JP2001235964A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a proper temperature without bringing a temperature detecting means into contact with the surface of a fixing roller, and to obtain a good toner fixed image. SOLUTION: A fixing roller 3,4,5,6, a pressure roller 8,9,10, a coil 1 for heating by applying an alternating magnetic field while maintaining a constant gap to the fixing roller, a temperature of the fixing roller. In the induction heating fixing apparatus, the temperature detecting means 7 is provided with a temperature detecting means 7 for detecting, and a control means for controlling the temperature of the fixing roller by flowing an alternating current to the coil and controlling the alternating current based on the detected temperature. It is arranged near the eddy current generating position at the end of the roller, so that an appropriate temperature can be detected at a position in consideration of the generation distribution of the eddy current generated in the heating layer 5 of the fixing roller. The fixing roller comprises a cored bar 3, an elastic layer 4, a conductive heating layer 5 and a release layer 6, and a temperature detecting means 7 is located near an eddy current generating position at an end of the fixing roller and heats the fixing roller. It is arranged on the inner circumference of the layer.

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 a printer, and more particularly to a fixing device for an electrophotographic printer and a fixing device for drying a solvent of an ink jet printer.

[0002]

2. Description of the Related Art FIG. 4 shows an example of a conventional fixing device using a halogen lamp as a heating source.
Reference numeral 22 denotes a pressure roller, 23 denotes a halogen lamp, 24 denotes a toner image, 25 denotes a recording sheet, 27 denotes a spring, and 28 denotes a temperature detecting means.

[0003] As a fixing device of a printer, there are a fixing device using a halogen lamp as a heat source and a fixing device using an electromagnetic induction heating device as a heat source. In a conventional fixing device using a halogen lamp as a heat source, a substantially cylindrical halogen lamp 23 is disposed at the center of a hollow fixing roller 21 as shown in FIG. The main electromagnetic wave is radiated and reaches the inside of the fixing roller 21 to be converted into heat. The heat is transmitted to the outside of the fixing roller 21, and the recording paper 25 having the marking material (toner image 24) sandwiched between the fixing roller 21 and the pressure roller 22 is moved by a spring 27.
The marking material 24 is fixed by heating while pressing. The temperature of the fixing roller 21 is controlled by detecting the temperature outside the fixing roller 21 by the temperature detecting unit 28 and controlling the current of the halogen lamp 23 based on the detected temperature by the control circuit.

On the other hand, various proposals have been made for a conventional fixing device using an electromagnetic induction heating device as a heat source, for example, a device in which the temperature detecting means is made of metal (see JP-A-8-6413), a sound sensor. The member generates induced heat (Japanese Patent Laid-Open No. 9-1
Japanese Patent Application Laid-Open No. Hei 9-197852), which uses a sound-sensitive member that also generates heat to prevent excessive temperature rise.
Japanese Patent Application Laid-Open No. 9-305045), a non-magnetic field space provided in a nip portion and a temperature detecting member provided therein (see Japanese Patent Application Laid-Open No. 9-305045). Providing means (Japanese Patent Laid-Open No. 10-691)
No. 87).

[0005]

However, in the case of the conventional fixing device using a halogen lamp as a heat source as shown in FIG. 4, since the halogen lamp 23 is disposed inside the fixing roller 21, Temperature detection means 2 inside
8 is provided, the temperature detecting means 28
Therefore, it is difficult to accurately detect the temperature of the fixing roller 21 because the electromagnetic wave is blocked. Therefore, the temperature detecting means 28 is attached to the outer periphery of the fixing roller 21 as shown in the figure, but as a result, a sliding mark is left on the surface of the fixing roller 21 and the mark appears on the fixed image. There is a problem that it leads to image deterioration.

[0006] Even in the case of a conventional fixing device using an electromagnetic induction heating device as a heat source, in a fixing device which uses a metal as a temperature detecting means and detects a temperature heated by heat generated by eddy current generated in the metal, it is necessary to provide a special feature. JP-A-8-6413, JP-A-9-197851, JP-A-9-197
No. 852), it is necessary to have a certain area continuous for the generation of eddy current, and eddy current will not be generated unless the temperature detecting means is thick and large to some extent, so that the temperature detecting means becomes large and the heat capacity becomes large. As a result, there has been a problem that the thermal response becomes slow. Further, there is no guarantee that the temperature of the temperature detecting means is equal to the temperature of the fixing roller or the fixing film, and there is a problem that it is difficult to detect an appropriate temperature.

Further, in a fixing device in which a non-magnetic field space is provided in a nip portion and a temperature detecting member is provided therein (Japanese Patent Laid-Open No. 9-3)
No. 05045), a non-magnetic field space is created by using a fixing film having a small heat capacity, and a temperature detecting means is provided therein, so that an eddy current is not generated in the space and an appropriate fixing temperature cannot be detected. In other words, the position where the fixing temperature is detected is only heated by the heat transmitted from the place where the eddy current is generated, and when the heat capacity is small like a fixing film, heat is applied to the recording paper or toner. Because it is immediately deprived, temperature detection becomes difficult.

In a fixing device provided with a temperature detecting means at a position where the induced current becomes dense inside the fixing sleeve (Japanese Patent Laid-Open No.
JP-A-69187), since the fixing sleeve has a flexible property, the temperature detecting means is in stable contact with the upper portion where the eddy current is sparse, but is detected in the portion where the eddy current is dense. It was difficult to stably contact the means, and it was difficult to detect an appropriate temperature.

Further, in the case of a halogen lamp as a heating source, as described above, the fixing roller is hollow and the halogen lamp is disposed therein, so that the temperature at which the temperature of the fixing roller is detected is determined. A sensor and an overheating prevention sensor can be arranged only on the outer periphery of the fixing roller. For this reason, most of the temperature sensors directly contact the outer peripheral surface of the fixing roller using a spring or the like. If the temperature sensor is in direct contact with the surface of the fixing roller as described above, contact marks and scratches are gradually formed on the surface of the fixing roller, and fixing marks and scratches appear on the fixed image. The result was a loss of quality.

[0010]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is possible to detect an appropriate temperature without bringing a temperature detecting means into contact with the surface of a fixing roller. Is what you get.

For this purpose, the present invention provides a fixing roller, a pressure roller, a coil for applying an AC magnetic field to the fixing roller to heat it, temperature detecting means for detecting the temperature of the fixing roller, and applying an AC current to the coil. In an induction heating fixing device having control means for controlling the temperature of the fixing roller by controlling the alternating current based on the detected temperature, the temperature detecting means may be located near an eddy current generating position at an end of the fixing roller. Wherein the temperature detecting means is constituted by a protective layer, a temperature sensor, and a hinge portion, and is disposed so as to come into contact with the inner periphery of the heating layer with a pressurized force. The fixing roller is characterized in that it is spirally wound in the axial direction while maintaining a constant gap outside the fixing roller.

A fixing roller, a pressure roller, a coil for applying an AC magnetic field to the fixing roller to heat the fixing roller, temperature detecting means for detecting a temperature of the fixing roller, and applying an alternating current to the coil to supply the alternating current to the coil. In the induction heating fixing device provided with control means for controlling the temperature of the fixing roller by controlling based on the detected temperature, the fixing roller comprises a core metal, an elastic layer, a conductive heating layer, and a release layer. Wherein the temperature detecting means is disposed near an eddy current generating position at an end of the fixing roller and on an inner periphery of a heating layer of the fixing roller, wherein the temperature detecting means comprises a protective layer, a temperature sensor, , Comprising a hinge portion, disposed so as to pressurized contact with the inner periphery of the heating layer, the coil is axially maintaining a constant gap to the fixing roller outside. It is characterized in that it has arranged wound on the winding form.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a view showing an embodiment of a fixing device according to the present invention, and FIG. 2 is a view for explaining nip formation. In the figure, 1 is a coil, 2 is a coil holder,
Reference numerals 3 and 8 denote a core metal, 4 and 9 an elastic layer, 5 a heating layer, 6, 10
Is a release layer, 7 is a temperature detecting means, 11 and 12 are bearings, 1
3 is a gear, 14 is a lever, 15 is a spring, 16 is a side plate, 1
7 indicates a hole.

In FIG. 1, the fixing roller comprises a metal core 3, an elastic layer 4, a conductive heating layer 5 having a small heat capacity, and a release layer 6. The core 3 is made of carbon steel, stainless steel, etc.
Materials having strength are suitable. For the elastic layer 4, a material having heat resistance and sufficient elasticity to form a nip between the fixing roller and the pressure roller, such as silicon rubber or foamed silicon rubber, is suitable. The heating layer 5 needs to have conductivity so that an eddy current is efficiently generated by the AC magnetic field from the coil 1. The release layer 6 is provided to make the melted toner easy to separate from the fixing roller, and has a purpose of preventing offset.

The material of the release layer 6 is a fluororesin (P
FA, PTFE, PEP), silicone resin, fluorine rubber, silicone rubber, etc. are suitable.
0 μm to several hundred μm are desirable. If it is less than several tens of μm, it is no longer abrasion to the recording paper, and if it is more than several hundreds of μm, the thermal conductivity is reduced and the heat from the heating layer cannot be transmitted efficiently.

The temperature detecting means 7 comprises a protective layer, a temperature sensor, and a hinge portion. The temperature detecting means 7 is supported on the inner periphery of the heating layer 5 with a spring property so that the heating layer 5 can be stably maintained even when the fixing roller rotates. To be able to detect temperature by contacting with pressure. Further, the elastic layer 4 has a structure in which a part of the elastic layer 4 is cut off so that the temperature detecting means 7 is attached to the end of the fixing roller. The opposite end of the temperature detecting means 7 is held by the side plate 16. If the spring property of the temperature detecting means 7 is weak, the temperature detecting means 7 will not stably come into contact with the heating layer 5, and if it is strong, the heating layer 5 will be pushed too much and deformed. Is fine.

The coil 1 is held by a coil holder 2, maintains a constant gap around the outer periphery of the fixing roller, and inductively heats the fixing roller by applying an AC magnetic field. FIG. 1B shows the structure in a top view. In the coil 1, since a high-frequency current flows, it is necessary to reduce the surface resistance and the loss of the coil. Therefore, a litz wire is used in which a plurality of insulated copper wires are bundled and twisted. For example, it is a spirally wound copper wire having a diameter of 0.5 mmφ and used by twisting eight wires. The coil holder 2 also has a function of protecting the recording paper from being in contact with the coil 1 immediately after fixing to prevent damage such as a scratch. The coil holder 2 has a hole 17 and water contained in the recording paper is heated and released, so it is necessary to release the water. Especially when moisture adheres to the coil 1,
This may cause deterioration of the insulation coating on the conductor surface of the coil 1 wound with the litz wire. Furthermore, if there is no hole 17,
If the water accumulates and exceeds a certain amount, it becomes water droplets and drops on the recording paper, and wets the fixed recording paper.

The pressure roller comprises a cored bar 8, an elastic layer 9, and a release layer 10 if necessary. The core metal 8 is the same as that of the fixing roller. The elastic layer 9 is required to have an elasticity that is in proportion to the elasticity of the elastic layer 4 and the heating layer 5 of the fixing roller. A nip is formed by this balance. When the elasticity of the fixing roller is low, the recording paper is bent toward the fixing roller as shown in FIG. 2A, and when the elasticity of the fixing roller is low, the recording paper is pressed as shown in FIG. It will bend to the roller side, which greatly affects the releasability of the recording paper. Further, if the elasticity of the fixing roller and the pressure roller are extremely different from each other and the curvature is large, wrinkles are likely to occur in the case of two types of recording paper such as an envelope. For this reason, it is desirable that the elasticity of the fixing roller and the pressure roller be appropriately balanced and close to a horizontal nip as shown in FIG.

Both ends of the fixing roller and the pressure roller are held on the side plate 16 by bearings 11 and 12. In the case of the fixing roller, a gear 13 is attached for transmitting a rotational torque, and is driven to rotate by a motor via the gear 13. Bearings 12 at both ends of the pressure roller are
, Is pulled toward the fixing roller by the spring 15 to form a nip load. The springs 15 are set so that both have the same load. When the nip load is large, the nip width is large, and when the nip load is small, the nip width is small. The nip width is an important parameter that determines the fixing time, and is determined in relation to the electrophotographic process speed and the thermal properties of the toner. As the nip width increases, the fixing time increases, and as the nip width decreases, the fixing time decreases. However, if the nip load is increased in order to increase the fixing time, the rotational torque tends to increase,
In that case, the motor becomes large and there is a restriction.

FIG. 3 is a diagram for explaining the generation distribution of the eddy current and the mounting position of the temperature detecting means. The fixing roller is heated by generating an eddy current in the conductive heating layer 5 by applying an AC magnetic field from the coil 1 maintaining a certain gap, but the AC magnetic field from the coil 1 is fixed due to a skin effect. It will concentrate mainly near the surface of the roller. If the electrical resistivity is ρ, the magnetic permeability is μ, the frequency of the AC magnetic field is f, and the skin thickness is δ, these relationships are

[0021]

(Equation 1)

## EQU2 ## If the frequency f of the AC magnetic field from the coil 1 is appropriately selected for efficient heating, the magnetic flux from the coil 1 is concentrated near the skin thickness δ, and an eddy current is effectively generated. When the eddy current is generated, Joule heat is generated according to the electric resistivity ρ, and the temperature of the fixing roller increases. When the material is carbon steel, SUS304, SUS430 or the like and the frequency of the AC magnetic field is f = 25 kHz, the skin thickness δ is several tens μm or more.
It becomes several 100 μm. On the other hand, it is important that the heating layer 5 has an appropriate elasticity in order to form an appropriate nip.
Conversely, if it is several hundreds μm or more, elasticity is lost.

As shown in FIG. 1B, for example, when the coil 1 is formed by spirally winding a litz wire in the axial direction of the fixing roller, an eddy current generated in the heating layer 5 by the AC magnetic field. FIG. 3 shows the distribution of.
Since the AC magnetic field from the coil 1 is generated as a magnetic path between the central portion of the coil 1 and the outside thereof, that is, in the heating layer 5 just below the coil 1, the AC magnetic field is viewed from above in FIG. As shown in the eddy current generation distribution and the eddy current generation distribution viewed from the side in FIG. 3B, the eddy current is generated in the axial direction and at both ends. The temperature detecting means 7 attached to the end of the fixing roller is disposed near the eddy current generating position as shown in FIG.

The present invention is not limited to the above embodiment, and various modifications are possible. For example, in the above embodiment, a coil formed by spirally winding a litz wire in the axial direction of the fixing roller is used, but a plurality of coils may be divided and arranged in the axial direction. Further, the gap between the coil and the fixing roller is fixed, but when the coil is divided, the gap may be changed between the end and the center.

[0025]

As is apparent from the above description, according to the present invention, the fixing roller, the pressing roller, and the fixing roller are heated by applying an AC magnetic field while maintaining a constant gap. Temperature detecting means for detecting the temperature of the fixing roller, and a control means for controlling the temperature of the fixing roller by passing an alternating current to the coil and controlling the alternating current based on the detected temperature. Since the fixing roller is disposed near the eddy current generating position at the end of the fixing roller, an appropriate temperature can be detected at a position in consideration of the distribution of eddy current generated in the heating layer of the fixing roller.

The fixing roller comprises a cored bar, an elastic layer, a conductive heating layer and a release layer, and the temperature detecting means is located near the eddy current generating position at the end of the fixing roller and heats the fixing roller. In the electromagnetic induction heating type fixing device in which a thin heating layer is provided and the coil can be disposed outside the layer, since the temperature detecting means is not in contact with the surface of the fixing roller, the heating effect is provided. Can also be placed inside the heating layer without affecting.

Further, the temperature detecting means is composed of a protective layer, a temperature sensor, and a hinge portion, and is disposed so as to come into contact with the inner periphery of the heating layer with pressurization. The present invention can provide a high-quality fixed image without causing deformation of the fixing roller, leaving no trace of the contact of the temperature detecting unit on the toner-fused surface of the recording paper, without causing deformation of the fixing roller. be able to.

[Brief description of the drawings]

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

FIG. 2 is a diagram for explaining nip formation.

FIG. 3 is a diagram for explaining an eddy current generation distribution and a mounting position of a temperature detecting unit.

FIG. 4 is a diagram illustrating an example of a conventional fixing device using a halogen lamp as a heating source.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Coil, 2 ... Coil holder, 3, 8 ... Core metal, 4, 9
... elastic layer, 5 ... heating layer, 6, 10 ... release layer, 7 ... temperature detecting means, 11, 12 ... bearing, 13 ... gear, 14 ... lever, 15 ... spring, 16 ... side plate, 17 ... hole

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H05B 6/14 H05B 6/14

Claims (4)

[Claims] 1. A fixing roller, a pressure roller, a coil for applying an AC magnetic field to the fixing roller to heat the fixing roller, a temperature detecting means for detecting a temperature of the fixing roller, and an AC current flowing through the coil. In the induction heating fixing device provided with control means for controlling the temperature of the fixing roller by controlling the temperature based on the detected temperature, the temperature detecting means is arranged near an eddy current generating position at an end of the fixing roller. A fixing device. 2. A fixing roller, a pressure roller, a coil for applying an AC magnetic field to the fixing roller to heat the fixing roller, a temperature detecting unit for detecting a temperature of the fixing roller, and an AC current flowing through the coil. In the induction heating fixing device provided with control means for controlling the temperature of the fixing roller by controlling based on the detected temperature, the fixing roller comprises a core metal, an elastic layer, a conductive heating layer, and a release layer. The fixing device is characterized in that the temperature detecting means is disposed near an eddy current generating position at an end of the fixing roller and on an inner periphery of a heating layer of the fixing roller. 3. The temperature detecting means comprises a protective layer, a temperature sensor, and a hinge portion, and is arranged so as to contact the inner periphery of the heating layer with a pressurized pressure. 3. The fixing device according to item 2. 4. The fixing device according to claim 1, wherein the coil is arranged so as to be spirally wound in the axial direction while maintaining a constant gap outside the fixing roller. apparatus.