JPH03166578A - Fixing device - Google Patents

Abstract

PURPOSE:To shorten a useless heating time before fixation processing by detecting the temperature of a heating body before preliminary heating and changing total energy at the time of preliminary heating in accordance with the detected temperature. CONSTITUTION:The relation between the temperature of the heating body 20 and the time necessary for raising the temperature to 180 deg.C, for example, is provided in a ROM table. As soon as a start switch is turned on, the detected temperature concerning the heating body of a thermometric element 23 is read by a microcomputer and preliminary heating energization start time is changed according to the tempera ture, so that the heating body is always allowed to be at the fixation-enabled tempera ture 180 deg.C 0.5 seconds before a fixation processing stage. Namely, when the highest temperature in use is 37 deg.C, the preliminary heating is started one second after the start switch is turned on. A short time after performing image formation, that means, in the case that the image formation is started again before the temperature of the heating body 20 falls to a room temperature, the preliminary heating is started two seconds after starting the image formation when the temperature of the heating body 20 is, for example, 74 deg.C. Thus, the consumption of energy caused by the useless heating before the fixation processing is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fixing device that applies thermal energy to an image carrier (recording material) via a film. This device can be used as a copier, a laser beam printer, a facsimile, a microfilm league printer, or an image display (
(display) device ● In an image forming device such as a recorder, a recording material as an image carrier is produced using a toner made of heat-meltable resin, etc. by an appropriate image forming process means such as electrophotography, electrostatic recording, or magnetic recording. Form an unfixed toner image corresponding to the desired image information on the surface of (electrofax sheet, electrostatic recording sheet, transfer material sheet, printing paper, etc.) directly or indirectly (transfer). carry it,
It can be used as an image fixing device that heats and fixes the unfixed toner image as a permanently fixed image on the surface of the recording material carrying the image. Further, the present invention is not limited to an image fixing device, and can be used as a device for heat-treating a wide variety of image carriers, such as a device that heats a recording material carrying an image to modify its surface properties. (Prior Art) Conventionally, a heating device for a recording material, for example, for heat-fixing an image, includes a heating roller maintained at a predetermined temperature, and a pressure roller having an elastic layer and pressed against the heating roller. By,
A heated roller system that heats the recording material while supporting it is often used. A belt fixing system is also known as an image fixing means, as disclosed in US Pat. No. 3,5711,797. This is done by: (1) Bringing the toner image into contact with a heating body web and heating it to its melting point to melt it; (2) After melting, the toner is cooled to a relatively high viscosity; (2) The toner image is heated while reducing its tendency to stick. This method allows the adhesive to be fixed without causing offset by peeling it off from the body web. There are also flash fixing methods and oven fixing methods. Recently, a heating device W (film heating method) has been devised that consists of a fixedly supported heating body, a film that is pressed against the heating body, and a pressure member that heats the recording material through the film. There is.

The system device disclosed in Japanese Unexamined Patent Publication No. 63-313182, which was previously proposed by the present applicant, belongs to this category, and an unfixed toner image is transferred through a thin heat-resistant film (sheet) that slides in pressure contact with a fixed heating element. Heat energy is applied to soften and melt the film to separate the recording material, or the toner cools and melts.
This is a heating means/device that basically separates the film and recording material after solidification.

(Problems to be Solved by the Invention) However, the conventional heat roller method described above, the belt fixing method described in U.S. Pat. No. 3,578,797, and other methods have the following problems. there were.

Heat roller method: ■It takes a considerable amount of time to reach the specified temperature, during which time image formation is prohibited.
FHJ has a so-called wait time. ■Because it requires heat capacity, a large amount of electricity is required. ■A special heat-resistant bearing is required because the roller temperature is high for rotating rollers. ■The rollers are in direct contact with the hands, which may be dangerous and require protective materials. ■Depending on the fixing temperature and curvature of the roller, the recording material wraps around the roller, making it easy to see recording material jams. ■Because the temperature at the fixing point where the toner is fixed on the recording material is equal to the temperature at the separation point between the recording material and the heat roller, high-temperature offset that depends on the separation temperature is likely to occur, and image glossiness that depends on the separation temperature is likely to occur. The degree cannot be controlled. Flash, oven fixing method: ■The device becomes larger.
■There is a risk of fire if the sharpness of the image deteriorates or if the recording paper stays in the fuser. Belt fixing method: This method also has the same problems as the above-mentioned heat roller method, such as wait time and large power consumption. The film heating method can: ■ Save power by using a low heat capacity heating element; Shorten wait time (quick start); ■ Prevent offset because the fixing point and separation point can be set separately. It is effective and has the advantage of being able to solve various other drawbacks of conventional examples. In film heating type fixing devices, in order to reduce the maximum fixing energy, the heating element is preheated for several seconds from the start of image processing until the transfer material sheet as an image carrier enters the fixing device. ). The energy applied for this preheating is set so that the temperature of the heating element rises to the fixing processing temperature by the time it enters the transfer material sheet at the lowest ambient temperature in which the apparatus is used. However, when the ambient temperature is high, or when forming an image again after a short period of time,
Since the heating element is already at a high temperature at the start, it reaches the fixing temperature earlier than the transfer material sheet enters. This is a waste of energy and causes heating of the image or equipment, which adversely affects image quality. In addition, problems such as fixing film, reducing the durability of fixing device parts such as pressure rollers and bearings occur. The present invention relates to a film heating type fixing device, and aims to solve the above-mentioned problems with this device. (Means for Solving the Problems) The present invention provides a fixing device that brings a heating body into close contact with one side of a film and an image carrier on the other side, and applies thermal energy to the image carrier through the film. The fixing device is characterized in that the total energy applied during preheating of the heating element is changed according to the detected temperature of the heating element. The changes in the total energy mentioned above include changing the preheating start time, preheating applied energy (applied power), etc. by phase control (changing the AC phase angle), PWM control (pulse width control), FM control (frequency control) It can be changed by the following methods. (Function) That is, the present invention detects the temperature of the heating element before preheating (preheating), and changes the total energy given to the heating element during preheating according to the detected temperature, thereby performing the fixing process on the fixing device. The heating element is heated to a temperature suitable for fixing immediately before or at the same time as the image bearing member enters. This makes it possible to reduce wasted heating time before the fixing process, thereby achieving effects such as energy reduction, prevention of excessive temperature rise in the image forming apparatus, and improved durability of fixing apparatus parts. (Embodiments) (1) Configuration example of fixing device (Figs. 1 and 2) Fig. 1 shows a schematic configuration of an example of a film heating type fixing device 1l according to the present invention. Reference numeral 25 designates an endless belt-shaped fixing film, which includes a driving roller 26 on the left side, a driven roller 27 on the right side, and a low heat capacity linear film as a heating element fixedly supported below between both rollers 26 and 27. Heating body 20
and a guide roller 2 disposed below the drive roller 26.
6a, the four members parallel to each other 26●27●20●2
A suspension is installed between 6a. The slave roller 27 is an endless belt-shaped fixing film 2.
The fixing film 25 also serves as a tension roller 5, and the fixing film 25 is rotated clockwise at a predetermined circumferential speed as the drive roller 26 rotates clockwise. It is rotated at the same circumferential speed as the conveyance speed of the transfer material sheet P as an image carrier carrying the toner image Ta on its upper surface without wrinkling, meandering, or speed delay. A pressure roller 28 serves as a pressure member and has a rubber elastic layer such as silicone rubber with good mold releasability. The lower surface is pressed against the lower surface with a total contact pressure of, for example, 4 to 7 kg, and is rotated counterclockwise in the forward direction in the conveyance direction of the transfer material sheet P. Endless belt-shaped fixing film 25 that is rotatably driven
Because it is repeatedly used to heat and fix toner images, it has excellent heat resistance, release properties, and durability, and generally has a life of 100 ILm.
Hereinafter, it is preferable to use a thin one with a thickness of 50 gauze or less. For example, polyimide ● polyetherimide ● PES -
A single layer film of a heat-resistant resin such as PFA (tetrafluoroethylene perfluoroalkyl vinyl ether copolymer resin) or a composite layer film, such as a 20ILm thick film, is coated with PTFE (tetrafluoroethylene resin) on at least the image contact side. ) A releasable coat e made by adding a conductive material to a fluororesin such as PAF is applied to a thickness of 10 pm. The linear heating element 20 with a low heat capacity as a heating element is made of wood and has horizontally long rigidity, high heat resistance, and heat insulation properties, with the eldest being in the transverse direction of the fixing film (direction perpendicular to the running direction of the fixing film 25). A heater support 24, and a temperature measuring element 23 as a means for detecting the temperature of the heating element 22 and the heating element 20, which are attached to and held on the lower surface of the support along the longitudinal length of the lower surface, are provided. It has a heater board 2l. The heater support 24 ensures the overall strength of the heating body 20, and is made of, for example, PPS (polyphenylene sulfide).
．． FAI (polyamideimide), PI (polyimide).
It can be constructed from highly heat-resistant resins such as PEEK (polyether-ether-ketone) and liquid crystal polymers, as well as composite materials of these resins and ceramics, metals, glasses, etc. For example, the heater substrate 21 has a thickness of l. It is an alumina substrate with a width of 10 mm and a length of 240 mm. The heating element 22 is, for example, a linear or band-shaped material formed by coating (by screen printing, etc.) an electrically resistive material such as Ta2N to a width of 1.0 mm along the length of the bottom surface of the substrate 21 approximately in the center. It is a current-carrying heating element with low heat capacity. The temperature measuring element 23 is, for example, a low temperature sensor such as PTL, which is coated along the longitudinal direction (by screen printing, etc.) approximately in the center of the upper surface of the substrate 21 (the surface opposite to the side on which the heating element 22 is provided). It is a resistance temperature detector with heat capacity. In this example, the temperature of the substrate 2l is detected as the temperature of the heating element 20 by the temperature measuring element 23. In the case of a wooden example, electricity is applied to the linear or band-shaped heating element 22 from both ends of its length to generate heat over the entire length of the heating element 22. Energization is DCioov cycle 2 0
The temperature of the heating element is controlled to 180'C by changing the width of the applied pulse while detecting the temperature of the heating element using a yasec pulse waveform using the thermometer 23. The fixing film 25 is not limited to an endless belt shape.
As shown in the figure, the fixed end fixing film 25 wound in a roll around the feed-out shaft 3o is passed between the heating body 20 and the pressure roller 28 and under the guide roller 26a to the take-up shaft 3l.
It may also be an a-configuration in which the transfer material sheet P is stopped at the feed shaft 30 side and travels from the take-up shaft 31 side at the same speed as the conveyance speed of the transfer material sheet P. (2) Fixing Execution Operation The image forming apparatus performs an image forming operation in response to the image forming start signal, and the transfer material sheet P conveyed from the transfer section (8) side to the fixing device l1 is guided by the guide 29 and heated at 180°C. The pressure contact portion N between the heating body 20 and the pressure roller 28 whose temperature is controlled to
The fixing film 25 enters between the fixing sheet 25 and the pressure roller 28 in the fixing nip section), and the unfixed toner image surface is moving in the same direction at the same speed as the conveyance speed of the sheet P.
The film passes through the fixing nip N between the heating body 20 and the pressure roller 28 while being subjected to a clamping force while being in close contact with the lower surface of the fixing film 24 and in an overlapping state together with the fixing film 24 without causing surface deviation or wrinkles. W is the width of the heating element 22 provided on the lower surface of the heating element, and the heating element 22 is within the width of the mutual pressure contact area between the lower surface of the heating element 20 and the upper surface of the pressure roller 28, that is, the width of the fixing nip N. Exists within the area. The toner image bearing surface of the sheet P receives heat from the heating element 22 via the fixing film 25 while passing through the fixing nip N while being in close contact with the fixing film surface, and the toner image is melted at a high temperature. Soft adhesive Tb is applied to the sheet P surface. In the case of a wood sample device, the recording material sheet P and the fixing film 2
Separation from the sheet 5 is performed at the time the sheet P passes through the fixing nip N and comes out. At this point of separation, toner T
The temperature of b is still higher than the glass transition point of the toner, and therefore, the bonding force (adhesive force) between sheet P and the fixing film 25 at this point of separation is small, so sheet P is directed toward the surface of the fixing film 25. There is almost no toner offset, and the sheet P is always separated smoothly without being stuck to the surface of the fixing film 25 due to poor separation and wrapping around and jamming. Since the toner Tb, which is at a temperature higher than the glass transition point, has appropriate rubber properties, the toner image surface upon separation does not follow the surface of the fixing film, but has an appropriate unevenness. Since the toner is maintained and cooled to solidify, excessive image gloss does not occur on the fixed toner image surface, resulting in high quality images. The sheet P separated from the fixing film 25 is guided by the guide 35 and while reaching the pair of paper ejection rollers (36), the temperature of the toner Tb, which is higher than the glass transition point, naturally cools down (natural cooling).
The temperature reaches a temperature below the glass transition point and solidifies Tc, and the image-fixed sheet P is output onto the tray.
(3) Preheating control of heating element■. Control example 1 (Figure 3) Figure 3 shows a heating element with a heating element of 5°C at the minimum operating temperature of this device.
These are the results of measuring the temperature rise characteristics of the heating element when a power of W was applied. The image forming apparatus used takes 5.5 seconds from when the start switch is turned on until the transfer material sheet enters the fixing device, and the 5°C heating element rises to the fixing temperature of 180°C in about 5 seconds. When the temperature of the body is 5°C, the fixing process can be performed by energizing the heating element 22 at 350 W almost at the same time as the start switch is turned on. Also, from Figure 3, for example, the heating element at 37°C takes about 4 seconds,
It can also be seen that the heating element at 74°C reaches 1806°C in about 3 seconds. In the wooden example, the relationship between the temperature of the heating element and the time required to raise the temperature to 180"C is set in the ROM table, and at the same time as the start switch is turned on, the temperature detected by the temperature detection element 23 on the heating element is set by the microcomputer. By changing the preheating energization start time according to the temperature, the heating element always reaches the fixing temperature of 180"C 0.5 seconds before the fixing process. That is, when the maximum operating temperature is 37°C, preheating starts 1 second after the start switch is turned on. In addition, when image formation is started again after a short time after image formation, that is, before the heating element has cooled down to room temperature, for example, if the heating element is 746C, preheating is started 2 seconds after the start. ．． This makes it possible to reduce energy consumption due to unnecessary heating before the fixing process, and to reduce the temperature rise within the 4LI. Additionally, the durability of the fixing film, pressure roller, bearings, etc. can be improved. ■． Control Example 2 (Figure 4) In this control example, the energy applied to the heating element is changed according to the heating element temperature without changing the preheating time, so that the heating element always reaches the fixing temperature immediately before the start of the fixing process. It was designed to reach . For example, as shown in Figure 4, the heating element at 40°C is heated to 300°C.
The temperature was raised to 180°C by applying a power of W for 5 seconds. 80"C heating element is 18" when energized at 250W for 5 seconds
Raise the temperature to 0@C. In this example, the temperature of the heating element and
The energy required to raise the temperature to 180°C by applying electricity for 5 seconds is determined by experiment, and the result is set on the ROM table, the temperature of the heating element is detected when the image forming star is turned on, and the microcomputer is controlled according to the temperature. The system is designed to provide energy that always reaches the heating element temperature of 180°C after 5 seconds. As a result, in addition to the same effect as control example 1 described above, the total maximum energy application time is reduced, so
It has the effect of improving the durability of electrical elements, etc. ■． Control example 3 (Fig. 5) In control examples 1 and 2 above, taking into account the delay in conveyance of the transfer material sheet, etc., the transfer material sheet enters the fixing device.
．． The heating element was allowed to reach the fixing processing temperature (180°C) 5 seconds before the test. The apparatus of this embodiment is capable of conveying the transfer material sheet with high precision, and therefore, as shown in FIG. It is set to . According to experiments, by doing this, the temperature measuring element 2
The so-called overshoot phenomenon, where the heating element exceeds 180@c due to the detection delay of 3, etc., has been reduced. This can reduce heat damage to the base material of the fixing film and the PTFE coating material on the surface layer. The present invention is more effective in a method in which the heating element is turned off for each paper interval when image formation is performed continuously, since the temperature of the heating element has not dropped sufficiently after the heating element is turned off. (4) Example of image forming apparatus (FIG. 6) FIG. 6 shows a schematic configuration of an example of an image forming apparatus incorporating the fixing device 11 according to the present invention. The image forming apparatus in this example is an electrophotographic copying apparatus of a reciprocating document table type, a rotating drum type, and a transfer type. Reference numeral 100 denotes a device housing, and l designates a reciprocating type original document mounting table made of a transparent plate member such as a glass plate, which is disposed on the top plate 100a of the device housing. It is driven to reciprocate to the right a and to the left a' at predetermined speeds. G is a document, which is placed by placing the image side to be copied facing down on the top surface of the document table l according to a predetermined placement standard, and placing the document pressure bonding plate 1a on top of it and pressing it down. ．． Reference numeral 100b denotes a slit opening, which serves as a document illumination section, and is opened on the surface of the top plate 100a of the machine casing, with its length extending in a direction perpendicular to the reciprocating direction of the document storage table l (direction perpendicular to the plane of the paper). The downward image surface of the original G placed on the original placing table l passes through the position of the slit opening ioob sequentially from the right side to the left side during the forward movement of the original placing table 1 to the right side a. During the passage of the document, the light L from the lamp 7 is received through the slit opening 100b and the transparent original table 1, and the document is illuminated and scanned. The illumination scanning light reflected from the document surface is image-formed and exposed on the surface of the photosensitive drum 3 by the short-focus small-diameter imaging element array 2. The photosensitive drum 3 is coated with a photosensitive layer such as, for example, a zinc oxide photosensitive layer or an organic semiconductor photosensitive layer, and is driven to rotate clockwise as indicated by an arrow b around a central support shaft 3a at a predetermined circumferential speed. The surface of the photosensitive drum 3 is uniformly charged with positive or negative polarity by the charger 4, and the image-forming exposure (slit exposure) of the original image is applied to the uniformly-charged surface of the photosensitive drum 3. Electrostatic latent images corresponding to the original image are sequentially formed. This electrostatic latent image is sequentially developed by a developing device 5 using a toner made of a resin etc. that is softened and melted by heating, and the developed toner image is transferred to a location where a transfer discharger 8 is provided as a transfer section. It will transition. S is a cassette in which transfer material sheets P as recording materials are loaded and stored, and the sheets in the cassette are fed and fed one by one by the rotation of the feeding roller 6, and then the sheets on the drum 3 are fed by the registration roller 9. When the leading edge of the toner image forming section reaches the transfer discharger 8, the leading edge of the transfer material sheet P also reaches the position between the transfer discharger 8 and the photosensitive drum 3, and the timing is adjusted so that they coincide. and is fed synchronously. The toner images on the photosensitive drum 3 are sequentially transferred onto the surface of the fed sheet by the transfer discharger 8. The sheet to which the toner image has been transferred in the transfer section is sequentially separated from the three surfaces of the photosensitive drum by a separating means (not shown) and transferred to the conveying device 1.
0, the unfixed toner image Ta carried thereon is guided to the aforementioned fixing device 11 and subjected to heat-fixing processing, and is transferred as an image-formed product (copy) through a guide 35 and an ejection roller 36 to a paper ejection tray 12 outside the machine. It is discharged to the top. The surface of the photosensitive drum 3 after image transfer is cleaned by a cleaning device l3.
After removing residual contaminants such as residual toner, it is used repeatedly to form images. (Effects of the Invention) As described above, the present invention detects the heating element temperature before preheating in a film heating type fixing device, and changes the total energy during preheating according to the detected temperature. This makes it possible to reduce wasted heating time before the fixing process, resulting in effects such as energy reduction, reduced temperature rise of the image forming device, and improved durability of fixing device parts.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an example of a film heating type fixing device according to the present invention. Figure 2 is the same diagram as above for another example of the device. Figures 3 to 5 are examples of control temperature graphs for preheating control examples 1 to 3. FIG. 6 is a schematic configuration diagram of an example of an image forming apparatus. 3 is a photosensitive drum, P is a transfer material sheet as an image carrier, 1l is a fixing member 1
1 20 is a heating element, 22 is a heating element, 23 is a temperature measuring element (heating element temperature detection means), 28 is a pressure roller.

Claims (3)

[Claims] (1) A fixing device that attaches a heating body to one side of the film and an image carrier to the other side of the film, and applies thermal energy to the image carrier through the film, depending on the temperature detected by the heating body. A fixing device characterized in that the total energy applied during preheating of the heating element is changed. (2) The fixing device according to claim 1, wherein the total energy is changed by changing the preheating start time. (3) The fixing device according to claim 1, wherein the total energy is changed by changing the preheating applied energy.