JPH07319318A - Image forming device - Google Patents

Abstract

PURPOSE:To attain the improvement of fixability and reduction in loss of energy by controlling the temperature control temp. of a heater in accordance with the image density of each part in images on a paper sheet, in an image forming device provided with a surf fixing unit. CONSTITUTION:In the image forming device provided with a means forming an unfixed toner image on the surface of a recording material, a means heating/ fixing the unfixed toner image on the surface of the recording material via a fixing film by a heater, etc., the heater 3 is constituted to provide a heat generating part whose longitudinal direction is the transverse direction of the fixing film and an energization and heat generation control means 69 generating heat so as to change the temperature control temp. of the heat generating part in accordance with output image information and the temperature control temp. is set higher in a region where the image density is lower to improve the fixability and low in a white part to reduce the loss of energy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus.

In particular, a fixing film, a running drive means for the fixing film, a heating body disposed on one side of the fixing film with the fixing film in the middle, and a heating body disposed on the other side thereof with respect to the heating body. The recording material is provided with a pressure member for closely contacting the surface of the recording material on which the unfixed toner image is carried with the fixing film, and is the same as the conveying speed of the recording material carrying the unfixed toner image conveyed from the image forming means side. An image forming apparatus equipped with a toner image heat fixing means for introducing the recording material between a fixing film and a pressing member that are driven to run in the same direction at a speed to heat and fix an unfixed toner image on the surface of the recording material. Regarding

[0003]

2. Description of the Related Art An electrophotographic system is a typical example of an image forming apparatus. This method requires a means for fixing the toner image on the recording material. Generally, as the fixing means, a roller fixing means, a fixing film, a traveling driving means for the fixing film, a heating element disposed on one side of the fixing film and a heating element disposed on the other side thereof. ,
A recording which is provided with a pressure member for adhering the surface of the recording material on the unfixed toner image carrying side to the heating body via the fixing film, and carries the unfixed toner image conveyed from the image forming means side. Toner image heating and fixing means for introducing the recording material between the fixing film and the pressing member that are driven to run in the same direction at the same speed as the material conveying speed to heat and fix the unfixed toner image on the surface of the recording material. There is. The former is often used for medium- and high-speed machines, and the latter is used for low-speed machines in order to make the most of their characteristics.

In both cases, fixing is performed by using a control means that stabilizes at the temperature required for fixing.

[0005]

However, except when the toner image is evenly distributed over the entire surface of the recording material, the temperature is uniformly controlled in one image, that is, heat is applied to a portion having no image. Leads to a loss of energy. Further, the temperature required for fixing differs depending on the image density, and it is necessary to change the temperature during fixing of one recording material according to the image. Further, if the temperature control temperature is raised and kept constant in order to secure the fixing property, problems such as temperature rise at the edges and heat durability also arise.

An object of the present invention is to provide an image forming apparatus which solves the problems such as the fixing property and energy loss as described above.

[0007]

SUMMARY OF THE INVENTION The present invention is an image forming means for forming a non-fixed toner image corresponding to target image information by carrying a toner made of a heat-meltable resin or the like on the surface of a recording material. A fixing film, a driving means for driving the fixing film, a heating body disposed on one side of the fixing film and a heating body disposed on the other side of the fixing film, and the fixing film with respect to the heating body. The recording material is provided with a pressure member for closely contacting the surface of the recording material on which the unfixed toner image is carried, and the same speed as that of the recording material carrying the unfixed toner image carried from the image forming means side. A toner image heat fixing means for introducing the recording material between the fixing film driven to run in the direction and the pressure member to heat and fix the unfixed toner image on the surface of the recording material. Heating of heat fixing means Is an image having a heat generating part having a longitudinal direction in the transverse direction of the fixing film on the contact surface side with the fixing film, and an energization heat generation control means for causing heat generation so that the temperature control temperature of the heat generating part is changed according to output image information. A forming apparatus is provided.

According to the present invention, by providing the output image detecting means, it is possible to know the temperature required for fixing the image on one recording material, and by changing the fixing temperature on the same recording material surface, It is possible to properly fix each output image.

[0009]

[Embodiment] Next, one embodiment of the present invention (digital & halftone temperature control up & memory loading) will be described.

Embodiment 1 1) Example of Image Forming Apparatus FIG. 1 shows a schematic structure of an example of an image forming apparatus using a fixing device 60 described later according to the present invention.

The image forming apparatus of this embodiment is a digital type electrophotographic copying apparatus.

When the original 19 is placed on the fixed original glass 20 and the required copying conditions are set and the copy start key is pressed, the photosensitive drum 39 moves at a predetermined peripheral speed in the clockwise direction indicated by the arrow. Is rotated and moved.

Further, the light source 21 (22 is a reflection shade) and the first mirror 23 move forward along the lower surface of the original table glass 20 from the home position on the left side of the glass to the right side of the glass at a predetermined speed V, and the second mirror. By moving the third mirrors 24 and 25 in the same direction at a speed of V / 2, the downward image surface of the document 19 placed on the document table glass 20 is illuminated from the left side to the right side, and its illumination scanning is performed. The light reflected from the document surface is formed by the imaging lens 2
9. The image is irradiated onto the CCD 61 through the fixed fourth mirror 26, and converted into a digital signal by the A / D converter 62 in FIG.

Image information converted into a digital signal is passed through an image processing device 63 shown in FIG. 4, which will be described later, to perform image processing, and is further converted into an analog signal by a D / A conversion device 65. Semiconductor laser 67
Light up.

The laser light is expanded in the longitudinal direction by passing through a polygon mirror 40 rotating at a high speed and a constant speed and an Fθ lens 41, and is imagewise exposed on the surface of the rotating photosensitive drum 39 via fixed mirrors 27 and 28. It

Prior to this exposure, the surface of the rotary photosensitive drum 39 is uniformly charged to a predetermined positive or negative potential by the primary charger 30, and the charged surface is exposed as described above. As a result, electrostatic latent images having a pattern corresponding to the original image are sequentially formed on the surface of the photosensitive drum 39. The electrostatic latent image formed on the surface of the photosensitive drum 39 is visualized as a toner image by the developing roller 32 of the developing device 31.

On the other hand, the transfer material sheet P as a recording material is fed by the paper feed roller 61 and introduced into the transfer portion between the photosensitive drum 39 and the transfer charger 34 at a predetermined timing through the guide 33. By receiving the transfer corona, the toner visible image on the surface of the photosensitive drum 39 is transferred to the surface of the sheet P sequentially while coming into contact with the photosensitive drum 39.

The sheet P that has passed through the image transfer portion is charged with a charge eliminating needle 35.
While the back surface charge is removed by the photosensitive drum 39,
The transport section 38 and the entrance guide 10 are sequentially separated from the surface.
Then, the toner image is fixed to the fixing device 60 as described later, and is discharged outside the apparatus as an image formed product.

After the transfer, the surface of the photosensitive drum 39 is cleaned by a cleaning blade 37 of a cleaning device 36 to remove stains such as residual toner, and is repeatedly used for image formation.

When the moving optical members 21 to 25 that have moved forward move to a predetermined forward movement end point, they are turned back to return to the initial home position and wait until the start of the next copy cycle. The resolution is 400 dpi for both input and output.

2) Structure of Fixing Device 60 FIG. 2 is a side sectional view of the fixing device 60 of the electrophotographic copying machine, which is an example of the heating device according to the present invention. Reference numeral 6 denotes an endless belt-shaped fixing film, which includes a driving roller 7 on the left side, a driven roller 8 on the right side, and both rollers 7, 8
3 of the low heat capacity linear heater 1 fixedly arranged below
It is stretched around the members 7, 8 and 1. The driven roller 8 also serves as a tension roller for applying tension in a direction to stretch the fixing film 6 outward, and the fixing film 8 is driven to rotate clockwise of the driving roller 7 whose surface is coated with silicon rubber or the like to increase the friction coefficient. Along with this, it is rotationally driven at a predetermined peripheral speed in the clockwise direction without wrinkles, meandering or speed delay.

Reference numeral 9 denotes a pressure roller as a pressure means having a rubber elastic layer having a good releasability such as silicon rubber, and is provided between the heater 1 and the lower film portion of the endless belt-shaped fixing film 6 described above. And a total pressure of 5 to 1 against the lower surface of the heater 1 by urging means such as a spring.
The sheets are pressed against each other with a contact pressure of 0 kg, and the sheet p
It rotates in the counterclockwise direction, which is the forward direction of the transport direction.

Since the endless fixing film 6 which is rotationally driven is repeatedly subjected to heat fixing of the toner image, it is excellent in heat resistance, separation and durability, and is generally 100.
A thin wall having a thickness of μ or less, preferably 40 μ or less is used. As an example, a PTFE (4) is formed on the outer peripheral surface of a thin endless belt made of a highly heat-resistant resin such as polyimide, polyetherimide, polyethersulfone, polyether, or ether ketone having a thickness of 20 μ, or a metal such as nickel or SUS.
A low surface energy resin such as fluorinated ethylene resin), PFA (tetrafluoroethylene, perfluoroalkyl vinyl ether copolymer resin), or a release coating layer in which a conductive material such as carbon black is added to these resins. 10
It is an endless belt with a total thickness of 30μ, which is applied to a μ thickness.

The heater 1 having a low heat capacity extends in the transverse direction of the endless film 6 and has, for example, an alumina substrate 2 having a thickness of 1.0 mm, a width of 10 mm and a longitudinal length of 340 mm, and a resistance such as ginpalladium or ruthenium oxide. The heat-generating layer 3 is formed by coating the material with a thickness of 10 μm and a width of 1.0 mm, and a protective layer 4 such as glass is formed on the heat-generating layer 3 in consideration of sliding with the film 6 having a thickness of 10 μm. Yes,
The heater support 11 is attached and held to be fixedly supported.

The heater support 11 has a heat insulating property, a high heat resistance, and rigidity for adiabatically supporting the heater 1 with respect to the fixing device 60 and the image forming apparatus. For example, PPS (polyphenylene sulfide) or PEEK (polyether ether). (Ketone), liquid crystal polymer, or other high heat resistant resin, or a composite material of these resins and ceramics, metal, or the like.

The heating layer 3 of the heater is energized from both ends in the longitudinal direction. The energization is 100 V AC, and the microcomputer MPU69 (FIG. 3) is used according to the detection temperature of the temperature detecting element 5 such as an NTC thermistor or the like, which is adhered or pressure-bonded or integrally formed on the back surface of the substrate 2 with a heat conductive silicon adhesive or the like. The energization is controlled by.

FIG. 3 is a side view of the heater 1 as seen from the paper feed side. The heat generating layer 3 is formed in a straight line along the length of the substrate at the center of the lower surface of the substrate 2. Reference numerals 3a and 3b denote current-carrying electrodes (input terminals) made of a good conductive material such as silver provided at the left and right ends of the heat generating layer 3. e is the effective total length area of the heat generating layer 3 between the electrodes 3a and 3b. In the case of this example, the maximum size transfer material sheet that can be supplied to the apparatus and used is the A3 plate (width 297 mm) and corresponds to the sheet width. It is designed to have a length dimension.

3) Control of fixing heater The image signal input from the CCD 61 is converted into an A / D converter 6
It is converted into a digital signal by 2. The digital signal is subjected to image processing such as gamma conversion processing and edge enhancement by the image processing device 63 based on the setting conditions input from the operation unit or the like. The processed signal is stored in the page memory 64.
Then, the halftone area detecting device 68 detects the halftone area in the image. And the sheet P
Enters the fixing device 60, and the MPU 69 controls the heater 1 of the fixing device so that the fixing temperature rises in synchronization with the fixing of the halftone area. Here, since the controlled temperature cannot be changed in the longitudinal direction, the average density of the image portion in the longitudinal direction is taken, and the heater is controlled in the paper feeding direction according to the density.

An example of actual temperature control will be described for the first intermittent copy.

As shown in FIG. 5, the heater 1 is energized in synchronization with the leading edge of the sheet p entering the fixing device 60.
Adjust the temperature to 0 degrees. When the laser output signal is FFH, the controlled temperature is raised to 150 degrees. Next, when the region of concentration 30H comes, the controlled temperature is raised to 180 degrees. Further, when 90H comes, the temperature control temperature is controlled to 160 degrees. Although it is not originally desired to energize the solid white portion, temperature control is performed at 100 degrees to stably control the heater. Where FFH, 9
0H, 30H, etc. are the values of the laser output control signal,
It is controlled by 256 values from 00H to FFH. The relationship between the laser output signal and the output image density is as shown in FIG.

Generally, it is necessary to change the temperature-controlled temperature according to the temperature of the pressure roller 9 or the like. Therefore, the temperature-controlled temperature of FFH is changed and controlled accordingly. The controlled temperature of the area is changed and controlled, and the controlled temperature of the halftone area is also changed in accordance with the temperature. That is, it is necessary to raise the temperature relatively to the controlled temperature of FFH. Therefore, the relationship between the laser output signal and the controlled temperature is stored in one table as shown in FIG.

FIG. 8 shows the dependency of the fixability when the control as shown in FIG. 7 is performed and when the temperature is adjusted at the proper temperature of the solid gloss without the control. FIG. 8B shows, as a conventional example, the fixing property when the fixing temperature is adjusted at a temperature suitable for satisfying the fixing property of the solid gloss and the temperature is adjusted. FIG. 8A shows the case where the present invention is applied, and shows the fixability when controlled by the relationship between density and temperature as shown in FIG. Here, the fixability refers to the density reduction rate calculated from the amount of reflected light before and after rubbing an output image of a certain density and rubbing it with a constant load.

Second Embodiment The image forming apparatus is similar to that of the first embodiment and has no page memory.

Control of fixing heater: After the copy button is pressed, the scanner unit operates and the image signal is input from the CCD 61. The input image signal is subjected to image processing by the image processing device 63 shown in FIG. The output image density detection device 71 detects the density of the image signal subjected to the image processing.

Here, after the image signal is recorded in advance as an electrostatic latent image on the surface of the rotary photosensitive drum 39,
A time t1 is set until the image is visualized by the developing device 31, transferred to the sheet p, and enters the fixing device. Further, the temperature of the fixing device causes a delay of time t2 from when the control signal is sent to the heater until it responds. In consideration of these, the temperature of the fixing heater is controlled by delaying the emission of the semiconductor laser by the time (t1-t2). By doing so, the image density and the fixing temperature when fixing the image can be matched well.

The relationship between the control temperature and the image density is the same as that shown in the first embodiment.

With the configuration of this embodiment, even in an image forming apparatus having no page memory, it is possible to sequentially change the temperature control by appropriately controlling the fixing heater.

Example 3 1) Example of image forming apparatus The example is substantially the same as that of Example 1, but the structure of the fixing heater is different.

2) Structure of Fixing Device The structure of the heating element in the fixing device of the first embodiment is changed as follows.

FIG. 10 is a schematic view showing the layer structure of the heater 1, and is shown as a perspective view in which the lower surface side of the heating element is directed upward and one longitudinal end side thereof is cut out.

The heater 1 of this example comprises a base 101 made of a heat-resistant and electrically insulating base material such as alumina, and a grace layer 102 made of a heat insulating material such as glass formed on the upper surface of the base 101. A resistance heating element layer 103 made of Ta2N or the like formed on the upper surface thereof, and separation electrodes 104A, 104B, 104C made of a conductive material such as Ag arranged so as to generate heat by dividing the resistance heating element layer in the longitudinal direction. And the common electrode 105, the resistance heating layer 103 and the electrode 104.
A sliding protection layer 106 formed of a heat-resistant and wear-resistant material such as Ta105 formed on the upper surface of 105.

FIG. 11 is a block diagram showing the constitution of the electric heating control. With such a configuration, a minute portion between the divided electrode and the common electrode generates heat, so that the entire heater functions as a set of minute resistance heating portions.

In this embodiment, the density of the heating element is set to 200.
Create a heater so that it becomes dpi.

3) Control Method of Fixing Heating Section As shown in FIG. 11, a control signal generating device 72 is required to control the fixing temperature to an appropriate fixing temperature according to the image signal taken into the page memory 64. This determines the fixing temperature according to the density of the area corresponding to each heat generating layer of the image,
It is a device that generates a signal that can obtain a voltage amount for controlling at that temperature. The average density of two pixels (corresponding to two pixels for one heater because the recording pixel density is 400 dpi and the heater density is 200 dpi) and the fixing temperature are shown in a table as shown in FIG. 7, for example. Remember. A voltage is supplied from the voltage applying device 73 to each heating element so that the temperature becomes based on this table, and control is performed. The control timing and the like are the same as in the first embodiment.

By adopting the configuration of this embodiment, the fixing temperature can be two-dimensionally controlled in the longitudinal direction and the paper feeding direction, so that the fixing can be performed more efficiently.

[0046]

According to the present invention, the temperature control temperature is varied depending on the image density in one image, and the temperature control temperature is raised as the density becomes low and it becomes difficult to fix the image. Accordingly, it is possible to perform efficient fixing. As a result, it is possible to realize an image forming apparatus that has many merits such that fixability can be satisfied at all densities, temperature rise can be suppressed, and power consumption can be reduced. In addition, the heat resistance of the entire system can be improved by suppressing the temperature rise of the heater, the fixing device and the periphery thereof.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an image forming apparatus according to first, second, and third embodiments of the present invention.

FIG. 2 is a side sectional view of a fixing device in the image forming apparatus according to the first exemplary embodiment of the present invention.

FIG. 3 is a side sectional view of the fixing heater according to the first exemplary embodiment of the present invention.

FIG. 4 is a block diagram showing the flow of image signals and control signals in the image forming apparatus according to the first embodiment of the present invention.

FIG. 5 is a diagram showing a relationship between a laser output signal and a heater controlled temperature when passing through a fixing nip portion in Embodiment 1 according to the present invention.

FIG. 6 is a diagram showing a relationship between a laser output signal and an output image density in Examples 1, 2, and 3 according to the present invention.

FIG. 7 is a conversion table diagram of a laser output signal and a temperature control temperature in Examples 1, 2, and 3 according to the present invention.

FIG. 8 is a diagram showing a relationship between a laser output signal and fixability in Example 1 according to the present invention.

FIG. 9 is a block diagram showing the flow of image signals and control signals in the image forming apparatus according to the second embodiment of the present invention.

FIG. 10 is a schematic diagram of a fixing heating body in an image forming apparatus according to a third exemplary embodiment of the present invention.

FIG. 11 is a block diagram showing the flow of image signals and control signals in the image forming apparatus according to the third embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Heater 2 ... Substrate 3 ... Exothermic layer 4 ... Protective layer 5 ... Thermistor 6 ... Fixing film 7 ... Driving roller 8 ... Followed roller 9 ... Pressure roller 10 ... Entrance guide 11 ... Heater support 12 ... Paper ejection guide 19 ... Document 20 ... Platen glass 21 ... Light source 22 ... Reflector 23-28 ... Mirror 29 ... Imaging lens 30 ... Primary charger 31 ... Developing device 32 ... Developing roller 34 ... Transfer charger 35 ... Eliminating needle 36 ... Cleaning device 37 ... Cleaning blade 38 ... Conveying part 39 ... Photosensitive drum 40 ... Polygon mirror 41 ... Fθ lens 61 ... CCD 62 ... A / D converter 63 ... Image processing device 64 ... Page memory 65 ... D / A converter 66 ... LD Driver 67 ... Semiconductor laser 68 ... Halftone area detection device 69 ... MPU 70 ... Operation unit 71 ... Output image density detection device 2 ... control signal generator 73 ... voltage application device 101 ... substrate 102 ... glaze layer 103 ... the resistance heating layer 104 ... split electrodes 105 ... common electrode 106 ... sliding protective layer

Claims (5)

[Claims] 1. An image forming means for forming a non-fixed toner image corresponding to target image information by carrying a toner made of a heat-meltable resin or the like on a recording material surface, a fixing film, and the fixing film. Running drive means, a heating body disposed on one side of the fixing film with the fixing film as a center, and an unfixed toner of a recording material disposed on the other side of the fixing film via the fixing film. A fixing film which is provided with a pressure member for bringing the surface on the image carrying side into close contact, and which is driven to run in the same direction at the same speed as the carrying speed of the recording material carrying the unfixed toner image carried from the image forming means side; A toner image heating and fixing unit that introduces the recording material between the pressure member and the image fixing member to heat and fix the unfixed toner image on the surface of the recording material. On the contact surface side with the film Wearing film transverse has a heating unit for the longitudinal, having electric heating control means for heating to vary in accordance with the output image information controlled temperature of the heat generating portion, the image forming apparatus characterized by. 2. The image forming apparatus according to claim 1, further comprising an output image detecting unit. 3. The image forming apparatus according to claim 1, wherein the position, density, etc. of the output image are detected, and the fixing temperature control temperature is adjusted within one image according to the output image density distribution. An image forming apparatus characterized by changing and controlling. 4. The image forming apparatus according to claim 1, 2 or 3, wherein the temperature control temperature for fixing in one image is increased in a region having a lower density, while the temperature in a solid white part is higher. An image forming apparatus having a low temperature control. 5. The image forming apparatus according to claim 1, wherein the fixing heat generating portion is a collective constitution of fine resistance heat generating portions arranged in a longitudinal direction, and the heat generating heat is generated. An image forming apparatus comprising: an energization heat generation control unit that energizes in a pulse shape for each individual fine resistance heating unit to selectively generate heat.