JP2002196613A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device provided with a fixing device using an electromagnetic induction heating system by which the high speed start-up of a device is completed and also energy saving is attained. SOLUTION: This fixing device using the electromagnetic induction heating system possesses a temperature controlling means to perform control so as to set the temperature of the fixing device at temperature at a printing time and an input quantity controlling means to perform control so that electric power input to an electromagnetic induction heat generating member is made constant in a normal state, and a fixing means is controlled by using the temperature controlling means at the printing time and the fixing device is controlled by using the input quantity controlling means at a stand-by time. When the control is performed by the input quantity controlling means, it is set in a balanced state by the temperature by which the heat generation of the fixing device and the heat radiation of it are balanced, and balancing temperature is set as the temperature by which a damage to a fixing sleeve and the other constituting member is suppressed to a minimum. The turn-on time of an electric power inverter is shortened, or the electric power input is intermittently performed or driving voltage is lowered as the controlling method of the electric power input.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a printer or a copying machine having a heating device using an electromagnetic induction heating system as a fixing device.

[0002]

2. Description of the Related Art In an image forming apparatus, a recording material (transfer material sheet, electrofax sheet, electrostatic recording paper, OHP paper, etc.) is used by an appropriate image forming process means such as an electrophotographic process, an electrostatic recording process, and a magnetic recording process. Sheet
A heat roller is used as a fixing device that heats and fixes an unfixed image (toner image) of the target image information formed on a printing paper or a format paper by a transfer method or a direct method as a permanently fixed image on a recording material surface. Type devices were widely used. Recently, a sleeve heating type device has been put into practical use from the viewpoint of quick start and energy saving. Also, an electromagnetic induction heating system has been proposed.

A) Heat roller type fixing device This is a fixing device which basically has a pressure roller pair of a fixing roller (heating roller) and a pressure roller, rotates the roller pair, and is a mutual pressure contact portion of the roller pair. An unfixed toner image to be image-fixed in the fixing nip portion is introduced, and a recording material on which the unfixed toner image is carried is introduced, nipped and conveyed, and the unfixed toner image is recorded by the heat of the fixing roller and the pressing force of the fixing nip portion. This is to fix the material by heat and pressure.

The fixing roller generally has a hollow metal roller made of aluminum as a base (metal core), and a halogen lamp as a heat source is inserted and disposed in the hollow space thereof. The power supply to the halogen lamp is controlled to control the temperature so that the predetermined fixing temperature is maintained.

In particular, as a fixing device of an image forming apparatus for forming a full-color image, which is required to have a capability of sufficiently heating and melting a maximum of four toner image layers to mix colors, a core metal of a fixing roller has a high heat capacity. And a rubber elastic layer for wrapping the toner image around the core metal and uniformly melting the toner image, and heating the toner image via the rubber elastic layer. There is also a configuration in which a heat source is provided in the pressure roller to heat and control the temperature of the pressure roller.

However, in the heat roller type fixing device, even when the power of the image forming apparatus is turned on and the halogen lamp, which is the heat source of the fixing device, is energized at the same time, the heat capacity of the fixing roller is large, and the fixing roller and the like are cooled. A considerable waiting time (wait time) is required from the cutting state to the rise to a predetermined fixable temperature, and the quick start property is lacking. Further, it is necessary to keep the fixing roller in a predetermined temperature control state by energizing the halogen lamp so that the image forming operation can be performed at any time even when the image forming apparatus is in a standby state (non-image output). There were problems such as a large amount.

Further, in a fixing device having a particularly large heat capacity, such as the fixing device of the above-described full-color image forming apparatus, a delay occurs between the temperature control and the temperature rise of the fixing roller surface. Problems such as uneven gloss and offset have occurred.

B) Fixing Device of Film Heating System A fixing device of the film heating system is disclosed in, for example, JP-A-63-3
Japanese Patent Application Laid-Open No. 13182, Japanese Patent Application Laid-Open No. 2-1577878, Japanese Patent Application Laid-Open No. 4-44075, Japanese Patent Application Laid-Open No. 4-204980, and the like.

That is, a nip portion is formed by sandwiching a heat-resistant film (fixing sleeve) between a ceramic heater as a heating element and a pressing roller as a pressing member. A recording material on which an unfixed toner image to be fixed is formed is carried between the pressure roller and the recording material. The recording material is sandwiched and conveyed together with the film. And fixing the unfixed toner image on the surface of the recording material with heat and pressure by the pressing force of the nip portion.

This fixing device of the film heating type can constitute an on-demand type device using a ceramic heater and a member having a low heat capacity as a film, and a ceramic heater as a heat source only when the image forming apparatus executes image formation. To a state in which heat is generated to a predetermined fixing temperature, the waiting time from the power-on of the image forming apparatus to the image forming executable state is short (quick start property), and the power consumption during standby is greatly reduced. There are advantages such as small (power saving).

However, a full-color image forming apparatus requiring a large amount of heat or a fixing device for a high-speed model has a calorific point.

C) Fixing Device of Electromagnetic Induction Heating System JP-A-51-109739 discloses an induction heating fixing device in which current is induced in a fixing roller by magnetic flux to generate heat by Joule heat. This makes it possible to directly generate heat in the fixing roller by utilizing the generation of an induced current, and achieves a more efficient fixing process than a heat roller type fixing device using a halogen lamp as a heat source.

However, since the energy of the alternating magnetic flux generated by the exciting coil as the magnetic field generating means is used to raise the temperature of the entire fixing roller, heat dissipation is large, and the fixing energy density with respect to the input energy is low, resulting in poor efficiency. there were.

Therefore, in order to obtain the energy acting on the fixing at a high density, the exciting coil is brought closer to the fixing roller as a heating element, or the alternating magnetic flux distribution of the exciting coil is concentrated near the fixing nip portion. An efficient fusing device has been devised.

FIG. 16 shows a schematic configuration of an example of the electromagnetic induction heating type fixing device in which the alternating magnetic flux distribution of the exciting coil is concentrated on the fixing nip to improve the efficiency.

Reference numeral 1601 denotes a cylindrical fixing sleeve having an electromagnetic induction heating layer (a conductor layer, a magnetic layer, and a resistor layer) and serving as an electromagnetic induction heating rotating body.

Reference numeral 1603 denotes a gutter-shaped sleeve guide member having a substantially semicircular cross section. The cylindrical fixing sleeve 1601 is loosely fitted outside the sleeve guide member 1603.

Numeral 1602 denotes a magnetic field generating means disposed inside the sleeve guide member 1603,
5 and an E-shaped magnetic core (core material) 1604.

An elastic pressure roller 1607 sandwiches the fixing sleeve 1601 and a sleeve guide member 1603.
Nip N having a predetermined width with a predetermined pressing force against the lower surface of
Are formed and mutually pressed.

The magnetic core 16 of the magnetic field generating means 1602
Numeral 04 is provided corresponding to the fixing nip portion N.

The pressing roller 1607 is driven to rotate in the counterclockwise direction indicated by the arrow by the driving means M. This pressure roller 16
07 by the frictional force between the pressure roller 1607 and the outer surface of the fixing sleeve 1601 by the rotation drive of the fixing sleeve 1601.
Is applied to the fixing sleeve 1601 so that the inner surface of the fixing sleeve 1601 is fixed to the sleeve guide member 160 at the fixing nip portion N.
The outer periphery of the sleeve guide member 1603 is rotated in a clockwise direction as indicated by an arrow at a peripheral speed substantially corresponding to the rotational peripheral speed of the pressure roller 1607 while sliding in close contact with the lower surface of the pressure roller 3 (pressure roller driving method). .

The sleeve guide member 1603 presses the fixing nip, supports the exciting coil 1605 and the magnetic core 1604 as the magnetic field generating means 1602, and fixes the fixing sleeve 1
It serves to support the 601 and to improve the transport stability of the film 1601 during rotation. This sleeve guide member 1603
Is an insulating member that does not hinder the passage of magnetic flux, and is made of a material that can withstand a high load.

The exciting coil 1605 generates an alternating magnetic flux by an alternating current supplied from an exciting circuit (not shown). The alternating magnetic flux is intensively distributed to the fixing nip N by the E-shaped magnetic core 1604 corresponding to the position of the fixing nip N, and the alternating magnetic flux is distributed to the electromagnetic induction heating layer of the fixing sleeve 1601 at the fixing nip N. Generates eddy currents. This eddy current generates Joule heat in the electromagnetic induction heating layer due to the specific resistance of the electromagnetic induction heating layer.

The electromagnetic induction heat of the fixing sleeve 1601 is concentrated in the fixing nip N where the alternating magnetic flux is intensively distributed, and the fixing nip N is heated with high efficiency.

The temperature of the fixing nip N is controlled by the thermistor 16.
06 by the temperature control system including the temperature detecting means 06, etc.
The temperature is controlled so that a predetermined temperature is maintained by controlling the current supply to 605.

As the pressure roller 1607 is driven to rotate, the cylindrical fixing sleeve 1601 rotates around the sleeve guide member 1603 and power is supplied from the excitation circuit to the excitation coil 1605 as described above. In a state where the fixing nip portion N rises to a predetermined temperature due to electromagnetic induction heating of the fixing sleeve 1601 and the temperature is adjusted, the recording on which the unfixed toner image t conveyed from the image forming unit (not shown) is formed. The material P is introduced between the fixing sleeve 1601 of the fixing nip N and the pressure roller 1607 with the image surface facing upward, that is, opposed to the fixing sleeve surface.
In the fixing nip portion N, the image surface is fixed to the fixing sleeve 1601.
The fixing nip portion N is conveyed together with the fixing sleeve 1601 in close contact with the outer surface of the fixing nip N. In the process of nipping and transporting the recording material P together with the fixing sleeve 1601 through the fixing nip N, the unfixed toner image t on the recording material P is heated and fixed by the electromagnetic induction heating of the fixing sleeve 1601. You. When the recording material P passes through the fixing nip portion N, it is separated from the outer surface of the rotary fixing sleeve 1601 and is discharged and conveyed.

The temperature control of the fixing device in the conventional example will be described below. FIG. 17 shows a control flowchart of a conventional example. The control based on this flowchart generally uses an arithmetic device such as a CPU or a DSP, but the control unit may be configured with only hardware.

The power of the image forming apparatus is turned on (step 17).
01) After the appropriate processing (checking of each part etc.) is completed,
The motor for driving the pressure roller is started, the pressure roller is rotated, and the fixing sleeve is driven. The fixing temperature control during standby is started to generate heat in the fixing sleeve (1702). The standby fixing temperature control means that the detected temperature of the fixing device detected by a temperature detecting element such as a thermistor or a thermopile is a control target temperature Ta.
(For example, 130 ° C.). At this time, the temperature detecting element may be detected by the temperature detecting element at any location where the heating state of the fixing device is known, but the fixing sleeve which is a heating element is most suitable.

Normally, when the fixing device is completely cooled, for example, after the power is turned on, the detected temperature is lower than the control target temperature Ta, so that the fixing sleeve generates heat at the maximum power.

When the fixing sleeve is heated by the fixing temperature control during standby (1703) and the detected temperature becomes equal to or higher than Ts ° C., the drive circuit performs power control to start temperature control to maintain the fixing device at Ts ° C. The forming apparatus enters a standby state (1705). When the standby state is entered, a print accepting state is established, and the fixing temperature control during standby is continued unless there is a print request (1706).

Here, the fixing device using induction heating can perform highly efficient heating, and the fixing member generates heat. Possible, that is, on-demand fixing is possible. However, with the increase in the amount of heat required at startup due to the increase in size of the device and the demand for the first print time becoming stricter, on-demand printing that satisfies users can be performed even with a fixing device using induction heating. It's gone. Therefore, it is necessary to perform standby heating in order to realize the first print time desired by the user.

When the image forming apparatus receives a print request from a host terminal such as a PC (1707), the fixing temperature control during standby is stopped, the fixing temperature control during printing is started, and the fixing sleeve is further heated (1708). . The fixing temperature control at the time of printing means that the detected temperature of the fixing device is a control target temperature Tb (for example, 1) which is sufficient to fix the toner image formed on the paper.
(90 ° C.) to control the temperature of the fixing device so as to be a constant value. Usually, since the detected temperature Ts of the fixing device at this time is lower than the control target temperature Tb, the fixing sleeve generates heat with the maximum power.

At the time of printing, the fixing sleeve generates heat by controlling the fixing temperature (1709). When the detected temperature becomes equal to or higher than Tp ° C., the drive circuit performs power control to start temperature control to keep the fixing device at Tp ° C. The forming device enters a fixable state (1710). When the image can be fixed, the image forming apparatus starts a printing operation, a toner image is formed on paper,
The paper is fixed on the paper by the fixing device (1711). This printing operation is continued until the print request is completed, during which time the fixing device adjusts the fixing temperature during printing (1712). When the print request is completed (1713), the control target temperature is changed from Tb ° C. to Ta ° C., and the fixing temperature control during printing is switched from the fixing temperature control during standby to the fixing temperature control during standby until the next print request is issued. Do.

The above is the description of the control flowchart in the conventional example.

FIG. 18 shows the temperature transition of the fixing device during control in the conventional example. As described in the control flowchart, heating is started when the power is turned on, and control is performed such that the temperature control temperature is kept constant at Ts ° C. during standby. When a print request is received, heating is started, and control is performed to keep the temperature regulation temperature Tp constant. When the printing is completed, the apparatus returns to the standby state, and performs control to keep the temperature control temperature at Ts ° C.

[0036]

However, the fixing device using the electromagnetic induction heating system shown in the above-mentioned conventional example has the following problems.

As described in the conventional example, in order to realize the start-up speed that can satisfy the user with the fixing device of the heat roller type, it is necessary to wait while maintaining a very high temperature (for example, about 160 ° C.). In this case, the heater must be degraded due to the high temperature during standby and the peripheral members must be degraded. In order to maintain the high temperature, a large amount of electric power (for example, about several hundred W) must be continuously supplied. There was a problem such as not having.

In the standby control in the fixing device using the electromagnetic induction heating system as shown in the conventional example, since the temperature is adjusted, the load on the control device such as the CPU is large, and the temperature control in two stages is performed. For this purpose, the temperature must be detected with high accuracy, and the driving motor such as the pressure roller with a large driving torque must be constantly driven, resulting in high power consumption. There was.

An object of the present invention is to realize a quick start-up of a fixing apparatus using an electromagnetic induction heating system even in a color image forming apparatus or a high-speed image forming apparatus. At the same time, the consumption during standby is shorter than when two types of temperature control (so-called print temperature control and standby temperature control) are performed in a fixing device using a halogen heater or the like or a conventional fixing device using an electromagnetic induction heating method. The purpose of the present invention is to suppress power consumption and to reduce damage to a fixing device and other components due to heat.

[0040]

According to a first aspect of the present invention, there is provided an image forming apparatus including a fixing device for heating a material to be heated which carries an image.
The fixing device includes: an exciting coil serving as a magnetic field generating unit; a power inverter for driving the exciting coil; a member that generates electromagnetic induction by the action of the magnetic field of the magnetic field generating unit; A pressure member for forming a nip portion of the member to be heated by pressing, and applying a magnetic field of the magnetic field generating means to the electromagnetic induction heating member to heat the material to be heated by the heat generated by the electromagnetic induction heating member; A fixing device, configured to control a temperature of the fixing device based on a detection result of the fixing device, the temperature of the fixing device being controlled to a first target temperature based on a detection result of the fixing device; First temperature control means, first power control means for controlling the output power of the power inverter to a first power amount or less,
Wherein the control is performed by using the first temperature control means during the fixing operation of the fixing device, and the control is performed by using the first power control means during standby of the fixing device. I do.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the temperature detected by the fixing device is the second temperature.
When the temperature is lower than the first temperature, the first startup control for controlling the output power of the power inverter to be equal to or more than the second power amount is performed until the first condition is satisfied.

According to a third aspect of the present invention, in the image forming apparatus according to the first aspect, the temperature detected by the fixing device is the second temperature.
When the temperature is lower than the second temperature, the second start-up control controlled by the first temperature control means is performed until the first condition is satisfied.

According to a fourth aspect of the present invention, in the image forming apparatus according to the second or third aspect, the first condition is that whether a detected temperature of the fixing device is equal to or higher than a third temperature. It is characterized by being.

According to a fifth aspect of the present invention, in the image forming apparatus according to the second or third aspect, the first condition is:
The time for performing the first or second startup control is the first time.
Or not longer than the time.

According to a sixth aspect of the present invention, in the image forming apparatus of the fifth aspect, the first time is determined by a temperature detected by the fixing device.

According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the first to sixth aspects, when the first power control means controls the power, the electromagnetic induction heating member is stopped, or It operates at low speed.

According to an eighth aspect of the present invention, in the image forming apparatus according to any one of the first to sixth aspects, the control of the output power is performed by adjusting the ON time of a switching element of a power inverter. And

According to a ninth aspect of the present invention, in the image forming apparatus according to any one of the first to sixth aspects, the output power is controlled by an intermittent output of a power inverter.

The tenth invention according to the present application is claimed in claims 1 to 6
In the image forming apparatus according to any one of the above, the temperature of the fixing device at the time of power control by the first power control means is a certain temperature due to a balance between heat generation by the electromagnetic induction heating member and heat radiation to the outside of the fixing device. It is characterized by being within the range.

The eleventh invention according to the present application is claim 2 to claim 6.
5. The image forming apparatus according to claim 1, wherein the second temperature is lower than the first temperature.

In the above configuration, there is provided an image forming apparatus in which the start-up of the apparatus is completed at a higher speed and energy is saved.

[0052]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG. 1 is a view for explaining an entire image forming apparatus according to an embodiment of the present invention.
In this embodiment, four colors, namely, yellow Y, magenta M,
This is a color image forming apparatus provided with cyan C and black K image forming means.

Reference numeral 201 denotes a photosensitive drum for forming an electrostatic latent image (a, b, c, and d indicate black K, cyan C, magenta M, and yellow Y, respectively), and 202 (a, b, c, and y).
d) is a laser scanner that performs exposure according to an image signal to form an electrostatic latent image on the photosensitive drum 201, and 203 is an endless transport belt that also serves as a transfer belt and sequentially transports paper to an image forming unit of each color. And 204, a fixing device for fixing the toner image formed on the sheet to the sheet.

Data to be printed is sent from a PC (not shown) to the printer, and when image formation in accordance with the printer engine system is completed and the printer is ready for printing, paper is supplied from a paper cassette (not shown) and a transport belt is provided. The sheet arrives at 203, and the sheet is sequentially conveyed to the image forming units of each color by the conveying belt 203. Image signals of the respective colors are sent to the respective laser scanners 202 in synchronism with the sheet conveyance by the conveyance belt 203, an electrostatic latent image is formed on the photosensitive drum 203, and the toner is developed by a developing unit (not shown). The image is transferred onto the paper at the transfer unit. In FIG. 1, images are sequentially formed in the order of yellow Y, magenta M, cyan C, and black K. Thereafter, the sheet is separated from the transport belt, the toner image is fixed on the sheet by heat in the fixing device 204, and is discharged to the outside.

Hereinafter, the fixing device 204 will be described in detail. In this example, the fixing device 204 is an electromagnetic induction heating type device. FIG. 2 is a cross-sectional side view of a main part of the fixing device 204 of the present embodiment, FIG. 3 is a front view of the main part, and FIG. 4 is a longitudinal front view of the main part.

The apparatus 204 of this embodiment uses a cylindrical electromagnetic induction heating belt similarly to the fixing apparatus of FIG.
It is a pressure roller drive system and electromagnetic induction heating system.
The same reference numerals are given to the same components and portions as those in the apparatus of FIG. 16, and the description will not be repeated.

The magnetic field generating means is magnetic cores 1604a and 16
04b and 1604c and an exciting coil 1605.

Magnetic cores 1604a, 1604b, 160
Reference numeral 4c denotes a member having high magnetic permeability, which is preferably made of a material used for a transformer core, such as ferrite or permalloy, and more preferably a ferrite having a small loss even at 100 kHz or more.

The exciting coil 1605 has a feeder 1605a
The excitation circuit 601 is connected to 1605b (FIG. 5). This excitation circuit 601 has a frequency of about 20 kHz to 500 kHz.
A high-frequency current of z is generated. The excitation circuit 601 will be described later in detail. The exciting coil 1605 is the exciting circuit 6
An alternating magnetic flux is generated by an alternating current (high-frequency current) supplied from 01.

Reference numerals 1603a and 1603b denote sleeve guide members each having a substantially semi-arc-shaped trough-shaped cross section. The opening side faces each other to form a substantially cylindrical body, and a fixing sleeve which is a cylindrical electromagnetically inductive heating belt on the outside. 1601 is loosely fitted.

The sleeve guide member 1603a includes magnetic cores 1604a, 1604b,
1604c and the excitation coil 1605 are held inside.

In the sleeve guide member 1603a, a good heat conducting member 304 is disposed inside the fixing sleeve 1601 on the side of the nip portion N facing the pressure roller 1607, as shown in FIGS. I have.

In this example, aluminum is used for the good heat conductive member 304. The good heat conducting member 304 has a heat conductivity k = 240 [w · m ⁻¹ · K ⁻¹ ] and a thickness of 1 [mm].

The good heat conducting member 304 includes an exciting coil 1605 serving as a magnetic field generating means and magnetic cores 1604a and 1604a.
It is arranged outside this magnetic field so as not to be affected by the magnetic field generated from the magnetic fields 04b and 1604c.

More specifically, the good heat conducting member 304 is disposed at a position where the magnetic core 1604c is separated from the exciting coil 1605, and is located outside the magnetic path formed by the exciting coil 1605 to form the good heat conducting member 304. Try not to affect.

Reference numeral 302 denotes a horizontally-long pressurizing rigid stay disposed in contact with the inner flat surface of the sleeve guide member 1603b.

Numeral 301 denotes magnetic cores 1604a and 1604b.
An insulating member for insulating the 1604c and the exciting coil 1605 from the rigid stay 302 for pressing.

The flange members 402a and 402b are externally fitted to the left and right ends of the assembly of the sleeve guide members 1603a and 1603b, and are rotatably mounted while fixing the left and right positions. When the fixing sleeve 1601 rotates, the ends of the fixing sleeve 1601 are rotated. The portion serves to regulate the sideward movement of the fixing sleeve along the length of the sleeve guide member.

A pressure roller 1607 as a pressure member is
It is composed of a core bar 1607a and a heat-resistant and elastic material layer 1607b such as silicone rubber, fluoro rubber or fluoro resin which is formed and coated concentrically around the core bar in the form of a roller. The portion is rotatably supported between chassis side plates (not shown) of the apparatus.

Pressing springs 403a and 403b are contracted between both ends of the pressing rigid stay 302 and spring receiving members 404a and 404b on the apparatus chassis side, respectively, so that a pressing force is applied to the pressing constituent stay 302. ing.
As a result, the lower surface of the sleeve guide member 1603a and the upper surface of the pressure roller 1607 are pressed against each other with the fixing sleeve 1601 interposed therebetween, thereby forming a fixing nip portion N having a predetermined width.

The pressure roller 1607 is driven to rotate in the counterclockwise direction indicated by the arrow by the driving means M. This pressure roller 16
07, the frictional force between the pressure roller 1607 and the outer surface of the fixing sleeve 1601 due to the rotational driving of the fixing sleeve 1601.
1, the fixing sleeve 1601 slides while the inner surface of the fixing sleeve 1601 is in close contact with the lower surface of the good heat conducting member 304 at the fixing nip N, and the pressing roller 1
The outer peripheral rotation of the sleeve guide members 1603a and 1603b is brought into a rotating state at a peripheral speed substantially corresponding to the rotational peripheral speed of 607.

In this case, in order to reduce the mutual sliding friction between the lower surface of the good heat conducting member 304 in the fixing nip N and the inner surface of the fixing sleeve 1601, the lower surface of the good heat conducting member 304 in the fixing nip N is fixed. A lubricant such as heat-resistant grease may be interposed between the inner surface of the sleeve 1601 and the lower surface of the good heat conductive member 304 may be covered with a lubricating member. This is because when the surface sliding property is not good in material such as when aluminum is used as the good heat conducting member 304 or when the finishing process is simplified, the sliding fixing sleeve 1601 is damaged and the fixing sleeve 1601 is damaged.
01 is prevented from deteriorating.

The good heat conducting member 304 has an effect of making the temperature distribution in the longitudinal direction uniform. For example, when small size paper is passed, the amount of heat of the non-paper passing portion of the fixing sleeve 1601 is reduced.
The heat is transferred to the good heat conducting member 304, and the amount of heat in the non-sheet passing portion is transferred to the small size sheet passing portion by heat conduction in the longitudinal direction of the good heat conducting member 304. As a result, an effect of reducing power consumption when passing small-sized paper is also obtained.

As shown in FIG. 5, the peripheral surface of the sleeve guide member 1603a is provided with convex ribs 1603c at predetermined intervals along the length thereof, so that the peripheral surface of the sleeve guide member 1603a is fixed to the fixing sleeve. 1601 by reducing the contact sliding resistance with the inner surface of the fixing sleeve 1601
Rotation load is reduced. Such a convex rib portion can be similarly formed and provided on the sleeve guide member 1603b.

FIG. 6 schematically shows how alternating magnetic flux is generated. C represents a part of the generated alternating magnetic flux.
The alternating magnetic flux C guided to the magnetic cores 1604a, 1604b, and 1604c is
4b, and the magnetic core 1604a and the magnetic core 16
04c, an eddy current is generated in the electromagnetic induction heating layer 701 of the fixing sleeve 1601. This eddy current is generated by the electromagnetic induction heating layer 7 by the specific resistance of the electromagnetic induction heating layer 701.
01 generates Joule heat (eddy current abduction). The heat value Q here is determined by the density of the magnetic flux passing through the electromagnetic induction heating layer 701, and shows a distribution as shown in the graph of FIG.

The vertical axis of the graph of FIG.
The fixing sleeve 160 represented by an angle θ with the center of a being 0
The horizontal axis indicates the heat generation amount Q in the electromagnetic induction heating layer 701 of the fixing sleeve 1601.
Here, the heating area H is defined as an area where the heating value is Q / e or more, where Q is the maximum heating value. This is an area where a heat value required for fixing can be obtained.

The temperature of the fixing nip N is controlled such that a predetermined temperature is maintained by controlling the current supply to the exciting coil 1605 by a temperature control system including a temperature detecting means (not shown). Reference numeral 1606 (FIG. 2) denotes a temperature sensor such as a thermistor for detecting the temperature of the fixing sleeve 1601. The temperature sensor 1606 is located downstream of the fixing nip N in the paper transport direction as shown in FIG. Is provided so as to be in contact with. In this embodiment, the temperature of the fixing nip N is controlled based on the temperature information of the fixing sleeve 1601 measured by the temperature sensor 1606.

Thus, the fixing sleeve 1601 rotates,
The power is supplied from the excitation circuit 601 to the excitation coil 1605, and the electromagnetic induction heating of the fixing sleeve 1601 is performed as described above, so that the fixing nip N rises to a predetermined temperature and is conveyed from the image forming unit in a state where the temperature is regulated. The recording material P on which the unfixed toner image t is formed is introduced between the fixing sleeve 1601 and the pressure roller 1607 in the fixing nip portion N with the image surface facing upward, that is, opposed to the fixing sleeve surface. In the portion N, the image surface is brought into close contact with the outer surface of the fixing sleeve 1601, and the fixing nip N is conveyed together with the fixing sleeve 1601.

The fixing nip N is fixed to the fixing sleeve 160.
In the process in which the recording material P is pinched and conveyed together with the recording material 1, the unfixed toner image t on the recording material P is heated and fixed by the electromagnetic induction heat of the fixing sleeve 1601. When the recording material P passes through the fixing nip portion N, it is separated from the outer surface of the rotary fixing sleeve 1601 and is discharged and conveyed. The heat-fixed toner image on the recording material passes through the fixing nip,
Upon cooling, it becomes a permanent fixed image.

Here, the temperature sensor (thermistor) 160
The position 6 cannot be the same as the heating section. This is for the following reason. Correct output cannot be obtained due to the influence of the induction magnetic field. Since there are many components such as coils, cores, and holders in the heating unit, there is no space for disposing the thermistor.

In this embodiment, as shown in FIG. 2, a thermo-switch, which is a temperature detecting element, is provided at a position facing the heat generating area H (FIG. 6) of the fixing sleeve 1601 to cut off power supply to the exciting coil 1605 during runaway. 303 is provided.

FIG. 7 is a circuit diagram of the safety circuit used in this example. Thermo switch 303 which is a temperature detecting element is +2
The 4 VDC power supply and the relay switch 802 are connected in series. When the thermo switch 303 is turned off, the power supply to the relay switch 802 is cut off and the relay switch 802 is turned off.
Operates, and the power supply to the excitation coil 1605 is cut off when the power supply to the excitation circuit 601 is cut off. The thermo switch 303 sets the OFF operation temperature to 22.
It was set to 0 ° C.

Further, the thermoswitch 303 is opposed to the heat generating area H of the fixing sleeve 1601,
In a non-contact manner. The distance between the thermoswitch 303 and the fixing sleeve 1601 was approximately 2 mm. As a result, the thermoswitch 30 is attached to the fixing sleeve 1601.
No damage is caused by the contact of No. 3 and deterioration of the fixed image due to durability can be prevented.

According to this embodiment, when the fixing device goes out of control due to a device failure, unlike the device configuration in which heat is generated in the fixing nip N as shown in FIG. Even when the apparatus is stopped and power is continuously supplied to the exciting coil 1605 and the fixing sleeve 1601 continues to generate heat, the paper is not directly heated because no heat is generated in the fixing nip portion N where the paper is sandwiched. Further, since the thermo switch 303 is provided in the heat generation area H where the heat generation is large, the relay switch 8 is turned off when the thermo switch 303 detects 220 ° C. and the thermo switch is turned off.
02 shuts off the power supply to the exciting coil 1605.

According to this example, the ignition temperature of the paper is about 400 ° C.
Since it is near, the heat generation of the fixing sleeve can be stopped without firing the paper.

Thermo switch 303 as temperature detecting element
Alternatively, a thermal fuse can be used.

In this example, since a toner containing a low softening substance was used in the toner t, an oil applying mechanism for preventing offset was not provided in the fixing device, but a toner not containing a low softening substance was used. In this case, an oil application mechanism may be provided. Also, when a toner containing a low softening substance is used, oil application or cooling separation may be performed. The above is the description of the fixing device 204.

Hereinafter, the excitation circuit 601 will be described. FIG.
5 shows a circuit in which an exciting coil 1605 and an exciting circuit 601 are connected to generate an alternating magnetic field by an exciting current. This excitation circuit generates a high-frequency current of about 20 kHz to 500 kHz.

FIG. 8 shows a circuit configuration of the excitation circuit 601. In FIG. 8, reference numeral 901 denotes a switching element;
Devices often used are devices such as MOSFETs and IGBTs. 902 is a reverse conducting diode. 160
5 is an exciting coil, 904 is a resonance capacitor. In such a circuit, single voltage resonance is performed by turning on and off the switch element 901.

FIG. 9 is a block diagram of the overall configuration of the induction heating control section including the output converter of FIG.

1001 is a power line input terminal, 1002
Is a circuit breaker, 1003 is a relay, 1004
Is a rectifier circuit composed of a bridge rectifier circuit for performing double-wave rectification from an AC input and a capacitor for performing a high-frequency filter;
005 is a gate control transformer, 1006 (901, 90
2) is a switching element, 904 is a resonance capacitor, 1
Reference numeral 008 denotes a current transformer that detects the switching current switched in step 1006 and is connected to the excitation coil of the fixing device. Reference numeral 1010 denotes a fixing unit unit which has the above-described excitation coil 160 as an electric component.
5 and a temperature detection thermistor 1606 and a thermoswitch 303 for detecting excessive temperature rise.

Reference numeral 1011 denotes a heating ON / OFF signal input to the fixing device, which is sent from the printer sequence controller. Reference numeral 1012 denotes a feedback control for controlling a control amount while comparing with a target temperature based on the detected value of the thermistor temperature of the fixing device. The circuit 1013 is a driver circuit that receives a feedback control signal and performs control appropriate to the control mode of the converter.

When an AC power supply is input from 1001 and AC power is applied to the rectifier circuit 1004 via an overcurrent breaker and a relay, a pulsating DC voltage is generated by a double-wave rectifier diode.

By driving the gate transformer 1005 with the subsequent switching element so that the switching element 1006 performs switching, the excitation coil 16
An AC pulse voltage is applied to a resonance circuit formed by the capacitor 05 and the resonance capacitor 1006. As a result, when the switching element 1006 is turned on, a pulsating DC voltage is applied to the excitation coil, and a current determined by the inductance and resistance of the excitation coil starts flowing. When the switching element is turned off according to the gate signal, the exciting coil tries to keep the current flowing, so that a high voltage called a flyback voltage, which is determined by the resonance capacitor and the exciting coil at both ends, is generated. This voltage oscillates around the power supply voltage, and converges to the power supply voltage if the off state is maintained. When the ringing of the flyback voltage is large and the voltage of the coil side terminal of the switching element is negative, the reverse conducting diode 90 is used.
2 turns on and current flows into the coil. During this period, the contact between the coil and the switching element is clamped at 0V. It is generally known that if a switching element is turned on during such a period, it can be turned on without carrying a voltage, and is called ZVS. In such a case, the loss due to the switching of the switching element is minimized, and efficient, low-noise switching is possible.

The temperature of the fixing device is detected by thermistor 1.
606, the resistance change of the thermistor 1606 is converted into a voltage, and compared with a predetermined reference voltage.
Detected as the difference from the target temperature. The ON time width is determined based on the detection result, and PWM control is performed based on the ON time width. The PWM control part comprises two pairs of constant current source circuits, a capacitor and a comparator, an on-time control part and an off-time control part. The off-time control part is stopped during the on-time, and the on-time control part is made during the off-time. Is stopped, and the ON time and the OFF time whose time widths are sequentially controlled by the steering flip-flop are repeatedly output. The off-time comparator is configured to be adjustable but has no feedback loop, so that control is performed for a fixed time, and temperature control is realized by feeding back temperature information to the on-time comparator.

The time during which the current flows through the exciting coil, that is, the maximum value of the time during which the switching element is on, is determined by the AC line voltage value and the power that can be supplied, and the control signal from the control circuit is set within a range not exceeding the time. Has become. Further, a configuration for defining the minimum time may be provided.

If the temperature of the fixing device is low when the power is turned on, such as when starting up in the morning, power is supplied in an on-time width close to the maximum time width. When the power that can be input is 1100 W as an example, power is supplied at 1100 W at the maximum on-time width from power-on until temperature control is performed, and the on-time width is determined by a signal from the thermistor 1606 as a temperature detecting element. And power is controlled.

A breaker 1002 for receiving AC power from a power input terminal 1001 to protect an overcurrent and a relay contact 10
The rectifier circuit 1004 enters the rectifier circuit 1004 via the control circuit 03. Here, the excitation winding of the relay detects the sleeve temperature of the fixing device, and is configured as an example via a thermoswitch contact that shuts off when the sleeve temperature exceeds a specified temperature and abnormally rises,
Even if a trouble occurs and the temperature of the fixing device rises abnormally, the relay 1003 is shut off and the power supply of the excitation circuit 601 is turned off to ensure the safety of the fixing device from thermal runaway. The above is the description of the excitation circuit 601.

In this case, the excitation circuit 60
Although the description has been made using a single voltage resonance type inverter as an example, any inverter that can generate an alternating current such as a current resonance type or a partial resonance type other than the voltage resonance type may be used.

Hereinafter, control of the fixing device using induction heating according to the first embodiment of the present invention will be described.

FIG. 10 shows a control flowchart of the first embodiment. The control based on this flowchart is executed by the CPU or D
Although it is common to use an arithmetic device such as an SP, the control unit may be configured only with hardware.

The power of the image forming apparatus is turned on (step 10).
1) After the appropriate processing (checking of each part) is completed, the motor for driving the pressure roller is started to rotate the pressure roller (102), and the fixing sleeve is driven. Next, power supply to the drive coil by the drive circuit is started to cause the fixing sleeve to generate heat (103). This power supply is performed until the detected temperature of the fixing device exceeds Ts ° C.

When the detected temperature becomes equal to or higher than Ts ° C. (104), the print request can be accepted (105), and at the same time, the input is switched to a fixed amount of low power (106). This small amount of small power input means that a constant power input of about several tens of watts is performed from the excitation circuit to the drive coil. As a method of reducing the power input, the ON time of the switching element of the excitation circuit is shortened. There is a method of reducing the excitation voltage pulse width to the excitation coil, and a method of inputting a small amount of power approximately by intermittently operating the drive circuit. Any method may be used.

The fixing device has a certain temperature range due to the relationship between the heat generated by the small power input and the heat radiation to the outside and heat conduction. The amount of heat dissipated varies depending on the outside air temperature, the amount of air in the vicinity of the device, and the like. If the temperature range at this time is set high, the time required for heating to a temperature at which fixation can be performed thereafter is short, that is, the first print time is shortened.

However, if the temperature range is set to a high value,
A large amount of input power is required, and power consumption during standby increases. In addition, by maintaining a high temperature,
Thermal stress occurs in members constituting the fixing device such as a sleeve and a pressure roller and members around the fixing device, which causes problems such as deformation and shortened life. After taking these conditions into account, the temperature range is set to an appropriate value. According to experiments conducted by us, the temperature of the fixing device at the time of printing of the fixing device of A3 paper size is about 180 to 200 ° C., and when the first print time is 20 s or less, the temperature range is 100 ° C. to 150 ° C. The temperature is preferably set to about 130 ° C. in this case,
The small power input may be about 70 W.

After switching to the low power input, the motor for driving the pressure roller is stopped, and the pressure roller and the fixing sleeve are stopped (107).

When the temperature is adjusted as in the prior art, in a system in which the temperature detection position and the heating position are different as in the present embodiment, the fixing sleeve, which is a heating material, must be constantly rotating. However, as described above, when the constant low power is input, the temperature of the apparatus is determined by the balance between heat generation and heat radiation, so that there is no problem in stopping the fixing sleeve. In addition, by not rotating the fixing sleeve, unnecessary heat radiation generated in portions other than the heating section when the fixing sleeve is rotating can be suppressed, thereby saving energy. Furthermore, by rotating the pressure roller as in this embodiment,
In a drive system in which the film is driven by the pressure roller to rotate, the drive torque is very large. By stopping the drive torque, the power consumption in the standby mode is reduced by about 10 W compared with the temperature control in the standby mode while the drive is being performed. I can do things.

When the image forming apparatus receives a print request from a host terminal such as a PC or the like (109), the driving of the pressure roller drive motor is started (110). The input is stopped, the fixing temperature control during printing is started, and the temperature of the fixing sleeve is further increased (111).

Heating of the fixing sleeve is performed by the fixing temperature control during printing (112), and when the detected temperature becomes Tp ° C. (11)
3), the temperature control for controlling the power by the drive circuit to keep the fixing device at Tp ° C. starts, and the image forming apparatus is in a fixable state. When the image can be fixed, the image forming apparatus starts a printing operation, a toner image is formed on the sheet, and is fixed on the sheet by the fixing device (114). This printing operation is continued until the print request is completed, during which time the fixing device performs fixing temperature control during printing (115). When the print request is completed, the fixing temperature control at the time of printing is stopped and switched to the constant low power input (116), and the constant low power input is performed until the next print request occurs.

The above is the description of the control flowchart according to the first embodiment.

FIG. 11 shows the temperature transition of the fixing device during control in the first embodiment. As described in the control flowchart, when the temperature exceeds the fixing device temperature Ts ° C., a constant small power is input, and the temperature at this time converges to an appropriate temperature. When a print request is received, heating is started, and control is performed to keep the temperature regulation temperature Tp constant. When printing is completed, a constant low power is input again, and the temperature converges to an appropriate temperature over time.

In this embodiment, control switching and the like are determined at the timing of a print request. However, the present invention is not necessarily limited to this timing, and it is not necessarily limited to this timing. An appropriate timing in image formation may be used, such as a timing at which the toner image formation on the paper is completed and reaches the fixing device.

In this embodiment, only a basic flowchart in the fixing control according to the present application is shown, and the control is not necessarily limited to this flowchart.
For example, in actual fixing control, there are various modes such as a sleep mode in which no power is supplied at all and a 1 / 2-speed fixing mode for improving the fixing property of a toner image. When the mode is shifted to, control unique to these modes may occur.

In this embodiment, as a power detection method for performing power control, current detection is performed by a current transformer, and power is calculated using this output. However, the present invention is not necessarily limited to this method. The voltage may be calculated using other methods such as detecting the voltage and calculating the power using the value.

In this embodiment, since the description has been given of the mode in which the sleeve rotates following the pressure roller, the expression of starting or stopping the rotation of the pressure roller drive motor is used as a method of controlling the rotation of the fixing sleeve. It is explained using. However, what is meant by this embodiment is whether or not the heating element is rotating. Therefore, any method of rotating the heating element may be used. There is no problem if a method of supplying power to the motor with a motor is used.

(Second Embodiment) A second embodiment of the present invention will be described. The configuration of the image forming apparatus, the configuration of the fixing device, and the like in this embodiment are the same as those in the first embodiment, and thus description thereof is omitted.

FIG. 12 shows a control flowchart of the second embodiment. The power of the image forming apparatus is turned on (step 120).
1) After completion of appropriate processing (checking of each part, etc.), a fixed small power is supplied to the induction heating fixing device to cause the fixing sleeve to generate heat (1202). This constant low power input means that a constant power input of about several tens of watts from the excitation circuit to the drive coil is performed in the same manner as the constant low power input in the first embodiment. The fixing sleeve generates heat by the constant small power input, and the temperature of the fixing device gradually increases. As described in the first embodiment, the fixing device is in an equilibrium state at a temperature where the heat generated by the small power input and the heat radiation to the outside are balanced. At the same time as the constant low power input is started, the print is ready to be received, and the constant low power input is continued as long as there is no print request. When the image forming apparatus receives a print request from a host terminal such as a PC (1203), even if the temperature does not reach a temperature range where heat generation and heat dissipation are balanced, rotation of the motor for driving the pressure roller is started (1204). The power input is stopped, the fixing temperature control during printing is started (1205), and the fixing sleeve is further heated.

Heating of the fixing sleeve is performed by the fixing temperature control at the time of printing (1206).
207), the drive circuit performs power control, and sets the fixing device to Tp.
The temperature adjustment to maintain the temperature in ° C. starts, and the image forming apparatus is in a fixable state. When the image can be fixed, the image forming apparatus starts a printing operation, a toner image is formed on the sheet, and is fixed on the sheet by the fixing device (1208). This printing operation is continued until the print request is completed, during which time the fixing device adjusts the fixing temperature during printing (120).
9). When the print request is completed (1210), the fixing temperature adjustment at the time of printing is stopped, and the input is switched to a constant low power input (121).
1) The rotation of the pressure roller driving motor is stopped (121).
2) Input a constant low power until the next print request is issued. Immediately after switching to this constant low power, there is more heat radiation than heat generation, so the temperature of the fixing device decreases.However, as time elapses, heat generation and heat radiation approach the same state. At the balanced temperature, the fixing device is in an equilibrium state.

The above is the description of the control flowchart according to the second embodiment.

FIG. 13 shows the temperature transition of the fixing device at the time of control in the second embodiment. As described in the control flowchart, when a constant low power is input and a print request is received, heating is started and control is performed so as to keep the regulated temperature Tp constant. When printing is completed, a constant low power is input again, and the temperature converges to an appropriate temperature over time. Although not shown in the figure, even when the print request does not come for a long time after the first constant low power input is performed, the temperature converges to an appropriate temperature as time elapses, such as after printing is completed.

(Third Embodiment) A third embodiment of the present invention will be described. The configuration of the image forming apparatus, the configuration of the fixing device, and the like in the present embodiment are the same as those in the first and second embodiments, and thus description thereof is omitted.

FIG. 14 is a control flowchart of the third embodiment. The power of the image forming apparatus is turned on (step 140).
1) After the appropriate processing (checking of each part) is completed, the motor for driving the pressure roller is started to rotate the pressure roller (1402), and the fixing sleeve is driven. Next, fixing temperature control during printing is started, and the fixing sleeve is heated (140).
3). The fixing sleeve is heated by the fixing temperature control during printing (1404), and the fixing temperature control during printing is performed until the elapsed time from the start of power supply exceeds a time t1 set as a time sufficient for heating the apparatus. Various methods such as a method of configuring a counter by hardware, a method of using a software timer, and the like can be used for calculating the elapsed time after the start of power supply. In this example, the time t1 is used as the preset value. However, the time t1 is based on the temperature detected by the temperature detecting element or the barometer such as the temperature outside the apparatus.
The setting may be made for each device or environment under each condition.

When the elapsed time from the start of power supply exceeds the set time t1 (1405), a print request can be accepted (1406), and at the same time, the input is switched to a small amount of low power input (1407). After switching to the low power input, the motor for driving the pressure roller is stopped, and the pressure roller and the fixing sleeve are stopped (1408).

When the image forming apparatus receives a print request from a host terminal such as a PC (1410), the driving of the pressure roller drive motor is started (1411), and the constant low power is input. Is stopped, the fixing temperature control during printing is started, and the fixing sleeve is further heated (1412).

The heat of the fixing sleeve is generated by the fixing temperature control at the time of printing (1413), and when the detected temperature becomes Tp ° C. (1
414), the drive circuit performs power control and sets the fixing device to Tp ° C.
, And the image forming apparatus enters a fixable state. When the image can be fixed, the image forming apparatus starts a printing operation, a toner image is formed on paper,
The sheet is fixed on the sheet by the fixing device (1415). This printing operation is continued until the print request is completed, during which time the fixing device adjusts the fixing temperature during printing (1416). When the print request is completed, the fixing temperature control at the time of printing is stopped and switched to the constant low power input (1417), and the constant low power input is performed until the next print request occurs.

The above is the description of the control flowchart according to the third embodiment.

FIG. 15 shows the temperature transition of the fixing device during control in the third embodiment. As described in the control flowchart, the fixing temperature during printing is adjusted until the set time t1 elapses after the power is turned on. After the elapse of the time t1, a constant small power input is made, and the temperature at this time converges to an appropriate temperature. When a print request is accepted, heating starts,
Control is performed to keep the temperature regulation temperature Tp constant. When printing is completed, a constant low power is input again, and the temperature converges to an appropriate temperature over time.

In this embodiment, the control at the time of the first start-up is performed by using the temperature control at the time of printing. However, other methods such as applying a certain amount of large power may be used.

In the present embodiment, the method of determining whether to start accepting a print request by using the time elapsed after the start of power-on has been described. However, for this determination, other conditions may be used. For example, various determination methods such as a method of using a time elapsed after the temperature reaches the temperature Tp ° C. at which the fixing temperature adjustment is performed at the time of printing can be considered.

The reason for adjusting the fixing temperature in FIG. 15 is as follows. In other words, by controlling the temperature at the fixing temperature and increasing the temperature in the apparatus, it is possible to prevent the start-up time from being delayed due to heat radiation from the heat generating portion to the surroundings when reheating from the standby state. .

By performing temperature control not at the temperature at the time of standby temperature control but at the fixing temperature, it is not necessary to set a plurality of target temperatures, so that the burden on hardware and software is reduced.

<Other Embodiments> 1) The fixing sleeve 1601 having electromagnetic induction heat generation may be of a form in which an elastic layer is omitted in the case of heat fixing such as a monochrome or one-pass multi-color image. . The electromagnetic induction heating layer 1701 may be formed by mixing a metal filler in a resin. It can also be a single-layer member of the electromagnetic induction heating layer.

2) The pressing member 1607 is not limited to a roller body, but may be another type of member such as a rotating belt type.

In order to supply thermal energy to the recording material also from the pressing member 1607 side, a heating means such as electromagnetic induction heating is also provided on the pressing member 1607 side to heat and control the temperature to a predetermined temperature. It can also be configured.

The rotation of the fixing sleeve 1601 is not limited to the pressure roller driving method of the embodiment.

3) The heating device of the present invention is not limited to the image heating and fixing device of the embodiment, but may be an image heating device for heating a recording material carrying an image to improve the surface properties such as gloss, It can be widely used as a means or a device for heating a material to be heated, such as a heating device, a device for heating and drying a material to be heated, and a laminating device.

[0137]

As described above, according to the present invention,
In the case of a fixing device using a halogen heater or the like, since the heat capacity is large and the heat conversion efficiency is low, the first print time does not burden the user (for example, 20 s).
In order to achieve this, the temperature control temperature during standby must be increased, so that power consumption during standby requires several hundred watts, whereas in the case of a fixing device using an induction heating method, the heat capacity is small. Since the heat conversion efficiency is high, when realizing the same first print time as the halogen method, the standby temperature can be made lower than the temperature control temperature of the halogen method, and the power consumption during standby is about several tens of watts. Therefore, it is very excellent from the viewpoint of energy saving.

By inputting a constant power during standby as in the present invention, even when the heating position and the temperature detection position are different, the temperature control during standby is not necessary, so that the pressure roller drive motor is stopped. It is possible to save energy for driving the motor. Further, since it is not necessary to constantly operate the motor, it is possible to extend the life of the motor and gears.

In addition, the power supplied to the fixing device does not change minutely due to the temperature control, and the power consumption during standby is stabilized.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an entire image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional side view of a main part of the fixing device according to the embodiment of the present invention.

FIG. 3 is a schematic front view of a main part of the fixing device according to the embodiment of the present invention.

FIG. 4 is a schematic cross-sectional front view of a main part of the fixing device according to the embodiment of the present invention.

FIG. 5 is a diagram showing a relationship between a magnetic field generation unit and an excitation circuit of the fixing device according to the embodiment of the present invention.

FIG. 6 is a diagram illustrating a relationship between a magnetic field generating unit and a heat generation amount Q of the fixing device according to the embodiment of the present invention.

FIG. 7 is a diagram showing a safety circuit of the fixing device according to the embodiment of the present invention.

FIG. 8 is a circuit diagram of a voltage resonance switching unit of the drive circuit according to the embodiment of the present invention.

FIG. 9 is a schematic configuration diagram of a drive circuit used in an embodiment of the present invention.

FIG. 10 is a diagram illustrating a control flowchart of the fixing device according to the first embodiment of the present invention.

FIG. 11 is a temperature transition diagram of the fixing device in the control according to the first embodiment of the present invention.

FIG. 12 is a view for explaining a control flowchart of a fixing device according to a second embodiment of the present invention.

FIG. 13 is a temperature transition diagram of the fixing device in the control according to the second embodiment of the present invention.

FIG. 14 is a view for explaining a control flowchart of a fixing device according to a third embodiment of the present invention.

FIG. 15 is a temperature transition diagram of the fixing device in the control according to the third embodiment of the present invention.

FIG. 16 is a schematic cross-sectional front view of a main part of a fixing device according to a conventional example.

FIG. 17 is a diagram illustrating a control flowchart of a fixing device according to a conventional example.

FIG. 18 is a temperature transition diagram of a fixing device under control of a conventional example.

[Explanation of symbols]

201 ‥ ··· photosensitive drum, 202 ‥‥ laser scanner, 203 · ‥ · conveyor belt, 204 · ‥ · fixing device,
601 high frequency power supply, 801 temperature detecting element for safety, 1601... Fixing sleeve, 1603 belt guide, 1604... Magnetic core, 1605 magnetic coil, 1606 temperature detecting element (thermistor) , 16
07 ‥ ··· Pressure roller as pressure member

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

Claims (11)

[Claims] 1. An image forming apparatus comprising a fixing device for heating a material to be heated carrying an image, the fixing device comprising: an exciting coil serving as a magnetic field generating means; and a power inverter for driving the exciting coil. A member that generates electromagnetic induction by the action of the magnetic field of the magnetic field generating means, and a pressing member that forms a nip portion of the material to be heated by mutual pressure contact with the electromagnetic induction heating member; A fixing device for applying a magnetic field of the magnetic field generating means to the material to be heated by the heat generated by the electromagnetic induction heating member; a temperature detecting means for detecting a temperature of the fixing device; and a detection result of the temperature detecting means. A first temperature control unit that controls the magnetic field generation unit so that the temperature of the fixing device becomes a first target temperature based on the first and second control units; and an output power of the power inverter that is controlled to be equal to or less than a first power amount. One And a power control unit. When the fixing device performs a fixing operation, control is performed using the first temperature control unit. When the fixing device is on standby, control is performed using the first power control unit. An image forming apparatus characterized in that: 2. A first start-up for controlling an output power of the power inverter to a second power amount or more until a first condition is satisfied when a temperature detected by the fixing device is lower than a second temperature. The image forming apparatus according to claim 1, wherein the control is performed. 3. When the detected temperature of the fixing device is lower than a second temperature, a second startup control controlled by the first temperature control means is performed until a first condition is satisfied. The image forming apparatus according to claim 1. 4. The image forming apparatus according to claim 2, wherein the first condition is whether a temperature detected by the fixing device is equal to or higher than a third temperature. 5. The method according to claim 2, wherein the first condition is whether the time for performing the first or second start-up control is longer than the first time. The image forming apparatus as described in the above. 6. The image forming apparatus according to claim 5, wherein the first time is determined by a temperature detected by the fixing device. 7. The image according to claim 1, wherein said electromagnetic induction heating member is stopped or operates at a low speed during power control by said first power control means. Forming equipment. 8. The image forming apparatus according to claim 1, wherein the control of the output power is performed by adjusting an ON time of a switching element of a power inverter. 9. The image forming apparatus according to claim 1, wherein the control of the output power is performed by an intermittent output of a power inverter. 10. The temperature of the fixing device during power control by the first power control means falls within a certain temperature range due to the balance between heat generation by the electromagnetic induction heating member and heat radiation outside the fixing device. The image forming apparatus according to any one of claims 1 to 6, wherein: 11. An image forming apparatus according to claim 2, wherein said second temperature is lower than said first temperature.