JPH0766221B2 - Thermal fuser cleaning method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a heat fixing device cleaning method for cleaning a heat roller and a backup roller in a heat roller type heat fixing device of a recording device using a dry developer, particularly an electrophotographic recording device. Regarding

2. Description of the Related Art As shown in FIG. 9, a conventional heat roller type heat fixing device rotatably drives a heat roller 1 having a halogen lamp (not shown) therein and the heat roller 1 in a direction indicated by an arrow. A drive device (not shown) and the heat roller 1 so that the recording paper can be pressed against the heat roller 1.
Rotatable backup roller 2 pressed against
And a cleaning device 3 for removing dirt on the heat roller 1 and the like, and the unfixed toner 4 adheres to the surface between the heat roller 1 and the backup roller 2 obtained through the image forming process. By passing the recording paper 5 passing through the path indicated by the arrow A, the toner is melted by heat and then fixed to the recording paper to fix the toner. In the figure, 6a and 6b are separation claws, and 7a and 7b are discharge rollers.

More specifically, in the heat roller 1, the surface of a hollow metal roller is usually coated with Teflon (PFA, PTFE, etc.) to prevent toner from offsetting to the surface of the heat roller. However, in actuality, toner offset may occur depending on conditions such as toner constituent material and fixing temperature. Therefore, a cleaning device 3 for removing the toner adhering to the heat roller 1 is provided in order to prevent the offset toner from contaminating the subsequent image. The cleaning device 3 is roughly classified into an oil coating type and an oilless type. The oil coating type is a type in which silicon oil is constantly supplied and impregnated into the felt, and the felt is brought into contact with a heat roller for coating. Many. on the other hand,
As the oilless type, felt, blade, or web is used.

Silicon rubber is also used for the backup roller to prevent toner offset.

SUMMARY OF THE INVENTION However, as described above, the conventional heat fixing device has to be provided with a cleaning device for removing dirt on the heat roller, which makes the device complicated, especially in the oil application type. However, the oilless type has a problem that the replacement cycle is short.

On the other hand, since the backup roller is rarely provided with its own cleaning device, it is difficult to eliminate the stain once it is attached.

The above problem occurs for the following reasons. That is, in the oil application type fixing device, a mechanism for uniformly applying the silicon oil on the heat roller and collecting the excess oil is necessary, and the mechanism is inevitably complicated. On the other hand, the oilless type, especially the type that uses a felt or a blade, is mechanically simple, but it has a small capacity for accumulating the offset toner and has a short life of itself, so that the replacement cycle is short. Usually, it is a factor that determines the shortest maintenance cycle of the fixing device. Therefore, a web or roller felt may be used in order to prolong the life of the cleaning device (see, for example, JP-A-62-47674 and JP-A-62-2284). However, even in this case, for example, in the case of a web, a complicated mechanism including a take-up motor is required, and the life of the roller felt is only about 2 to 3 times as long as that of an ordinary plate-shaped one in view of space. The problem of not becoming remains.
In other words, basically the method of storing dirt always leads to the end of its life.

Further, since the surface of the backup roller is usually made of silicone rubber, cleaning by mechanical rubbing similar to that of the heat roller causes a large amount of friction and is practically impossible.

The present invention has been made in view of the above problems, and provides a heat fixing device cleaning method capable of cleaning a heat roller and a backup roller of a heat fixing device without providing a cleaning device. With the goal.

Means for Solving the Problems The inventors of the present invention have diligently studied to solve the above-mentioned problems, and the heat roller and the backup roller do not always have to be cleaned at all times, only by cleaning at an appropriate interval. Offset to the recording paper can be prevented, dirt on the surface of the heat roller can be removed by rubbing with the recording paper, and the surface temperature condition of the heat roller and the backup roller is set to a certain temperature range,
The present invention has been accomplished by finding that stains on the backup roller are transferred to the heat roller by rotating the two in contact with each other.

That is, the first invention of the present application does not use a cleaning device that is normally used, but supplies a recording sheet between the heat roller and the backup roller of the heat fixing device during the non-recording operation. And a backup roller sandwiching the recording paper, a speed difference is generated between the running speed of the recording paper and the peripheral speed of the heat roller, and the dirt of the heat roller is removed by the recording paper. Is.

Further, in the second invention of the present application, the heat roller and the backup roller of the heat fixing device are rotated in contact with each other during non-recording operation, and the heat roller surface temperature and the backup roller surface temperature are heated during the rotation. In the temperature range in which the adhesive force between the roller surface and the toner is larger than the adhesive force between the backup roller and the toner, dirt on the backup roller is transferred to the heat roller.

Furthermore, the third invention of the present application is a combination of the first invention and the second invention. That is, at the time of non-recording operation, the heat roller and the backup roller of the thermal fixing device are brought into contact with each other and rotated, and during the rotation, the heat roller surface temperature and the backup roller surface temperature are kept between the heat roller surface and the toner. The adhesive force of the backup roller is larger than the adhesive force between the backup roller and the toner, the dirt of the backup roller is transferred to the heat roller, and then the recording paper is supplied between the heat roller and the backup roller. Then, with the heat roller and the backup roller sandwiching the recording paper, a speed difference is generated between the traveling speed of the recording paper and the peripheral speed of the heat roller, and the dirt of the heat roller is removed by the recording paper. This is the structure.

Effect In the first invention of the present application, as described above, the recording paper is sandwiched between the heat roller and the backup roller of the heat fixing device, and a speed difference is generated between the recording paper and the heat roller. The heat roller can be cleaned by scraping off the dirt such as the offset toner on the recording paper. The dirty recording paper may be discharged and discarded.

Next, in the second invention of the present application, the surface temperature of each of the heat roller and the backup roller is set so that the adhesive force to the toner becomes larger on the heat roller side, so that the heat roller and the backup roller mutually At the contacted portion, dirt such as offset toner is transferred to the heat roller side. Therefore, by rotating the heat roller and the backup roller in contact with each other, the dirt on the entire surface of the backup roller is transferred to the heat roller side, and the backup roller can be cleaned.

Furthermore, in the third invention of the present application, by combining the above methods, first, the dirt of the backup roller is transferred to the heat roller to clean the backup roller, and then the dirt of the heat roller is rubbed against the recording paper to remove the heat roller. Both rollers of the heat fixing device can be cleaned by cleaning.

As described above, unlike the conventional method, the method of the present invention does not require a cleaning device, can simplify the structure, and is not a method of depositing dirt on the cleaning member. Therefore, replacement of the cleaning member itself is unnecessary. ,
It becomes possible to prolong the maintenance cycle and prolong the life of the fixing device.

EXAMPLE FIG. 1 shows a schematic structure of an electrophotographic recording apparatus used for carrying out the method of the present invention, in which 20 is a photosensitive drum and 21a.
Is a recording paper roll, 21b is a recording paper fed from the recording paper roll 21a, 22 is a feeding roller, 22a is a driving roller, 22b is a driven roller, 23 is a pulley, 24 is a cutter, 25 is a cutter, 25 is a feeding roller, and 25a is a driving roller. Roller, 25b is a driven roller, 26 is a pulley,
27 is a drive roller 22 for each of the paper feed roller 22 and the feeding roller 25.
a, a pulse motor for driving 25a, 28: a transfer for peeling toner from the photosensitive drum 20 and peeling the recording paper, a peeling portion, 29: a heat fixing device, 29a: a heat roller having a Teflon coating layer on its surface, and 29b: a surface Rotatable backup roller with silicone rubber, 30 is pulley, 31 is heat roller 29
Reference numeral 32 is a motor for driving a, and numeral 32 is a paper discharge sensor for detecting that the recording paper has passed through the thermal fixing device 29. It should be noted that the image forming process unit (initial charging device, exposing device, developing device, cleaning device, etc.) around the photosensitive drum 20 is omitted in this figure.

The recording operation and the method for cleaning the heat fixing device 29 in the electrophotographic recording apparatus configured as described above will be described below.

First, at the time of recording, this operation is exactly the same as that at the time of recording in a normal electrophotographic recording apparatus. That is, first, a photosensitive drum on which a latent image has been formed and which has adhered toner through the developing section.
20 rotates in the direction of the arrow and reaches the transfer and peeling section 28. On the other hand, in synchronization with this, the recording paper 21b is transferred to the peeling section 28 by the paper feed roller 22 and the feeding roller 25, and the toner is transferred and the recording paper is peeled off. And the recording paper 21
b further reaches the heat fixing device 29, and the toner is fixed on the recording paper 21b by the heat of the heat roller 29a having a halogen lamp inside. On the other hand, the recording paper 21b is cut by the cutter 24 when it advances by a predetermined amount. Further, at the time of this recording, the conveyance speed of the recording paper 21b and the peripheral speed of the fixing roller are set to be substantially the same.

Here, as shown in the figure, the thermal fixing device 29 is not provided with a cleaning device. As described above, the conventional fixing device is provided with the cleaning device for removing the dirt on the heat roller. This is because the toner may be offset to the heat roller side at the time of fixing and stain the subsequent images.
This is to prevent it.

However, as a result of experiments conducted by the present inventors, if the heat roller surface temperature is set to an appropriate temperature for the toner that is used as a product, the heat roller surface can be cleaned without cleaning. Not only the offset that looks like, but the offset that stains the image is
We have confirmed that this does not occur with at least 1,000 print orders. Therefore, in the short term, there is no particular problem even if the cleaning device is not used. However, in the long term, it is a fact that stains gradually accumulate, become visible, and stain the front and back surfaces of the recording paper. Further, when a recording paper jam occurs, particularly when a fixing unit jams, the improperly fixed toner on the recording paper may adhere to the heat roller. Therefore, it is necessary to reliably perform cleaning each time.

Therefore, a cleaning method of the present invention that does not use a cleaning device will be described.

First, a method of cleaning the heat roller 29a will be described. As shown in FIG. 1, in this apparatus, separate motors 27 and 31 drive the paper feed roller 22 that conveys the recording paper 21b and the feeding roller 25, and the heat roller 29a of the heat fixing device 29. There is. Therefore, the recording paper 21 by the feeding roller 25 is
The conveyance speed of b and the peripheral speed of the heat roller 29a can be controlled independently of each other. Therefore, during the non-recording operation, first, the motors 27 and 31 are operated to convey the recording paper 21b to the thermal fixing device 29 without performing recording, and the recording paper 21b is placed between the heat roller 29a and the backup roller 29b. After being securely sandwiched (the state is detected by, for example, the paper discharge sensor 32), the motor 27 for driving the feeding roller 25 is stopped in the excited state, and the heat roller 29a is continuously rotated. Then, the recording paper 21b does not run because it is pressed by the paper feed roller 22 and the feeding roller 25, and the thermal fixing device 29
Then, the heat roller 29a runs idle while rubbing the recording paper 21b. Therefore, due to the rubbing, stains mainly on the toner attached to the heat roller 29a are transferred to the recording paper 21b, and the outer surface of the heat roller 29a is cleaned. When the heat roller 29a makes almost one rotation, the motor 27 is slightly actuated to advance the recording paper 21b slightly, and then the recording paper is stopped again, and the heat roller 29a is rubbed with a new portion of the recording paper to clean it. After repeating this operation an appropriate number of times, the recording paper 21b is cut by the cutter 24, and the dirty recording paper 21b is discharged and discarded. This completes one cleaning operation. This cleaning operation is automatically performed by a sequence control device (not shown). The start timing of the cleaning operation will be described later. According to the experiment conducted by the present inventor, the stains when printing about 5000 passages could be completely removed by three rotations by slightly advancing the recording paper 21a every one rotation of the heat roller 29b.

In the case of this method, it is true that it is good to carry out the heating with the heat roller 29a, but since the cleaning is carried out by the mechanical force of rubbing, it can also be carried out at room temperature. However, since the damage to the heat roller 29a increases, it is basically desirable to perform it in a heated state.

Further, if the speed difference between the heat roller 29a and the recording paper 21b occurs, rubbing occurs, so it is not particularly necessary to stop the running of the recording paper 21b with certainty.
It is not necessary to increase the nip pressure of the feeding roller 25. However, if the conveyance force of the fixing device 29 is extremely large due to that of the paper feed roller 22 and the feeding roller 25,
On the contrary, the recording paper 21b is pulled out by sliding on the paper feeding roller 22 and the feeding roller 25, and the paper feeding roller 22 and the feeding roller 25 are rubbed by the recording paper. Therefore, this state is always generated during cleaning, and the rubber wear of those rollers increases. In such a case, the recording paper roll 21
There is a method to fix a so that it does not rotate. Figure 2 shows
The main portion of an example of a recording paper running stopper for preventing the recording paper roll 21a from rotating is shown. 21a is a recording paper roll, 33 is a recording paper spool, 33a is a protruding portion of the spool, and 34 is the apparatus main body side. A solenoid fixed to (not shown), 34a, is a plunger that moves therein. It's very easy to operate, and normally the plunger 34a is a solenoid 3
If you want to stop the recording paper running while it is retracted inside 4, slide it toward the spool 33 side. Then, the tip of the protrusion 33a is caught, the rotation of the spool 33 and the recording paper roll 21a held by the protrusion 33a is prevented, and the running of the recording paper is stopped. When such a stopper is used, it is not necessary to stop the pulse motor 27 in FIG. 1 in the excited state, and both the paper feed roller 22 and the feeding roller 25 may be in a free state. Further, the motor 27 is not limited to the pulse motor, and may be a DC motor, for example.

Further, in this embodiment, two motors are used, but there is also a method in which the motor itself is one and a clutch for disconnecting the recording paper conveyance system is provided. An example thereof is shown in FIG. Third
In the figure, the same as in the case of FIG. 1 except that 35 is a motor, 36 is a clutch for controlling the rotation of the recording paper conveyance system roller, and 37 is a recording paper running stopper for stopping the rotation of the recording paper roll 21a. It is a composition. Here the recording paper running stopper
As the device 37, for example, the device described above (FIG. 2) is used. Next, the operation will be described. Clutch during normal recording
Since 36 is connected and the driving force of the motor 35 is transmitted, the paper feeding roller 22, the feeding roller 25, and the heat roller 29a rotate. On the other hand, at the time of cleaning, at least until the leading edge of the recording paper 21b passes between the rollers of the thermal fixing device 29, it is the same as at the time of normal recording, but immediately after that, the clutch 36
Is separated, and at the same time, the recording paper running stopper 37 is activated. Therefore, in this case as well, the heat roller 29a in the thermal fixing device 29 runs idle while rubbing the stationary recording paper 21b, so that the surface thereof is cleaned.

The operation of the heat roller cleaning method according to the present invention has been described above. Next, the timing (timing) of the cleaning will be described. First, as a general rule, this cleaning must be performed during non-recording. Further, as described above, when using a normal toner,
It was found from an experiment that the offset to the heat roller, which stains the image, does not occur in about 1,000 prints. Therefore, as shown in the present embodiment, when roll paper is used as the recording paper, it is desirable to adopt a method of automatically performing cleaning when the roll paper is set in the apparatus.
One reason is that in the case of roll paper, one roll of recording paper length is fixed, and it is usually exchanged with about 300 copies, and even with a large number, about 500 copies will be exchanged reliably, and therefore the recorded image will be smeared. This is because regular cleaning is automatically performed without accumulation of dirt. Another advantage is that in the case of a device that uses roll paper, the length of the recording paper is usually set to a specified length for the purpose of aligning the leading edge of the recording paper and cutting off the chevron-shaped cut of the leading edge when setting in the device. In many cases, it is configured to automatically feed out and cut, and automatically discharge the paper. At this time, the above-described cleaning is automatically performed, so that the loss of the recording paper can be substantially eliminated. Therefore, even from this point of view, the present invention is very suitable for an apparatus using roll paper. On the other hand, the effect of the present invention does not change even in an apparatus using a cut sheet, but unlike the case of a roll sheet, the number of recording sheets at the time of replenishment is indefinite, so the number of recording sheets is managed by a counter or the like of the recording apparatus, A method of automatically performing cleaning after every predetermined number of sheets is preferable. However, in this case, when the counter reaches a predetermined number and the cleaning is automatically performed during continuous recording, the dirty recording paper used for cleaning enters between the regular recorded objects. Occurs. Therefore, in order to prevent such a thing from occurring, for example, when the cleaning time (number of passes) is reached during continuous recording, the apparatus side is provided with a control circuit that waits until a series of recording is completed and then performs cleaning. It is preferable. The control circuit may be provided with a function of, for example, determining that the recording is completed and starting cleaning when the next recording is not performed even after a predetermined time elapses after the recording is completed. .

The regular cleaning of the heat roller when using roll paper or cut paper has been described above. In addition to such regular cleaning, it is necessary to perform cleaning one after another when trouble occurs, especially when recording paper is jammed in the fixing section. Therefore, it is preferable that the same operation as the regular cleaning is automatically performed when a jam occurs.

Next, the backup roller 29b (see FIGS. 1 and 3)
The cleaning method will be described. Since the backup roller 29b normally contacts the back surface of the recording paper, it is hardly soiled by the toner adhering to the recording paper.
However, when the recording paper is not present, it is in contact with the heat roller 29a and is rotating, and when the heat roller 29a is heated to the fixing temperature, the toner is attached to the backup roller rather than the adhesive force to the heat roller. Since the adhesive force is large, the offset toner adhering to the heat roller is transferred to the backup roller side, and the backup roller becomes dirty. In particular, as described above, when a large amount of toner adheres to the heat roller due to the occurrence of a jam in the fixing unit, a large amount of toner adheres to the backup roller, which requires cleaning.

The backup roller 29b is generally made of silicon rubber and is often a driven roll. Therefore, it is difficult to use the same method as the above heat roller cleaning. Therefore, in the present invention, a method of utilizing a change in adhesion of toner to a heat roller or a backup roller depending on temperature is used. As described above, when the heat roller is set to the fixing temperature (for example, 160 to 170 ° C.), when the heat roller 29a and the backup roller 29b are brought into contact with each other, the toner is transferred from the heat roller side to the backup roller side. However, it has been found that when the heat roller temperature is lowered and the heat roller and the backup roller are brought into rolling contact with each other while keeping the temperature in a certain temperature range, the dirt attached to the backup roller is transferred to the heat roller side.
When the present inventor examined the temperature region where the toner transfer from the backup roller to the heat roller occurred, the following results were obtained.

Conditions Heat roller surface: PFA coating Backup roller surface: Silicon rubber (RTV) Peripheral speed: 70mm (sec) Toner binder resin: Styrene-acrylic system result (temperature range where toner transfer from backup roller to heat roller occurs) Heat roller surface Temperature T _H = 100 to 130 ° C. Backup roller surface temperature T _B = T _H ± 5 ° C. In the method of the present invention, this phenomenon is utilized to clean the backup roller 29b. That is, at the time of non-recording operation, the heat roller 29a and the backup roller 29b are in rolling contact with each other, and the heat roller 29a is cooled from the fixing temperature to the above temperature region by natural heat dissipation or the temperature is raised from the normal temperature state to the above temperature region. Let As a result, the surface temperature of the backup roller 29b also falls within the above temperature range, toner stains attached to the backup roller 29b are offset to the heat roller side, and the backup roller 29b is cleaned. The temperature range in which the toner transfer from the backup roller to the heat roller occurs is
Since it changes depending on the toner characteristics, roller surface characteristics, etc., it is sufficient to select an appropriate temperature range according to the toner characteristics, roller surface characteristics, etc.

After the cleaning operation of the backup roller 29b is completed, the heat roller cleaning method described above can be performed to remove dirt on the heat roller. Therefore, the backup roller 29b and the heat roller 29a can be cleaned without using a cleaning device.

The reason why the phenomenon of toner transfer from the backup roller 29b to the heat roller 29a occurs is not always clear, but it is considered as follows. Firstly, the toner in this case can be regarded as a kind of hot melt type toner, and the adhesion to the adherend (in this case, the heat roller or backup roller) changes with temperature, and secondly, the heat roller. And the backup roller have different surface states (surface roughness, surface energy, etc.).

Here, let us consider the constituent factors of the total adhesive force of the toner and the heat roller or backup roller as F _H and F _B , respectively. This is shown below.

F _H = F _T + F _TH F _B = F _T + F _TB where F _H : Total adhesion of toner to heat roller F _B : Total adhesion of toner to backup roller F _T : Toner adhesion at temperature T Cohesion force F _TH : Adsorption force of toner to heat roller at temperature T F _TB : Adsorption force of toner to backup roller at temperature T Therefore, the toner cohesion force and the adsorption force to heat roller and backup roller are divided into respective forces. Consider the dependence of on temperature.

Toner cohesive force F _T Thermoplastic resin is used as the binder of heat fixing toner. Therefore, FIG. 4 shows the temperature characteristic of the cohesive force of the toner as a model. Here, the horizontal axis represents the temperature T and the vertical axis represents the toner cohesive force F _T. Since the initial state of the toner is powder, the cohesive force between the toner particles is small. Then, as the temperature rises, it melts and the cohesive force increases (PH _{1 in the} figure).
Then, when it reaches a predetermined temperature, it reaches a peak, and thereafter, the cohesive force decreases. When the toner is cooled from this state, the cohesive force increases (PH _{2 in the} figure). Therefore, when the once-melted toner is heated and cooled, the cohesive force changes along a locus such as PH _{2 in} the figure. From the viewpoint of the cohesive force of the adhesion force of the toner to the adherend, the toner in the molten state is in contact with the two adherends (the surface material and the state are the same). When cooled, the lower the temperature, the greater the toner adhesion. Therefore, we will apply this idea to the case of backup rollers and heat rollers.

First, structurally, the heat roller is generally made of a hollow metal tube, whereas the backup roller has a siligo rubber layer formed around a metal shaft. Therefore, comparing the heat capacities, the backup roller is usually larger than the other. As a result, when the time characteristics of the surface temperature of both rollers are modeled, the relationship shown in FIG. 5 is obtained. In FIG. 5, the horizontal axis represents the elapsed time t and the vertical axis represents the surface temperature T of the roller. Here, as a view of the horizontal axis, it is assumed that the time t advances to the right in the drawing when the roller is heated and goes to the left in the drawing when the roller is cooled. Further, on the vertical axis, 0 at the origin represents normal temperature (room temperature). The symbols in the figure are as follows.

T _H: heat roller surface temperature T _H1: the heat roller surface temperature at the time of heating T _H2: during cooling of the heat roller surface temperature T _B: backup roller surface temperature T _B1: backup roller surface temperature at the time of heating T _B2: on cooling Backup roller surface temperature T _HF : Heat roller surface temperature at set fixing temperature _THB : Backup roller surface temperature at set fixing temperature Here, heating means turning on the halogen lamp inside the heat roller, and cooling means turning it off. And refers to the state of natural heat dissipation.

As can be seen from the figure, the relationship of T _H > T _B (1) always holds during heating and at the fixing temperature. This is because the heat roller has a halogen lamp that is a heating element inside,
It is natural to consider that the backup roller is only indirectly heated by rolling contact with the heat roller and has a large heat capacity.

On the other hand, when the halogen lamp is turned off and both rollers cool, this time the temperature drop of the backup roller is delayed by the amount of large heat capacity, and T _H <T _B ...... ( 2) There may be a relationship. Therefore, in this case, as a matter of course, even if the surface temperatures of both rollers are close to each other according to the relationship of the formula (1), the rollers usually adhere to the backup roller depending on the balance of forces due to factors other than the cohesive force. It was found that the toner may be sufficiently moved (offset) to the heat roller.

Next, let us consider the attractive force.

Adsorption Forces F _TH , F _TB The toner transfer from the backup roller to the heat roller is, according to the experiments conducted by the present inventor, generated only when the toner has a certain viscosity in the temperature range lower than the set fixing temperature. It was Therefore, considering this,
The attraction force of the toner to both rollers may be represented mainly by the adhesive force and Van der Waals force at the interface between the toner and the adherend. Therefore, the temperature dependence of the adhesive force and van der Waals force of the thermoplastic resin used as the binder of the toner is considered and expressed as a model. Figure 6 is a representation of the temperature dependence of the toner adhesion, the horizontal axis represents temperature T, and the vertical axis represents the toner adhesion F _c. Fig. 7 shows the temperature dependence when the van der Waals force at the interface between the toner and the adherend is considered at the molecular level in the model. The horizontal axis is temperature and the vertical axis is the magnitude of van der Waals force. ing. From these graphs, the adhesive strength increases when the toner is heated from room temperature to increase its temperature, reaches a peak at a predetermined temperature, and thereafter decreases in reverse. On the other hand, the van der Waals force becomes active in molecular motion due to temperature rise, and the force itself decreases. However, this is a case where the toner is sufficiently melted and then cooled and fixed and then heated again as a prerequisite. Also, this is a model diagram,
It is needless to say that the absolute value of the force largely changes depending on the surface shape (roughness etc.) of the adherend and the magnitude of the surface energy of the material forming the surface, rather than the absolute value of the force.

Therefore, further considering the following items, the adhesive force to each roller is considered by adding the adhesive force and the Van der Waals force.

Heat roller surface layer material: Fluorine resin (PTE, PFA, etc.) Backup roller 〃: Silicon rubber Surface energy: Silicon rubber> Fluorine resin Surface roughness: Silicone rubber> Fluorine resin Due to this, if the viscosity of the toner is low, for example, set In the vicinity of the fixing temperature (for example, 160 to 170 ° C), due to the difference in the "wettability" of the surface constituent materials, the toner has a larger adsorption force with the backup roller and the toner has a higher viscosity (for example, 110 to 140 ° C). In (), it is fully conceivable that the attraction force with the heat roller becomes larger due to the difference in van der Waals force due to the difference in surface smoothness. This situation is shown in FIG. The horizontal axis shows the temperature T, and the vertical axis shows the attraction forces F _TH and F _TB to each roller. The temperature is T _a
In the region between T _b and T _b , the attraction force is F _TH > F _TB . The setting the fixing temperature in the graph is set than normal T _b to the high temperature side.

As described above, it can be explained that the toner adhering to the backup roller can be moved to the heat roller side in a specific temperature region by the combination of the cohesive force of the toner and the adsorbing force to both rollers.

As described above, the cause of the toner movement between the rollers was considered based on the experimental results of the present inventor. This means that if a thermoplastic resin is used as the binder of the toner, it basically has this property.

The backup roller cleaning method as described above is most effective especially in terms of prolonging the maintenance cycle when used in combination with the heat roller cleaning method by rubbing the recording paper. However, it is not something that can be supplemented by it, and it can be used in combination with a cleaning method (of a heat roller) that uses an ordinary felt, blade, etc. It is very effective.

Finally, the relationship between the life of the heat roller and the backup roller of the thermal fixing device cleaning method according to the present invention will be described. First, the heat roller cleaning using rubbing with recording paper is as follows. That is, the nip pressure between both rollers and the cleaning interval (number of recordings)
Depending on the conditions such as the above, it is sure that the life is extended remarkably as compared with the conventional felt cleaning or blade cleaning which is always in pressure contact.

On the other hand, in the backup roller cleaning, no mechanical force is particularly used, and since the operation is performed in a region where the temperature is lower than the fixing temperature and the toner is not solidified, the life of the backup roller is not affected at all. .

EFFECTS OF THE INVENTION As is apparent from the above description, in the first invention of the present application, the recording paper is supplied between the heat roller and the backup roller of the heat fixing device during the non-recording operation, and the heat roller and the backup roller are connected to each other. With the recording paper sandwiched between, the speed difference between the running speed of the recording paper and the peripheral speed of the heat roller can be used to scrape off the dirt of the heat roller onto the recording paper. The heat roller can be cleaned without using such a cleaning device. For this reason, since the cleaning device is not required, the device configuration can be simplified, and since no replacement of parts of the cleaning device is required, it is possible to prolong the maintenance cycle and the life of the thermal fixing device. Has the effect.

Further, in the second invention of the present application, the heat roller and the backup roller of the heat fixing device are rotated in contact with each other during non-recording operation, and the heat roller surface temperature and the backup roller surface temperature are heated during the rotation. Cleaning the backup roller by transferring dirt on the backup roller to the heat roller by setting the temperature range in which the adhesive force between the roller surface and the toner is larger than the adhesive force between the backup roller and the toner. It has the effect that

Further, in the third invention of the present application, by combining the backup roller cleaning method of the second invention and the heat roller cleaning method of the first invention, dirt of the backup roller is first transferred to the heat roller, and then, The dirt on the heat roller can be rubbed against the recording paper to remove it, and both the backup roller and the heat roller can be cleaned without using a conventional cleaning device, simplifying the structure of the heat fixing device. In addition, the maintenance cycle of the heat fixing device and the life of the heat fixing device can be extended.

[Brief description of drawings]

FIG. 1 is a side view showing a schematic structure of an electrophotographic recording apparatus used for carrying out the method of the present invention, and FIG. 2 is a schematic perspective view of a main part of a recording paper running stopper used for preventing rotation of a recording paper roll. FIG. 3 is a schematic side view showing another example of the electrophotographic recording apparatus used for carrying out the method of the present invention, and FIGS. 4 to 8 show the temperature dependence of each force acting on the toner in the fixing portion. 4 is a graph for explaining, FIG. 4 is a graph showing a relationship between toner cohesive force and temperature, FIG. 5 is a graph showing a relationship between surface temperature of each roller of the heat fixing device and time, and FIG. 6 is a toner. FIG. 7 is a graph showing the relationship between adhesive force and temperature, FIG. 7 is a graph showing the relationship between van der Waals force and temperature, FIG. 8 is a graph showing the relationship between toner adsorption force and temperature, and FIG. It is a side view showing a schematic configuration of a heat fixing device. 20 ... Photosensitive drum, 21a ... Recording paper roll, 21b ... Recording paper, 22
... paper feed roller, 22a ... drive roller, 22b ... driven roller, 24
… Cutter, 25… Feed roller, 25a… Drive roller, 25b
... following roller, 27 ... motor, 28 ... transfer and peeling section, 29 ... heat fixing device, 29a ... heat roller, 29b ... backup roller, 31 ... motor, 32 ... paper ejection sensor, 33 ... recording paper spool, 33a ... projection Part, 34 ... Solenoid, 35 ... Motor, 36 ...
Clutch, 37 ... Recording paper running stopper.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication location G03G 21/10 (72) Inventor Kiyoshi Futaki 2-3-3 Shimomeguro, Meguro-ku, Tokyo Matsushita Dentsu Co., Ltd. (72) Inventor Kotaro Takada 2-3-8 Shimomeguro, Meguro-ku, Tokyo Matsushita Dentsu Co., Ltd. (56) Reference JP 62-284377 (JP, A) JP 60-263182 (JP, A) JP-A-63-274980 (JP, A)

Claims (3)

[Claims] 1. A recording sheet is fed between a heat roller and a backup roller of a thermal fixing device during a non-recording operation, and the recording sheet is run with the recording sheet sandwiched by the heat roller and the backup roller. A method for cleaning a heat fixing device, characterized in that a speed difference is generated between a speed and a peripheral speed of a heat roller to remove stains on the heat roller on a recording paper. 2. A non-recording operation wherein a heat roller and a backup roller of a heat fixing device are brought into contact with each other and rotated,
During the rotation, the heat roller surface temperature and the backup roller surface temperature are set to a temperature range in which the adhesive force between the heat roller surface and the toner is larger than the adhesive force between the backup roller and the toner. A method for cleaning a heat fixing device, which comprises transferring dirt to a heat roller. 3. A heat roller and a backup roller of a heat fixing device are brought into contact with each other and rotated during non-recording operation,
During the rotation, the heat roller surface temperature and the backup roller surface temperature are set to a temperature range in which the adhesive force between the heat roller surface and the toner is larger than the adhesive force between the backup roller and the toner. The dirt is transferred to a heat roller, and then the recording paper is supplied between the heat roller and the backup roller. While the recording paper is sandwiched between the heat roller and the backup roller, the running speed of the recording paper and the heat are applied. A method for cleaning a thermal fixing device, characterized in that a speed difference is generated between the peripheral speed of the roller and the dirt of the heat roller is removed by a recording paper.