JPH08305206A - Fixing device - Google Patents

Abstract

PURPOSE: To reduce overshoot by the methods other than the changes of structure of a fixing roller and material quality by using a hollow core material for forming an oil supply rotor of an oil supply means. CONSTITUTION: An oil supply means is formed by an oil application roller 1, oil pumping rollers 2, 3, and application oil 16. The oil application roller 1 is so constructed that a surface layer 5 where rubber is made to adhere in several layers is provided on the outside of a core bar 4 which is a metallic core material, and the oil pumping roller 2 is formed only by a metallic core material 6. After the flow of an electric current is stopped, the temperature of the inner surface of a fixing roller 7 is lowered, and the surface temperature is raised to cause overshoot. Accordingly, it is better to decrease the heat radiation amount from the fixing roller 7 to the oil roller system. In order to decrease the above heat ratiation amount, the heat capacity of the oil roller system may be reduced to the utmost, and the heat capacity of the oil roller system can be decreased by making the oil application roller 1 and the oil pumping roller 2 hollow.

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 recording apparatus such as a copying machine and a laser beam printer, which comprises a fixing rotator, a pressure rotator and an oil supply means. Applying oil to at least one of the rotating body for pressurization and the rotating body for pressurization, at least one of the rotating body for fixing and the rotating body for pressurization uses radiation from a heat source such as a halogen heater. The present invention relates to a fixing device that performs fixing by heating by heating and nipping and transporting a transfer material such as paper on which a developer such as toner is transferred at a pressure contact portion of the fixing rotation body and the pressure rotation body.

[0002]

2. Description of the Related Art The structure of such a conventional fixing device is shown in FIG.
Shown in In FIG. 3, 7 is a fixing roller which is a fixing rotating body, and the fixing roller 7 is a core metal 9 which is a metal core material.
Is formed by coating the surface layer 10 of rubber or resin on the surface of the. Further, below the fixing roller 7,
Similarly, a pressure roller 8 as a pressure rotating body, in which a surface of a core metal 9 which is a metal core material is coated with a surface layer 10 such as rubber or resin, is arranged so as to be in pressure contact with the fixing roller 7. A contact area having a predetermined width (hereinafter referred to as a nip portion) is formed by these rollers. further,
A halogen heater 11 serving as a heat source is installed inside the fixing roller 7, and the radiant heat of the halogen heater 11 causes the fixing roller 7 to rotate.
The heat of the fixing roller 7 is raised and the temperature of the fixing roller 7 is maintained by the heat capacity of the fixing roller 7. In the conventional example shown in FIG. 3, the heat source is installed only on the fixing roller 7, but this heat source may be installed on the pressure roller 8 side as well.

However, in either case, heating and pressurizing can be performed in the nip portion of both rollers. For example, in the apparatus shown in FIG. 3, the nip portion of the fixing roller 7 and the pressure roller 8 develops toner or the like. When the transfer material 13 such as paper on which the agent 12 is placed passes, heat is supplied from the fixing roller 7 to the developer 12 and the transfer material 13 and the pressure by the fixing roller 7 and the pressure roller 8 causes the developer 12 to pass through. Are fixed on the transfer material 13.

Therefore, in the fixing device having such a structure, unfixed developer, paper dust, or the like adheres to the fixing roller 7 or the pressure roller 8 to stain the transfer material at the next fixing. May have an adverse effect.

Therefore, conventionally, as shown in FIG. 3, for example, an oil application roller 14 as an oil supply rotating body is used.
Also, an oil supply means including the oil pumping roller 15 and the coating oil 16 is provided, the oil 16 is supplied to the oil coating roller 14 by the oil pumping roller 15, and the oil is further applied to the surface of the fixing roller 7 by the oil coating roller 14. 16 and apply the developer and the fixing roller 7
The separation property of the transfer material is improved to prevent the above-mentioned stains on the transfer material. In the apparatus shown in FIG. 3, the oil supply means is provided on the fixing roller 7 side, but the oil supply means may also be provided on the pressure roller 8 side.

Further, in the fixing device having the above-mentioned structure, not only the fixing roller 7 but also the surroundings become considerably high in temperature and power consumption is large, so that the transfer material in the nip portion between the fixing roller 7 and the pressure roller 8 is large. Halogen heater 11 for heating fixing roller 7 at the same time when the passage of 13 is completed
Power supply to the halogen heater 11 is stopped.
There is a case in which a so-called overshoot phenomenon occurs in which the temperature of the surface of the fixing roller 7 rapidly rises despite the fact that the heat supplied from the inside is lost.

If this overshoot is large, the surface layer 1
Although the heat resistance of the rubber of 0, the peeling at the interface between the core metal 9 and the rubber of the surface layer 10, and the safety standard are problems, the magnitude of this overshoot depends on the thickness and the thermal conductivity of the rubber of the surface layer 10, It is a well-known fact that it depends on the heat capacity of the cored bar 9 and the like, and in the conventional fixing device design, the thickness of the rubber of the surface layer 10 and the thermal conductivity were changed to take measures to reduce the overshoot.

[0008]

However, in the above-mentioned conventional example, by reducing the thickness of the rubber of the surface layer 10 or by increasing the thermal conductivity of the rubber, the heat capacity of the cored bar 10 is further increased. Although the amount of overshoot as described above can be reduced by decreasing, the optimization of these parameters may cause a design limit, and therefore the overshoot cannot be reduced sufficiently. There was an occasion.

Therefore, it is an object of the present invention to provide a fixing device capable of reducing the above-mentioned overshoot by a method other than changing the structure and material of the fixing roller.

[0010]

According to the first invention of the present application, the above object is to provide a rotating body pair composed of a rotating body for fixing and a rotating body for pressurizing, and a rotating body for supplying oil to the rotating body. An oil supply means for supplying oil to heat the rotating body by using a heat source inside at least one rotating body of the rotating body pair, and apply pressure to the transfer material on which the developer is transferred passing through the rotating body pair. In the fixing device for applying the heat and fixing the developer to the transfer material, the core material forming the oil supply rotating body of the oil supply means is hollow.

According to the second invention of the present application,
The above object is achieved in the first invention, in which the core material of the fixing rotary member and the pressurizing rotary oil supplying rotary member is formed of a metal having a lower specific heat than iron.

Further, according to the third invention of the present application, the above object is achieved by the core material of the oil supply rotary member being formed of aluminum in the first invention.

According to the fourth invention of the present application,
The above object is achieved in the first aspect of the present invention, in which the core material of the oil supply rotary body is made of Teflon.

Further, according to a fifth invention of the present application, in the above-mentioned first object, the oil supply rotary member has an elastic surface layer on a metal core material.
This is achieved by having a layered structure.

According to the sixth invention of the present application,
The above object is provided with a rotating body pair composed of a fixing rotating body and a pressing rotating body, and an oil supply means for supplying oil to the rotating body by an oil supplying rotating body, and at least one rotating body of the rotating body pair. In the fixing device for heating the rotating body by using a heat source inside the body and applying pressure and heat to the transfer material on which the developer is transferred passing through the pair of rotating bodies to fix the developer on the transfer material, This is achieved by providing means for preheating the supply means to a temperature higher than room temperature.

Further, according to the seventh invention of the present application, in the above-mentioned sixth invention, the temperature of the oil supply means is at least the same as the control temperature during the fixing operation of the fixing rotator. It is achieved by

According to the eighth invention of the present application,
The above object is achieved in the sixth invention or the seventh invention, in which the means for preheating the oil supply means to a temperature higher than room temperature is a heater provided inside the oil supply rotary body.

Further, according to the ninth invention of the present application, the above-mentioned object is to provide a pair of rotating members consisting of a fixing rotating member and a pressing rotating member, and to supply oil to the rotating member by an oil supplying rotating member. An oil supply unit for heating the rotating body using a heat source inside at least one rotating body of the rotating body pair, and applying pressure and heat to the transfer material on which the developer is transferred passing through the rotating body pair. In the fixing device for fixing the developer to the transfer material, the oil supply rotary member of the oil supply unit is provided on the fixing rotary member or on both the fixing rotary member and the pressing rotary member. It is arranged so that it can be brought into and out of contact with and away from each other, and is from the fixing rotator, or the fixing rotator and the pressure rotator, except for the period in which the transfer material on which the developer is transferred passes through the pair of rotators. By keeping it separate from both sides of the body It is made.

Further, according to the tenth invention of the present application, a pair of rotating members composed of a fixing rotating member and a pressing rotating member, and an oil supplying means for supplying oil to the rotating member by the oil supplying rotating member. And heating the rotating body by using a heat source inside at least one rotating body of the rotating body pair, and applying pressure and heat to the transfer material on which the developer is transferred passing through the rotating body pair. In the fixing device for fixing the toner to the transfer material, the oil supply rotary member of the oil supply means is a fixing rotary member or an oil applying rotary member that applies oil to both the fixing rotary member and the pressing rotary member. The oil applying rotary body has an oil pumping rotary body for pumping oil, and the oil pumping rotary body is arranged so as to be able to come into contact with and separate from the oil applying rotary body. Transfer material with transferred agent Other periods passing through the pair of rotating members is achieved by keeping is separated from the oil coating rotator.

[0020]

By using a rotating body pair of a fixing rotating body and a pressing rotating body which are rotatably arranged in pressure contact with each other and a heat source arranged in at least one of the rotating bodies, a rotating body pair is formed. In a fixing device of a system in which a transfer material on which a developer has been transferred is passed through and heated and pressed to fix the developer to the transfer material, the heat source is provided before the transfer material passes through a pair of rotating bodies. The heating is started by, but when the transfer material passes through the rotating body pair, heat is taken from the surface of the heated rotating body to the transfer material side and the oil supply means side. On the other hand, heat is supplied from a heat source from the inside of the rotating body, but due to the heat capacity and the thermal conductivity of the rotating body, it takes a predetermined time for the heat to reach the surface of the rotating body. The surface temperature temporarily drops, and after the thermal transfer between the transfer material side and the oil supply means side on the surface of the rotating body becomes a steady state, the surface temperature starts to rise to a predetermined temperature. Therefore,
When in this steady state, there is a temperature difference between the inner surface and the surface of the rotating body, and this temperature difference is maintained during this steady state. As a result, at the time when the passage of the transfer material is completed and the power supply to the heat source is stopped, a temperature distribution in which the inner surface side becomes higher in the radial direction than the surface side occurs in the rotating body, and the heat distribution that makes this temperature distribution uniform is generated. Since movement occurs, the temperature of the surface of the rotating body rises, causing so-called overshoot.

Therefore, in the present invention, in order to reduce the overshoot, the temperature difference between the inner surface and the surface of the rotating body in the steady state is made small. It was decided to suppress the amount of heat released to the oil supply means.

The heat radiated to the oil supply means is represented by Q, where ΔT is the temperature difference between the oil supply means and the rotary body immediately after the transfer material passes through the rotating body pair, and the heat capacity Cρ of the entire oil supply means is Q. = ΔT · Cρ
In the present invention, by reducing both ΔT and Cρ,
The amount Q of heat radiated to the oil supply means is reduced to reduce the temperature difference between the inner surface and the surface of the rotating body in the steady state, thereby reducing the amount of overshoot.

That is, according to the first invention of the present application, the heat capacity Cρ is decreased and the overshoot amount is reduced by making the core material forming the oil supply rotor of the oil supply means hollow. Reduce.

According to the second invention of the present application,
In the first aspect of the present invention, the heat capacity Cρ is reduced and the overshoot amount is reduced by forming the core material with a metal having a lower specific heat than iron.

Further, according to the third invention of the present application, in the first invention, the core material is made of aluminum to reduce the heat capacity Cρ and reduce the overshoot amount.

According to the fourth invention of the present application,
In the first aspect of the present invention, the heat capacity Cρ is reduced and the overshoot amount is reduced by forming the core material from Teflon.

Further, according to a fifth invention of the present application, in the above first invention, the oil supply rotary body has a two-layer structure in which a resin layer is provided on a metal core material, The heat capacity Cρ is reduced to reduce the amount of overshoot.

According to the sixth invention of the present application,
By providing means for preheating the oil supply means to a temperature higher than room temperature, the temperature difference ΔT is reduced and the overshoot amount is reduced.

Further, according to the seventh invention of the present application, in the sixth invention, the temperature of the oil supply means is at least the same as the control temperature during the fixing operation of the fixing rotator. , The temperature difference ΔT is eliminated, and the overshoot amount is reduced.

According to the eighth invention of the present application,
In the sixth invention or the seventh invention, the heater provided inside the oil supply rotating body preheats the oil supply means to a temperature higher than room temperature to reduce or eliminate the temperature difference ΔT. , Reduce the amount of overshoot.

Further, according to the ninth invention of the present application, the oil supply rotary member of the oil supply means is provided with respect to the fixing rotary member or between the fixing rotary member and the pressing rotary member. The fixing member is arranged so as to be able to come into contact with and separate from both of them, and except the period in which the transfer material on which the developer is transferred passes through the pair of rotating members, from the fixing rotating member or the fixing rotating member and the pressure rotating member. By keeping it away from both sides of the body,
The transfer of heat from the fixing rotator, or both the fixing rotator and the pressurizing rotator to the oil supply rotator is eliminated, and the amount of heat stored in the oil supply rotator is retained, thereby supplying the oil. The temperature difference ΔT when the fixing rotary body is brought into contact with the fixing rotary body or both the fixing rotary body and the pressing rotary body is reduced, and the overshoot amount is reduced.

According to the tenth invention of the present application, among the oil supply rotary members of the oil supply means,
The oil scooping rotary body is arranged so as to be freely contactable and separable with respect to the oil coating rotary body, and the oil coating rotary body is provided except during the period in which the transfer material on which the developer is transferred passes through the rotary body pair. Is separated from the fixing rotator, or from both the fixing rotator and the pressurizing rotator, the transfer of heat to the oil pumping rotator is generated via the oil applying rotator. The amount of heat stored in the oil pumping rotor is retained, and the temperature difference ΔT when the oil pumping rotor is brought into contact with the oil coating rotor is reduced, and the overshoot amount is reduced.

[0033]

Embodiments of the present invention will be described below with reference to the accompanying drawings. First, an embodiment of the fixing device of the present invention is shown in FIG. In FIG. 1, reference numeral 7 denotes a fixing roller which is a fixing rotating body, and the fixing roller 7 is formed by coating a surface of a core metal 9 which is a metal core material with a surface layer 10 such as rubber or resin. Below the fixing roller 7, there is provided a pressure roller 8 as a pressure rotating body in which a surface of a core metal 9 which is also a metal core material is coated with a surface layer 10 such as rubber or resin. They are arranged so as to come into pressure contact with each other, and a contact area of a predetermined width (hereinafter,
The nip portion) is formed. Further, inside the fixing roller 7, a halogen heater 11 as a heat source is provided.
Is provided, heat is supplied to the fixing roller 7 by its radiant heat, the temperature of the fixing roller 7 is raised, and the temperature is maintained by the heat capacity of the fixing roller 7. In the apparatus shown in FIG. 1, the heat source is installed only on the fixing roller 7. However, when an image is formed on both surfaces of the transfer material 13, this heat source is also provided on the pressure roller 8 side. You may install similarly.

In such an apparatus, when the transfer material 13 such as paper having the developer 12 such as toner passes through the nip portion between the fixing roller 7 and the pressure roller 8, the developer 12 from the fixing roller 7 and The developer 12 is fixed to the transfer material 13 by the supply of heat to the transfer material 13 and the pressure of the fixing roller 7 and the pressure roller 8.

However, in the fixing device having such a structure, not only the fixing roller 7 but also the surroundings become considerably high in temperature and power consumption is large, so that the transfer material 13 in the nip portion between the fixing roller 7 and the pressure roller 8 is large. At the same time when the passage of the above is finished, the energization to the halogen heater 11 for heating the fixing roller 7 is stopped. At this time, although the heat supplied from the halogen heater 11 is lost, the surface of the fixing roller 7 is A phenomenon called so-called overshoot in which the temperature rises rapidly sometimes occurs.

The mechanism of occurrence of this overshoot will be described below with reference to the conventional apparatus of FIG. 3 and FIGS. 4 to 6.

In the fixing device shown in FIG. 3, before the transfer material 13 onto which the developer 12 has been transferred passes through the nip between the fixing roller 7 and the pressure roller 8, the fixing roller 7
Of the transfer material 13 is increased to a predetermined fixing temperature.
4 enters the nip portion, heat is rapidly removed from the surface of the fixing roller 7 in the direction of the arrow 20 as shown in FIG. 4, and from the surface of the fixing roller 7 in the direction of the arrow 22 on the oil applying roller 14 side. The heat is also taken away. Along with this, the surface temperature of the fixing roller 7 decreases as shown in FIG. On the other hand, the inner surface of the fixing roller 7 is supplied with heat from the halogen heater 11 in the direction of the arrow 21 to try to compensate for the surface temperature decrease, but the amount of heat applied to the fixing roller 7 reaches the surface. It takes a certain period of time t1 until
As shown in, the surface temperature of the fixing roller 7 continues to drop during this period t1. Hereinafter, this period t1 will be referred to as an initial temperature lowering period.

On the other hand, after the initial temperature lowering period t1 has elapsed and the amount of heat applied to the inner surface of the fixing roller 7 reaches the surface, the thermal transfer of heat by the fixing roller 7 becomes a steady state, but FIG. As shown in, the temperature difference ΔT1 between the inner surface and the surface of the fixing roller 7 in the steady state period t2 continues to maintain the temperature difference ΔT0 generated at the end of the initial temperature decrease period.

Therefore, at the time when the passage of the transfer material for a certain time is finished and the energization of the halogen heater 11 is stopped at the same time, a temperature distribution as shown by a curve 23 in FIG. 6 is generated in the radial direction of the fixing roller 7.

However, after the energization is stopped, heat is moved in the direction of the arrow 24 to make the temperature distribution uniform as shown in FIG. 6, so that the inner surface of the fixing roller 7 is rotated after a certain period of time t3 as shown in FIG. And the surface temperature becomes uniform. That is,
The temperature of the inner surface of the fixing roller 7 decreases and the temperature of the surface of the fixing roller 7 increases, resulting in an overshoot of ΔT2.

In order to reduce such an overshoot, the temperature difference ΔT1 between the inner surface and the surface of the fixing roller 7 in the steady state may be reduced. However, as described above, the temperature difference ΔT1 is in the initial temperature lowering period t1. Since the temperature difference ΔT0 at the end point is maintained, the temperature difference ΔT1 in the steady state can be reduced by decreasing the temperature difference ΔT0 at the end point of the initial temperature decrease period t1.

The temperature difference ΔT0 at the end of the initial temperature lowering period t1 is determined by the amount of heat released from the surface of the fixing roller 7 during the initial temperature lowering period t1, and the heat released from this fixing roller 7 is analyzed. The amount of heat applied to the developer 12, the transfer material 13, and the oil application roller 1
4 and the oil pumping roller 15 and the system including the oil 16 (hereinafter referred to as an oil roller system) can be roughly divided into heat amounts.

However, the amounts of heat applied to the developer 12 and the transfer material 13 are almost the same as the heat capacity of the core metal 9 of the fixing roller 7 and the surface layer 10.
Is determined only by the thermal conductivity of rubber,
As described in the explanation of the conventional example, the optimization of these parameters may have a design limit.

On the other hand, in the case of the conventional example shown in FIG. 3, the amount of heat applied to the oil roller system is ΔT3, which is the temperature difference between the oil roller system and the fixing roller 7 immediately after the transfer material 13 has passed through the nip portion. If the total heat capacity Cρ of
It is represented by Q = ΔT3 · Cρ.

Therefore, since the heat radiation amount Q to the oil roller system can be reduced by reducing both ΔT3 and Cρ, the temperature difference ΔT0 at the end of the initial temperature lowering period t1 can be reduced. Therefore, the amount of overshoot can be reduced.

Therefore, the present invention is intended to reduce the amount of overshoot by reducing the heat radiation amount Q from the fixing roller or both the fixing roller and the pressure roller to the oil roller system. is there.

A method for suppressing the heat radiation amount to the oil roller system will be specifically described below.

(First Embodiment) First, the expression Q = ΔT representing the heat radiation amount from the fixing roller to the oil roller system is first described.
An example of reducing the heat radiation amount Q by reducing Cρ in 3 · Cρ will be described.

FIG. 1 is a sectional view perpendicular to the axis of the oil applying roller of the fixing device according to the present invention. 1 in FIG.
Is an oil application roller as an oil supply rotating body,
Reference numeral 3 is an oil pumping roller as a rotating body for supplying oil, and 16 is coating oil. In this embodiment, these rollers and oil constitute an oil supply means (hereinafter referred to as an oil roller system).

As shown in FIG. 1, the oil applying roller 1 has a surface layer 5 to which several layers of rubber are adhered on the outside of a metal core 4 which is a metal core material. It is made of only a core material 6 made of.

In such a fixing device, the fixing roller 7 is warmed up to a predetermined temperature before the transfer material 13 passes through the nip portion, but at that time, the oil roller system is kept at almost room temperature. Accordingly, there is a temperature difference ΔT3 between the fixing roller 7 and the oil roller system in the initial stage after the transfer material 13 has passed through the nip portion, and the fixing roller 7 and the oil applying roller 1 are pressed against each other to rotate, so that the fixing is performed. Heat is radiated from the fixing roller 7 to the oil roller system until the temperatures of the roller 7 and the oil roller system become substantially the same. And
The amount of heat required for the temperature of the oil roller system to be the same as the temperature of the fixing roller 7 is proportional to the total heat capacity Cρ of the oil roller system.

Therefore, in order to reduce the heat radiation amount Q from the fixing roller 7 to the oil roller system, the heat capacity Cρ possessed by the oil roller system may be made as small as possible, and the oil application roller 1 as in this embodiment. Also, by making the oil pumping roller 2 hollow, the heat capacity Cρ can be reduced.

As a result, the amount of heat required to make the temperature of the oil roller system the same as that of the fixing roller 7 is reduced as compared with the conventional example, and the heat radiation amount Q from the fixing roller 7 to the oil roller system is reduced. be able to.

Since the pressure contact force between the oil applying roller 1 and the oil drawing roller 2 is not so good, there is no problem in terms of strength even if they are hollow.

By reducing the amount of heat radiated from the fixing roller to the oil roller system by the above method, as shown in FIG. 2, the temperature of the inner surface and the surface of the fixing roller 7 at the end of the initial temperature lowering period t1. The difference ΔT0 can be made smaller than in the past, and as a result, the amount of overshoot ΔT
It has become possible to reduce 2 as compared with the conventional one.

Further, iron was used as the material of the core metal of the conventional oil applying roller and the oil pumping roller, but the heat capacity ε becomes about 2/3 by changing it to aluminum. For the same reason as above, the same effect can be expected in reducing the amount of overshoot. Also,
A greater effect can be expected by using aluminum for the core metal and making the core metal hollow.

Not only aluminum but also a metal having a heat capacity smaller than that of iron, which is the material of the conventional oil applying roller and the oil drawing roller, is used as the material of the oil applying roller and the oil drawing roller. As a result, Cρ can also be made small, which can reduce the overshoot.

It is also effective to reduce the overshoot by using resin as the material of the oil application roller and the oil pumping roller. Teflon, for example, can be used as the resin to be used, but the heat capacity of Teflon is about 2/3 that of iron, and at the same time, the thermal conductivity is half that of iron (poor thermal conductivity), so the heat conduction inside Teflon However, the amount of heat flowing from the fixing roller to the oil applying roller per unit time is also reduced. Therefore, it is effective in reducing the amount of overshoot.

Further, a method in which the oil applying roller or the oil scooping roller has a two-layer structure and the surface layer of which is made of resin and the inner layer is made of metal is also effective in reducing overshoot. By using a resin such as Teflon on the surface layer,
As described above, both the heat capacity and the thermal conductivity are smaller than iron, and the inner layer metal material having a smaller heat capacity than iron is also used to increase the heat quantity Q from the fixing roller to the roller for oil application. It can be reduced.

(Second Embodiment) Next, the above equation Q = ΔT3
A method of reducing the heat radiation amount from the fixing roller to the oil application roller by reducing ΔT3 in Cρ will be described.

In order to reduce the temperature difference ΔT0 between the fixing roller and the oil roller system in the initial stage after the transfer material has passed through the nip portion, the temperature of the fixing roller is determined as the temperature control temperature. Should be changed.

That is, by heating the oil applying roller and the oil pumping roller or the oil to a temperature higher than room temperature before passing through the nip portion of the transfer material,
As compared with the conventional example, the temperature ΔT3 between the oil applying roller and the fixing roller becomes smaller, and as a result, the heat quantity Q from the fixing roller to the oil roller system becomes smaller, and the overshoot can be reduced.

Further, when the initial temperature of the oil roller system is raised to the same temperature as the control temperature of the fixing roller, ΔT0 becomes zero and the heat radiation amount from the fixing roller to the oil roller system disappears. Most effective in reducing overshoot.

As a structure for making the initial temperature of the oil roller system higher than room temperature, for example, there is a method of installing a heater inside a hollow oil application roller or the like.

(Third Embodiment) Next, a method of keeping the fixing roller and the oil applying roller apart from each other except during the period when the transfer material passes through the nip portion will be described.

When the transfer material passes through the nip portion, the fixing roller and the oil applying roller are in contact with each other, but since the temperature of the oil roller system is lower than that of the fixing roller, the fixing roller moves to the oil roller system. Heat flows to raise the temperature of the oil roller system to near the temperature of the fixing roller.

Here, comparing the heat capacities of the fixing roller and the oil roller system as a whole, comparing the area of the oil roller system that is larger and the area of the fixing roller that is in contact with the outside air with that of the oil roller system, The fixing roller is larger. Therefore, the amount of heat that escapes from the fixing roller after the transfer material has passed through the nip portion (the state where the heat supply from the heater is also cut off) is larger than the amount of heat that escapes from the oil roller system. In addition, because the entire heat capacity of the oil roller system is larger than that of the fixing roller, the temperature of the fixing roller becomes lower than that of the oil roller system after the transfer material has passed through the nip portion.

Therefore, the flow of heat after the transfer material has passed through the nip portion is the transfer of heat from the oil roller system to the fixing roller system, which is the reverse of the flow during the passage, and even after the transfer material has passed through the nip portion. If the oil roller system and the oil roller system are kept in contact with each other, the temperature of the oil roller system will drop at the same speed as the fixing roller due to the above heat flow.

Therefore, in this embodiment, after the transfer material has passed through the nip portion, the fixing roller and the oil roller system are separated from each other.

As a result, the transfer of heat from the oil roller system to the fixing roller does not occur after the transfer material has passed through the nip portion, and the amount of heat taken from the fixing roller by the oil roller system while the transfer material passes through the nip portion is eliminated. Can hold

Therefore, if the oil roller system holds a larger amount of heat, the temperature difference ΔT3 between the transfer roller and the fixing roller can be reduced when the transfer material passes through the nip portion next time. Since the amount of heat released from the fixing roller to the oil roller system when passing through the nip part of is small,
The amount of overshoot can be reduced.

Since the fixing roller is immediately heated by the heat from the heater placed at the center, there is no problem even if the temperature is lowered.

In each of the above-described embodiments, the case where the oil roller system is provided only on the fixing roller side has been described, but the present invention is not limited to this, and the oil roller system is provided on the pressure roller side. It is also applicable to a fixing device provided with.

Further, in each of the above-described embodiments, an example in which an oil applying roller and an oil pumping roller are used as the oil supply rotary member has been described, but fixing using a roller that also serves as an oil applying roller and an oil pumping roller is described. The present invention can be applied to an apparatus.

Further, it is also possible to separate the oil pumping roller, which is the oil pumping rotary member, from the oil coating roller, which is the oil coating rotary member, without separating the oil supply rotary member from the fixing roller or the like. .

[0076]

As described above, the first aspect of the present application
According to the invention, by making the core material forming the oil supply rotary body of the oil supply means hollow, from the heated fixing rotary body or from both the fixing rotary body and the pressurizing rotary body. The amount of heat radiated to the oil supply means can be reduced, and the amount of overshoot can be reduced without changing the structure or material of the fixing rotator or the like.

According to the second invention of the present application,
In the first invention, by supplying the core material with a metal having a lower specific heat than iron, oil is supplied from the heated fixing rotator or from both the fixing rotator and the pressure rotator. The amount of heat radiated to the means can be reduced, without changing the structure or material of the fixing rotator, etc.
The amount of overshoot can be reduced.

Further, according to a third invention of the present application, in the first invention, the core material is formed of aluminum so that the core is made of a heated fixing body or is heated. It is possible to reduce the amount of heat radiated from both the pressure applying rotary member and the oil supply unit, and it is possible to reduce the amount of overshoot without changing the structure or material of the fixing rotary member or the like.

According to the fourth invention of the present application,
In the first aspect of the present invention, by forming the core material from Teflon, the amount of heat radiated from the heated fixing rotator, or both the fixing rotator and the pressure rotator to the oil supply unit is increased. The amount of overshoot can be reduced without changing the structure or material of the fixing rotator or the like.

Further, according to the fifth invention of the present application, in the first invention, the oil supply rotary body has a two-layer structure having an elastic surface layer on a metal core material. The amount of heat radiated from the heated fixing rotator, or both the fixing rotator and the pressurizing rotator to the oil supply means can be reduced, and the structure and materials of the fixing rotator and the like can be reduced. The amount of overshoot can be reduced without changing.

According to the sixth invention of the present application,
By providing a means for preheating the oil supply means to a temperature higher than room temperature, the amount of heat radiated from the heated fixing rotator, or both the fixing rotator and the pressure rotator to the oil supply means The amount of overshoot can be reduced without changing the structure or material of the fixing rotator or the like.

Further, according to the seventh invention of the present application, in the sixth invention, the temperature of the oil supply means is at least the same as the control temperature of the fixing rotator during the fixing operation. The amount of heat radiated from the heated fixing rotator, or both the fixing rotator and the pressure rotator to the oil supply means can be reduced, and the structure and material of the fixing rotator, etc. can be changed. Without doing
The amount of overshoot can be reduced.

According to the eighth invention of the present application,
In the sixth invention or the seventh invention, the heater provided inside the oil supply rotary body preheats the oil supply means to a temperature higher than room temperature, or the heated fixing rotary body or It is possible to reduce the amount of heat radiated from both the fixing rotator and the pressurizing rotator to the oil supply means, and to reduce the amount of overshoot without changing the structure or material of the fixing rotator or the like. it can.

Further, according to the ninth invention of the present application, the oil supply rotary member of the oil supply means is provided with respect to the fixing rotary member or between the fixing rotary member and the pressurizing rotary member. The fixing member is arranged so as to be able to come into contact with and separate from both of them, and except the period in which the transfer material on which the developer is transferred passes through the pair of rotating members, from the fixing rotating member or the fixing rotating member and the pressure rotating member By keeping it away from both sides of the body,
It is possible to reduce the amount of heat radiated from the heated fixing rotator, or both the fixing rotator and the pressure rotator to the oil supply means, and change the structure and material of the fixing rotator and the like. It is possible to reduce the amount of overshoot.

According to the tenth invention of the present application, among the oil supply rotary members of the oil supply means,
The oil scooping rotary body is arranged so as to be freely contactable and separable with respect to the oil coating rotary body, and the oil coating rotary body is provided except during the period in which the transfer material on which the developer is transferred passes through the rotary body pair. The distance from the heated fixing rotor, or from both the fixing rotor and the pressurizing rotor to the oil pumping rotor, is the amount of heat released to the oil pumping rotor. It can be reduced without changing the structure or material of the fixing rotator, etc.
The amount of overshoot can be reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view perpendicular to the axes of an oil applying roller and an oil scooping roller of a fixing device according to a first exemplary embodiment of the present invention.

FIG. 2 is a diagram comparing the magnitude of overshoot between the conventional fixing device and the fixing device of the present invention.

FIG. 3 is a cross-sectional view perpendicular to the axes of an oil applying roller and an oil scooping roller of a conventional fixing device.

4 is a diagram showing a concept of heat transfer from a fixing roller in the fixing device of FIG.

5 is a diagram showing a transient change in temperature of the inner surface and the surface of the fixing roller when the transfer material passes through the nip portion between the fixing roller and the pressure roller in the fixing device of FIG.

FIG. 6 is a conceptual diagram showing temperature distribution and heat transfer in the fixing roller after the transfer material has passed through a nip portion between the fixing roller and the pressure roller of the fixing device in FIG.

[Explanation of symbols]

1 oil application roller (rotating body for oil supply, rotating body for oil application) 2, 3 oil pumping roller (rotating body for oil supply,
Rotating body for oil pumping) 4,6 Core metal (core material) 5 Surface layer 7 Fixing roller (rotating body for fixing) 8 Pressure roller (rotating body for pressing) 12 Developer 13 Transfer material 16 Applied oil

Claims (10)

[Claims] 1. A rotary body pair comprising a fixing rotary body and a pressure rotary body, and an oil supply means for supplying oil to the rotary body by an oil supply rotary body, wherein at least one of the rotary body pairs is provided. A fixing device for heating a rotating body by using a heat source inside the rotating body and applying pressure and heat to a transfer material on which a developer is transferred, which passes through the rotating body pair, to fix the developer on the transfer material, A fixing device, wherein a core material forming an oil supply rotary member of the oil supply means is hollow. 2. The fixing device according to claim 1, wherein the core material of the oil supply rotary member is formed of a metal having a lower specific heat than iron. 3. The fixing device according to claim 1, wherein the core member of the oil supply rotary member is made of aluminum. 4. The fixing device according to claim 1, wherein the core material of the oil supplying rotary member is formed of a heat resistant resin. 5. The fixing device according to claim 1, wherein the oil supplying rotary member has a two-layer structure having an elastic surface layer on a metal core material. 6. A rotary body pair comprising a fixing rotary body and a pressure rotary body, and an oil supply means for supplying oil to the rotary body by an oil supply rotary body, wherein at least one of the rotary body pairs is provided. A fixing device for heating a rotating body by using a heat source inside the rotating body and applying pressure and heat to a transfer material on which a developer is transferred, which passes through the rotating body pair, to fix the developer on the transfer material, A fixing device comprising means for preheating the oil supply means to a temperature higher than room temperature. 7. The fixing device according to claim 6, wherein the temperature of the oil supply unit is at least the same as the control temperature of the fixing rotator during the fixing operation. 8. The fixing device according to claim 6, wherein the means for preheating the oil supply means to a temperature higher than room temperature is a heater provided inside the oil supply rotary member. 9. A rotary body pair comprising a fixing rotary body and a pressurizing rotary body, and an oil supply means for supplying oil to the rotary body by an oil supply rotary body, wherein at least one of the rotary body pairs is provided. A fixing device for heating a rotating body by using a heat source inside the rotating body and applying pressure and heat to a transfer material on which a developer is transferred, which passes through the rotating body pair, to fix the developer on the transfer material, The oil supply rotary member of the oil supply means is disposed so as to be able to come into contact with and separate from the fixing rotary member or both the fixing rotary member and the pressurizing rotary member. A fixing device characterized in that it is separated from the fixing rotary member or from both the fixing rotary member and the pressing rotary member except during a period in which the transferred transfer material passes through the rotating member pair. 10. A rotary body pair comprising a fixing rotary body and a pressurizing rotary body, and an oil supply means for supplying oil to the rotary body by an oil supply rotary body, wherein at least one of the rotary body pairs is provided. In a fixing device that heats a rotating body by using a heat source inside the rotating body and applies pressure and heat to the transfer material on which the developer has been transferred passing through the pair of rotating bodies to fix the developer on the transfer material, The oil supply rotary member of the supply means is an oil application rotary member that applies oil to the fixing rotary member or both the fixing rotary member and the pressurizing rotary member, and an oil pumping pump that pumps oil to the oil application rotary member. And a rotating body for oil pumping,
It is arranged so as to be able to come in contact with and separate from the oil application rotary body, and is separated from the oil application rotary body except during a period in which the transfer material on which the developer is transferred passes through the rotary body pair. A fixing device characterized by the above.