JP4042843B2 - Roller unit and image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a roller unit that conveys a recording medium while being sandwiched between other rollers, and an image forming apparatus including the roller unit.
[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. 4 is a schematic diagram illustrating a schematic configuration of a conventional fixing device.
[0005]
The fixing device 100 is for making a toner (image) 102 a permanent visible image on a recording medium 104 such as recording paper. 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]
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.
[0011]
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.
[0012]
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.
[0013]
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).
[0014]
This technique will be described with reference to FIGS.
[0015]
FIG. 5 is a cross-sectional view showing the fixing roller into which the coil spring is inserted. 6 is an enlarged cross-sectional view of a part of the fixing roller of FIG. FIG. 7 is a perspective view showing a part of the fixing roller of FIG. 8 is a cross-sectional view taken along the line AA in FIG. FIG. 9 is a schematic view showing the coil spring that has come out of the cored bar. FIG. 10 is a cross-sectional view showing a cored bar on which a stopper is formed. FIG. 11 is a cross-sectional view showing a coil spring with a varying winding pitch. In these drawings, the same components as those shown in FIG. 4 are denoted by the same reference numerals.
[0016]
A coil spring 150 wound spirally is inserted into the inner space of the cored bar 124. The coil spring 150 extends in the longitudinal direction of the cored bar 124 and contacts the inner peripheral surface of the cored bar 124 to press the inner peripheral surface. Since the cored bar 124 is very thin, the pressing force received by the outer peripheral surface of the fixing roller 120 also affects the coil spring 150. When the fixing roller 120 starts to rotate and the pressure roller 130 starts to rotate, the pressed fixing roller 120 and the coil spring 150 also start to move in the longitudinal direction thereof. At this time, the movement of the fixing roller 120 is suppressed by a roller stopper (not shown). However, since the coil spring 150 is only inserted into the fixing roller 120, the coil spring 150 moves in the direction of arrow D and the cored bar 124 is moved. Begin to break out of. When the fixing roller 120 and the pressure roller 130 continue to rotate, the coil spring 150 falls off the core metal 124.
[0017]
Therefore, as shown in FIG. 10, a technique has been proposed in which stoppers 124 a are formed at both ends in the longitudinal direction of the core metal 124 so that the coil spring 150 does not come out of the core metal 124.
[0018]
[Problems to be solved by the invention]
However, in the technique shown in FIG. 10, although the coil spring 150 does not come out of the core metal 124, the coil spring 150 may move inside the core metal 124 as shown in FIG. . When the winding pitch of the coil spring 150 varies in this way, the strength for reinforcing the cored bar 124 varies in the longitudinal direction of the cored bar 124 to change the nip pressure, so that the recording medium is skewed. Arise.
[0019]
In view of the above circumstances, an object of the present invention is to provide a roller unit in which a wire does not come out and the winding pitch does not vary, and an image forming apparatus including the roller unit.
[0020]
[Means for Solving the Problems]
In order to achieve the above object, the first roller unit of the present invention comprises:
(1) a hollow cylindrical roller;
(2) a wire 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 and presses the inner peripheral surface outward; With
(3) The wire is characterized in that the winding direction of the spiral is reversed at a plurality of locations separated from each other in the wire.
[0021]
here,
(4) In the wire, a portion between one boundary of the plurality of boundaries and a boundary adjacent to the boundary may be wound by 1.5 turns or more.
[0022]
In order to achieve the above object, the second roller unit of the present invention comprises:
(5) a hollow cylindrical roller;
(6) 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 that contacts the inner peripheral surface of the cylindrical roller and presses the inner peripheral surface outward. With
(7) The wire is characterized in that a right-handed wire and a left-handed wire having opposite spiral directions are alternately and continuously formed.
[0023]
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.
[0024]
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.
[0025]
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.
[0026]
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.
[0027]
A procedure for forming an image with the copying machine 10 will be described.
[0028]
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.
[0029]
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.
[0030]
On the other hand, a recording medium such as recording paper is fed from the cassette 16 in the direction of arrow E (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 in the present invention) and a pressure roller 70. The pressure roller 70 is pressed against the fixing roller 50 by a pressure spring 72 (see FIG. 2). The recording medium is conveyed while being sandwiched between the two rollers 50 and 70, and the developed 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.
[0031]
The basic configuration of the fixing device 40 is the same as that 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.
[0032]
FIG. 2 is a perspective view showing the fixing roller. FIG. 3 is a schematic diagram showing the inside of the fixing roller.
[0033]
The fixing roller 50 includes a pipe-shaped (hollow cylindrical) cored bar 52 (an example of the cylindrical roller in the present invention) made of an alloy of aluminum and magnesium. The outer diameter of the central portion in the longitudinal direction of the cored bar 52 is smaller than the outer diameters at both ends in the longitudinal direction. For this reason, the cored bar 52 has an inverted crown shape. Since the cored bar 52 has an inverted crown shape in this way, the clamping force (the recording medium is pressed against the recording medium) at both ends in the longitudinal direction of the fixing roller 50 in the nip portion formed by the fixing roller 50 and the pressure roller 70. Force) is greater than the central portion in the longitudinal direction. Accordingly, no twist or wrinkle occurs on the recording medium conveyed while being sandwiched between the fixing roller 50 and the pressure roller 70. In addition, the diameter of the longitudinal direction both ends of the metal core 52 is larger by about 0.07 mm to 0.13 mm than the longitudinal center.
[0034]
Further, the cored bar 52 is cut so that the thickness thereof is about 0.3 to 0.4 mm over the entire region. A release layer 54 is formed on the outer peripheral surface of the cored bar 52. This release layer 54 is a fluororesin having high releasability, oil-impregnated silicone rubber, or a silicone rubber layer having a fluororesin layer formed on the surface thereof.
[0035]
A spiral spring 60 (which is an example of a wire according to the present invention) is disposed in a hollow portion of the core metal 52 (inside the fixing roller 50). The outer diameter of the coil spring 60 is about 0.1 mm to 0.5 mm larger than the inner diameter of the cored bar 52. For this reason, the coil spring 60 is in contact with an inner wall surface 52a (an example of the inner circumferential surface referred to in the present invention) 52a surrounding the hollow portion of the core metal 52 and presses (presses) the inner wall surface 52a outward. ). For this reason, the coil spring 60 rotates together with the cored bar 52. Further, stoppers 52 b are formed at both ends in the longitudinal direction of the core metal 52 so that the both ends in the longitudinal direction of the coil spring 60 are fixed so that the coil spring 60 does not come out of the core metal 52.
[0036]
The coil spring 60 is composed of right-handed winding materials 62 and 66 and a left-handed winding material 64 that are right-handed and left-handed whose spiral winding directions are opposite to each other. From the right end of the right-hand wound wire 62 (the right end in FIG. 3), the left-hand wound wire 64 continues, and from the right end of the left-hand wound wire 64, the right-hand wound wire 66 continues. That is, the coil spring 60 is formed by alternately and continuously winding right-handed wire and left-handed wire.
[0037]
The right-hand wound wire 62 and the left-hand wound wire 64 have the spiral winding directions reversed at the boundary 60a. Further, the left-hand wound wire 64 and the right-hand wound wire 66 have the spiral winding directions reversed at the boundary 60b. That is, in the coil spring 60, the spiral winding direction is reversed at a plurality of locations (here, the boundaries 60a, 60b, 60c, and 60d) separated from each other.
[0038]
Further, the right-hand wound wire 62 has a spiral shape of about 2 turns, the left-hand wound wire material 64 also has a spiral shape of about 2 turns, and the right-hand wire material 66 has a spiral shape of about 3 turns. That is, each wire 62, 64, 66 is spirally wound in 1.5 turns or more. Therefore, each wire 62, 64, 66 is strong against external force, and can maintain the strength as the coil spring 60.
[0039]
When the fixing roller 50 rotates in a certain direction while being pressed by the pressure roller 70, for example, even if the left-hand wound wire 64 tries to move in the direction of the arrow D as the fixing roller 50 rotates, the right-hand wound wire 62 remains in the reverse direction. Therefore, the movement of the left-hand wound wire 64 is suppressed. Therefore, even if the stopper 52b is not provided, the coil spring 60 does not come out of the fixing roller 50. Moreover, since the right-handed winding materials 62 and 66 and the left-handed winding material 64 cancel each other's movement, the winding pitch P of the coil spring 60 is not shifted.
[0040]
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 cored bar 52 is prepared, and the coil spring 60 is reduced in the diameter reduction direction (tightly wound). And inserted in the hollow portion of the cored bar 52 in a state twisted in the direction in which the outer diameter decreases. 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 core metal 52 is reinforced by the coil spring 60 in this way, the core metal 52 does not deform even when the pressure roller 70 presses the fixing roller 50.
[0041]
【The invention's effect】
As described above, according to the first roller unit of the present invention, when the cylindrical roller rotates in a certain direction, a portion of the wire wound in one direction is rotated as the cylindrical roller rotates. Even if it tries to move in the longitudinal direction of the cylindrical roller, the portion wound in the other direction opposite to this one direction prevents this movement. Therefore, the wire does not come out of the cylindrical roller. Further, the winding pitch of the wire does not fluctuate.
[0042]
The wire is a portion between the boundary and the boundary when the portion between one boundary of the plurality of boundaries and the boundary next to the boundary is wound more than 1.5 turns Is 1.5 turns or more, the strength as a wire can be maintained.
[0043]
Further, according to the second roller unit of the present invention, when the cylindrical roller rotates in a certain direction, for example, the right-hand wound wire moves in the longitudinal direction of the cylindrical roller as the cylindrical roller rotates. Even so, the left-handed wire prevents the right-handed wire from moving. Therefore, the wire does not come out of the cylindrical roller. Further, the winding pitch of the wire does not fluctuate.
[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.
FIG. 2 is a perspective view showing a fixing roller.
FIG. 3 is a schematic diagram showing the inside of a fixing roller.
FIG. 4 is a schematic diagram illustrating a schematic configuration of a conventional fixing device.
FIG. 5 is a cross-sectional view showing a fixing roller into which a coil spring is inserted.
6 is an enlarged cross-sectional view illustrating a part of the fixing roller of FIG.
7 is a perspective view showing a part of the fixing roller in FIG. 6. FIG.
8 is a cross-sectional view taken along the line AA in FIG.
FIG. 9 is a schematic diagram showing a coil spring that has slipped out of a cored bar.
FIG. 10 is a cross-sectional view showing a core bar on which a stopper is formed.
FIG. 11 is a cross-sectional view showing a coil spring with a varying winding pitch.
[Explanation of symbols]
50 Fixing roller 52 Core metal 60 Coil springs 60a and 60b Boundaries 62 and 66 Right-handed wire 64 Left-handed wire

Claims (4)

A hollow cylindrical roller;
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 roller unit is characterized in that the winding direction of the spiral is reversed at a plurality of locations separated from each other in the wire.   2. The wire according to claim 1, wherein a portion between one boundary of the plurality of boundaries and a boundary adjacent to the boundary is wound by 1.5 turns or more. Roller unit. A hollow cylindrical roller;
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 roller unit is characterized in that a right-handed wire and a left-handed wire whose spiral winding directions are opposite to each other are alternately and continuously formed.   An image forming apparatus comprising the roller unit according to claim 1.

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