JP2002043048A - Heating device and image-forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate reduction in a service life of a sleeve due to concentra tion of heat generation, at a part of the sleeve to generate deterioration at the part by thermal fatigue, and eliminate fixing irregularity due to deterioration of the part of the sleeve. SOLUTION: Heating temperature control is conducted by use of a first control means in heating action time, when a subject to be heated passes a nip part, and stand-by temperature control is conducted by use of a second control means in stand-by time, when the object material to be heated does not pass the nip part in this heating device. It is provided with a heat generating position changing means for changing heating positions in an electromagnetic induction heat generating member by each specified condition under stand-by temperature control.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating device using an electromagnetic induction heating system for heating and fixing an unfixed toner image on the surface of a recording material as a material to be heated, a printer using the heating device, and a copying machine. The present invention relates to an image forming apparatus such as a printer.

[0002]

2. Description of the Related Art In an image forming apparatus, a recording material (transfer material sheet, electrofax sheet, electrostatic recording paper, OHP sheet) is used in an appropriate image forming process means such as an electrophotographic process, an electrostatic recording process, and a magnetic recording process. A fixing device that heats and fixes an unfixed image (toner image) of the target image information formed and supported on a printing paper or a format paper by a transfer method or a direct method as a permanent fixed image on a recording material surface is used. Roller-type fixing devices have been widely used. Recently, a sleeve heating type fixing device has been put into practical use from the viewpoint of quick start and energy saving. Further, a fixing device of an electromagnetic induction heating type has been proposed. a) Heat roller type fixing device The heat roller type fixing device basically has a pressing roller pair of a fixing roller (heating roller) and a pressing roller, and the pressing roller pair is rotated to allow the pressing roller pair to rotate. A recording material carrying an unfixed toner image to be image-fixed at the nip portion, which is a press contact portion, 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 nip portion. The surface is fixed by heat and pressure.

The fixing roller generally has a hollow metal roller made of aluminum as a base (core metal), and a halogen lamp as a heat source is inserted 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 be capable 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 if the power of the image forming apparatus is turned on and the energization of the halogen lamp which is the heat source of the fixing device is started 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. Therefore, it is necessary to supply current to the halogen lamp to maintain the fixing roller in a predetermined temperature control state 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 large consumption.

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) Film-heating type fixing device The film-heating type fixing device is a heat-resistant film (fixing sleeve, hereinafter abbreviated as sleeve) between a ceramic heater as a heating element and a pressing roller as a pressing member. To form a nip portion, and a recording material carrying an unfixed toner image to be fixed is introduced between the film and the pressure roller in the nip portion, and is sandwiched together with the film. By conveying, the heat of the ceramic heater is applied to the recording material via the film in the nip portion,
Further, the unfixed toner image is heat-pressure fixed on the recording material surface 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 performs 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 The fixing device of the electromagnetic induction heating system is a fixing device that induces a current in a sleeve by magnetic flux and generates heat by Joule heat. This makes it possible to directly generate heat in the sleeve by utilizing the generation of an induced current, thereby achieving a more efficient fixing process than a heat roller type fixing device using a halogen lamp as a heat source.

FIGS. 9, 10 and 11 show a schematic configuration of an example of a fixing device of an electromagnetic induction heating system. FIG. 9 is a schematic cross-sectional side view of a main part of the fixing device of this embodiment. FIG. 11 is a front model view of a main part, and FIG. 11 is a longitudinal front model view of a main part.

In FIG. 9 to FIG. 11, reference numeral 405 denotes a cylindrical sleeve having an electromagnetic induction heating layer (a conductor layer, a magnetic layer, and a resistor layer) as an electromagnetic induction heating rotor. Reference numerals 406a and 406b denote sleeve guide members having a substantially semi-arc-shaped trough-shaped cross section. The opening side faces each other to form a substantially columnar body, and a sleeve 405, which is a cylindrical electromagnetic induction heating belt, is loosely formed on the outside. It is fitted outside.

The sleeve guide member 406a includes magnetic cores 407a, 407b, and 407 as magnetic field generating means.
c and the exciting coil 408 are held inside. The magnetic cores 407a, 407b, and 407c are members having high magnetic permeability, and are generally made of a material used for a transformer core such as ferrite or permalloy.
It is preferable to use ferrite with a small loss even at 0 kHz or more.

The exciting coil 408 has a feeder 408a
08b is connected to the excitation circuit 701 (FIG. 12). The excitation circuit 701 generates a high-frequency current of about 20 kHz to 500 kHz, which will be described later in detail. Excitation coil 4
08 generates an alternating magnetic flux by an alternating current (high-frequency current) supplied from the excitation circuit 701.

The sleeve guide member 406a includes
As shown in FIG.
Reference numeral 4 denotes a nip portion N, which is located on the side facing the pressure roller 410, inside the sleeve 405. In this example,
Aluminum is used for the good heat conductive member 404. The good heat conducting member 404 has a heat conductivity k = 240 [W ·
m-1 · K-1], and the thickness is 1 [mm]. The good heat conducting member 404 is arranged outside the magnetic field so as not to be affected by the magnetic field generated from the exciting coil 408 as the magnetic field generating means and the magnetic cores 407a, 407b, 407c. Specifically, the good heat conducting member 404 is disposed at a position separated by the magnetic core 407c from the exciting coil 408, and is located outside the magnetic path formed by the exciting coil 408 to affect the good heat conducting member 404. I try not to.

Reference numeral 402 denotes a horizontally-long pressurizing rigid stay disposed in contact with the inner flat surface of the sleeve guide member 406b. 401 is a magnetic core 407a / 407b / 407
c and an insulating member for insulating the exciting coil 408 and the pressurizing rigid stay 402 from each other.

The flange members 502a and 502b are externally fitted to the left and right ends of the assembly of the sleeve guide members 406a and 406b, and are rotatably mounted while fixing the left and right positions. When the sleeve 405 rotates, the ends of the sleeves are received. Thus, it serves to regulate the movement of the sleeve along the length of the sleeve guide member.

The pressure roller 410 as a pressure member is made of a heat-resistant and elastic material layer of silicone rubber, fluoro rubber, fluoro resin, or the like, which is formed by concentrically forming a roller around a core metal 410a. 410b, and both ends of the cored bar 410a are rotatably supported and held between sheet metal on a chassis (not shown) of the apparatus.

Pressing springs 503a and 503b are contracted between both ends of the pressing rigid stay 402 and the spring receiving members 504a and 504b on the apparatus chassis side, so that a pressing force is applied to the pressing rigid stay 402. ing.
Thus, the lower surfaces of the sleeve guide members 406a and 406b and the upper surface of the pressure roller 410 are pressed against each other with the sleeve 405 interposed therebetween, thereby forming a nip portion N having a predetermined width.

The pressing roller 410 is driven to rotate in the counterclockwise direction shown by the arrow by the driving means M. This pressure roller 410
Rotational force acts on the sleeve by the frictional force between the pressure roller and the outer surface of the sleeve 405 due to the rotational drive of the roller, and the inner surface of the sleeve 405 comes into close contact with the lower surface of the good heat conducting member 404 at the nip portion N and slides. While moving, the outer circumference of the sleeve guide members 406a and 406b is rotated in a clockwise direction indicated by an arrow at a peripheral speed substantially corresponding to the rotational peripheral speed of the pressure roller 410 (pressure roller driving method).

In this case, in order to reduce the mutual sliding friction force between the lower surface of the good heat conducting member 404 at the nip N and the inner surface of the sleeve 405, the lower surface of the good heat conducting member 404 of the nip N and the sleeve 405 are reduced. A lubricant such as heat-resistant grease may be interposed between the inner surface and the inner surface, or the lower surface of the good heat conductive member 404 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 404, or when the finishing process is simplified, the sliding sleeve 405 is scratched and the durability of the sleeve is reduced. It is to prevent the property from being deteriorated.

The good heat conducting member 404 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 in the non-sheet passing portion of the sleeve 405 is reduced. To the small-size paper passing portion due to heat conduction in the longitudinal direction of the good heat conducting member 404. As a result, an effect of reducing power consumption when passing small-sized paper is also obtained.

Sleeve guide members 406a, 406b
Serves to press the nip N, support the exciting coil 408 and the magnetic core 407, support the sleeve 405, and improve the transport stability when the sleeve rotates. The sleeve guide members 406a and 406b are insulating members that do not hinder the passage of magnetic flux, and are made of a material that can withstand a high load.

As shown in FIG. 12, a convex rib 406c is formed on the peripheral surface of the sleeve guide member 406a at a predetermined interval along the length thereof, and the peripheral surface of the sleeve guide member 406a and the sleeve 405 are formed. The rotational load on the sleeve is reduced by reducing the contact sliding resistance with the inner surface of the sleeve. Such a convex rib portion 406c can be similarly formed and provided on the sleeve guide member 406b.

FIG. 13 is a diagram schematically showing the appearance of the generation of the alternating magnetic flux. FIG. 13A is a state diagram of the alternating magnetic flux C guided to the electromagnetic induction heating layer 801 and the magnetic cores 407a, 407b, and 407c. (b) is a graph showing a part of the alternating magnetic flux.

The alternating magnetic flux C guided to the magnetic cores 407a, 407b, and 407c is
07b, and between the magnetic core 407a and the magnetic core 40.
7c, an eddy current is generated in the electromagnetic induction heating layer 801 of the sleeve 405. The eddy current generates Joule heat (eddy current loss) in the electromagnetic induction heating layer due to the specific resistance of the electromagnetic induction heating layer 801. The heat value Q here is determined by the density of the magnetic flux passing through the electromagnetic induction heating layer 801 and has a distribution as shown in the graph of FIG.
In the graph of FIG. 13B, the vertical axis represents the magnetic core 407.
The position in the circumferential direction of the sleeve 405 is represented by an angle θ with the center of a being 0, and the horizontal axis represents the amount of heat generated in the electromagnetic induction heating layer 801 of the sleeve 405. 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 nip N is controlled by a temperature control system including a temperature detecting means so as to maintain a predetermined temperature by controlling the current supply to the exciting coil 408. Reference numeral 409 denotes a temperature sensor such as a thermistor for detecting the temperature of the sleeve 405, which is located on the downstream side in the paper transport direction with respect to the nip portion N and is provided so as to contact the inner wall of the sleeve 405 as shown in FIG. ing. The thermistor 409 measures the temperature of the sleeve 405 whose heat has been removed by the recording material P when passing through the nip N, and controls the heat generation of the sleeve due to induction heating.

Next, the operation will be described.

The pressure roller 410 is driven to rotate, and accordingly, the cylindrical sleeve 405 is rotated.
In the state where the electromagnetic induction heating of the sleeve 405 is performed as described above by the power supply to the excitation coil 408 from the power supply 1 and the nip portion N rises to a predetermined temperature and the temperature is controlled, the unfixed sheet conveyed from the image forming means portion The recording material P on which the toner image t is formed is introduced between the sleeve 405 of the nip portion N and the pressure roller 410 with the image surface facing upward, that is, facing the sleeve surface. In the process in which the image surface is closely attached to the outer surface of the sleeve 405 at the nip portion N and the nip portion is conveyed together with the sleeve 405, the unfixed toner on the recording material P is heated by electromagnetic induction heating of the sleeve 405. The image t is fixed by heating. When the recording material P passes through the nip portion N, the recording material P is separated from the outer surface of the rotating sleeve 405 and is discharged and conveyed. After passing through the nip portion, the heat-fixed toner image on the recording material is cooled and becomes a permanent fixed image.

In this embodiment, as shown in FIG. 9, a thermo switch 403, which is a temperature detecting element, is provided at a position facing the heat generating region H (FIG. 13) of the sleeve 405 to cut off power supply to the exciting coil 408 during runaway. Is arranged.

FIG. 14 shows the excitation coil 408 and the excitation circuit 70.
1 shows a circuit for generating an alternating magnetic field by an exciting current by connecting the exciting circuit 1 to the exciting circuit 701. The exciting circuit 701 generates a high-frequency current of about 20 kHz to 500 kHz.

Thermo switch 403 as a temperature detecting element
Is connected in series with the +24 VDC power supply and the relay switch 901, and when the thermo switch 403 is turned off, the power supply to the relay switch 901 is cut off, the relay switch 901 is operated, and the power supply to the excitation circuit 701 is cut off. Thus, a safety circuit for interrupting power supply to the excitation coil 408 is configured. The OFF temperature of the thermoswitch 403 is set to 220 ° C.

The thermo switch 403 is connected to the sleeve 4
It is disposed in a non-contact manner on the outer surface of the sleeve so as to face the heat generation area H of the thermometer 05, and the distance between the thermoswitch 403 and the sleeve 405 is approximately 2 mm. Thereby, the sleeve 4
No. 05 shows no damage due to contact of the thermoswitch 403, and can prevent deterioration of a fixed image due to durability.

According to this embodiment, unlike a configuration in which heat is generated in the nip portion N when the fixing device goes out of control due to a device failure, the nip portion N
When the recording material P is sandwiched in the nip portion N, the fixing device stops, power is supplied to the excitation coil 408, and the sleeve 405 continues to generate heat. The recording material is not directly heated because no heat is generated in the sandwiched nip portion N. Further, in the heat generation region H where the heat generation amount is large, the thermo switch 403 is used.
Is installed, the thermoswitch 403 is set to 220 ° C.
Is detected, and when the thermo switch is turned off, the power supply to the exciting coil 408 is cut off by the relay switch 901.

According to this embodiment, the ignition temperature of the recording material P is about 4
Since the temperature is around 00 ° C., the recording material does not ignite,
Heat generation of the sleeve 405 can be stopped. As the temperature detecting element, a temperature fuse can be used in addition to the thermoswitch 403.

In this embodiment, since a toner containing a low softening substance is used in the toner, an oil application mechanism for preventing offset is not provided in the fixing device, but a toner containing no low softening substance is used. May be provided with an oil application mechanism. Also, when a toner containing a low softening substance is used, oil application or cooling separation may be performed.

Hereinafter, the excitation circuit 701 will be described.

FIG. 15 shows the circuit configuration of the excitation circuit 701. In FIG. 15, reference numerals 711 and 715 denote switching elements, and frequently used elements such as MOSFETs and IGBTs. 712 and 716 are reverse conducting diodes, 713 is an exciting coil, and 714 and 717 are resonance capacitors. By turning on and off the switch elements 712 and 715 in such a circuit, single voltage resonance is performed.

FIG. 16 is a block diagram showing the overall configuration of the induction heating control unit.

1001 is a power line input terminal, 1002
Is a circuit breaker, 1003 is a relay, 1004
Is a rectifier circuit (RECT) composed of a bridge rectifier circuit that performs double-wave rectification from AC input and a capacitor that functions as a high-frequency filter, 1005 is a gate control transformer (GT), 1006 is a switching element, 1007 is a resonance capacitor, Reference numeral 1008 denotes a current transformer (C) for detecting the switching current switched at 1006.
At T), it is connected to the excitation coil 1010a of the fixing device.
Reference numeral 1010 denotes a fixing device unit, which includes the above-described excitation coil 1010a, a temperature detection thermistor (TH) 1010b, and a thermoswitch (T, SW) 1009 for detecting an excessive temperature rise as electric components. ing,
Reference numeral 1011 denotes an input of a heating ON / OFF signal of the fixing device transmitted from a printer sequence controller (not shown). Reference numeral 1012 controls a control amount based on a detected value of the thermistor temperature of the fixing device while comparing with a target temperature. A feedback (FB) control circuit 1013 is a driver circuit that receives a feed hack control signal and performs control according to the control mode of the converter.

An AC power input is received from a power line input terminal 1001, and a circuit breaker 1002 and a relay 1
When AC power is applied to the rectifier circuit 1004 via 003, a pulsating DC voltage is generated by the double-wave rectifier diode. Next, an AC pulse voltage is applied to a resonance circuit formed by the excitation coil 1010a and the resonance capacitor 1007 by driving the gate transformer 1005 so that the subsequent switching element 1006 performs switching. As a result, when the switching element 1006 is turned on, a pulsating DC voltage is applied to the exciting coil 1010a, and a current determined by the inductance and the resistance of the exciting coil 1010a starts flowing.

The switching element 10 according to the gate signal
06 is turned off, the exciting coil 1010a tries to keep the current flowing, so that the resonance capacitor 1010
07 and an exciting coil 1010a, a high voltage called a flyback voltage is generated. This voltage oscillates around the power supply voltage and converges to the power supply voltage if the off state is maintained as it is.

The ringing of the flyback voltage is large,
During a period in which the voltage of the coil side terminal of the switching element 1006 is negative, the reverse conducting diode is turned on, and a current flows into the exciting coil 1010a. During this period, the contact point between the exciting coil 1010a and the switching element 1006 is set to 0.
It will be clamped to V. It is generally known that if the switching element 1006 is turned on during such a period, it can be turned on without carrying a voltage.
is called. In such a case, the switching element 10
06 minimizes the loss associated with the switching, and enables efficient and low-noise switching.

The temperature of the fixing device is detected by a thermistor, and the resistance change of the thermistor is converted into a voltage, compared with a predetermined reference voltage, and detected as a difference from a target temperature. The ON time width is determined based on the detection result, and PWM control is performed based on the ON time width. PW
The M control part is composed of two pairs of constant current source circuits, an on-time control unit and an off-time control unit, a capacitor, and a comparator. The off-time control unit is stopped during the on-time, and the on-time control unit is turned off during the off-time. The on-time and the off-time, whose time widths are controlled sequentially, are repeatedly output by a steering flip-flop that stops the operation.

The off-time comparator is adjustable but has no feedback loop to control for a fixed time, and the temperature control is realized by feeding back temperature information to the on-time comparator.

The time during which current flows through the exciting coil 1010a,
That is, the maximum value of the ON time of the switching element 1006 is determined by the AC line voltage value and the power that can be supplied, and the control signal from the control circuit is in a range not exceeding the time. Further, a configuration for defining the minimum time may be provided.

For example, when the temperature of the fixing device is low when the power is turned on, for example, when the device is started up in the early morning, power is supplied in an ON time width close to the maximum time width.
When the power that can be supplied is 1100 W as an example, power is supplied at a maximum on time width of 1100 W from power-on until temperature control is performed, and the on-time width is increased by a signal of a thermistor that is a temperature detecting element. Limits and controls power.

The AC power from the power line input terminal 1001 enters the rectifier circuit 1004 via the circuit breaker 1002 for protecting against overcurrent and the relay 1003, where the exciting winding of the relay detects the temperature of the sleeve of the fixing device. When the sleeve temperature rises abnormally and exceeds the specified temperature,
If a trouble occurs and the fixing device abnormally rises in temperature, the relay 1003 is turned off to turn off the power of the excitation circuit, and the fixing device is disconnected from a thermal runaway. To ensure the safety.

In this case, for the sake of simplicity, the explanation has been made using a single voltage resonance type inverter as an example of the excitation circuit. However, other than the voltage resonance type, a current resonance type or a partial resonance type may be used. Any inverter that can generate AC may be used.

Hereinafter, the temperature control of the conventional fixing device will be described.

The fixing device using induction heating can perform highly efficient heating and the fixing member generates heat.
The fixable state is reached in about several tens of seconds after the power is turned on. With this performance, an on-demand fixing is realized in an image forming apparatus provided with a general induction heating fixing device.

However, an increase in the amount of heat required at the start-up due to an increase in the size of the apparatus and an increase in the demand for the first print time have led to an on-demand system that can satisfy the user even in a fixing apparatus using induction heating. Printing is becoming impossible. Therefore, in order to realize the first print time desired by the user, the image forming apparatus including the induction heating fixing device also performs the standby heating similarly to the heat roller method.

FIG. 17 is a control flowchart of a conventional example. Control based on this flowchart is performed by CPU or DSP.
In general, an arithmetic device such as the above is used, but the control unit may be constituted only by hardware.

When the power of the image forming apparatus is turned on (1101) and an appropriate process (checking of each part, etc.) is completed, the motor for driving the pressure roller is started to rotate the pressure roller (11).
02), the sleeve is driven. Next, power supply to the drive coil by the drive circuit is started to cause the sleeve to generate heat (1103). This power supply is performed until the detected temperature of the fixing device exceeds Ts ° C.

When the detection temperature ≧ Ts ° C. (1104),
A print request reception start state is set (1105), and at the same time, the supply is switched to a small amount of small power supply (1106). The supply of a fixed amount of small power means that a constant power of about several tens of watts is input 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, or a method of inputting a small amount of power approximately by intermittently operating the drive circuit, if the power can be reduced to a certain value or less. 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 supply and the heat radiation and heat conduction to the outside. The amount of heat dissipated varies depending on the outside air temperature, the amount of air, and the like. However, there is no problem since the temperature of the fixing device during standby does not require much accuracy. 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, when 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, when the high temperature is maintained, members constituting the fixing device, such as the sleeve and the pressure roller, and members around the fixing device generate thermal stress, which causes problems such as deformation and shortened life. The temperature range is set so as to be an appropriate value in consideration of these conditions. Generally, the temperature of the fixing device when printing on A3 paper is about 180 to 200 ° C., and when the first print time is 20 s or less, the temperature range is 100 ° C.
The temperature is preferably set to about 150 ° C., and particularly preferably 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 sleeve are stopped (1107). Continue constant small power (1108), P
When the image forming apparatus receives a print request from the host terminal such as C (1109), the driving of the pressure roller drive motor is started (1110), then the constant small power supply is stopped, and the fixing temperature control during printing is started. Then, the sleeve is further heated (1111). Heat generation of the sleeve is performed by the fixing temperature control during printing (1112), and when the detected temperature becomes equal to or higher than Tp ° C. (1113), the drive circuit performs power control to start temperature control to maintain the fixing device at Tp ° C. The device 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 (1114).
This printing operation is continued until the print request is completed, during which time the fixing device adjusts the fixing temperature during printing (111).
5). When the print request is completed, the fixing temperature control at the time of printing is stopped and switched to constant low power supply (1116), and constant low power supply is performed until the next print request occurs.

FIG. 18 shows the temperature transition of the fixing device during control in the conventional example.

As described in the control flowchart, when the temperature exceeds the fixing device temperature Ts.degree.
The temperature at this time converges to an appropriate temperature. When a print request is accepted, heating is started, and control is performed to keep the temperature regulation temperature Tp ° C constant. When printing is completed, a constant low power is input again, and the temperature converges to an appropriate temperature over time.

[0059]

However, in the fixing device based on the electromagnetic induction heating method shown in the conventional example, in the control during standby, the heating is performed in a state where the sleeve is stopped in order to reduce the power during standby heating. Is going. At this time, the heat generated by the sleeve has a temperature gradient as shown in FIG. 13B, and the heat is concentrated on a part of the sleeve. There were challenges. In addition, there is a problem in that a part of the sleeve is deteriorated to cause fixing unevenness.

The present invention has been made to solve the above-mentioned conventional problems, and it is an object of the present invention to provide a heating apparatus using an electromagnetic induction heating method, which prevents local thermal fatigue of a sleeve during standby heating. Aim. Further, applying the heating device as a fixing device for heating and fixing an unfixed toner image formed on a recording material as a material to be heated to the recording material,
It is an object of the present invention to provide an image forming apparatus capable of preventing deterioration in image quality at the time of fixing and forming a high-quality image.

[0061]

According to the present invention, there is provided a heating device having the following constitution, and an image forming apparatus using the heating device as a fixing device. (1) An electromagnetic induction heating member that generates heat by the action of the magnetic field of the magnetic field generating means, and a pressing member that forms a nip by mutual pressure contact with the electromagnetic induction heating member. In a heating device that performs heating temperature control using the first control means during the heating operation passing through the nip portion, and performs standby temperature control using the second control means during standby when the material to be heated does not pass through the nip portion. And a heating position changing means for changing a heating position of the electromagnetic induction heating member for each predetermined condition during the standby temperature control. (2) The heating device according to claim 1, wherein the predetermined condition is whether or not a heat generation time of the electromagnetic induction heating member has exceeded a predetermined time t. (3) A temperature detecting means for detecting a temperature of the electromagnetic induction heating member, wherein the predetermined condition is whether or not a temperature detected by the temperature detecting means exceeds a predetermined temperature. 2. The heating device according to 1. (4) The apparatus according to claim 1, further comprising a temperature detecting unit for detecting a temperature of the electromagnetic induction heating member, wherein the predetermined condition is whether or not a temperature detected by the temperature detecting unit is saturated. Heating equipment. (5) a heat generating position changing means for changing a heat generating position of the electromagnetic induction heat generating member to an arbitrary position; and a heat generating position setting table storing setting of a heat generating position of the electromagnetic induction heat generating member, wherein the heat generating position is provided. The heating device according to any one of (1) to (4), wherein the heat generation position is sequentially changed by the heat generation position changing means in accordance with the setting data stored in the setting table. (6) In the image forming apparatus having an image forming unit that forms an unfixed toner image on the surface of the material to be heated and a heat fixing unit that heats and fixes the unfixed toner image on the surface of the material to be heated, An image forming apparatus, wherein the heating device according to any one of (1) to (5) is applied as a fixing unit.

[0062]

(First Embodiment) FIG. 1 is a view for explaining an entire image forming apparatus according to an embodiment of the present invention.
This embodiment shows a color image forming apparatus provided with image forming means (image forming section) for four colors, that is, yellow Y, magenta M, cyan C, and black K. In the figure, reference numeral 201 denotes an electrostatic latent image. Forming a photosensitive drum (a,
b, c, and d indicate K, C, M, and Y, respectively); 202, a laser scanner that performs exposure according to an image signal to form an electrostatic latent image on the photosensitive drum 201; Reference numeral 204 denotes a fixing device (heat fixing unit) for heating and fixing the toner image formed on the recording material to the recording material, the endless conveyance belt also serving as a transfer belt for sequentially conveying the toner image to the image forming unit.

When data to be printed is sent from a PC (Personal Computer) to the printer, and the image formation in accordance with the printer engine system is completed and the printer becomes ready for printing, a recording material is supplied from a paper cassette to the transport belt 203. Then, the recording material is sequentially conveyed by the conveying belt 203 to the image forming units of each color. The image signal of each color is sent to each laser scanner 202 in accordance with the recording material conveyance by the conveyance belt 203 and the timing, and the photosensitive drum 20
An electrostatic latent image is formed on the recording medium 1, toner is developed by a developing unit (not shown), and is transferred onto a recording material by a transfer unit (not shown).

In FIG. 1, images are sequentially formed in the order of Y, M, C, and K. Thereafter, the recording material is separated from the transport belt 203, and the toner image is fixed on the recording material by heat in the fixing device 204, and is discharged to the outside. The fixing device 204 according to the present exemplary embodiment employs the heating device of the present invention. In the following description, the heating device will be described as the fixing device 204.

In the image forming apparatus described above, the fixing device 204 using induction heating in the print request accepting state, that is, in the standby state, is controlled by a control device such as a CPU or a DSP (not shown) as described below. It is controlled according to the device standby sequence.

FIG. 2 is a control flowchart of a first embodiment in which the heating device of the present invention is applied as a fixing device, and FIG. 3 is a block diagram for explaining a schematic configuration of the fixing device in the present embodiment. Hereinafter, description will be made with reference to FIGS.

When the image forming apparatus enters the standby state and the control apparatus starts the fixing apparatus standby sequence (10)
1) The standby temperature control of the fixing device is started (10).
2). This standby temperature control may be any method as long as the standby heating is performed while the sleeve 306 is stopped. For example, the constant power input control described in the conventional example or the temperature control using a thermistor (in this case, the target temperature needs to be set low because the heat generation position and the temperature detection position are different) may be used. At this time, as described in the conventional example, C
A control device such as the PU 301 controls the power inverter 304 to drive the exciting coil 307 with low power, thereby causing the sleeve 306 to generate heat and performing standby heating.

When the standby temperature control starts, the CPU 30
1 resets the variable (time t) to t = 0. Thereafter, the counting of the time variable t is started (10
3). The value of the time variable t indicates the heating time at the current heating position of the sleeve.

The control device always checks whether there is a request to end the standby sequence of the fixing device (104), and counts the time t. When a request to end the standby sequence of the fixing device is generated, the standby temperature control is ended (1).
06), the fixing device standby sequence is terminated (10)
7).

The time variable t increases and the ROM 302
If it exceeds the set value Th stored in advance in the storage device (105), the driving motor 303 of the fixing device is driven for a fixed time Td (106). Driving motor 3 for fixing device
When the drive unit 03 is driven, the pressure roller 305 in the fixing device rotates, and the sleeve 306 is rotated following the pressure roller 305, so that the heat generation position in the sleeve 306 is changed. After that, the time variable t is reset and the sleeve 30 is reset.
The counting of the time variable t of the heating time at the new heat generation position of No. 6 is started (103).

At this time, the predetermined time Tb is preferably set so that the same portion does not generate heat even if the heating position is changed a plurality of times. More preferably, the maximum standby set time (for example, about 15 minutes) is set. It is preferable to set so that the same portion is not heated even if the change is made.

In the present embodiment, it has been described that the driving amount of the driving motor of the fixing device is driven for a predetermined time Td. But,
It is not always necessary to specify the time, and for example, a method of rotating the rotation angle of the drive motor or the sleeve by a fixed angle may be performed. 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. 4 shows a control flowchart of the second embodiment, and FIG. 5 shows a schematic configuration in the present embodiment. Hereinafter, description will be made with reference to FIGS.

The image forming apparatus enters the standby state, and the control apparatus starts the fixing apparatus standby sequence (1301).
Then, the standby temperature control of the fixing device is started (130).
2). At this time, similarly to the first embodiment, the control device such as the CPU 301 controls the power inverter 304 and drives the exciting coil 307 with low power, so that the sleeve 306 is controlled.
To generate heat and perform standby heating.

When the standby temperature control is started, the control device always checks whether or not there is a request for terminating the standby sequence of the fixing device (1303). The temperature control ends (1306), and the fixing device standby sequence ends (1307).

If there is no request to end the standby sequence, the temperature k detected by the thermistor 1401 is checked,
When the temperature exceeds a preset temperature Kh stored in advance in a storage device such as 02, the driving motor 303 of the fixing device is driven for a predetermined time Td (1305).

Further, instead of the above-described determination method, the condition that the detected temperature k of the thermistor 1401 is saturated may be used as a condition, and the drive motor 303 may be driven when it is saturated. It is desirable that the mounting position of the thermistor 1401 is a position where the temperature of the heat generating position can be directly detected. However, it is not always necessary to directly detect the temperature of the heat generation position. Even if the heat generation position and the temperature detection position are different from each other as in the conventional example, the heat generation position and the surrounding temperature can be indirectly estimated by heat conduction. No problem. Although the set temperature Kh varies depending on the configuration of each fixing device, according to experiments conducted by us, it is preferable to set the temperature at about 70 to 100 ° C. at the thermistor position described in the conventional example.

When the driving motor 303 of the fixing device is driven, the pressure roller 305 in the fixing device is rotated, and the sleeve 306 is rotated following the pressure roller 305, so that the heat generation position in the sleeve 306 is changed. . After the change of the heating position, the end request of the standby sequence is checked again and the detection temperature k of the thermistor is checked. (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 this embodiment are the same as those in the first and second embodiments, and thus description thereof will be omitted.

FIG. 6 shows a control flowchart of the third embodiment, and FIG. 7 shows a schematic configuration of the third embodiment. Hereinafter, description will be made with reference to FIGS.

When the image forming apparatus enters the standby state and the control apparatus starts the fixing apparatus standby sequence (150)
1) The standby temperature control of the fixing device is started (150).
2). At this time, similarly to the first embodiment, the control device such as the CPU 301 controls the power inverter 304 and drives the exciting coil 307 with low power, so that the sleeve 306 is controlled.
To generate heat and perform standby heating.

When the standby temperature control starts, the CPU 30
Reference numeral 1 refers to the previous stop position of the sleeve stored in the ROM 302, and drives the drive motor of the fixing device to the position set as the next stop position after the previous stop position based on the information of the position detection unit ( 1503).

FIG. 8 shows an explanation of the position detecting section at this time.
In the figure, reference numeral 405 denotes a sleeve, 1701 denotes a position reference flag of the sleeve 405 fixed so as to rotate corresponding to the end of the sleeve, and 1702 denotes a photo interrupter as a position detecting element for detecting the position of the flag 1701.

In the above configuration, the position where the flag 1701 blocks the photo interrupter 1702 is used as a reference.
The position is calculated based on the drive time and drive angle of the drive motor of the fixing device. At this time, several to ten and several stop positions are determined in advance, and the positions are stored in the ROM 302.
The plurality of stop positions are rotated, and the stop positions are sequentially changed to the next position.

The CPU 301 always checks whether there is a request to end the standby sequence of the fixing device (150).
4) When a request to end the standby sequence of the fixing device is issued, the standby temperature control is ended (1507), and the fixing device standby sequence is ended (1508).

When there is no request for terminating the standby sequence, if the temperature and time conditions as described in the first and second embodiments are satisfied, the driving motor 3
03 is driven (1505), the sleeve 306 is rotated to the next stop position, and the drive motor 303 of the fixing device is stopped at a desired position. After the heat generation position is changed, the CPU 301 checks again the end request of the standby sequence and the temperature and time conditions.

By using the above-described method, the heat generation position during standby is rotated, and it is possible to prevent uneven generation of heat, thereby preventing local deterioration.

In each of the embodiments described above, the case where the heating device of the present invention is applied to a fixing device has been described. However, the heating device of the present invention can also be applied to wrinkling and polishing of a material to be heated. it can.

[0087]

As described above, according to the present invention,
In the heating device of the electromagnetic induction heating system, the heating position of the electromagnetic induction heating member is changed for each predetermined condition during standby heating, so that local heating of the electromagnetic induction heating member can be prevented. As a result, local deterioration due to thermal fatigue can be prevented, and there is an effect of reducing a reduction in the life of the electromagnetic induction heating member.

Further, by applying this heating device to the fixing device, it is possible to prevent temperature unevenness and wrinkles caused by the deterioration of a part of the electromagnetic induction heating member,
There is an effect that an image forming apparatus capable of preventing deterioration in image quality at the time of fixing and performing high-quality image formation can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating an overall configuration of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a view for explaining a control flowchart of the fixing device according to the first embodiment of the present invention.

FIG. 3 is a block diagram illustrating a schematic configuration of a fixing device according to an embodiment of the present invention.

FIG. 4 is a diagram illustrating a control flowchart of a fixing device according to a second embodiment of the present invention.

FIG. 5 is a block diagram illustrating a schematic configuration of a fixing device according to a second embodiment of the present invention.

FIG. 6 is a diagram illustrating a control flowchart of a fixing device according to a third embodiment of the present invention.

FIG. 7 is a block diagram illustrating a schematic configuration of a fixing device according to a third embodiment of the present invention.

FIG. 8 is a perspective view illustrating a position detection unit of a fixing device according to a third embodiment of the present invention.

FIG. 9 is a schematic cross-sectional side view of a main part of a conventional fixing device.

FIG. 10 is a front model diagram of a main part of the fixing device.

FIG. 11 is a longitudinal front model view of a main part of the fixing device.

FIG. 12 is a diagram showing a relationship between a magnetic field generation unit of the fixing device and an excitation circuit.

FIG. 13 is a diagram showing a relationship between a magnetic field generating means of the fixing device and a heat generation amount Q.

FIG. 14 is a diagram showing a safety circuit of the fixing device.

FIG. 15 is a circuit diagram of an excitation circuit.

FIG. 16 is an overall configuration block diagram of an induction heating control unit.

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

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

[Explanation of symbols]

 201 (201a to 201d) Photosensitive drum 202 (202a to 202d) Laser scanner 203 Conveying belt 204 Fixing device 405 Sleeve 406 (406a, 406b) Belt guide 407 (407a to 407c) Magnetic core 408 Magnetic coil 409 Temperature detecting element (thermistor) 410 Pressure roller 701 as pressure member Excitation circuit 901 Temperature detecting element for safety

Continuing on the front page F-term (reference) 2H033 AA02 AA23 BA11 BA12 BA25 BA27 BA31 BA32 BE06 CA05 CA22 CA32 CA48 3K059 AA08 AB27 AB28 AC33 AC35 AC54 AD34 CD09 CD18 CD23 CD77 5H323 AA36 BB03 BB17 CA08 CB06 DA01 DB01 EE03 LL01 GG01 MM08 TT06

Claims (6)

[Claims] An object to be heated, comprising: an electromagnetic induction heating member that generates heat by the action of a magnetic field of a magnetic field generating means; Performs heating temperature control using the first control means during a heating operation passing through the nip portion, and performs standby temperature control using the second control means during standby when the material to be heated does not pass through the nip portion. A heating device, comprising: a heating position changing unit that varies a heating position of the electromagnetic induction heating member for each predetermined condition during the standby temperature control. 2. The heating device according to claim 1, wherein the predetermined condition is whether or not a heat generation time of the electromagnetic induction heating member has passed a predetermined time. 3. The apparatus according to claim 2, further comprising a temperature detecting means for detecting a temperature of said heat generating member, wherein said predetermined condition is whether or not a temperature detected by said temperature detecting means exceeds a predetermined temperature. The heating device according to claim 1. 4. The apparatus according to claim 1, further comprising temperature detecting means for detecting a temperature of said electromagnetic induction heating member, wherein said predetermined condition is whether or not a temperature detected by said temperature detecting means is saturated. 2. The heating device according to 1. 5. A heat generating position changing means for changing a heat generating position of the electromagnetic induction heat generating member to an arbitrary position, and a heat generating position setting table for storing setting of a heat generating position of the electromagnetic induction heat generating member, The heating device according to any one of claims 1 to 4, wherein the heat generation position is sequentially changed by the heat generation position changing means according to the setting data stored in the heat generation position setting table. 6. An image forming apparatus comprising: an image forming section for forming an unfixed toner image on a surface of a material to be heated; and a heat fixing section for heating and fixing the unfixed toner image on the surface of the material to be heated. An image forming apparatus to which the heating device according to claim 1 is applied as the heat fixing unit.