JP2001201964A - Image heating device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electromagnetic induction heating type image heating device and an image forming device capable of realizing quick start by forming plural nip parts for heating an image, obtaining excellent heating performance even in the case of a low nip pressure and making the heat capacity of an induction heating element small. SOLUTION: The electromagnetic induction heating type image heating device is provided with a moving or turning induction heating element 3, an alternating magnetic field generating means 5 for making the heating element 3 perform electromagnetic induction heating and pressure members 14A and 14B forming the nip part N while being in press-contact with the heating element 3. In the image heating device, the image on the recording material is heated by forming plural nip parts N and carrying the recording material P to the plural nip parts N in order.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image heating apparatus and an image forming apparatus of an electromagnetic (magnetic) induction heating system, and more particularly to a fixing apparatus such as a printer, a facsimile, a copying machine, and an image forming apparatus having the same. Things.

[0002]

2. Description of the Related Art For example, in an image forming apparatus such as a copying machine, a printer, a facsimile, or the like, a recording material (transfer material, photosensitive paper, photosensitive paper, An unfixed toner image formed and carried on a paper sheet such as electrostatic recording paper or printing paper in a transfer method (indirect method) or a direct method in accordance with target image information, and is heated and fixed on the surface of the recording material. As an image heating fixing device as an image heating device for (hereinafter, referred to as a fixing device),
Conventionally, devices of a contact heating system such as a heat roller system and a roller heating system have been widely used.

The above-described apparatus is also used in an apparatus for forming an image using a liquid containing a dye or a pigment, such as an ink jet system, in order to dry the ink quickly.

In such a device, a halogen lamp or a heating resistor is used as a heat source of a heating element, an electric current is applied to the heating element to generate heat, and the heat is transferred through a roller or a roller as a heat transfer member. And heat fixing is performed.

Japanese Patent Publication No. 5-9027 proposes an apparatus of an electromagnetic induction heating system in which an eddy current is generated in a fixing roller by magnetic flux and heat is generated by Joule heat. By utilizing the generation of the eddy current in this way, the heat generation position can be made closer to the toner, and the efficiency of energy consumption can be increased as compared with an apparatus using a halogen lamp.

The configuration of a conventional electromagnetic induction heating type fixing device will be described below with reference to FIG. In FIG. 8, a sheet P on which an unfixed image is placed is guided from the entrance guide 101 to the fixing device 100 to the fixing nip N, and
2, the sheet P is nipped and conveyed by a pressure roller 103 which is driven to rotate with respect to the fixing roller 102, and an unfixed image is fixed on the sheet P by heat from the fixing roller 102.

The fixing roller 102 comprises a driving and rotating fixing cylinder 102a, and a heat generating core (alternating magnetic field generating means) 104 fixedly disposed inside the fixing cylinder 102a and causing the fixing cylinder 102a to generate heat. Alternating magnetic field generating means 1
Reference numeral 04 denotes a casing made of a semi-cylindrical heat-resistant resin. An excitation coil 105 is disposed on the fixing nip side as shown in the figure, and a core 106 made of a T-shaped ferrite material is provided inside the excitation coil 105. Is arranged.

When a heating signal is input from the controller 107 to the DC voltage generator 108, a high frequency alternating voltage of, for example, 100 V, 100 kHz is applied to the exciting coil 105 by the exciting circuit 109. The magnetic flux generated by the exciting coil 105 is guided to the core 106, and generates an eddy current in the conductive layer of the fixing cylinder 102a in the fixing nip, and causes the fixing roller 102 to generate heat by Joule heat due to the eddy current.

[0009]

In recent years, in such an induction heating type fixing apparatus, when the apparatus is started up, the temperature of a fixing cylinder, which is an induction heating element, is started, and then the fixing temperature is reached and the fixing process is performed. There is a demand for a shorter time to start, that is, a quick start.

However, if the inner thickness of the fixing cylinder 103 is reduced in order to realize a quick start by reducing the heat capacity of the fixing cylinder 103, the fixing cylinder 103 may be permanently deformed by the pressure contact with the pressure roller. is there. For this reason, if the pressure between the fixing cylinder 103 and the pressure roller is set to a small value, it is not possible to sufficiently secure the force for pressing the toner image and the heating area (nip area) at the time of fixing, so that good fixing performance (heating performance) is obtained. It becomes difficult to get.

Therefore, it is necessary to raise the fixing temperature in order to secure the fixing performance with a small pressure and a small fixing nip. However, if the temperature is increased, problems such as a rise in the temperature of the non-sheet passing portion and a high-temperature offset occur.

That is, in the fixing device using the electromagnetic induction heating method, there is no latitude in the inner thickness of the fixing cylinder 103 for realizing the quick start and the inner thickness of the fixing cylinder 103 satisfying the fixing property.

Accordingly, an object of the present invention is to form a plurality of nip portions for image heating so that good heating performance can be obtained even at a low nip pressure, and to reduce the heat capacity of the induction heating element to achieve a quick start. It is an object of the present invention to provide an image heating apparatus and an image forming apparatus of an electromagnetic induction heating type capable of achieving image formation.

[0014]

An image heating apparatus and an image forming apparatus according to the present invention have the following features to solve the above-mentioned problems.

[1]: an induction heating element that moves or rotates,
An electromagnetic induction heating type image heating apparatus comprising: an alternating magnetic field generating means for causing the induction heating element to generate electromagnetic induction heat; and a pressurizing member which presses the induction heating element to form a nip. Wherein a plurality of recording materials are formed, and the recording material is sequentially conveyed to the plurality of nip portions to heat an image on the recording material.

[2] The image heating apparatus according to [1], wherein the plurality of nip portions are formed by one induction heating element and pressure members arranged at least at two places. .

[3] The image heating apparatus according to [1] or [2], wherein the temperatures of the plurality of nip portions are different from each other.

[4] The image heating apparatus according to [3], wherein the temperature of the plurality of nip portions is lower on the downstream side than on the upstream side in the recording material conveyance direction.

[5] The image heating apparatus according to [1], wherein the plurality of nips are heated using different magnetic field sources.

[6] The image according to any one of [1] to [5], wherein the alternating magnetic field generating means is movable in a direction in which a magnetic field in a plurality of nips is changed. Heating equipment.

[7] The image heating apparatus according to any one of [1] to [6], wherein the image on the recording material is heated and fixed on the recording material.

[8]: In an image forming apparatus having an image forming means for forming an image on a recording material and an image heating means for heating the image on the recording material, [1] to [8] An image forming apparatus comprising the image heating device according to any one of the preceding claims.

<Operation> By forming a plurality of press-contact nip portions between the induction heating element and the pressurizing member as described above, a sufficient heating area (nip portion) can be secured without increasing the pressure of the pressurizing member. As a result, the thickness of the induction heating element can be reduced, so that a quick start can be realized.

[0024]

FIG. 1 is a sectional view of a fixing device according to a first embodiment, and FIG. 2 is a perspective view of an exciting coil.

In FIG. 1, reference numeral 1 denotes a fixing device using an electromagnetic induction heating system as an image heating device according to the present invention, which is provided in a copying machine (image forming apparatus) described later, and is a transfer device on which an unfixed image is formed. When the paper (paper) P is introduced, the fixing process is performed by the heat from the induction heating element and the pressure of the fixing nip.

The fixing roller 3 is composed of a fixing cylinder 4 in which the surface of a conductive metal pipe is coated with a fluororesin (for example, Teflon (trademark)) having a good toner releasing property, and an alternating magnetic field generating means 5. Have been.
The fixing cylinder 4 is rotationally driven by a rotational drive transmitted from a driving unit (not shown), and the alternating magnetic field generating unit 5 is fixedly disposed inside the fixing cylinder 4.

The alternating magnetic field generating means 5 has excitation coils 7, 8 and cores 11, 12, 13 arranged around a support member 6, and a casing made of a heat-resistant resin such as PPS or LCP is provided on the outer periphery thereof. , Are arranged in parallel with the longitudinal direction of the nip. As shown in FIG.
Numeral 8 is wound and arranged in the longitudinal direction of the alternating magnetic field generating means 5. Voltage application to the excitation coils 7 and 8 is connected to the excitation circuits A9 and B10 shown in FIG.

The pressure rollers 14A and 14B are provided with an elastic layer having good heat resistance such as silicon rubber or fluoro rubber around the cored bar, and a layer made of a material having good toner releasability such as Teflon is formed on the outermost layer. ing. The pressure rollers 14A and 14B are arranged so as to form at least two nips on the circumferential surface of the fixing roller 3, and are brought into contact with a predetermined pressure by a pressure unit (not shown). A guide member 15 is disposed between the pressure rollers 14A and 14B so that the transfer paper does not enter between the rollers. A pressure roller 14 is provided on the inner surface of the fixing cylinder 4.
In order to detect the temperature at the nip-corresponding positions of A and 14B, temperature detecting elements (thermistors in this example) 16A and 16B are in contact with each other at a predetermined pressure. Then, the detection signal is guided to a controller (CPU) 17.

The fixing roller 3 is coated with silicone oil from the fixing web portion 18 and is cleaned. Separating claw 1 is provided on fixing roller 3 and pressure rollers 14A and 14B.
9 and 20 are in contact with a predetermined pressure.

In order to raise the temperature of the fixing cylinder 4, a signal is input from the controller (CPU) 17 to the DC voltage generators A21 and B22.
To generate a DC voltage. And the excitation circuits A9, B10
Thus, the alternating voltage is converted to about 100 kHz, and the alternating voltage is applied to the exciting coils 7 and 8 respectively. The magnetic flux generated by the exciting coils 7 and 8 is
In each fixing nip, the fixing cylinder 4
A magnetic field enters the conductive layer, and an eddy current is generated in the conductive layer to heat each nip portion N. Each nip temperature is determined by thermistor 16
A, 16B, and the controller (CPU) 17 controls the DC voltage generator A2 according to the temperature.
1 and B22 to control the temperature.

As an example of the temperature control, when the temperature control of the fixing roller 3 is started from the room temperature, the thermistors 16A, 1
Full operation (maximum power supply) is performed until the temperature of the thermistor 16B reaches 200 ° C., and when the temperature reaches 200 ° C., the roller surface temperature of the thermistor 16B is reduced as shown in FIG.
DC voltage generator A2 so as to be lower than the surface temperature of
1 and B22.

As described above, by forming a plurality of nip portions N and sequentially transporting the recording material P to the plurality of nip portions N to thermally fix the image on the recording material, the fixing property is improved even when the nip pressure is reduced. , The thickness of the fixing cylinder 4 can be reduced, and the heat capacity of the fixing roller can be reduced, thereby achieving a quick start. Further, since there is no need to forcibly raise the fixing temperature, a power-saving fixing device can be provided, and troubles such as high-temperature offset can be prevented.

Further, by lowering the temperature (fixing temperature) of the nip portion N on the downstream side of the upstream side in the paper transport direction, the fixing separation property is improved (the lower the fixing temperature, the more the recording material P is separated from the fixing roller. It's easy to do). As a result, the frequency of fixing jams was reduced, and the reliability of the copying machine itself was improved.

Further, by rotating two or more of the pressure rollers 14A and 14B into contact with the fixing roller 3, the temperature rise of the non-sheet passing portion which occurs when the small size sheet is continuously passed is also made uniform in temperature. , Can be prevented. As a result, there is no need to raise the (resin) grade of the fixing component, and there is a cost advantage.

(Second Embodiment) FIGS. 5 and 6 are sectional views of a fixing device according to a second embodiment. FIG. 7 is a longitudinal sectional view of the fixing device according to the second embodiment. Components having the same role as in the above-described embodiment are denoted by the same reference numerals, and description thereof is omitted.

The fixing device 29 using the electromagnetic induction heating system of the second embodiment differs from the first embodiment in the configuration of the fixing roller 30. Another difference is that a mechanism for changing the pressing force of the pressure rollers 14A and 14B is provided.

In the first embodiment, the pressure rollers 14A, 1
In order to differentiate the temperature of the nip portion N formed in FIG.
As shown in (1), the excitation coils 7 and 8 are separately controlled. In the second embodiment, as shown in FIG. 5, there is one excitation coil 7, and the alternating magnetic field generating means 31 supporting the coil 7 is swung about the rotation center 31A as an axis, so that the pressing roller 14A , 14B (FIG. 6).

Next, a method of driving the alternating magnetic field generating means 31 to swing will be described. As shown in FIG. 7, both ends of the alternating magnetic field generating means 31 are supported by bearings 32 in the fixing roller 30. A gear 33 is fixed to the end of the rotation center 31A so that the rotation of the stepping motor 37 can be transmitted. The alternating magnetic field generating means 31 has a configuration in which the exciting coil 7 and the cores 12 and 13 are arranged around the support member 6, and a casing is provided on the outer periphery with a heat-resistant resin such as PPS or LCD. Fixing roller 30
As shown in FIG. 7, both ends of the fixing roller 30 are rotatably supported by fixing side plates 34 and 35 via bearings 36.
The driving is transmitted from the fixing drive gear fixed to and rotated. The circuit that causes the fixing roller 30 to generate heat is connected to the controller (CPU) 38 直流 DC voltage generator 39 励 excitation circuit 40 ⇔ excitation coil 7, as in the first embodiment.

Next, a mechanism for changing the pressing force of the pressing rollers 14A and 14B to the fixing roller will be described. As shown in FIG. 7, both ends of the pressure roller 14A are
The pressure arms 42 and 43 are urged by a pressure spring 44 so as to obtain a pressing force. The working length of the pressure spring 44 changes as the positions of the spring metal plates 45 and 46 move in the vertical direction in the figure, and the pressing force of the pressure rollers 14A and 14B also changes. Spring seat plate 45,
46 is supported so as to be able to move up and down, and a shaft 47 is freely penetrated. Circular rollers 55 are fixed to both ends of the shaft 47, and the fixing side plates 34, 3 are movable in the vertical direction in the figure.
5 has a long hole. The shaft 4 is located below the roller 55.
An eccentric cam 49 fixed to 8 is arranged, and a gear 50 is fixed to the end of the shaft 48, and the gear 50 is configured to transmit the drive of the stepping motor 51.

When changing the pressing force, the controller
A (CPU) 38 drives a stepping motor 51 to rotate an eccentric cam 49 via a gear 50 and a shaft 48, thereby moving a roller 55 driven by the eccentric cam 49 up and down, and a spring engaged with the shaft 47. The pressing force is adjusted by moving the seat plate 45 up and down.

Next, the temperature control operation of the fixing device 29 will be described.

First, at the start of temperature control, the alternating magnetic field generating means 31
Is at the position shown in FIG. 5, and the nip temperature of the pressure rollers 14A and 14B is increased to, for example, 200 ° C. The nip temperature at this time is monitored by thermistors 16A and 16B,
Feedback control is performed by a controller (CPU) 38. The thermistors 16A and 16B are at the target temperature 200
When the temperature reaches ° C, the stepping motor 37 shown in FIG. 7 is driven to rotate the alternating magnetic field generation means 31 to the upstream side in the recording material conveyance direction, and the temperature is monitored by the thermistors 16A and 16B while the temperature gradient shown in FIG. Attached. At this time, the DC voltage generator 39 is also a controller (CPU) 38.
And temperature control. For example, control is performed so that the temperature detected by one thermistor 16A becomes a predetermined temperature.

Next, an example of a fixing operation of the fixing device 29 will be described.

(1) When performing temperature control from the state where the fixing roller 30 is cooled, the stepping motor 51 shown in FIG.
14B is kept apart. By performing such an operation, the surface temperature of the fixing cylinder 4 is reduced.
4A, 14B quickly rises without being exposed to heat.

(2) The use environment of the fixing device and the type and size of the paper P are detected in advance by a temperature / humidity detecting means (not shown) and a paper type / size detecting means (not shown). The stepping motor 51 is controlled so as to minimize the curl amount, and the pressing force of the pressure roller is controlled.

(3) When a thicker than normal paper type of, for example, 200 / m ² basis weight is selected as the paper P, the stepping motor 51 is controlled by the controller 38 and the pressure roller 14 is controlled.
The pressure of A and 14B is made as low as possible. In this case, since the paper P is thick, the pressure applied to the paper P is the same even if the pressure is reduced. In particular, according to this operation, when thick paper enters the fixing device 29, the transfer vibration of the paper P and the image failure ( So-called fixing rush shock) can be reduced.

Also, in this embodiment, by providing a plurality of nips, the same effect as in the above-described embodiment can be obtained.

(Example of Image Forming Apparatus) Next, the image forming apparatus 23 of the present invention will be described with reference to FIG.

The apparatus 23 of this embodiment is an optical copying machine provided with the above-described fixing device 1 or 29.

When the image forming operation is started, the paper (transfer paper) P loaded in the cassette 24 is
5 and 26, the document is sent to the image forming means side, and the document placed on the document table 60 is optically scanned by the optical system 61, and the image is formed on the photosensitive drum 62 for exposure. ,
The electrostatic latent image resulting from the exposure is developed by a developing unit 63 to form a toner image. The toner image and the sheet P are synchronously introduced into a transfer unit m, and the toner image is transferred onto the sheet P by a transfer unit 64. Is transferred. Each of these elements 60, 61, 62, 6
The sheet P carrying the toner image by the image forming means 3 and 64 is introduced into the fixing device 1 or the fixing device 29 via the transport section 65 and subjected to the fixing process, and the image forming device 23
It is discharged outside.

As described above, the provision of the fixing devices 1 and 29 according to the first or second embodiment enables a quick start of the device. Further, high-temperature offset, non-sheet passing portion temperature rise, and fixing rush shock can be suppressed, and good image formation can be performed.

Further, the fixing separation property was good, the frequency of fixing jam was reduced, and the reliability was improved.

[0053]

As described above, according to the present invention,
Electromagnetic induction heating that forms a plurality of nips for image heating so that good heating performance can be obtained even at a low nip pressure, and reduces the heat capacity of the induction heating element for quick start It is possible to provide an image heating apparatus and an image forming apparatus of a system.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a fixing device according to a first embodiment.

FIG. 2 is a perspective view of an excitation coil of the fixing device according to the first embodiment.

FIG. 3 is a cross-sectional view of the image forming apparatus including the fixing device according to the first embodiment.

FIG. 4 is a temperature distribution diagram of a fixing roller.

FIG. 5 is a sectional view of a fixing device according to a second embodiment.

FIG. 6 is a sectional view of a fixing device according to a second embodiment.

FIG. 7 is a longitudinal sectional view of a fixing device according to a second embodiment.

FIG. 8 is a sectional view of a fixing device according to a conventional technique.

[Explanation of symbols]

 1, 29 Fixing device 3, 30 Fixing roller (induction heating element) 4 Fixing cylinder 5 Alternating magnetic field generating means 6 Support member 7 Exciting coil 9 Electrode portion 11, 12, 13 Core 14A, 14B Pressure roller 15 Guide member 16A, 16B Thermistor 18 Fixing web section 19, 20 Separation claw 23 Image forming apparatus 24 Cassette 25, 26 Transport path 28 Transport section 31 Alternating magnetic field generating means 31A Rotation center 32 Bearing 33 Gear 34, 35 Fixing side plate 36 Bearing 37 Stepping motor 38 Controller 39 DC Voltage generating device 40 Excitation circuit 41A Bearing 42, 43 Pressing arm 44 Pressing spring 45, 46 Spring seat plate 47 Shaft 48 Shaft 49 Eccentric cam 50 Gear 51 Stepping motor 55 Roller 60 Document table 61 Optical system 62 Photosensitive drum 63 Development 64 Transfer device 100 Fixing device 101 Entrance guide 102 Fixing roller 103 Pressure roller 104 Heating core (alternating magnetic field generating means) 105 Exciting coil 106 Core 107 Controller 108 DC voltage generator 109 Exciting circuit A21, B22 DC voltage generator A9, B10 Excitation circuit N Nip section P Paper (recording material, transfer paper) m Transfer section

Claims (8)

[Claims] 1. An induction heating element that moves or rotates, an alternating magnetic field generating means for causing the induction heating element to generate electromagnetic induction,
And an image heating apparatus of an electromagnetic induction heating system having a pressing member that presses against the induction heating element to form a nip portion, wherein a plurality of the nip portions are formed and a recording material is sequentially conveyed to the plurality of nip portions. An image heating apparatus for heating an image on the recording material. 2. An image heating apparatus according to claim 1, wherein said plurality of nip portions are formed by one induction heating element and at least two pressurizing members. 3. The image heating apparatus according to claim 1, wherein the plurality of nips have different temperatures. 4. The image heating apparatus according to claim 3, wherein the temperature of the plurality of nip portions is lower on the downstream side than on the upstream side in the recording material conveyance direction. 5. The image heating apparatus according to claim 1, wherein the plurality of nips are heated using different magnetic field sources. 6. The image heating apparatus according to claim 1, wherein said alternating magnetic field generating means is movable in a direction in which magnetic fields in a plurality of nips are changed. 7. The recording medium according to claim 1, wherein the image on the recording material is heated and fixed on the recording material.
Item 10. The image heating device according to item 1. 8. An image forming apparatus having an image forming means for forming an image on a recording material and an image heating means for heating the image on the recording material, wherein the image heating means is an image heating means. An image forming apparatus comprising the image heating device according to claim 1.