JP2650446B2 - Fixing device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fixing device of a system for applying thermal energy to a recording material via a film.

This device is used for image forming devices such as copiers, laser beam printers, facsimile machines, micro film reader printers, image display (display) devices, and recorders. Target image information by direct means or indirect (transfer) method on the surface of recording material (electrofax sheet, electrostatic recording sheet, transfer material sheet, printing paper, etc.) using toner consisting of heat-meltable resin by means An unfixed toner image corresponding to the above-described method is formed and carried, and the unfixed toner image can be utilized as an image fixing device for performing a heat fixing process as a permanently fixed image on a recording material surface carrying the image.

Further, the present invention is not limited to the image fixing device, and can be used as a device for heating the image carrier widely, for example, a device for heating a recording material carrying an image to improve the surface property.

(Prior Art) Conventionally, for example, a recording material heating apparatus for heating and fixing an image includes a heating roller maintained at a predetermined temperature, and a pressure roller having an elastic layer and pressing against the heating roller. Therefore, a heat roller method of heating while nipping and conveying a recording material is often used.

As disclosed in U.S. Pat. No. 3,578,797, a belt fixing system is also known as an image fixing means. This is done by bringing the toner image into contact with the heating element web and heating it to its melting point to melt it.After melting, the toner is cooled to a relatively high viscosity, and the toner image is removed from the heating element web in a state where the tendency to adhere to the toner is reduced. This is a method of fixing without causing offset by going through the process of peeling.

 There are also a flash fixing method and an oven fixing method.

Recently, a heating device (film heating system) that includes a fixedly supported heating element, a film that is in pressure contact with the heating element, and a pressing member that causes the recording material to be in close contact with the heating element via the film is also available. It has been devised.

A system disclosed in Japanese Patent Application Laid-Open No. 63-313182 according to the applicant's earlier proposal belongs to this and applies to a recording material via a thin heat-resistant film (sheet) which is slidably pressed against a fixed heating body. Heating means for applying heat energy to the formed and unfixed toner image to soften / melt it to separate the film and the recording material, or to separate the film and the recording material after the toner is cooled and solidified.・ It is a device.

(Problems to be Solved by the Invention) However, the conventional heat roller system as described above, the belt fixing system described in US Pat. No. 3,578,797,
Other methods have the following problems.

Heat roller method: It takes a considerable time to rise to a predetermined temperature, during which time the image forming operation is prohibited. That is, there is a so-called wait time. Large electric power is required because heat capacity is required. A high heat-resistant roller bearing requires a heat-resistant special bearing. The configuration is such that the roller touches the roller directly, which is dangerous and requires a protective member. The recording material is wrapped around the roller due to the fixing temperature and the curvature of the roller, so that a jam trouble of the recording material is easily observed. Since the temperature of the fixing point for fixing the toner on the recording material is equal to the temperature of the separation point between the recording material and the heat roller, high-temperature offset depending on the separation temperature is likely to occur, and the degree of image gloss depending on the separation temperature. Cannot control.

Flash, oven fixing method: The device becomes large. If the sharpness of the image is reduced or the recording paper stays in the fixing device, there is a risk of firing.

Belt fixing method: This method also has the same problems as those of the heat roller method, such as the wait time and large power consumption.

In the film heating method, a low heat capacity heating element can be used, which saves power and shortens the wait time (quick start property). Since the fixing point and the separation point can be set separately, offset is also prevented. It is effective and has the advantage that various disadvantages of the conventional example can be solved.

In this film heating type fixing device, it is important to prevent wrinkles and uneven feeding in the moving film. The occurrence of wrinkles in the film causes fixing unevenness, and the uneven feeding causes image disturbance. Therefore, in this type of fixing device, an apparatus configuration is used in which tension is applied to the film using a tension roller to remove wrinkles and uneven feeding of the film.

The present invention is also a fixing device of the film heating type. However, it is possible to reduce the size and cost of this type of device by preventing the occurrence of film wrinkles and uneven feeding without using a tension roller. Aim.

(Means for Solving the Problems) The present invention provides a fixed heating means in which a heating element is supported by a holder, and a recording apparatus in which one surface slides with the heating device and the other surface carries an unfixed image. A fixing device that has an endless film that moves together with the material, and a drive roller that drives the film, and that fixes an unfixed image on a recording material by heat from the heating body through the film. Wherein the film is suspended only around the heating means and the driving roller, and the driving roller has a rubber layer on an outer periphery thereof.

(Operation) That is, in the fixing device of the film heating type of the present invention, the film sliding with the fixed heating means is stretched around only the heating means and the driving roller, and the driving roller has a rubber layer on the outer periphery. An apparatus having a configuration characterized in that the film slides on the heating means and a load acts on that part, but the film only contacts the heating means except for the driving roller, so that the film driving load due to contact is reduced. In addition, since the driving roller has a rubber layer on the outer periphery, the driving roller can drive the film reliably and perform good fixing.

A state where sufficient tension is applied to the film stretched between the heating means and the drive roller by adjusting the distance between the two parts without using a separate tension roller to prevent wrinkles and uneven feeding. Since a tension roller is not separately used, the size and cost of the apparatus can be reduced.

(Example) (1) Example 1 of fixing device (FIG. 1) FIG. 1 shows a film heating type fixing device 20 according to the present invention.
FIG. 2 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 is a heating element holder (heater holder)
The heat-insulating member 8 provided along the length of the horizontal heat-insulating member 8 is fitted and held with the surface on the side on which the energized heating element layer 3 is provided facing outside, and further held as necessary. The lever 8 is mounted and supported on the rigid support 9 with the heating element 1 side facing downward, and is fixedly disposed at a predetermined position of the fixing device with the heating element 1 facing downward.

Reference numeral 6 denotes a film drive roller disposed in parallel with the heating element above the stationary heating means (1.8, 9).

Reference numeral 5 denotes an endless belt-shaped fixing film suspended between the stationary heating means 1 (1.8, 9) and the driving roller 6, and the driving roller 6 is driven by an arrow. Is rotated clockwise by rotating clockwise.

Reference numeral 7 denotes a pressing roller having a rubber elastic layer having good releasability such as silicone rubber as a pressing member, and urging means (not shown) which sandwiches the film 7 against the lower surface of the heating body 1. Thus, the recording material P is rotated counterclockwise in the forward direction in the transport direction of the recording material P fed to the apparatus, for example, with a contact pressure of 4 to 7 kg.

The heating element 1 is a low-heat-capacity linear heating element whose longitudinal direction is perpendicular to the direction in which the film moves, and includes a substrate 2, a current-carrying heating element layer 3, a temperature detecting element 4, and the like.

The substrate 2 is a member having heat resistance, electrical insulation, and low heat capacity, and is, for example, an alumina substrate having a thickness of 1.0 mm, a width of 10 mm, and a length of 240 mm.

The current-carrying heating element layer 3 has a surface on one side of the substrate 2 on a film sliding side, and a Ta ₂ N.
This is a linear or belt-shaped low heat capacity layer provided by coating (screen printing or the like) an electric resistance material such as silver palladium to a width of 1.0 mm.

The temperature detecting element 4 (temperature measuring element) is a component of the temperature control 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. Is measured as the temperature of the heating body 1.

The heating element holder 8 is a heat insulator and has low heat resistance and poor heat conductivity, such as PPS (polyphenylene sulfide), bakelite, PBT, PAI (polyamide imide), PI (polyimide), PEEK (polyether ether ketone), and liquid crystal polymer. And the like, and a composite material of these resins with ceramics, metal, glass and the like.

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

Endless belt-shaped fixing film 5 driven to rotate
Has a width larger than the maximum width of the recording material to be introduced into the device and subjected to the fixing process.Since it is repeatedly provided for the heating and fixing of the toner image, it has excellent heat resistance, releasability and durability, Generally, 100 μm or less, preferably 40 μm or less, 2
Use a thin material having a thickness of 0 to 30 μm. For example, polyimide, (PI), polyetherimide (PEI), PES, PFA (4
PTFE (tetrafluoroethylene resin with good releasability) on at least the image contact surface side of a single-layer film or a composite layer film of a heat-resistant resin such as a fluoroethylene-porfluoroalkylvinyl ether copolymer resin) or a composite film such as a 20 μm thick film ). A release coating layer to which a fluororesin such as PAF or a conductive material such as carbon is added is applied to a thickness of 10 μm or less. The inner surface of the film serves as a driving slide.

The film 5 is rotated and driven between the drive roller 6 and the heater 1 fixedly arranged via the holder 8 and the support 9 and is given a tension without wrinkles or uneven feeding as it advances.
That is, wrinkles become uneven fixing, and feed unevenness causes image disturbance.To prevent these, for example, A4 vertical feed, that is, about several kg of feeding a PI film 5 having a width of 210 to 240 mm at a speed of 50 mm / sec. Although tension was required, by adjusting the position of the holder 8 or the support 9 or the driving roller 6, the film 5 is supported by this tension without flexing.
The occurrence of wrinkles and uneven feeding on the film 5 was able to be removed.

If a coating for reducing the frictional force is applied to the inner surface of the film in order to reduce the sliding resistance between the film 5 and the holder 8, the film driving force with the drive roller 6 cannot be obtained. It turned out that the resin holder was good. I tried to reduce the contact area by making fine unevenness on the surface to reduce friction, but film wear due to unevenness occurred,
It is suitable to use a burr-free smooth mold surface of a resin molded product comprehensively. Further effects were obtained by coating the surface of the resin molded article with a resin having a low coefficient of friction such as fluorine or silicone resin. It is effective to prevent the film from being damaged if the holder 8 has a shape in which all the film contact portions have a curvature. When the holder 8 is integrally formed with the rigid support 9, the strength, the accuracy by joining, and the weight reduction are improved to some extent.

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

In the case of this example, the above-mentioned linear or belt-shaped energizing heating element layer 3 of the heating element 1 is energized from both longitudinal ends thereof to generate heat over the entire length. The energization has a pulse-like waveform of a DC voltage, and has an energization control circuit configuration for giving a pulse corresponding to a desired temperature and energy release amount controlled by the temperature detecting element 4 by changing its pulse width. The pulse width is approximately 0.5 to 5 msec.

In this embodiment, a sensor (not shown) for detecting the leading and trailing edges of the recording material P is provided near the fixing device on the upstream side of the fixing device 20 in the conveying direction of the recording material P, and the sensor generates heat in response to the recording material detection signal. The recording material P determines the energization period for the body layer 3 by the fixing device.
It is controlled only for the necessary period of passing 20.

The leading end of the recording material P carrying the unfixed toner image Ta on the upper surface of the recording material P conveyed from the image forming unit (not shown) to the fixing device 20 due to the image forming operation performed by the image forming device in response to the image forming start signal is closer to the fixing device. The above-mentioned sensor (not shown) arranged in
, The rotation of the fixing film 5 is started,
The recording material P is guided by the guide 10a and enters between the fixing film 5 and the pressure roller 7 at the pressure contact portion N (fixing nip) between the heating body 1 and the pressure roller 7, and the unfixed toner image surface Is in close contact with the lower surface of the fixing film 5 moving in the same direction at the same speed as the conveying speed of the recording material P, and is applied to the heating element 1 in an overlapping state with the fixing film 5 without causing surface deviation or wrinkling. The sheet passes through the fixing nip N with the pressure roller 7 while receiving a squeezing pressure.

The toner image bearing surface of the recording material P receives the heat of the heating element layer 3 via the fixing film 5 while passing through the fixing nip portion N in a state of being pressed and adhered to the fixing film surface. The recording material P is softened and adhered to Tb.

In the case of this embodiment, the recording material P is separated from the fixing film 5 when the recording material P passes through the fixing nip N and exits.

At the time of this separation, the temperature of the toner Tb is still higher than the glass transition point of the toner, and the bonding force (adhesion) between the recording material P and the fixing film 5 at this separation time is small. The recording material P is always smoothly separated without causing a toner offset to the fixing film 5 surface and without causing the recording material P to be wound and jammed while being adhered to the fixing film 5 surface due to poor separation.

And, since the toner Tb in a state of a temperature higher than the glass transition point has an appropriate rubber property, the toner image surface at the time of separation has an appropriate uneven surface property without following the fixing film surface, and this surface property is improved. Since the toner image is maintained and cooled and solidified, excessive image gloss does not occur on the fixed toner image surface, and high quality image is obtained.

The recording material P separated from the fixing film 5 is guided by the guide 10b, and the temperature of the toner Tb, which is higher than the glass transition point, naturally lowers (naturally cools) before reaching the sheet discharging means, so that the temperature falls below the glass transition point. Then, the recording material P on which the image has been fixed is output onto the tray.

(2) Fixing Device Example 2 (FIG. 2) In the fixing device 20 of FIG. 1 described above, the recording material P is separated from the fixing film 5 when the recording material P passes through the fixing nip portion N (that is, after fixing). In this embodiment, the heating nips (1.8, 9) and the driving roller 6 are arranged in the horizontal direction with respect to the vertical and vertical arrangement of the apparatus shown in FIG. The recording material P that has passed through the fixing film 5
The melted toner is cooled appropriately in a toner layer cooling step, and then the film 5
This is a configuration mode in which it is separated from the surface.

(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 FIG. 1 according to the present invention.
The image forming apparatus of this example is a reciprocating platen type / rotating drum type
This is a transfer type electrophotographic copying machine.

Reference numeral 100 denotes an apparatus housing, and reference numeral 11 denotes a reciprocating original placing table made of a transparent plate member such as a glass plate disposed on the upper plate 100a of the apparatus housing. Reciprocatingly driven at a predetermined speed in the direction a and the left side a ′.

G is a manuscript, placed on the upper surface of the manuscript mounting table 11 with the image side to be copied facing downward according to a predetermined mounting standard,
The original is set by covering the original cover 11a with the original cover 11a.

Reference numeral 100b denotes a slit opening serving as a document illuminating unit that is opened on the surface of the machine housing top plate 100a with a direction perpendicular to the reciprocating movement direction of the document placing table 11 (perpendicular to the paper surface) as a longitudinal direction. The downward image surface of the document G placed and set on the document table 11 sequentially passes through the position of the slit opening 100b from the right side to the left side during the forward movement of the document table 11 to the right side a. During the passage, the light L of the lamp 13 is received through the slit opening 100b and the transparent document table 11 for illumination scanning. The reflected light of the illumination scanning light on the original surface is image-formed and exposed on the surface of the photosensitive drum 14 by the short-focus small-diameter imaging element array 12.

The photosensitive drum 14 is coated with a photosensitive layer such as a zinc-lead oxide photosensitive layer or an organic semiconductor photosensitive layer, and is driven to rotate clockwise as indicated by an arrow c at a predetermined peripheral speed about a central support shaft 14a. The photosensitive drum receives a uniform charging process of positive or negative polarity by the charger 15 and receives the image forming exposure (slit exposure) of the original image on the uniformly charged surface.
On the fourteenth surface, electrostatic latent images corresponding to the image of the document exposed by image formation are sequentially formed.

The electrostatic latent image is successively visualized by a toner made of a resin or the like which is softened and melted by heating by a developing device 16, and the developed toner image is transferred to a portion where a transfer discharger 19 as a transfer portion is provided. I will do it.

S is a cassette in which transfer material sheets P as recording materials are stacked and stored, and the sheets in the cassette are fed one by one by the rotation of a feed roller 17, and then the toner on the drum 14 is moved by a registration roller 18. When the leading end of the image forming section reaches the transfer discharger 19, the leading end of the transfer material sheet P also reaches the position between the transfer discharger 19 and the photosensitive drum 14 and is synchronized in timing so that they coincide with each other. Will be fed. Then, the transfer discharger 19 is applied to the surface of the sheet.
As a result, the toner images on the photosensitive drum 14 are sequentially transferred.

The sheet to which the toner image has been transferred in the transfer unit is sequentially separated from the surface of the photosensitive drum 14 by a separation unit (not shown), and is transported by
23, the unfixed toner image Ta guided to and carried by the fixing device 20 is subjected to the heat fixing process, and passes through a guide 10b and a discharge roller 10c as an image formed product (copy). Is discharged on top.

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

(Effects of the Invention) As described above, the present invention does not use a tension roller as a means for preventing film wrinkling and feeding unevenness in a film heating type fixing device, so that the device can be reduced in size and cost. In addition, the tension member is formed by the surface and the fixing portion exists at the tension portion. An image having no unevenness of the film and no unevenness of the fixing in the portion is obtained.

Since the film slides with the heating means, a load acts on that part.However, the film contacts only the heating means except for the driving roller, so that the film driving load due to the contact can be reduced, and the driving roller has a rubber layer on the outer periphery. Therefore, the drive roller can reliably drive the film, and can perform excellent fixing.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an example of a film heating type fixing device according to the present invention. FIG. 2 is the same drawing of another example of the apparatus. 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 detecting element, 5 is a fixing film, 6 is a film driving roller, and 7 is a pressure roller.

Claims (1)

(57) [Claims] 1. A fixed heating means in which a heating element is supported by a holder, and an endless shape in which one surface slides with the heating means and the other surface moves together with a recording material bearing an unfixed image. A film and a driving roller for driving the film, a fixing device for fixing an unfixed image on a recording material by heat from the heating body through the film, wherein the film is the heating means A fixing device, wherein the fixing device is suspended only around the driving roller, and the driving roller has a rubber layer on an outer periphery.