JP2002008845A - Heating device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heating device and an image forming device solving the problem that a stable conveying of a material to be recorded cannot be realized. SOLUTION: In an electromagnetic induction heating device driven by a press roller, a rotation detection means is provided on a fixing belt and a rotation speed of the fixing belt is monitored. The rotation speed of the press roller is controlled such that the rotation speed of the fixing belt becomes approximately constant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic induction heating type heating device, and an image forming apparatus such as an electrophotographic apparatus and an electrostatic recording device provided with the heating device as an image heating device.

[0002]

2. Description of the Related Art For convenience, an image heating apparatus (fixing apparatus) provided in an image forming apparatus such as a copying machine or a printer and heating and fixing a toner image on a recording material will be described as an example of a heating apparatus.

In an image forming apparatus, a recording material (transfer material sheet, electrofax sheet, electrostatic recording paper, OHP sheet) is used by an appropriate image forming process means such as an electrophotographic process, an electrostatic recording process, and a magnetic recording process.・
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, belt heating type devices have 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 basically has a rotating pressure roller pair of a fixing roller (heating roller) and a pressure roller, and an image should be fixed to a fixing nip portion which is a mutual pressure contact portion of the roller pair. The recording material on which the unfixed toner image is formed and carried is introduced, nipped and conveyed, and the unfixed toner image is hot-pressed and fixed on the recording material surface by the heat of the fixing roller and the pressing force of the fixing nip. .

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 film heating system is disclosed in, for example,
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 (hereinafter, referred to as a film or a fixing belt) between a ceramic heater as a heating element and a pressing roller as a pressing member. By introducing a recording material on which an unfixed toner image to be image-fixed is formed and supported between the film and the pressure roller of the section and holding and transporting the same together with the film, the heat of the ceramic heater in the nip portion is reduced. The unfixed toner image is applied to the recording material via the film, and the unfixed toner image is heat-pressure-fixed to the recording material surface by the pressing force of the nip portion.

This film heating type fixing device can be constituted as an on-demand type device using a ceramic heater and a member having a low heat capacity as a fixing film, and a ceramic as a heat source only when the image forming apparatus performs image formation. What is necessary is just to energize the heater to generate heat 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 large. Has the advantage of being small (power saving).

However, 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, is required to wrap and uniformly fuse an image. It is necessary to provide a rubber elastic layer on the outer periphery of the film. Since the rubber elastic layer has a large heat capacity, the quick start characteristic which is a feature of the film heating device is lost.

Further, there is a problem in the amount of heat supply as a full-color image forming apparatus requiring a large amount of heat or a fixing device for a high-speed model. 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, the density of fixing energy with respect to the input energy is low, and the efficiency is low. 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 the heating element, or the alternating magnetic flux distribution of the exciting coil is concentrated near the fixing nip portion. An efficient fixing device has been proposed.

FIG. 19 is a schematic configuration diagram showing an example of an 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. In FIG. 19, reference numeral 10 denotes an electromagnetic induction heating layer (a conductor layer, a magnetic layer,
A cylindrical fixing belt as a heating rotator that generates electromagnetic induction heat and has a resistance layer.

Numeral 16 denotes a gutter-shaped belt guide member having a substantially semi-circular cross section. The cylindrical fixing belt 10 is loosely fitted outside the belt guide member 16. Numeral 15 denotes a magnetic field generating means disposed inside the belt guide member 16 and comprises an exciting coil 18 and an E-shaped magnetic core (core material) 17.

Numeral 30 denotes an elastic pressure roller as a pressure member, and the belt guide member 16 sandwiches the fixing belt 10 therebetween.
Nip N having a predetermined width with a predetermined pressing force against the lower surface of
Are formed and mutually pressed. The magnetic field generating means 1
The magnetic core 17 of No. 5 is disposed so as to correspond to the fixing nip portion N.

The pressure roller 30 is rotationally driven by a driving means M in a counterclockwise direction indicated by an arrow. A rotational force acts on the fixing belt due to a frictional force between the pressing roller and the outer surface of the fixing belt 10 due to the rotational driving of the pressing roller 30, and the inner surface of the fixing belt 10 The outer circumference of the belt guide member 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 30 while sliding in close contact with the lower surface of the member 16 (pressure roller drive system). ).

The belt guide member 16 has a fixing nip portion N
, And supports the exciting coil 18 and the magnetic core 17 as the magnetic field generating means 15, supports the fixing belt 10, and improves the conveyance stability when the fixing belt 10 rotates. The belt guide member 16 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 18 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 17 corresponding to the position of the fixing nip N, and the alternating magnetic flux is applied to the electromagnetic induction heating layer of the fixing belt 10 at the fixing nip N. Generates eddy currents. This eddy current generates Joule heat in the electromagnetic induction heating layer due to the sticking resistance of the electromagnetic induction heating layer.

The electromagnetically induced heat of the fixing belt 10 is intensively generated in the fixing nip N where the alternating magnetic flux is intensively distributed, and the fixing nip is heated with high efficiency. The temperature of the fixing nip N is controlled so as to be maintained at a predetermined temperature by controlling the current supply to the exciting coil 18 by a temperature control system including a temperature detecting unit (not shown).

Thus, the pressure roller 30 is driven to rotate,
Accordingly, the cylindrical fixing belt 10 rotates around the belt guide member 16 and moves from the excitation circuit to the excitation coil 18.
When the fixing nip N is raised to a predetermined temperature and the temperature is adjusted by the electromagnetic induction heating of the fixing belt 10 as described above by the power supply to the fixing belt 10, the fixing belt 10 is conveyed from an image forming unit (not shown). The recording material P on which the toner image t is formed is introduced between the fixing belt 10 and the pressure roller 30 in the fixing nip portion N with the image surface facing upward, that is, opposed to the fixing belt surface. At the time, the image surface comes into close contact with the outer surface of the fixing belt 10, and the fixing nip N is conveyed together with the fixing belt.

In the process in which the recording material P is nipped and conveyed in the fixing nip portion N together with the fixing belt 10, the unfixed toner image t on the recording material P is heated by electromagnetic induction heating of the fixing belt 10. Is heat-fixed. When the recording material P passes through the fixing nip portion N, it is separated from the outer surface of the rotary fixing belt 10 and is discharged and conveyed.

[0023]

SUMMARY OF THE INVENTION In order to realize a quick start, in a heating device of an electromagnetic induction heating system,
When a fixing belt having a small heat capacity is employed, it is difficult to obtain a rigidity enough to directly drive the fixing belt. Therefore, the fixing belt is driven by a configuration driven by a pressure roller or the like.

Therefore, in the heating device of the electromagnetic induction heating system in which the fixing belt is driven by the pressing roller, if the pressing roller and the fixing belt slip at the start of the rotation of the pressing roller and the fixing belt does not rotate, the heat capacity is reduced. In a small fixing belt, the temperature of the heat generating region may be excessively high, and the fixing belt may be damaged. In particular, when the heat generation region extends outside the nip, the temperature rise rate is much higher than that of the conventional film heating type fixing device, so that the possibility of damaging the fixing belt was further increased.

Further, when the recording material enters the fixing nip while the fixing belt is not rotating, the recording material cannot pass through the fixing nip, and a jam may occur.

In the heating device of the electromagnetic induction heating type in which the fixing roller is driven by the pressing roller, when the elastic layer of the pressing roller thermally expands, the outer peripheral length of the pressing roller becomes longer.
When the pressure roller shaft is rotated at a constant speed in this state, if the temperature of the pressure roller rises, the transport distance per rotation increases. Therefore, when using the Quick Start, when the heating is started from around room temperature and the pressure roller temperature is low when the pressure roller temperature is low, and when the pressure roller temperature increases during continuous printing There is a problem that the paper transport speed changes with the transport speed of the recording material.

In a conventional heating device driven by a pressure roller, in an image forming apparatus in which the conveyance speed of a fixing nip changes,
The distance between the transfer nip and the fixing nip is increased, and a transfer path is formed in a valley for providing a loop to the recording material there to absorb a difference in the transfer speed between the fixing nip and the transfer nip. There was something.

However, since the distance between the transfer nip and the fixing nip becomes long, there is a problem that the apparatus body becomes large and the first print time becomes long. Also, in the case of a recording material such as thick paper having a strong stiffness, the transfer nip and the fixing nip are not connected along the valley-shaped transfer path, and the transfer nip and the fixing nip are linearly connected. There was a problem that the image was stretched.

Further, with a conventional heating device driven by a pressure roller, the temperature of the pressure roller is predicted from the number of prints, and the rotation speed of the pressure roller is changed to shorten the distance between the transfer nip and the fixing nip. Although some image forming apparatuses have been devised to prevent the image from growing, it is difficult to make predictions for all environments and types of recording materials. Was.

In a monochrome image forming apparatus or a color image forming apparatus, when a color image is collectively transferred to a recording material using an intermediate transfer member, the image is stretched. Even in an image forming apparatus, when a plurality of photoconductors are arranged in tandem on a fixing belt and a toner image is sequentially transferred to a recording material, the recording material enters the fixing nip while straddling a plurality of transfer nips. May be.

In this state, if the recording material conveyance speed at the fixing nip changes, color misregistration may occur, and the image quality may be significantly reduced. In a tandem type color image forming apparatus, it is necessary to arrange a plurality of photosensitive drums substantially in a line, so if the distance between the final transfer nip and the fixing is set to be large enough to absorb a change in the conveying speed, the apparatus becomes large. There was a problem.

Accordingly, the present invention has been made to solve the above-described problem. In a heating device of an electromagnetic induction heating system driven by a pressure roller as a driving roller having an elastic layer, rotation of a fixing belt is detected. By realizing it with an inexpensive configuration, damage to the fixing belt is prevented.

Further, by detecting the rotation speed of the fixing belt,
By feeding back the change in the rotation speed of the fixing belt to the rotation speed of the pressure roller, the change in the conveyance speed of the recording material due to the change in the outer diameter of the pressure roller can be corrected, and the recording material can be conveyed at a stable speed. It is an object to provide a heating device.

As the image heating device, the above-mentioned heating device is provided.
It is an object to provide an image forming apparatus capable of forming a high-quality image.

[0035]

According to the present invention, there is provided a heating apparatus and an image forming apparatus having the following constitution. (1) A heating rotator that generates electromagnetic induction by the action of a magnetic field of a magnetic field generating means, a driving rotator that has an elastic layer that drives the heating rotator by frictional force, and rotation detection that detects rotation of the heating rotator. A heating apparatus comprising: means for detecting a rotation speed using the rotation detection means; and controlling the rotation speed of the driving rotator based on the detected rotation speed. (2) The heating device according to (1), wherein the driving rotator is a pressurizing rotator that forms a nip portion by mutual pressure contact with the heat generating rotator. (3) The heating device according to (1) or (2), wherein a rotation detection pattern is formed on the surface of the heating rotator. (4) The heating device according to (1) or (2), wherein a rotation detection pattern is formed on an auxiliary member that rotates together with the heating rotator. (5) The heating device according to (1) or (2), wherein a transmission unit for directly transmitting the rotation of the heating rotator is provided, and the rotation detection pattern is formed on the transmission unit. (6) The heating device according to any one of (3) to (5), wherein a rotation speed is detected from the rotation detection pattern using the rotation detection unit. (7) The heating device according to any one of (1) to (6), wherein the heating rotary body is an endless belt. (8) The heating device according to (7), wherein the heat generation area of the endless belt is located above the entry side of the recording material in the nip portion. (9) The heating device according to any one of (1) to (7), wherein the rotation detecting unit can simultaneously detect a conveyance state of the recording material. (10) When the rotation of the heating rotator is not detected even though the driving rotator is rotating, stopping the heat generation of the heating rotator and stopping the rotation of the driving rotator are described. The heating device according to any one of (1) to (8), which is characterized in that: (11) an image forming means for forming an image on a recording material;
A heating device according to any one of (1) to (10), wherein the heating device is provided as an image heating device for heating an image formed on a recording material by the image forming means. An image forming apparatus comprising: (12) There is a plurality of image forming means for forming an image on the recording material, and at least one of the portions for forming an image on the recording material and the nip portion simultaneously pinch and transport the recording material. The image forming apparatus according to (11). (13) The image forming apparatus according to (11) or (12), wherein the recording material is transported substantially vertically.

[0036]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) Fixing Device (Heating Device) 100 FIG. 1 is a schematic front view of a main part of a fixing device 100 using a heating device of the present invention, and FIG. 2 is a main portion in FIG. FIG. 3 is a longitudinal sectional front view of a main part.

The heating device 100 is a pressure roller driving system and an electromagnetic induction heating system using a cylindrical electromagnetic induction heating belt, similarly to the conventional apparatus shown in FIG. The same components as those of the apparatus of FIG. 19 are denoted by the same reference numerals, and the description thereof will not be repeated.

The magnetic field generating means comprises magnetic cores 17a and 17b and an exciting coil 18. The magnetic cores 17a and 17b are members having a high magnetic permeability, and are preferably made of a material used for a transformer core such as ferrite or permalloy, and more preferably ferrite which has little loss even at 100 kHz or more. The exciting coil 18 has a feeder 18a
The excitation circuit 27 (FIG. 4) is connected to 8b. The excitation circuit 27 can generate a high frequency of 20 kHz to 500 kHz by a switching power supply. The exciting coil 18 generates an alternating magnetic flux by an alternating current (high-frequency current) supplied from the exciting circuit 27.

Reference numerals 16a and 16b denote belt guide members of a trough type having a semi-circular cross section having a substantially semicircular arc shape. 10 is loosely fitted.
The belt guide member 16a holds magnetic cores 17a and 17b as magnetic field generating means and an exciting coil 18 inside.

Reference numeral 22 denotes a horizontally long pressing rigid stay disposed in contact with the inner flat surface of the belt guide member 16b. 19 is a magnetic core 17a / 17b and an exciting coil 18
It is an insulating member for insulating between the pressurizing rigid stay 22 and the pressing rigid stay 22. Pressing springs 25a and 25b are respectively contracted between both ends of the pressing rigid stay 22 and the apparatus chassis side, thereby applying a pressing force to the pressing rigid stay 22. As a result, the lower surface of the belt guide member 16a and the upper surface of the pressure roller 30 are pressed against each other with the fixing belt 10 interposed therebetween, thereby forming a fixing nip portion N having a predetermined width.

The pressure roller 30 is rotationally driven by a driving means M in the counterclockwise direction shown by the arrow. A rotational force acts on the fixing belt by the frictional force between the pressing roller 30 and the outer surface of the fixing belt 10 due to the rotational driving of the pressing roller 30, and the inner surface of the fixing belt 10 is a sliding member at the fixing nip N. The outer circumference of the belt guide members 16a and 16b is rotated at a peripheral speed substantially corresponding to the rotational peripheral speed of the pressure roller 30 in the clockwise direction indicated by the arrow while sliding in close contact with the lower surface of the belt 40.

In this case, in order to reduce the mutual sliding friction force between the lower surface of the sliding member 40 and the inner surface of the fixing belt 10 at the fixing nip N, the sliding member 40 of the fixing nip N
A lubricant such as heat-resistant grease may be interposed between the lower surface of the fixing belt 10 and the inner surface of the fixing belt 10. This is because when the surface sliding property is not good in material such as the case where alumina is used as the sliding member 40 or when the finishing process is simplified, the sliding fixing belt 10 is damaged and the fixing belt 1 is damaged.
This is to prevent the durability of No. 0 from deteriorating.

The pressure roller 30 as a pressure member includes a core metal 30a, and a heat-resistant and elastic material layer 30b such as silicone rubber or fluorine rubber which is formed and coated concentrically around the core metal as a roller. It has a structure with a release layer 30c such as a fluororesin provided on the surface layer and having good releasability. Both ends of the core metal 30a are rotatably supported between the chassis side metal plates of the apparatus.
・ It is arranged to be held by 29b.

The flange members 23a and 23b are fixedly attached to both ends of the fixing belt 10. The belt guide members 16a and 16b are externally fitted to both left and right ends of the assembly, and the left and right positions are adjusted by the flange regulating members 24a and
The fixing belt 10 is rotatably mounted while being regulated by 4b.
During rotation of the fixing belt, the fixing belt 10 receives the end of the fixing belt in a circular shape to regulate the shifting of the fixing belt 10 along the length of the belt guide member and to prevent the fixing belt end from being damaged.

As shown in FIG. 5, the belt guide member 16
A convex rib portion 16e is formed on the peripheral surface of the fixing belt 10 at predetermined intervals in the longitudinal direction of the fixing belt 10 to reduce contact sliding resistance between the peripheral surface of the belt guide member 16a and the inner surface of the fixing belt 10. 10, the rotational load is reduced. Such a convex rib portion can be similarly formed and provided on the belt guide member 16b.

FIG. 5 schematically shows how the alternating magnetic flux is generated. The magnetic flux C represents a part of the generated alternating magnetic flux. As shown in FIG. 5A, the magnetic cores 17a and 17b
The alternating magnetic flux (C) guided to the magnetic core 17a generates an eddy current in the electromagnetic induction heating layer 1 of the fixing belt 10 between the magnetic core 17a and the magnetic core 17b. This 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 1. The heat value Q here is determined by the density of the magnetic flux passing through the electromagnetic induction heating layer 1, and has a distribution as shown in the graph of FIG. In the graph shown in FIG. 5B, the vertical axis shows the position in the circumferential direction of the fixing belt 10 represented by an angle θ where the center of the magnetic core 17 a is 0, and the horizontal axis shows the electromagnetic induction heating layer of the fixing belt 10. The calorific value Q at 1 is shown. 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 18 by a temperature control system including a temperature detecting means (not shown). Reference numeral 26 denotes a temperature sensor such as a thermistor for detecting the temperature of the fixing belt 10. In this embodiment, the temperature of the fixing nip N is controlled based on the temperature information of the fixing belt 10 measured by the temperature sensor 26. I have.

As the fixing belt 10 rotates, the electromagnetic induction heat of the fixing belt 10 is generated as described above by the power supply from the excitation circuit 27 to the excitation coil 18, and the fixing nip N rises to a predetermined temperature. Unfixed toner image t conveyed from the image forming unit in the state where the temperature is adjusted
Is formed between the fixing belt 10 and the pressure roller 30 in the fixing nip portion N with the image surface facing upward, that is, opposed to the fixing belt surface. The fixing nip N is conveyed together with the fixing belt 10 in close contact with the outer surface of the fixing belt 10. This fixing nip portion N is fixed to the recording material P together with the fixing belt 10.
Is heated by the electromagnetic induction heat of the fixing belt 10, and the unfixed toner image t on the recording material P is heated and fixed. The recording material P is a fixing nip N
, The sheet is separated from the outer surface of the rotary fixing belt 10 and is discharged and conveyed. After passing through the fixing nip, the heat-fixed toner image on the recording material is cooled and becomes a permanent fixed image.

In this embodiment, as shown in FIG. 6, a thermo-switch 50, which is a temperature detecting element for interrupting power supply to the exciting coil 18 during runaway, is provided at a position facing the heat generating area H of the fixing belt 10. are doing.

FIG. 6 is a circuit diagram of the safety circuit used in this example. Thermo switch 50 which is a temperature detecting element has
The VDC power supply and the relay switch 51 are connected in series.
1 is cut off, the relay switch 51 operates,
When the power supply to the excitation circuit 27 is cut off, the power supply to the excitation coil 18 is cut off. The thermoswitch 50 set the OFF operation temperature to 220 ° C.

The thermoswitch 50 is connected to the fixing belt 1.
The fixing switch 10 is disposed in a non-contact manner on the outer surface of the fixing belt 10 so as to face the heat generating region H of 0, and the distance between the thermoswitch 50 and the fixing belt 10 is approximately 1 mm. Thereby, the fixing belt 10
Therefore, it is possible to prevent the fixed image from being damaged due to the durability.

According to this embodiment, the heat generation area H of the fixing belt 10
Is positioned above the entry side of the recording material P in the fixing nip portion N, unlike a configuration in which heat is generated in the fixing nip N as in the conventional device shown in FIG. Even when the fixing device stops with the paper sandwiched in the nip N, the power supply to the exciting coil 18 is continued, and the fixing belt 10 continues to generate heat, no heat is generated in the fixing nip portion N where the paper is sandwiched. The paper is not directly heated. In addition, since the thermo switch 50 is provided in the heat generation region H where the heat generation amount is large, the thermo switch 50
When 0 ° C. is sensed and the thermo switch is turned off, the power supply to the exciting coil 18 is cut off by the relay switch 51.

According to this example, the ignition temperature of the paper is about 400 ° C.
Because it is near, the paper does not ignite and the fixing belt 1
Zero heat generation can be stopped. A temperature fuse may be used as the temperature detection element in addition to the thermoswitch.

In the present embodiment, the toner containing a low softening substance is used in the toner t. Therefore, the fixing device does not have an oil application mechanism for preventing offset, but the toner does not contain the low softening substance. In this case, an oil application mechanism may be provided, and oil application or cooling / separation may be performed even when a toner containing a low softening substance is used. A) Excitation Coil 18 The excitation coil 18 uses a bundle (bundle) of a plurality of copper thin wires, each of which is individually insulated and coated, as a conductive wire (electric wire) constituting a coil (wire transfer). The exciting coil is formed by winding a plurality of times. In this example, the exciting coil 18 is formed by winding 10 turns.

As the insulating coating, a coating having heat resistance is preferably used in consideration of heat conduction due to heat generated by the fixing belt 10.
For example, a coating of polyamideimide or polyimide may be used. The excitation coil 18 may improve the density by applying pressure from the outside.

The shape of the exciting coil 18 is set along the curved surface of the heating layer 1 as shown in FIG. In this embodiment, the distance between the heat generating layer of the fixing belt 10 and the exciting coil 18 is set to be approximately 2 mm. As the material of the excitation coil holding member 19, a material having excellent insulation properties and good heat resistance is preferable. For example, phenol resin, fluorine resin, polyimide resin, polyamide resin, polyamide imide resin, P
EEK resin, PES resin, PPS resin, PFA resin, P
It is preferable to select TFE resin, FEP resin, LCP resin, or the like.

Magnetic cores 17a and 17b and exciting coil 1
8 and the heat generating layer 1 of the fixing belt 10 are closer to each other as much as possible, the magnetic flux absorption efficiency is higher. However, when this distance exceeds 5 mm, the efficiency is remarkably reduced. Is good. If the distance is within 5 mm, the distance between the heating layer 1 of the fixing belt 10 and the exciting coil 18 does not need to be constant.

Excitation coil holding member 19 of excitation coil 18
4, that is, 18 a and 18 b (FIG. 4), the outside of the bundled wire is insulated for portions outside the excitation coil holding member 19. B) Fixing Belt 10 FIG. 7 is a schematic diagram of a layer configuration of the fixing belt 10 in this example. The fixing belt 10 of the present embodiment has a heating layer 1 made of a metal belt or the like which is a base layer of the fixing belt 10 of electromagnetic induction heat generation.
And an elastic layer 2 laminated on its outer surface and a release layer 3 laminated on its outer surface. A primer layer (not shown) may be provided between each layer for adhesion between the heat generating layer 1 and the elastic layer 2 and adhesion between the elastic layer 2 and the release layer 3.
In the fixing belt 10 having a substantially cylindrical shape, the heat generating layer 1 is on the inner surface side, and the release layer 3 is on the outer surface side. As described above, the alternating magnetic flux acts on the heat generating layer 1 so that the heat generating layer 1
Then, an eddy current is generated and the heat generating layer generates heat. The heat heats the fixing belt 10 via the elastic layer 2 and the release layer 3, and the recording material P as the heating material passed through the fixing nip N
Is heated to heat and fix the toner image.

A. Heating Layer 1 The heating layer 1 is preferably made of a ferromagnetic metal such as nickel, iron, ferromagnetic SUS, and nickel-cobalt alloy. A non-magnetic metal may be used, but a metal such as nickel, iron, magnetic stainless steel, or a cobalt-nickel alloy, which has good magnetic flux absorption, is more preferable.

It is preferable that the thickness is larger than the skin depth represented by the following formula and 200 μm or less. The skin depth σ [m] is determined by the frequency f [Hz] of the excitation circuit and the magnetic permeability μ.
Is expressed as σ = 503 × (ρ / fμ) ^1/2 with the specific resistance ρ [Ωm].

This indicates the depth of absorption of electromagnetic waves used in electromagnetic induction. At a depth deeper than this, the intensity of the electromagnetic waves is 1 / e or less. (FIG. 9).

The thickness of the heat generating layer 1 is preferably 1 to 100 μm.
m is good. If the thickness of the heat generating layer 1 is smaller than 1 μm, most of the electromagnetic energy cannot be absorbed, so that the efficiency is deteriorated. On the other hand, if the heating layer 1 has a thickness of more than 100 μm, the rigidity becomes too high, and the flexibility deteriorates, which is not practical for use as a rotating body. Therefore, the thickness of the heating layer 1 is 1 to
100 μm is preferred.

B. Elastic Layer 2 The elastic layer 2 is made of silicone rubber, fluorine rubber, fluorosilicone rubber, or the like, and has good heat resistance and good thermal conductivity. The thickness of the elastic layer 2 is preferably from 10 to 500 μm.
The elastic layer 2 has a thickness necessary to ensure the crystal quality of the fixed image.

When a color image is printed, a solid image is formed over a large area on the recording material P, especially for a photographic image. In this case, if the heating surface (the release layer 3) cannot follow the unevenness of the recording material or the unevenness of the toner layer, uneven heating occurs, and uneven gloss occurs in the image in portions where the amount of heat transfer is large and small. Areas with a large amount of heat transfer have high gloss,
The glossiness is low in portions where the amount of heat transfer is small.

When the thickness of the elastic layer 2 is 10 μm or less, the unevenness of the recording material or the toner layer cannot be completely followed, and uneven image gloss occurs. Also, if the elastic layer 2 is 1000
If it is more than μm, the thermal resistance of the elastic layer becomes large, and it is difficult to realize quick start. More preferably, the thickness of the elastic layer 2 is preferably 50 to 500 μm.

If the hardness of the elastic layer 2 is too high, the elasticity of the elastic layer 2 cannot follow irregularities of the recording material or the toner layer, resulting in uneven image gloss. Therefore, the hardness of the elastic layer 2 is 60 ° (JIS-A) or less, more preferably 45 ° (J-A).
IS-A) The following is preferred.

The thermal conductivity λ of the elastic layer 2 is 2.5 × 10 ^{−3 to} 8.4 × 10 ⁻³ [W / cm · °
C] (6 × 10 ^-4 to 2 × 10 ^-3 [ca1 / cm · sec]
Deg]) is good.

The thermal conductivity λ is 2.5 × 10 ⁻³ [W / cm · ° C.] (6 × 10 ⁻⁴ [c
a1 / cm · sec · deg]), the thermal resistance is large, and the temperature rise in the surface layer (release layer 3) of the fixing belt becomes slow.

When the thermal conductivity λ is 8.4 × 10 ⁻³ [W / cm · ° C.] (2 × 10 ⁻³ [c
a1 / cm · sec · deg]), the hardness becomes too high or the compression set becomes worse.

Therefore, the thermal conductivity λ is 2.5 × 10 ⁻³ [W / cm · ° C.] (6 × 10 ⁻⁴ [c
a1 / cm · sec · deg]) ~ 8.4 × 10
^-3 [W / cm · ° C] (2 × 10 ^-3 [ca1 / cm ·
sec · deg]).

More preferably, 3.3 × 10 ⁻³ [W / cm · ° C.] (8 × 10 ⁻⁴ [c
a1 / cm · sec · deg]) ~ 6.3 × 10
⁻³ [W / cm · ° C.] (1.5 × 10 ⁻³ [ca1 / c]
m · sec · deg]).

C. Release Layer 3 Release layer 3 is made of fluororesin, silicone resin, fluorosilicone rubber, fluororubber, silicone rubber, PFA, P
A material having good releasability and heat resistance, such as TFE and FEP, can be selected.

The thickness of the release layer 3 is preferably 1 to 100 μm. If the thickness of the release layer 3 is less than 1 μm, there arises a problem that uneven coating of the coating film causes a part having poor releasability or insufficient durability. On the other hand, if the thickness of the release layer exceeds 100 μm, there is a problem that heat conduction is deteriorated. In particular, in the case of a resin-based release layer, the hardness becomes too high, and the effect of the elastic layer 2 is lost.

As shown in FIG. 8, in the configuration of the fixing belt 10, the heating layer 1 on the side of the belt guide surface (the heating layer 1
The heat insulating layer 4 may be provided on the side opposite to the elastic layer 2).
As the heat insulating layer 4, a fluororesin, a polyimide resin, a polyamide resin, a polyamideimide resin, a PEEK resin, P
ES resin, PPS resin, PFA resin, PTFE resin, F
A heat-resistant resin such as an EP resin is preferable.

The thickness of the heat insulating layer 4 is 10 to 10
00 μm is preferred. When the thickness of the heat insulating layer 4 is smaller than 10 μm, the heat insulating effect cannot be obtained, and the durability is insufficient. On the other hand, if it exceeds 1000 μm, the magnetic core 17
The distance of the heat generating layer 1 from the a.17b and the exciting coil 18 increases, and the magnetic flux is not sufficiently absorbed by the heat generating layer 1.

Since the heat insulating layer 4 can insulate the heat generated in the heat generating layer 1 so as not to go to the inside of the fixing belt, the efficiency of heat supply to the recording material P side is lower than when the heat insulating layer 4 is not provided. Get better. Therefore, power consumption can be suppressed. C) Rotational speed detection As shown in FIG. 1, a rotation that absorbs light of a specific wavelength in a region where the recording material P at the end of the fixing belt 10 as a means for directly transmitting the rotation of the heating rotator does not pass. The detection pattern 60 is formed. For example, width 2 mm, length 10
Twenty mm belt-shaped patterns are formed on the surface of the fixing belt at equal intervals. The distance between the patterns was 2 mm. As shown in FIG. 2, an optical sensor 61 including a light emitting element and a reflected light receiving element is disposed at a position facing the rotation detection pattern 60.

The optical sensor 61 is composed of a light emitting element and a light receiving element. Light emitted from the light emitting element is reflected at the position of the rotation detection pattern 60 on the fixing belt 10 and detected by the light receiving element. The light amount obtained by the light receiving element is converted into an electric signal,
The converted electric signal is taken into a control circuit (not shown), and a change in the electric signal can be monitored.

In this embodiment, the electric signal is obtained by converting the amount of light obtained by the light receiving element into a voltage value. Hereinafter, the converted voltage value is referred to as a detected voltage value. Optical sensor 61
The light emitted from the light emitting element of the rotation detection pattern 60
When the light is absorbed by the light receiving element, the amount of light detected by the light receiving element decreases, and the detection voltage value also decreases.

Therefore, when the fixing belt 10 rotates as shown in FIG.
It changes according to the position of. Here, the distance between the peaks of the voltage value is 1
Think of it as a cycle. Since the rotation detection pattern is a pattern that absorbs light as described above, the detection voltage value becomes minimum when the rotation detection pattern 60 is located at the center position of the optical sensor 61, and the rotation detection pattern is rotated at the center position of the optical sensor 61. It becomes the maximum value when the middle of the detection pattern 60 is located.

In this embodiment, the fixing belt 10 is determined based on the period of the electric signal of the rotation detection pattern 60 detected by the optical sensor 61.
, That is, the transport speed of the recording material P is calculated. Monitor the time of one cycle between the peaks of the detected voltage value,
A feed hack is applied to the rotation speed of the driving means M according to the amount of change in the time.

As an example, hereinafter, the fixing belt 10 is
Description will be made assuming a case where one rotation is made during c. As described in the first embodiment, there are 20 rotation detection patterns for one rotation of the fixing belt 10. Therefore, FIG.
As shown in (1), when the fixing belt 10 is rotated once per 1 second, a voltage fluctuation signal of 50 msec per cycle is obtained.

When the rotation speed of the fixing belt is set as described above while the temperature of the pressure roller 30 is at room temperature, the pressure is increased until the first recording material reaches the fixing nip after the heating operation is started. Due to the thermal expansion of the roller, the outer peripheral length of the pressure roller becomes longer. Further, when continuous printing or intermittent printing is performed, the temperature of the pressure roller further increases, and the outer peripheral length of the pressure roller further increases. The amount of thermal expansion of the pressure roller depends on the outer diameter of the pressure roller, the thickness of the elastic layer, the method of setting the coefficient of thermal expansion, etc., and the temperature of the pressure roller, but when the rotational angular velocity of the pressure roller shaft is constant, The pressure roller surface speed will increase by a few percent with increasing temperature.

For example, when the surface speed of the 5% pressure roller increases, the conveying speed of the recording material also increases by approximately 5%, and one cycle of rotation detection of the fixing belt is 50 msec × (100−5)% = 47.5 msec. And the transport speed of the recording material increases.

Assuming that the transport speed of the fixing nip N is Vf and the transport speed of the transfer nip T2 is Vt, Vf ≒ Vt at room temperature.
When the electromagnetic induction heating is started and the diameter of the pressure roller expands, Vf> Vt, and when the recording material enters the fixing nip, the recording material is pulled between the fixing nip and the transfer nip.

Therefore, in this embodiment, feedback is applied to the rotation speed of the driving means M of the pressure roller so that one cycle of rotation detection of the fixing belt can be maintained at a constant value in about 50 msec. Feedback control is a general PLL
(Phased locked loop) control, PID (proportional-integral-derivative) control, or the like may be used. In order to realize the feedback control, it is preferable to use a circuit including an operational amplifier or a DSP (Digital Signal Processing). The control constant can be set according to the rotation speed and the amount of thermal expansion of the pressure roller. By this feedback control, one cycle of rotation detection is set to a set value (50 msec in this example).
c) If it is shorter, the rotation speed of the driving means M is reduced, and if one cycle of rotation detection is longer than the set value, the driving means M
Control to increase the rotation speed of the. With this control, the rotation speed of the fixing belt can be kept substantially constant. Therefore, the recording material can be transported at a stable speed.

In this embodiment, the transport speed of the fixing nip N at room temperature and the transport speed of the transfer nip T2 are set to be substantially equal as an initial setting. However, this initial setting value is set for an arbitrary pressure roller temperature. Has the same effect. Further, it is preferable that Vf <Vt be set within a range that does not affect the conveyance of the recording material and the image. This is effective to ensure that the recording material is not pulled between the fixing nip N and the transfer nip T2.

According to the present invention, in a heating device driven by a pressure roller, an electromagnetic induction heating type heating device capable of realizing a quick start from room temperature by using a fixing belt having a small heat capacity. Monitor and
The change in the transport speed can be corrected by feeding back the change in the transport speed due to the thermal expansion of the pressure roller to the rotation speed of the driving unit M. Accordingly, the recording material can be stably conveyed, and the distance between the fixing nip N and the transfer nip T2 can be shortened, so that the size of the image forming apparatus main body can be reduced. Furthermore, the first blind time can be reduced.

In a color image forming apparatus in which a color image is collectively transferred to a recording material using an intermediate transfer member as in this embodiment, or in a monochrome image forming apparatus (not shown), a fixing nip N portion The conveyance speed of the recording material in the recording nip can be kept substantially constant, so that the conveyance speed of the fixing nip is almost equal to or slightly lower than the conveyance speed of the transfer nip, so that the recording material enters the fixing nip. However, since the recording material is not pulled, no image elongation occurs.

Further, even in a color image forming apparatus, even when a plurality of photoconductors are arranged in tandem on a conveyor belt and a toner image is sequentially transferred to a recording material, image elongation does not occur. Even when the recording material enters the fixing nip in a state where the recording material straddles a plurality of transfer nips, the conveyance speed of the recording material at the fixing nip N portion can be kept substantially constant. By lowering the transport speed at the fixing nip, which is almost equal to or slightly lower than the transport speed, even if the recording material enters the fixing nip, the recording material will not be pulled, and good image quality without color shift will occur. Can be obtained.

In a tandem type color image forming apparatus, it is necessary to arrange a plurality of photosensitive drums substantially in a line, and if the distance between the final transfer nip and the fixing is large enough to absorb the change in the conveying speed, the apparatus becomes large. Although there is a problem that the heating device is driven, the size of the main body can be reduced by implementing the present invention even in a heating device driven by a pressure roller.

Further, when the recording material is conveyed substantially vertically even in the tandem type, the relationship between the rear end of the conveyance belt and the fixing nip N is determined on the image surface side of the recording material in consideration of the minimum paper passing length. since disturbed images holding the recording material, and the distance between the conveyor belt rear fixing nip and L _TF, the minimum sheet passing length as L _SP, must satisfy the L _TF <L _SP is there. By implementing the present invention in a heating device driven by a pressure roller, the distance between the rear end of the conveyance belt and the fixing nip N can be reduced in a tandem type image forming apparatus that conveys a recording material substantially vertically, This is particularly effective for making it possible to convey a recording material having a small size.

In this embodiment, the rotation detecting pattern for absorbing light of a specific wavelength is formed, but a pattern having a higher reflectance than the fixing belt surface can be formed. In this case, the detected voltage value is higher at the center of the rotation detection pattern than at the middle position of the rotation detection pattern. The point is that a pattern may be formed so that the contrast of the detected voltage value can be obtained and the rotation state can be detected. Similarly, a slit may be formed in the fixing belt instead of the detection pattern.

As shown in FIG. 11, a rotation detecting pattern can be provided on the flange member 23b, which is an auxiliary member for protecting the end portion of the fixing belt 10, as a structure that can obtain the same effect. In this case, slits 62 can be radially provided as a rotation detection pattern as shown in FIG.
The light emitting element 63 and the transmitted light receiving element 64 can be disposed so as to face each other. In this case, it is not necessary to consider voltage value fluctuation due to contamination of the pattern surface, which needs to be considered in the case of the slit 62.

Further, the number of rotation detection patterns can be arbitrarily set according to the required detection accuracy, and the pattern width and pattern interval in the circumference of the fixing belt can be changed as necessary. (Second Embodiment) In this embodiment, the light emitting element 63 and the light receiving element 64, which are the optical sensors used in FIGS. 11 and 12 of the first embodiment, are used as a conveyance state detection sensor for the recording material P. An example will be described.

In the image forming apparatus, several sensors are provided on the conveyance path for monitoring the conveyance state of the recording material P. When the recording material P is in a state different from the normal conveyance state, that is, when the recording material P does not pass the sensor position at a predetermined timing, it is determined that a jam has occurred and the image forming process is stopped. And inform the user.

Therefore, in this example, FIGS.
As shown in FIG. 5, the passage information of the recording material P obtained from the paper ejection detection arm 65 provided after the fixing nip and the optical sensor used in the first embodiment are simultaneously monitored.

The mechanism by which the recording material P moves through the fixing nip N to move the paper ejection detection arm 65 will be briefly described. The paper ejection detection arm 65 is disposed at a position where the recording material P passes, and is fixed to a rotating shaft. The rotating shaft is rotatably fixed by positioning means (not shown). Further, a light-shielding plate 66 is fixed to the rotation shaft, and moves in conjunction with the sheet ejection detection arm 65.

The light shielding plate 66 is movably installed between the light emitting element 63 and the light receiving element 64 of the optical detection sensor.
FIG. 14 shows a state before the recording material P pushes the discharge detection arm 65 (discharge sensor off). FIG. 15 shows a state in which the recording material pushes the sheet ejection detection arm 65 (sheet ejection sensor on).
Then, the movement of the arm moves the light shielding plate 66 in the direction of the arrow via the rotation shaft. When the recording material P has passed and the discharge detection arm 65 returns to the original position, the light shielding plate 66 also returns to the original position (FIG. 14) in conjunction with this. The movement destination of the light shielding plate 66 is set so as to shield a part of the slit 62 for rotation detection.
Arranged so as to provide percent shielding.

The detection voltage obtained as shown in FIG. 16 depends on whether the recording material P is at the position of the discharge detection arm 65 (discharge sensor on) or not (discharge sensor off). The value changes. In the present example, the voltage level is also reduced by about 50% (voltage drop) by shading about 50%. By monitoring the change in the peak voltage value, the conveyance state of the recording material can be monitored. The transport state can be determined based on the amount of decrease from the peak voltage value, the rate of decrease from the peak voltage value, when the value falls below a set threshold value, and the like.

As described above, in this embodiment, in addition to the rotation detection of the fixing belt 10 described in the first embodiment, the conveyance state of the recording material P can be monitored by the same optical detection element. became. Therefore, it is possible to provide an image forming apparatus capable of detecting the rotation of the fixing belt 10 at low cost. (Third Embodiment) In this embodiment, the rotation state of the fixing belt is monitored from the rotation speed of the fixing belt 10 detected in the first and second embodiments, and the following control is performed. As shown in FIG. 17, when the fixing belt is not rotating (when stopped),
It shows a constant voltage value according to the position where the fixing belt stops. Therefore, by monitoring this voltage value, the rotation of the fixing belt 10 can be detected. If the pressure roller 30 is rotated, the fixing belt 10
When the rotation of the fixing belt 10 is not detected, that is, when the voltage value indicates a constant value, it is determined that the fixing belt 10 is not rotating, and the electromagnetic induction heating is stopped.
The image forming operation is stopped.

Further, as shown in FIG. 17, when the voltage value is detected at a period longer than the period when the voltage value is rotating at a normal speed (normal state) for one period time (during slip), When it is determined that the fixing belt 10 is slipping, the electromagnetic induction heating is stopped, and the image forming operation is stopped. Here, the normal speed means that the period of one cycle is longer than the set value although the pressure roller is rotated faster than the maximum value at which the rotational angular speed of the pressure roller 30 changes due to thermal expansion. Means the case.

Here, for example, an operation failure state of the fixing belt 10 can be displayed on an operation panel (not shown) of the image forming apparatus or a connected image input apparatus (computer or the like).

FIG. 17 illustrates an example using the optical sensor 61 shown in FIG. 2, but the same control can be performed in the case of the optical sensor shown in FIGS.

According to the present invention, the heating operation can be safely stopped when the fixing belt does not rotate despite the rotation of the pressure roller or when the fixing belt slips. In particular, it is possible to prevent the fixing belt 10 from being damaged even when the heat generation region is outside the nip and the temperature rising speed is high. (Others) 1) A means for directly transmitting rotation from the fixing belt 10 may be provided, and the optical sensor 61 may be provided for this means. Specifically, the flange member 23 is used as a means for directly transmitting rotation.
Can be formed in a gear shape, and a rotation detection pattern can be formed on another gear to which rotation has been directly transmitted as this means.

2) An encoder can be used for the rotation detection pattern and the optical sensor.

3) The fixing belt 10 of heat generation by electromagnetic induction is
In the case of heat fixing such as a monochrome or one-pass multicolor image, the elastic layer 2 may be omitted. The heat generating layer 1 may be formed by mixing a metal filler into a resin. The heating layer may be a single layer member.

4) In order to supply thermal energy to the recording material also from the pressing member 30 side, a heating means such as electromagnetic induction heating is also provided on the pressing member 30 side to heat and control the temperature to a predetermined temperature. It is also possible to adopt a device configuration.

5) The fixing belt 10 can be made of another type of member such as a rigid roller.

6) 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 holding an image to improve the surface properties such as gloss, and an image heating device to be assumed. It can be widely used as a means / apparatus for heat-treating a material to be heated, such as a device for heating and drying a material to be heated, a heating laminating device, and the like. Fourth Embodiment Example of Image Forming Apparatus FIG. 18 is a schematic configuration diagram showing an example of an image forming apparatus according to the present invention in which the heating device shown in each of the above embodiments is applied as a heat fixing device. The image forming apparatus of this example is an electrophotographic color printer. FIG.
In the figure, reference numeral 101 denotes a photosensitive drum (image carrier) made of an organic photosensitive member or an amorphous silicon photosensitive member, and is rotated at a predetermined process speed (peripheral speed) in a counterclockwise direction indicated by an arrow. The photosensitive drum 101 undergoes a uniform charging process of a predetermined polarity and potential by a charging device 102 such as a charging roller during the rotation process.

Next, a laser beam 103 output from a laser optical register (laser scanner) 110 is applied to the charged surface.
And scanning exposure processing of the target image information. The laser optics 110 is a laser beam 10 modulated (on / off) corresponding to a time-series electric digital pixel signal of target image information from an image signal generator such as an image reader (not shown).
3 is output to form an electrostatic latent image corresponding to the target image information scanned and exposed on the surface of the rotating photosensitive drum 101. 109
Is a mirror for deflecting the output laser light from the laser optical box 110 to the exposure position of the photosensitive drum 101.

In the case of full-color image formation, scanning exposure / latent image formation is performed on a first color-separated component image in a target full-color image, for example, a yellow component image.
The latent image is developed as a yellow toner image by the operation of the yellow developing device 104Y of the four-color developing device 104. The yellow toner image is the photosensitive drum 101
(Or close part) between the roller and the intermediate transfer drum 105
In the primary transfer portion T1 which is
Is transferred to the surface. After the transfer of the toner image to the surface of the intermediate transfer drum 105, the surface of the rotary photoconductor drum 101 is cleaned by the cleaner 107 after removing the adhered residue such as untransferred toner.

The process cycle of charging, scanning exposure, development, primary transfer, and cleaning as described above is performed by the second color separation component image (for example, magenta component image,
The magenta developing device 104M operates), the third color separation component image (eg, cyan component image, cyan developing device 104C operates), the fourth color component button component image (eg, black component image, black developing device 104BK operates) ) Are sequentially executed for each color separation component image, and a yellow toner image is formed on the surface of the intermediate transfer drum 105. Convenient four color toner images of a magenta toner image, a cyan toner image, and a black toner image are sequentially superimposed and transferred, and a color toner image corresponding to a target full-color image is synthesized and formed.

The intermediate transfer drum 105 is a metal drum 1
05a on the medium resistance elastic layer 105b and the high resistance surface layer 10
5c is rotated clockwise as indicated by an arrow at substantially the same peripheral speed as the photosensitive drum 101 in contact with or in proximity to the photosensitive drum 101, and a bias potential is applied to the metal drum 105a of the intermediate transfer drum 105. And the toner image on the photosensitive drum 101 is transferred to the surface of the intermediate transfer drum 105 by the potential difference from the photosensitive drum 101.

The color toner image synthesized and formed on the surface of the intermediate transfer drum 105 is
In a secondary transfer portion T2 which is a contact nip portion between the transfer roller 05 and the transfer roller 106, the toner image is transferred onto the surface of the recording material P sent to the secondary transfer portion T2 from a paper supply unit (not shown) at a predetermined timing. Go. The transfer roller 106 is supplied with a charge having a polarity opposite to that of the toner from the back surface of the recording material P,
The combined color toner images are sequentially and collectively transferred from the surface of the intermediate transfer drum 105 to the recording material P.

The recording material P that has passed through the secondary transfer portion T2 is separated from the surface of the intermediate transfer drum 105, introduced into the image heating device (fixing device) 100, and subjected to the heat fixing process of the unfixed toner image. The sheet is discharged to a discharge tray (not shown) outside the apparatus as a color image formed product. After the transfer of the color toner image to the recording material P, the intermediate transfer drum 105 is cleaned by the cleaner 108 by removing the residual toner such as untransferred toner and paper dust. The cleaner 108 is normally kept in a non-contact state with the intermediate transfer drum 105. In the process of performing the secondary transfer of the color toner image from the intermediate transfer drum 105 to the recording material P, the cleaner 108 contacts the intermediate transfer drum 105. It is kept in contact.

The transfer roller 106 is also always kept in a non-contact state with the intermediate transfer drum 105, and during the secondary transfer of the color toner image from the intermediate transfer drum 105 to the recording material P, the intermediate transfer is performed. Body drum 10
5 is held in contact with the recording material P via the recording material P.

The apparatus of the present embodiment can also execute a print mode of a monocolor image such as a monochrome image. Also, a double-sided image print mode or a multiple image print mode can be executed.

In the case of the double-sided image print mode, the recording material P on which the first-side image printed out of the image heating device 100 has been printed.
Is turned upside down via a recirculation transport mechanism (not shown), is sent again to the secondary transfer portion T2, receives the toner image transfer on the two surfaces, and is again introduced into the image heating device 100 and
By receiving the fixing process of the toner image on the surface, a double-sided image print is output.

In the case of the multiple image print mode, the recording material P on which the first image has been printed out of the image heating device 100 is printed.
Is sent to the secondary transfer unit T2 again without being turned upside down via a recirculation transport mechanism (not shown) and receives the second transfer of the toner image on the surface on which the first image has been printed. , And undergoes the second toner image fixing process, thereby outputting a multiplex image print.

[0120]

As described above, according to the present invention,
In the heating device driven by the pressure roller, a heating device of the electromagnetic induction heating type that can realize a quick start from room temperature using a fixing belt with a small heat capacity, monitors the rotation detection cycle of the fixing belt, and The change in the transport speed can be corrected by feeding back the change in the transport speed due to the expansion to the rotation speed of the drive unit. Therefore, the recording material can be stably conveyed, and the distance between the fixing nip and the transfer nip can be reduced. As a result, the size of the image forming apparatus body to which the heating device of the present invention is applied as the heat fixing device can be reduced. Becomes possible. Further, the first print time can be reduced.

Further, since the conveying speed of the recording material at the fixing nip N portion can be kept substantially constant, the conveying speed of the fixing nip portion is made substantially equal to or slightly lower than the conveying speed of the transfer nip. Even if the recording material enters the fixing nip, the recording material is not pulled, so that image elongation does not occur.

Further, even when a plurality of photoconductors are arranged in tandem on a transport belt in a color image forming apparatus, and the toner images are sequentially transferred to a recording material, image expansion does not occur. Even when the recording material enters the fixing nip with the recording material straddling a plurality of transfer nips, the conveyance speed of the recording material at the fixing nip N portion can be kept substantially constant. The transport speed at the fixing nip is almost equal to or slightly lower than the transport speed of the fixing nip, so that the recording material does not pull even when the recording material enters the fixing nip, and a good image without color shift occurs. Quality can be obtained.

Further, since the heat generation area of the fixing belt is positioned above the entrance side of the recording material in the fixing nip portion, when the fixing device goes out of control due to a device failure, the fixing device stops with paper being pinched in the fixing nip. Even when power is supplied to the exciting coil and the fixing belt 10 continues to generate heat, the paper is not directly heated because no heat is generated in the fixing nip portion where the paper is sandwiched.

Further, when the recording material is conveyed substantially vertically even in the tandem type image forming apparatus, the distance between the rear end of the conveying belt and the fixing nip N can be reduced without disturbing the image, and the recording material having a smaller size can be formed. The recording material can be transported.

In addition to the detection of the rotation of the fixing belt, the conveyance state of the recording material can be monitored by the same optical sensor. Therefore, it is possible to provide an image forming apparatus capable of detecting the rotation of the fixing belt at low cost.

Further, there is an effect that the heating operation can be safely stopped when the fixing belt does not rotate despite the rotation of the pressure roller or when the fixing belt slips.

The image forming apparatus further includes an image forming means for forming an image on a recording material, and the above-described heating device of the present invention. Since the image forming apparatus is configured as an image heating apparatus for performing heat fixing processing on a material, there is an effect that an image forming apparatus capable of forming a high quality image can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic front view of a main part showing a first embodiment of a heating device of the present invention.

FIG. 2 is a schematic cross-sectional side view of a main part of the heating device.

FIG. 3 is a schematic cross-sectional front view of a main part of the heating device.

FIG. 4 is a diagram showing a relationship between a magnetic field generating means and an excitation circuit.

FIG. 5 is a diagram showing a relationship between a magnetic field generating means and a heat generation amount Q.

FIG. 6 is a diagram showing how an exciting coil is wound.

FIG. 7 is a schematic diagram of a layer configuration of a fixing belt having an electromagnetic induction heating property.

FIG. 8 is a schematic diagram of a layer configuration of a fixing belt having an electromagnetic induction heating property.

FIG. 9 is a graph showing the relationship between the depth of a heating layer and the intensity of electromagnetic waves.

FIG. 10 is a graph showing a time change of a detection voltage value.

FIG. 11 is a front model view of a main part of a heating device of another embodiment.

FIG. 12 is a schematic cross-sectional side view of a main part of a heating device according to another embodiment.

FIG. 13 is a front model view of a main part of a heating device according to a second embodiment.

FIG. 14 is a schematic cross-sectional side view of the main part of the paper ejection sensor off.

FIG. 15 is a schematic cross-sectional side view of the main part of the paper ejection sensor on.

FIG. 16 is a graph showing a relationship between a detected voltage value and time in the second embodiment.

FIG. 17 is a graph illustrating a change over time in a detected voltage value according to the third embodiment.

FIG. 18 is a schematic configuration diagram of an image forming apparatus in which the heating device of the present invention is applied as a heat fixing device.

FIG. 19 is a cross-sectional side view of a conventional fixing device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Heat generation layer 2 Elastic layer 3 Release layer 4 Heat insulation layer 10 Fixing belt 16 Belt guide 17a, 17b Magnetic core 18 Exciting coil 19 Exciting coil holding member 23a / 23b Flange member for regulating and holding end of fixing belt 26 Temperature detecting element (Thermistor) 27 Excitation circuit 30 Pressure roller as pressure rotating body 60 Rotation detection pattern 61 Optical sensor 62 Slit 63 Light emitting element 64 Light receiving element 65 Paper ejection detection arm 66 Light shielding plate

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 2H033 BA11 BA12 BA25 BA31 BA32 BE06 CA13 3K059 AA08 AB19 AB27 AB28 AC47 AD08 AD29 AD30 AD32 AD34 BD23 CD10 CD75

Claims (13)

[Claims] 1. A heating rotator for generating electromagnetic induction by the action of a magnetic field of a magnetic field generating means, a driving rotator having an elastic layer for driving the heating rotator by frictional force, and detecting rotation of the heating rotator. A heating device comprising: a rotation detection unit; a rotation speed is detected by using the rotation detection unit, and the rotation speed of the driving rotator is controlled based on the detected rotation speed. 2. The heating device according to claim 1, wherein the driving rotator is a pressurizing rotator that forms a nip portion by mutual pressure contact with the heat generating rotator. 3. The heating device according to claim 1, wherein a rotation detection pattern is formed on the surface of the heating rotator. 4. The heating device according to claim 1, wherein a rotation detection pattern is formed on an auxiliary member that rotates together with the heating rotator. 5. The heating apparatus according to claim 1, further comprising means for directly transmitting the rotation of the heating rotator, wherein the rotation detection pattern is formed on the means. 6. The heating apparatus according to claim 3, wherein a rotation speed is detected from the heat generation rotation detection pattern by using the rotation detection means. 7. The heating device according to claim 1, wherein the heating rotator is an endless belt. 8. The heating apparatus according to claim 7, wherein the heat generating area of the endless belt is located above the entrance side of the recording material in the nip portion. 9. The heating apparatus according to claim 1, wherein said rotation detecting means can simultaneously detect a conveyance state of the recording material. 10. When the rotation of the heating rotator is not detected even though the driving rotator is rotating, stopping the heat generation of the heating rotator and stopping the rotation of the driving rotator. Claims 1 to 9 characterized by the above-mentioned.
The heating device according to claim 1. 11. An image forming means for forming an image on a recording material, and a heating device according to any one of claims 1 to 10, wherein said heating device is covered by said image forming means. An image forming apparatus comprising: an image heating device that heats an image formed on a recording material. 12. An image forming apparatus for forming an image on a recording material, comprising: a plurality of image forming means for forming an image on the recording material; and a nip portion for simultaneously nipping and conveying the recording material. The image forming apparatus according to claim 11, wherein: 13. An image forming apparatus according to claim 11, wherein said recording material is conveyed substantially vertically.