JP2002123113A - Fixing device and image forming device with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device capable of obtaining a stable image with high fixation and free from uneven glossiness, and also, capable of attaining the improved durability and improved safety by stably controlling the temperature of a fixing body with less ripple fluctuation, while accomplishing energy- saving and on-demand, and to provide an image forming device equipped with the fixing device. SOLUTION: The device is provided with a secondary coil 4 connected to a heating body 9, and a primary coil 3 arranged so as to magnetically connected to the secondary coil 4, and the power from a power source 8 is received by the primary coil 3, thereafter, the power is supplied to the secondary coil 4, the secondary coil 4 and the primary coil 3 are directly or indirectly attached to a fixing roller 1 and a supporting member for the fixing roller 1, respectively, and the power from the power source 8 is supplied to the heating body 9 in a non-contact state by the magnetic connection between the secondary coil 4 and the primary coil 3.

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 an unfixed image onto the recording material by heating and pressing while holding and transporting a recording material carrying an unfixed image by a fixing member and a pressing member. And an image forming apparatus including the fixing device.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, a printer, a facsimile or the like which adopts an electrophotographic system, a problem of increasing energy saving in recent years is a problem of energy saving.

A fixing device provided in such an image forming apparatus directly consumes electric power as heat energy in order to melt an unfixed image containing toner and fix it on a sheet as a recording material. It accounts for a large factor in the power consumption used overall.

[0004] For this reason, in such a fixing device, a fixing device on demand has been known as one direction for reducing the power consumption.

In the fixing device, the fixing body is formed as a thin roller, a thin belt, or a film, so that the heat capacity is reduced to speed up the start-up and, at the same time, the power consumption during the fixing is suppressed.

[0006] By achieving on-demand in this way,
When a print signal is received, there is almost no waiting time, and printing starts immediately.Therefore, it is not necessary to keep the fixing body at a high temperature near the printing temperature during non-printing. Just fine. The heat radiation at the time of keeping the temperature of the fixing device increases in proportion to the temperature difference between the environmental temperature and the set temperature of the fixing body, and these always consume power even in a state where no printing is performed. Therefore, in a situation where printing is intermittently repeated, on-demanding brings a very large power saving effect.

[0007] In such a fixing device, generally, a method of heating the inside of the fixing member by a heater serving as a heating member is mainly used. In the case of using a halogen lamp as a heater and a fixing roller as a fixing body, the glass surface of the halogen lamp reaches a high temperature of 400 ° C. or more, but the actual temperature control is about 180 ° C. by detecting the surface temperature of the fixing roller. It is done in. On the other hand, when a ceramic heater as a heater and a fixing film as a fixing body are used, the temperature of the ceramic heater is about 190 to 200 ° C., and the same fixing property as the former is obtained. The latter system, which can be reduced to as low as possible, has less heat loss and is more efficient.

Similarly, a method in which the fixing body itself generates heat,
For example, a system using a self-heating element or magnetic induction heating can reduce the top temperature and is a highly efficient system.
In addition, since the vicinity of the surface of the fixing body is directly heated, the thermal responsiveness is improved, and stable temperature control with a small ripple compared to roller fixing by normal halogen lamp heating is possible.
The latitude between the high-temperature offset region and the low-temperature offset region can be effectively used. As a result, a stable image having high fixability without gloss unevenness can be obtained.

[0009]

However, although a fixing device having a self-heating type fixing roller having a sheet heating element which can be said to be the most popular among the above-mentioned fixing devices has been invented for a long time, Until now, there have been few practical applications. The biggest problem that could not be realized is that, in addition to the durability and stability of the fixing roller itself, the only practical sliding contacts that can pass a large current of about 10 A are carbon chips or tin or mercury contacts. That was not there. In the configuration using the sliding contact as in the prior art, discharge frequently occurs between the contact electrodes,
Generates noise. In addition, when the discharge is repeated, an oxide film is formed on the metal contact surface of the contact portion, and the electrode burns due to heating, so that the reliability, safety and durability of the product cannot be obtained.

Accordingly, the present invention realizes a stable fixing body temperature with small ripple fluctuations while realizing energy saving and on-demand, thereby obtaining a stable image with high fixability without gloss unevenness. It is an object of the present invention to provide a fixing device capable of improving the durability and safety of the device, and an image forming apparatus including the fixing device.

[0011]

According to the present invention, an object of the present invention is to provide a fixing member and a pressing member which rotate by pressing against each other, and a heating member which receives electric power from a power source and heats the fixing member.
A fixing device for fixing the unfixed image to the recording material by heating and pressurizing the recording material carrying an unfixed image while nipping and conveying the recording material by the fixing body and the pressing body, wherein the heating element is In a fixing device that rotates together with a fixing member, a power receiving portion formed by a coil connected to a heating member, and a power supply portion formed by a coil disposed so as to be magnetically coupled to the coil of the power supplying and receiving portion With
The power supply unit receives power from a power supply and supplies the power to a power receiving unit. The power receiving unit is attached to the fixing body and the power supply unit is directly or indirectly attached to a support member for the fixing body. This is achieved by the first invention in which the electric power from the power supply is supplied to the heating body in a non-contact manner by magnetic coupling between the electric power receiving unit and the electric power supply unit.

Further, according to the present application, the above object is achieved in the first aspect, in which the fixing member has a roller shape, and the heating member is a resistance heating element or a resistance heating element integrally formed with the fixing member. This is also achieved by the second invention in which the coil of the power receiving portion and the heating element form a closed circuit.

Further, according to the present application, the object is an image forming apparatus for recording an image formed by a series of image forming processes on a recording material, wherein the fixing device according to the first invention or the second invention is provided. The invention is also achieved by the third invention having:

[0014]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

(First Embodiment) First, a first embodiment of the present invention will be described.

FIG. 1 shows an electrophotographic laser beam printer 101 as an example suitably showing the image forming apparatus of the present embodiment.
FIG. 1 is a schematic cross-sectional view illustrating a schematic configuration of a printer (hereinafter, abbreviated as a printer 101).

The printer 101 forms an image corresponding to image information provided from an image information providing device (not shown) such as a host computer provided outside the main body of the printer 101 on a sheet-shaped recording material P. This is an image forming apparatus in which a series of image forming processes of recording is performed according to a known electrophotographic method.

As shown in FIG. 1, a printer 101 includes a drum-shaped rotatable photosensitive member 102 serving as a latent image carrier and a process cartridge 104 holding a developing device 103.
And a laser scanner unit 1 for forming an electrostatic latent image according to the image information on the outer peripheral surface of the photoconductor 102 by an exposure processing step according to the image information from the image information providing device.
05 (hereinafter, abbreviated as a scanner 105), a roll-shaped rotatable transfer member 106 for performing a transfer processing step on the recording material P, and a fixing process on the transferred recording material P by heating and pressing. Fixing device 107 that applies
And

The process cartridge 104 provided in the printer 101 includes, in addition to the photosensitive member 102 and the developing device 103, the photosensitive member 10 before the exposure process by the scanner 105.
Charging roller 1 for charging the outer peripheral surface of the roller 2 to a specified potential distribution
08 and is detachably supported by the main body of the printer 101. When maintenance such as repair of the photoconductor 102 and supply of the developer to the developing device 103 is required, the main body of the printer 101 can be opened and closed by the main body. Open the cover 109 supported by the process cartridge 1
By exchanging the entire unit 04, the maintenance can be speeded up and simplified.

Next, a series of image forming processes in the printer 101 will be described.

First, the photosensitive member 102 is moved in the direction of arrow K1 by pressing a start button or the like (not shown) provided on the main body of the printer 101 to instruct the printer 101 to start a series of image forming processes. Rotational drive is started at a specified peripheral speed, and the outer peripheral surface of the photoconductor 102 is charged to a specified potential distribution by the charging roller 108 and the photoconductor 102, to which a specified bias is applied, slidingly contacting each other.

Next, the charged portion of the outer peripheral surface of the photoreceptor 102 is scanned and exposed by the scanner 105 in accordance with the image information from the image information providing device, so that an electrostatic latent image corresponding to the image information is obtained. Is formed in the above-described region, the electrostatic latent image is visualized into a visible image by the developer of the developing device 103, and a predetermined number of recording materials P can be stored and removed by the main body of the printer 101. The transfer member is transferred onto the recording material P which is conveyed at a predetermined timing from a freely supported cassette 111 to a space formed between the photosensitive member 102 and the transfer member 106 by a rotatable paper feed roller 112 or the like. The visible image is transferred by 106.

The recording material P on which the transfer processing has been performed is subjected to fixing processing by the fixing
The sheet is discharged to the outside of the apparatus by a discharge roller 113 rotatably supported by the main body 1 and is stacked on a tray 114 attached to one side of the main body, thereby completing a series of image forming processes. It will be.

Next, the fixing device 107 will be described in detail.

FIG. 2 is a side sectional view showing a schematic configuration of the fixing device 107.

As shown in FIG. 2, the fixing device 107 includes a fixing roller 1 as a fixing member, a pressure roller 2 as a pressing member,
It includes a heating element 9, a primary coil 3 as a power supply unit, and a secondary coil 4 as a power reception unit.

The fixing roller 1 is supported by a bearing 5,
The drive gear 7 is driven and rotated.

The pressure roller 2 is supported by a bearing 5 ′, is pressed against the fixing roller 1, and is driven to rotate.

Further, the fixing roller 1 has a heating element 9 mounted inside, and electric power from a power source 8 is supplied to the heating element 9 from a secondary coil 4 integrated and integrated inside the fixing roller 1. It has become feverish. The power supplied to the primary coil 3 by the power supply 8 is temporarily in the form of magnetic energy by magnetic coupling, and is transmitted to the secondary coil 4 in a non-contact state.

That is, the primary coil 3, which is the primary side of the magnetic coupling portion formed by the primary coil 3 and the secondary coil 4, is fixedly arranged on a support member (not shown) for the fixing roller 1.
The secondary coil 4, which is the secondary side, is attached to the fixing roller 1 to be movable, and a minute gap is provided between the two so that power can be supplied to the heating member 9 of the fixing roller 1 in a non-contact manner. . The magnetic coupling portion may be incorporated in the entire heat generating portion of the fixing roller 1 or may be localized at an end.

The magnetic coupling portion includes a primary side which supplies power to each other and is provided outside the fixing roller 1, and a secondary side which is integrally driven with the roller and is rotationally driven.

Since the magnetic coupling portion is smaller than that of the magnetic induction heating system and is only between the gaps of about 0.1 to 0.8 mm, a magnetically almost closed circuit is formed. The noise prevention shield requires a minimum range. If the magnetic coupling portion is disposed inside the fixing roller, the shielding effect of the fixing roller core metal can be used.

As shown in FIG. 3, in the magnetic coupling portion of this embodiment, the primary coil 3 and the secondary coil 4 have cores 3A and 4A and coils 3B and 4B forming a magnetic circuit, respectively. I have.

The cores 3A and 4A have a Curie temperature of 220 to
A ferrite core of about 260 ° C. is used. this is,
It is already industrially produced as an electronic component and is inexpensive.

The wires of the coils 3B and 4B are made of litz wire or the like so as to withstand a large current of about 10A. By increasing the design efficiency of the magnetic circuit, the number of turns on the primary and secondary sides may be about several to ten turns. The number of turns may be the same or different. Although various methods of arranging the coils are conceivable, the present embodiment shows a configuration in which the fixing roller is wound in the circumferential direction.

As the power supply 8, by using a circuit configuration such as an existing switching power supply or an inverter circuit, a system with high efficiency and reduced cost can be provided. For example, the execution voltage is changed by turning on / off a switching power supply to control the amount of heat generated, or the AC input is converted into a high frequency of about several tens to 100 kHz by a PWM inverter circuit, and is converted into a magnetic field by a primary coil. Then, the power can be transmitted by receiving the secondary coil and converting the current again. It is also possible to increase the voltage on the primary side to increase the power transmission efficiency of the coil.

Although various configurations of the fixing body and the heating body are possible, in this embodiment, as shown in FIG. 4, the surface release layer 14 and the elastic layer 14 are provided on the outer surface of the cored bar 12 of the fixing roller 1. The heating element 9 has a layer structure in which a heating layer 10 serving as a resistance heating layer and an insulating layer 11 are integrally formed on the inner surface of the cored bar 12 as the heating element 9.

The fixing roller 1 has a diameter of 40φ, a cored bar 12 formed as a hollow cylindrical body, and a heat generating layer 1 mounted inside.
0 allows self-heating.

The surface release layer 14 is formed as a fluororesin tube or a coating layer of FEP, PTFE, CPTFE, PFA or the like having a thickness of about 10 to 30 μm. Under the lower layer, an elastic layer 13 of low hardness HTV silicone rubber having a thickness of 1.5 t is formed. The core 12 is made of aluminum 6063 having a thickness of 2t.

On the inner surface of the metal core 12, an insulating layer 11 made of a heat-resistant resin is formed on a thickness of 0.6 t, and a heat generating layer 10 is formed with a thickness of 0.3 t. The heating layer 10 is a low-resistance heating element in which a conductive carbon particle material such as carbon black or Ketjen black is dispersed in a heat-resistant resin such as polyimide or a fluorine resin. Alternatively, carbon rubber may be dispersed in silicone rubber.

The heating layer 10 has ring-shaped electrodes (not shown) connected to the litz wire of the secondary coil at both ends in the axial direction of the fixing roller 1. The resistance value between the electrodes is about several to several tens of ohms at 100V.

The pressure roller 2 has an HTV silicone rubber 2t under a surface release layer similar to the fixing roller 1 having a diameter of 40φ.
Is formed in a two-layer configuration. The pressure roller 2 is driven to rotate in a state where a nip is formed between the pressure roller 2 and the fixing roller 1 by pressing, and the nip width when stationary is 8.2 mm at the center in the axial direction.

In order to achieve on-demand at the time of startup, it is necessary to transmit a large power of about 1000 W in a time of about several tens of seconds. Once the print temperature has been reached, it is necessary to send power of about 80 to 100 W to keep it warm, and about 400 to 500 W during paper fixing.

It took approximately 90 seconds to rise from room room temperature to a printing temperature of 190 ° C. This is because although the surface temperature itself of the fixing roller 1 rises very quickly, in a configuration in which the pressure roller 2 does not have a heat source, the fixing property is low when the pressure roller 2 is cold, so that the heating is performed by multiple pre-rotations. This requires a rise time of about one minute or more. The fixing roller 1 and the pressure roller 2 had a surface temperature ripple of about ± 3 ° C. The peripheral speed of the fixing roller 1 and the pressing roller 2 is 30 to 120 mm / s, and the pressing force of the fixing roller 1 and the pressing roller 2 is 392 N (40 kN).
gf).

In the present embodiment, the temperature control of the fixing roller 1 and the pressure roller 2 is performed by detecting the roller surface temperature by the thermistor 6 in contact with the non-sheet passing area of the fixing roller 1.

Unlike a configuration in which a halogen heater is disposed inside a fixing roller or a pressure roller, a configuration in which a magnetic coupling portion is localized at one end of the fixing roller or the pressure roller has a fixing roller and a pressure roller. Replacement (roller replacement) is simplified. Normally, it is difficult for the user to replace the roller with the heat roller configuration, and thus the fixing unit is often replaced. However, in the present invention, only the roller replacement can be easily performed. For example, the fixing unit can be divided into upper and lower parts so as to be openable and closable so that the fixing roller and the pressure roller can be taken out immediately.

Incidentally, a roller structure in which the heat generating layer is provided on the outer surface side of the fixing roller or the pressing roller is of course also possible. Since the heating layer is close to the fixing surface, the fixing efficiency can be further improved.

As described above, according to this embodiment, since there is no contact, durability and safety as a product can be obtained, and the degree of freedom in fixing design according to the product specifications is improved. It is possible to respond to the future such as speeding up.

The cost can be reduced by modularizing the magnetic coupling portion, and it can be recycled when the fixing unit is collected.

As a feature or merit, the heat-generating portion of the fixing roller can be arbitrarily distributed and formed in a plane, and the degree of freedom in designing according to specifications is very high.

Unlike the magnetic induction heating method, the magnetic and thermal characteristics can be separated into factors, so that the performance of each characteristic can be improved.

Further, similarly to the configuration using the normal rollers,
The pressure can be increased.

Further, by using a boosting effect of a normal switching power supply or a simple inverter circuit as a power supply, a system with high efficiency and low cost can be provided.

Further, the magnetic coupling portion is smaller than that of the magnetic induction heating system, only between the gaps of about a few mm, and the shield for preventing electromagnetic noise can be minimized.

Further, a material having a Curie point of about 270 ° C. already exists in the magnetic core, and the cost cannot be reduced.

(Second Embodiment) Next, a second embodiment of the present invention will be described. Note that the same components as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

In the first embodiment, as shown in FIG.
The gap of the magnetic coupling between the primary coil 3 and the secondary coil 4 is provided on the end face of the fixing roller 1 to form a parallel gap.
Although the lines of magnetic force are directed in the axial direction of the fixing roller 1, in the present embodiment, as shown in FIG. 5, this is used as a circumferential gap so that the lines of magnetic force are directed in the radial direction of the fixing roller 1. .

The advantage of the present embodiment is that, unlike the parallel gap described above, even when the alternating current from the power supply is at a low frequency, the vibration due to the axial mutual magnetic force applied to the primary side and the secondary side of the transformer in the magnetic coupling. That is, it can be canceled and prevented in the circumferential direction.

(Third Embodiment) Next, a third embodiment of the present invention will be described. Note that the same components as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

In the present embodiment, the thermistorless operation is achieved by utilizing the change in the resistance of the heating element due to the temperature.

For example, PT having conductive carbon particles dispersed therein
A heat-resistant resin such as FE can have a positive resistance-temperature characteristic (PTC) such that when the temperature rises, the distance between particles increases due to thermal expansion and the resistance value of the heating element increases. That is, self-temperature control may be performed by using a PTC heater as a so-called heating element to keep the applied voltage constant (the Joule heat Q of the heater is Q = V ² / R with respect to the applied voltage V to both ends). Alternatively, the temperature control may be performed based on the response signal of the transformer.

One method is as follows. Fluctuations in the resistance R of the heating element cause fluctuations in the impedance Z on the primary side of the transformer. Since this impedance value can be detected using a bridge circuit or the like, it is possible to perform non-contact temperature detection. Assuming that the number of turns of the primary coil is n1 and the number of turns of the secondary coil is n2, the transformation ratio k is k = n1 / n2. When the inductance value of the primary-side inductance value of L1,2 primary and L2, have a relationship of L2 / L1 = k ^2. When the resistance value of the heating element on the secondary side is a function of temperature R (T), an AC voltage having an angular frequency ω is applied ignoring the resistance on the primary side for simplicity. Then, Z (T) = L1 / ((1 / ω) ² + (L2 / R
(T)) ² ) The impedance is also a function of temperature, with a relationship such as ^0.5 .

By measuring and grasping this relationship in advance, the temperature can be controlled by controlling the applied voltage based on the impedance value. Another method is to use a magnetic sensor for detecting the amount of current instead of directly using a large current.
The value of the current flowing in the next coil may be indirectly detected to capture the impedance fluctuation, and the temperature may be controlled accordingly.

[0064]

As described above, according to the first invention of the present application, electric power from a power supply is supplied to a heating element in a non-contact manner by magnetic coupling between a power receiving section and a power supply section. Therefore, by performing stable fixing temperature control with small ripple fluctuation while realizing energy saving and on-demand, it is possible to obtain a stable image with high fixability without uneven gloss and durability and safety of the apparatus. Performance can be improved.

According to the second invention of the present application,
Since the power from the power supply is supplied to the resistance heating element or the resistance heating layer in a non-contact manner by magnetic coupling between the power receiving unit and the power supply unit, energy saving and on-demand can be realized.
By performing stable fixing body temperature control with small ripple fluctuation, it is possible to obtain a stable image having high fixability without uneven gloss and to improve the durability and safety of the apparatus.

Further, according to the third aspect of the present invention, the electric power from the power supply is supplied to the heating element in a non-contact manner by the magnetic coupling between the electric power receiving section and the electric power supply section. By achieving stable fixing body temperature control with small ripple fluctuation while realizing image quality, it is possible to obtain a stable image with high fixability without uneven gloss and to improve the durability and safety of the apparatus. Can be.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view illustrating a schematic configuration of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a side sectional view showing a schematic configuration of a fixing device provided in the image forming apparatus of FIG.

FIG. 3 is a diagram illustrating an example of a configuration of a magnetic coupling unit including a power supply unit and a power reception unit of the fixing device in FIG. 2;

FIG. 4 is a diagram illustrating an example of a layer configuration of a fixing member provided in the fixing device of FIG. 2;

FIG. 5 is a diagram illustrating an example of a configuration of a magnetic coupling unit including a power supply unit and a power reception unit according to a second embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Fixing roller (fixing body) 2 Pressure roller (pressing body) 3 Primary coil (power supply part) 4 Secondary coil (power receiving part) 3B, 4B coil 8 Power supply 9 Heating body 10 Heating layer (resistance heating layer) ) 101 Electrophotographic laser beam printer (image forming apparatus) 107 Fixing device P Recording material

Claims (3)

[Claims] An image forming apparatus comprising: a fixing member and a pressure member that rotate in pressure contact with each other; and a heating member that receives power from a power source and heats the fixing member. A fixing device for fixing the unfixed image on the recording material by heating and pressing while being nipped and conveyed by a pressurizing member, wherein the fixing device rotates with the fixing member. And a power supply unit formed of a coil disposed so as to be magnetically coupled to the coil of the power supply / reception unit, and the power supply unit receives power from a power supply. The power receiving unit is attached to a fixing member, and the power supply unit is directly or indirectly attached to a support member for the fixing member. With the department A fixing device configured to supply electric power from a power supply to a heating body in a non-contact manner by magnetic coupling between the heating elements. 2. The fixing body has a roller shape, and the heating body is a resistance heating body or a resistance heating layer integrally formed with the fixing body. The coil of the power receiving unit and the heating body are closed circuit. The fixing device according to claim 1, wherein the fixing device is formed. 3. An image forming apparatus for recording an image formed by a series of image forming processes on a recording material, comprising the fixing device according to claim 1 or 2. .