JPH11194647A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent blister or toner blister from occurring on coating paper by setting the set temperature of a fixing member and that of an endless belt- like fixing member to different values, providing a contacting and separating means and individually rotating the endless belt-like fixing member. SOLUTION: By driving and rotating a roll for driving a belt 26 by a motor for driving a belt 28, a pressure belt is driven and rotated singly, so that the surface temperature of the pressure belt is made uniform in a rotating direction. When a fixing start signal is inputted, the contacting and separating means 21 of the pressure belt is actuated, so that the pressure belt starts to press- contact with a thermal fixing roll 1, and simultaneously the roll 1 starts to rotate. In such a case, the pressure belt is heated and kept at the set temperature lower than the surface temperature of the roll 1 by specified temperature by a roll for laying 11 having a heating source 15, and the quantity of heat applied to transfer paper 16 from the rear surface is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device used in an image forming apparatus such as a copying machine or a printer using an electrophotographic method, and more particularly, to a method of separating a belt-shaped fixing member from a heat fixing member during standby. The present invention relates to a fixing device capable of preventing a phenomenon called “blister” or “toner blister”, which is likely to occur at the time of fixing coated paper at the start of sheet feeding, by heating while idling.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine or a printer using this type of electrophotographic system, a toner image is formed on a photosensitive drum, and the toner image formed on the photosensitive drum is formed. Is transferred and fixed on a transfer sheet, or a plurality of toner images sequentially formed on a photosensitive drum are transferred once on an intermediate transfer member, and then transferred and fixed on a transfer sheet at once. Alternatively, a black-and-white or color image is formed by forming multiple toner images of different colors on the photosensitive drum and then transferring and fixing them collectively on transfer paper.

In an image forming apparatus such as a copying machine or a printer, in particular, a full-color image forming apparatus, in order to improve the color developing property and image quality of a toner image by imparting gloss to the surface of a transfer sheet, As a transfer sheet, as shown in FIG.
A so-called coated paper may be used in which a coating layer 102 made of synthetic rubber, synthetic resin, or the like is coated on the surface or both front and back surfaces to a thickness of several μ to several tens μ.

[0004] When an unfixed image is fixed on such coated paper by a fixing device, a phenomenon called a "blister" occurs in which an excessive amount of heat is applied to the coated paper to partially push up the coated layer. In addition, the smoothness of the coated paper is lost. This is because the water inside the coated paper evaporates and the volume expands due to the heating by the fixing device, but the vaporized water vapor is discharged to the outside of the paper by the coating layer 102 made of synthetic rubber or the like applied to the surface of the paper 100. As shown in FIG.
02 is intensively emitted to the outside from a thin portion of 02 or a portion where the coat layer 102 is absent, and this is generated when the coat layer 102 is broken. Therefore, the image on the paper 100 on which the “blister” has occurred is deteriorated because fine unevenness occurs on the background coat layer 102 and the smoothness of the coated paper is lost.

[0005] In addition to the phenomenon called "blister", when the coated paper 100 on which a high-density toner image such as a full-color image is transferred is subjected to a fixing process, as shown in FIG. The water vapor generated in the toner layer 103 by the heating by the fixing device and the coated paper 100
A phenomenon called so-called “toner blister” occurs in which the water vapor generated inside the paper does not escape to the back side of the paper 100 due to the coating layer 102 made of the synthetic rubber or the like of the coated paper 100 and forms bubbles in the toner layer 103. I do. This phenomenon called “toner blister” also deteriorates an image similarly to the above-mentioned “blister”.

Therefore, the following two methods have already been known as technical means for preventing the phenomenon called "blister" or "toner blister".

The first method is a method of heating at a high temperature and shortening the heating time, by heating only the surface of the transfer sheet and completing the fixing operation before the heat is transmitted to the inside of the sheet. , Suppresses evaporation of water inside the paper,
This is to prevent a phenomenon called "blister" or "toner blister".

A second method is to reduce the amount of heat applied to the transfer sheet from the back surface. This method also suppresses evaporation of water inside the sheet and relatively increases the heating time. It is known that by keeping the temperature on the pressure side on the back surface of the paper low, it is also suitable for high-speed fixing.

[0009]

However, the prior art described above has the following problems. That is, among the technical means for preventing the phenomenon called "blister" or "toner blister", in the case of the first method, it is necessary to maintain the fixing device at a high temperature, and accordingly, the fixing device has There is a problem in that power consumption increases, and the fixing is not suitable for a high-speed fixing device with limited power consumption in order to enable high-speed fixing.

In the case of the second method, as described above, the heating time is relatively long, but the power consumption can be suppressed by keeping the temperature on the pressure side of the back surface of the paper low. Although it is also suitable for high-speed fixing, in order to increase the speed of the fixing device, as shown in FIG. 14, as shown in FIG. The endless belt-shaped member 114 stretched by the rolls 111, 112, 113 is
When the transfer paper 100 is brought into pressure contact with the transfer paper 15, it becomes necessary to employ a fixing device in which the time during which heat and pressure act on the transfer paper 100 has been increased. In such a fixing device, the following problems newly arise. .

That is, as disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 5-150679, when a fixing device using an endless belt-shaped member as a pressing member is used to fix coated paper, the fixing is performed during standby. Since the fixing device is stopped, the surface temperature of the endless belt-shaped pressing member 114 is partially different at this time, as shown in FIG. For example, the surface temperature of the belt at a portion where the heating fixing roll 115 and the belt-shaped pressing member 114 are in contact with each other is substantially equal to the temperature of the heating fixing roll 115. However,
The surface temperature of the portion of the belt-shaped pressing member that is not in contact with the heat fixing roller 115 remains low because there is no heating source. As a result, when the fixing device starts operating, blisters of the coated paper are partially generated along the circumferential direction of the belt-shaped pressing member due to the uneven temperature of the belt surface, There is a problem that image degradation occurs.

Such unevenness of the belt surface temperature can be solved by idling the belt-shaped pressing member before starting the fixing operation. In such a case, the temperature of the belt-shaped pressing member is reduced. Becomes equivalent to the temperature of the heat-fixing roll, and the amount of heat from the pressurized side, which is a measure to prevent “blister” of coated paper, cannot be reduced.
It cannot solve the problem that the error occurs. Further, since the fixing operation cannot be performed during the idling operation, the start time of the first copy is delayed by that amount, and the first copy performance is deteriorated.

Accordingly, the present invention has been made to solve the above-mentioned problems of the prior art, and an object thereof is to provide an endless belt as a pressing member or a heating member in order to enable high-speed fixing. Provided is a fixing device that can reliably prevent the occurrence of "blisters" and "toner blisters" on coated paper even when a shaped member is used, and can also prevent poor first copy performance. It is in.

[0014]

That is, according to the first aspect of the present invention, an endless belt-shaped fixing member having a heating source stretched by a plurality of rolls is pressed against a surface of a fixing member having a heating source. A fixing member for performing a fixing process by heat and pressure by passing a transfer material carrying an unfixed toner image through a pressure contact portion between the fixing member and the endless belt-shaped fixing member. The fixing temperature of the endless belt-shaped fixing member is set to a different value, and a contact / separation means for contacting and separating the fixing member and the endless belt-shaped fixing member is provided, and the endless belt-shaped fixing member is independently provided. It is configured to provide a driving means for rotationally driving. As the fixing member having the heating source, for example, a heating fixing roll having a heating source inside or outside is used. As the endless belt-shaped fixing member, for example, a pressure belt stretched by a plurality of rolls is used. However, the present invention is not limited to this. An endless belt-shaped fixing member is used as a heating-side fixing member, and a pressing-side fixing member is formed by a roll-shaped member. Both members may be constituted by endless belt-shaped fixing members.

According to a second aspect of the present invention, at least one of the heating sources for heating the endless belt-shaped fixing member is located at a position higher than a pressure contact portion between the endless belt-shaped fixing member and the fixing member. The fixing device according to claim 1, wherein the fixing device is arranged on an upstream side.

Further, according to a third aspect of the present invention, the set temperature of the endless belt-shaped fixing member is controlled based on a detection result of a temperature detecting means disposed downstream of a tension roll having a heating source. 3. The method according to claim 1, wherein
3. The fixing device according to item 1.

Further, the invention according to claim 4 is characterized in that the set temperature of the endless belt-shaped fixing member is set to a value lower than the set temperature of the fixing member by 20 ° C. or more. A fixing device according to any one of claims 1 to 3.

According to a fifth aspect of the present invention, in the fixing device according to any one of the first to fourth aspects, the endless belt-shaped fixing member is separated from the fixing member during standby. is there.

The fixing device according to any one of claims 1 to 5, wherein the endless belt-shaped fixing member is rotated and heated during standby. It is.

Further, according to a seventh aspect of the present invention, the rotation speed of the endless belt-shaped fixing member during standby is:
7. The fixing device according to claim 1, wherein the temperature difference between the endless belt-shaped fixing member on the upstream side and the downstream side of the stretching roll having a heating source is set to be within 2 [deg.] C. It is a fixing device.

The invention according to claim 8, wherein the time from the start of the contact between the endless belt-shaped fixing member and the fixing member to the start of the nip of the transfer material is equal to the time of the endless belt-shaped fixing member and the fixing member. 8. The fixing device according to claim 1, wherein the temperature difference is set to be equal to or higher than 10 ° C.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on an embodiment shown in the drawings.

Embodiment 1 FIG. 1 is a configuration diagram showing an embodiment of a fixing device according to the present invention.

In FIG. 1, reference numeral 1 denotes a heating fixing roll as a fixing member having a heating source, and the heating fixing roll 1 is rotationally driven at a predetermined peripheral speed along a direction indicated by an arrow by a driving source (not shown). It is supposed to be.
The heat fixing roll 1 has a metal core 2,
As the metal core 2, for example, one made of aluminum, stainless steel, or the like is used. The surface of the metal core 2 is coated with an elastic layer 3, and the surface of the elastic layer 3 is further coated with a top coat layer 4.
Is finished in a state close to a mirror surface state. The metal core 2 may be made of a metal having a high thermal conductivity other than aluminum or stainless steel. The top coat layer 4 may be any heat-resistant elastic material. Materials can be used.

A halogen lamp 5 is disposed inside the metal core 2 as a heating source, and the heating and fixing roll 1 is heated from the inside by the halogen lamp 5 so that the surface temperature becomes a predetermined temperature. It is supposed to be. The surface temperature of the heat-fixing roll 1 is detected by a temperature sensor 6 that is in contact with the surface of the central portion of the heat-fixing roll 1.
It is configured to be controlled by a temperature controller (not shown) so that the temperature becomes 50 ° C.

Further, on the surface of the heat-fixing roll 1, for example, a dimethyl silicone oil viscosity of 1000 cs (trade name “KF-96” manufactured by Shin-Etsu Chemical Co., Ltd.) as a release agent is supplied by a release agent supply device 8. It is supplied uniformly. The release agent supply device 8 includes a release agent supply roll 8c to which the release agent 8b accommodated in the oil pan 8a is supplied.
The release agent 8b attached to the surface of the release agent supply roll 8c is supplied, and the release agent 8b
And a release agent applying roll 8d for applying the coating agent. Then, the release agent supply device 8 rotates the release agent application roll 8 d and the release agent supply roll 8 c with the rotation of the heat fixing roll 1, so that the surface of the heat fixing roll 1 is released. 8b is applied and supplied.

Further, below the heat fixing roll 1,
A belt module 9 having a pressure belt 10 as an endless belt-shaped pressure member is disposed so as to be pressed against a predetermined nip width. This belt module 9
It is mainly composed of a pressure belt 10 and three rolls 11, 12, 13 that stretch the pressure belt 10.
The pressure belt 10 has, for example, a thickness of 75 μm and a width of 30 μm.
It is formed of a polyimide film or the like having a circumference of 0 mm and a length of 188 mm, and is stretched by three rolls 11, 12, and 13 with a tension of about 8 kg. The above three rolls 1
The diameters of 1, 12, and 13 are, for example, 23 mm, respectively.
It is set to 18 mm and 18 mm. The three rolls 11, 12, and 13 are formed, for example, in a cylindrical shape or a cylindrical shape by stainless steel or the like. By tilting the rotation axis of the rolls 13, the bias of the pressure belt 10 is prevented. Roll 13 as a so-called steering roll
When using a roll, the roll 13 may be formed by coating a surface of a cylindrical or columnar member made of metal such as stainless steel with an elastic layer. Further, a pressure contact member 14 for pressing the endless belt 10 against the surface of the heat fixing roll 1 with a predetermined pressure is disposed between the roll 11 and the roll 12. The outlet of the belt nip is connected to the pressure roll 11 via the belt 10 at about 20 kgf.
Is pressed against the heat fixing roll 1 with a load of. For this reason, the elastic layer 3 of the heat fixing roll 1 is deformed, distortion ε is generated on the surface thereof, and the transfer paper 16 can be peeled off by its own rigidity. In the figure, reference numeral 15 denotes a halogen lamp for heating the pressure belt 10 disposed inside the stainless steel roll 11. Reference numeral 17 denotes an unfixed toner image transferred onto the transfer paper 16.

The pressing member 14 is, as shown in FIG.
The elastic layer 14b is laminated on the surface of the base plate 14a, and the surface of the elastic layer 14b is
As shown in FIG. 2,
It is pressed toward the heat fixing roll 1 by a compression coil spring 18 disposed on the base plate 14a side. As the base plate 14a, for example, a stainless steel plate having a width (the running direction of the belt) of 20 mm, a length (a direction perpendicular to the paper surface) of 320 mm, and a thickness of 5 mm is used. The elastic layer 14b has a rubber hardness of 2
3 ° silicone sponge (silicone rubber foam)
5 mm in thickness is used. Here, the rubber hardness is a result measured by adding a load of 300 gf with a rubber hardness meter for sponge of Asker C type manufactured by Kobunshi Kagaku. Further, as the low friction layer 14c,
"FGF-400-4" (trade name) manufactured by Chuko Kasei, which is a glass fiber sheet impregnated with polytetrafluoroethylene, is used.

Here, the pressing member 14 is provided with an elastic layer 14b.
, The pressure belt 10 of the low friction layer 14c
The contact surface that makes contact with the outer peripheral surface of the heat fixing roll 1 can be aligned. That is, if the pressing member 14 is pressed toward the heat fixing roll 1 by a load equal to or more than a certain value,
The elastic layer 14b is deformed so that the contact surface of the low friction layer 14c is pressed along the outer peripheral surface of the heat fixing roll 1. Therefore, when the pressing member 14 is pressed against the heat fixing roll 1 by the compression coil spring 18, the pressing belt 10 is pressed against the heat fixing roll 1 without any gap.

On the surface of the pressure belt 10, dimethyl silicone oil having a viscosity of 1000 cs (trade name "K
F-96 "(Shin-Etsu Chemical Co., Ltd.) supplies a release agent (not shown) configured in the same manner as the release agent supply device 8 for applying a release agent to the surface of the heat fixing roll 1 as shown in FIG. The device is adapted to apply the toner, thereby also preventing toner offset on the surface of the pressure belt 10.

Further, a cleaning device 20 for cleaning the surface of the heat-fixing roll 1 is disposed on the surface of the heat-fixing roll 1 as shown in FIG. The cleaning device 20 supplies the cleaning web 20b from the supply roll 20a, and presses the cleaning web 20b into contact with the cleaning web 20b while the cleaning web 20b is wound by a winding roll 20c that is rotated by a motor (not shown). Heat fixing roll 1 by roll 20d
By pressing against the surface of the fixing roller 1, offset toner and the like adhering to the surface of the heat fixing roll 1 are removed.

In this embodiment, the set temperature of the fixing member and the set temperature of the endless belt-shaped fixing member are set to different values, and the contact temperature for contacting and separating the fixing member and the endless belt-shaped fixing member is set. A separation unit is provided, and a driving unit for independently rotating and driving the endless belt-shaped fixing member is provided.

That is, in this embodiment, as shown in FIG. 2, a contact / separation means 21 for separating the pressure belt 10 from the surface of the heat fixing roll 1 is provided. The contact / separation means 21 includes three rolls 1 for stretching the pressure belt 10.
A frame 22, to which the eccentric cam 24 is attached, is supported so as to be swingable about a rotation shaft 23, and an eccentric cam 24 is brought into contact with a lower end of the frame 22 to drive the eccentric cam 24. The frame 25 is rotated by a predetermined amount by a motor 25 at a predetermined timing.
2 is configured to swing in the direction of coming and going with the heat fixing roll 1.

In the fixing device according to this embodiment, the heat source 1
5 is set lower than the set temperature of the heat fixing roll 1 by a predetermined temperature, for example, 25 ° C., and the amount of heat from the pressure belt 10 to the back surface of the transfer paper 16 is reduced. It is configured to hold down.

Further, in the fixing device according to this embodiment, the pressure belt 10 is configured to be rotatable at a predetermined timing independently of the heat fixing roll 1 and independently. Therefore, as shown in FIG. 1, a belt driving roll 26 is provided on the surface of the pressure belt 10 via a tension roll 11 having a heating source 15 so as to sandwich the pressure belt 10. The pressing belt 10 is rotated by a driving motor 28 via a driving gear 27 at a predetermined timing based on a driving signal from a motor control circuit 29 to thereby press the belt 10. It can be driven to rotate at a predetermined rotation speed at a predetermined timing independently of the heat fixing roll 1. It is not always necessary to separately provide a mechanism for rotating and driving the pressure belt 10 alone.
When applying a release agent using a release agent application device configured in the same manner as the release agent application device 8 shown in FIG. Of course, it may be configured to be independently driven to rotate. FIG.
Reference numeral 30 denotes a temperature detection sensor provided downstream of the tension roll 11 having the heating source 15 and configured to detect the temperature of the pressure belt 10.

In the fixing device according to this embodiment, in order to enable high-speed fixing in the following manner, even if an endless belt-shaped member is used as the pressing member or the heating member, the coating is performed as follows. "Blister" and "toner blister" on paper can be reliably prevented,
In addition, it is possible to prevent the first copy performance from being deteriorated.

That is, in the fixing device according to this embodiment, as shown in FIGS. 1 and 3, the heating fixing roll 1 is stopped during standby, while the pressure belt 10 is
It is in a state of being separated from the heat fixing roll 1. By doing so, the surface temperature of the pressure belt 10 is reduced
Can be in a state not affected by the temperature. However, as it is, as shown by a broken line in FIG. 5, the surface near and far from the heat-fixing roll 1 and the portion stretched by the stretching roll 11 having the heating source 15 and other portions are heated. The temperature of the pressure belt 10 differs. Therefore, the pressure belt 10 is driven to rotate independently by rotating the belt driving roll 26 by a belt driving motor 28, thereby reducing the surface temperature of the pressure belt 10.
As shown by the solid line in FIG. 5, it can be made uniform along the rotation direction.

Next, when a fixing start signal is inputted, as shown in FIG. 3, the contacting / separating means 21 of the pressure belt 10 operates.
As shown in FIG. 4, the pressure belt 10 starts to press against the heat fixing roll 1, and at the same time, the heat fixing roll 1 also starts rotating. Then, after the contact of the pressure belt 10 is completed, the transfer paper 16 arrives at the entrance of the nip immediately after a very short time of, for example, about 1 sec, is heated to a predetermined temperature, and is mutually pressed at a predetermined pressure. The fixing is started by the heat fixing roll 1 and the pressure belt 10 pressed against each other. Ideally, the time from the start to the completion of the contact operation between the pressure belt 10 and the heat fixing roll 1 is extremely short, and the arrival of the sheet after the contact is completed is ideally short.
This is because the main purpose is to perform the fixing operation without changing the temperature difference between the heat fixing roll 1 and the pressure belt 10 generated during the standby. And the pressure difference between the pressure belt 10 and the pressure belt 10 is reduced. The driving motor 28 for rotating and driving the pressure belt 10 alone is operated until the contact between the two is completed, so that the pressure belt 10 does not stop during the contact operation of the pressure belt 10. It has become.

During the fixing operation, since the pressure belt 10 and the heat fixing roll 1 are in pressure contact with each other, the temperature difference between the two seems to decrease. The temperature difference between the two is maintained. After the fixing operation is completed, that is, triggered by the passage of the last transfer paper 16 through the exit of the nip portion, the rotation motor 28 of the pressure belt 10 is started to operate, and The separation operation of the belt 10 is started. At this time, the time required for the separation operation of the pressure belt 10 is ideally the same as the time required for the contact operation, but the temperature of the pressure belt 10 can be corrected in the standby state after the separation operation is completed. Therefore, the time required for the separating operation of the pressure belt 10 does not matter so much.

As described above, in the fixing device according to the above embodiment, as shown in FIG. 1, the endless belt-shaped pressure belt 10 is used as the pressure member. Even when fixing a full-color toner image having a large amount of toner 17, pressure and heat can be applied to the transfer paper 16 made of coated paper or the like carrying the unfixed toner image 17 for a relatively long time, It goes without saying that high-speed fixing is possible, and during standby, while the pressure belt 10 is separated from the heat fixing roll 1 by the contact / separation means 21, the pressure belt 10 is independently driven to rotate, and the heating source 15 is turned on. The pressure belt 10 can be heated and maintained at a set temperature lower than the surface temperature of the heat fixing roll 1 by a predetermined temperature by the tension roll 11 having By reducing the amount of heat applied to the copy sheet 16, the coated paper "blister" or "toner blister" can be reliably prevented. Moreover, since the pressure belt 10 is uniformly heated to a predetermined temperature while being driven to rotate during standby,
Based on the fixing operation start signal, the pressure belt 10 can be pressed into contact with the heat fixing roll 1 in a short time to start the fixing operation, thereby preventing the first copy performance from being deteriorated. .

[0041]

[Experimental Example 1] FIG. 1 is a block diagram showing also an experimental example 1 of the fixing device according to the present invention.

In FIG. 1, reference numeral 1 denotes a heating / fixing roll. The heating / fixing roll 1 is driven by a driving source (not shown) at a predetermined rotational speed, for example, 7 along an arrow direction.
It is rotationally driven at 7.6 rpm. The above heat fixing roll 1
For example, the outer circumference of an aluminum core 2 having an outer diameter of 61 mm and a thickness of 1.5 mm is coated with HTV silicone rubber (rubber hardness: 45 degrees) as an elastic layer 3 to a thickness of 2 mm. On the surface of No. 3, Viton rubber (registered trademark of DuPont) was applied to a thickness of 30 μm to form an outer diameter of 65 mm. This heat-fixing roll 1 has 10 rolls disposed therein.
The surface set temperature is 1 by the 00W halogen lamp 5.
Heated to 50 ° C. On the other hand, the pressing belt 10
Is a 75 μm thick polyimide belt with a thickness of 100 μm.
It was formed by applying a silicon rubber of μm and a viton rubber of 30 μm in thickness. The pressing belt 10 is a tension roll 11 made of a stainless steel roll having a core thickness of 2 mm.
, A 250 W halogen lamp 15 as a heat source
And heated so that the surface setting temperature was 120 ° C. Then, the tension roll 11 is disposed upstream of the entrance of the nip portion, and the temperature detection sensor 30 is connected to the tension roll 1.
By arranging the pressure belt 10 on the downstream side from 1, the temperature of the pressure belt 10 at the nip entrance can be easily controlled to the set temperature. Further, the pressure belt 10 is separated by the contact / separation means 21 so as not to be in contact with the heat fixing roll 1 during standby, but the separation amount is not limited.

In the fixing device configured as described above,
A driving motor 28 for rotating the pressure belt 10 is operated to rotate the pressure belt 10 at a rotation speed of 60 rpm, and the three stretching rolls 11, 12, and 13 (stainless steel core 2 mm thick) and the fixing pad 14 is the pressure belt 10
Idle rotation until the temperature became equal to the set temperature.

In the fixing experiment, Oji Paper's OK coated paper A3 was used.
1.5 mg / cm for size (127.9 gsm basis weight)
^As shown in FIG. 6, ^two toner patches 30 (2 cm square) were formed at the three positions of the leading edge, the center, and the trailing edge of the transfer paper 16.

Then, first, the heat fixing roll 1 is
The pressure belt 10 and the heat fixing roll 1 were pressed against each other at a rotation speed of 7.6 rpm (the contact operation was performed for about 1 second).
c). About one second after the completion of the contact, the insertion of the transfer paper 16 into the nip portion was started. FIG. 7 shows a temperature change at the entrance of the nip portion of the pressure belt 10 at this time. Observation of the sample after fixing showed that not only "blister" but also "toner blister" was not generated.

Next, in the above experiment, the set temperature of the tension roll on the pressure side was increased by 10 ° C. in increments of 10 ° C., and the degree of occurrence of “blister” and “toner blister” was investigated. FIG. 8 shows the result.

As can be seen from FIG. 8, "blister"
The set temperature effective for preventing the generation of “toner blister” is that the temperature difference between the heat fixing roll 1 and the pressure belt 10 is 2
It is desirable that the temperature is 0 ° C. or higher.

Experimental Example 2 Next, the present inventor conducted an experiment for confirming the relationship between the contact timing and the temperature rise of the pressure belt 10 using the experimental apparatus used in Experimental Example 1 described above.

The experimental method is as follows.
The contact time of the roller with the heat-fixing roll 1 was set to 0 sec. Since the rotation of the heat fixing roll 1 is 77.6 rpm, a delay of about 0.8 sec occurs from the contact point to the temperature change of the pressure belt 10.

FIG. 9 shows the result of Experimental Example 2. As can be seen from the graph shown in FIG. 9, if the time until the pressure belt 10 and the heat fixing roll 1 come into contact with each other and the time until the start of paper passing after the contact is completed are long, the heating adjusted at the standby time Fixing roll 1 and pressure belt 1
The temperature difference of 0 decreases, and the temperature of the pressure belt 10 becomes close to that of the heat-fixing roll 1, causing the occurrence of “blister”. From the results of the graphs shown in FIG. 8 and FIG. There is.

Experimental Example 3 In Experimental Example 1 described above, the rotation speed of the pressure belt during standby was set to 60 rpm, but it is not necessary to constantly rotate the pressure belt at a rotation speed of 60 rpm during standby.

Therefore, in Experimental Example 3, the relationship between the rotational speed of the pressure belt and the temperature stability was examined.

As shown in FIG. 10, an infrared reflection type temperature sensor 40 for measuring the surface temperature of the pressure belt 10 is provided upstream and downstream of the stretching roll 11 having the heating source 15 as shown in FIG. 41, the rotational speed of the pressure belt 10 was sequentially reduced stepwise by the motor control circuit 29.

FIG. 11 shows the results of Experimental Example 3 above.

As can be seen from FIG. 11, if the three tension rolls 11 to 13 are heated to some extent, even if the rotation of the pressure belt 10 is reduced to 15 rpm, the heating source 15
Temperature difference between the upstream side and the downstream side of the tension roll 11 having
It can be within ° C.

As a result of the experiment, three tension rolls 11
When the temperature of the tension roller 13 is different (when the lighting time of the halogen lamp 15 of the stretching roll 11 is long), the pressure belt 10
It was found that by setting the rotation speed to 60 rpm, the temperature of each of the tension rolls 11 to 13 could be raised to the set temperature more quickly.

[0057]

As described above, according to the present invention, in order to enable high-speed fixing, even when an endless belt-shaped member is used as a pressing member or a heating member, "blister" or "toner blister" is applied to coated paper. Can be reliably prevented, and a fixing device capable of preventing the first copy performance from being deteriorated can be provided.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of a fixing device according to the present invention.

FIG. 2 is a configuration diagram showing a contacting / separating means.

FIG. 3 is a timing chart illustrating an operation of the fixing device.

FIG. 4 is a configuration diagram illustrating a fixing operation of the fixing device.

FIG. 5 is a graph showing the temperature of the pressure belt during standby.

FIG. 6 is an explanatory diagram showing a test chart.

FIG. 7 is a graph showing the temperature of the pressure belt.

FIG. 8 is a chart showing experimental results of Experimental Example 1.

FIG. 9 is a graph showing experimental results of Experimental Example 2.

FIG. 10 is a configuration diagram illustrating an experimental apparatus of Experimental Example 3.

FIG. 11 is a chart showing experimental results of Experimental Example 3;

FIG. 12 is an explanatory view showing a “blister” in a conventional coated paper.

FIG. 13 is an explanatory diagram showing a “toner blister” on a conventional coated paper.

FIG. 14 is a configuration diagram showing a conventional fixing device.

FIG. 15 is a graph showing the temperature of a belt-shaped pressing member in a conventional fixing device.

[Explanation of symbols]

1: Heat fixing roll, 5: Halogen lamp, 9: Belt module, 10: Pressure belt, 11 to 13: Stretch roll, 15: Halogen lamp, 21: Contact / separation means, 26: Roll for driving belt.

Claims (8)

[Claims] An endless belt-shaped fixing member having a heating source stretched by a plurality of rolls is pressed against the surface of a fixing member having a heating source, and the fixing member is pressed against the endless belt-shaped fixing member. In a fixing device that performs a fixing process by heat and pressure by passing a transfer material carrying an unfixed toner image through a unit, the set temperature of the fixing member and the set temperature of the endless belt-shaped fixing member are set to different values. A fixing device provided with contact / separation means for contacting and separating the fixing member and the endless belt-shaped fixing member, and a driving means for independently rotating and driving the endless belt-shaped fixing member. . 2. A heat source for heating the endless belt-shaped fixing member, wherein at least one of the heating sources is disposed upstream of a pressure contact portion between the endless belt-shaped fixing member and the fixing member. The fixing device according to claim 1. 3. The set temperature of the endless belt-shaped fixing member is controlled based on a detection result of a temperature detecting unit disposed downstream of a stretching roll having a heating source. 3. The fixing device according to 1 or 2. 4. The fixing device according to claim 1, wherein a set temperature of the endless belt-shaped fixing member is set to a value lower than a set temperature of the fixing member by 20 ° C. or more. . 5. The fixing device according to claim 1, wherein the endless belt-shaped fixing member is separated from the fixing member during standby. 6. The fixing device according to claim 1, wherein the endless belt-shaped fixing member is rotated and heated during standby. 7. The rotation speed of the endless belt-shaped fixing member during standby is such that the temperature difference between the endless belt-shaped fixing member on the upstream side and the downstream side of the stretching roll having a heating source is within 2 ° C. The fixing device according to any one of claims 1 to 6, wherein the fixing device is set as follows. 8. The time from the start of the contact between the endless belt-shaped fixing member and the fixing member to the start of the nip of the transfer material is:
The temperature difference between the endless belt-shaped fixing member and the fixing member is set to be not less than 10 ° C.
8. The fixing device according to any one of claims 1 to 7.