JP2003271002A - Fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make the gloss of a fixed image uniform in a belt fixing system. <P>SOLUTION: The device is provided with several kinds of heat sources for heating a belt, and uses temperature sensors the number of which is greater than the number of the kinds of the heat sources. When the temperature of the belt is controlled based upon a temperature detected by each temperature sensor, control temperatures in the positions of the heat sources are equal. <P>COPYRIGHT: (C)2003,JPO

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 melting and fixing a toner image on a transfer material in an image forming apparatus.

[0002]

2. Description of the Related Art A general image forming apparatus using an electrophotographic system usually uses a transfer material and an electrostatically held toner composed of resin, magnetic material, colorant, etc. It has a fixing device for fusing and fixing by applying heat and pressure while being nipped and conveyed at the pressure contact portion (nip portion) between the pressure roller that is in pressure contact and rotation and the pressure roller. But,
In recent years, in order to increase the output speed of image forming apparatuses, it has become necessary to increase the process speed. Therefore, a wider nip width (nip width) is required, and a belt fixing method that replaces the fixing roller, the pressure roller, or both with an endless belt to secure a wide nip width has been proposed and commercialized. . For example, as shown in FIG. 6, a method has been proposed in which the fixing roller is replaced with a belt, a plurality of metal sleeves having a heat source are provided inside the belt, and the belt is driven by the metal sleeves. ing. According to this method, there is an advantage that a nip width that is about twice that of the roller fixing method of almost the same size can be secured.

[0003]

However, in the belt fixing method as in the above-mentioned conventional example, when the fixing device is stopped while the image forming apparatus is on standby, it comes into contact with the metal sleeve containing the heating source. Temperature unevenness occurs in the circumferential direction of the belt in the presence and absence of the area. When the fixing operation is started in this state, the glossiness (gloss) of the image is different between the image portion fixed by contact with the high temperature belt and the image portion fixed by contact with the low temperature belt. There was a flaw.

Further, since the heat capacity of the belt is small, the heat of the belt is given to the transfer material while passing through the nip portion, and the temperature of the belt is greatly lowered at the exit of the nip portion. If the nip width is set too wide, there is a defect that fixing failure occurs.

An object of the invention according to the present application is to make the image gloss after fixing uniform by always keeping the temperature of the belt of the belt fixing system uniform in the circumferential direction. Further, also in the nip portion, heating of the belt prevents the fixing failure.

[0006]

In order to achieve the above object, the invention according to the present application provides a transfer material by pressurizing and heating in a nip portion formed by a heated endless belt and a pressing member. In the fixing device that fixes the unfixed toner image formed above, there are multiple types of heating sources for heating the endless belt, and the endless belt temperature detection device used to control the endless belt temperature is the heating source. The number of endless belts is equal to or more than a certain number, and the endless belt temperatures detected by the plurality of endless belt temperature detection devices are controlled to be equal to each other at a predetermined target temperature.

In the above structure, there are a plurality of types of heating sources for heating the endless belt, and the number of endless belt temperature detecting devices used for controlling the temperature of the endless belt is equal to or more than the number of heating sources. The means for controlling the endless belt temperatures detected by the temperature detection device so that they are equal to each other at a predetermined target temperature can heat the belt over the entire circumferential direction of the belt, so that the temperature of the belt becomes uniform in the circumferential direction. Acts like Further, since the belt can be heated in the nip as well, it acts to prevent the belt temperature from decreasing in the nip.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG. 1 is a drawing that best shows the features of the present invention, and is a schematic cross-sectional view of a fixing device that is an embodiment of the present invention.

The fixing belt 1 has a diameter of 30 mm, the base is made of Ni by electroforming, and the thickness is 20 to 200 μm.
(Preferably 30 to 100 μm). Further, a silicon rubber layer as an elastic layer is formed on the outer periphery of the Ni base body by 100.
˜1000 μm (preferably 200 to 500 μm), and a layer of fluororesin such as PFA or PTFE as a release layer is 10 to 100 μm (preferably 20 to 100 μm) on the outer periphery thereof.
60 μm) is provided.

The fixing belt winding roller 2 has a diameter of 20 [m].
m] made of Al and has a wall thickness of 4 [mm]. The fixing belt winding roller 3 is an Al sleeve having a diameter of 15 [mm] and a thickness of 1.5 [mm]. Pressure roller 4
Is an iron sleeve having a diameter of 50 [mm] and a thickness of 1 [mm], and a silicon rubber sponge having a thickness of 3 [mm] as an elastic layer is provided on the outer periphery thereof, and the surface layer has a thickness of 50 [mm] as a release layer. A [μm] PFA tube is provided.

The fixing belt winding roller 2 and the fixing belt winding roller 3 respectively have a total pressure of 10 against the pressure roller 4.
It is pressurized with [Kg weight] and 15 [Kg weight]. Also,
The fixing belt winding roller 2 and the fixing belt winding roller 3 are
The fixing belt 1 is driven so that the rotation speed is 170 [mm / sec], and the pressure roller 4 is driven to rotate. Alternatively, the pressure roller 4 may also be driven.

At this time, the width of the nip portion composed of the fixing belt 1 and the pressure roller 4 becomes about 20 [mm].

The fixing belt winding roller 2 and the fixing belt winding roller 3 are provided with halogen lamp heaters 5 and 6 as heating sources, respectively. The halogen lamp heaters 5 and 6 have rated powers of 350 [W] and 150, respectively.
[W], which is on / off controlled to a target temperature of 200 [° C.] based on the temperatures detected by the temperature sensors 8 and 9, respectively.

The exciting coil 7 is arranged along the fixing belt 1, and is appropriately 0 to 1 with an alternating current of 10 to 100 [kHz].
Uses [kW] power. The magnetic field induced by the alternating current causes an eddy current to flow in the Ni conductive layer of the fixing belt 1 to generate Joule heat. It is preferable to cover the exciting coil 7 with an insulator and press the pressing roller 4 against the pressure roller 4 via the fixing belt 1 to further improve the fixing performance.

The temperature sensor 10 is arranged so as to contact the surface of the fixing belt 1, and the surface temperature of the fixing belt 1 is controlled by increasing or decreasing the power supply to the exciting coil 7 based on the detection signal of the temperature sensor 10. The target temperature is 200
It is automatically controlled so that the temperature becomes constant at [℃].

The transport guide 11 is provided with an unfixed toner image T.
The transfer material P, which is carried while carrying, is arranged at a position for guiding the transfer material P to the nip portion between the fixing belt 1 and the pressure roller 4.

FIG. 2 shows the temperature of the fixing belt 1 detected by the temperature sensor 8 from the state in which the image forming apparatus is on standby until the fixing belt 1 starts rotating and makes one revolution.

FIG. 6 shows a fixing device in which the heating source of the conventional example is only a halogen lamp heater, and FIG. 5 similarly shows the fixing device of the conventional example in which the image forming apparatus is in a standby state. The temperature of the fixing belt 1 detected by the temperature sensor 8 from when the belt 1 starts rotating to when it makes one round is shown.

In the configuration of this embodiment, the fixing belt 1 is circumferentially heated at the target temperature of 200 [° C.] by the two heating methods of the halogen lamp heaters 5 and 6 and the exciting coil 7 even when the image forming apparatus is on standby. You can see that it is made evenly across. On the other hand, in the fixing device of the conventional example, since the fixing belt 1 is heated only by the halogen lamp heaters 5 and 6 while the image forming apparatus is on standby, the fixing belt 1 which is not in contact with the fixing belt winding rollers 2 and 3. The part has become cold. Therefore, in the circumferential direction of the fixing belt 1, an uneven temperature distribution as shown in FIG. 5 is obtained, and the gloss of the image after fixing becomes uneven, which is not preferable.

Further, in the fixing device of the conventional example, since the heat is not supplied to the fixing belt 1 at the nip portion, the temperature of the fixing belt 1 is drastically lowered at the nip portion. As a result, when the fixing speed is high, or when fixing thick paper or the like, insufficient heat may cause fixing failure. In the fixing device of the present embodiment, since the fixing belt 1 is heated by the exciting coil 3 also in the nip portion, the temperature drop in the nip portion of the fixing belt 1 is small and the fixing property can be secured.

Although the heat source for the fixing belt is arranged inside the belt in this embodiment, it may be arranged outside the belt. In that case, the temperature sensor can be appropriately selected and arranged inside or outside the belt.

As described above, in the present embodiment, two types of fixing belt heating sources are used, and three fixing belt temperature detecting devices are used to determine the fixing belt temperature at each heating source position. By controlling to be equal, a fixed image having a uniform gloss can be obtained. Further, it becomes possible to fix at a higher speed.

(Second Embodiment) This embodiment is different from the first embodiment in that the sheet heating element 37 is used as the heating source for the fixing belt 1 instead of the induction heating system using an exciting coil. is there. Although it is inferior to the system of Embodiment 1 in terms of high-speed fixing, the system of this embodiment has a wide selection range such as selection of the base layer of the fixing belt and resin such as polyimide. Further, if the sheet heating element 37 is pressed against the pressure roller 4 via the fixing belt 1, the fixing performance may be further improved.

The halogen lamp heaters 35 and 36 are on / off controlled so that the temperatures detected by the temperature sensors 38 and 39 are constant at 200 [° C.] which is the target temperature. The planar heating element 37 is controlled so that the temperature detected by the temperature sensor 30 is constant at a target temperature of 200 [° C.]. The temperature of the fixing belt 1 detected by the temperature sensor 38 from the state in which the image forming apparatus is on standby until the fixing belt 1 starts rotating and makes one revolution is substantially the same as that in FIG. 2 described in the first embodiment. .

As described above, also in this embodiment, as in the first embodiment, two types of fixing belt heating sources are used, and three fixing belt temperature detecting devices are used. By controlling the fixing belt temperature at the heating source position to be equal, a fixed image having a uniform gloss can be obtained.

(Third Embodiment) In this embodiment, as in the first embodiment, the halogen lamp heaters 45 and 46 and the exciting coil 47 are arranged in the pressure belt 41, and the temperature sensors are respectively provided. The target temperature is 170 at 43, 49 and 40
It is controlled to be constant at [° C]. Pressure belt 41
May use the same material as the fixing belt 1 described in the first embodiment.

The fixing roller 42 is φ50 [mm], the base is an aluminum sleeve having a thickness of 3 [mm], and silicon rubber is provided as an elastic layer with a thickness of 2 [mm] on the outer periphery, and the surface layer is separated. A PFA tube having a thickness of 50 μm is provided as a mold layer. Further, a halogen lamp heater 44 is arranged inside as a heating source. The halogen lamp heater 44 uses the output value of the temperature sensor 48 so that the fixing roller 42 reaches a predetermined target temperature.
ON / OFF controlled.

In the configuration of this embodiment, as in the first embodiment, the pressure belt 41 is fixed by the two heating methods of the halogen lamp heaters 45 and 46 and the exciting coil 47 even when the image forming apparatus is on standby. The target temperature can be made uniform in the circumferential direction.

Further, since the pressure belt 41 is heated by the exciting coil 47 in the nip portion, the temperature effect in the nip portion of the pressure belt 41 is small and the fixing property can be improved.

As described above, in the present embodiment, a fixed image having a uniform gloss can be obtained by using the halogen lamp heater and the induction heating system using the exciting coil together as the heating source of the pressure belt. Further, it becomes possible to fix at a high speed.

[0031]

As described above, according to the invention of the present application, a fixed image having uniform gloss can be output at high speed.

[Brief description of drawings]

FIG. 1 is a schematic view of a cross section of a fixing device according to a first embodiment of the present invention.

FIG. 2 shows the fixing belt 1 detected by the temperature sensor 8 from the state in which the image forming apparatus is in a standby state to the fixing belt 1 in the first embodiment of the present invention, from when the fixing belt 1 starts rotating to when the fixing belt 1 makes one round. It is the figure which showed temperature.

FIG. 3 is a schematic cross-sectional view of a fixing device that is a second embodiment of the present invention.

FIG. 4 is a schematic cross-sectional view of a fixing device that is a third embodiment of the present invention.

FIG. 5 shows the temperature of the fixing belt 1 detected by the temperature sensor 8 from the state where the image forming apparatus is on standby to the time when the fixing belt 1 starts to rotate and makes one revolution when the conventional fixing device is used. It is a figure.

FIG. 6 is a schematic view of a cross section of a conventional fixing device.

[Explanation of symbols]

1 fixing belt 2 Fusing belt winding roller 3 Fixing belt winding roller 4 pressure roller 5 Halogen lamp heater 6 Halogen lamp heater 7 Excitation coil

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2H033 AA03 AA10 BA11 BA12 BA25                       BA26 BA32 BB03 BB06 BB28                       BB33 BE06 CA04 CA05 CA07                       CA30 CA32 CA48                 3K058 AA61 AA71 BA18 CA12 CA22                       CA92 CB02 CE31 CE32 DA01                       DA02 DA26 GA03 GA06                 3K059 AA08 AB19 AB28 AC33 AD15                       AD39 CD06 CD73 CD75

Claims (6)

[Claims] 1. A fixing device for fixing an unfixed toner image formed on a transfer material by being pressed and heated in a nip portion formed by a heated endless belt and a pressure member or a fixing member. The fixing device is characterized in that there are a plurality of types of heating sources for heating the endless belt, and the number of endless belt temperature detecting devices used to control the endless belt temperature is equal to or more than the number of heating sources. 2. The fixing device according to claim 1, wherein there are two types of heat sources for heating the endless belt. 3. The fixing device according to claim 1, wherein the endless belt has a base made of magnetic metal. 4. The fixing device according to claim 3, wherein the heating source is a halogen lamp heater and an induction heating coil. 5. The fixing device according to claim 1, wherein the heating source is a halogen lamp heater and a planar heating element. 6. The endless belt temperature, which is used to control the endless belt temperature and is detected by a plurality of endless belt temperature detecting devices, is controlled to be equal to each other at a predetermined target temperature. The fixing device according to any one of claims 1 to 5.