JP2003223979A - Induction heating roller device, fixing device and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an induction heating roller device in which the heating time of a heating roller is shortened, and provide a fixing device and an image forming device equipped with this in an induction heating method. <P>SOLUTION: This has the heating roller HR in which the induction current flows to generate heat when magnetically coupled to the postscript induction coils IC1, IC2, IC3, the induction coils IC1, IC2, IC3 arranged and installed so as to be magnetically coupled with the heating roller HR, an alternate current power supply HFS to energize the induction coils IC1, IC2, IC3 by applying an alternate voltage to the induction coils IC1, IC2, IC3, and a control means CC of forming the prescribed pause period at the alternate voltage applied to the induction coils IC1, IC2, IC3. By forming a pause period in the alternate voltage, a heating efficiency after finishing the pause period becomes higher. <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 an induction heating roller device, a fixing device including the induction heating roller device, and an image forming apparatus.

[0002]

2. Description of the Related Art In order to thermally fix a toner image, a heating roller using a halogen bulb as a heat source has been conventionally used, but it is inefficient and requires a large amount of electric power. Therefore, development is being carried out to introduce the induction heating method to solve this problem.

Japanese Patent Laid-Open No. 2000-215974 discloses that
An exciting coil that is arranged close to the object to be heated and magnetically couples to a heating roller made of a magnetic material, which is the object to be heated, to generate an induced current (eddy current). The wound one is deformed along the curved surface of the heated body, and the magnetic core is arranged along the curved surface of the exciting coil on the opposite side of the longitudinal end of the exciting coil from the heated body. Exciting coils are listed. (Prior art 1)
Further, Japanese Patent Laid-Open No. 2000-215971 has a heating rotating body, that is, a heating roller, having an electromagnetic induction heat generation property, and a magnetic flux generating means disposed inside the heating rotating body and magnetically coupled to the heating roller. An induction heating device for heating a heated body by electromagnetic induction heating of a heating rotating body by high-frequency induction magnetic flux generated from the magnetic flux generating means, wherein the magnetic flux generating means includes a core made of a magnetic body and an electromagnetic conversion coil wound around the core. The magnetic core is opposed to the core portion around which the electromagnetic conversion coil is wound, and a magnetic space gap is provided between the tip portions to concentrate the magnetic flux from the core portion to a part of the heating rotor. A structure having a magnetic flux guiding core portion is described.
(Prior Art 2) Both of the prior arts 1 and 2 are heating methods utilizing eddy current loss (hereinafter referred to as eddy current loss heating method), and the same operation as is put to practical use in an IH jar or the like. It is the principle. The high frequency used in the eddy current loss method is 20 to 100 k.
It is about Hz.

On the other hand, Japanese Patent Laid-Open No. 59-33787 discloses a cylindrical roller body made of a conductive member, that is, a heating roller, a cylindrical bobbin concentrically arranged in the roller body, and an outer circumference of the bobbin. , A high-frequency induction heating roller provided with an induction coil that is spirally wound and induces an induction current in the roller body by energization to heat the same. (Prior Art 3) In the prior art 3, the cylindrical roller body serves as a closed-circuit secondary coil and the induction coil serves as a primary coil, and magnetic coupling like a transformer occurs between the two to form a cylindrical shape. A secondary voltage is induced in the secondary coil of the roller body. Then, based on this secondary voltage, a secondary current (induced current) flows in the closed circuit of the secondary coil, so that the cylindrical roller body generates heat, which is a heating method by the heat generated by the secondary side resistance (hereinafter referred to as a transformer). It is called the combined heating method). The transformer coupling heating method has a higher magnetic coupling than the eddy current loss heating method, so that the steady efficiency is high and the entire heating roller can be heated. Therefore, the structure of the fixing device is simpler than those of the prior arts 1 and 2. There is an advantage. In addition, operating frequency of 100 kHz or more,
By suitably setting the high frequency to 1 MHz or more, the Q of the induction coil can be increased and the power transmission efficiency can be increased. Therefore, the overall efficiency of heating is increased, and power saving can be achieved. There is also an advantage that the structure of the fixing device is simpler than that of the eddy current loss heating method. Further, the heat capacity can be made considerably smaller than that of the eddy current loss heating type heating roller. Therefore, the transformer coupling heating method is very suitable for increasing the speed of heat fixing.

The inventors of the present invention have previously proposed a closed circuit in which the secondary resistance of a heating roller having a hollow structure rotatably supported by air-core transformer type magnetic coupling to an induction coil is approximately equal to the secondary reactance. The invention has improved the transformer coupling method in which the power transmission efficiency from the induction coil to the heating roller is increased and the remarkable effect that the heating roller can be efficiently heated is obtained. This invention
The present application has been filed as Japanese Patent Application No. 2001-016335. According to the present invention, it is possible to save the electric power for the induction heating of the heating roller and speed up the heat fixing.

[0006]

However, in both the transformer coupling heating method and the eddy current loss heating method,
As an induction heating method, there are expectations for further speeding up of heating and power saving. The present inventor, while advancing the development of the above-described various induction heating roller devices, paid attention to the temperature rise with respect to time when the induction coil was energized with AC power. In the case of a heating roller using a conventional halogen light bulb, the temperature increases linearly with the energization time, as shown in graph B of FIG. On the other hand, in the induction heating method, as shown in the graph A of FIG. 1, the temperature rises rapidly immediately after the start of energization, but shows a saturation tendency with the passage of time, and the degree of temperature rise increases with time. It has the feature of reducing. Therefore, by defining the temperature rise value per second at the time of temperature rise as "heating efficiency" and looking at the change of this heating efficiency with time, as shown in the graph B of FIG. , Becomes almost constant, but in the case of the induction heating method, as shown in A of FIG.
It becomes a downward straight line that decreases in proportion to time.

1 and 2 are views for explaining the temperature rise of an induction heating type heating roller device together with that of a halogen bulb, FIG. 1 being a graph showing the temperature rise characteristic, and FIG. 2 being a heating efficiency characteristic. It is a graph shown. In each figure, the horizontal axis represents time, the vertical axis represents temperature in FIG. 1, and heating efficiency in FIG. Graph A shows heating by an induction heating system, and B shows heating by a halogen bulb.

That is, the heating of the induction heating system has a higher heating efficiency and a higher heating speed than the heating by the halogen bulb, but the heating efficiency decreases as the temperature rises, and eventually becomes smaller than that of the halogen bulb. Become.

However, in the case of the induction heating method, the present inventor surprisingly finds that when the heating is interrupted, paused, and then reheated, the heating efficiency characteristic returns to the original value as shown in FIG. I found it to grow. The present invention is
It is based on this discovery.

FIG. 3 is a graph for explaining a change in heating efficiency in the induction heating method when a rest period of time s is formed during application of an AC voltage. In the figure, the horizontal axis represents time and the vertical axis represents heating efficiency.

As can be seen from the figure, when the rest period s is formed during the application of the AC voltage to the induction coil, the heating efficiency becomes high.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an induction heating roller device in which the heating time of the heating roller is shortened in the induction heating system, a fixing device provided with the induction heating roller device, and an image forming apparatus.

The present invention also relates to an induction heating system,
Another object of the present invention is to provide an induction heating roller device, which is designed to save power for heating the heating roller, a fixing device including the induction heating roller device, and an image forming apparatus.

[0014]

According to another aspect of the present invention, there is provided an induction heating roller device, which comprises a heating roller which generates heat when an induction current flows when it is magnetically coupled to an induction coil, which is arranged so as to be magnetically coupled to the heating roller. An induction coil provided; an AC power supply for applying an AC voltage to the induction coil to energize the induction coil; and a control means for forming a rest period of a predetermined time in the AC voltage applied to the induction coil. It is characterized by being.

In the present invention and the following inventions, the definitions and technical meanings of terms are as follows unless otherwise specified.

<About the heating roller> The heating roller is
An induction current flows through the heating roller when the induction coil is magnetically coupled. In the case of the eddy current loss heating heat method, an eddy current is induced in the heating roller. Further, in the case of the transformer coupling heating system, the heating roller is provided with a secondary coil of a closed circuit, and during magnetic coupling, a secondary current is induced and flows mainly in the orbiting direction in the secondary coil. The secondary coil may have one turn or one turn or more. Further, the secondary coil can obtain high power transmission efficiency when the secondary side resistance value thereof is substantially equal to the secondary reactance. Note that the secondary side resistance value and the secondary reactance being “substantially equal” means that the secondary side resistance value is Ra, the secondary reactance is Xa, and α = Ra / X
When it is set to a, it can be set as the range which satisfy | fills Numerical formula 1. Further, the secondary side resistance value can be obtained by measurement. The secondary side reactance can be calculated.

[0017]

0.25 <α <4 Further, the heating roller can be arranged so that the secondary coil has a single or plural form. In the case of a single secondary coil, it is desirable to arrange the secondary coil so as to extend over almost the entire effective length along the axial direction of the heating roller. Further, when a plurality of secondary coils are arranged, it is desirable to disperse them in the axial direction of the heating roller.

Next, an example of the structure of the heating roller in the case of the transformer coupling heating method using the air core transformer coupling is shown below. In this configuration example, the heating roller is a roller base,
It comprises a first metal coating and a second metal coating. The roller base body is made of metal or heat resistant insulator.
In the case of a metal, any metal may be used as long as it has heat resistance and high mechanical strength, regardless of whether or not it has conductivity. However, Fe or Al is preferable in terms of workability and cost. Further, in the case of a heat resistant insulator, any insulator may be used as long as it is heat resistant and has high mechanical strength. However, it is preferably ceramics or glass. The first metal coating is disposed on the surface of the roller base. And
A secondary coil of a closed circuit is formed, and this secondary coil is air-core transformer-coupled with the primary coil. Further, the following materials and manufacturing methods can be adopted for the first metal film in order to obtain a desired secondary side resistance value. When formed by electroplating, vapor deposition or sputtering, C
It is preferable to use a material selected from the group of u, Ni, Ag and Al. On the other hand, thick film forming method (application +
When formed by firing), Cu, Ag and Ag
It is preferable to use a material selected from the group consisting of + Pd. The second metal coating is made of a metal having oxidation resistance and covers the surface of the first metal coating. That is, the second metal coating protects the surface of the first metal coating and prevents oxidation. The surface of the second metal coating may be oxidized. Suitable metals include Zn, Sn, Ni and Ti, and the second metal film can be formed by electroplating, vapor deposition, sputtering, thick film forming method and the like. The first and second metal coating films can be provided on either or both of the outer surface and the inner surface of the roller base. Also, the first and second
The metal coating of may be composed of a plurality of layers.

Further, in order to obtain a more practical heating roller, the following constitutions are allowed to be added as necessary.

1 Protective Layer The protective layer can be provided as necessary for mechanical protection and electrical insulation of the heating roller, or for improving elastic contact property or toner releasability. Glass can be used as the constituent material of the protective layer for the former, and synthetic resin can be used as the constituent material of the protective layer for the latter.

2 Shape of the heating roller If desired, a crown can be formed on the heating roller. The crown may have either a drum shape or a barrel shape.

3 Rotating Mechanism of Heating Roller The mechanism for rotating the heating roller can be selected from known configurations as appropriate and employed.

4 Regarding the Temperature Sensor In order to control the temperature of the heating roller, the temperature sensor can be brought into thermal contact with the heating roller at a proper position. When a plurality of induction coils are arranged dispersedly in the axial direction of the heating roller, a plurality of temperature sensors can be arranged so as to be sensitive to the temperature of the position facing each induction coil. Then, by controlling the electric power supplied from the induction coil according to the temperature of the axial region, it is possible to improve the temperature uniformity of the heating roller.

<Induction coil> The induction coil is
It is means for magnetically coupling to the heating roller and transmitting AC power to the heating roller. Therefore, although the induction coil may be disposed at the inside or outside of the heating roller with respect to the heating roller, the induction coupling facilitates magnetic coupling. In the case of the eddy current loss heating method, the induction coil is arranged so as to generate a magnetic flux so as to be orthogonal to the axis of the heating roller. On the other hand, in the case of the transformer coupling heating method, the induction coil is arranged so as to generate a magnetic flux in the axial direction of the heating roller.

Further, a single induction coil or a plurality of induction coils are arranged regardless of the eddy current loss heating method or the transformer coupling heating method. When using a plurality of induction coils, the plurality of induction coils can be connected in parallel or in series to a single AC power source. In addition, if a plurality of induction coils are connected to respective AC power sources, it becomes possible to adjust the input power individually or in groups. Furthermore, when using a plurality of induction coils, it is preferable to disperse them along the axial direction of the heating roller. in this case,
There may be an appropriate gap between adjacent induction coils, or if there is no problem with insulation, they may partially overlap.

When the induction coil is energized, that is, excited by an AC power source, it generates a magnetic field, and the magnetic field interlinks with the heating roller to generate an induction current in the heating roller. That is, the induction coil and the secondary coil of the heating roller are magnetically coupled to each other via the alternating magnetic field. In the case of the transformer coupling heating method, it functions as a primary coil and a secondary coil of the transformer. It should be noted that even if an eddy current is generated in the secondary coil when a part of the magnetic flux passes through the secondary coil, it does not matter if most of the secondary current flows in the circumferential direction. Therefore, the induction coil is a means for transferring high frequency power to the secondary coil of the heating roller.

Further, as the induction coil, one acting as a core can be used if necessary. When air core transformer coupling is performed, the core is not used. The induction coil may be stationary with respect to the rotating heating roller, or may be rotated together with the heating roller or separately. When rotating, a rotary current collecting mechanism may be interposed between the high frequency power supply and the induction coil. Further, the "air-core transformer coupling" is meant to include not only a complete air-core transformer coupling but also a transformer coupling that can be regarded as a substantially air-core. For example, the induction coil does not have a magnetic material inside.

<About AC Power Supply> The AC power supply is a means for applying an AC voltage to the induction coil to energize the induction coil. The output frequency of the AC power supply is not basically limited, but in the case of a transformer coupling heating method utilizing air-core transformer coupling, it is convenient that it is configured to output a high frequency of 100 kHz or more. Good.
This is because by setting the high frequency to 100 kHz or more, the Q of the induction coil can be increased and the power transmission efficiency can be further enhanced. When the power transmission efficiency is high, the overall efficiency of heating is high, and power can be saved. Note that compatible active devices (for example,
MOSFETs can be used as described below. From the viewpoints of economic efficiency and ease of suppressing high frequency noise,
A high frequency of 1 to 4 MHz is preferable.

In order to generate an alternating current of a desired frequency, it is practical to directly or indirectly convert a direct current or a low frequency alternating current into an alternating current by using an active element such as a semiconductor switch element. In order to obtain AC power of a required frequency from the low frequency AC, it is preferable to convert the low frequency AC into DC by using a rectifying means. The direct current may be a smoothed direct current formed by using a smoothing circuit or may be a non-smoothed direct current. Circuit elements such as amplifiers and inverters can be used to convert direct current to alternating current. As the amplifier, for example, a class E amplifier having high power conversion efficiency can be used. Also, a half-bridge type inverter or the like can be used. Furthermore, as an active element,
A MOSFET having excellent frequency characteristics is suitable. A plurality of AC power supply circuits may be connected in parallel, and the AC outputs of the AC power supply circuits may be combined and then applied to the induction coil. As a result, the output of each AC power supply circuit can be small even with the desired power, so
Using a MOSFET, it is suitable for high frequencies and can generate alternating current at low cost and efficiently.

Further, when using a plurality of induction coils,
The AC power supply can be common to a plurality of induction coils. Then, by variably configuring the frequency of the output of the AC power supply, it becomes possible to individually control the electric power supplied to each induction coil. But if you want,
A frequency-variable AC power source may be separately provided for each induction coil.

Furthermore, if necessary, for example, the input power at the time of start-up can be made larger than that at the time of normal operation to perform rapid heating.

<Regarding Control Means> The control means is means for forming a rest period of a predetermined time in at least the AC voltage applied to the induction coil. That is, the AC voltage is intermittently applied to the heating roller by forming the rest period. The rest period is preferably set before the temperature rise of the heating roller is saturated, in other words, before the heating efficiency is considerably reduced. Further, the set number of pause periods may be either once or plural times. Further, the time width of the rest period is not particularly limited, but it is preferable to be as short as possible within a range where the heating efficiency is restored. To increase the heating rate to the target temperature,
The pause period is preferably formed when the heating efficiency is somewhat high rather than when the heating efficiency is extremely low. As a guide, for example, it may be set to a time higher than the heating efficiency of the halogen bulb. Further, the rest period may be formed while maintaining 50% or more of the initial heating efficiency.

Next, the control means may have any other specific configuration as long as a rest period is formed in the AC voltage applied to the induction coil. For example, the AC oscillating circuit is directly controlled to intermittently oscillate, or a switch is interposed between an AC generating circuit that continuously generates an AC and an induction coil to open or close the switch. be able to.

Further, the control means allows the alternating current output to be constant or variable. It can be configured to perform duty control, that is, PWM control in order to control the AC output.

<Other Configurations> Although not an essential component of the present invention, a more effective induction heating roller device can be obtained by selectively implementing the following configurations, if desired.

1. Regarding Reel Frame In order to maintain the predetermined shape and position of the induction coil in a predetermined manner, the induction coil can be supported by using a winding frame made of a material having a dielectric loss as small as possible. . In this case, the reel is
It may be hollow or the inside may be solid. A winding groove for aligned winding and an axial groove for accommodating the feeding lead wire can be formed in the winding frame. But,
It is also possible to maintain the plural induction coils in a predetermined shape by directly molding or adhering the induction coils with synthetic resin or glass material instead of the winding frame.

2 Regarding Power Feed Lead Wire A power feed lead wire can be used to feed AC power from an AC power source to the induction coil, or in addition to this, to connect with a capacitor. The power supply lead wire is preferably arranged at a position close to the inner surface or the outer surface of the induction coil. When the power supply lead wire is passed inside the induction coil, if the power supply lead wire is close to the center axis of the induction coil, the magnetic flux interlinking with the power supply lead wire will increase, resulting in eddy current loss inside the power transfer. This is not preferable because it lowers the efficiency. On the other hand, with the above configuration, the magnetic flux interlinking with the power supply lead wire is reduced, so that the reduction in power transmission efficiency is relatively suppressed.

3. Capacitor in parallel with induction coil A capacitor can be connected in parallel with the induction coil. The capacitor forms a resonant circuit with the induction coil. In this case, the position where the capacitor is provided is not particularly limited. If the heat resistant temperature of the condenser and the space inside the heating roller are allowed, it may be placed inside the heating roller close to the induction coil, or the condenser may be placed away from the induction coil and heating roller. Good.

4 About Warm-up Control During the warm-up period after start-up, that is, when power supply is started, the heating roller can be controlled to rotate at a lower rotation speed than that in normal operation.

5. Temperature Control of Heating Roller In order to keep the temperature of the heating roller constant within a predetermined range, for example, 200 ° C., a heat sensitive element can be brought into thermal contact with the surface of the heating roller. Then, the heat sensitive element is connected to the temperature control circuit. As the heat sensitive element, a thermistor having a negative temperature characteristic or a non-linear resistance element having a positive temperature characteristic can be used.

6 Conveying Sheet When the heating roller is used to heat the object to be heated, the heating roller may be configured to directly contact the object to be heated. It can be configured to intervene. In this case, the transport sheet is allowed to have an endless shape or a roll shape. By using the transport sheet, it becomes possible to smoothly heat and transport the object to be heated.

<Operation of the Present Invention> When an AC voltage is applied to the induction coil, an AC wave magnetic field is generated from the induction coil and magnetically coupled to the heating roller. That is, the induction coil serves as a primary coil, and magnetic coupling is performed between the induction coil and the heating roller. As a result, an induced current flows through the heating roller. Then, Joule heat is generated by the induced current, and the temperature of the heating roller rises. Also, in the transformer-coupled heating method of the air-core transformer coupled type, 100 k
At high frequencies above Hz, power transfer efficiency increases,
For example, it will be 95% or more. However, in the case of the induction heating method, the heating efficiency of the heating roller gradually decreases with the passage of time.

Next, when the rest period is formed in the application of the AC voltage to the induction coil by the action of the control means, the heating operation of the heating roller is stopped during the rest period. When the rest period ends and the AC voltage is applied to the induction coil again, heating is restarted. The heating at this time is restored to a high value for the heating efficiency of the heating roller, and gradually decreases over time. Therefore, by forming the rest period, the temperature rise of the heating roller can be made faster than in the case where the alternating voltage is continuously applied without forming the rest period.

Further, by increasing the heating rate up to the desired temperature, it becomes possible to save the input power.

The induction heating roller device according to the invention of claim 2 is
A heating roller that generates heat when an induction current flows when magnetically coupled to an induction coil; an induction coil that is magnetically coupled to the heating roller; and an AC voltage is applied to the induction coil to energize the induction coil. AC power source for controlling the AC voltage applied to the induction coil so that the heating efficiency by applying the AC voltage after the rest period is higher than that before the rest period. There is.

According to the present invention, the condition to be satisfied during the rest period is defined by the heating efficiency.

Thus, in the present invention, the above-described structure makes it possible to shorten the heating time of the heating roller to the same level as or more than the case where the idle period is not formed. In addition, power consumption can be saved by appropriately setting the pause period.

The induction heating roller device according to the third aspect of the invention is
A heating roller that generates heat when an induction current flows when magnetically coupled to an induction coil; an induction coil that is magnetically coupled to the heating roller; and an AC voltage is applied to the induction coil to energize the induction coil. An alternating current power supply for controlling at least a room temperature to a target temperature; and a control means for forming a rest period of a predetermined time in the alternating voltage applied to the induction coil.

The present invention defines a configuration for forming a rest period of AC voltage application during so-called warm-up.
In addition, if necessary, after the target temperature is reached, it is not necessary to form a pause period for applying the AC voltage.

Thus, in the present invention, the warm-up time can be shortened.

The induction heating roller device according to the invention of claim 4 is
A heating roller that generates heat when an induction current flows when magnetically coupled to an induction coil; an induction coil that is magnetically coupled to the heating roller; and an AC voltage is applied to the induction coil to energize the induction coil. An AC power supply for controlling the target temperature control between the temperature upper limit and the temperature lower limit, and a control unit for forming a quiescent period of a predetermined time in the AC voltage applied to the induction coil. I am trying.

The present invention defines a configuration in which after the target temperature is reached, a rest period is formed in the AC voltage application while maintaining the target temperature. That is, in the present invention, when the temperature of the heating roller reaches the target temperature and then the application of the AC voltage is intermittently performed, the temperature is controlled to be always between the temperature upper limit and the temperature lower limit of the target temperature. A pause period is formed when an AC voltage is applied. It should be noted that, if necessary, it is not necessary to form a rest period in the application of the AC voltage when warming up.

Thus, in the present invention, the AC voltage is applied when the temperature reaches the lower limit of the target temperature. However, since the period is formed during the application of the AC voltage, the heating efficiency is high for the reason described above. Become. Therefore, the heating speed of the heating roller is increased, and the time required to reach the temperature upper limit and the temperature upper limit is shortened. In addition, since the heating time is shortened, power can be saved.

The induction heating roller device according to the fifth aspect of the invention is
A heating roller that generates heat when an induction current flows when magnetically coupled to an induction coil; a plurality of induction coils that are distributed along the axial direction of the heating roller and are magnetically coupled to the heating roller. An AC power supply for applying an AC voltage to each induction coil to energize a plurality of induction coils; and a control means for forming a quiescent period for a predetermined time in the AC voltage applied to a selected induction coil among the plurality of induction coils. It is characterized by having.

The present invention defines a configuration suitable for heating the heating roller by partially selecting it in the axial direction. That is, by disposing a plurality of induction coils dispersed along the axial direction of the heating roller, it becomes possible to partially heat the heating roller in the axial direction. Because, in the heating roller, a portion approaching the induction coil to which the AC voltage is applied and energized is strongly heated, so a plurality of induction coils are dispersedly arranged in the axial direction of the heating roller, By selectively applying an AC voltage to each induction coil to energize it, the heating roller can be selectively heated along its axial direction.

Further, in order to partially control the temperature of the heating roller, a temperature sensor such as a thermistor is arranged so as to thermally contact with the surface of the heating roller facing each induction coil, and The temperature sensor can be connected to an output control circuit of an AC power supply that applies a high frequency voltage to each induction coil. Thereby, the temperature of the heating roller can be partially maintained at the desired temperature.

When heating a region of the heating roller facing the plurality of induction coils, an AC voltage is applied to each induction coil at the same time during warm-up while forming a rest period, and after reaching the target temperature. By alternately switching a plurality of induction coils, it is possible to form a rest period in the application of the AC voltage to each induction coil. However, if necessary, the idle period may be simultaneously formed for each induction coil even after the target temperature is reached. Also, if desired, the idle period may not be formed during warm-up.

Thus, in the present invention, since the heating roller can be partially heated along its axial direction, when the induction heating roller device is used for fixing toner,
The heating area can be selected according to the size of the image forming paper, and heating of the selected area of the heating roller can be speeded up.

The induction heating roller device according to the invention of claim 6 is
In the induction heating roller device according to any one of claims 1 to 5, the control means duty-controls the AC power supply, and an off period of the duty control acts as the idle period.

The present invention defines a structure for effectively forming a rest period of AC voltage application. That is, the AC output can be controlled as desired by controlling the duty of the AC voltage at an appropriate cycle. AC output control is
It may be made constant by performing feedback control, or may be controlled to a desired value according to an external signal. The duty control may be performed by adopting a known circuit configuration.

Further, due to the duty control by the control means, the AC voltage is applied during the ON period, and the AC voltage is not applied during the OFF period, so that it becomes a pause period.

Thus, in the present invention, the heating of the heating roller can be speeded up by the idle period formed by the OFF period of the duty control while the AC output is controlled by the duty control as desired.

According to a seventh aspect of the present invention, there is provided a fixing device main body having a pressure roller; a heating roller is provided in pressure contact with the pressure roller of the fixing device main body, and a toner image is formed between the two rollers. The induction heating roller device according to any one of claims 1 to 6, wherein the induction heating roller device is arranged so as to fix the toner image while transporting the formed recording medium.

In the present invention, the "main body of the fixing device" means
The rest of the fixing device excluding the induction heating roller device.

The pressure roller and the heating roller may be directly in pressure contact with each other, but may be indirectly in contact with each other via a conveying sheet or the like if necessary. The transport sheet may be endless or roll-shaped.

Thus, in the present invention, the toner image can be fixed at a high speed while the recording medium having the toner image formed thereon is conveyed while being sandwiched between the heating roller and the pressure roller.

An image forming apparatus according to an eighth aspect of the present invention includes an image forming apparatus main body having an image forming means for forming a toner image on a recording medium; and a toner image on the recording medium fixed to the image forming apparatus main body. And a fixing device according to claim 7.

In the present invention, the "image forming apparatus main body" means the remaining portion of the image forming apparatus excluding the fixing device. The image forming unit is a unit that forms an image on a recording medium to form image information by an indirect method or a direct method. The "indirect method" means a method of forming an image by transfer.

The image forming apparatus corresponds to, for example, an electrophotographic copying machine, a printer or a facsimile.

As the recording medium, for example, a transfer material sheet, a printing paper, an electrofax sheet, an electrostatic recording sheet or the like is applicable.

Thus, according to the present invention, an image forming apparatus suitable for a high speed type can be obtained.

[0072]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. 4 to 9 show a first embodiment of an induction heating roller device of the present invention, FIG. 4 is a circuit block diagram showing an overview of the whole, and FIG. 5 is a partially cutaway central sectional front view of an induction coil and a heating roller. FIG. 6, FIG. 6 is a cross-sectional view of the heating roller, FIG. 7 is a circuit diagram mainly showing a power supply circuit, FIG. 8 is a waveform diagram showing a rest period formed in the AC voltage applied to the induction coil, and FIG. 9 is induction heating. It is a temperature change figure showing temperature control of a roller device. In this embodiment, the induction heating roller device is a transformer-coupled heating system in which an air-core transformer is coupled. In each figure, the induction heating roller device is
Heating roller HR, three induction coils IC1, IC2, I
C3 includes three capacitors C1, C2, C3 and an operating circuit OC. Note that the three induction coils IC1, IC2, IC3 and the three capacitors C1, C2, C include three resonance circuits RC1, RC2, R.
C3 is formed and is energized by a high frequency power supply HFS described later.

The configuration of each of the above components will be described in detail below.

<Regarding Heating Roller HR> The heating roller HR comprises a roller base 1, a first metal coating ws, a second metal coating ns and a protective layer 2, and is rotationally driven by a rotating mechanism RM. To be done.

The roller base 1 is made of a Fe-cast cylinder, and has a length of 300 mm and a thickness of 3 mm, for example.

The first metal film ws is a cylindrical film-shaped film 1 made of a Cu film formed by electroplating.
It consists of a turn coil, and on the outer surface of the roller base 1,
It is arranged over almost the entire effective length in the axial direction.
The thickness of the first metal coating ws is equal to the heating roller HR.
The secondary side resistance value in the orbiting direction is set to 1Ω, which is almost the same value as the secondary reactance.

The second metal film ns is a Zn film formed by electroplating and covers the entire surface of the first metal film ws. The secondary side resistance values of the roller base body 1 and the second metal coating ns are set so as to be values greatly deviated from the secondary reactance.

The protective layer 2 is made of fluororesin and is formed by coating the outer surface of the second metal film ns.

The rotating mechanism RM is a mechanism for rotating the heating roller HR, and is constructed as follows. That is, as shown in FIG. 2, the first end member 3
A, a second end member 3B, a pair of bearings 4, 4, a bevel gear 5, a spline gear 6, and a motor 7 are provided.

The first end member 3A includes a cap portion 3a,
It consists of a drive shaft 3b and a tip 3c. Cap part 3a
2 is fitted to the left end of the heating roller HR in FIG. 2 from the outside, and is fixed to the heating roller HR by using a push screw (not shown).
Supports the left edge of. The drive shaft 3b is the cap portion 3a.
Projects outward from the center of the outer surface of the. Point 3c
From the center of the inner surface of the cap portion 3a to the cap portion 3a
Protruding inward.

The second end member 3B comprises a ring portion 3d. The ring portion 3d supports the right end of the heating roller HR by fitting the right end of the heating roller HR in FIG. 2 from the outside and fixing it to the heating roller HR using a push screw (not shown). There is.

One of the pair of bearings 4 and 4 rotatably supports the outer surface of the cap portion 3a of the first end member 3A. The other rotatably supports the outer surface of the second end member 3B. Therefore, the heating roller HR has the first and second end members 3A and 3B fixed to both ends thereof.
And a pair of bearings 4 and 4 are rotatably supported.

The bevel gear 5 is mounted on the drive shaft 3b of the first end plate 3A. The spline gear 6 meshes with the bevel gear 5. The rotor shaft of the motor 7 is directly connected to the spline gear 5.

<Three induction coils IC1, IC2, IC
About 3> Three induction coils IC1, IC2, IC
As shown in FIG. 4, 3 is magnetically coupled to the secondary coil ws of the heating roller HR. Then, as shown in FIG.
The winding frame 8 is wound around the heating roller HR so as to be dispersed in the axial direction of the heating roller HR, and is wound in the circumferential direction of the heating roller HR. In addition, a pair of power supply lead wires 9 are connected in parallel via impedances Z, respectively.

The bobbin 8 is made of a fluororesin cylinder and has a recess 8a, a support 8b and a wire groove 8c. The recess 8a is formed at the center of the tip of the coil bobbin 8 and is rotatably engaged with the rotating mechanism RM. The support portion 8b is formed at the base end of the winding frame 8 and is fixed to a fixing portion (not shown). The wire groove 8c is formed in a part of the outer surface of the winding frame 8 in a gutter shape along the axial direction, and accommodates the power supply lead wire 9 therein. The power supply lead wire 9
3, is housed in the wire groove 1c, led out to the outside from the base end side of the winding frame 8, and connected to the output end of the high frequency power supply HFS via a coaxial cable.

Then, the three induction coils IC1 and IC
2, IC3 are used in a stationary state, the power supply lead wire 9 is housed in the wire passage groove 1c, and the induction coils IC1, IC2,
Since it is close to the IC 3, there is almost no linkage of magnetic flux, so that almost no eddy current loss occurs in the power supply lead wire 9.
On the other hand, the three induction coils IC1, IC2, IC3 are inserted into the heating roller HR from the ring portion 3d of the second end member 3B, and the recess 1a formed at the tip of the winding frame 8 is the first. The support portion 1b formed at the base end as described above is engaged with the sharp end portion 3c of the end plate 3A and is fixed to the fixing portion, so that the support portion 1b is supported coaxially with the heating roller HR and is heated. Even if the roller HR rotates, it remains stationary.

<Regarding Three Capacitors C1, C2, C3> As shown in FIGS. 1 and 4, the three capacitors C1, C2, C3 have three induction coils IC1, IC.
2, 3 connected in parallel to IC3, three resonance circuits RC1, R
C2 and RC3 are formed. In FIG. 4, R
_ws represents the equivalent resistance of the closed circuit formed by the secondary coil _ws of the heating roller HR.

<Regarding Three Resonant Circuits RC1, RC2, RC> Of the three resonant circuits RC1, RC2, RC3, RC1 and RC2 have their resonance points in FIG.
Curve A is, and RC3 is curve B. That is, the resonance points of the curves A and B are deviated from each other.

<Regarding the operating circuit OC> The operating circuit OC
As shown in FIG. 4 and FIG. 7, is composed of a DC power supply DC, an AC power supply HFS, and a control means CC.

(About AC power supply HFS) AC power supply H
The FS supplies high frequency power to each induction coil IC1, IC2, IC3, and its input end is connected to the output end of the DC power supply DC. The input end of the DC power supply DC is connected to the low frequency AC power supply AS.

As shown in FIG. 7, the AC power supply HFS includes a high frequency filter HFF, a variable frequency high frequency oscillator OSC, a gate drive circuit GDC, a half bridge inverter main circuit HBI, a load circuit LC and an external signal source OSS. It is composed by.

The high frequency filter HFF includes a DC power supply DC and a half bridge type inverter main circuit HBI which will be described later.
The high-frequency alternating current is prevented from flowing out to the low-frequency alternating-current power supply AS side by interposing between the two.

The high frequency oscillator OSC is of variable oscillation frequency, generates a high frequency signal of a predetermined frequency, and inputs it to the drive circuit DC.

The gate drive circuit GDC is composed of a preamplifier and amplifies the high frequency signal sent from the high frequency oscillator OSC and outputs a drive signal.

Half-bridge type inverter main circuit HBI
Are connected in series between DC power source DC output terminals, which will be described later, and are excited by a drive signal of the drive circuit DC to switch alternately, and a pair of MOSFETs Q1 and Q2 and a pair of MOSFET Q.
1, Q2, and capacitors C4 and C5 connected in parallel, and converts the DC output of the DC power supply DC into a high frequency AC voltage having a substantially rectangular wave. The capacitors C4 and C5 perform a high frequency bypass action during the operation of the inverter.

The load circuit LC is a DC cut capacitor C
6, inductor L1, three capacitors C1, C2, C
It is composed of three. DC cut capacitor C6
Prevents the direct current component from flowing into the load circuit LC from the direct current power supply DC side via the pair of MOSFETs Q1 and Q2. Inductor L1 and three capacitors C1, C2, C3
Form a series resonance circuit to form three induction coil ICs.
The AC voltage applied to both ends of IC1, IC2 and IC3 is shaped into a sine wave. 3 by waveform shaped AC voltage
The induction coils IC1, IC2, IC3 are energized.

The external signal source OSS is for controlling the output frequency of the AC power supply HFS by being controlled by the sheet width detecting means (not shown), and controlling the oscillator OSC.
It functions to change its oscillation frequency.

(About DC power supply DC) DC power supply DC
Is a rectifier circuit, the input end of which is connected to the low-frequency AC power supply AS to convert the low-frequency AC voltage into a non-smoothed DC voltage,
Output from the DC output terminal.

(Regarding Low Frequency AC Power Supply AS) The low frequency AC power supply AS is, for example, a 100V commercial AC power supply.

(Regarding Control Means CC) Control Means CC
Is for controlling the generation of an AC voltage to form a temporary rest period, and functions to stop the oscillator OSC.

<Operation of the induction heating roller device>
The low frequency AC voltage of the low frequency AC power supply AS is the DC power supply DC
Is converted into a DC voltage by the AC power supply HFS, and then converted into a high frequency AC voltage by the AC power supply HFS and applied to the three induction coils IC1, IC2, IC3 in the stationary state. As a result, 3
Since the two induction coils IC1, IC2, IC3 are energized, the first metal coating ws of the heating roller HR, which is magnetically coupled, generates heat due to the secondary current flowing therethrough in the circumferential direction, and the temperature rises. To do.

Further, as shown in FIG. 8 during the application of the AC voltage, the rest period s is formed by the control means CC,
The application of the AC voltage is temporarily interrupted. When the AC voltage is applied again after the end of the rest period s, the heating efficiency is restored and becomes higher, so that the heating rate of the heating roller HR becomes higher.

Further, in the induction heating roller device of the present embodiment, a temperature sensor (not shown) is arranged in thermal contact with the heating roller HR, and the AC power supply HFS is controlled. Therefore, as shown in FIG. Temperature controlled. That is,
The heating roller HR is heated from room temperature to a target temperature as initial heating when warming up. Then, when the target temperature is reached, the application of the AC voltage is controlled so as to be within the range between the temperature upper limit and the temperature lower limit as the target temperature management. The rest period during the application of the AC voltage is formed in both the initial heating and the target temperature control.
Speed of temperature control increases.

FIG. 10 is a conceptual diagram showing a second embodiment of the induction heating device of the present invention. In the figure, the same parts as those in FIGS. 4 and 7 are designated by the same reference numerals and the description thereof will be omitted. In this embodiment, the induction heating roller device is configured by an eddy current loss heating method.

Therefore, the three induction coils IC1, I
C2 and IC3 are arranged so that the magnetic fluxes generated from them cross the heating roller at a right angle. In addition,
S1, S2, and S3 are temperature sensors, respectively, which are arranged at portions of the heating roller HR that face the induction coils IC1, IC2, and IC3, and the AC power supply HFS.
Is controlled to individually control the AC voltage applied to each induction coil IC1, IC2, IC3 to control the temperature of each part as desired.

FIG. 11 is a vertical sectional view showing an embodiment of the fixing device of the present invention. In the figure, 21 is an induction heating roller device, 22 is a pressure roller, 23 is a recording medium, 24 is toner, 25 is a mount, and IC is an induction coil.

The induction heating roller device 21 uses the first embodiment shown in FIGS. 4 to 9.

The pressure roller 22 is the induction heating roller device 2
The heating roller HR is arranged in pressure contact with the first heating roller HR, and conveys the recording medium 23 while narrowing the pressure between the two.

An image is formed on the recording medium 23 by attaching the toner 24 to the surface thereof.

The pedestal 25 mounts the above components (excluding the recording medium 23) in a predetermined positional relationship.

Then, in the fixing device, the recording medium 23 on which the toner 24 is attached to form an image is inserted between the heating roller HR and the pressure roller 22 of the induction heating roller device 21 and conveyed. At the same time, the toner 24 is heated and melted by the heat of the heating roller HR, and thermal fixing is performed.

FIG. 12 is a conceptual sectional view of a copying machine as an embodiment of the image forming apparatus of the present invention. In the figure, 31 is a reading device, 32 is an image forming unit, 33 is a fixing device, and 34 is an image forming device case.

The reading device 31 optically reads the base paper and forms an image signal.

The image forming means 32 forms an electrostatic latent image on the photosensitive drum 32a based on the image signal, attaches toner to the electrostatic latent image to form a reverse image, and records it on paper or the like. Transfer to a medium to form an image.

The fixing device 33 has the structure shown in FIG. 11, and heats and melts the toner adhering to the recording medium to heat-fix it.

The image forming apparatus case 34 accommodates the above-mentioned devices and means 31 to 33, and is provided with a carrying device, a power supply device, a control device, and the like.

[0117]

According to the first aspect of the present invention, a heating roller that generates heat when an induction current flows when it is magnetically coupled to an induction coil described later, and an induction coil disposed so as to be magnetically coupled to the heating roller. By including an AC power supply for applying an AC voltage to the induction coil to energize the induction coil and a control means for forming a pause period of a predetermined time in the AC voltage applied to the induction coil, the pause period ends. Then, when the AC voltage is applied to the induction coil again, the heating efficiency of the heating roller is restored to a high value. It is possible to provide an induction heating roller device capable of speeding up.

According to the second aspect of the present invention, a heating roller which generates heat when an induction current flows when it is magnetically coupled to the induction coil, an induction coil arranged to be magnetically coupled to the heating roller, and an AC voltage. Control to form a rest period in the AC voltage applied to the induction coil so that the heating efficiency by applying the AC voltage after the rest period is higher than that before the rest period. When the alternating current voltage is applied to the induction coil again after the end of the rest period, the heating efficiency of the heating roller is restored to a high value. It is possible to provide the induction heating roller device which is faster than the case where the AC voltage is continuously applied without forming the.

According to the third aspect of the present invention, a heating roller that generates heat when an induction current flows when magnetically coupled to the induction coil described later, an induction coil arranged to be magnetically coupled to the heating roller, and an AC voltage. And an AC power supply for energizing the induction coil by applying to the induction coil, and a control means for forming a pause period of a predetermined time in the high frequency voltage applied to the induction coil when heating from at least room temperature to a target temperature. Thus, when heating from the room temperature to the target temperature, the temperature of the heating roller rises faster than in the case where the alternating voltage is continuously applied without forming a rest period, and thus it is possible to provide the induction heating roller device.

According to the fourth aspect of the present invention, the heating roller generates heat when an induction current flows when it is magnetically coupled to the induction coil, an induction coil arranged to be magnetically coupled to the heating roller, and an AC voltage. Is applied to the induction coil to energize the induction coil, and a quiescent period of a predetermined time is formed in the AC voltage applied to the induction coil when the target temperature control is performed at least between the upper temperature limit and the lower temperature limit. By including the control means, when performing the target temperature control between the temperature upper limit and the temperature lower limit, the temperature rise of the heating roller is more continuously applied than the case where the alternating voltage is applied without forming a pause period. It is possible to provide an induction heating roller device that speeds up.

According to the fifth aspect of the present invention, the heating roller that generates heat when an induction current flows when it is magnetically coupled to the induction coil, and the heating roller are distributed in the axial direction of the heating roller so as to be magnetically coupled. A plurality of induction coils installed, an AC power supply that applies an AC voltage to each induction coil to energize the plurality of induction coils, and a control that forms a pause period of a predetermined time for the AC voltage applied to the plurality of induction coils And an induction heating roller device that speeds up heating of selected areas of the heating roller.

According to the invention of claim 6, the control means duty-controls the AC power source, and the OFF period of the duty control acts as the idle period, thereby controlling the AC output by the duty control as desired. It is possible to provide an induction heating roller device that speeds up heating of the heating roller by the idle period formed by the duty control off period.

According to the seventh aspect of the invention, the fixing device main body provided with the pressure roller and the heating roller are placed in pressure contact with the pressure roller of the fixing device main body so that a toner image is formed between the two rollers. 7. The induction heating roller device according to claim 1, wherein the induction heating roller device is arranged so as to fix the toner image while being transported with the recording medium sandwiched therebetween. It is possible to provide a fixing device having the above effect.

According to the invention of claim 8, an image forming apparatus main body having an image forming means for forming a toner image on the recording medium, and a toner image on the recording medium fixed to the image forming apparatus main body. By including the fixing device according to item 7, it is possible to provide an image forming apparatus having the effects of claims 1 to 6.

[Brief description of drawings]

FIG. 1 is a graph showing temperature rise characteristics for explaining the temperature rise of an induction heating type heating roller device together with that of a halogen bulb.

FIG. 2 is a graph showing heating efficiency characteristics as well.

[Fig. 3] Time s for applying an AC voltage in the induction heating method
Graph explaining the change in heating efficiency when a rest period is formed

FIG. 4 is a circuit block diagram showing an overall outline of a first embodiment of an induction heating roller device of the present invention.

FIG. 5 is a partially cutaway central sectional front view of the induction coil and the heating roller.

FIG. 6 is a transverse sectional view of the heating roller.

FIG. 7 is a circuit diagram mainly showing a power supply circuit.

FIG. 8 is a waveform diagram showing a dwell period formed in an AC voltage similarly applied to the induction coil.

FIG. 9 is a temperature change diagram showing the temperature control of the induction heating roller device.

FIG. 10 is a conceptual diagram showing a second embodiment of the induction heating device of the present invention.

FIG. 11 is a vertical sectional view showing an embodiment of a fixing device of the present invention.

FIG. 12 is a conceptual sectional view of a copying machine as an embodiment of the image forming apparatus of the present invention.

[Explanation of symbols]

CC ... Control means, HFS ... AC power supply, HR ... Heating roller, IC1 ... Induction coil, IC2 ... Induction coil, IC3
… Induction coil

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2H033 AA30 AA32 BA25 BA27 BA32                       BB03 BB04 BB13 BB18 BB28                       BE06 CA07 CA17 CA30 CA45                       CA46 CA48                 3K059 AA08 AB19 AD02 AD03 AD07                       CD05

Claims (8)

[Claims] 1. A heating roller that generates heat when an induction current flows when magnetically coupled to an induction coil described below; an induction coil disposed so as to be magnetically coupled to the heating roller; and an AC voltage is applied to the induction coil. An induction heating roller device, comprising: an AC power supply for energizing the induction coil; and a control means for forming an idle period of a predetermined time in the AC voltage applied to the induction coil. 2. A heating roller, which generates heat when an induction current flows when magnetically coupled to an induction coil described below; an induction coil arranged so as to be magnetically coupled to the heating roller; and an AC voltage is applied to the induction coil. An AC power supply for energizing the induction coil; and a control means for forming a rest period in the AC voltage applied to the induction coil so that the heating efficiency by applying the AC voltage after the rest period is higher than that before the rest period. An induction heating roller device characterized in that 3. A heating roller that generates heat when an induction current flows when magnetically coupled to an induction coil described below; an induction coil arranged so as to be magnetically coupled to the heating roller; and an AC wave voltage is applied to the induction coil. AC power supply for energizing the induction coil;
An induction heating roller device, comprising: a control unit that forms a rest period of a predetermined time in an AC voltage applied to an induction coil when heating from at least room temperature to a target temperature. 4. A heating roller that generates heat when an induction current flows when magnetically coupled to an induction coil described below; an induction coil disposed so as to be magnetically coupled to the heating roller; and an AC voltage is applied to the induction coil. An AC power supply for energizing the induction coil; and a control means for forming a rest period of a predetermined time in the AC voltage applied to the induction coil when performing the target temperature control between at least the upper temperature limit and the lower temperature limit. An induction heating roller device characterized in that 5. A heating roller that generates heat when an induction current flows when magnetically coupled to an induction coil described later; distributed along the axial direction of the heating roller and magnetically coupled to the heating roller. A plurality of induction coils; an AC power supply that applies an AC voltage to each induction coil to energize the plurality of induction coils; and a pause period of a predetermined time in the AC voltage that is applied to a selected induction coil among the plurality of induction coils An induction heating roller device comprising: control means; 6. The induction heating roller device according to claim 1, wherein the control means duty-controls the AC power supply, and an off period of the duty control acts as the idle period. . 7. A fixing device main body provided with a pressure roller; a heating roller is provided in pressure contact with the pressure roller of the fixing device main body, and a recording medium on which a toner image is formed is sandwiched between both rollers. A fixing device comprising: the induction heating roller device according to any one of claims 1 to 6, which is arranged so as to fix the toner image while being conveyed. 8. An image forming apparatus main body comprising an image forming means for forming a toner image on a recording medium; a fixing device according to claim 7, which is disposed in the image forming apparatus main body to fix the toner image on the recording medium. An image forming apparatus comprising: