JPH02131272A - Image forming device - Google Patents

Abstract

PURPOSE:To improve the durability of the heat generating body of a toner image heating and fixing means and to simplify a driving system and reduce its size by providing the heat generating body with a linear heat generation part in the lateral direction of a fixation film and bringing the fixation film into contact with at least a pressure member over the overall-length area. CONSTITUTION:The fixation film 23 contacts a pressure roller 22 over the entire-length area. Namely, the pressure roller 22 contacts the heat generating body 21 across the fixation film 23 and there is no part which contacts the heat generating body directly. The rubbing wear and damage of the part of the heat generation surface 28 of the heat generation body with the pressure roller 22 are prevented. Consequently, the durability of the heat generation body 21 is improved and there is no large frictional resistance generated at the direct contacting part to reduce the rotary driving torque of the pressure roller 22, thereby simplify the driving system of a fixation device 20.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to image forming apparatuses such as copying machines, laser beam printers, facsimile machines, microfilm reader printers, image display devices, and recording machines.

For more details, see Electronic Photography/D? The surface of a recording material (electrofax sheet, electrostatic recording sheet, transfer material sheet, printing paper, etc.) is printed using a toner made of heat-meltable resin or the like by an appropriate image forming process such as f-recording or magnetic recording. An unfixed toner image corresponding to the desired image information is formed and supported on the surface of the recording material using a direct method or an indirect (transfer) method, and the unfixed toner image is heated as a permanently fixed image on the surface of the recording material carrying the image. The present invention relates to an image forming apparatus that performs fixing processing.

(Prior Art) Conventionally, a fixing device used in this type of device uses a heating roller maintained at a predetermined temperature and a pressure roller having an elastic layer and in pressure contact with the heating roller. A roller fixing method is often used in which a recording material on which a toner image has been formed is heated while being supported and conveyed.

However, in this type of device, in order to prevent the so-called offset phenomenon in which toner is transferred to the heating roller, it is necessary to maintain the heating roller at an optimal temperature, and the thermal capacity of the heating roller or heating element must be increased. did not become. That is, when the heat capacity of the heating roller is small, the temperature of the heating roller tends to fluctuate greatly toward a lower temperature side or a higher temperature side due to paper passing or other external factors due to the relationship with the amount of heat supplied by the heating element. If the temperature changes to the low temperature side, the toner softens and melts insufficiently, resulting in poor fixing or low-temperature offset. If the temperature changes to the high temperature side, the toner completely melts and the cohesive force of the toner decreases. ,
Causes high temperature offset.

In order to avoid this problem, increasing the heat capacity of the heating roller increases the time it takes to heat the heating roller to a predetermined temperature, causing another problem of increasing standby time when using the device. .

As a measure to solve this problem, US Patent No. 3,578
, No. 797, (1) bringing the toner image into contact with a heating body web and heating it to its melting point to melt it, (2) cooling the toner after melting to give it a relatively high viscosity, and (2) making the toner image relatively high in viscosity. A method is known in which fixation is achieved without causing offset by going through the process of peeling off the heating element web in a state where the tendency to adhere is weakened.

In addition, the above-mentioned known method heats the toner image and recording material without applying pressure to the heating body, so there is no need to heat the recording material, compared to other methods. The company says it can melt toner using much less energy.

However, as is well known, when the toner is brought into contact with a heating body without being pressurized, the heat transfer efficiency decreases and it takes a relatively long time to heat and melt the toner.

Therefore, Japanese Patent Publication No. 51-29825 (Special Patent Application No. 47-25)
No. 896), it has been proposed that a known pressure welding technique be added to this to improve the heat transfer coefficient and to sufficiently heat and melt the toner in a short time.

(Problems to be Solved by the Invention) However, in the apparatus disclosed in this publication, in order to heat the toner sufficiently in a relatively short time, ■ Toner images and records are formed between a pair of heating elements. Since the method uses a method in which the material is heated under pressure, and then the heating is stopped and then forcedly cooled, the energy required for fixing increases. In other words, by heating the toner image with a pair of heating elements, the toner image is heated from above and below, which may seem efficient at first glance, but on the other hand, in order to heat the toner image from the recording material side, the recording material must first be sufficiently heated. This requires a large amount of energy. Furthermore, in the cooling process, the recording material that has been heated and humidified when heating the toner image cannot be separated unless it is cooled.
A forced cooling method is required, resulting in a large waste of energy.

As described above, a method has been proposed in which the heated toner is cooled and then separated to fix the toner without causing high-temperature offset, but it has not been put to practical use because of the drawbacks described above.

In the above two proposed examples, the heating body is composed of a heating roller, the web fed by the heating roller, and a heat generation source built into the heating roller, heating is performed via the web, and it functions as a web conveyance roller. are doing. For this reason, the method of supplying power to the heat generating source and the form of abutting support for the temperature sensing element become complicated, and the temperature control tends to be difficult.

Furthermore, in the configuration in which the temperature sensing element slides with the heating roller, there are safety problems such as excessive temperature rise due to wire breakage.

Moreover, since both of the above two examples require a heating element with a relatively large heat capacity, there is also the disadvantage that heat radiation into the machine increases and the temperature inside the machine increases significantly.

The present invention solves the problems of the conventional apparatus described above, and makes it possible to reduce the heat capacity of the heating element without causing fixing failure or offset. As a result, standby time, power consumption, and It is an object of the present invention to provide an image forming apparatus that causes a small temperature rise inside the machine and has other remarkable features.

(Means for Solving the Problems) The present invention provides an image forming means that forms an unfixed toner image covering target image information by carrying toner made of heat-melting resin or the like on the surface of a recording material. , a fixing film, a traveling drive means for the fixing film, a heating body disposed on one side of the fixing film with the fixing film inside, and a heating body disposed on the other side of the fixing film for moving the fixing film with respect to the heating body. a pressure member that brings the unfixed toner image bearing side of the recording material into close contact with each other through the pressurizing member, and presses the unfixed toner image bearing surface of the recording material into close contact with each other, and the pressurizing member is provided with a pressure member that brings the unfixed toner image bearing side of the recording material into close contact with each other. a toner image heat fixing means for introducing the recording material between the fixing film driven to run and the pressure member and heating and fixing the unfixed toner image on the surface of the recording material; The image forming apparatus is characterized in that the heating body of the heat fixing means has a linear heating section in the transverse direction of the fixing film, and the fixing film is in contact with at least the entire length of the pressure member.

(Function) (1) The recording material to which the image is to be fixed is introduced between the fixing film and the pressure member, which are running in the same direction at the same speed as the conveyance direction of the recording material. When the image bearing side surface is in close contact with the fixing film and overlapped with the fixing film, the mutual pressure contact area (fixing nip area) between the heating body and the pressure member is subjected to squeezing pressure, and the surfaces may be misaligned due to the speed difference between them. They overlap and fit together as one piece without any wrinkles or wrinkles.

■Heating process During this process of passing through the mutual pressure contact section, the unfixed toner image on the surface of the recording material is heated and softened and melted by the heating body via the fixing film, and in particular, the surface layer part is completely softened and melted by increasing the toner melting point. melt. In this case, the heating body, fixing film, toner image, etc.
The recording material is well pressed and adhered by the pressure member and heat is transferred effectively, so that the toner is sufficiently softened and melted by heating for a short period of time, and good fixing properties can be obtained. On the other hand, the temperature rise of the recording material itself is actually extremely small and there is little waste of thermal energy. In other words, the recording material itself is not heated substantially, only the toner is effectively heated to soften and melt, and the toner image can be successfully heat-fixed with low power.

Here, a note will be made regarding the softening and melting of the toner described in the present invention. The temperature conveniently expressed as the toner's "melting point" refers to the minimum temperature required for the toner to fix. In some cases, the viscosity decreases to such an extent. Therefore, even when it is conveniently expressed as melting when determining the name, it may actually indicate a decrease in viscosity to the extent of softening. The present invention also includes such cases. Similarly, even when it is conveniently expressed that the toner has been cooled and fixed, depending on the toner, it may be more appropriate to say that the toner has become highly viscous rather than assimilated. The present invention also includes such cases.

■Cooling process The toner image that is in close contact with the fixing film and sequentially passes through the mutual pressure contact area between the heating body and the pressure member.The recording material portion that has already been heated and softened and melted is kept in close contact with the fixing film surface even after passing through the pressure contact area. The conveyance is continued for a while, and this period is used as a cooling process, in which the heat of the toner softened and melted in the heating process is radiated, and the toner is cooled and fixed. This cooling and solidification greatly increases the cohesive force of the toner, causing it to behave as a group, and while the adhesion and fixing force to the recording material side increases, the cohesive force to the fixing film side extremely decreases. For the recording material, when the toner is heated and softened and melted in the heating process, it is pressurized by a pressure member, so at least a part of the toner image penetrates into the surface layer of the recording material, and the permeated portion is cooled. The anchor effect caused by solidification increases the adhesion and adhesion of the cooled and solidified toner to the recording material side.

After the toner image is cooled and solidified in the above-described cooling step, the recording material is sequentially separated from the fixing film surface. At this time of separation, the toner image is cooled and solidified, and the adhesion and adhesion force to the recording material is sufficiently large, but the adhesion and fixation force to the fixing film is extremely small, so the part of the recording material where the image has been fixed generates toner offset with respect to the fixing film. They are easily separated one after another without any problems.

In this way, the recording material on which the image is to be fixed is made to run in close contact with the fixing film at the same speed so that the unfixed toner image bearing surface faces the running fixing film surface, and the toner image is heated and melted by a heating body through the fixing film. Seriously, toner image. Since the recording material and the fixing film are separated after being cooled and fixed, toner offset with respect to the fixing film does not occur, and a heating element with a small heat capacity is used to supply power to the heating element with a simple configuration. The toner image can be efficiently heated by maintaining the heating element at a temperature sufficiently high relative to the temperature (melting point or softening point) at which the toner should be humidified in order to be fixed. This makes it possible to achieve sufficiently good fusing with less energy and no fusing defects, and as a result,
This has the effect of providing an image forming apparatus with less standby time during use, less power consumption, and less internal temperature rise.

(2) Since the fixing film is in contact with at least the entire length of the pressure member, the pressure member always comes into contact with the heating body through the fixing film and does not come into direct contact with the heating body. Therefore ■. When such a direct contact part exists, the durability (life) of the heating element can be improved by preventing the occurrence of friction wear and damage with the pressure member on the heat generating surface of the heating element corresponding to the part. will improve.

■． When there is a direct contact part, there is no large frictional force generated in that part, and when the pressure member is a rotating or rotationally driven member, the driving torque is reduced, simplifying and downsizing the drive system. As a result, it becomes possible to downsize and reduce the cost of the image forming apparatus.

(Example) <Example 1> (Figures 1 to 5) The apparatus of this example is an electrophotographic copying apparatus of a Haraaki mounting table reciprocating type, rotating drum type, and transfer type.

(1) Overall schematic configuration of the device (Fig. 1) In Fig. 1, 100 is a device housing, and 1 is a reciprocating motion consisting of a transparent plate member such as a glass plate disposed on the top plate 100a of the machine housing. It is a mounting table for the mold, and the top plate 100a of the machine casing is placed on the right side a in the drawing.
, are driven to reciprocate in the left direction 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 1 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 direction of reciprocating movement of the document table 1 (direction perpendicular to the plane of the paper). The downward image surface of the document G set on the document platform 1 passes through the position of the slit opening 100b sequentially from the right side to the left side during the forward movement of the document platform 1 to the right side a. During the passing process, the light Ll 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 imaged and exposed on the surface of the photosensitive drum 3 by the short focus and small diameter imaging element array 2.

The photosensitive drum 3 is coated with a photosensitive layer such as a zinc oxide photosensitive layer or an organic semiconductor photosensitive layer, and is rotated clockwise as indicated by an arrow b around a central support shaft 3a at a predetermined circumferential speed. The charger 4 uniformly charges the original with positive or negative polarity, and then the image-forming exposure (slit exposure) of the original image is carried out on the surface of the photosensitive drum 3. Electrostatic latent images corresponding to the images are sequentially formed.

This electrostatic latent image is sequentially visualized by a developing device 5 using toner made of a resin or the like that softens and melts when heated, and the developed toner image is transferred to a location where a transfer discharger 8 is provided as a transfer section. I will do it.

S is a cassette loaded with transfer material sheets P as recording materials, and the sheets in the cassette are fed and fed one by one by the rotation of the feeding roller 6, and are then fed onto the drum 3 by the registration roller 9. The timing is set so that when the leading edge of the toner image forming section reaches the position of 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 tram 3, so that they are aligned. The data is taken and fed synchronously. Then, the toner image on the photosensitive drum 3 side is 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 guided by a conveying kite 10 to a fixing device 20, which will be described later, to heat the unfixed toner image carried thereon. After undergoing a fixing process, the image is discharged onto a paper tray 11 outside the machine as an image-formed product (copy).

On the other hand, after the toner image has been transferred, the surface of the photosensitive drum 3 is subjected to removal of adhering contaminants such as residual toner by a cleaning device 12, exposed to light over the entire surface, subjected to charge removal by step 2, and electrical residual memory is erased repeatedly. Used for image formation.

PH1 is a paper feed detection sensor (for example, a photo sensor) disposed in the sheet bus portion between the feed roller 6 and the registration roller 9. PH2 is a discharge detection sensor (same as the same) disposed next to the fixing device 20.

(2) Fixing device 20 FIG. 2 is an enlarged view of a portion of the fixing device 20 in an image fixing state.

24 is a fixing film feeding shaft, on which the fixing film 23 of a desired set length is wound into a roll, and the leading end of the fixing film 23 is connected to the fixing film winding shaft 2.
It is locked at 7. The fixing film 23 in this embodiment is a thin plastic long film having a heat-resistant treatment and having a thickness of, for example, PET (polyester) as a base material.

21 and 22 are the upper surface fll+ and the lower surface n! of the fixing film portion between the shafts 24 and 27. [A heating body and a pressure roller are disposed facing each other.] The heating body 21 and the pressure roller 22 are constantly pressed with the fixing film 23 in between by a biasing means (not shown) to achieve a desired contact pressure (for example, a total pressure of 4 to
6Kg) is given. 26 and 33 are the heating elements 21
Next to the pressure roller 22, there are an upper separation roller and a lower separation roller having a large curvature (strong curvature, small radius), which are arranged to face the upper and lower surfaces of the fixing film, respectively. Reference numeral 32 denotes a guide plate disposed between the pressure roller 22 and the lower separation roller 33. They face each other substantially parallel to each other with a gap of , or are in slight contact with each other. The pressure roller 22 has an elastic layer made of silicone rubber or the like on a core made of metal or the like.

The upper separation roller 26 and the lower separation roller 33 are rollers that are free to rotate.

The winding shaft 27 is rotationally driven in the clockwise direction indicated by the arrow by a drive system (not shown), and as a result, the fixing film 23 is fed out from the lli[lI24 side to the winding IN 127 side to the image forming section (transfer section 8). from the fixing device 20 via the guide 10
It is wound up and run in the same direction at the same speed as the conveyance speed of the sheet P being conveyed to. The pressure roller 22 is rotationally driven in the counterclockwise direction of the arrow by a drive system (not shown) at a circumferential speed that is approximately the same as the transport speed of the sheet P.

Reference numeral 30 denotes a fixing film remaining amount sensor arm that is brought into contact with the outer surface of the rolled fixing film 23 on the feed-out shaft 24 side, and is used as the fixing film is sequentially transferred to the winding shaft 27 side by executing the fixing process. The remaining amount is detected from the gradual decrease in the roll diameter, and when the film is near the end, a warning display or sound is displayed to prompt the user to replace the fixing film.

The heating element 2l is a heat-resistant and electrically insulating base material such as alumina, or a composite member containing the same, and has a linear or strip-shaped heating surface (layer) made of Ta2N or the like on the lower surface of the base material.
28, and furthermore, for example, Ta205 is formed as a vibration protection layer on the surface thereof. The lower surface of the heating element 21 is smooth, and the front and rear ends are rounded to enable smooth sliding on the fixing film 23.

The heat generating surface 28 of the heating body has a small heat capacity, and the temperature is instantaneously raised to around 300° C. each time it is energized in a pulsed manner.

Reference numerals 29 and 25 are the same levers as the sheet detection sensors disposed on the lower surface side of the transfer material conveyance guide 10 from the toner image transfer section 8 to the fixing device 20 near the fixing device 20. In the free state, the tip of the lever 25 projects toward the body of the guide 10 through a through hole 10a provided in the guide 10. In this state, sensor 29 is off. Guide 1
The transfer material sheet P is conveyed from the transfer unit 8 side to the fixing device 20 side along the upper surface of the sheet P, and the protruding tip of the lever 25 is cut by the tip of the sheet P, so that the transfer material sheet P is transferred to the back side of the sheet P. It sinks into the through hole 10a and rotates. This lever 25
The sensor 29 is turned on by the downward rotation of the seat P, and a control circuit (not shown) detects whether the seat P has reached the sensor position. The lever 25 is pressed against the back surface of the seat P until the seat P passes through the lever position, so that the lever 25 is kept in a sunken and rotating state during that time, and the slave sensor 29 is kept in the on state. is retained. Thereafter, when the rear end of the seat P passes the position of the lever 25 and is separated from the lever 25, the lever 25 becomes free and returns to the position in which the tip protrudes from the through hole 10a again and rotates. . This return rotation turns off the sensor 29, and the control circuit detects that the seat P has passed the sensor position.

Figure 3 shows a heating element 21, a pressure roller 22, and a fixing film 2.
3. This is a dimensional relationship diagram of transfer paper P as recording paper, which will be described in detail in section (4) below.

(3) Operation After setting the original G on the original platen 1, setting the number of images to be formed, specifying the size of the sheet P to be used, specifying the magnification, etc., when the image forming start switch is pressed, The feeding of the sheet P in the cassette S is started by the feeding roller 6, and the feeding of the sheet P is detected by the sensor PH1. Also, image formation on the three surfaces of the photosensitive drum is started.

The fixing device 20 operates when a predetermined timer period elapses from the time when the sensor PH1 detects paper feeding, that is, when the sheet P fed from the cassette S is transferred to the registration roller pair 9, the transfer section 8, and the guide 1.
0 and the tip reaches a position near the pressure contact portion between the heating body 21 and the pressure roller 22. At the point in time when the time required has elapsed, the drive system of the fixing device starts rotating the winding shaft 27 and the pressure roller 22. A winding drive state is entered in which the fixing film 23 travels from the delivery shaft 24 side to the winding shaft 27 side at the same speed as the conveyance speed of the sheet P. Moreover, the heating surface 28 of the heating body 21
The sensor 29 and the lever 25 detect the leading and trailing ends of the conveying sheet P, thereby timing the transport sheet P and energizing it when necessary.

At this time, energization to the heat generating surface may be controlled by detecting the position of the sheet using a paper feed sensor or the like of the image forming apparatus.

Unfixed toner image T conveyed to fixing device 20 by L.
The heating body 21 is placed in an overlapping state with the fixing film 23, with the upper surface of the sheet supporting the fixing film 23 in close contact with the lower surface of the fixing film 23 in the running state, without causing any surface deviation or wrinkles.
It passes through the mutual pressure contact portion between the roller and the pressure roller 22 while being subjected to a squeezing force.

This process of passing through the mutual crimping part is referred to as the heating process (action).
The toner image is heated to soften and melt as described in (1) (1) above.

As mentioned above, the heating process in this embodiment is as follows:
This is accomplished by the heating element 21, which is provided with a linear heating surface 28 and configured to repeatedly generate heat by energizing the heating element 28 in a pulsed manner to the heating element 28, which is formed integrally with the heating element 21 and has a low heat capacity. That is, the toner image Ta on the sheet P conveyed at the conveyance speed Vp (lIIm/s) is sequentially transferred to the heat generating surface 28 of the heating body 21 along with the fixing film 23, which is conveyed without deviation according to the conveyance speed of the sheet P. Within the effective width of the linear heating section determined according to the width! It is fed into the tank and heated to become a softened and fused image Tb.

The sheet portion that has passed through the mutual pressure contact between the heating body 21 and the pressure roller 22 is spread between the heating body 21 and the upper separation roller 26 and travels forward until it reaches the position of the separation rollers 26 and 33. The fixing film continues to be conveyed while remaining in close contact with the fixing film portion. The guide plate 32 functions to support the back surface of the sheet P and maintain close contact with the fixing film 22.

Instead of the guide plate 32, a rotary guide belt is suspended around the pressure roller 22 and the lower separation roller 33, and this belt supports the back side of the sheet P to maintain close contact with the fixing film 23. It is also possible to do so.

This conveyance process is referred to as a cooling process, and as described in (1) (1) above (function), the heat of the softened and melted toner Tb is radiated, and the toner is cooled and solidified Tc.

When the fixing film 23 reaches the position of the separation upper roller pair 26, the traveling direction of the fixing film 23 is turned away from the sheet P surface along the surface of the heel upper roller 26, which has a large curvature, and the fixing film 23 and the sheet P The sheets are separated from each other (minute M) and are delivered to the paper discharge tray 11. By the time of separation, the toner has sufficiently cooled and solidified, and the toner has been sufficiently cooled and solidified as described in (1) of (effect) above.
As mentioned in item 1, the adhesion of the toner to the sheet P
Since the adhesion force is sufficiently large and the adhesion force to the fixing film 23 is extremely small, the fixing film 23
The separation of the sheet P and the sheet P can be easily and sequentially performed without substantially causing toner offset with respect to the fixing film 23.

The winding drive of the fixing film 23 of the fixing device 20 is stopped when the sheet P finishes passing through the fixing device 20 and its trailing edge is detected by the paper detection sensor PH2.

In the apparatus of this embodiment, the fixing film 23 is sequentially wound from the feed shaft 24 side to the winding IN 127 side at the same speed as the conveyance speed of the sheet P every time the fixing process of the sheet P is executed as described above. It will be used as such.

The fixing film winding forward drive control starts driving when a predetermined first timer time elapses from the time when paper feed is detected by the paper feed detection sensor PH1, and stops the drive when a predetermined second timer time elapses. During this time, the fixing process for the sheet P is executed, and the discharge detection sensor PH
It is also possible to have a configuration that does not use 2.

Further, it is also possible to adopt a configuration in which the drive is controlled by the leading and trailing end detection signals of the seat P from the sensor 29 and the lever 25.

In this embodiment, the temperature of the linear heating surface 28 of the heating element 21 is instantaneously raised to a high enough temperature relative to the melting point (or fixing temperature) of the toner when energized, so there is no need to preheat the heating element. , heat transfer to the pressure roller 22 during non-fixing is small. Also, during fixing, the fixing film, toner image, and sheet are interposed between the heating element 21 and the pressure roller 22, and the heat generation time is short, resulting in a rapid temperature gradient, so the pressure roller 22 does not rise in temperature. Even if continuous image formation is carried out to the extent necessary for practical purposes, the temperature is maintained below the melting point of the toner.

In the apparatus of this embodiment having such a configuration, the toner image made of heat-fusible toner on the sheet P is first heated and melted by the heating body 21 via the fixing film 23, and in particular, the surface layer is completely melted. Soften and melt. At this time, the heating body, fixing film, toner image, and sheet are brought into close contact with each other by the pressure roller 22, and heat is efficiently transferred.

Thereby, the heating of the sheet P itself can be suppressed as much as possible, and the toner image can be efficiently heated and melted. In particular, by limiting the time for energization and heat generation, it is possible to save energy.

A small heating element is sufficient, so its heat capacity is small, and there is no need to heat up the heating element in advance, so power consumption during non-image formation can be reduced, and temperature rise inside the machine can also be prevented. .

In this embodiment, since the temperature of the pressure roller 22 is maintained lower than the melting point of the toner as described above, it is possible to promote heat dissipation of the toner image in the cooling process following the toner image heating process. . Therefore, the time required for cooling can be shortened, and the device can be downsized.

(4) Dimensional relationship Figure 3 (a). ('b) is the heating body 21 and the pressure roller 22
, a fixing film 23, and a transfer paper P serving as a recording material.

A linear heat generating surface (heat generating part) 2 provided on the heating body 2l
The total length of the fixing film 8 in the transverse direction is H, and the pressure roller 2 is opposed to the heating body 21 with the fixing film 23 interposed therebetween.
When R is the same overall length dimension of 2, F is the width dimension of the fixing film 23, and P is the width dimension of the transfer paper P (dimension perpendicular to the conveyance direction), the dimensional relationship is P≦R≦H≦F. Set to . In this example, P<R<H<F. That is, the relationship between the pressure roller 22 and the fixing film 23 is R<F, and the fixing film 23 is
are in contact with each other over the entire length of the area.

In other words, the pressure roller 22 comes into contact with the heating body 21 via the fixing film 23, and there is no direct contact portion with the heating body. Therefore, when there is a direct contact part like the part A-A in FIG. 4, the occurrence of friction wear and damage between the part of the heating element heating surface 28 and the pressure roller 22 corresponding to the part A-A is avoided. By preventing this, the durability of the heating element is improved, and since there is no large frictional force generated at the direct contact portion A-A, the rotational driving torque of the pressure roller 22 can be reduced, and the driving force of the fixing device is reduced. The system can be simplified.

In addition to the above P≦R≦H≦F, the pressure roller 22
Since the heating element (heat generating surface) 21 (28) is not directly rubbed, the same effect as in the above example (FIG. 3) can be obtained.

FIG. 4 shows an example in which there is a direct contact opposing portion A-A between the heating body 21 and the pressure roller 22, and the dimensional relationship is P<F<R<H. There are opposing parts A and A where the heating body 21 and the pressure roller 22 come into direct contact with each other on the outer side of both edges, and these parts A-A
In this case, the heating body 21 and the pressure roller 22 are likely to be worn out and damaged in a short period of time, and the frictional resistance at those parts is large, increasing the rotational driving torque of the pressure roller 22.

(5) In addition, the fixing film 23 is sequentially wound and run from the delivery shaft 24 side to the take-up shaft 27 side every time the fixing process is performed, as in the embodiment device, and when the entire length has been wound and used, a new fixing film is created. In addition to using a rewinding system that replaces the film 23, toner offset to the fixing film 23 does not substantially occur, so if the film has little thermal deformation or deterioration, it can be used by winding it onto the winding shaft 27 side. It is also possible to use the finished fixing film 23 by rewinding it to the delivery shaft 24 side in a timely manner, or by reversing and exchanging the winding side and the delivery side. usage formula). Further, it is also possible to adopt a configuration in which the belt is of an endless belt type and rotated to perform the fixing process.

In the winding and replacing type, the fixing film 23 can be made of, for example, a thin and inexpensive polyester base material that has been subjected to heat-resistant treatment, and it can be made thinner regardless of durability, resulting in lower power consumption. can.

In the rewinding and reuse type, the fixing film is, for example, a 25 μm thick polyimide resin film as a base material with excellent heat resistance and mechanical strength, and a release layer made of a fluororesin or the like with high mold release properties is provided on the surface. It is possible to use a composite layer film provided, and it is preferable that the contact pressure between the heating body 21 and the pressure roller 22 is released during rewinding and reverse running.

When using multiple times, such as a rewinding type or an endless belt type, a felt pad is provided for cleaning the film surface, and a felt pad is impregnated with a small amount of mold release agent, such as silicone oil, and the bat is brought into contact with the film surface. Cleaning of the film surface and further improvement of carcass performance may be carried out. When the fixing film is treated with an insulating fluororesin, static electricity that disturbs the toner image is likely to be generated on the film, so it is a good idea to remove the static electricity using a grounded static eliminator brush. The film may be charged within a range that does not disturb the toner image by applying a bias voltage to the brush without being grounded. Furthermore, one measure is to add conductive powder fibers, such as carbon black, to the fluororesin to prevent the above-mentioned image disturbance caused by static electricity. Furthermore, the charge removal and conductivity of the pressure roller can be carried out by similar means. Furthermore, an antistatic agent or the like may be applied or added.

In either method, the fixing film 23 is configured as a cartridge that can be freely attached to and removed from a predetermined portion of the fixing device 20, thereby facilitating the work of replacing the fixing film.

The configuration of the heating body 21 and the control of energization to the heat generating surface (layer) 28 are not limited to those described above. For example, the heating surface 2 of the heating element
In place of 8, a thick film resistor or a ceramic chip array having PTC characteristics may be arranged, and the energization control may be conducted normally instead of in a pulsed manner.

In short, it is sufficient that the energizing heat generating part of the heating body and the heating part that heats the toner are integrally formed and fixedly supported.

The above-described embodiments are transfer-type electronic copying devices, but the image forming process and means include a direct type in which a toner image is directly formed and carried on electrofax paper, electrostatic recording paper, etc., and a magnetic recording image forming type. Copying machines, laser beam printers, facsimile machines, microfilm reader printers, display devices, and recording machines that form an image using heat-fusible toner on a recording material and fix it by heating using other appropriate image forming processes and means. The present invention can be effectively applied to various image forming apparatuses such as the above.

(Effects of the Invention) As described above, the present invention makes it possible to reduce the heat capacity of the heating body, which is the heating means, without causing fixation failure or offset in a toner image heat fixing type image forming apparatus. As a result, it is possible to realize an image forming apparatus with low power consumption during standby time and low internal temperature rise. Furthermore, the thin fixing film can be used repeatedly over a long period of time without any problem of wrinkles.

In addition, short-term wear and damage to the heating element is prevented, resulting in improved usage durability (
In addition, the driving torque of the pressurizing member is reduced, making it possible to simplify and downsize the drive system.

[Brief explanation of the drawing]

The drawings show an embodiment of the apparatus; FIG. 1 is an overall schematic diagram of the apparatus, FIG. 2 is an enlarged view of the fixing device in the fixing state, and FIGS. 3 and 4 show the heating body ( FIG. 2 is an explanatory diagram of the dimensional relationship among a heating roller, a pressure roller, a fixing film, and a transfer paper. 3 is a photosensitive tram, 8 is a transfer discharger, P is a transfer material sheet (
(recording material), 20 is the overall code of the fixing device, 21 is the heating element,
22 is a pressure roller, 23 is a fixing film, 23 is a winding shaft, and 24 is a delivery shaft. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] (1) An image forming means for forming an unfixed toner image corresponding to target image information by carrying toner made of a heat-melting resin or the like on the surface of a recording material, a fixing film, and 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; The fixing film is provided with a pressure member for bringing the surfaces into close contact with each other, and is driven to run in the same direction at the same speed as the conveyance speed of the recording material carrying the unfixed toner image conveyed from the image forming means side, and the pressure member. toner image heat fixing means for introducing the recording material between the recording material and heating and fixing the unfixed toner image on the surface of the recording material, the heating body of the toner image heat fixing means being linear in the transverse direction of the fixing film. What is claimed is: 1. An image forming apparatus comprising: a heat generating section, the fixing film being in contact with at least the entire length of the pressure member.