JPH01108589A - Heat roller fixing pressure roller and heat roller fixing device - Google Patents

Abstract

PURPOSE:To prevent the generation of a wrinkle caused by a peripheral speed difference by constituting the outside periphery of an elastic material layer so that it can be brought to elastic displacement locally against its moving direction. CONSTITUTION:When an elastic projection 39a of a pressure roller 37 rushes into a nip area which is pressed against a heat roller 30, each projection is brought to elastic deformation toward the inside in the radial direction and the advance direction of the outside periphery of the pressure roller, and a recording medium 41 is pressed against the outside peripheral surface of the heat roller. Simultaneously, by this pressing force, frictional force is generated in a contact part with the recording medium 41 of the elastic projection, and rotational driving force is transferred to the elastic projection through the recording medium. On the other hand, among the elastic projections positioned in the nip area, the part which is directly pressed against the outside periphery of the heat roller 30 moves at a peripheral speed being equal to a peripheral speed of the heat roller, and on the other hand, the part which is pressed against the recording medium 41 moves at a higher peripheral speed which has taken thickness of the recording medium into consideration. In such a way, paper can be allowed to pass through without generating a wrinkle.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a pressure roll used in a heat roll fixing device, and a heat roll fixing device using this pressure roll.

(Prior Art) Copying machines and printers using electrophotography have been widely put into practical use, and these copying machines and printers use heat roll fixing devices to fix toner images formed on recording media. ing.

FIG. 4 is a schematic cross-sectional view showing the structure of a heat roll fixing device conventionally used for boat fishing.

A pressure roll 2 is pressed against the heat roll 1 to form a nip area, and the recording medium 3 on which the unfixed toner image is formed is conveyed under pressure between the heat roll 1 and the pressure roll to transfer the toner image to the recording medium 3. to take root. The heat roll 1 has a hollow cylindrical core metal 4, the outer peripheral surface of the core metal 4 is coated with a fluorine resin layer 5 having mold releasability, and an infrared lamp is provided inside the core metal 4 as a heating source. 6 is placed. A temperature sensor 7 is disposed in contact with the outer periphery of the heat roll 1, and is connected to a control circuit (not shown) to maintain the outer periphery of the heat roll 1 at a constant temperature. The core metal 4 of the heat roll is connected to a drive device (not shown), and the drive force rotates the heat roll 1 in the direction of arrow a. The pressure roll 2 is constructed by covering the outer peripheral surface of a cylindrical core metal 8 with a silicone rubber layer 9 having a thickness of approximately 3 mm. The heat roll 1 is brought into pressure contact with the pressure roll 2 using a compression spring to form a nip area, and a rotational driving force is applied from the heat roll to the pressure roll through this nip area to cause the pressure roll to rotate in a driven manner. let The unfixed toner image formed on the recording medium 3 is
While passing through the nip area, the recording medium 3 is pressed against the heat roll 1 and is heated and melted by the heat from the heat roll.
fixed on top.

(Problems to be Solved by the Invention) The heat roll fixing device described above is configured to heat and fuse the toner image on the recording medium while the recording medium passes through the nip area. It is important to form it uniformly. For this purpose, a silicone rubber layer, which is a rubber-like elastic material, is formed on the outer periphery of the pressure roll, and the pressure roll is pressed against the heat roll to elastically deform the outer periphery of the pressure roll to form a nip area of a predetermined width. ing. However, when the recording medium passes through this nip area, the recording medium is conveyed under pressure from the top and bottom sides, so the nip area may be formed unevenly or the recording medium may be unevenly formed. If the leading end enters the nip area with waves, the recording medium will not be conveyed uniformly along the direction of travel, resulting in a problem of paper wrinkles.

Furthermore, copiers and printers not only record images on plain paper, but also direct mail, that is, often print addresses and recipients directly on the surface of envelopes, and even double-walled recording media such as envelopes are prone to wrinkles. It is strongly required that paper can be passed without this occurring. In this case, since the recording medium acts as a single rigid body, a single structure such as recording paper can be passed relatively easily without wrinkles.

However, double-structured items such as envelopes are conveyed with two superimposed rigid bodies fixed to each other in three directions, so the top side that contacts the heat roll and the pressure roll contact each other. Because of the influence of the difference in circumferential speed between the lower surface and the lower surface, it has been nearly impossible to convey the material under pressure without causing wrinkles. That is, with most heat roll fixing devices currently installed in copying machines and printers on the market, it has been impossible to convey envelopes under pressure without causing wrinkles.

Therefore, an object of the present invention is to solve the above-mentioned drawbacks and to provide a heat roll fixing device that can stably pass paper without wrinkles, particularly a heat roll fixer that can pass envelopes without wrinkles, and a heat roll fixing device that can pass envelopes stably without wrinkles. The present invention provides a pressure roller for roll fixing.

(Means for Solving the Problems) A heat roll fixing pressure roller according to the present invention includes a heat roll having a 6-heat source and a pressure roll having an elastic material layer formed on the outer periphery, which are pressed against each other. In the pressure roll for heat roll fixing, which fixes the toner image on the recording medium by passing the recording medium on which the toner image is formed through the nip area, the outer periphery of the elastic material layer is It is characterized in that it is constructed so that it can be locally elastically displaced in the direction of movement.

Further, the heat roll fixing device according to the present invention is characterized in that the outer periphery of the elastic material layer of the pressure roll can be locally elastically displaced in the nip area in the direction of movement thereof. .

(Function) FIG. 5 is a schematic diagram showing the state of the nip area when an envelope is passed through using a conventional heat roll fixing device. The heat roll 1 and the pressure roll 2 are pressed against each other to form a nip area, and the envelope 10 is passed through. This envelope 1
0 has a lower paper 10a that contacts the heat roll and a lower paper 10b that contacts the pressure roll, and the rear end and both side ends in the traveling direction are bent and fixed. Since the outer periphery of the pressure roll 2 can be elastically deformed, the nip area is formed in an arc shape along the outer periphery of the heat roll 1 when cut along a plane perpendicular to the central axis of the heat roll, and therefore the envelope 10 is also pressed. Since it is pressed against the heat roll by the roller, it deforms into an arc shape along the outer periphery of the heat roll 1. A pressing force is applied between the heat roll 1 and the pressure roll 2 to move the heat roll 1 at a circumferential speed of V. When rotated with , envelope 10
Frictional force acts between the upper paper 10a and the heat roll 1, and due to this frictional force, the upper surface side of the lower paper 10a that contacts the heat roll has a surface circumferential speed V of the heat roll. The lower surface side that contacts the lower paper 10b moves at a circumferential speed v. In addition, the upper paper 10a and the lower paper 10b
Due to this frictional force, the upper surface side of the lower paper 10b that contacts the upper paper 10a moves at a circumferential speed V1, and the lower surface side that contacts the pressure roller 2 moves at a circumferential speed V2. Moving. In the nip area, the envelope 10 is pressed against the outer periphery of the heat roll, so when determining the circumferential velocities v and v2, the envelope is regarded as a cylindrical body with the same center of curvature, and the cylindrical body moves at the same rotation speed as the heat roll. It can be calculated as Therefore, if the radius of the heat roll is ro and the thickness of the upper paper 10a and the lower paper 10b is d, then the radius of the lower surface of the upper paper 10a is ro+d, and the radius of the lower surface of the lower paper 10b is r, It becomes +2d. If the rotation speed of the heat roll is S, the circumferential speed is V. is V. −
2πros, and the circumferential velocity V, is V, = 2πS (r,
+d), the peripheral speed v2 is v2-2πS (re÷2d
). Therefore, the circumferential speed vo of the surface of the envelope 10 in contact with the heat roll 1 and the circumferential speed v of the surface in contact with the pressure roller 2
2, a circumferential speed difference of Vz-vo=4πSd will occur. On the other hand, the heat roll and the pressure roll are in pressure contact with each other over a long effective length, for example, over 256 mm when passing B4 size paper lengthwise. However, since the width of the envelope is approximately 50 to 60 mm, the heat roll and the pressure roll are brought into pressure contact with each other through the envelope 10 at the center, and are driven directly into pressure contact with each other at both ends.

Since the pressure roll is driven by the heat roll,
In the area where the pressure roll is in direct pressure contact with the heat roll, the pressure roll moves at a circumferential speed equal to the circumferential speed v0 of the heat roll. If the width of the envelope being passed is small relative to the effective length of the pressure roll in the longitudinal direction, the length of the area where the pressure roll is in direct pressure contact with the heat roll will be long, and therefore the entire pressure roll will be covered by the heat roll. peripheral speed V. You will have to move. As a result, the lower paper 10b of the envelope 10
It is considered that a sentencing speed difference Δv=4πSd between the lower surface side and the pressure roll occurs, and the lower paper job of the envelope 10 is pulled toward the rear end, causing wrinkles on the rear end. In addition, when passing wide envelopes, the circumferential speed in the area that is in direct pressure contact with the heat roll of the pressure roll is slower than the circumferential speed in the area that is in pressure contact with the envelope. This causes the envelope to pull toward the side, and wrinkles also occur at the bottom end of the envelope.

The present invention is based on this recognition, and eliminates wrinkles by locally absorbing the circumferential speed difference that occurs between the lower surface of the envelope and the pressure roller that presses against it in the nip area on the surface of the pressure roller. This is to prevent the occurrence of

Therefore, in the present invention, the outer circumferential surface of the pressure roll is made elastically displaceable in the direction in which the paper passes, and the pressure roller is moved by the frictional force generated between the lower surface of the envelope and the pressure roller in the nip area. The outer circumferential surface is locally elastically displaced in the paper passing direction. Due to this local elastic displacement of the pressure roller's outer circumferential surface, the outer circumferential portion of the pressure roller in the nip area can move at the same circumferential speed as the bottom surface of the envelope, effectively preventing the occurrence of a circumferential speed difference. .

(Example) Fig. 1 shows the configuration of an example of a heat roll fixing device according to the present invention, Fig. 1a is a sectional view taken along a plane perpendicular to the paper passing direction, and Fig. FIG. 1C is a plan view showing the external appearance of the pressure roll. The heat roll 30 has a hollow cylindrical core metal 31 made of aluminum, and a release layer 32 of fluororesin is coated on the core metal 31. The release layer 32 can also be composed of an oil-impregnated silicone rubber layer. Both ends of the core metal 31 are connected to bearings 33a and 3.
It is rotatably attached to the housing 34 of the fixing device via 3b. An infrared lamp 3 is installed as a heating source inside the core metal 31.
5 is placed, and the heat roll 30 is heated by radiant heat from this infrared lamp. A temperature sensor (not shown) is disposed in contact with the outer circumferential surface of the heat roll 30 to control the temperature of the outer circumferential surface of the heat roll 30 to be maintained at a constant temperature. A gear 36 is connected to one end of the core metal 31, and the heat roll is connected to a drive device (not shown) via the gear 36 to rotate the heat roll at a constant speed. A pressure roll 37 is arranged so as to be in pressure contact with the outer periphery of the heat roll 30.

The pressure roll 37 has a cylindrical core metal 38 made of stainless steel, and a 5 mm thick layer made of silicone rubber is placed on the core metal 38.
Cover with a layer of elastic material 39 of approximately 100 mL. This elastic material layer 39
Various rubber-like elastic materials can be used for the material, and for example, the material can be made of an elastic material such as urethane rubber or nitrile rubber. Both ends of the core metal 38 are connected to bearings 40a
and 40b, it is rotatably attached to the housing 34. In the fixing device according to the present invention, the heat roll and the pressure roll are pressed against each other by an interaxial fixing method. That is,
The distance between the axes of the heat roll and pressure roll is set to be smaller than the sum of the radius of the heat roll and the radius of the pressure roll, and the heat roll and pressure roll are pressed against each other to form a nip area. form. The pressure roll according to the present invention has a small change in elastic force with respect to a change in the distance between the shafts, as will be described later, and the elastic rubber material layer 39 is not easily affected by the compression set, so it is sufficient to press the roll by the method of fixing the shafts. can form a uniform nip area,
As a result, there is no need for a compression spring and the setting work becomes easier. As shown in FIGS. 1 and 1C, the pressure roll 37 according to the present invention has grooves of minute width extending parallel to the central axis of the roll formed at a predetermined pitch in the elastic material layer 39 on the outer periphery. Constructed by By forming grooves at a predetermined pitch over the entire circumference, the outer periphery of the pressure roll is made of an elastic rubber material, extends parallel to the central axis at a predetermined pitch, and protrudes radially outward. A series of elastic protrusions 39a are formed. When these elastic protrusions 39a enter the nip area where they come into pressure contact with the heat roll 30, each protrusion is elastically deformed inward in the radial direction and in the direction of movement of the outer periphery of the pressure roll, and the elastic force generated by this elastic deformation is used to record data. The medium 41 is pressed against the outer peripheral surface of the heat roll. At the same time, this pressing force generates a frictional force at the contact portion of the elastic protrusion with the recording medium 41, and this frictional force causes rotational driving force to be transmitted to the elastic protrusion via the recording medium. On the other hand, as described above, among the elastic protrusions located in the nip area, the portion that is in direct pressure contact with the outer circumference of the heat roll 30 moves at a circumferential speed equal to the circumferential speed of the heat roll, while the portion that is in pressure contact with the recording medium 41 is moved at a circumferential speed equal to the circumferential speed of the heat roll. It moves at a faster circumferential speed considering the thickness of the recording medium. Therefore, the elastic protrusion located in the nip area has two areas with different speed differences. In this case, if the driving force directly transmitted from the outer periphery of the heat roll to the pressure roll is greater than the driving force transmitted via the recording medium, the outer periphery of the pressure roll as a whole moves at the circumferential speed of the heat roll. However, since the elastic protrusion can be elastically displaced in the direction of travel, the elastic protrusion that comes into pressure contact with the recording medium is elastically displaced in the direction of travel due to the frictional force generated between it and the recording medium, and this As a result, it travels at a speed equal to the traveling speed of the outer periphery of the recording medium. As a result, the partial circumferential velocity difference occurring in the pressure roll, which is the cause of wrinkles as described above, is absorbed by the elastic displacement of the elastic protrusions, and paper wrinkles can be effectively prevented from occurring. In addition, when fixing a wide recording medium, in other words, the driving force transmitted to the pressure roll via the recording medium is stronger than the driving force transmitted through the part that is in direct pressure contact with the heat roll. If it is large, the elastic protrusion portion that comes into direct pressure contact with the heat roll will be elastically displaced in the direction opposite to the traveling direction, thereby absorbing the partial circumferential speed that occurs on the pressure roll. Although the grooves defining each elastic protrusion are shown relatively large in order to make the drawing clear, the width of the groove defining the protrusion varies depending on the nip width, roller diameter, rubber hardness of the elastic material layer, It can be set arbitrarily in consideration of the set temperature of the heat roll, etc., and for example, about 100 μm is sufficient. The reason for this is that when the elastic protrusion enters the nip area, it is sequentially elastically displaced in the advancing direction, and the same elastic displacement is performed sequentially in accordance with each position in the nip area.

Furthermore, if elastic protrusions are formed at a predetermined pitch on the outer peripheral surface of the pressure roll, the amount of change in the pressure contact force generated between the pressure roll and the heat roll relative to the amount of elastic deformation of the elastic material layer 39 on the outer periphery of the pressure roll is relatively small. Since it is small, that is, it is necessary when using an elastic rubber material with low rubber hardness, a uniform nip area can be formed even if the heat roll and pressure roll are fixed between their axes. By forming elastic protrusions on the outer periphery of the pressure roll, there will be a portion on the back side of the recording medium that does not come into contact with the pressure roll, but since the recording medium is evenly pressed against the outer circumferential surface of the heat roll by the elastic protrusions. Problems in which fixing performance deteriorates rarely occur.

2A to 2C are partial sectional views taken along a plane perpendicular to the central axis of the roll, showing the configuration of a modified example of the pressure roll according to the present invention.

In FIG. 2a, the outer periphery of the cylindrical core metal 50 is covered with an elastic material layer 51.
The pressure roll is shown in which elastic protrusions 52 having a substantially corrugated cross section are regularly formed along the circumferential direction on the outer periphery of the elastic material layer 51. In FIG. 2, a large number of grooves with a relatively shallow depth and a small pitch are formed on the outer periphery of the elastic material layer 51,
An example in which elastic protrusions 52 are formed in this way is shown. This pressure roller uses both the elastic force of the elastic protrusion 52 and the elastic force of the heath portion 52a of the elastic material layer that supports the elastic protrusion to press the recording medium against the heat roll. - It is possible to generate a layer-uniform pressing force. FIG. 2C shows a pressure roll in which elastic protrusions 52 are directly formed on the outer periphery of the core metal 50.

3a to 3C are perspective views showing the structure of another modification of the pressure roll according to the present invention. FIG. 3a shows an example in which elastic protrusions 60 are formed on the outer circumferential surface of the pressure roll, extending from the center toward the side ends to widen toward the end. If a protrusion is formed that widens from the center of the roll toward the side edges,
As shown by the arrow, a force is generated that pulls the recording medium to be conveyed under pressure in the direction of the side edge, making it possible to more effectively prevent the occurrence of wrinkles. FIG. 3 shows an example in which a large number of circular elastic protrusions 61 are formed on the outer periphery of the pressure roll. By forming the elastic protrusions 61 in this way, the elastic protrusions can be elastically displaced not only in the moving direction of the roll outer periphery but also in a direction perpendicular to this, thus causing the recording medium to be dislocated in the direction perpendicular to the conveyance direction. This is useful when a desired force is generated. FIG. 3C shows an example in which grooves intersecting the center axis are formed on the outer circumferential surface of the roll to form diamond-shaped elastic protrusions 62 over the entire surface. This diamond-shaped elastic protrusion is also useful because it can be elastically displaced in the recording medium conveyance direction and in a direction perpendicular thereto.

The present invention is not limited to the embodiments described above, and various modifications are possible. For example, in the above-mentioned embodiment, a roll that functions only as a pressure roll was explained, but if a hollow cylindrical core metal is used like a heat roll and a heating source is placed inside the core metal, it can also be used as a heat roll. can do.

Further, in the heat roll fixing device described above, only the heat roll is connected to a drive source and the pressure roll is driven. However, it is also possible to connect the heat roll and the pressure roll to separate drive sources and drive them. You can also do it. in this case,
The pressure roll according to the present invention has an outer periphery that can be elastically displaced in the movement direction of the outer periphery and in the opposite direction.
Even if there is a difference in circumferential speed between the heat roll and the pressure roll, the difference in circumferential speed can be locally absorbed, so they can rotate in proper pressure contact with each other, which improves the design of the roll drive system. This increases the degree of freedom of movement and eliminates inconveniences caused by differences in circumferential speed.

(Effects of the Invention) As explained above, according to the present invention, the outer peripheral surface of the pressure roll can be locally elastically displaced in the direction of movement of the outer peripheral surface, so that the heat roll and the pressure roll can be Even if a difference in circumferential speed occurs between them, this difference in circumferential speed can be absorbed by the pressure roll. As a result, it is possible to effectively prevent wrinkles from occurring due to the circumferential speed difference. In particular, a toner image formed on the surface of an envelope can be fixed without wrinkles even in the case of a double structure such as an envelope that is fixed in three directions.

In addition, in the pressure roll according to the present invention, since the elastic force increases gradually with respect to the amount of elastic deformation in the radial direction, it is possible to uniformly form the pressure bonding force between the pressure roll and the heat roll. The heat roll and pressure roll can be set by the interlocking method. As a result, a compression spring and a related compression mechanism are not required, and costs can be reduced. Furthermore, the work of setting the heat roll and pressure roll becomes easier, and the pressure roll can be driven at a predetermined speed in the same way as the heat roll, making it possible to further improve the conveyance of the recording medium.

[Brief explanation of the drawing]

FIGS. 1a-c are diagrams showing the configuration of a heat roll fixing device and a pressure roll according to the present invention, and FIGS. 2a-c are diagrammatic cross-sectional views showing the configuration of a modified example of the pressure roll according to the present invention. , Fig. 3 a - c are perspective views showing the structure of another modification of the pressure roll, Fig. 4 is a diagram showing the structure of a conventional heat roll fixing device and the pressure roll, and Fig. 5 shows an envelope. FIG. 6 is a schematic diagram showing the state of the second knob area when fixing. 30...Heat roll 32...Release layer 34.
...Housing 35...Infrared lamp.

Claims (1)

[Claims] 1. A recording medium in which a heat roll having a heating source and a pressure roll having an elastic material layer formed on the outer periphery are pressed against each other to form a nip area and a toner image is formed. A pressure roll for heat roll fixing, which fixes the toner image on the recording medium by passing the toner image through the nip area,
A pressure roll for heat roll fixing, characterized in that the outer periphery of the elastic material layer is configured to be locally elastically displaceable in the direction of movement thereof. 2. Claim 1, characterized in that elastic protrusions extending parallel to the central axis of the roll are formed on the outer periphery of the elastic material layer at a predetermined pitch over the entire circumference of the roll. A pressure roll for heat roll fixing as described in . 3. The pressure roll for heat roll fixing according to claim 1, wherein elastic protrusions are formed on the outer periphery of the elastic material layer over the entire periphery of the roll. 4. A heat roll having a heat source and a pressure roll having an elastic material layer formed on the outer periphery are pressed against each other to form a nip area, and the recording medium on which the toner image is formed is passed through the nip area. In the heat roll fixing device that fixes a toner image on a recording medium by moving the pressure roll, the pressure roll is configured such that the outer periphery of the elastic material layer can be locally elastically displaced in the nip area in the direction of movement thereof. A heat roll fixing device characterized by: 5. The heat roll fixing device according to claim 4, wherein the heat roll and the pressure roll are rotatably fixed by an interaxial fixing method to form a nip area.