JP2003151722A - Heating device and heating system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve temperature followingness during passing of a small size paper in a fixing device. SOLUTION: Inside a cylindrical fixing roller 300, a main heater 3010 of double end type and sub heaters 3011, 3012 of single end type are arranged. The main heater 3010 and the sub heaters 3011, 3012 are arranged such that the main heater 3010 heats a small size (B5 of standard size) paper passing zone, and that the sub heaters 3011, 3012 heat an outside zone from their both edge portions. When the small size paper is heated, the main heater 3010 is used. When the paper of the size larger than that is heated, the main heater 3010 and the subs heaters 3011, 3012 are used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device in a dry electrophotographic device, a drying device in a wet electrophotographic device, a drying device in an ink jet printer, a heating device preferably implemented in an erasing device for rewritable media, and heating. Regarding the system.

[0002]

2. Description of the Related Art As a fixing device which is one of typical heating devices used in electrophotographic equipment such as copying machines and printers, a halogen heater is generally provided inside a fixing roller made of a hollow core metal such as aluminum. There is often used a configuration in which a heating means including the above is disposed and a halogen heater is caused to generate heat to set the fixing roller to a predetermined temperature (fixing temperature).

However, in this method, the time required for the fixing roller to reach the fixing temperature after the start of heating, that is, the so-called warm-up time is long, and it is necessary to preheat the fixing roller during standby from the viewpoint of usability. Therefore, there is a problem that the standby power consumption is large. So, in recent years,
Attempts have been made to reduce the warm-up time by thinning the fixing roller to reduce the heat capacity. However, in this case, the heat transfer property of the fixing roller in the axial direction is lowered, and when a small-sized recording paper is continuously passed, the surface temperature of the fixing roller at a portion where the recording paper does not pass is abnormally increased. There is a problem that abnormal temperature rise of the paper passing portion is likely to occur.

As a solution to such a problem, as disclosed in Japanese Patent Laid-Open No. 8-220930, a plurality of (mainly two) heaters having different heating areas are used to make the size of the recording paper. Therefore, a measure for selectively heating the fixing roller has been taken.

There are the following two main methods.

First, as a first method, as shown in FIG. 16, a central heating heater 500 and a full width heating heater 50 are used.
In combination with 1 and 1, when the large size recording paper is passed, heating is performed only by the full width heating heater 501, and when passing small size paper, only the central heating heater 500 is used for heating. It was

However, in the first method, since the heat is not supplied to the end portion during continuous feeding of small size paper, the temperature of the end portion of the fixing roller is lower than that of the central portion. Therefore, if the large size paper is passed immediately after the small size paper is passed, fixing failure may occur at the end portion, wrinkles,
There is a problem that fixing and performance cannot be satisfied due to curling or the like.

As a second method, as shown in FIG. 17, a central heating heater (main heater) 500 and an end heating heater (sub-heater 502) are combined, and when a large size sheet is passed, the main heater is used. 500 and sub heater 50
2 is used for heating, and only the main heater 500 is used for heating when passing small size paper.

One temperature sensor 503 and one temperature sensor 504 are installed at the central portion and at the end portion, respectively. The central heater 503 controls the main heater 500 and the end sensor 504 controls the sub-heater 502. This second
In this method, the sub-heater 5
If the end temperature of the fixing roller is controlled to an appropriate temperature by 02, the fixing property is satisfied even when the large size sheet is passed immediately after the small size sheet is passed without the above-described temperature drop at the end portion. be able to.

[0010]

However, the second method also has the following problems.

1) Temperature follow-up property when passing small size paper An example of the axial output distribution (heat distribution characteristic) of the halogen heater in the second method is shown in FIG. The halogen heater has a structure in which electric energy is converted into thermal energy by energizing a tungsten filament inserted in the bulb. As shown in the figure, the output distribution of the halogen heater is, for example, a sub heater 502 for end heating. However, it is not possible to completely eliminate heat generation in the central portion (usually, it is inevitable to generate heat of about 20% of the heat generation amount at the end portion).
Similarly, in the main heater 500 for heating the central portion,
It is impossible to completely eliminate the heat generation at the end portions (as with the sub-heater, heat generation of about 20% of the heat generation amount at the center portion cannot be avoided). Therefore, in the second method, as shown in FIG. 18, the total heat generation amount obtained by summing the heat generation distribution of the main heater and the heat generation distribution of the sub heater is designed to be substantially flat. When continuously passing small size paper, the heat generation amount by the sub heater 502 is limited in order to avoid the temperature rise at both ends.

Therefore, when continuously passing small size paper, heat is supplied only by the main heater 500, and the heat supply amount to the paper passing portion is reduced. Therefore, when the second method is used at a fixing device having a high fixing speed, for example, a copying speed (or a printing speed) exceeding 40 sheets / minute, the halogen heater is used when continuously feeding small size paper. However, there is a problem in that the temperature of the fixing roller is lowered without being able to catch up with the heat supply.

2) Delay of warm-up due to heater heat capacity Even though the heat capacity of the fixing roller can be reduced, the heat capacity of the halogen heater is not much different from that of the configuration of FIG. This is because the heat capacity of the halogen heater depends on the length of the glass tube and the heater wire. For this reason, the heat capacity of the halogen heater is not sufficiently reduced, and there is a limit to the reduction of warm-up.

3) Roller axial direction temperature controllable With respect to both ends of the heating member, it is usual that the shape of the heating member is left and right and not symmetrical. The surrounding environmental conditions may also differ between the left and right depending on the usage conditions. Therefore, the amount of heat radiation from both ends of the heating member is not always constant on the left and right.

When the sub-heater is constituted by a double end type in which two electrodes for energization are arranged on both end surfaces of the heating member as in the conventional case, the amount of heat radiated from both end portions is always constant. There is a problem that a temperature difference occurs between the left and right of the heating member depending on the state.

4) Temperature drop of the roller end portion in the cooling mode When the heat capacity of the fixing roller is made low, depending on the degree thereof, the method of providing two halogen heaters, one for the main and one for the sub heater, may be used for passing small size paper. In some cases, it is not possible to sufficiently suppress the non-sheet passing temperature rise. For example, when the heat generation area of the main heater is set in accordance with B5R paper which is a kind of small size paper, for example, when A5R paper having a width narrower than B5R paper is continuously fed, the non-heating as shown in FIG. The temperature rises in the paper passing area. To deal with this problem, after passing a specific small size paper and then passing a larger size of recording paper, a cooling mode is set to wait for the execution of the next job for a predetermined time. A method of eliminating the temperature rise in the non-sheet-passing portion has been proposed (Japanese Patent Laid-Open No. 8-211779, etc.).

However, in this cooling mode, as shown in FIG. 20, the temperature at both ends of the fixing roller after cooling (after 15 seconds) becomes too lower than the fixing temperature,
Next, when the heating operation (fixing operation) is started, there is a problem that both ends of the medium become defective in heating (improper fixing). In order to suppress this edge temperature drop, for example, a method in which only the sub-heater 502 is turned on under a predetermined condition during the cooling mode can be considered, but as described above, the heat generation amount in the central portion of the sub-heater is set to 0.
Therefore, heat is also supplied to the non-sheet passing portion temperature rise occurrence region. For this reason, as shown in FIG. 21, the cooling time until the temperature of the non-sheet passing portion temperature rise occurrence region is lowered to an appropriate temperature is delayed to 20 seconds.

The present invention has been made to solve the above conventional problems. An object of the present invention is to improve the temperature followability when passing small size paper.

Another object of the present invention is to reduce warm-up time.

Another object of the present invention is to improve the temperature controllability in the roller axial direction.

Another object of the present invention is to suppress the temperature drop of the roller end portion in the cooling mode.

[0022]

The present invention has the following constitution to solve the above problems.

(1) It has a cylindrical heating member heated to a predetermined temperature by a heating means, and a pressurizing member press-contacting the heating member to form a press-contact portion, and the medium to be heated is applied to the press-contact portion. A heating device for transporting and heating a medium to be heated, wherein the heating means comprises a plurality of heaters having different heating regions corresponding to the width of the medium, and at least one of the plurality of heaters is provided. One heater is a single end type in which two electrodes for energization are arranged on the same end surface of the heating member.

With this structure, the following effects can be obtained.

By using the single end type heater, the length of the heater is shorter than the width of the medium to be heated. The shortened region becomes a non-heated region of the heater. Therefore, by the length of the unheated area,
The heat capacity of the heater can be reduced. This leads to a reduction in the heat capacity of the fixing device as a whole. As a result, the warm-up time can be shortened.

By using the single end type heater, the heat generation of the heater in the non-heated region can be reduced to zero. This area is heated by another heater. Since the power distribution to each heater is optimized by this, the heat supply efficiency can be improved when a small-sized medium is continuously fed, and a good heat following property can be secured.

(2) The plurality of heaters are a main heater for heating the sheet passing width region of a small-sized medium to be heated,
It consists of a sub-heater for heating the paper passing width area of the large-sized medium to be heated, excluding the paper passing width area of the small size, and the sub-heater is a single end type compared to the main heater. The sub-heater has a narrow heating area (a wide non-heating area), and by using the single-end type, the effect of reducing the warm-up and improving the heat supply efficiency at the time of passing a small-sized medium is high. vice versa,
When the main heater having a long heating area is a single end type, it is not preferable in terms of a supporting method (cantilever support) and a heater heat capacity.

.. (3) The heat capacity per unit length of the heating member is HCr, and the feeding speed of a small-sized medium to be heated is V
When p, Vp ≧ 38HCr + 39.

In the conventional heating device using a plurality of double end type heaters, as a result of examination, it is generally found that Vp ≧ 38.
Under the use condition of HCr + 39, the heat supply when a small-sized medium is continuously passed cannot catch up, the temperature of the heating member (fixing roller) is lowered, and heating failure (fixing failure) occurs until 100 sheets are continuously passed. Had occurred. Therefore, there is a problem that the heat capacity of the heating member cannot be reduced and the warm-up time becomes long (= the standby power consumption becomes large).

On the other hand, in the heating device according to the constitution of the present invention,
Since the heat supply can be secured even under the condition of Vp ≧ 38HCr + 39, the warm-up time can be shortened (= the standby power consumption can be reduced).

(4) The heat capacity per unit length of the heater is HCh, and the heat capacity per unit length of the heating member is HCh.
When r, HCr / HCh <14.

When HCr / HCh <14, a sufficient effect of 10% or more is obtained as the warm-up reduction rate.

(5) The main heater is of a double end type in which two electrodes for energization are arranged on both end surfaces of the heating member, and the heating area is a small size covering from the center to the left and right of the heating member. At least one sub-heater is arranged at each of both end portions of the heating member, the sub-heater being opposed to the sheet passing width region of the heating medium.

In the structure in which the paper is conveyed around the center, the main heater can heat the small size paper by arranging the fixing device as described above.
Large-sized paper can be heated by the main heater and the left and right sub-heaters.

(6) A temperature detecting element is provided on the heating member facing the main heater and the left and right sub-heaters at both ends of the heating member.

With such a configuration, the temperature of the main heater and the left and right sub-heaters can be controlled by a total of three temperature detecting elements.

(7) A temperature detecting element is provided on the heating member facing the main heater and one of the left and right sub-heaters at both ends of the heating member.

With such a structure, the temperature of the main heater and the left and right sub-heaters can be controlled by the total of two temperature detecting elements.

(8) The heater has a heating element such as a halogen heater and a nichrome wire heater, and a heat-resistant sealing material.

In the heater having the heating element and the heat-resistant sealing material, since the heater heat capacity other than the heating element is large,
The present invention can be applied more effectively.

(9) It is composed of the above-mentioned heating device and a control section for controlling the current to the heater, and the control section, when a medium to be heated of a size smaller than the heating area of the main heater is continuously fed. A cooling mode in which the main heater is turned off for a certain period of time is set, and in this cooling mode, control is performed to turn on only the sub-heater under predetermined conditions, and the heating member generated by continuously passing a small-sized medium to be heated is generated. It is characterized in that the temperature rise in the non-sheet passing portion is eliminated.

Conventionally, in a heating device having a cooling mode,
In the cooling mode, the temperatures of both ends of the heating member are too low compared to the central part of the heating member, and when the heating operation (fixing operation) is started next, there is a problem that both ends of the medium become defective in heating (improper fixing). In order to suppress this edge temperature drop, there is a method of turning on only the sub-heater under a predetermined condition during the cooling mode. However, in the conventional heating device having a plurality of double-end type heaters, the amount of heat generated at the center of the sub-heater is Since it is not 0, heat is also supplied to the non-sheet-passing portion temperature rise occurrence region, and the cooling time of the non-sheet-passing portion temperature rise occurrence region is delayed.

On the other hand, in the heating device according to the present invention, since the sub-heater is a single end type and heat is supplied only to both ends of the heating member, only the sub-heater is turned on under a predetermined condition during the cooling mode, so that no paper is passed. It is possible to prevent the temperature drop at both ends of the heating member without delaying the cooling time of the part temperature rise occurrence region.

(10) The controller controls the ratio of the power supplied to the sub-heaters to the total power supplied to all the heaters.
It is characterized in that it is made larger during the warm-up period when the heating member is heated to a predetermined heating temperature than during the fixing operation in which the medium to be heated is heated.

Only the main heater exists in the central part of the heating member, but since the main heater and the sub-heaters exist at both ends of the heating member, the total heat capacity to be heated (heating member plus heater) that needs to be heated at the time of temperature rise is The both ends of the heating member are larger than the central part of the heating member. Therefore, at the time of temperature increase, the rate of temperature increase at both ends of the heating member can be increased by increasing the amount of power supplied to the sub-heater or increasing the ratio of power supplied to the sub-heater.

(11) The controller is characterized in that the electric power supplied to the main heater is controlled to be constant during the fixing operation and the warm-up time.

The same effect as the above (10) can be obtained. Further, since the main heater can be constantly used with a constant power, the efficiency is excellent and the life of the main heater can be extended.

(12) It is characterized by comprising the heating device of the above (6) and a control unit for independently controlling the main heater and the left and right sub-heaters based on the outputs of the temperature detecting elements.

Regarding the both ends of the heating member, the shape of the heating member is not symmetrical at all on the left and right, and the ambient environmental conditions may be different on the left and right depending on usage conditions. Is not always constant on the left and right.

When a plurality of sub-heaters are driven and controlled under the same condition based on the temperature information of one temperature detecting element, the amount of heat supplied to both ends of the fixing roller is always the same. There is a possibility that a temperature difference will occur.

On the other hand, in the heating device of the present invention, since the heat is supplied to both ends (left and right) of the heating member independently, it is possible to always maintain a constant temperature regardless of usage conditions (13). The heating device according to (7), and a control unit that independently controls the main heater and the left and right sub-heaters based on the output of each of the temperature detection elements, and controls the left and right sub-heaters in common. It is characterized by doing.

Although the temperature at both ends (left and right) of the heating member cannot be controlled to be constant, it contributes to cost reduction and downsizing.
This is useful when precise control is unnecessary.

(14) The heating device according to any one of the above (5) to (8), and a control unit for controlling the lighting timings of the left and right sub-heaters so that they do not match when the medium to be heated is passed. It is characterized by

Since the left and right sub-heaters are not turned on at the same time, the temperature ripple can be reduced.

[0055]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment in which a heating device and a heating system of the present invention are applied to a fixing device in an electrophotographic apparatus will be described below with reference to FIG.

FIG. 1 is a sectional view showing a system example of an image forming system 1 using an electrophotographic process to which the fixing device of the present invention is applied.

As shown in FIG. 1, the image forming system 1
With the printer 2 as the core, the scanner 3, the automatic document feeder 4, the sheet post-processing device 5, the multi-stage sheet feeding unit 6, and the relay feeding unit 8 are connected to expand the function. The scanner 3 has an automatic document feeder 4 arranged above it.
In addition, the printer 2 is supported on the system rack 7 and is disposed above the printer 2 and the sheet post-processing device 5.

A brief description will be given below of each device.

(Printer 2) The printer 2 is the scanner 3
In addition to recording and outputting the image read in, the image data from the externally connected device is recorded and output when an image processing device such as a personal computer is connected.

In the printer 2, an electrophotographic process section 20 centering on a drum-shaped photosensitive member 200 is arranged on the right side of the center of the apparatus main body. Around the photoconductor 200, charging means for uniformly charging the surface of the photoconductor 200,
An optical scanning unit 22 that scans a light image on the uniformly charged photoreceptor 200 to write an electrostatic latent image, and a developing unit that visualizes the electrostatic latent image written by the optical scanning unit 22 with a developer. And a transfer unit for transferring the image stored and reproduced on the photoconductor 200 onto a sheet, and the photoconductor 200
A cleaning unit that removes the developer remaining on the surface of the photoconductor 200 to record a new image, and a discharge lamp unit (not shown) that removes the charges on the surface of the photoconductor 200 are sequentially installed. It is arranged.

Below the main body of the printer 2, there is arranged a paper supply unit 21 which is internally provided in the main body of the printer 2. The paper supply unit 21 includes a paper storage tray 210 that stores paper.
And a separation / supply means 211 for separately supplying the paper stored in the paper storage tray 210 one by one. The sheets separated and supplied one by one from the sheet supply unit 21 are
The images are sequentially supplied to the photoconductor 200 and the transfer unit 203 of the electrophotographic process unit 20, and the recorded and reproduced image is transferred onto the photoconductor 200. Note that the paper is supplied to the paper supply unit 21 by pulling out the paper storage tray 210 on the front side of the printer 2 main body.

On the lower surface of the main body of the printer 2, the sheet sent from the multi-stage sheet feeding unit 6 or the like prepared as a peripheral device is received, and the photoconductor 2 of the electrophotographic process section 20 is received.
00 and the transfer unit 203 are provided with a sheet receiving port 27 for sequentially feeding.

A fixing device 23 is arranged above the electrophotographic process section 20. The fixing device 23 is sequentially received, and the developer transferred onto the paper is heated and fixed to the outside of the fixing device 23. Send the paper to. The sheet on which the image is recorded is discharged from the discharge roller 28 of the printer 2 to the printer 2
It is delivered to the relay transport unit 8 on the upper surface of the main body. As described above, the paper transport path 64 of the printer 2 is configured to be substantially vertical from bottom to top.

In the upper and lower spaces of the optical scanning unit 22, a printer control unit 24 for accommodating a process control unit (PCU) substrate for controlling the electrophotographic process and an interface substrate for receiving image data from outside the apparatus, an interface substrate. The image control unit 25 including an image control unit (ICU) substrate for subjecting the image data received from the image data to a predetermined image processing and scanning and recording as an image by the optical scanning unit 22, and these various substrates, and A power supply unit 26 for supplying electric power to the unit is arranged.

(Multistage Paper Feeding Unit 6) The multistage paper feeding unit 6 is an external paper feeding device and has three paper feeding portions 61, 62, 63. Each paper supply unit 61,
The sheets accommodated in the sheet accommodating trays 610, 620 and 630 of 62 and 63 are separated and fed by means of separation feeding means 611, 621 and 631.
The sheets are separated one by one, and are supplied to the sheet discharge port 65 provided on the upper surface of the unit and communicating with the sheet receiving port 27 of the printer 2.

In the present invention, the sheet supply units 61, 62, 63 accommodating sheets of a desired size selectively operate during operation. Replenishment of paper to the paper supply units 61, 62, and 63 is performed by inserting a paper storage tray 610, on the front side of the unit main body.
This is performed by pulling out 620 and 630, and the paper feeding unit 62
Papers of the same size are stored in and 63.

Further, the multi-stage paper feeding unit 6 is constructed such that the printer 2 and the post-processing device 5 are mounted on the upper part thereof, but it can be moved in this state and fixedly arranged between the system racks 7. As described above, the moving roller 69 and the fixed portion 6 are provided at the bottom.
Eight. At the time of movement, the fixed portion 68 is rotated and lifted to separate the fixed portion 68 from the floor surface, and at the time of fixing, the fixed portion 68 is rotated and moved downward to bring the fixed portion 68 into contact with the floor surface, thereby providing a multi-stage structure. The paper feeding unit 6 is fixed.

In the description of FIG. 1, an apparatus having three different paper feeding units 61, 62, 63 is explained, but three paper feeding units having the same one are stacked in plural stages or only one. There are various ones.

(Sheet Post-Processing Device 5) The sheet post-processing device 5 includes the relay conveyance unit 8 and the printer 2 above the device.
The paper on which the image discharged from the sheet is recorded is carried in by the carry-in roller 50.
In this case, the paper is post-treated.

The post-processing includes stapling processing, sorting processing and the like, but the apparatus illustrated in FIG. 1 performs stapling processing, and the post-processing is post-processing on the lower sheet discharge tray 59. Those that are not discharged are selectively discharged to the upper discharge tray 56 by the switching gate 52.

(Scanner 3) The scanner 3 automatically supplies a sheet original by the automatic original conveying device 4 and sequentially exposes and scans the originals one by one to automatically read an original image. Alternatively, it is provided with a manual reading mode in which a document of a sheet that cannot be automatically fed by the automatic document feeder 4 is manually set to read a document image. Then, the transparent document placing table 3
The image of the original document set on the substrate 0 is exposed and scanned by the first scanning unit 31 and the second scanning unit 32 which move along the original document table 30 in a predetermined speed relationship with each other, and the mirror and the imaging lens 33 are scanned. Photoelectric conversion element 3 guided by optical parts such as
The image of the original is converted into an electric signal and then output.

(Automatic Document Feeding Device 4) The automatic document feeding device 4 feeds the document placed on the document setting tray 40 toward the document placing table 30 and places the scanned document on the document discharging tray 42. A document feeding unit 41 for discharging the document is provided. Further, in order that a document of a sheet that cannot be automatically supplied is placed on the document table 30 and can be scanned, the document is rotated upward with the back side of the device as a fulcrum so that the front side of the device is opened. Is configured.

(Relay Transport Unit 8) The relay transport unit 8 is mounted on the discharge tray 29 provided at the top of the printer 2 and collects the image-recorded sheet discharged from the discharge roller 28 of the printer 2. , A conveying unit for introducing the sheet toward the sheet post-processing device 5 located on the downstream side of the printer 2.

In the middle of the sheet conveying path 84 of the relay conveying unit 8, the sheet is formed on the discharge tray 9 formed by the upper surface 82 of the unit and the upper surface 54 of the sheet post-processing apparatus 5.
Another sheet conveying path 83 that guides the sheet to is branched. Two
One discharge destination is a gate 81 arranged at a branch portion of the transport path.
It can be changed by switching.

Next, regarding the fixing device 23 according to the present invention,
This will be described in detail with reference to FIG.

As shown in FIG. 2, the fixing device 23 detects the temperature of the heating roller (fixing roller) 300 which is a heating member, the halogen heater 301 which constitutes the heating means for heating the heating roller 300, and the heating roller 300. It is provided with a temperature sensor 302 which constitutes a temperature detecting means, a control circuit (not shown) which is a temperature controlling means, and a pressure roller 303.

The halogen heater 301 is used for the fixing roller 30.
When the halogen heater 301 is placed in the interior of the fixing roller 300, the halogen heater 301 emits light with a predetermined heat distribution and infrared rays are radiated to heat the inner peripheral surface of the fixing roller 300.

The fixing roller 300 is the halogen heater 30.
This is for heating the recording paper, which is the medium to be heated, which is heated to a predetermined temperature (here, 200 ° C.) by 1 and passes through the nip portion 310 of the fixing device. Fixing roller 3
00 includes a cored bar 320 which is its main body, and a template layer 321 formed on the outer peripheral surface of the cored bar 320 in order to prevent the toner on the recording paper from being offset.

For the core metal 320, for example, a metal such as iron, stainless steel, aluminum, copper, or an alloy thereof is used. In addition, as the core metal 320 of this embodiment,
An iron (STKM) cored bar having a diameter of 40 mm and a wall thickness of 0.2 mm is used.

The release layer 321 includes PFA (copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether) and PTFE (polytetrafluoroethylene).
Fluororesin, silicone rubber, fluororubber, etc. are suitable. A fluororesin is used as the release layer 321 of this embodiment.

The pressure roller 303 is constructed such that a heat resistant elastic material layer 331 such as silicone rubber is provided on the outer peripheral surface of a core metal 330 such as steel, stainless steel or aluminum. On the surface of the heat resistant elastic material layer 331 of the pressure roller 303, a release layer 332 made of a fluororesin similar to that of the fixing roller 300 may be formed. The pressure roller 303 in this embodiment has a diameter of 30 mm, a heat-resistant elastic layer made of silicone rubber, and a template layer made of PFA tube. The fixing roller is made of an elastic member such as a spring (not shown). It is configured to be pressed against the fixing roller with a force of 200 N, whereby a nip portion 310 having a width of about 6 mm is formed between the fixing roller and the fixing roller.

Next, the heating control method in this embodiment will be described in detail with reference to FIGS.

[0083]

Embodiment 1 FIG. 3 shows a schematic structure in which the present invention is applied to a so-called center registration type fixing device in which a recording paper which is a medium to be heated is fed with reference to the center position of a fixing roller 300. It is a figure.

The halogen heater 301 which is the heating means of the fixing device heats the main heater 3010 for heating the central portion of the fixing roller, the sub-heater L3011 for heating the left end portion of the fixing roller, and the right end portion of the fixing roller. It consists of a total of three sub-heaters R3012 for.

The main heater 3010 is a so-called double end type heater having energizing terminals on both sides which is generally used in a fixing device, and is a sub heater L301.
1. The sub-heater R3012 is a so-called single-end type heater having an energizing terminal only on one side.

Both the main heater and the sub-heater have a hollow glass tube (bulb) 303 in which a filament 304 made of tungsten and a halogen-based inert gas are sealed, and the filament 304 is energized to generate Joule heat to generate a high temperature state. The principle is to emit infrared rays. Here, a halogen cycle using a halogen gas is used to return the tungsten that has been heated to a high temperature and evaporated to the filament 304. To maintain this halogen cycle, a glass tube (bulb) 303 is used.
Needs to be heated to a temperature of 250 ° C. or higher (usually about 475 ° C.).

FIGS. 4 and 5 are views showing the heat distribution of the main heater 3010, the sub-heater L3011, and the sub-heater R3012. The control unit, which will be described later, controls so as to obtain such characteristics. FIG. 4 shows the heat distribution during the temperature raising operation, and FIG. 5 shows the heat distribution during the fixing operation. As shown in FIG. 4, the main heater 3010
The heat distribution area of the sub-heaters L301 and R301 is set so as to substantially coincide with the paper-passing area of B5 size (paper width) which is particularly frequently used among small size paper.
The second heat distribution area is set to cover the outside of the B5 size paper passing area. As a result, almost 100% of the main heater 3010 is at the center of the roller, and almost 100% of the sub-heater L3011 and the sub-heater R are at the roller end.
Heat is supplied from 3012.

As the temperature sensor 302, one in the heat distribution area of the main heater 3010 (thermistor M3020),
One in the heat distribution area of the sub-heater L3011 (thermistor L
Two thermistors 3012) are installed, and the signals detected by the thermistor M3020 and thermistor L3021 are taken into the CPU 308 which is the control unit via the input circuits 304 and 305. The CPU 308 controls the drivers 306 and 307 based on the detected roller surface temperature.
It is configured to control the energization of each heater via the. That is, the CPU 308 determines the main heater 3010 and the left and right sub-heaters L based on the outputs of the thermistors.
3011 and the sub-heater R3012 are independently controlled, while the left and right sub-heaters L3011 and the sub-heater R are
3012 is commonly controlled based on the detection signal of the thermistor L3021.

Next, a method of controlling the heater by the CPU 308 will be described in detail. The power supplied to each heater is controlled by phase control so that the main heater 550W,
The sub-heater is driven with 175W power distribution,
Main heater 450 during temperature raising operation (warm up)
It is configured to be driven by electric power distribution of 225 W for each W and sub heater. That is, the CPU 308 raises the ratio of the power input to the sub-heaters to the total power input to all the heaters so that the heating member is heated to a predetermined heating temperature more than during the fixing operation in which the heating target paper is heat-treated. The control is performed to make it larger at time (when warming up).
By doing so, the temperature rising time can be shortened.

The reason for this will be described below.

As described above, only the main heater 3010 exists in the central portion of the fixing roller, but since the main heater 3010, the sub-heater L3011, and the sub-heater R3012 exist in both ends of the fixing roller, heating is required when raising the temperature. The total heat capacity of the heating target (fixing roller + heater (filament and glass tube)) is larger at both ends of the fixing roller than at the center of the fixing roller. As a result, when the temperature is raised, the sub heater L3011, the sub heater R
It is more advantageous to distribute more power to the 3012 in order to increase the temperature evenly, but on the other hand, during the fixing operation,
On the contrary, this is because a large amount of electric power is required for the main heater 3010 as in the case of continuously passing small size paper.

In this embodiment, an example is shown in which the ratio of power supplied to each heater is changed without changing the total power supplied to the heaters. However, the power supplied to the main heater varies depending on whether the temperature is raised or fixed. There is no problem even if a control method of increasing the electric power input to the sub-heater without increasing the temperature is used. In this case, since the electric power supplied to the main heater is constant during the temperature rise and the fixing, the heat conversion efficiency of the main heater is excellent, and there is no concern that the life of the main heater is shortened by the phase control.

Next, the temperature rising characteristics of the fixing device will be described with reference to the drawings.

FIG. 6 shows the results of measuring the temperature rising characteristics of the fixing roller using this fixing device.

For comparison, the temperature rising characteristics of the conventional fixing device are also shown.

From FIG. 6, in the fixing device of the present invention,
It can be seen that the temperature rise time is reduced by about 22% compared to the conventional case. The reason for this will be described with reference to FIG. 7. Figure 7
17 is a table comparing the heat capacities of the fixing roller and the heater of the conventional fixing device shown in FIG. 17 and the fixing device of the present invention.

As shown in FIG. 7, in the fixing device of the present embodiment, the heat capacity of the heater is smaller than that of the conventional fixing device, so that the thermal energy required to heat to a predetermined temperature is small, and as a result, the fixing device is fixed. The total required thermal energy combined with the rollers is about 20% less, so the temperature rises faster. The reason why the heat capacity of the fixing device of this embodiment is small is shown in FIG.
Is clear from. That is, since the sub-heater L3011, and the sub-heater R3012 are single-end type heaters, the region between both sub-heaters is a complete non-heating region by the sub-heater.

The effect of shortening the temperature raising time is that the heat capacity ratio HCr / HCh is HCr / HCh when the heat capacity per unit length of the fixing roller is HCr and the heat capacity per unit length of the heater is HCh.
The smaller is the larger. FIG. 8 shows the results of examining the heat capacity ratio HCr / HCh of the fixing roller and the main heater and the shortening rate of the temperature rise time by simulation. From this, the heat capacity ratio HCr / HCh of the fixing roller and the heater is 1
It can be seen that if it is less than 4, a sufficient effect of a shortening rate of 10% or more can be obtained.

Next, the temperature followability of the present fixing device will be described with reference to the drawings.

FIG. 9 shows the results of examining the temperature followability of the fixing device of this embodiment. As experimental conditions, a fixing speed of 240 mm / s and a printing speed of 50 sheets / minute were used, and 100 sheets were continuously printed on a B5R size sheet (printing pattern was a text chart with a printing rate of 4%).

For comparison, the temperature rising characteristics of the conventional fixing device are also shown.

As shown in FIG. 9, in the conventional fixing device, the temperature of the fixing roller after passing 100 sheets is not in the non-offset temperature range (180
However, in the fixing device of the present invention, the set temperature is 200 ° C.
It can be seen that is maintained. This means that when B5R size paper is passed, both the conventional fixing device and the fixing device of the present embodiment turn on only the main heater, but from the comparison of FIG. 5 and FIG. The heat distribution of the main heater in the B5R size paper passing area is 10
This is because the required amount of heat supply is secured and the temperature followability is secured because it is 0%, which is larger than the conventional 80%. That is, in the conventional fixing device, in order to obtain 100% heat distribution, the heat distribution of 80% by the main heater and the heat distribution of 20% by the sub-heater are used to control the temperature of the small-size paper passing area. While only the power control to the main heater 500 is performed based on the temperature sensor 503 provided in that area (see FIG. 17), in the present embodiment, the temperature control of the small size sheet passing area is performed only by the main heater 3010. Therefore, it can be said that the present embodiment has better temperature following performance.

FIG. 10 shows the fixing device of the present embodiment.
Heat capacity HCr of fixing roller and feeding speed V of small size paper
It is a result of investigating a condition capable of ensuring temperature followability from the relationship with p. The conditions for ensuring temperature followability are:
It was decided that the fixing roller temperature after 100 sheets had been passed was maintained within the non-offset temperature range (180 ° C. or higher here), and the case of a conventional fixing device was also examined for comparison (FIG. 11). In the figure, ○ indicates × when the temperature followability is OK.
Indicates the case of NG. As shown in FIG. 10, in the fixing device of the present invention, temperature followability can be ensured in all areas, whereas in the conventional fixing device, Vp ≧ 38HCr + 39.
It is understood that the temperature followability cannot be ensured in the case of.
Therefore, the present invention is more effective when applied under the condition of Vp ≧ 38HCr + 39.

Next, FIG. 12 shows the result of examining the temperature distribution of the fixing roller in the cooling mode in the fixing device of this embodiment.
Shown in. For comparison, refer to FIGS. 20 and 21 showing the temperature distribution of the fixing roller in the cooling mode of the conventional fixing device.

In the present embodiment, the CPU 308 executes the heating medium of a size smaller than the heat generation area of the main heater 3010 (size smaller than B5R size: medium of A5R size, for example) continuously for a certain period of time. Set the cooling mode to turn off the main heater 3010,
In this cooling mode, control is performed to turn on only the sub-heater L3011, the sub-heater R3012 under predetermined conditions. The predetermined condition referred to here is a parameter condition for determining the number of sheets that have been continuously fed and how long the continuous copying time was, and controlling the ON time of the sub-heater L3011, the sub-heater R3012 based on this. In general,
If the number of continuously fed sheets is large or the continuous copying time is long, the sub heater L3011, the sub heater R3012 are turned off.
A parameter for lengthening N hours is set.

In the conventional fixing device (FIG. 20), the roller temperature in the non-sheet passing portion temperature rise generating portion is cooled to the fixing set temperature (200 ° C.) or lower by cooling for 15 seconds, but the non-sheet passing portion temperature rises. The temperature of the fixing roller on the outer side (both ends) of the generation portion is too lower than the fixing temperature. In order to suppress this temperature drop in the end portion, when only the sub-heater is turned on under a predetermined condition during the cooling mode (FIG. 21), heat is also supplied to the non-sheet-passing portion temperature rise occurrence region by the sub-heater. It takes about 20 seconds to cool the paper part temperature rise occurrence region to 200 ° C. or less, which is the set fixing temperature, which is delayed.

On the other hand, in this embodiment, while the sub-heater L3011 and the sub-heater R3012 are turned on in the cooling mode under a predetermined condition, the heat of the sub-heater is not supplied to the non-sheet-passing portion temperature rise occurrence region, and therefore, it is shown in FIG. As can be seen, the cooling time is as fast as 15 seconds, and the roller temperature distribution after cooling is almost uniform.

[0108]

[Embodiment 2] Next, referring to FIG. 13, a case where the present invention is applied to a so-called side registration type fixing device in which a recording paper, which is a medium to be heated, is fed with reference to an end position of a fixing roller, will be described. Explain. Since the configuration other than the method of arranging the halogen heater is the same as that of the first embodiment, the description thereof is omitted here.

The halogen heater, which is the heating means of the fixing device, comprises a main heater 3013 for heating the central portion to the right side portion of the fixing roller 300 and a sub-heater 3014 for heating the left side portion of the fixing roller 300 in total. .

The main heater 3013 is a double end type heater, and the sub heater 3014 is a single end type heater having an energizing terminal only on one side.

Although the main heater 3013 may be a single end type and the sub heater 3014 may be a double end type, or both the main heater 3013 and the sub heater 3014 may be a single end type, the heating area of the sub heater 3014 is smaller than that of the main heater 3013. Narrow (wide non-heated area). Therefore, the sub heater 301
The effect of shortening the warm-up when 4 is a single end type and the effect of improving the heat supply efficiency when passing a medium of a small size are higher than when the main heater 3013 is a single end type. On the other hand, since the main heater has a long heating area, it is more preferable to support the main heater at both ends in terms of ensuring strength. Therefore, in this embodiment, a single end type is used for the sub heater 3014 and a double end type is used for the main heater 3013.

FIG. 14 is a diagram showing the heat distribution of the main heater 3013 and the sub heater 3014. As shown in FIG. 14, as the heat distribution area of the main heater 3013,
Of the small size paper, it is set so that it is almost the same as the B5 size (paper width) sheet passing area that is particularly frequently used (250 m
m) and the heat distribution area of the sub heater is
It is set to cover the outside of the B5 size paper passing area. From this, almost 100% from the center of the roller to the right side
From the main heater 3013, almost 1 on the left side of the roller
Heat is supplied from the 00% sub-heater 3014.

As the temperature sensor, the main heater 301
3 in the heat distribution area (thermistor M3022) and one in the sub-heater 3014 heat distribution area (thermistor S302).
A total of two thermistors 3) are installed, and the signals detected by the thermistor M3022 and thermistor S3014 are taken into the CPU 308 via the input circuits 304 and 305. The CPU 308 is configured to energize each heater via the drivers 306 and 307 based on the detected roller surface temperature.

[0114]

Third Embodiment Next, a fixing device according to a third embodiment of the present invention will be described with reference to FIG. In the third embodiment, the configuration other than the temperature control method including the thermistor is exactly the same as that of the first embodiment, and therefore the description thereof is omitted here.

The halogen heater which is the heating means of the fixing device is a main heater 3010 for heating the central portion of the fixing roller 300, a sub-heater L3011 for heating the left end portion of the fixing roller 300, and the fixing roller 300.
It is composed of a total of three sub-heaters R3012 for heating the right end portion of the.

The main heater 3010 is a so-called double end type heater which has energizing terminals on both sides and is generally used in a fixing device, and is a sub heater L301.
1. The sub-heater R3012 is a so-called single-end type heater having an energizing terminal only on one side.

As the temperature sensor, one is provided in the heat distribution area of the main heater (thermistor M3020), and the sub-heater L3 is used.
One in the heat distribution area of 011 (thermistor L3021) and one in the heat distribution area of sub-heater R3012 (thermistor R3).
024), a total of three thermistors are installed, the thermistor M3020, the thermistor L3021, and R302.
The signals detected at 4 are input circuits 304, 305, 30
It is taken in by CPU 308 through 9. CPU30
8 is a driver 30 based on the detected roller surface temperature.
The heaters are configured to control energization via 6, 307 and 310. That is, the CPU 308 independently controls each of the main heater 3010, the sub-heater L3011, and the sub-heater R3012 based on the output of each thermistor. The effects of the above configuration will be described below.

Regarding both ends of the fixing roller, the shape of the fixing roller is not symmetrical on the left and right, and the surrounding environmental conditions are
The amount of heat radiated from both ends of the heating member is not always constant on the left and right, because the right and left may differ depending on the usage conditions.

When the two sub-heaters are driven and controlled under the same conditions as in the first embodiment, the amount of heat supplied to both ends of the fixing roller is always the same. Therefore, a temperature difference may occur at both ends of the fixing roller depending on the usage conditions. There is a possibility that it will end up.

On the other hand, in the fixing device of this embodiment, the heat is supplied to both ends (left and right) of the fixing roller independently of each other, so that the temperature can always be maintained at a constant temperature regardless of the usage conditions.

As another embodiment, the lighting timings of the left and right sub-heaters L3011 and R3012 may be controlled so that they do not match.

The present invention has the following effects.

This leads to a reduction in the heat capacity of the fixing device as a whole. As a result, the warm-up time can be shortened.
Further, the power distribution to each heater is optimized, the heat supply efficiency can be improved when a small-sized medium is continuously fed, and good heat followability can be secured.

Further, the sub-heater is of single-end type, and heat is supplied only to both ends of the heating member,
By turning on only the sub-heater under a predetermined condition during the cooling mode, it is possible to prevent the temperature drop at both ends of the heating member without delaying the cooling time of the non-sheet passing portion temperature rise occurrence region.

Further, at the time of temperature rise, the rate of temperature rise at both ends of the heating member can be increased by increasing the power supplied to the sub-heater or increasing the ratio of power supplied to the sub-heater.

[Brief description of drawings]

FIG. 1 is a cross-sectional configuration diagram illustrating a system example of an image forming system to which a fixing device according to an exemplary embodiment of the present invention is applied.

FIG. 2 is a diagram showing a cross-sectional configuration of a fixing device according to an embodiment of the present invention.

FIG. 3 is a diagram showing a schematic configuration of a fixing device in a first embodiment of the invention.

FIG. 4 is a diagram showing a heat distribution of a heater in the first embodiment.

FIG. 5 is a diagram showing a heat distribution of a heater in the first embodiment.

FIG. 6 is a graph showing the temperature rise characteristics of the fixing device in the first embodiment.

FIG. 7 is a table comparing heat capacities of a fixing roller and a heater of a conventional fixing device and a fixing device of the present invention.

FIG. 8 is a graph showing the relationship between the heat capacity ratio of the fixing roller and the heater and the shortening rate of the temperature rising time in the fixing device of the first embodiment.

FIG. 9 is a graph showing a temperature following characteristic of the fixing device in the first embodiment.

FIG. 10 is a graph showing the relationship between the heat capacity of the fixing roller, the feeding speed of small-sized paper, and the temperature followability in the fixing device of the first embodiment.

FIG. 11 is a graph showing the relationship between the heat capacity of the fixing roller, the feeding speed of small size paper, and the temperature followability in the conventional fixing device.

FIG. 12 is a diagram showing the temperature distribution of the fixing roller after the cooling mode of the fixing device in the first embodiment.

FIG. 13 is a diagram showing a schematic configuration of a fixing device according to a second embodiment of the invention.

FIG. 14 is a diagram showing a heat distribution of a heater in the second embodiment.

FIG. 15 is a diagram showing a schematic configuration of a fixing device according to a third embodiment of the invention.

FIG. 16 is a schematic configuration diagram of a conventional fixing device (first method).

FIG. 17 is a schematic configuration diagram of a conventional fixing device (second method).

FIG. 18 is a diagram showing a heat distribution of a heater in a conventional fixing device (second method).

FIG. 19 is a diagram showing a temperature rise characteristic of a non-sheet passing portion.

FIG. 20 is a diagram showing a temperature distribution in the fixing roller axial direction of a conventional fixing device (second method).

FIG. 21 is a diagram showing a temperature distribution in the fixing roller axial direction of a conventional fixing device (second method).

[Explanation of symbols]

3010: Main heater 3011: (single end type) sub heater L 3012: (single end type) sub heater R

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03G 21/00 384 G03G 21/00 372 21/14 B41J 3/04 101Z F term (reference) 2C056 EA25 EB02 EB03 EB04 EB14 EB30 EC02 EC03 EC04 EC14 EC29 HA45 HA46 2H027 DA12 DA20 DA38 DA46 DC10 DE10 EA12 ED25 EE01 EF04 EF09 2H033 AA03 AA30 BA25 BA27 BA31 BA32 BA59 CA36 CA37 CA37 CA37 CA37 CA37 CA37 CA32 CA37 CA30 BB03 BB03 BB21 BB30 BB21 BB30 BB21 BB30 BB21 BB30 BB21 BB30 BB21 BB30 BB21 BB30 BB21 BB30 BB21 BB30 BB21 BB30 BB21 BB30 BB21 BB21 BB30 BB21 BB30 BB21 BB30 BB21 BB30 BB30 BB21 BB30 BB21 BB30 BB21 BB30 BB21 BB30 BB22 BB30 BB21 BB30 BB22 3K058 AA03 AA65 AA71 AA81 AA86 AA88 BA18 CA23 CA45 CA61 CB02 CB10 CB22 CE24 DA02 DA06 GA06

Claims (14)

[Claims] 1. A heating member having a cylindrical heating member heated to a predetermined temperature by a heating means, and a pressing member press-contacting the heating member to form a press-contact portion, and a medium to be heated is conveyed to the press-contact portion. A heating device for heating a medium to be heated,
The heating means is composed of a plurality of heaters having different heating regions corresponding to the width of the medium, and at least one heater among the plurality of heaters has two electrodes for energization, which are end faces on the same side of the heating member. A heating device characterized by being a single-ended type that is placed in. 2. The main heater for heating the paper passage width area of a small-sized medium to be heated, and the plurality of heaters excluding the small-size paper passage width area from a large-sized medium to be heated. It consists of a sub-heater for heating the paper width area,
The heating device according to claim 2, wherein the sub-heater is a single end type. 3. The heating according to claim 2, wherein Vp ≧ 38HCr + 39 when the heat capacity per unit length of the heating member is HCr and the feeding speed of a small-sized medium to be heated is Vp. apparatus. 4. The heat capacity per unit length of the heater is H
The heating device according to claim 2, wherein, when Ch and the heat capacity per unit length of the heating member are HCr, HCr / HCh <14. 5. The main heater is of a double end type in which two electrodes for energization are arranged on both end surfaces of the heating member, and the heating area has a small size from the center to the left and right of the heating member. The heating device according to any one of claims 2 to 4, wherein the heating device is opposed to a sheet passing width region of the medium, and at least one sub-heater is arranged at each end of the heating member. .. 6. The heating apparatus according to claim 5, wherein a temperature detecting element is provided on the heating member facing the main heater and each of the left and right sub-heaters at both ends of the heating member. 7. The heating device according to claim 5, wherein a temperature detecting element is provided on the heating member facing the main heater and one of the left and right sub-heaters at both ends of the heating member. 8. The heating device according to claim 1, wherein the heater has a heating element such as a halogen heater and a nichrome wire heater, and a heat-resistant sealing material. 9. A heating device according to any one of claims 1 to 8 and a control unit for controlling a current to the heater, wherein the control unit controls a medium to be heated having a size smaller than a heat generation region of the main heater. A cooling mode is set to turn off the main heater for a certain period when paper is continuously fed.
A heating system which controls to turn on only a sub-heater under a predetermined condition to eliminate a temperature rise in a non-sheet passing portion of a heating member caused by continuously passing a medium to be heated of a small size. 10. The control unit raises the heating power of the heating member to a predetermined heating temperature with respect to the ratio of the power input to the sub-heaters to the total power input to all the heaters, as compared with the fixing operation in which the heating target medium is heat-treated. The heating device according to claim 9, wherein the heating device is increased in warm-up time. 11. The heating apparatus according to claim 10, wherein the control unit controls the electric power supplied to the main heater to be constant during the fixing operation and the warm-up time. 12. A heating system comprising: the heating device according to claim 6; and a control section for independently controlling a main heater and left and right sub-heaters based on the outputs of the temperature detecting elements. 13. A heating device according to claim 7, and a control unit for independently controlling the main heater and the left and right sub-heaters based on the output of each of the temperature detecting elements, and for commonly controlling the left and right sub-heaters. A heating system characterized by the following. 14. A heating device according to claim 5,
A heating system comprising: a control unit that controls the lighting timings of the left and right sub-heaters so that they do not match when the medium to be heated is passed.