JP2002311751A - Fixing device and image forming device - Google Patents

Abstract

(57) [Problem] To solve the problem that the amount of power used exceeds the capacity of a commercial power supply and the safety at the time of heat source runaway assumed when temperature control is impossible becomes a problem. Things. The present invention provides a fixing member having a first heat source therein, a pressing member arranged to face the fixing member, and a second member which generates heat by receiving power supply.
An external heating member having a heat source 5 for heating the fixing member from the outside, and a driving unit for supplying electric power to the second heat source 5. The driving unit includes a power storage device 1 capable of rapid charging and discharging.
4 and a charger 15 that is supplied from the commercial power supply 12 and charges the power storage device 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for fixing toner on a sheet-shaped recording medium to the recording medium, and to an image forming apparatus such as a copying machine, a printer, and a facsimile.

[0002]

2. Description of the Related Art Generally, in an image forming apparatus such as an electrophotographic copying machine, a printer, and a facsimile, a fixing device in which a pressure roller is pressed against a fixing roller is used. In this fixing device, while rotating a fixing roller heated by a heat source, a sheet-shaped recording medium onto which toner has been transferred is inserted between the fixing roller and a pressure roller, and the toner is heated and melted to form a recording medium on the recording medium. To be established. As a heat source for heating the fixing roller, generally, a halogen heater using a halogen lamp has been used. The heat source is controlled so that the power supplied from the commercial power supply is controlled by the temperature control means so that the surface temperature of the fixing roller becomes a set value.

In such a fixing device, when the recording medium is inserted between the fixing roller and the pressure roller to fix the toner on the recording medium, the surface of the fixing member is supplied by supplying heat to the recording medium from the fixing roller. However, if the heat supply from the heat source to the fixing roller and the heat transfer to the fixing roller surface are not sufficient during one rotation of the fixing roller, the temperature of the fixing roller surface may return to the set value. Disappears.

In particular, when the peripheral length of the fixing roller is smaller than the dimension of the recording medium in the transport direction, heat supply from the fixing roller to the recording medium after one rotation of the fixing roller is performed during the first rotation of the fixing roller. It is smaller than that. As a result, there arises a problem that the gloss and the fixability of the image are different between the leading end and the trailing end in the transport direction of the recording medium, and fixing unevenness occurs.

In order to solve such a problem, the temperature just before the fixing roller enters the fixing nip portion (the nip portion between the fixing roller and the pressure roller) may be kept constant. Therefore, a technique has been proposed in which an external heating member for externally heating the surface of the fixing roller is provided to prevent the temperature of the surface of the fixing roller from lowering.

Japanese Patent Application Laid-Open No. 2000-98799 discloses a heating device for a fixing device having a heater which generates heat when supplied with electric power and a heater driving means for supplying electric power to the heater. A rechargeable battery, and a charger that is supplied with power from a commercial power supply and charges the storage battery, wherein the heater includes a main heater that is supplied with power from a commercial power supply, and an auxiliary heater that is supplied with power from the storage battery. And a heating device for the fixing device, wherein the charging of the storage battery is performed when the main heater is turned off.

Japanese Patent Application Laid-Open No. 8-314323 discloses an internal heater having a pair of rollers for inserting and pressing a recording medium to which unfixed toner is adhered, and having a heater in at least one of the rollers. An external / internal heating type fixing device having an external heater provided on the side to which the unfixed toner is attached, and driving the internal heater and the external heater to fix the unfixed toner on the recording medium. And a second step of driving only the external heater to fix the unfixed toner on the recording medium at a stage when the unfixed toner reaches a first set temperature lower than a fixable temperature at which the unfixed toner is fixed on the recording medium. An external / internal heating type fixing device characterized by controlling to a set temperature is described.

Japanese Patent Application Laid-Open No. 2000-315567 has a heating unit, a main power supply device, and an auxiliary power supply device. The heating unit has a heating element and generates heat by electric power supplied from the main power supply device and the auxiliary power supply device. In the apparatus, there is described a heating device characterized by using a capacitor as an auxiliary power supply device.

[0009]

In the above technique, a heat source for heating the external heating member is required in addition to the heat source for heating the fixing roller. The problem arises. Further, when the power supply from the commercial power supply to the heat source is controlled by the temperature control unit, there is a problem of safety at the time of the heat source runaway which is assumed when the temperature control of the fixing roller surface becomes impossible due to the failure of the temperature control unit. .

The present invention can solve the problem that the temperature of the fixing member surface cannot be prevented from decreasing due to the lack of the capacity of the commercial power supply, and the fixing device and the image are advantageous in terms of safety at the time of runaway of the heat source. It is an object to provide a forming device.

[0011]

According to a first aspect of the present invention, there is provided a fixing device for fixing a toner image formed on a sheet-shaped recording medium.
A fixing member having a first heat source therein; a pressing member disposed to face the fixing member; and a second heat source that generates heat by receiving power supply, and heats the fixing member from outside. An external heating member, and a driving unit for supplying electric power to the second heat source. The driving unit charges the power storage device that can be charged and discharged rapidly and is supplied with power from a commercial power supply. And a charger.

According to a second aspect of the present invention, in the fixing device of the first aspect, the power storage device includes a capacitor having a capacity capable of storing a total energy amount of 1 kJ or more.

The invention according to claim 3 is the invention according to claim 1 or 2
In the fixing device described above, the second heat source is a heater having a heating wire in a glass tube.

According to a fourth aspect of the present invention, in the fixing device according to the third aspect, the color temperature of the heater in a stationary state is 260.
It is 0K or more.

According to a fifth aspect of the present invention, in the fixing device according to the fourth aspect, in the heater, the gas sealed in the glass tube contains krypton or xenon as a main component.

The invention according to claim 6 is the invention according to claim 1 or 2
In the fixing device described above, the second heat source is a planar resistance heating element.

According to a seventh aspect of the present invention, in the fixing device according to any one of the first to sixth aspects, the external heating member is a rotating body.

The invention according to claim 8 is the fixing device according to claim 7, wherein the rotating body is an endless belt.

According to a ninth aspect of the present invention, in the fixing device according to any one of the first to eighth aspects, the fixing member is an endless belt.

According to a tenth aspect of the present invention, in the fixing device according to the ninth aspect, the endless belt as the fixing member is bridged between a heating member and a support member, and the heating member is separated from the fixing nip to the upstream side. It is arranged at the position.

The invention according to claim 11 is the invention according to claims 1 to 11
The fixing device according to any one of the above, wherein the first heat source is a planar heating resistor.

According to a twelfth aspect of the present invention, in the fixing device according to the eleventh aspect, the heating member is fixed and slides at a contact portion with the endless belt to be bridged to heat the endless belt. Is what you do.

According to a thirteenth aspect of the present invention, in the fixing device according to the twelfth aspect, the heating member is formed of a curved thin plate having a substantially arc-shaped cross section.

According to a fourteenth aspect of the present invention, there is provided an image forming apparatus in which a toner image is formed on a sheet-shaped recording medium and the toner image on the recording medium is fixed by a fixing device. 13 is a fixing device according to any one of 13.

[0025]

FIG. 9 shows a first embodiment of the present invention. The first embodiment is an example of an image forming apparatus.
A charging unit 1 is provided around a drum-shaped photosensitive member 101 as an image carrier which is rotated in a direction indicated by an arrow by a driving unit (not shown).
02, cleaning means 103, developing sleeve 105 as developing means for visualizing an electrostatic latent image on photoconductor 101
, And a transfer unit 106 are disposed.

After the photosensitive member 101 is uniformly charged by the charging means 102, it is exposed to laser light L from a laser optical system 140 as a writing means (exposure means) to form an electrostatic latent image. The electrostatic latent image is developed by 107 to become a toner image. The toner image on the photoconductor 101 is transferred to a sheet P as a sheet-shaped recording medium by a transfer unit 106 as described later, and the photoconductor 101 is cleaned by a cleaning unit 103 after the transfer of the toner image. Therefore, the charging means 102 and the laser optical system 14
The developing unit 107, the transfer unit 106, and the image forming unit 107 form a toner image on the sheet P.

At the lower part of the apparatus, there is provided a paper feeder having a paper feed cassette 110 which can be attached and detached in the direction of arrow a.
The sheet P accommodated in the sheet cassette 110 is the middle plate 11
1 and is pressed against the paper feed roller 113 via the arm 112 by the force of a spring (not shown). The uppermost sheet in the sheet feed cassette 110 is fed by a rotation of the sheet feed roller 113 in response to a command from a control unit (not shown), and while the double feed is prevented by the separation pad 114, the registration roller pair 115 on the downstream side Transported to

A paper feed tray 132 is rotatably mounted by a pin 133, and the uppermost sheet-shaped recording medium in the paper feed tray 132 is fed by a paper feed roller and fed by a separation pad. Is transported to the pair of registration rollers 115 on the downstream side while preventing the occurrence of the rotation. One of the sheets in the sheet cassettes 110 and 132 is selectively fed.

The registration roller pair 115 sends the conveyed sheet P to the transfer means 106 at a timing synchronized with the image (toner image) on the photoreceptor 101. The transfer unit 106 transfers the image on the photoconductor 101 to the paper P sent from the pair of registration rollers 115,
The sheet P on which the image has been transferred is conveyed to the fixing device 116. The fixing device 116 fixes the toner on the sheet P to the sheet P by applying heat and pressure.

The sheet P having been fixed from the fixing device 116
Are discharged onto a paper discharge tray 122 from a paper discharge port 121 by a paper discharge roller pair 120 and stacked. In order to correspond to the size of the paper to be discharged, the paper discharge auxiliary tray 125 is slidable in the direction of arrow b. An operation surface is disposed on the right side of the apparatus, and an operation panel 130 protrudes from the upper front surface of the exterior unit 131 (the upper right side of the apparatus in FIG. 9). Case 1 arranged on the left side in the figure
In 34, electrical equipment and control devices such as a power supply circuit 135 and a printed board 136 (engine driver board) are housed, and a controller board 137 is also housed. The cover 138 constituting the paper discharge tray 122 has a rotation fulcrum 1.
39 can be released.

FIG. 2 shows a fixing device 11 according to the first embodiment.
6 is shown schematically. In the fixing device 116, a pressing roller 2 as a pressing member made of an elastic member such as silicon rubber is pressed against a fixing roller 1 as a heating member and a fixing member with a constant pressing force by a pressing unit (not shown). I have.
Since the fixing member and the pressure member are generally rollers, they are shown in FIG. 2 as rollers 1 and 2. However, one or both of the rollers are not limited to the rollers but may be formed by using an endless belt or the like. Is also good.

An external heating member 3 is brought into contact with the surface of the fixing roller 1 at a predetermined pressure.
Is externally heated. When the external heating member 3 is, for example, a roller for external heating which is a rotating body, the contact with the fixing roller 1 is stabilized without sliding on the contact surface with the fixing roller 1.

The fixing device 116 has a main heater 4 and a sub-heater 5 as heat sources that generate heat when supplied with electric power. The main heater 4 is disposed inside (inside) the fixing roller 1 so that the fixing roller 1 Heat from inside. The sub-heater 5 is disposed inside the external heating roller 3 and heats the external heating roller 3 from the inside.

The fixing roller 1 and the pressure roller 2 are driven to rotate by a driving mechanism (not shown). The temperature sensor 6 is in contact with the surface of the fixing roller 1 (or the pressure roller 2), and detects the surface temperature (fixing temperature) of the fixing roller 1 (or the surface temperature of the pressure roller 2). The sheet 8 (the sheet P) as a sheet-shaped recording medium carrying the toner 7 is
When passing through the fixing nip portion between the fixing roller 1 and the pressure roller 2, the toner 7 is fixed by heating and pressing by the fixing roller 1 and the pressure roller 2.

As the main heater 4 as a heat source for heating the fixing roller 1 from the inside, a heater (generally a halogen heater) having a heating wire in a glass tube is used. In the present embodiment, a heater (generally, a halogen heater) having a heating wire in a glass tube is similarly used for the sub-heater 5 in consideration of reliability. In addition, by setting the steady-state color temperature of the heaters 4 and 5 to 2600 K or more, the rising speed can be increased. The heaters 4 and 5 use a halogen heater whose main component is krypton or xenon as a gas sealed in the glass tube, so that the life can be extended and the responsiveness as a heat source can be further improved.

FIG. 1 shows a fixing device 11 according to the first embodiment.
6 shows the block configuration of FIG. A detection signal from the temperature sensor 6 is taken into a CPU 10 as a control means via an input circuit 9, and the CPU 10 changes the surface temperature (fixing temperature) of the fixing roller 1 based on the detection signal from the temperature sensor 6 to a set temperature (set value). ), The switch 11 is controlled to control the power supply from the commercial power supply 12 to the main heater 4, and the switch 13 is controlled to control the power supply from the power storage device 14 to the sub-heater 5.

Here, the main heater 4 is energized from the commercial power supply 12 via the switch 11, and the switch 11
The power supply from the commercial power supply 12 to the main heater 4 is controlled by being controlled by U10. The switch 13 switches the power storage device 14 to the charger 15 and the sub-heater 5, and the switch 13 switches the power storage device 14 to the charger 15 so that the charger 15 converts AC power from the commercial power supply 12 to DC power. And applied to the power storage device 14
To charge.

When the switch 13 switches and connects the power storage device 14 to the sub-heater 5, the power is discharged from the power storage device 14 to the sub-heater 5 via the switch 13. The CPU 10 controls the power supply from the power storage device 14 to the sub-heater 5 by controlling the switch 13. The power storage device 14 is capable of rapid charging and discharging (the cycle of charging and discharging is performed by the recording medium 8).
A storage device, for example, a capacitor having a capacity capable of storing a total energy amount of 1 kJ or more is used.

When the surface temperature of the fixing roller 1 does not fall below the set value, the switch 13 switches the power storage device 14 to the charger 15.
And the charger 15 converts the AC power from the commercial power supply 12 into DC power and applies the DC power to the power storage device 14 to charge the power storage device 14. When the surface temperature of the fixing roller 1 falls below the set value, the switch 13 switches and connects the power storage device 14 to the sub-heater 5, the power storage device 14 discharges the power to the sub-heater 5, and the sub-heater 5 is driven by a direct current.

According to the fixing device 116 of the first embodiment, the fixing roller 1 as a fixing member having the main heater 4 therein as the first heat source, and the heating roller disposed opposite to the fixing roller 1 are disposed. A pressure roller 2 as a pressure member;
An external heating member 3 that has a sub-heater 5 as a second heat source that generates heat when supplied with electric power and heats the fixing roller 1 from outside, and a driving unit that supplies electric power to the sub-heater 5 The means includes a power storage device 14 capable of rapid charging and discharging, and a charger 15 that is supplied with power from the commercial power supply 12 and charges the power storage device 14, so that the capacity of the commercial power supply is insufficient and the temperature of the fixing member surface decreases. Can be prevented, and this is advantageous in terms of safety in the event of a runaway heat source.

That is, by providing the power storage device 14 as a power supply source to the sub-heater 5 that heats the external heating member 3, power exceeding the power supply limit from the commercial power supply is temporarily supplied when the temperature of the surface of the fixing roller 1 decreases. Thus, it is possible to avoid a problem that the temperature of the fixing roller surface cannot be prevented from decreasing due to a shortage of the capacity of the commercial power supply. This also makes it possible to stabilize the gloss of the toner image on the recording medium 8 and reduce its unevenness. Further, power is supplied from the power storage device 14 to the sub-heater 5 that heats the external heating member 3. The climb is not accelerated, which is advantageous in terms of safety.

Further, one recording medium 8 is fixed to the fixing device 116.
The external heating member 3 is repeatedly turned on and off while passing through the power storage device. Therefore, the power storage device 14 that supplies power to the sub-heater 5 that heats the external heating member 3 has a charging / discharging cycle sufficient for the linear velocity. It must follow.
According to the fixing device 116 of the first embodiment, the power storage device 14
By using a large-capacity capacitor whose charge / discharge cycle is faster than that of a storage battery, that is, a capacitor having a capacity capable of storing a total energy amount of 1 kJ or more,
The charge / discharge cycle can sufficiently follow the linear speed, and the present invention can be applied to a fixing device having a high linear speed.

Further, according to the fixing device 116 of the first embodiment, the radiation source having the heating wire in the mosquito tube, which is most frequently used in the past, is used as the heat source 5, so that the cost can be suppressed and the reliability can be improved. Is obtained. The reliability of the heat source 5 is highest when a halogen heater is used.

It takes 1-2 seconds for the radiant heater to reach 90% of the output after the filament is turned on. This is the rising time of the filament itself until the temperature of the filament rises, and the temperature rise of the fixing member is delayed by that much. The rising time of the filament of the halogen heater itself increases as the heat capacity of the filament increases. In short, the larger the filament diameter and the longer the length of the filament, the larger the heat capacity of the filament and the longer the rise time of the filament itself.

The radiant heater is generally used in most fixing devices because of its low cost, high safety, and long service life. However, in order to use a power storage device (capacitor) 14 that can charge and discharge quickly and allow a large current to flow in a short time as a device of a power supply power supply to the external heating member 3 requiring high responsiveness, the rise time is increased. If it is not early, the effect cannot be fully exhibited.

Since the power supply from the power storage device 14 is for a short time during a fixed discharge, the longer the response of the heat source 5 itself or the rise as the external heating member 3 is, the larger the proportion of energy loss is. Would.
In addition, since the external heating member 3 repeats heating and non-heating of the fixing member 1 while one recording medium 8 passes through the fixing device 116, heat supply to the fixing member 1 is efficiently performed. For this purpose, it is necessary to reduce the heat loss at the time of rising as much as possible.

In the fixing device 116 according to the first embodiment, the sub-heater 5 reduces the heat capacity and increases the steady-state color temperature to 26.
By increasing the temperature to 00K or more, the rise time of the filament itself can be shortened, the responsiveness as a heat source can be increased, and the external heating member 3 can be quickly heated.

The radiant heater has a problem that the life is shortened because the diameter of the radiant heater rises faster due to the lower heat capacity of the filament. On the other hand, when light emitted from the filament of the radiation heater passes through the glass tube, a part of the light is absorbed by the glass tube, and the temperature of the glass tube rises. This results in heat loss of the heater. Conventionally, the heat loss in the glass part of the radiation heater is 5% of the total radiation.
%, Which is a loss in the steady state where the temperature of the radiant heater is stable, and the loss of the glass part of the radiant heater at the time of startup of a high-speed rising type fixing device using a fixing member having a small heat capacity. Is newly found to be several times that from the experimental results.

In the fixing device 116 of the first embodiment, the gas sealed in the glass tube of the sub-heater 5 is polymerized with krypton or xenon as a main component, thereby suppressing evaporation of the filament and extending the life. it can. In addition, the gas in the glass tube is polymerized to suppress heat loss due to gas convection in the glass tube, to reduce the cooling of the filament by the gas at startup, and to make the startup of the external heating member 3 faster. Can be.

As a method of heating the fixing member from the outside by the external heating member, a non-contact type in which the external heating member is not in contact with the fixing member and a contact type in which the external heating member is in contact with the fixing member can be considered. In the non-contact type, there is a problem that the heat transfer efficiency between the fixing member and the external heating member is reduced.
In the contact type, when the external heating member is fixed, there is a problem that sliding occurs between the external heating member and the fixing member, thereby causing damage to the fixing member.

In the fixing device 116 of the first embodiment, since the external heating member 3 is a rotating body, the fixing member may be damaged by frictional sliding at a contact portion between the fixing member and the external heating member. Can solve the problem.

FIG. 3 schematically shows a second embodiment of the present invention. In the second embodiment, the endless belt 3a is used as the external heating member 3 in the first embodiment, and the endless belt 3a is wrapped around the rollers 16 and 17, and is fixed to the fixing roller 1 between the rollers 16 and 17. The left part is abutted. The sub heater 5 disposed in the roller 16 is a roller 1
6, the endless belt 3a is heated, and the endless belt 3a heats the fixing roller 1 while rotating in the direction of the arrow. In the fixing device of the second embodiment, since the contact area between the fixing roller 1 and the endless belt 3a is large, the contact area between the fixing roller 1 and the endless belt 3a can be sufficiently secured, and the surface of the fixing roller 1 can be secured. Can be heated more efficiently.

FIG. 4 shows a part of a fixing device according to a third embodiment of the present invention. In the third embodiment, a planar resistance heating element 5a is used as the sub-heater 5 for heating the external heating member 3 which is in contact with the fixing roller 1 in the first embodiment. The resistance heating element 5a is provided integrally inside the fixing roller 1 via an electric insulating layer 18.
The resistance heating element 5a is connected to the power storage device 1 by a power supply unit (not shown).
Power is supplied to the fixing roller 1 from the fixing roller 1 through the switch 13 and heat is generated. On the surface of the external heating member 3 on the side in contact with the fixing roller 1, a surface layer 19 for reducing frictional resistance of contact and reducing frictional scratches is laminated. The surface layer 19 is preferably made of Teflon or the like having excellent heat resistance and durability.

The external heating member 3 is a roller as a rotating body in FIG. 4, but as shown in FIG.
b may be used. In this case, the electric insulation layer 18 and the resistance heating element 5a are also formed in a plate shape, and the resistance heating element 5a is provided integrally with the outside of the external heating member 3b via the electric insulation layer 18.

Since the external heating member 3 repeatedly heats and non-heats the fixing roller 1 while one recording medium 8 passes through the fixing device 116, heat is supplied from the external heating member 3 to the fixing roller 1. Needs to be done efficiently. For this purpose, high responsiveness of the sub-heater 5 is required, and it is advantageous to use a planar resistance heating element for directly heating the fixing roller 1 as the sub-heater 5.

In the fixing device of the third embodiment, the sub-heater 5 uses the sheet-like resistance heating element 5a to heat the external heating member 3b via the electric insulating layer 18 with the resistance heating element 5a. Is advantageous for efficient heat supply, and the manufacturing cost can be reduced. Further, the sub-heater 5 can sufficiently follow the fixing device having a high linear velocity by using the resistive heating element 5a having high response.

When a commercial AC power supply is used as the power supply power supply for the heating resistor, it is necessary to increase the resistance of the heating resistor to some extent, and for that purpose, a complicated energization pattern must be designed. However, in the third embodiment, since the heating resistor 5a is driven by the DC low voltage from the power storage device 14, there is no need to increase the resistance of the heating resistor 5a.
The energization pattern can be prevented from becoming complicated.

FIG. 6 schematically shows a fixing device according to a fourth embodiment of the present invention. In the fourth embodiment, in the first embodiment, the fixing device 116 includes a fixing roller 20 also serving as a driving roller and a heating roller 21 serving as a heating member.
And a pressure roller 22 as a pressure member, an endless belt 23 as a fixing member, a main heater 4 and a sub-heater 5 as heat sources, and an external heating member 3. It is wrapped around the heating roller 21. The main heater 4 and the sub-heater 5 are the same as in the first embodiment, and the energization is controlled by the circuit shown in FIG. 1 as in the first embodiment.

The external heating member 3 is brought into contact with the endless belt 23 on the heating roller 21 at a predetermined pressure.
Heats the endless belt 23 from outside. External heating member 3
Is an external heating roller which is a rotating body, for example. The main heater 4 is disposed inside (inside) the heating roller 21 to heat the heating roller 21, and the heating roller 21 heats the endless belt 23. The sub-heater 5 is a roller 3 for external heating.
And heats the external heating roller 3 from the inside.

The temperature sensor 6 is in contact with the endless belt 23 on the heating roller 21 and detects the surface temperature (fixing temperature) of the endless belt 23. The sheet 8 as a sheet-shaped recording medium carrying the toner 7 includes an endless belt 23 and a pressure roller 2.
2, the toner 7 is fixed by heating and pressing at a fixing nip portion between the fixing roller 20 and the pressure roller 22.

As the base of the endless belt 23, an endless belt-like base made of a heat-resistant resin or metal is used. Polyimide, polyamideide, polyetherketone (PEEK) or the like is used as the heat-resistant resin, and nickel, aluminum, iron, or the like is used as the metal. The thickness of the base of the endless belt 23 is desirably 100 μm or less.

Since the surface of the endless belt 23 comes into contact with the sheet-shaped recording medium 8 and the toner 7 in a pressurized state, a release layer is required, and those having excellent heat resistance and durability are preferable. Therefore, the surface layer of the endless belt 23 is formed of a heat-resistant release layer (such as a fluororesin or a high-release silicone rubber) and is formed on the base of the endless belt 23. The fluorine-based resin is applied to the surface of the base of the endless belt 23 by spraying or the like, and is heated and fused to form a surface release layer. The high release silicone rubber has a rubber hardness of 25 to 6
5 degrees (JIS A hardness tester) and a thickness in the range of 100 to 300 μm are desirable as conditions for obtaining good fixing properties and responsiveness.

The fixing roller 20 has a cored bar, and a heat insulating elastic member made of a soft heat-resistant material, for example, foamed silicon rubber or the like in order to make the fixing nip width sufficiently large on the outer periphery thereof. ing. The heat-insulating elastic member has a sufficient thickness, in this embodiment, about 15% to 20% of the diameter of the fixing roller 20. Pressure roller 22
Has a heat-resistant release layer (fluorine resin, high release silicone rubber, etc.) on the surface of a core metal such as aluminum, stainless steel or carbon steel. In the present embodiment, in order to improve the releasability of the sheet-shaped recording medium 8 from the endless belt 23, the hardness of the pressing roller 22 is made harder than that of the fixing roller 20, and the fixing nip portion is formed upward. Pressure roller 22
The release layer has a thickness of less than 7% of the diameter of the pressure roller 22 and a hardness of 40 Hs or more according to JIS A. The heating roller 21 has a length longer than the width of the paper 8 and is arranged so as to lie in the width direction of the paper 8.

The fixing roller 20 is driven to rotate by a drive unit (not shown), and the endless belt 23 rotates, and the endless belt 2 is rotated.
3 is heated by the heating roller 21 on the upstream side of the fixing nip portion, and when the paper 8 passes between the endless belt 23 and the pressing roller 22, the fixing nip between the fixing roller 20 and the pressing roller 22 is formed. The toner 7 is fixed by heat and pressure in the section.

When the fixing member is a roller, the diameter of the roller must be increased in order to ensure a sufficient fixing nip portion. However, this increases the heat capacity, which is disadvantageous in efficiency. In the fourth embodiment, since the fixing member is the endless belt 23, a wide fixing nip portion can be ensured without excessively increasing the heat capacity, which is advantageous in terms of efficiency.

In the fourth embodiment, the endless belt 23
Is stretched over a heating roller 21 as a heating member and a fixing roller 20 as a support member, and since the heating roller 21 is arranged at a position away from the fixing nip portion on the upstream side, before the endless belt reaches the fixing nip portion. The heating can be performed by the heating roller. Further, the endless belt can be wound around the heating roller, and the contact area between the endless belt and the heating roller can be increased.

FIG. 7 shows a part of a fixing device according to a fifth embodiment of the present invention. In the fifth embodiment, a planar resistance heating element 4a is used as the main heater 4 in the fourth embodiment. The resistance heating element 4 a is integrally supported inside the heating roller 21 via an electric insulating layer 24. The resistance heating element 4a is heated by a power supply unit (not shown) from the commercial power supply 12 via the switch 11, and generates heat.
The heating roller 21 is heated via the electric insulating layer 24. The resistance heating element 4 a is kept insulated from the heating roller 21 by the electric insulating layer 24. The heat distribution which becomes the temperature distribution characteristic of the heating roller 21 can be made desired according to the pattern of the resistance heating element 4a. In the fixing device of the fifth embodiment, since the main heater 4 is a planar resistance heating element 4a, more efficient heat transfer from the resistance heating element 4a to the heating roller 21 is possible.

FIG. 8 shows a part of a fixing device according to a sixth embodiment of the present invention. In the sixth embodiment, in the fifth embodiment, the heating roller 21 is a substantially semi-cylindrical heating member 25 made of a curved thin plate having a substantially arc-shaped cross section, and the resistance heating element 4a and the electric insulating layer are formed. Reference numeral 24 denotes a curved (substantially semi-cylindrical) resistance heating element 26 having a substantially arc-shaped cross section.
And the electrical insulating layer 27. The heating member 25 has a length longer than the width of the sheet-shaped recording medium 8, is disposed so as to lie in the width direction of the recording medium 8, and is fixed to a base (not shown). Therefore, the heating member 25 cannot rotate, and the endless belt 23 is heated by the heating member 25 while sliding in contact with the heating member 25. On the surface of the heating member 25 on the side where the endless belt 23 slides, a surface layer 25a for reducing frictional resistance of the sliding is laminated. Surface layer 25
a is desirably made of a material having excellent heat resistance and durability, such as Teflon (registered trademark).

The heating member 25 is a thin-walled substrate having a substantially semicircular arc shape when viewed in the axial direction, and a substantially circular arc shape obtained by dividing a metal cylinder of aluminum, stainless steel or the like in the longitudinal direction. The heating member 25 can reduce the contact resistance with the endless belt 23 by forming at least the contact surface with the endless belt 23 into a curved shape. The length of the arc of the heating member 25 is determined by the length of the contact surface that contacts the endless belt 23.

Generally, when the heating member is a rotating body such as a roller that rotates with the endless belt, power is supplied to the heat source for heating the heating member by sliding the terminal portion in contact with the metal brush in the circumferential direction. Although a method in which the contact is performed by moving the power supply unit is adopted, such contact sliding in the power supply unit is inevitable due to the configuration. However, since both the metal brush and the terminal part are worn, abrasion powder and roughening of the sliding surface are generated, which leads to an early life of the brush part, generation of noise due to spark discharge, etc., and lowers the reliability of the machine. I have.

In the sixth embodiment, the heating member 25 is fixed and slides at the contact portion with the endless belt 23 to be bridged and heats and heats the endless belt 23. As a result, the early life of the brush portion due to abrasion powder and roughening of the sliding surface and generation of noise due to spark discharge are eliminated.

Generally, a cylindrical metal base is used as the heating member. However, when the heating member is fixed, since the heating member does not rotate, the portion in contact with the endless belt is always constant. The heat generated in the non-contact portion is not efficiently transferred to the endless belt. However, in the sixth embodiment, since the heating member 25 is formed of a curved thin plate having a substantially arc-shaped cross section, it is possible to efficiently transfer heat from the heating member to the endless belt, and to reduce the amount of heat for energy saving. Can be achieved.

In the first to sixth embodiments, since the fixing device is provided, the gloss of the image on the recording medium can be stabilized and the unevenness can be reduced.

[0074]

As described above, according to the first aspect of the present invention, it is possible to solve the problem that the capacity of the commercial power supply is insufficient and it is impossible to prevent the temperature of the fixing member from lowering.
This is advantageous in terms of safety during runaway of the heat source. According to the second aspect of the invention, the charge / discharge cycle of the power storage device can sufficiently follow the linear speed of the fixing device, and the invention can be applied to a fixing device having a high linear speed.

According to the third aspect of the present invention, the effects of suppressing costs and increasing reliability can be obtained. According to the invention of claim 4, the rising time of the filament itself can be shortened, the responsiveness of the heat source can be increased, and the external heating member can be quickly heated. According to the invention according to claim 5, the heater can suppress the evaporation of the filament and extend the life, suppress the heat loss due to gas convection in the glass tube, and reduce the cooling of the filament by the gas at the time of startup. The rise of the external heating member can be made faster.

According to the sixth aspect of the invention, it is advantageous for efficient heat supply to the fixing member, and the manufacturing cost can be reduced. Further, it is possible to sufficiently follow the fixing device having a high linear velocity, and it is possible to avoid complication of the energization pattern of the heat source. According to the invention according to claim 7, it is possible to solve the problem that the fixing member is damaged by frictional sliding at the contact portion between the fixing member and the external heating member.

According to the eighth aspect of the present invention, a sufficient contact area between the fixing member and the external heating member can be ensured, and the surface of the fixing member can be more efficiently heated. According to the ninth aspect, a wide fixing nip portion can be secured without increasing the heat capacity so much, which is advantageous in terms of efficiency. According to the tenth aspect, the endless belt can be heated by the heating member before reaching the fixing nip. Further, the endless belt can be wound around the heating member, and the contact area between the endless belt and the heating member can be increased.

According to the eleventh aspect, more efficient heat transfer from the resistance heating element to the heating member can be achieved. According to the twelfth aspect of the present invention, the contact sliding in the power supply section is eliminated, and the early life of the brush section due to abrasion powder and roughened sliding surface and the generation of noise due to spark discharge are eliminated.

According to the thirteenth aspect, heat can be efficiently transferred from the heating member to the endless belt, and the amount of heat can be reduced for energy saving. According to the fourteenth aspect, it is possible to stabilize the gloss of an image on a recording medium and reduce unevenness thereof.

[Brief description of the drawings]

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

FIG. 2 is a cross-sectional view schematically illustrating a fixing device according to the first embodiment.

FIG. 3 is a sectional view schematically showing a second embodiment of the present invention.

FIG. 4 is a sectional view showing a part of a fixing device according to a third embodiment of the present invention.

FIG. 5 is a sectional view showing a part of a fixing device according to another embodiment of the present invention.

FIG. 6 is a sectional view schematically showing a fixing device according to a fourth embodiment of the present invention.

FIG. 7 is a sectional view showing a part of a fixing device according to a fifth embodiment of the present invention.

FIG. 8 is a sectional view showing a part of a fixing device according to a sixth embodiment of the present invention.

FIG. 9 is a cross-sectional view schematically showing the first embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 20 Fixing roller 2, 22 Pressure roller 3 External heating member 3a, 23 Endless belt 4 Main heater 5a, 4a, 26 Resistance heating element 5 Sub heater 6 Temperature sensor 10 CPU 11, 13 Switch 12 Commercial power supply 14 Power storage device 15 Charging Containers 18, 24, 27 Electrical insulating layer 21 Heating roller 25 Heating member

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takashi Fujita 1-3-6 Nakamagome, Ota-ku, Tokyo, Ricoh Co., Ltd. (72) Inventor Hirokazu Ikegami 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (72) Inventor Takashi Kikuchi 1-3-6 Nakamagome, Ota-ku, Tokyo ・ Ricoh Co., Ltd. (72) Shigeo Kurodaka 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (72) Inventor Kiyoshi Oshima 1-3-6 Nakamagome, Ota-ku, Tokyo ・ Ricoh Co., Ltd. (72) Jun Inventor 1-3-6 Nakamagome, Ota-ku, Tokyo, Stock Company Ricoh F-term (reference) 2H033 AA42 BA11 BA25 BA26 BA30 BB01 BB18 BB21 BB23 BB28 CA07 CA27 CA45 3K058 AA45 AA72 AA73 BA18 CA12 CA23 CB22 CD04 CE17 CE23 CE29 DA02

Claims (14)

[Claims] A fixing device for fixing a toner image formed on a sheet-shaped recording medium, comprising: a fixing member having a first heat source therein; and a pressing member disposed to face the fixing member. An external heating member having a second heat source that generates heat when supplied with electric power, and externally heating the fixing member; and a driving unit that supplies electric power to the second heat source. Is a fixing device comprising: a power storage device capable of rapidly charging and discharging; and a charger that is supplied with power from a commercial power supply and charges the power storage device. 2. The fixing device according to claim 1, further comprising a capacitor having a capacity capable of storing a total energy amount of 1 kJ or more as said power storage device. 3. The fixing device according to claim 1, wherein the second heat source is a heater having a heating wire in a glass tube. 4. The fixing device according to claim 3, wherein the steady-state color temperature of the heater is 2600 K or more. 5. The fixing device according to claim 4, wherein the gas contained in the heater in the glass tube contains krypton or xenon as a main component. 6. A fixing device according to claim 1, wherein said second heat source is a sheet-like resistance heating element. 7. The fixing device according to claim 1, wherein the external heating member is a rotating body. 8. A fixing device according to claim 7, wherein said rotating body is an endless belt. 9. A fixing device according to claim 1, wherein said fixing member is an endless belt. 10. The fixing device according to claim 9, wherein the endless belt serving as the fixing member extends over a heating member and a supporting member, and the heating member is disposed at a position away from the fixing nip portion on the upstream side. Characteristic fixing device. 11. The fixing device according to claim 1, wherein the first heat source is a planar heating resistor. 12. The fixing device according to claim 11, wherein the heating member is fixed, slides at a contact portion with the endless belt to be bridged, and heats and heats the endless belt. Fixing device. 13. A fixing device according to claim 12, wherein said heating member is formed of a curved thin plate having a substantially arc-shaped cross section. 14. An image forming apparatus for forming a toner image on a sheet-like recording medium and fixing the toner image on the recording medium by a fixing device, wherein the fixing device is provided.
An image forming apparatus, wherein the image forming apparatus is the fixing device according to any one of claims 13 to 13.