JP4103988B2 - Fixing roller and image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fixing roller that conveys a recording medium or the like while sandwiching a recording medium with a pressure roller, and an image forming apparatus including the fixing roller.
[0002]
[Prior art]
2. Description of the Related Art As an output device for a computer or workstation, an electrophotographic image forming apparatus that forms an image on a recording medium using a powder developer (toner) is known. In such an image forming apparatus, for example, an image bearing member such as a photosensitive drum is irradiated with light carrying image information (for example, a laser) to form an electrostatic latent image, and a developing roller is used for the electrostatic latent image. Then, toner is supplied to form a developed image, and this developed image is transferred to a recording medium using a transfer roller or the like to form a transferred image (developed image). The recording medium on which the transfer image is formed is conveyed to a fixing device, and the transfer image is fixed on the recording medium in the fixing device. The fixing device is usually provided with a fixing roller having a built-in heater and a pressure roller in pressure contact with the fixing roller. When the transfer image is fixed on the recording medium, the transfer image is heated and pressed at a predetermined fixing temperature while the recording medium is nipped and conveyed by the fixing roller and the pressure roller. The transfer image is fixed on the recording medium by this heating and pressurization. The recording medium on which the transferred image is fixed is discharged while being sandwiched between discharge rollers or the like.
[0003]
The fixing device will be described with reference to FIG.
[0004]
FIG. 7 is a schematic diagram illustrating a schematic configuration of the fixing device.
[0005]
The fixing device 100 is for making the toner (image) 102 a permanent visible image on the recording medium 104. The recording medium 104 conveyed in the direction of arrow A by a conveyance unit (not shown) is guided by the fixing inlet guide 106 and enters the nip portion 108 between the fixing roller 120 and the pressure roller 130.
[0006]
The fixing roller 120 is for heating and melting the toner. The thermistor 140 is in contact with the outer peripheral surface (front surface) of the fixing roller 120, and the thermistor 140 is configured to measure the temperature of the outer peripheral surface of the fixing roller 120. Further, the fixing roller 120 incorporates a heat source (a heating element) such as a halogen heater 122. A controller (not shown) controls the halogen heater 122 based on the outer peripheral surface temperature measured by the thermistor 140, whereby the outer peripheral surface temperature of the fixing roller 120 is maintained at a predetermined fixing temperature.
[0007]
As the fixing roller 120, for example, an outer peripheral surface of a cored bar 124 made of, for example, an iron or aluminum pipe is coated with a fluororesin layer 126 having good releasability. The fixing roller 120 is rotated in the direction of arrow B by a drive source (not shown).
[0008]
The pressure roller 130 is for pressing the recording medium 104 against the fixing roller 120 with a predetermined pressure. As the pressure roller 130, for example, an outer peripheral surface of a metal core 132, for example, covered with an elastic body layer 134 such as silicone rubber or fluororubber with a predetermined thickness is generally used. While pressing the pressure roller 130 against the fixing roller 120 with a predetermined pressure and rotating it in the direction of arrow C, a load for fixing the toner 102 to the recording medium 104 is applied.
[0009]
When the recording medium 104 enters the nip portion 108, the toner 102 on the recording medium 104 is melted at the fixing temperature, and the melted toner 102 is pressed against the recording medium 104 with the load described above. Fixed to 104. The recording medium 104 on which the toner 102 is fixed is separated from the fixing roller 120 and the pressure roller 130 by a separation claw 142 and reaches a paper discharge roller (not shown), and is discharged out of the apparatus by the paper discharge roller.
[0010]
By the way, for example, when the fixing roller 120 is manufactured by cutting an aluminum pipe-shaped member, the outer diameter of the central portion in the longitudinal direction of the fixing roller 120 is about 0.07 mm to 0.2 mm than the outer diameter of both end portions in the longitudinal direction. It may be made smaller (so-called inverted crown shape). In this way, by making the both ends in the longitudinal direction thicker than the central part in the longitudinal direction of the fixing roller 120, the peripheral speed of the both ends in the longitudinal direction is increased and the recording medium 104 is conveyed so as to be pulled outward (so-called reverse crown). Effect). As a result, the recording medium 104 can be transported without causing wrinkles on the recording medium 104.
[0011]
The fixing roller 120 described above is required to rise quickly from the viewpoint of energy saving. For this reason, there is an image forming apparatus in which the time (rise time) from when the image forming apparatus main body is completely cooled to when the main switch is turned on and when the first copy is discharged is 30 seconds or less. This rise time is getting shorter year by year.
[0012]
In addition, it is required to minimize power consumption for warming the fixing device in a standby state in which the main switch of the image forming apparatus main body is turned on. For this reason, in the above standby state, it is necessary to completely turn off the heater of the fixing device. Thus, when the heater of the fixing device is completely turned off in the standby state, in order to bring the fixing roller to a predetermined temperature almost at the same time when the heater is turned on, the thickness of the fixing roller is reduced to reduce its heat capacity. It is necessary to keep. For this reason, a fixing roller made of an aluminum alloy having a good thermal conductivity is often used.
[0013]
In order to shorten the rise time described above, the thickness of the fixing roller 120 made of aluminum has recently been reduced to about 0.8 mm. When the thickness of the fixing roller 120 is further reduced, the fixing is performed when the recording medium 104 is sandwiched between the fixing roller 120 and the pressure roller 130 (nip portion 108) and the developed image is fixed with heat and pressure. The roller 120 may be deformed. As described above, when the central portion in the longitudinal direction of the fixing roller 120 is made thinner than both ends in the longitudinal direction, the central portion in the longitudinal direction is easily deformed, so that sufficient fixing performance cannot be secured in the central portion in the longitudinal direction. There is a fear.
[0014]
In order to solve the above problems, a technique has been proposed in which a helical coil spring is inserted into the fixing roller 120 to reinforce the fixing roller 120 (see Japanese Patent Application Laid-Open No. 10-116675). Further, a technique for reinforcing the fixing roller 120 by forming a spiral rib on the inner peripheral surface of the fixing roller 120 has been proposed (see Japanese Patent Application Laid-Open No. 2000-29342).
[0015]
[Problems to be solved by the invention]
However, in the fixing roller in which the spiral coil springs and ribs are provided on the inner peripheral surface as described above, a portion of the outer peripheral surface corresponding to the opposite side of the spiral portion of the inner peripheral surface is more than the other portion. Has high strength. For this reason, the outer peripheral surface on the opposite side has a higher nip pressure than the other outer peripheral surfaces, and the reverse crown effect is reduced. In addition, since the portion where the nip pressure is high is spiral, the recording medium is brought to the longitudinal end of the fixing roller during conveyance. Accordingly, the recording medium may be skewed or wrinkles may occur on the recording medium, resulting in poor transportability.
[0016]
In view of the above circumstances, an object of the present invention is to provide a fixing roller having high strength and good transportability, and an image forming apparatus including the fixing roller.
[0017]
In order to achieve the above object, the fixing roller of the present invention comprises:
(1) In reverse crown shape A hollow cylindrical roller;
(2) A wire rod that extends in the longitudinal direction of the cylindrical roller while being spirally wound in the hollow portion of the cylindrical roller and contacts the inner peripheral surface of the cylindrical roller;
(3) The wire is made of the cylindrical roller Longitudinal center The spiral winding directions are opposite to each other, In addition, the spiral portion of the wire rod is positioned so that the upstream portion in the rotational direction of the cylindrical roller is located closer to the central portion in the longitudinal direction of the cylindrical roller than the downstream portion in the rotational direction continuous to the upstream portion in the rotational direction. When a member to be conveyed is sandwiched and conveyed in a nip portion between the cylindrical roller and another roller, the portion with a high nip pressure is the central portion in the longitudinal direction of the cylindrical roller. Moving from one to the longitudinal end It is characterized by this.
[0018]
here,
(4) The wire may be formed by joining a plurality of spiral wires that are in contact with the inner peripheral surface of the cylindrical roller and shorter than the cylindrical roller.
[0019]
Also,
(5) The wire may be made of an elastic material.
[0020]
Another fixing roller of the present invention for achieving the above object is
(6) In reverse crown shape A hollow cylindrical roller;
(7) Two spirals shorter than the cylindrical roller that extend in the longitudinal direction of the cylindrical roller and are in contact with the inner peripheral surface of the cylindrical roller while being spirally wound in the hollow portion of the cylindrical roller A wire rod combined with a wire rod,
(8) These two short helical wires are those in which the spiral winding directions are opposite to each other, And the rotation direction upstream part of the said cylindrical roller is located in the longitudinal direction center part side of the said cylindrical roller rather than the rotation direction downstream part which follows this rotation direction upstream part among this helical wire. Wound in a spiral And
(9) When a transported member is sandwiched and transported in the nip portion between the cylindrical roller and another roller, the portion with a high nip pressure moves from the longitudinal center portion of the cylindrical roller toward the longitudinal end portion. It is characterized by this.
[0021]
In order to achieve the above object, an image forming apparatus according to the present invention provides:
(10) A fixing roller according to any one of the above is provided.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
A schematic structure of an image forming apparatus incorporating an embodiment of a roller unit of the present invention will be described with reference to FIG.
[0028]
FIG. 1 is a schematic diagram showing a digital copying machine as an example of an image forming apparatus in which an embodiment of a roller unit of the present invention is incorporated.
[0029]
On the top surface of the copying machine 10, a rectangular parallelepiped original pressing plate 12 that can be opened and closed is disposed. An image reading device 14 that reads an image recorded on the original is disposed below the original pressing plate 12. The upper surface (upper wall) of the image reading device 14 is a document table glass (not shown) on which a document is placed.
[0030]
An operation panel (not shown) for inputting the number of copies and the like is arranged on the front side (front side) of the original cover 12. A cassette 16 that stores a plurality of cut sheets is provided at the lower part of the copying machine 10 so as to be freely inserted into and removed from the copying machine 10. In addition, a space is formed in the left portion of the copying machine 10, and a paper discharge tray 18 on which the discharged recording paper is stacked is formed.
[0031]
A procedure for forming an image with the copying machine 10 will be described.
[0032]
In order to form an image recorded on an original on a recording medium, the original pressure plate 12 is opened, and the original is placed on the upper surface of an original platen glass (not shown) so that the image surface faces downward. The original is pressed and fixed by the original pressing plate 12. Next, by pressing a predetermined operation button or the like, the image recorded on the document is read by the image reading device 14. The read image is converted into a digital signal, and this digital signal is transmitted to the laser scanner 20.
[0033]
The signal transmitted to the laser scanner 20 is converted into laser light, and this laser light is irradiated onto the photosensitive drum 22 via the scanner mirror 20a and the folding mirror 20b that rotate at high speed. The photosensitive drum 22 is uniformly charged by a charger 24, and an electrostatic latent image is formed on the photosensitive drum 22 irradiated with laser light. The electrostatic latent image is developed with the developer supplied from the developing roller 26 to form a developed image.
[0034]
On the other hand, a recording medium such as recording paper is fed from the cassette 16 in the direction of arrow A (paper feeding direction) by the paper feeding roller 28, and conveyed to the transfer roller 34 by the conveying roller 30 and the registration roller 32. The transfer roller 34 transfers the developed image of the photosensitive drum 22 to the recording medium while sandwiching the recording medium together with the photosensitive drum 22. The recording medium to which the developed image is transferred is guided to the fixing device 40 by the conveyance guide 36. The fixing device 40 is provided with a fixing roller 50 (which is an example of a roller unit according to the present invention) and a pressure roller 70, and a recording medium is conveyed between these two rollers 50 and 70 and developed. The image is fixed on the recording medium. The recording medium on which the developed image is fixed in this manner is discharged by the discharge roller 80 and stacked on the discharge tray 18.
[0035]
The basic configuration of the fixing device 40 is the same as the configuration of the conventional fixing device 100 shown in FIG. The fixing roller 40 is different from the fixing device 100 in the fixing roller 50. The structure of the fixing roller will be described with reference to FIGS.
[0036]
2A is a schematic diagram showing the inside of the fixing roller, and FIG. 2B is a graph showing the nip pressure of the fixing roller in FIG. FIG. 3 is a perspective view showing a coil spring. FIG. 4 is a cross-sectional view showing the fixing roller of FIG.
[0037]
The fixing roller 50 includes a pipe-shaped (hollow cylindrical) fixing roller tube 52 (an example of the cylindrical roller in the present invention) made of an alloy of aluminum and magnesium. The fixing roller tube 52 is cut so that the thickness thereof is 0.28 to 0.32 mm over the entire area. A release layer (not shown) is formed on the outer peripheral surface of the fixing roller tube 52. This release layer is a fluororesin having high releasability, oil-impregnated silicone rubber, or a silicone rubber layer having a fluororesin layer formed on the surface thereof.
[0038]
In the hollow portion of the fixing roller tube 52 (inside the fixing roller 50), a spirally wound coil spring 60 (which is an example of a wire according to the present invention) is disposed. The outer diameter of the coil spring 60 is about 0.1 mm to 0.5 mm larger than the inner diameter of the fixing roller tube 52. For this reason, the coil spring 60 is in contact with an inner wall surface (an example of the inner circumferential surface referred to in the present invention) 52a surrounding the hollow portion of the fixing roller tube 52 and presses (presses) the inner wall surface 52a outward. ) The coil spring 60 is fixed to the fixing roller tube 52 and rotates together with the fixing roller tube 52.
[0039]
When manufacturing the fixing roller 50 described above, a coil spring 60 having an outer diameter that is about 0.1 mm to 0.5 mm larger than the inner diameter of the fixing roller tube 52 as described above is prepared. Both end portions are inserted into the hollow portion of the fixing roller tube 52 in a state in which the both end portions are twisted in the diameter reducing direction (the direction in which the winding is tight and the outer diameter is reduced). After the insertion is completed, the twist of the coil spring 60 is released. Thereby, the outer peripheral surface of the coil spring 60 contacts the inner wall surface 52a and pushes the inner wall surface 52a outward. Since the fixing roller tube 52 is reinforced by the coil spring 60 in this manner, even if the pressure roller 70 (see FIG. 1) presses the fixing roller 50, the fixing roller tube 52 is not deformed.
[0040]
A driving gear 54 is attached to one end portion of the fixing roller tube 52 in the longitudinal direction, as shown in FIG. The drive gear 54 is for transmitting a driving force for rotating the fixing roller tube 52 to the fixing roller tube 52.
[0041]
The outer peripheral surface of the fixing roller tube 52 opposite to the portion where the coil spring 60 is in contact is pressed more strongly than the outer peripheral surface opposite to the portion where the coil spring 60 is not in contact. Therefore, the nip pressure when the fixing roller 50 is pressed against the pressure roller 70 is different from the portion where the coil spring 60 is in contact with the other portion of the fixing roller tube 52 as shown in FIG. Higher than part. However, the fluctuation of the nip pressure in the longitudinal direction of the fixing roller 50 does not adversely affect the fixing property. 2B represents the nip pressure, and the horizontal axis represents the longitudinal direction of the fixing roller. Further, W1 in FIG. 2 represents an area (sheet passing area) through which the recording medium passes, and W2 represents an area pressed by the pressure roller 70. W2 is wider than W1, and the coil spring 60 is arranged over a slightly larger area than W2.
[0042]
As described above, the coil spring 60 extends in the longitudinal direction of the fixing roller tube 52 while being spirally wound around the hollow portion of the fixing roller tube 52, and contacts the inner peripheral surface of the fixing roller tube 52 to contact the inner peripheral surface. Is pressed outward. The coil spring 60 is spirally wound, and the winding directions are opposite to each other at the central portion 60a of the spiral. In other words, the coil spring 60 has the spiral winding directions opposite to each other at the center in the longitudinal direction of the fixing roller tube 52 (which is an example of a predetermined position in the longitudinal direction according to the present invention). When the coil spring 60 is inserted into the hollow portion of the fixing roller tube 52, the central portion 60 a of the coil spring is positioned at the center portion in the longitudinal direction of the fixing roller tube 52.
[0043]
Further, the coil spring 60 has a downstream portion in the rotational direction (for example, 60c) in which the upstream portion (for example, a portion indicated by 60b) of the fixing roller tube 52 in the rotational direction of the coil spring 60 is continuous with the upstream portion in the rotational direction. The fixing roller tube 52 is wound spirally so as to be located on the center side in the longitudinal direction of the fixing roller tube 52 with respect to the portion (shown). Accordingly, the coil spring 60 rotates in the direction of arrow E as the fixing roller tube 52 rotates.
[0044]
As shown in FIG. 4, the recording medium P is sandwiched between the fixing roller 50 and the pressure roller 70 (see FIG. 1) so that the central portion in the width direction of the recording medium P is positioned at the central portion 60a of the coil spring 60. However, when transporting in the direction of arrow F, the portion with high nip pressure (for example, 60b and 60c) moves on the surface of the recording medium P from the longitudinal center of the fixing roller 50 toward the longitudinal end. . For this reason, the recording medium P is conveyed in the direction of arrow F while being pulled in the direction of arrow G1 with the width direction one end being pulled in the direction of arrow G2, with the width direction center portion being the boundary. As a result, the recording medium P is difficult to skew and is transported so as not to be wrinkled.
[0045]
In the above example, one continuous coil spring 60 is used, but a plurality of coil springs shorter than the fixing roller tube 52 may be joined together to form the coil spring 60.
[0046]
Another example of the fixing roller will be described with reference to FIG.
[0047]
FIG. 5 is a perspective view showing the inside of another example of a fixing roller cut in the longitudinal direction.
[0048]
The fixing roller 150 (an example of a roller unit according to the present invention) includes a pipe-shaped (hollow cylindrical) fixing roller tube 152 (an example of a cylindrical roller according to the present invention) made of an alloy of aluminum and magnesium. I have. The outer diameter of the central portion in the longitudinal direction of the fixing roller tube 152 is smaller by about 0.15 mm than the outer diameter of both ends in the longitudinal direction. For this reason, the fixing roller tube 152 has an inverted crown shape. Further, the thickness of the fixing roller tube 152 in the longitudinal center is 0.30 mm, and the thickness at both longitudinal ends is 0.35 mm. A release layer (not shown) is formed on the outer peripheral surface of the fixing roller tube 152. This release layer is a fluororesin having high releasability, oil-impregnated silicone rubber, or a silicone rubber layer having a fluororesin layer formed on the surface thereof.
[0049]
On the inner peripheral surface 152 a of the fixing roller tube 152, a rib 154 that is spirally wound and extends in the longitudinal direction of the fixing roller tube 152 is formed. The rib 154 protrudes inward from the inner peripheral surface 152a. The fixing roller tube 152 is reinforced by the rib 154, and the fixing roller tube 152 is not deformed even when the pressure roller 70 (see FIG. 1) presses the fixing roller 150.
[0050]
The rib 154 is spirally wound, and the winding directions are opposite to each other at the central portion 154a of the spiral. The rib 154 includes a downstream portion (for example, a rotation direction downstream portion (for example, a portion indicated by 154b) of the rib 154 in the rotation direction (arrow H direction) of the fixing roller tube 152 (for example, a portion indicated by 154b). It is wound spirally so as to be located closer to the center in the longitudinal direction of the fixing roller tube 152 than the portion 154c.
[0051]
As shown in FIG. 4, the recording medium P is sandwiched between the fixing roller 150 and the pressure roller 70 (see FIG. 1) so that the central portion in the width direction of the recording medium P is positioned at the central portion 154 a of the rib 154. However, when the sheet is conveyed in the direction of arrow F, the portion with a high nip pressure (for example, 154b and 154c) moves on the surface of the recording medium P from the center in the longitudinal direction of the fixing roller 150 toward the end in the longitudinal direction. . Further, the fixing roller tube 152 has a reverse crown shape. Accordingly, the recording medium P is conveyed in the direction of the arrow F while being pulled in the direction of the arrow G1 and the other end in the direction of the width is pulled in the direction of the arrow G2 with the central portion in the width direction as a boundary. As a result, the recording medium P is difficult to skew and is transported so as not to be wrinkled.
[0052]
Still another example of the fixing roller will be described with reference to FIG.
[0053]
FIG. 6 is a perspective view showing the inside of a fixing roller of still another example cut in the longitudinal direction.
[0054]
The fixing roller 250 (an example of a roller unit according to the present invention) includes a pipe-shaped (hollow cylindrical) fixing roller tube 252 (an example of a cylindrical roller according to the present invention) made of an alloy of aluminum and magnesium. I have. The fixing roller tube 252 is cut so that its thickness is 0.28 to 0.32 mm over the entire area. A release layer (not shown) is formed on the outer peripheral surface of the fixing roller tube 252. This release layer is a fluororesin having high releasability, oil-impregnated silicone rubber, or a silicone rubber layer having a fluororesin layer formed on the surface thereof.
[0055]
In the hollow portion of the fixing roller tube 252 (inside the fixing roller 250), two coil springs 260 and 262 (an example of the two helical wires according to the present invention) wound spirally are arranged. Has been. Each of the coil springs 260 and 262 is made of a stainless steel wire. Each coil spring 260, 262 is about half the length of the fixing roller tube 252, and each coil spring 260, 262 is equal in length. Therefore, the ends of the two coil springs 260 and 262 are in contact with each other at the center portion in the longitudinal direction of the fixing roller tube 252.
Further, the outer diameter of each of the coil springs 260 and 262 is about 0.1 mm to 0.5 mm larger than the inner diameter of the fixing roller tube 252. For this reason, the coil springs 260 and 262 are in contact with an inner wall surface 252a (which is an example of an inner circumferential surface referred to in the present invention) surrounding the hollow portion of the fixing roller tube 252, and push the inner wall surface 252a outward ( Pressing). The coil springs 260 and 262 are fixed to the fixing roller tube 252 and rotate together with the fixing roller tube 252.
[0056]
When manufacturing the fixing roller 250 described above, two coil springs 260 and 262 having an outer diameter larger by 0.1 mm to 0.5 mm than the inner diameter of the fixing roller tube 252 as described above are prepared. The coil spring 260 is inserted into the hollow portion from one end in the longitudinal direction of the fixing roller tube 252 in a state where both ends in the longitudinal direction of the coil spring 260 are twisted in the diameter reducing direction (the direction in which the winding is tight, the direction in which the outer diameter is reduced). After the insertion is completed, the twist of the coil spring 260 is released. Subsequently, the remaining one end of the coil spring 262 is inserted into the hollow portion from the other end in the longitudinal direction of the fixing roller tube 252 in a state where both ends in the longitudinal direction are twisted in the diameter reducing direction. After the insertion is completed, the twist of the coil spring 262 is released. Thereby, the outer peripheral surface of each coil spring 260,262 contacts the inner wall surface 252a and pushes the inner wall surface 252a outward. Since the fixing roller tube 252 is reinforced by the coil springs 260 and 262 as described above, the fixing roller tube 252 does not deform even when the pressure roller 70 (see FIG. 1) presses the fixing roller 250.
[0057]
As described above, each of the coil springs 260 and 262 extends in the longitudinal direction of the fixing roller tube 252 while being spirally wound in the hollow portion of the fixing roller tube 252, and contacts the inner peripheral surface of the fixing roller tube 252. The inner peripheral surface is pressed outward. The coil springs 260 and 262 are spirally wound, but their winding directions are opposite to each other. In other words, the coil springs 260 and 262 are opposite to each other in the spiral winding direction at the center in the longitudinal direction of the fixing roller tube 252 (the contact portion of the coil springs 260 and 262).
[0058]
Further, each coil spring 260, 262 is a rotation in which the upstream portion in the rotation direction of the fixing roller tube 252 (for example, the portion indicated by 260a, 262a) of the coil springs 260, 262 continues to the upstream portion in the rotation direction. It is spirally wound so as to be positioned on the center side in the longitudinal direction of the fixing roller tube 252 with respect to the downstream side portion (for example, portions indicated by 260b and 262b). Accordingly, as the fixing roller tube 252 rotates in the arrow H direction, the coil springs 260 and 262 also rotate in the arrow H direction.
[0059]
As shown in FIG. 4, recording is performed by the fixing roller 250 and the pressure roller 70 (see FIG. 1) so that the central portion in the width direction of the recording medium P is positioned at a contact portion between the two coil springs 260 and 262. When transporting in the direction of arrow F while pinching the medium P, the portion with high nip pressure (for example, 260a, 262a, 260b, 262b) passes the surface of the recording medium P from the longitudinal center to the longitudinal end of the fixing roller 250. It will move toward the department. Accordingly, the recording medium P is conveyed in the direction of the arrow F while being pulled in the direction of the arrow G1 and the other end in the direction of the width is pulled in the direction of the arrow G2 with the central portion in the width direction as a boundary. As a result, the recording medium P is difficult to skew and is transported so as not to be wrinkled.
[0060]
In each of the above examples, the fixing roller tubes 52, 152, and 252 are made of aluminum and a magnesium alloy. However, the fixing roller is made of any one of these materials or a composite material of steel and both inorganic materials and organic materials. A tube may be made. The coil springs 60, 260, 262 are not limited to stainless steel. The thickness of the fixing roller tube 52, 152, 252 is not limited to the above example. Further, the number of turns of the coil springs 60, 260, 262 is not limited to the above example.
[0061]
【The invention's effect】
As described above, in the first roller unit of the present invention, the cylindrical roller is reinforced from the inside because the inner peripheral surface of the cylindrical roller is pressed (pressed) outward by the helical wire. ing. For this reason, even if a force acts on the outer peripheral surface of the cylindrical roller from the outside, the cylindrical roller is hardly deformed. Moreover, the outer peripheral surface on the opposite side of the part where the wire is in contact with the inner peripheral surface of the cylindrical roller is pressed more strongly than the outer peripheral surface on the opposite side of the part where the wire is not in contact. For this reason, when the recording medium is transported while being sandwiched between the cylindrical roller and another roller, for example, the sandwiching pressure (nip pressure) moves as the cylindrical roller rotates. In this case, since the spiral winding directions are opposite to each other at a predetermined position in the longitudinal direction of the cylindrical roller, the recording medium being conveyed is difficult to skew. As a result, good transportability can be obtained.
[0062]
Here, in the case where the spiral winding direction of the wire rod is opposite to each other with the central portion in the longitudinal direction of the cylindrical roller as a boundary, for example, a recording medium is formed between the cylindrical roller and another roller. When transporting while pinching, since the spiral winding directions are opposite to each other at the longitudinal center of the cylindrical roller, skewing can be prevented more reliably.
[0063]
Further, in the wire, the upstream portion of the wire in the rotation direction of the cylindrical roller is positioned closer to the central portion in the longitudinal direction of the cylindrical roller than the downstream portion in the rotation direction continuous to the upstream portion in the rotation direction. In the case where the recording medium is wound spirally, for example, when the recording medium is transported while being sandwiched between the cylindrical roller and another roller, the portion with the high sandwiching pressure (nip pressure) is cylindrical. As the roller rotates, the cylindrical roller moves from the longitudinal center to the longitudinal end. For this reason, since the recording medium being conveyed is conveyed so as to extend in the longitudinal direction of the cylindrical roller, the recording medium does not wrinkle.
[0064]
Furthermore, the wire rod is formed by joining a plurality of spiral wire rods shorter than the cylindrical roller that are in contact with the inner circumferential surface of the cylindrical roller and press the inner circumferential surface outward. Even if the length of the cylindrical roller is changed, the wire can be formed by appropriately joining the helical wire according to the changed length.
[0065]
Furthermore, when the wire is made of an elastic material, the wire is elastically deformed according to an external force, so that a long-life roller unit can be obtained.
[0066]
Moreover, in the 2nd roller unit of this invention, since the internal peripheral surface of the cylindrical roller is pressed outside by the wire (it is pressed), the cylindrical roller is reinforced from the inside. For this reason, even if a force acts on the outer peripheral surface of the cylindrical roller from the outside, the cylindrical roller is hardly deformed. In addition, the outer peripheral surface on the opposite side (back side) of the inner peripheral surface of the cylindrical roller that is in contact with the wire is more strongly pressed outward than the outer peripheral surface on the opposite side of the portion that is not in contact with the wire. Yes. For this reason, when the recording medium is transported while being sandwiched between the cylindrical roller and another roller, for example, the sandwiching pressure (nip pressure) moves as the cylindrical roller rotates. In this case, since the spiral winding directions are opposite to each other at a predetermined position in the longitudinal direction of the cylindrical roller, the recording medium being conveyed is difficult to skew. As a result, good transportability can be obtained.
[0067]
Here, each of the two helical wires has a cylindrical shape in which the upstream portion in the rotational direction of the cylindrical roller of the helical wire is continuous with the downstream portion in the rotational direction continuous with the upstream portion in the rotational direction. In the case of being wound spirally so as to be located on the center side in the longitudinal direction of the roller, for example, when the recording medium is transported while being sandwiched between the cylindrical roller and another roller, this clamping pressure ( A portion having a high nip pressure moves from the longitudinal center of the cylindrical roller toward the longitudinal end as the cylindrical roller rotates. For this reason, since the recording medium being conveyed is conveyed so as to extend in the longitudinal direction of the cylindrical roller, the recording medium does not wrinkle.
[0068]
In the third roller unit of the present invention, the inner peripheral surface of the cylindrical roller is reinforced by a spiral rib. For this reason, even if a force acts on the outer peripheral surface of the cylindrical roller from the outside, the cylindrical roller is hardly deformed. Moreover, the outer peripheral surface on the opposite side (back side) of the inner peripheral surface of the cylindrical roller where the rib is formed is stronger than the outer peripheral surface on the opposite side of the portion where the rib is not formed. For this reason, when the recording medium is transported while being sandwiched between the cylindrical roller and another roller, for example, the sandwiching pressure (nip pressure) moves as the cylindrical roller rotates. In this case, since the spiral winding directions are opposite to each other at a predetermined position in the longitudinal direction of the cylindrical roller, the recording medium being conveyed is difficult to skew. As a result, good transportability can be obtained.
[0069]
Here, when the ribs have spiral winding directions that are opposite to each other at the center in the longitudinal direction of the cylindrical roller, for example, a recording medium is formed between the cylindrical roller and another roller. When transporting while pinching, since the spiral winding directions of the ribs are opposite to each other with the central portion in the longitudinal direction of the cylindrical roller as a boundary, skewing is more reliably prevented.
[0070]
Further, in the rib, the upstream portion of the rib in the rotational direction of the cylindrical roller is positioned closer to the central portion in the longitudinal direction of the cylindrical roller than the downstream portion in the rotational direction continuous to the upstream portion of the rotational direction. In the case where the recording medium is wound spirally, for example, when the recording medium is transported while being sandwiched between the cylindrical roller and another roller, the portion with the high sandwiching pressure (nip pressure) is cylindrical. As the roller rotates, the cylindrical roller moves from the longitudinal center to the longitudinal end. For this reason, since the recording medium being conveyed is conveyed so as to extend in the longitudinal direction of the cylindrical roller, the recording medium does not wrinkle.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a digital copying machine as an example of an image forming apparatus in which an embodiment of a roller unit of the present invention is incorporated.
2A is a schematic diagram showing the inside of a fixing roller, and FIG. 2B is a graph showing the nip pressure of the fixing roller in FIG. 2A.
FIG. 3 is a perspective view showing a coil spring.
4 is a cross-sectional view showing the fixing roller of FIG. 2 that is transporting recording paper.
FIG. 5 is a perspective view showing the inside of a fixing roller of another example cut in the longitudinal direction.
FIG. 6 is a perspective view showing the inside of a fixing roller of still another example cut in the longitudinal direction.
FIG. 7 is a schematic diagram illustrating a schematic configuration of a fixing device.
[Explanation of symbols]
50, 150, 250 fixing roller
52, 152, 252 Fixing roller tube
60, 260, 262 coil spring
154 Ribs

Claims (5)

A hollow cylindrical roller with an inverted crown shape ,
A wire rod that extends in the longitudinal direction of the cylindrical roller while being spirally wound in the hollow portion of the cylindrical roller and contacts the inner peripheral surface of the cylindrical roller;
The wire is
The spiral winding directions are opposite to each other at the longitudinal center of the cylindrical roller, and the upstream portion of the wire in the rotational direction of the cylindrical roller is upstream of the rotational direction. It is wound spirally so as to be located on the longitudinal direction central portion side of the cylindrical roller from the downstream side portion in the rotation direction continuous to the side portion,
When a transported member is sandwiched and transported in a nip portion between the cylindrical roller and another roller, a portion with a high nip pressure moves from the longitudinal center portion of the cylindrical roller toward the longitudinal end portion. A fixing roller characterized by that. The wire is
The fixing roller according to claim 1, wherein a plurality of helical wires shorter than the cylindrical roller that are in contact with the inner peripheral surface of the cylindrical roller are joined to each other.   The fixing roller according to claim 1, wherein the wire is made of an elastic material. A hollow cylindrical roller with an inverted crown shape ,
Two helical wires, which are shorter than the cylindrical roller, extend in the longitudinal direction of the cylindrical roller while being spirally wound in the hollow portion of the cylindrical roller and are in contact with the inner peripheral surface of the cylindrical roller. With the combined wire,
These two short spiral wires have the spiral winding directions opposite to each other, and the upstream portion of the spiral roller in the rotational direction of the cylindrical roller is upstream of the rotational direction. It is wound spirally so as to be located in the longitudinal direction central portion side of the cylindrical roller from the downstream side portion in the rotation direction continuous to the portion ,
When a transported member is sandwiched and transported in a nip portion between the cylindrical roller and another roller, a portion with a high nip pressure moves from the longitudinal center portion of the cylindrical roller toward the longitudinal end portion. A fixing roller characterized by that.   An image forming apparatus comprising the fixing roller according to claim 1.

Images