing roller 14 and the pressure roller 15
6 can be compensated for the shortage of heat supply to the transfer sheet 30 which cannot be avoided when the heat conductivity of the silicon rubber layer 26 is set to be high and the hardness of the silicon rubber layer 26 is reduced due to the thermal deterioration. Therefore, in the fixing device of the first embodiment, good fixability is obtained for plain paper, and good translucent color reproducibility is obtained for OHP sheets.

(Second Embodiment) Next, a second embodiment of the present invention will be described. In the second embodiment, the influence of the decrease in the heat supplied to the transfer sheet 30 due to the decrease in hardness due to the thermal deterioration of the silicon rubber layer 26 is determined by the fixing roller 1.
4 and the surface temperature (fixing temperature) of the silicon rubber layer 26 of the pressure roller 15 is corrected.

The mechanical structure of the fixing device of the second embodiment is the same as that of the first embodiment shown in FIG. 1, and the silicone rubber layer 26 of the fixing roller 14 and the pressure roller 15 is As in the first embodiment, 1.2 × 10 ⁻³ (cal /
cm · sec · ° C) or more 2.4 × 10 ^-3 (cal / cm · sec · ° C)
It has the following high thermal conductivity. Further, the fixing temperature before correction is 160 ° C. in both the case where the transfer sheet is plain paper and the case where the transfer sheet is an OHP sheet.

The fixing operation shown in FIG. 8 will be described.
First, if the copy mode is the plain paper mode in step S8-1, the process proceeds to step S8-2 to execute the fixing temperature correction in the plain paper mode. In this step S8-2,
Based on FIG. 9 and Table 4 below, the fixing temperature is corrected according to the accumulated energizing time ATM.

[0053]

[Table 4]

First, in step S10-1 of FIG. 10, the integrated energization time ATM is checked. Step S10-
If the accumulated energization time ATM is less than 200 hours in 2, it is determined in step S10-3 that the fixing temperature is not corrected. In step S10-2, the accumulated energizing time ATM is 200
If it is not less than the time, the process proceeds to step S10-4. If the accumulated time ATM is less than 800 hours in step S10-4, the fixing temperature is set to 1.5 in step S10-5.
℃ rise. If the accumulated time ATM is not less than 800 hours in step S10-4, the process proceeds to step S10-6. In step S10-6, the accumulated time ATM is 200
If less than 0 hours, the fixing temperature is increased by 3 ° C. in step S10-7. In step S10-6, the accumulated time ATM
If not less than 2000 hours, step S10-8
Move to In step S10-8, the accumulated time ATM is 5
If it is less than 000 hours, the fixing temperature is increased by 4.5 ° C. in step S10-9, and if it is not less than 5000 hours, the fixing temperature is increased by 6 ° C. in step S10-10.

On the other hand, if the copy mode is the OHP mode in step S8-1 in FIG. 8, the flow shifts to step S8-3 to execute the fixing speed correction in the OHP mode. In step S8-3, the fixing speed is corrected according to the integrated energizing time ATM based on FIG. 9 and Table 5 below.

[0056]

[Table 5]

First, in step S11-1 of FIG. 11, the accumulated energizing time ATM is checked. Step S11-
If the accumulated energization time ATM is less than 200 hours in step 2, it is determined in step S11-3 that the fixing temperature is not corrected. In step S11-2, the accumulated energizing time ATM is 200
If it is not less than the time, the process proceeds to step S11-4. If the accumulated time ATM is less than 800 hours in step S11-4, the fixing temperature is set to 2.5 in step S11-5.
℃ rise. If the accumulated time ATM is not less than 800 hours in step S11-4, the process proceeds to step S11-6. In step S11-6, the accumulated time ATM is 200
If less than 0 hours, the fixing temperature is increased by 5.0 ° C. in step S11-7. In step S11-6, the accumulated time A
If TM is not less than 2000 hours, step S11-
Move to 8. In step S11-8, the integrated energizing time AT
If M is less than 5000 hours, the fixing temperature is increased by 7.5 ° C. in step S11-9, and if M is not less than 5000 hours, the fixing temperature is increased by 10 ° C. in step S11-10.

After the fixing temperature is corrected by changing the conditions depending on the type of the transfer sheet as described above, the fixing operation is executed in step S8-4 in FIG. In the second embodiment,
As in the first embodiment, the thermal conductivity of the silicon rubber layer 26 is set to 1.2 × 10 ⁻³ (cal / cm · sec · ° C.) or more to 2.4.
Since the value is set to a high value of × 10 ⁻³ (cal / cm · sec · ° C.) or less, the heat transfer efficiency to the surface of the silicon rubber layer 26 is good. Therefore, at the start of continuous paper feeding, the elastic member 2
Can be prevented from temporarily lowering, and the fixing speed can be set to a high speed.

In the second embodiment, as described above, the fixing temperature is increased as the integrated energizing time ATM increases, that is, as the hardness of the silicon rubber layer 26 decreases due to thermal degradation. When the fixing temperature is increased, the amount of heat supplied to the transfer sheet 30 from the fixing roller 14 and the pressure roller 15 increases. Therefore, in the second embodiment, when the thermal conductivity of the silicon rubber layer 26 of the fixing roller 14 and the pressure roller 15 is set to be high as described above, the pressure contact force is reduced due to thermal deterioration which cannot be avoided. The shortage of heat supply supplied to the transfer sheet 30 can be compensated. Therefore, in the fixing device of the second embodiment, good fixability can be obtained for plain paper, and good translucent color reproducibility can be obtained for OHP sheets.

In the second embodiment, as shown in FIG. 9, the set value of the fixing temperature is the same in both the plain paper mode and the OHP mode, and the fixing temperature is increased at time intervals. . However, a means for switching the fixing temperature to a plurality of set values is provided, and as shown in FIG.
The time interval until the fixing temperature is increased in the case of 1 (for example, from the integrated energizing time ATM1 to the integrated energizing time A in FIG. 12).
The time interval until the fixing temperature in the case of the low temperature set value t2 is increased (for example, FIG. 12).
(Time interval from the integrated energizing time ATM2 to the integrated energizing time ATM4). The higher the fixing temperature, the faster the elasticity of the silicone rubber layer 26 decreases due to thermal deterioration. Therefore, by correcting the fixing temperature as shown in FIG. 12, it is possible to more reliably prevent a decrease in fixability on plain paper and a decrease in translucent color reproducibility on OHP sheets due to thermal deterioration.

Further, as shown in FIG. 13, the higher the set value of the fixing temperature is, the larger the increase width a of the fixing temperature in one fixing temperature correction may be set. The higher the fixing temperature, the faster the elasticity of the silicone rubber layer 26 decreases due to thermal deterioration. Therefore, by correcting the fixing temperature as shown in FIG. 13, the shortage of heat supply to the elastic member caused by the thermal deterioration is compensated, and the fixing property of the plain paper is reduced and the OH is reduced.
It is possible to more reliably prevent a reduction in transmissive color reproducibility in the P sheet.

(Third Embodiment) A third embodiment of the present invention has the same configuration as that of the first embodiment described above.
The fixing speed correction in the plain paper mode in step S5-2 and the fixing speed correction in the OHP mode in step S5-3 are different from those in the first embodiment.

FIG. 14 shows the correction of the fixing speed in the plain paper mode in the third embodiment. In FIG.
Steps S14-1 to S14-10 are the same as those in FIG.
The first step shown in steps S6-1 to S6-10 of FIG.
This is the same as in the embodiment. First, the correction amount of the fixing speed is determined only from the integrated energizing time ATM.

Next, in step S14-11, the control
The control unit 35 reads the temperature detected by the temperature sensor 33. Stay
In step S14-12, the detection temperature t and the fixing temperature are set.
Value t _SET(In this embodiment, 160 ° C.) difference Δt is calculated.
You.

Next, in steps S14-13 to S14-21, the correction amount of the fixing speed is corrected according to the temperature difference Δt.

First, in step S14-13, if the accumulated energization time ATM is less than 200 hours, the temperature difference Δt is determined in step S14-14 based on Table 6 below.
Further, the fixing speed is further corrected according to.

[0067]

[Table 6]

In step S14-14, the temperature difference Δt is 0
When the temperature is in the range of -2.5 ° C, the fixing speed is not corrected, and the fixing operation is performed at the fixing speed corrected in steps S14-1 to S14-10. The temperature difference Δt is-
In the range of 2.5 to -5 ° C, the fixing speed is further increased by 3.
If the temperature difference Δt is −5 ° C. or more, the fixing speed is further reduced by 7%.

In step S14-13, the integrated energizing time AT
If M is not less than 200 hours, step S14-1
Move to 5. In step S12-15, the accumulated energizing time A
If TM is less than 800 hours, step S12-16
Then, based on Table 7 below, the fixing speed is corrected according to the temperature difference Δt.

[0070]

[Table 7]

In step S14-16, the temperature difference Δt is set to 0
When the temperature difference Δt is in the range of −2.5 to −5 ° C., the fixing speed is further reduced by 2% when the temperature difference Δt is in the range of −2.5 to −5 ° C.
The fixing speed is further reduced by 5.5% and the temperature difference Δt is −5 ° C.
Above this, the fixing speed is further reduced by 9%.

In step S14-15, the integrated energizing time AT
If M is not less than 800 hours, step S14-
Move to 17. If it is determined in step S14-17 that the accumulated energization time ATM is less than 2000 hours, the flow proceeds to step S14-.
At 18, the fixing speed is corrected according to the temperature difference Δt based on Table 8 below.

[0073]

[Table 8]

In step S14-14, the temperature difference Δt is set to 0.
When the temperature difference Δt is in the range of −2.5 to −5 ° C., the fixing speed is further reduced by 4% when the temperature difference Δt is in the range of −2.5 to −5 ° C.
The fixing speed is further reduced by 7.5%, and the temperature difference Δt is −5 ° C.
If above, the fixing speed is further reduced by 11%.

In step S14-17, the integrated energizing time AT
If M is not less than 2000 hours, step S14
Move on to -19. If the accumulated energization time ATM is less than 5000 hours in step S14-19, step S14
At -20, the fixing speed is corrected according to the temperature difference Δt based on Table 9 below. On the other hand, if the accumulated energization time ATM is not less than 5000 hours in step S14-19,
In step S14-21, the fixing speed is corrected according to the temperature difference Δt based on Table 10 below.

[0076]

[Table 9]

[0077]

[Table 10]

At step S14-20, the temperature difference Δt is 0
When the temperature is in the range of -2.5 ° C, the fixing speed is further reduced by 6%. When the temperature difference Δt is in the range of -2.5 to -5 ° C,
The fixing speed is further reduced by 9.5%, and the temperature difference Δt is −5 ° C.
If above, the fixing speed is further reduced by 13%.

In step S12-21, the temperature difference Δt is 0
When the temperature difference Δt is in the range of −2.5 to −5 ° C., the fixing speed is further reduced by 8% when the temperature difference Δt is in the range of −2.5 to −5 ° C.
The fixing speed was further reduced by 11.5%, and the temperature difference Δt was −5.
If the temperature is not lower than ° C, the fixing speed is further reduced by 15%.

In Tables 6 to 10, as the temperature difference Δt increases, the fixing speed is greatly reduced. As is clear from comparison of Table 6 to Table 10, the longer the cumulative energizing time ATM is, the more the temperature difference Δt becomes from 0 to -2.5 ° C,
The amount of reduction in the fixing speed corresponding to each range of 2.5 to -5 ° C and -5 ° C or higher is also large. The larger the temperature difference Δt between the set value of the fixing temperature and the temperature T detected by the temperature sensor 33, the higher the actual surface temperature of the silicon rubber layer 26, and the lower the elasticity due to thermal deterioration. Therefore, by lowering the fixing speed in accordance with the magnitude of the temperature difference Δt as described above, it is possible to more reliably prevent the fixing performance from being deteriorated due to the thermal deterioration of the silicone rubber layer 26. Further, in the third embodiment, since the amount of reduction in the fixing speed corresponding to each range of the temperature difference Δt is made different according to the integrated energization time ATM, it is possible to more reliably prevent the fixing performance from being lowered.

FIG. 15 shows fixing speed correction in the OHP mode in the third embodiment. In FIG.
Steps S15-1 to S15-10 are the same as those in FIG.
The first step shown in steps S7-1 to S7-10 of FIG.
As in the case of the embodiment, first, the integrated energizing time AT
The correction amount of the fixing speed is determined only from M.

Next, in step S15-11, the control unit 35 reads the detected temperature t of the temperature sensor 33, and calculates the temperature difference Δt in step S15-12.

Next, in steps S15-13 to S15-21, the correction amounts of the fixing speed and the fixing temperature are corrected according to the temperature difference Δt.

First, in step S15-13, if the accumulated energizing time ATM is less than 200 hours, the temperature difference Δ is determined in step S15-14 based on Table 11 below.
The fixing speed is corrected according to t.

[0085]

[Table 11]

In step S15-14, the temperature difference Δt is 0
When the temperature is in the range of -2.5 ° C, the fixing speed is not corrected, and the fixing operation is performed at the fixing speed corrected in steps S15-1 to S15-10. The temperature difference Δt is-
In the range of 2.5 to -5 ° C, the fixing speed is further increased by 5%.
If the temperature difference Δt is −5 ° C. or more, the fixing speed is further reduced by 10%.

In step S15-13, the integrated energizing time AT
If M is not less than 200 hours, step S15-1
Move to 5. In step S15-15, the accumulated energizing time A
If the TM is less than 800 hours, step S15-16
Based on Table 12 below, the fixing speed and the fixing temperature are corrected according to the temperature difference Δt.

[0088]

[Table 12]

In step S15-16, the temperature difference Δt is 0
If it is in the range of -2.5 ° C, the fixing temperature is increased by 2.5 ° C. If the temperature difference Δt is in the range of −2.5 to −5 ° C., the fixing temperature is increased by 2.5% ° C., and the fixing speed is set to 5.5.
%. If the temperature difference Δt is −5 ° C. or more, the fixing temperature is increased by 2.5% and the fixing speed is reduced by 10%.

In step S15-15, the integrated energizing time AT
If M is not less than 800 hours, step S15-
Move to 17. If it is determined in step S15-17 that the accumulated energization time ATM is less than 2,000 hours, step S15-
At 18, the fixing speed and the fixing temperature are corrected according to the temperature difference Δt based on Table 13 below.

[0091]

[Table 13]

In step S15-18, the temperature difference Δt is set to 0.
If it is in the range of -2.5 ° C, the fixing temperature is increased by 5.0 ° C. If the temperature difference Δt is in the range of −2.5 to −5 ° C., the fixing temperature is increased by 5.0 ° C., and the fixing speed is reduced by 5%. If the temperature difference Δt is −5 ° C. or more, the fixing temperature is increased by 5.0 ° C., and the fixing speed is reduced by 10%.

In step S15-17, the integrated energizing time AT
If M is not less than 2000 hours, step S15
Move on to -19. If the accumulated energization time ATM is less than 5000 hours in step S15-19, step S15
In -20, the fixing speed and the fixing temperature are corrected according to the temperature difference Δt based on Table 14 below. On the other hand, if the accumulated energization time ATM is not less than 5000 hours in step S15-19, the fixing speed and the fixing temperature are corrected in step S15-21 according to the temperature difference Δt based on Table 15 below.

[0094]

[Table 14]

[0095]

[Table 15]

In step S15-20, the temperature difference Δt is 0
If it is in the range of -2.5 ° C, the fixing temperature is increased by 7.5 ° C. If the temperature difference Δt is in the range of −2.5 to −5 ° C., the fixing temperature is increased by 7.5% and the fixing speed is reduced by 5%. If the temperature difference Δt is −5 ° C. or more, the fixing temperature is increased by 7.5 ° C., and the fixing speed is reduced by 10%.

In step S15-21, the temperature difference Δt is 0
If it is in the range of -2.5 ° C, the fixing temperature is increased by 10.0 ° C. If the temperature difference Δt is in the range of −2.5 to −5 ° C., the fixing temperature is increased by 10.0 ° C., and the fixing speed is reduced by 5%. If the temperature difference Δt is −5 ° C. or more, the fixing temperature is increased by 10.0 ° C., and the fixing speed is reduced by 10%.

In Tables 11 to 15, the larger the temperature difference Δt is, the more the fixing speed is reduced. Also,
As is clear from comparison of Table 11 to Table 15, the longer the cumulative energization time ATM is, the more the temperature difference Δt is 0 to −2.5 ° C.
The amount of decrease in the fixing speed corresponding to each of the range of −2.5 to −5 ° C. and −5 ° C. or more is large, and the amount of increase in the fixing temperature is large. As the temperature difference Δt between the set value of the fixing temperature and the detected fixing temperature is larger, the temperature of the silicon rubber layer 26 is higher and the elasticity is reduced by thermal degradation. As a result, the fixing speed and the transmissive color reproducibility due to the thermal deterioration of the silicone rubber layer 26 can be more reliably prevented. Further, since the amount of decrease in the fixing speed and the amount of increase in the fixing temperature corresponding to each range of the temperature difference Δt are made different in accordance with the integrated energizing time ATM, the fixing property and the transmissive color reproducibility are more reliably reduced. Can be prevented.

(Fourth Embodiment) A fourth embodiment of the present invention has the same configuration as that of the above-described second embodiment.
The fixing temperature correction in the plain paper mode in step S8-2 and the fixing temperature correction in the OHP mode in step S8-3 are different from those in the second embodiment.

FIG. 16 shows the fixing temperature correction in the plain paper mode in the fourth embodiment. In FIG.
Steps S16-1 to S16-10 are the same as those in FIG.
In the same manner as in the second embodiment from step S10-1 to step S10-10 of 0, first, the correction amount of the fixing temperature is determined only from the integrated energizing time ATM.

Next, in step S16-11, the control section 35 reads the detected temperature of the temperature sensor 33, and in step S16-12, calculates the difference Δt between the detected temperature t and the set value t _SET of the fixing temperature. .

Next, in steps S16-13 to S16-21, the fixing speed is corrected according to the temperature difference Δt.

First, in step S16-13, if the accumulated energizing time ATM is less than 200 hours, the fixing speed is corrected according to the temperature difference Δt based on Table 6 in step S16-14.

In step S16-13, the integrated energizing time AT
If M is not less than 200 hours, step S16-1
Move to 5. In step S16-15, the integrated energizing time A
If the TM is less than 800 hours, Step S16-16
Based on Table 7, the fixing speed is corrected according to the temperature difference Δt.

In step S16-15, the integrated energizing time AT
If M is not less than 800 hours, step S16-1
Move to 7. In step S16-17, the integrated energizing time A
If TM is less than 2000 hours, step S16-1
In step 8, based on Table 8, the fixing speed is corrected according to the temperature difference Δt.

In step S16-17, the integrated energizing time AT
If M is not less than 2000 hours, step S16-
Move to 19. If the accumulated energization time ATM is less than 5000 hours in step S16-19, step S16-
In step 20, based on Table 9, the fixing speed is corrected according to the temperature difference Δt. In step S16-19, the integrated energizing time A
If the TM is 5000 hours or more, the fixing speed is corrected according to the temperature difference Δt based on Table 9 above.

As described above, if the fixing temperature is corrected in accordance with the integrated energizing time ATM and the fixing speed is further corrected in accordance with the temperature difference Δt, the silicon rubber layer 2 due to thermal deterioration can be obtained.
6, it is possible to more reliably reduce the influence of the decrease in hardness.
Better fixability can be obtained.

FIG. 17 shows the fixing temperature correction in the OHP mode in the fourth embodiment. In FIG.
Steps S17-1 to S17-10 are the same as those in FIG.
This is the same as the case of the second embodiment shown in Steps S11-1 to S11-10 of the first embodiment. First, the correction amount of the fixing temperature is determined only from the integrated energizing time ATM.

Next, in step S17-11, the control unit 35 reads the temperature detected by the temperature sensor 33, and calculates the temperature difference Δt in step S17-12.

Next, in steps S17-13 to S17-21, the fixing speed and the fixing temperature are corrected according to the temperature difference Δt.

First, in step S17-13, if the accumulated energizing time ATM is less than 200 hours, the fixing speed is corrected according to the temperature difference Δt in step S17-14 based on Table 11 above.

In step S17-13, the integrated energizing time AT
If M is not less than 200 hours, step S17-1
Move to 5. In step S15-15, the accumulated energizing time A
If the TM is less than 800 hours, step S17-16
Based on Table 12, the fixing speed and the fixing temperature are corrected according to the temperature difference Δt.

In step S17-15, the integrated energizing time AT
If M is not less than 800 hours, step S17-1
Move to 7. In step S17-17, the integrated energizing time A
If TM is less than 2000 hours, step S17-1
In step 8, based on Table 13, the fixing speed and the fixing temperature are corrected in accordance with the temperature difference Δt.

In step S17-17, the integrated energizing time AT
If M is not less than 2000 hours, step S17-
Move to 19. If it is determined in step S17-19 that the accumulated energization time ATM is less than 5000 hours, step S17-
In step 20, the fixing speed and the fixing temperature are corrected according to the temperature difference Δt based on Table 14 above. If the cumulative energization time ATM is 5000 hours or more in step S17-19, the fixing speed and the fixing temperature are corrected according to the temperature difference Δt based on Table 15 above.

As described above, if the fixing temperature is corrected in accordance with the accumulated energizing time ATM and the fixing speed and the fixing temperature are further corrected in accordance with the temperature difference Δt, the hardness of the silicon rubber layer 26 is reduced due to thermal deterioration. More reliably reduce the impact of
Better translucent color reproducibility can be obtained.

(Fifth Embodiment) FIGS. 18 and 19 show a fifth embodiment of the present invention.

The lower end of the lower frame 13 is connected to the upper end of a spring 40 in the figure, and a cam plate 41 is fixed to the lower end of the spring 40 in the figure. Cam plate 4
Reference numeral 1 is in contact with an eccentric cam 43 driven to rotate by a motor 42. The upper end of the lower frame 13 is provided with an upwardly protruding portion 13a.

18 and 19, the cleaning roller 19 provided on the upper frame 12, the oil application mechanism 20 and the like, the pre-fixing guide 22 provided on the lower frame 13, the oil scraping blade 23, the separating claw 24
Etc. are omitted.

The spring 40 urges the lower frame 13 against the upper frame 12. In the pressure contact state shown in FIG. 18, the protrusion 13 a abuts on the lower portion of the upper frame 12, so that the center distance X is kept constant, and as a result, the width of the nip 32 is also kept constant.

In the pressure-contact state shown in FIG. 18, when a plurality of transfer sheets 30 overlapping each other are supplied to the nip portion 32, or when foreign matter is supplied to the nip portion 32 together with the transfer sheet 30, the nip portion 32 When the force for moving the fixing roller 14 and the pressure roller 15 acting in the direction to separate from each other exceeds the pressure contact force of the spring 40, the lower frame 13 rotates counterclockwise in the figure, and the fixing roller 1
4 and the pressure roller 15 are separated from each other.

By finely adjusting the rotation angle of the eccentric cam 43 in the pressure contact state shown in FIG. 18, the spring 40 presses the lower frame 13 against the upper frame 14 to press the fixing roller 14 and the pressure roller 15 against each other. The power can be adjusted. For example, when the eccentric cam 43 at the rotation angle position shown in FIG.
When the eccentric cam 43 is rotated in the direction indicated by the arrow X2, the force with which the spring 40 presses the fixing roller 14 and the pressure roller 15 decreases.

Further, the rotational angle position of the eccentric cam 43 is shown in FIG.
9, the fixing roller 14 and the pressure roller 15 are separated from each other.

Next, the operation of the fifth embodiment will be described.
As in the first to fourth embodiments, the control unit 35 executes the operation shown in the flowchart of FIG. 4 to calculate the integrated energization time ATM.

The control unit 35 calculates the integrated energizing time A
The lower frame 13 is connected to the upper frame 14 according to the TM.
Adjust the biasing force against. First, in step S20-1 of FIG. 20, the control unit 35 sets the integrated energization time AT
Check M.

Next, in step S20-2, the correction amount of the pressing force is determined according to the accumulated energizing time ATM. The longer the cumulative energizing time ATM is, the more the hardness of the silicon rubber layer 26 is reduced due to thermal deterioration. When the hardness of the silicone rubber layer 26 decreases, the strength of the silicone rubber layer 26 with respect to the stress generated in the nip 32 between the fixing roller 14 and the pressure roller 15 decreases.

With respect to the stress of the nip portion 32, the spring 40
Is too large, the transfer sheets 30 are supplied to the nip portion 32 in a state where the transfer sheets 30 overlap each other,
When foreign matter is supplied to the nip portion 32 together with the transfer sheet 30, an excessive load is applied between the fixing roller 14, the pressure roller 15, and the upper frame 12 and the lower frame 13, and these may be damaged. . On the other hand, the nip 3
If the pressing force of the spring 40 is too small with respect to the stress of 2, the transfer sheet may fail to pass.

For this reason, in step S20-2,
As shown in Table 16, the larger the integrated energizing time ATM is, the more the spring 40 becomes, as shown in Table 16, in order to prevent the pressing force from becoming too large with respect to the stress of the nip portion 32 which decreases due to the hardness caused by thermal deterioration. A correction amount for reducing the pressing force is determined.
The correction amount is set so that the pressure contact force does not become too small with respect to the stress of the nip portion 32.

[0128]

[Table 16]

In step S20-3, the control unit 35 controls the spring 40 so that the pressing force of the spring 40 is reduced by the correction amount.
The motor 42 is driven to adjust the rotational angle position of the eccentric cam 43. Thereafter, in step S20-4, a fixing operation is performed.

As described above, in the fixing device of the fifth embodiment,
Since the contact force of the spring 40 is reduced according to the decrease in the hardness of the silicone rubber layer 26 of the fixing roller 14 and the pressure roller 15 due to the thermal degradation, even if the hardness of the silicone rubber layer 26 is reduced by the thermal degradation. The balance between the stress of the nip 32 between the fixing roller 14 and the pressure roller 15 and the contact force of the spring 40 is maintained. Therefore, the fixing roller 14 and the pressure roller 15 are reliably separated from each other when foreign matter or the like is supplied, so that the fixing roller 14 and the pressure roller 15 can be prevented from being damaged. Further, it is possible to prevent the occurrence of paper passing failure due to insufficient pressing force of the spring 40.

In the fixing device of the fifth embodiment,
As in the first to fourth embodiments, the fixing temperature and the fixing speed may be corrected in accordance with the integrated energizing time ATM and the temperature difference Δt.

In the first to fifth embodiments, as shown in FIG. 21, when the detected fixing temperature is the same as the set temperature, the time measured by the timer (step S4 in FIG. 4). -1 to step S4-10) are directly integrated as the energizing time TM1, and when the fixing temperature detection value is higher than the set temperature by 10 ° C. or more, the time measured by the timer is multiplied by a coefficient exceeding 1. When the fixing temperature detected value is lower than the set temperature, the corrected time is multiplied by a coefficient of a predetermined value from 0 to less than 1 to correct the corrected time. The energization time TM1 '' may be used.

The higher the actual fixing temperature is, the lower the elasticity of the silicone rubber layer 26 becomes due to the thermal deterioration. Therefore, the time measured by the timer is corrected according to the detected temperature t as described above. In addition, a decrease in the hardness of the silicone rubber layer 26 due to thermal deterioration can be estimated with higher accuracy.

[0134]

As is apparent from the above description, in the fixing device of the first invention, the fixing conditions such as the fixing speed and the fixing temperature are corrected in accordance with the decrease in hardness due to the thermal deterioration of the elastic member. For this reason, it is possible to prevent a decrease in fixability when the transfer sheet is plain paper due to a decrease in hardness of the elastic member, and a decrease in translucent color reproducibility when the transfer sheet is an OHP sheet. Therefore, in the fixing device according to the first aspect of the invention, it is possible to increase the fixing efficiency by using a material having poor heat resistance but high thermal conductivity as the elastic member.

In the fixing device according to the second aspect of the present invention, the pressing force of the first and second heat fixing members is reduced in accordance with a decrease in hardness of the elastic member due to thermal deterioration.
Even if the hardness of the elastic member or the strength of the elastic member is reduced due to thermal deterioration, damage to the heat-fixing member and the like due to simultaneous supply of a plurality of transfer sheets stacked on each other to the contact portion. It can be reliably prevented.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating a fixing device according to a first embodiment of the present invention.

FIG. 2A is a schematic diagram showing a fixing device in a pressed state;
FIG. 3B is a schematic diagram illustrating the fixing device in a separated state.

FIG. 3 is a diagram showing a relationship between the hardness of the silicon rubber layer 26 and the integrated energizing time.

FIG. 4 is a flowchart for explaining the operation of the control unit to measure the accumulated energization time.

FIG. 5 is a flowchart illustrating a fixing operation according to the first exemplary embodiment of the present invention.

FIG. 6 is a flowchart showing a subroutine of step S5-2 in FIG. 5;

FIG. 7 is a flowchart showing a subroutine of step S5-3 in FIG.

FIG. 8 is a flowchart illustrating a fixing operation according to a second exemplary embodiment of the present invention.

FIG. 9 is a diagram illustrating a relationship between an integrated energizing time and a fixing temperature.

FIG. 10 is a flowchart showing a subroutine of step S8-2 in FIG. 8;

FIG. 11 is a flowchart showing a subroutine of step S8-3 in FIG.

FIG. 12 is a diagram showing another column of the fixing temperature correction in the second embodiment.

FIG. 13 is a diagram showing another example of fixing temperature correction in the second embodiment.

FIG. 14 is a flowchart illustrating fixing speed correction in a plain paper mode according to the third embodiment.

FIG. 15 is a flowchart illustrating fixing speed correction in the OHP mode according to the third embodiment.

FIG. 16 is a flowchart illustrating fixing temperature correction in a plain paper mode according to a fourth embodiment.

FIG. 17 is a flowchart illustrating fixing temperature correction in an OHP mode according to a fourth embodiment.

FIG. 18 is a schematic configuration diagram illustrating a pressing state of a fixing device according to a fifth embodiment.

FIG. 19 is a schematic configuration diagram illustrating a separated state of a fixing device according to a fifth embodiment.

FIG. 20 is a flowchart for explaining the operation of the fifth embodiment.

FIG. 21 is a diagram for explaining correction of an energization time.

FIG. 22 is a schematic configuration diagram illustrating a conventional fixing device.

[Explanation of symbols]

 Reference Signs List 14 Fixing roller 15 Pressure roller 17, 28, 42 Motor 18, 43 Eccentric cam 25 Metal cylinder 26 Silicon rubber layer (elastic member) 27 Heater (heating means) 33 Temperature sensor 35 Control unit 40 Spring 41 Cam plate

Continued on the front page (72) Inventor Tetsuya Yamada 2-3-13 Azuchicho, Chuo-ku, Osaka-shi, Osaka Inside Osaka International Building Minolta Co., Ltd. (72) Taizo Onishi 2--3, Azuchicho, Chuo-ku, Osaka-shi, Osaka No. 13 Osaka International Building Minolta Co., Ltd. F-term (reference) 2H033 AA23 AA45 BA30 CA20 CA26 CA30 CA36 CA39

Claims (13)

[Claims] 1. An image forming apparatus comprising: a first and a second heat fixing member having an elastic member and pressed against each other so that the elastic members come into contact with each other; and heating at least one of the first and second heat fixing members. A heating unit that heats and melts the developer on the transfer sheet that is inserted into the contact portion of the first and second heat-fixing members, and fixes the developer on the transfer sheet. (2) means for holding the heat fixing member at a constant distance to keep the width of the contact portion constant, and a degree of thermal deterioration of the elastic member based on at least an integrated energizing time which is an integrated value of energizing time to the heating means. And a fixing condition correcting means for correcting a fixing condition in accordance with the degree of thermal deterioration estimated by the heat deterioration estimating means. 2. The fixing device according to claim 1, wherein the thermal deterioration estimating unit estimates that the thermal deterioration has progressed as the integrated energizing time is longer. 3. The fixing device according to claim 1, wherein the fixing condition correcting unit corrects at least a fixing speed. 4. The fixing condition correcting means for reducing the fixing speed as the integrated power-on time is longer.
3. The fixing device according to claim 1. 5. The fixing device according to claim 4, wherein the fixing condition correcting means reduces the fixing speed in a stepwise manner with respect to the integrated energizing time. 6. The fixing device according to claim 1, wherein the fixing condition correcting means corrects at least a fixing temperature. 7. The fixing condition correcting means increases the fixing temperature as the integrated energizing time is longer.
3. The fixing device according to claim 1. 8. The fixing device according to claim 7, wherein the fixing condition correcting means increases the fixing temperature in a stepwise manner with respect to the integrated energizing time. 9. A fixing device comprising: means for switching a fixing temperature to a plurality of set values; wherein the fixing condition correcting means shortens a time interval of an integrated energizing time for increasing the fixing temperature as the set fixing temperature is higher. The fixing device according to claim 8, wherein the setting is performed. 10. A fixing means for switching a fixing temperature to a plurality of set values, wherein the fixing condition correcting means sets a rise width of one fixing temperature to be larger as the set fixing temperature is higher. The fixing device according to claim 8. 11. A temperature detecting means for detecting a surface temperature of at least one of the first and second heat fixing members, wherein the fixing condition correcting means detects at least a temperature detected by the temperature detecting means. The fixing device according to claim 3, wherein at least one of a fixing speed and a fixing temperature is further corrected based on the fixing speed. 12. The first and second elastic members each having an elastic member, and the first and second elastic members are pressed against each other so that the elastic members come into contact with each other.
And a heating means for heating at least one of the first and second heat-fixing members, and a developing unit on a transfer sheet inserted through a contact portion between the first and second heat-fixing members. A fixing device that heats and melts the agent and fixes the agent on the transfer sheet, wherein at least one of the first and second heat fixing members is
An elastic means for urging the first and second heat fixing members in a direction in which they are pressed against each other; and a constant distance between the first and second heat fixing members against the pressing force of the elastic means. Holding the first and second
Means for maintaining the contact portion between the heating and fixing members at a constant width, and thermal deterioration estimating means for estimating a degree of thermal deterioration of the elastic member based on at least an integrated energizing time which is an integrated value of energizing time to the heating means. A fixing force adjusting means for adjusting the pressing force of the elastic means according to the degree of thermal deterioration estimated by the thermal deterioration estimating means. 13. The fixing device according to claim 12, wherein the fixing condition correcting unit reduces the pressing force of the elastic unit as the integrated energizing time increases.