JPH03166579A - Fusing device - Google Patents

Abstract

PURPOSE:To obtain an image without irregularity of fixation by applying tensile force to a film only between a film driving part and a heating body. CONSTITUTION:While the film 5 is driven to be turned and advances between a driving roller 6 and the heating body 1 which is set and disposed through a holder 8 and a supporting body 9, the tensile force is applied to the film without wrinkle or the irregularity of feed. The film 5 is supported without deflection by the tensile force by adjusting the position of the holder 8 or the supporting body 9 or the driving roller 6, so that the wrinkle or the irregularity of feed which occurs to the film 5 is eliminated. Since a tension roller is not used, the device is miniaturized and the cost is reduced. Furthermore, the waviness of the film is not caused in a fixing part and the image without irregularity of fixation is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fixing device that applies thermal energy to a recording material through a film.

This equipment includes copying machines, laser beam printers, facsimile machines, microfilm reader printers, and image display (
In an image forming apparatus such as a display) device or a recorder, a recording material (electrofax machine) is produced using a toner made of heat-meltable resin or the like by an appropriate image forming process means such as electrophotography, electrostatic recording, or magnetic recording. An unfixed toner image corresponding to the desired image information is formed and carried on the surface of a sheet (electrostatic recording sheet, transfer material sheet, printing paper, etc.) by a direct method or an indirect (transfer) method, and the unfixed toner image is It can be utilized as an image fixing device that heats and fixes the 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 widely used as a device for heat-treating an image carrier, such as a device that heats a recording material that has rejected 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 and conveying it is often used.

A belt fixing system is also known as an image fixing means, as disclosed in US Pat. No. 3,578,797.

This is done by: 1) Bringing the toner image into contact with a heating element web and heating it to its melting point to melt it; 2) After melting, cool the toner to make it relatively high in viscosity; and 2) Heat it while reducing the tendency of the toner 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 (film heating method) consisting of a fixedly supported heating element, a film that presses against the heating element, and a pressure member that brings the recording material into close contact with the heating element through the film has been developed. It has been devised.

The system device disclosed in Japanese Patent Application Laid-Open No. 63-313182, which was previously proposed by the present applicant, belongs to this category. The basic method is to apply heat energy to an unfixed toner image formed and carried on a material to soften and melt it and separate the film and recording material, or to separate the film and recording material after the toner has cooled and solidified. It is a heating means/device.

(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. was there.

Heat roller method: It takes a considerable amount of time to reach a predetermined temperature, and during this time the image forming operation is prohibited.

That is, there is a so-called wait time.

■Because it requires heat capacity, a large amount of electric power 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 troubles such as jamming of the recording material.

■Since 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 temperature is likely to occur, and image gloss that depends on the separation temperature The extent of this 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 fixing device.

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: ■ A low heat capacity heating element can be used, resulting in power savings and shortened wait time (quick start); ■ The fixing point and separation point can be set separately, preventing offset. This is an effective method having advantages such as being able to solve various other drawbacks of the conventional example.

In this film heating type fixing device, it is important to prevent wrinkles and uneven feeding of the moving film from occurring. Wrinkling of the film causes uneven fixing, and uneven feeding causes image disturbance. Therefore, in this type of fixing device, a tension roller is used to apply tension to the film to remove wrinkles and uneven rimming of the film.

The present invention is also a film heating type fixing device, but
It is an object of the present invention to reduce the size and cost of this type of device by making it possible to prevent film wrinkles and uneven feeding without using a tension roller.

(Means for Solving the Problems) The present invention involves moving a film in contact with a heating body that is fixedly supported, and heating the recording material together with the film by bringing the recording material into close contact with the surface of the film opposite to the heating body. This fixing device applies thermal energy to a recording material from a heating body through a film by moving the recording material through the body position, and is characterized in that the film is tensioned only between a film drive unit and the heating body. This is a fixing device.

(Function) In other words, by adjusting the distance between the film drive section and the heating body section, wrinkles and uneven feeding can be prevented from occurring in the film stretched between the two sections without using a tension roller. This system applies sufficient tension to the film, and since no tension rollers are used, the device can be made smaller and less costly. Compared to the case where the tension area is located and causes uneven fixing, since the tension section is configured as a surface and the fixing section is present in the tension section, there is no unevenness in the film at least at the fixing section, and an image without uneven fixation can be obtained.

(Example) (1) Example 1 of fixing device (Fig. 1) Fig. 1 shows a film heating type fixing device 20 according to the present invention.
It is a structural diagram of an example.

1 is a low heat capacity linear heating element (heater) as a heating element. This heating element 1 has a heating element accommodating recess provided along its length on the lower surface of a horizontally elongated heat insulating member 8 serving as a heating element holder (heater holder), with the side on which an energizing heating element layer 3 to be described later is provided facing outward. If necessary, place the holder 8 on the rigid support 9 with the heating element 1 side facing downward.
This is mounted and supported at a predetermined position of the fixing device with the heating body 1 facing downward.

Reference numeral 6 denotes a film drive roller disposed above and in parallel with the fixed heating bodies (1, 8, 9).

Reference numeral 5 designates an endless belt-like fixing film that is stretched between the fixed heating elements 1 (1, 8, 9) and the drive roller 6. It rotates clockwise by being rotationally driven in the clockwise direction.

7 is a pressure roller having a rubber elastic layer with good mold releasability, such as silicone rubber, as a pressure member;
The film 7 is sandwiched and pressed against the lower surface of the recording material P with a total contact pressure of, for example, 4 to 7 kg by an unillustrated biasing means, and the film 7 is pressed against the lower surface of the recording material P in the direction of conveyance of the recording material P fed to the apparatus. Rotate counterclockwise in direction.

The heating body 1 is a low heat capacity linear heating body whose length is in the direction intersecting the plane movement direction of the film, and is composed of a substrate 2, a current-carrying heating layer 3, a temperature sensing element 4, and the like.

The base 2 is a heat-resistant, electrically insulating, and low heat capacity member,
As an example, thickness 1.0mm, width 10mm, length 2 4
It is a 0 mm alumina substrate.

The current-carrying heating element layer 3 has one surface of the substrate 2 facing the film sliding side, and Ta2 is formed approximately in the center of the surface along the longitudinal direction of the surface.
Width 1. Omflll
It is a linear or band-shaped layer with low heat capacity that is applied by coating (screen printing, etc.) on

The temperature detection element 4 (temperature detection element) is a component of the temperature adjustment system of the heating element 1, and is provided on the surface of the substrate 2 opposite to the surface on which the energized heating element layer 3 is provided, and is configured to detect the temperature of the substrate 2. Heating body 1
Temperatures are taken as the temperature.

The heating element holder 8 is made of a heat insulating material with poor heat resistance and thermal conductivity, such as PPS (polyphenylene sulfite), Bakelite, PBT-PAI (polyamideimide), P
I (polyimide) It can be constructed from highly heat-resistant resins such as PEEK (polyetheretherketone) liquid crystal polymers, and composite materials of these resins and ceramics, metals, glass, etc.

The drive roller 6 is a solid or hollow metal roller, or one whose outer periphery is coated with a rubber layer or resin layer such as urethane, EPDM, or CR to increase the coefficient of friction with the film 5.

The endless belt-shaped fixing film 5, which is rotated and driven, has a width wider than the width of the largest recording material to be introduced into the apparatus and subjected to fixing processing, and is repeatedly used to heat and fix toner images. It has excellent heat resistance, mold releasability, and durability, and has a thin wall of generally 100 μm or less, preferably 40 μm or less, and 20 to 30 μm. For example, polyimide (PI) polyetherimide (PE I)
・Single-layer film or composite layer film of heat-resistant resin such as PES-PFA (tetrafluoroethylene-barroalkyl vinyl ether copolymer resin), e.g. 20μ
A 10 μm thick releasable coat layer containing a fluororesin such as PTFE (tetrafluoroethylene resin) or PAF, which has good releasability, and a conductive material such as carbon, is applied to at least the image contact side of the m-thick film. These are as shown below. The inner surface of the film becomes a driving sliding part.

The film 5 is rotationally driven between a drive roller 6 and a heating element 1 fixedly arranged via a holder 8 and a support 9, and tension is applied thereto without wrinkles or uneven feeding. That is, wrinkles cause uneven fixing, and uneven feeding causes image disturbance. To prevent these, for example, A4 lengthwise feeding, that is, feeding a PI film 5 with a width of 210 to 2400111 at a speed of 50 mm/sec, requires a diagonal. kg of tension was required, but by adjusting the position of the holder 8, support 9, or drive roller 6, the film 5 is supported without deflection by this tension, thereby preventing wrinkles and uneven feeding of the film 5. I was able to remove it.

If a coating is applied to the inner surface of the film to reduce the frictional force in order to reduce the sliding resistance between the film 5 and the holder 8, the film cannot drive the drive roller 5, so it is desirable to reduce the frictional force on the holder 8 side. I found out that the resin holder is good. In order to reduce friction, we tried to reduce the contact area by creating minute irregularities on the surface, but the irregularities caused the film to wear out, so overall it was more suitable to use the smooth mold surface of the resin molded product. . Further effects were obtained by coating the surface of this resin molded product with a resin having a low coefficient of friction such as fluorine or silicone resin.

In terms of the shape of the holder 8, it is effective to prevent damage to the film by making all the film contacting portions have a curvature.

When the holder 8 is integrally molded on the rigid support 9, the strength and precision of joining are improved, and the weight is reduced to some extent.

The lower surface of the substrate 2 on which the heating element layer 3 is formed is a film 5.
Since it is a sliding surface, it is preferable to form a sliding protective layer such as Ta205 to protect the surface.

In the case of this example, electricity is applied to the linear or strip-shaped current-carrying heating layer 3 of the heating body 1 from both longitudinal ends thereof to cause the heating layer 3 to generate heat over its entire length. The energization is a DC voltage pulse waveform, and the energization control circuit is configured to provide a pulse according to the desired temperature and energy release amount controlled by the temperature detection element 4 by changing the pulse width. The pulse width is approximately 0.5 to 5IIISeC.

Furthermore, in this example, the leading and trailing edge detection sensors (
(not shown), and depending on the recording material detection signal of the sensor, the period of energization to the heating element layer 3 is determined so that the recording material P is fixed to the fixing device 2.
It is controlled only during the necessary period when it passes through 0.

The image forming apparatus performs an image forming operation in response to an image forming start signal, and the leading edge of the recording material P carrying an unfixed toner image Ta on its upper surface, which is conveyed from the unillustrated image forming section side to the fixing device 20, is closer to the fixing device. The aforementioned sensor (not shown) arranged in
When detected, rotation of the fixing film 5 is started,
The recording material P is guided by the guide 10a and the fixing film 5 is placed in the pressure contact area N (fixing nip) between the heating body 1 and the pressure roller 7.
and the pressure roller 7, and the unfixed toner image surface adheres to the lower surface of the fixing film 5, which is moving in the same direction at the same speed as the conveyance speed of the recording material P, causing surface misalignment and wrinkles. The film passes through the fixing nip N between the heating member 1 and the pressure roller 7 while being subjected to a pinching force in an overlapping state together with the fixing film 5 without causing a pinching force.

The toner image-carrying member of the recording material P receives heat from the heating element layer 3 through the fixing film 5 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 surface of the recording material P.

In the case of the apparatus of this example, the recording material P and the fixing film 5 are separated from each other when the recording material P passes through the fixing nib portion N and comes out.

At this time of separation, the temperature of the toner Tb is still higher than the glass transition point of the toner, and therefore, the bonding force (adhesive force) between the recording material P and the fixing film 5 at this time of separation is small, so the recording material P is The toner offset to the 5th surface of the fixing film hardly occurs, and the recording material P is always separated smoothly without being stuck to the 5th surface of the fixing film and jammed due to poor separation.

Since the toner Tb at a temperature higher than the glass transition point has appropriate rubber characteristics, the toner image surface upon separation does not follow the fixing film surface but has an appropriate uneven surface. Since the toner is maintained and cooled and solidified, excessive image gloss does not occur on the fixed toner image surface, resulting in a high quality image.

While the recording material P separated from the fixing film 5 is guided by a guide 10b and reaches the paper ejection means, the temperature of the toner Tb, which is higher than the glass transition point, naturally cools down (naturally cools) to a temperature below the glass transition point. As a result, the recording material P on which the image has been fixed is output onto the tray.

(2) Fixing device example 2 (FIG. 2) The above-mentioned fixing device 20 shown in FIG. In this example, the heating element 1 and the driving roller 6 are arranged horizontally on the left and right, compared to the vertical arrangement of the apparatus shown in FIG. The molten toner is then conveyed in close contact with the 5th surface of the fixing film, and the molten toner is appropriately cooled during this period as a toner layer cooling step, and then separated from the 5th surface of the film.

(3) Example of Image Forming Apparatus (FIG. 3) FIG. 3 shows a schematic configuration of an example of an image forming apparatus incorporating the fixing device 20 of the example shown in FIG. 1 according to the present invention.

The image forming apparatus in this example is a reciprocating document plate type, a rotating drum type,
This is a transfer type electrophotographic copying device.

100 is a device cabinet; 11 is a top plate 100 of the device cabinet;
This is a reciprocating type original document mounting table made of a transparent plate member such as a glass plate placed on top a, and it reciprocates at a predetermined speed on the top plate 100a of the machine casing to the right a and left a in the drawing, respectively. Driven.

G is a document, which is placed on the top surface of the document table 11 with the image side to be copied facing downward according to predetermined placement standards;
The document is set by placing the document pressure bonding plate 11a on top of the document 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 11 (direction perpendicular to the plane of the paper). The downward image surface of the original document G set on the document placement table 11 is sequentially exposed to the slit opening 10 from the right side to the left side during the forward movement of the document placement table 1 to the right side a.
It passes through the position of 0b, and in the process of passing, the lamp 13
Light L is passed through the slit opening toob and the transparent original table 1
1, and the illumination is scanned. The light reflected from the document surface of the illumination scanning light is image-formed and exposed on the surface of the photosensitive drum 14 by the short focus and small diameter imaging element array 12 .

The photosensitive drum 14 is coated with a photosensitive layer such as a zinc oxide photosensitive layer, an organic semiconductor photosensitive layer, etc., and has a central support of % 1 4 a
is driven to rotate clockwise in the direction of arrow C at a predetermined circumferential speed, and during the rotation process is uniformly charged with positive or negative polarity by charger l5, and the original document is placed on the uniformly charged surface. By receiving an image-forming exposure (slit exposure), electrostatic latent images corresponding to the image-forming exposed original image are sequentially formed on the surface of the photosensitive drum 14.

This electrostatic latent image is sequentially developed by a developing device 16 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 19 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 one by one by the rotation of the feed roller 17, and then the sheets are fed by the registration roller 18 onto the drum l4. When the leading edge of the toner image forming section of P reaches the transfer discharger 19, the transfer material sheet P
The leading edge of the transfer discharger 19 and the photosensitive drum 14 are also timed so that they exactly reach the position between the transfer discharger 19 and the photosensitive drum 14, and are fed synchronously. Then, the toner image on the photosensitive drum 14 side is sequentially transferred onto the surface of the fed sheet by the transfer discharger 19.

The sheet to which the toner image has been transferred in the transfer section is sequentially separated from the surface of the photosensitive drum 14 by a separating means (not shown), and is led to the above-mentioned fixing device 20 by the conveying device 23 to remove the unfixed toner image Ta carried thereon. After being heated and fixed, it is transferred to the guide 10b and discharge roller 10 as an image-formed product (copy).
c and is discharged onto the paper discharge tray 21 outside the machine.

On the other hand, the surface of the photosensitive drum 14 after the toner image transfer is subjected to removal of adhered contaminants such as residual toner by a cleaning device 22, and is used repeatedly for image formation.

(Effects of the Invention) As explained below, the present invention does not use a tension roller as a means to prevent wrinkles or uneven feeding of the film in a film heating type fixing device, so the device can be made smaller and lower in cost. Not only that, but compared to the conventional case where the heating body is located in the middle of the waving of the film between two axes, causing uneven fixing, the tension part is composed of a plane and the fixing part is present in the tension part, so at least There is no unevenness in the film at the fixing section, and an image with no uneven fixation can be obtained.

[Brief explanation of the drawing]

FIG. I is a schematic configuration diagram of an example of a film heating type fixing device according to the present invention. Figure yJ2 is the same diagram as above of another example of the device. FIG. 3 is a schematic configuration diagram of an example of an image forming apparatus. 14 is a photosensitive drum, P is a transfer material sheet as a recording material,
20 is a fixing device, 1 is a heating element, 3 is a heating element, 4 is a heating element temperature detection element, 5 is a fixing film, 6 is a film drive roller, and 7 is a pressure roller. /100 Figure 1

Claims (1)

[Claims] (1) A film is brought into contact with a fixedly supported heating body and moved, a recording material is brought into close contact with the surface of the film opposite to the heating body, and the film is moved and passed through the heating body together with the film, and the film is removed from the heating body. 1. A fixing device that applies thermal energy to a recording material through a fixing device, characterized in that the film is tensioned only between a film drive section and the heating body section.