JP2005309169A - Roller unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a roller unit capable of keeping, for instance, the rigidity of a fixing roller uniform in its longitudinal direction. <P>SOLUTION: A plurality of ringlike members 80 are fitted in the hollow of a core bar 52. Each ringlike member 80 is elastic. The plurality of ringlike members 80 are arranged in the longitudinal direction of the core bar 52. The ringlike members 80 are each independent, and two adjacent ringlike members 80 are apart from each other by a specific distance L. The inside diameter D1 of the core bar 52 is slightly smaller than the outside diameter D2 of each ringlike member 80. That is, the outside diameter D2 of each ringlike member 80 is slightly larger than the inside diameter D1 of the core bar 52. Thus, the ringlike members 80 each press the internal circumferential surface 52b of the core bar 52 outward by contacting the internal circumferential surface 52b. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a roller unit that conveys a recording medium and the like while sandwiching it with another roller.

  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, laser light) to form an electrostatic latent image, and a developing roller is applied to the electrostatic latent image. The toner is supplied to form a developed image, and the 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.

  The fixing device will be described with reference to FIG.

  FIG. 6 is a schematic diagram illustrating a schematic configuration of a conventional fixing device.

  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.

  The fixing roller 120 is for heating and melting the toner 102. 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.

  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).

  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.

  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 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.

  The above-described fixing roller 120 is required to rise quickly from the viewpoint of shortening the waiting time. 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.

  Further, from the viewpoint of energy saving, it is required to reduce power consumption for keeping the fixing device 100 warm as much as possible in a standby state in which the main switch of the image forming apparatus main body is turned on. For this reason, in the standby state described above, it is necessary to completely turn off the heater 122 of the fixing device 100. When the heater 122 of the fixing device 100 is completely turned off in the standby state as described above, the thickness of the fixing roller 120 is reduced in order to bring the surface of the fixing roller 120 to a predetermined temperature almost simultaneously with the heater 122 being turned on. Therefore, it is necessary to reduce the heat capacity. For this reason, a fixing roller 120 made of a thin aluminum alloy having good thermal conductivity is often used.

  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.

  In order to solve the above problems, a technique has been proposed in which a helical coil spring 150 is inserted into the fixing roller 120 to reinforce the fixing roller 120 (see, for example, Patent Document 1).

  This technique will be described with reference to FIGS.

  FIG. 7 is a cross-sectional view showing the fixing roller into which the coil spring is inserted. FIG. 8 is a schematic view showing the coil spring that has come out of the cored bar. FIG. 9 is a cross-sectional view showing a cored bar on which a stopper is formed. FIG. 10 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. 6 are denoted by the same reference numerals.

  As shown in FIG. 7, a coil spring 150 wound in a spiral shape is inserted into the internal 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. For this reason, 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 begin to move slightly in the longitudinal direction thereof. In this case, 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 gradually moves in the direction of the arrow D to move the core. It begins to escape from the gold 124 (see FIG. 8). When the fixing roller 120 and the pressure roller 130 continue to rotate, the coil spring 150 falls off the core metal 124.

Therefore, as shown in FIG. 9, a technique has been proposed in which stoppers 124 a are formed at both longitudinal ends of the core metal 124 so that the coil spring 150 does not come out of the core metal 124.
JP-A-10-116675

  However, in the technique shown in FIG. 9, 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. . In this way, when the winding pitch of the coil spring 150 varies, the strength for reinforcing the cored bar 124 varies in the longitudinal direction of the cored bar 124, and the rigidity of the fixing roller 120 varies in the longitudinal direction. As a result, the nip pressure between the fixing roller 120 and the pressure roller 130 changes to cause a problem such that the recording medium is skewed.

  In view of the above circumstances, an object of the present invention is to provide a roller unit that can maintain the rigidity of a fixing roller uniformly in the longitudinal direction.

In order to achieve the above object, the roller unit of the present invention comprises:
(1) a hollow cylindrical roller;
(2) a plurality of ring-shaped members that are in contact with the inner peripheral surface of the cylindrical roller and press the inner peripheral surface outwardly, each being disposed at a predetermined distance from each other in the longitudinal direction of the cylindrical roller; It is characterized by comprising.

here,
(3) The ring-shaped member is formed by curving a plate-shaped member of a predetermined length and overlapping both ends in the longitudinal direction of the plate-shaped member,
(4) The width in the circumferential direction of the ring-shaped member may be uniform by overlapping the longitudinal ends of the plate-shaped member with each other.

Also,
(5) Provided with a bearing that contacts the outer peripheral surface of the cylindrical roller and rotatably supports both longitudinal ends thereof;
(6) The ring-shaped member may be arranged densely in a portion where the bearing is located in the outer peripheral surface and sparsely arranged in other portions.

  In the roller unit of the present invention, since the inner peripheral surface of the cylindrical roller is pressed outward with the plurality of ring-shaped members arranged apart from each other, each ring-shaped member does not move inside the cylindrical roller. For this reason, even if this cylindrical roller rotates in a state where pressure is applied to the outer peripheral surface of the cylindrical roller, the plurality of ring-shaped members can be maintained at a predetermined distance (predetermined pitch). As a result, the rigidity of the cylindrical roller can be kept uniform over the longitudinal direction.

  Here, the ring-shaped member is formed by curving a plate-shaped member having a predetermined length and overlapping both longitudinal ends of the plate-shaped member with each other in the longitudinal direction of the plate-shaped member. When the circumferential width of the ring-shaped member is uniform by overlapping the parts, the cylindrical roller is heated from the inside because the circumferential width of the ring-shaped member is uniform. In this case, the cylindrical roller is heated to a uniform temperature in the circumferential direction of the ring-shaped member. For this reason, temperature unevenness hardly occurs in the cylindrical roller.

  In addition, a bearing that contacts the outer peripheral surface of the cylindrical roller and rotatably supports both ends in the longitudinal direction thereof is provided, and the ring-shaped member is densely arranged in a portion of the outer peripheral surface where the bearing is located. In addition, if the other portions are arranged sparsely, even if another roller is strongly pressed against the cylindrical roller, the portion of the outer peripheral surface of the cylindrical roller where the bearing is located does not deform.

  The present invention has been realized in an electrophotographic image forming apparatus.

  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.

  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.

  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.

  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.

  A procedure for forming an image with the copying machine 10 will be described.

  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.

  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.

  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 (not shown). 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 paper discharge roller 42 and stacked on the paper discharge tray 18.

  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 conventional fixing device 100 in the fixing roller 50. The structure of the fixing roller will be described with reference to FIGS.

  FIG. 2 is a schematic view showing the fixing roller cut in the longitudinal direction. FIG. 3A is a front view showing a ring-shaped member fitted in the fixing roller of FIG. 2, and FIG. 3B is a side view.

  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 outer 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 part.

  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 52 a of the core metal 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. Note that a halogen heater (not shown) is disposed inside the cored bar 52 so that the fixing roller 50 can be heated to a predetermined temperature.

  A plurality of ring-shaped members 80 are fitted in the hollow portion of the cored bar 52 (inside the fixing roller 50). Each ring-shaped member 80 has elasticity. The plurality of ring-shaped members 80 are arranged side by side in the longitudinal direction of the cored bar 52 at a predetermined interval L. Each ring-shaped member 80 is independent, and two adjacent ring-shaped members 80 are separated from each other by a predetermined distance L.

  The inner diameter D1 of the cored bar 52 is slightly smaller than the outer diameter D2 of the ring-shaped member 80. That is, the outer diameter D2 of the ring-shaped member 80 is slightly larger than the inner diameter D1 of the cored bar 52. For this reason, each ring-shaped member 80 contacts the inner peripheral surface 52b of the cored bar 52 and presses the inner peripheral surface 52b outward. Although the pressing force is weak, the cored bar 52 is reinforced.

  The ring-shaped member 80 is formed with two hooks 82 projecting inward from two locations that are approximately 90 ° apart in the circumferential direction. When the ring-shaped member 80 is inserted into the cored bar 52 and disposed, the two hooks 82 are grasped with a tool and moved in the directions of arrows F and G so that the outer diameter D2 of the ring-shaped member 80 is reduced. In this state, the ring-shaped member 80 is inserted into the cored bar 52 and disposed at an appropriate position. Instead of the hook 82, an opening or notch may be formed in the ring-shaped member 80.

  As described above, in the fixing roller 50, the inner peripheral surface 52b of the cored bar 52 is pressed outward in a state where the plurality of ring-shaped members 80 are arranged independently of each other. Does not move inside the cored bar 52. For this reason, even if this cored bar 52 rotates in a state where pressure is applied to the outer peripheral surface 52a of the cored bar 52, the plurality of ring-shaped members 80 can maintain a state separated from each other by a predetermined distance (predetermined pitch). As a result, the rigidity of the cored bar 52 can be kept uniform over the longitudinal direction. Therefore, the surface temperature of the fixing roller 50 is prevented from becoming uneven, and image defects due to the temperature unevenness can be prevented.

  Another example of the ring-shaped member will be described with reference to FIG.

  Fig.4 (a) is a perspective view which shows the ring-shaped member of another example, (b) is a front view of the ring-shaped member shown to (a), (c) is shown to (a). It is a side view of a ring-shaped member.

  The ring-shaped member 90 is formed by curving a plate-shaped member having a predetermined length and overlapping the longitudinal ends 92 and 94 of the plate-shaped member. Both end portions 92 and 94 in the longitudinal direction of the plate-like member are thinner than the central portion 96, and the same width as the central portion 96 is obtained by overlapping the both end portions 92 and 94 in the longitudinal direction. As a result, the circumferential width of the ring-shaped member 90 is uniform.

  The ring-shaped member 90 is formed with two hooks 98 projecting inward from two locations separated by about 30 ° in the circumferential direction. When the ring-shaped member 90 is inserted into the cored bar 52 and disposed, the two hooks 98 are grasped with a tool and moved in the directions of arrows H and I, and the outer diameter D3 of the ring-shaped member 90 is set to the cored bar 52. In this state, the ring-shaped member 90 is inserted into the cored bar 52 and disposed at an appropriate position. Instead of the hook 98, an opening or notch may be formed in the ring-shaped member 90.

  As described above, since the width in the circumferential direction of the ring-shaped member 90 is uniform, when the core metal 52 is heated from the inside, the core metal 52 has a uniform temperature in the circumferential direction of the ring-shaped member 90. Heated. For this reason, temperature unevenness is less likely to occur in the fixing roller 50.

  With reference to FIG. 5, another example of the arrangement method of the ring-shaped member 80 will be described.

  FIG. 5 is a schematic diagram showing the fixing roller cut in the longitudinal direction. In this figure, the same components as those shown in FIG. 2 are denoted by the same reference numerals.

  The fixing roller 250 is provided with a bearing 252 that contacts the outer peripheral surface 52 a of the core metal 52 and rotatably supports both longitudinal ends of the core metal 52. The bearing 252 is disposed at a position (outside the sheet passing area) that is out of the sheet passing area (area through which the recording medium passes).

  In the hollow portion of the cored bar 52 (inside the fixing roller 250), a plurality of ring-shaped members 80 are arranged separately from each other. The plurality of ring-shaped members 80 are densely arranged in the portion where the bearing 252 is located in the outer peripheral surface 52a, and are sparsely arranged in other portions. The interval between the densely arranged ring-shaped members 80 is L1, the interval between the sparsely arranged ring-shaped members 80 is L2, and L2 is longer than L1.

  Even if the core roller 52 is strongly pressed against the bearing 252 by the pressure roller 70 (see FIG. 1) being strongly pressed against the fixing roller 250, the plurality of closely arranged ring-shaped members 80 are in the longitudinal direction of the core metal 52. Since both ends are sufficiently reinforced, both ends in the longitudinal direction of the cored bar 52 are not deformed. Accordingly, the distance L1 is such that both ends in the longitudinal direction of the cored bar 52 are not deformed due to the bearing 252.

  Even if the pressure roller 70 is pressed more strongly against the fixing roller 250 in order to rotate the fixing roller 250 and the pressure roller 70 quickly to increase the image formation speed, a plurality of densely arranged as described above. Since the ring-shaped member 80 sufficiently reinforces both ends in the longitudinal direction of the cored bar 52, both ends in the longitudinal direction of the cored bar 52 are not deformed.

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. 3 is a schematic diagram showing the fixing roller cut in the longitudinal direction. (A) is a front view which shows the ring-shaped member engage | inserted inside the fixing roller of FIG. 2, (b) is a side view. (A) is a perspective view which shows the ring-shaped member of another example, (b) is a front view of the ring-shaped member shown to (a), (c) is the ring shape shown to (a). It is a side view of a member. FIG. 6 is a schematic view showing a fixing roller of another example cut in the longitudinal direction. FIG. 10 is a schematic diagram illustrating a schematic configuration of a conventional fixing device. It is sectional drawing which shows the fixing roller in which the coil spring was inserted. It is a schematic diagram which shows the coil spring which came out of the metal core. It is sectional drawing which shows the metal core in which the stopper was formed. It is sectional drawing which shows the coil spring from which the winding pitch fluctuated.

Explanation of symbols

50, 250 Fixing roller 52 Core metal 52a Core metal outer peripheral surface 52b Core metal inner peripheral surface 80, 90 Ring-shaped member 252 Bearing

Claims (3)

A hollow cylindrical roller;
A plurality of ring-shaped members which are in contact with the inner peripheral surface of the cylindrical roller and press the inner peripheral surface outward, and are each arranged at a predetermined distance from each other in the longitudinal direction of the cylindrical roller. A roller unit characterized by that. The ring-shaped member is
It is formed by curving a plate-shaped member of a predetermined length and overlapping both ends in the longitudinal direction of the plate-shaped member,
2. The roller unit according to claim 1, wherein the circumferential width of the ring-shaped member is made uniform by overlapping both longitudinal ends of the plate-shaped member. A bearing that contacts the outer peripheral surface of the cylindrical roller and rotatably supports both longitudinal ends thereof,
The ring-shaped member is
3. The roller unit according to claim 1, wherein the roller unit is densely arranged in a portion of the outer peripheral surface where the bearing is located and sparsely arranged in other portions.

Images