JPH07129026A - Image forming device - Google Patents

Abstract

PURPOSE:To provide an image forming device without generating the deviation of an image and the wrinkles of a recording material due to the deformation of a pressure roller by eliminating some problems. CONSTITUTION:After printing is completed, the temp. of a fixing roller is lowered to a standby temp., and when a printing signal is not outputted for five minutes (t1) for instance, a heater is turned off and shifted to an electricity saving mode. A printer main motor for rotating the pressure roller is turned on for 1.3 seconds (t6) for instance, at the same time of shifting the heater into the electricity saving mode. Thus, the rubber layer of the pressure roller is prevented from being locally, concentratively and repeatedly affected by temperature change to prevent the deterioration of rubber.

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 laser beam printer or an electrophotographic copying machine. In particular, the present invention relates to a fixing device of an image forming apparatus having a power saving mode in which a fixing heater is turned off.

[0002]

2. Description of the Related Art Conventionally, as an image forming apparatus using a laser using an electrophotographic method, there is a laser beam printer in addition to a copying machine and a facsimile.

In this laser beam printer, when a print signal is output from a computer and document data is sent as shown in FIG. 18, the surface temperature of the fixing roller 103 in the fixing device 100 shown in FIG. Is detected by the thermistor 101, and the standby temperature (here, 18
From 0 ° C. to the print temperature (here, 190 ° C.), the heater 102 in the fixing roller 103 is turned on and raised.
Start printing.

On the other hand, when printing is completed, the temperature is lowered to the standby temperature. For example, when no print signal is output for 5 minutes (= t ₁ ), the heater is turned off to enter the power saving mode. In this power saving mode, the pressure roller does not rotate because the main motor, which is synchronized with the rotation of the pressure roller, remains off.

When a print signal is received during the power saving mode, the power saving mode is released and the fixing roller 103 is released.
The inside heater 102 is turned on to raise the temperature of the surface of the fixing roller 103 to the printing temperature, and printing is started again.

As described above, in the conventional fixing device,
By controlling the heater 102 in the fixing roller 103 at any time, power saving is achieved.

[0007]

However, according to the above-mentioned conventional example, the rubber forming the pressure roller is apt to be deteriorated by a rapid thermal change, and particularly in the device having the power saving mode, the rubber is repeatedly subjected to the temperature change. Since the frequency is high, the rubber tends to be deteriorated, and the rubber having a low hardness has a problem that the deterioration is remarkable.

As a result, the portion that is in pressure contact with the fixing roller may be deformed to cause image misalignment or wrinkling of the recording material in the direction perpendicular to the conveying direction.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and provide an image forming apparatus which does not cause image shift due to deformation of a pressure roller and wrinkling of a recording material.

[0010]

According to the present invention, the above object is to provide an image forming means for forming an unfixed developer image on a recording material and an endlessly movable body for conveying the recording material. A recording material conveying member for fixing, a heating source arranged in contact or non-contact with the recording material conveying member for fixing, and pressed against the heating source via the recording material conveying member for fixing, or the recording material described above. A pressing rotary member that directly presses and rotates with the conveying member to sandwich and convey the recording material together with the fixing recording material conveying member, and does not receive the next image forming operation start signal for a predetermined time after the image forming operation is completed. In this case, in the image forming apparatus including a temperature control device set to stop energizing the heating source and shift to the power saving mode, the pressing rotary member may be used before or after shifting to the power saving mode. Rotate, It is achieved by that it comprises a set rotation control means to vary the pressure contact position between the serial heating source or fixing a recording material conveying member.

[0011]

According to the present invention, when the image forming operation is completed,
The power supply to the heating source is stopped by the temperature control device to shift to the power saving mode.Before or after shifting to the power saving mode, the rotation control means rotates the pressurizing rotating member to rotate the heating source or the fixing recording material. The pressure contact position between the conveying member and the pressing rotary member is changed. This allows
The pressurizing rotary member is not locally concentrated and heated / cooled, and deterioration of the pressurizing rotary member is prevented.

[0012]

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

<First Embodiment> First, a first embodiment of the present invention will be described with reference to FIGS. 1 is a diagram showing a main part of a laser beam printer according to a first embodiment of the present invention,
FIG. 2 is a view showing a fixing device provided in this laser beam printer.

In FIGS. 1 and 2, 1 is a photosensitive drum (organic photoconductor, selenium, amorphous silicone, etc.) which is an image carrier, 2 is a charging roller, 3 is laser light, 4 is a developing device, and 5 is transfer. Roller, 6 cleaner, P recording material, t
a, tb, and tc are toners.

Characters and image information converted into electric signals from a host computer (not shown) are input to an interface controller (not shown) and signal processed, and the laser light 3 is appropriately emitted by this output. To do. The laser light 3 is projected onto the surface of the photosensitive drum 1 while scanning in a direction perpendicular to the rotation direction thereof. At this time, the photosensitive drum 1 is rotating in the direction a and is uniformly distributed by the charging roller 2. Is charged. Therefore, the charge on the photosensitive drum 1 is attenuated where the laser light 3 is applied, and the charge remains on the photosensitive drum 1 where the laser light 3 is not applied. An electrostatic latent image is formed. Then, this electrostatic latent image is subjected to reversal development by the developing device 4, and a visible image is obtained on the photosensitive drum 1 by the toner applied according to the electrostatic latent image. On the other hand, recording material P
Are picked up one by one by a paper feed roller (not shown), and are aligned at a position where the photosensitive drum 1 and the transfer roller 5 face each other via a paper guide (not shown) at a timing adjusted by a registration roller (not shown). The toner image transferred on the drum 1 is
It is transferred onto the recording material P by the transfer roller 5 to which a voltage having a polarity opposite to that of the toner is applied. After that, the recording material P is separated from the photosensitive drum 1 by its own weight or static elimination, the toner image is fixed by the fixing device 200, and the recording material P is discharged to a tray (not shown).

After the transfer process is completed, the photosensitive drum 1 removes the residual toner by the cleaner 6, and then enters the next image forming process.

Next, the fixing device 200 in the above laser beam printer will be described in detail with reference to FIG. The fixing roller 203 shown in FIG. 2 has a length of 364 m.
m aluminum cylinder roller with a thickness of 2.9 mm,
It is coated with 25 μm thick PFA to improve releasability, and its outer diameter is 27.8 mm. A 600 W halogen heater 202, which is a heating source, is disposed inside the fixing roller 203. Further, the surface of the fixing roller 203 is 25 μm thick on the surface of a polyimide material.
m-thick PFA-coated separating claw 206, fixing pad 2
05 and the thermistor 201 are arranged in contact with each other.

On the other hand, a pressure roller 204 is arranged below the fixing roller 203. This pressure roller 204
Is for forming a nip (pressing contact portion) in the heat fixing portion, a PFA tube having a thickness of 50 μm (volume resistance 10 ¹³ to 10 ¹⁴ Ω · cm) in the upper layer and conductivity (volume resistance 10 ³ to in the lower layer). 10 ⁴ Ω · cm) Silicone sponge, core metal with a round bar of iron with an outer diameter of 14 mm, length 317 mm (rubber part),
It has an outer diameter of 27 mm and a hardness of 41 ° (ASKER-C hardness). In the pressure roller 204, both ends of the core metal are pressed toward the center of the fixing roller 203 by springs (not shown) with a total pressure of 13 kgf of 6.5 kgf on one side, and the core metal of each roller is a bearing of a bearing. It is supported by and is driven to rotate by the print main motor. The peripheral speed is 75m
It is rotating at m / s.

Next, the operation sequence of the apparatus of this embodiment will be described with reference to the timing chart of FIG.
As shown in FIG. 3, when a print signal is output from the computer, the document data is sent to the laser beam printer, the temperature of the surface of the fixing roller 203 of the fixing device 200 is detected by the thermistor 201, and the standby temperature (1 in this case) is detected.
From 80 ° C.) to the print temperature (here, 190 ° C.), the heater 202 in the fixing roller 203 is turned on and raised to start printing. After that, when printing (here, two sheets) is completed, the fixing temperature is lowered to the standby temperature, and if no print signal is output for 5 minutes (assuming t ₁ = 5 minutes), the heater is turned off and the power saving mode is entered. .

Then, the printer main motor for rotating the pressure roller at the same time when the power saving mode is entered is set for 1.3 seconds (=
t ₆₎ is turned on. At this time, the movement distance is 117 mm (this value is an actual measurement value, and is larger than the value calculated assuming that the main motor is turned on for 1.3 seconds because of the inertia of the motor), and the movement angle is 496.6 ° (360 × 11
7/27 × π).

Further, when the power saving mode continues for t ₂ or more, the pressure roller is rotated during t ₇ , and similarly t ₈ and t.
Rotate the pressure roller for a period of ₉ .

The values of t ₅ , t ₂ , t ₃ , and t ₄ may be arbitrarily determined, and the values of t ₆ , t ₇ , t ₈ , and t ₉ are also arbitrary so that the nip position does not come to the same place. You may change to.

After that, when a print signal is received during the power saving mode, the power saving mode is released, and the temperature of the fixing roller surface of the fixing device is raised to the print temperature by turning on the heater in the fixing roller to print. Start.

As described above, according to this embodiment, by providing the pressure roller deformation preventing mode for rotating the pressure roller during the power saving mode, the rubber layer of the pressure roller repeats a local temperature change. It is possible to prevent the rubber from being received and prevent the rubber from being deteriorated.

As shown in FIG. 4, 4 minutes (= t ₁₀ ) after the end of printing, the pressure roller deformation prevention mode is entered, and the printer main motor is operated to turn off the pressure roller before the fixing heater is turned off. You may make it move the nip part of. .

Further, as shown in FIG. 5, when the printer main motor is moved, the fixing heater may be turned on for a short time to enter the pressure roller deformation prevention mode. In particular with those of the sliding type resin to the fixing bearing, t ₆ ~
When the value of t ₉ is set to several seconds or more, it is preferable to adjust the temperature of the fixing roller pair to a predetermined constant temperature and then rotate the main motor for a predetermined time in consideration of the sliding characteristics depending on the temperature of the bearing. By doing so, the friction between the bearing of the fixing roller and the core of the fixing roller is reduced, and the torque for rotating the fixing roller can be effectively reduced. Particularly, the effect is great when the bearing of the fixing roller is made of resin.

<Second Embodiment> Next, a second embodiment of the present invention will be described with reference to FIGS. 6 and 7. The same parts as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

In this embodiment, unlike the first embodiment, the surface temperature of the fixing roller is detected by the thermistor 201 as shown in FIG.
From the power saving mode on to the fixing roller surface temperature T ₁ , the printer main motor is driven as in the first embodiment to enter the pressure roller deformation prevention mode in which the pressure roller is rotated.

When the surface temperature of the fixing roller is less than T ₁ ,
Do not drive the printer main motor. Accordingly, when the bearing of the fixing roller is made of resin, it is possible to prevent the core metal of the fixing roller from being bitten by the bearing. The flowchart is as shown in FIG.

<Third Embodiment> Next, a third embodiment of the present invention will be described with reference to FIGS. The same parts as those of the first and second embodiments are designated by the same reference numerals and the description thereof will be omitted.

This embodiment is different from the second embodiment in that the surface temperature of the pressure roller is controlled by the thermistor 2 as shown in FIGS.
In step 07, the printer main motor is driven to enter the pressure roller deformation prevention mode in which the pressure roller is rotated until the pressure roller surface temperature reaches T2 after the power saving mode is turned on.

When the surface temperature of the pressure roller is less than T ₂ ,
Do not drive the printer main motor. The flowchart is as shown in FIG.

Since the temperature of the pressure roller is made of a rubber material, it has a large heat capacity and the surface temperature after printing is largely different depending on the number of prints, and the effect of adopting this embodiment is great.

<Fourth Embodiment> Next, a fourth embodiment of the present invention will be described with reference to FIGS. The same parts as those of the first to third embodiments are designated by the same reference numerals and the description thereof will be omitted.

In this embodiment, as shown in FIG. 11, the film 302 is brought into contact with and slid on the heating body 301, and the film 3
No. 02 heating element 301 is adhered to the surface opposite to the heating element 301, and a material to be heated (recording material) P is adhered to the heating element 301 together with the film 302.
And applies heat energy to the material P to be heated from the heating body 301 via the film 302. The pressure roller 303 driven by the motor M is used as a member for pressing and transporting the material P to be heated to the film 302. I have it. Also,
It has a thermistor 304 as a temperature detecting element in contact with the pressure roller 303.

FIG. 12 shows the sequence of this embodiment.
Similar to the third embodiment, the surface temperature of the pressure roller 303 is detected by the thermistor 304 which is in contact with the pressure roller 303, and the temperature is compared with the determined temperature to set the pressure roller deformation prevention mode. Decide whether to enter.

In this embodiment, the main motor and the pressure roller drive motor are different from each other, and the noise when rotating is reduced.

<Fifth Embodiment> Next, a fifth embodiment of the present invention will be described with reference to FIGS. The same parts as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

In this embodiment, after entering the power saving mode,
Although the timing is the same as that of the first embodiment, the rotation speed of the main motor can be reduced to half that during printing to reduce noise.

Further, as shown in FIG. 14, during the standby mode and the power saving mode, the rotation speed of the main motor may be reduced to 1/10 of that during printing and the rotation may be continued. As a result, noise can be reduced and deformation of the pressure roller can be prevented.

<Sixth Embodiment> Next, a sixth embodiment of the present invention will be described with reference to FIGS. The same parts as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

FIG. 15 is a vertical sectional view of the fixing device according to the sixth embodiment. This embodiment differs from the first embodiment in that the pressure plate 208
A solenoid 209 is provided in the power source, and when the power saving mode is turned on, the pressure can be weakened by turning on the solenoid and moving the pressure plate.

FIG. 16 shows the sequence. By doing so, the deformation of the pressure roller can be prevented.

[0044]

As described above, according to the present invention,
Even in an image forming apparatus in which the pressure-applying rotary member is formed of rubber and provided with a power saving mode, the pressure-applying rotary member is locally moved by changing the pressure contact position between the heat source or the fixing recording material conveying member and the pressurizing rotary member. It is possible to prevent image deviation due to deformation of the pressing rotary member, or generation of wrinkles of the recording material in the direction perpendicular to the recording material conveyance direction without being repeatedly subjected to repeated temperature changes.

[Brief description of drawings]

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

FIG. 2 is a detailed vertical sectional view of a fixing device used in the apparatus of FIG.

FIG. 3 is an operation sequence diagram of the apparatus in FIG.

FIG. 4 is another operation sequence diagram according to the first embodiment of the present invention.

FIG. 5 is another operation sequence diagram according to the first embodiment of the present invention.

FIG. 6 is a diagram showing a relationship between an operation sequence and a fixing roller surface temperature in Embodiment 2 of the present invention.

FIG. 7 is a flowchart after shifting to a power saving mode according to the second embodiment of the present invention.

FIG. 8 is a diagram showing a relationship between an operation sequence and a fixing roller surface temperature in Embodiment 3 of the present invention.

FIG. 9 is a flowchart after shifting to a power saving mode according to the third embodiment of the present invention.

FIG. 10 is a detailed vertical sectional view of a fixing device according to a third embodiment of the invention.

FIG. 11 is a detailed vertical sectional view of a fixing device according to a fourth exemplary embodiment of the present invention.

FIG. 12 is an operation sequence diagram in the fourth embodiment of the present invention.

FIG. 13 is an operation sequence diagram in the fifth embodiment of the present invention.

FIG. 14 is another operation sequence diagram according to the fifth embodiment of the present invention.

FIG. 15 is a detailed vertical sectional view of a fixing device according to a sixth embodiment of the present invention.

FIG. 16 is an operation sequence diagram in the sixth embodiment of the present invention.

FIG. 17 is a detailed vertical sectional view showing a schematic configuration of a conventional image forming apparatus.

FIG. 18 is an operation sequence diagram of a conventional image forming apparatus.

[Explanation of symbols]

102, 202 Halogen heater (heating source) 103, 203 Fixing roller (fixing recording material conveying member) 104, 204, 303 Pressure roller (pressing rotating member) 301 Heating body (heating source) 302 Film (fixing recording material) Conveying member) P Recording material

Claims (7)

[Claims] 1. An image forming unit for forming an unfixed developer image on a recording material, an endlessly movable fixing recording material conveying member for conveying the recording material, and the fixing recording material conveying. A heating source arranged in contact or non-contact with the member,
Pressure contact with the heating source via the fixing recording material conveying member,
Alternatively, a rotation member for pressing the recording material conveying member directly in rotation to rotate to sandwich and convey the recording material together with the fixing recording material conveying member, and a next image forming operation start signal after the image forming operation is completed. In the case of not receiving the signal for a predetermined time, in an image forming apparatus provided with a temperature control device set to stop energizing the heating source and shift to the power saving mode, before or after shifting to the power saving mode. An image forming apparatus comprising: a rotation control unit that is set to rotate a pressure rotating member to change a pressure contact position with the heating source or the fixing recording material conveying member. 2. The rotation control means detects the temperature of the fixing recording material conveying member or the heating source before or after shifting to the power saving mode, and determines the time and the number of rotations of the pressing rotating member according to the temperature. The image forming apparatus according to claim 1, wherein the image forming apparatus is set so as to rotate and change the press contact position. 3. The rotation control means detects the temperature of the surface of the pressing rotary member before or after shifting to the power saving mode,
The image forming apparatus according to claim 1, wherein the pressing rotation member is set so as to change the pressing position by determining the time and the number of rotations of the pressing rotation member and rotating the pressing rotation member. 4. The rotation control means, after the image forming operation is completed,
The image forming apparatus according to any one of claims 1 to 3, wherein the pressing rotation member is set to shift to a power saving mode while rotating at a rotation speed lower than that during the image forming operation. 5. The image forming apparatus according to claim 1, further comprising means for weakening a pressure contact force of the pressure rotating member in the power saving mode. 6. The image forming apparatus according to claim 1, wherein the fixing recording material conveying member is a fixing roller having an elastic layer on a cored bar. 7. The image forming apparatus according to claim 1, wherein the fixing recording material conveying member is a pressure rotating member and a heat resistant film member.