JP4103987B2 - Roller unit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a roller unit including a gear that transmits a driving force from the outside.
[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 by 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]
As the above-mentioned fixing roller, a roller in which a rubber material such as silicone rubber or fluorine rubber is coated on the outer peripheral surface of a metal cylinder in which a heater is disposed is used. Such a fixing roller 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.
[0004]
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. In this way, 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 purpose, a fixing roller made of an aluminum alloy having a good thermal conductivity is used.
[0005]
In order to shorten the rise time described above, the thickness of an aluminum fixing roller has recently been reduced to about 0.8 mm. If the thickness of the fixing roller is further reduced, the fixing roller may be deformed when the recording medium is sandwiched between the fixing roller and the pressure roller (nip portion) and the developed image is fixed with heat and pressure. There is. Since the central portion in the longitudinal direction of the fixing roller is particularly easily deformed, there is a possibility that sufficient fixing performance cannot be ensured in the central portion in the longitudinal direction.
[0006]
Therefore, a technique for reinforcing the fixing roller by pressing a coil spring having an outer diameter slightly larger than the inner diameter of the fixing roller against the inner wall surface of the fixing roller has been proposed (see Japanese Patent Publication No. 2810355). In this technique, the thickness of the fixing roller can be reduced to about 0.35 mm, and the heat capacity of the fixing roller can be reduced while maintaining the strength.
[0007]
A technique for reinforcing the fixing roller with a coil spring will be described with reference to FIGS.
[0008]
FIG. 6 is a partially broken view showing an example of a conventional fixing roller. FIG. 7 is a perspective view showing a gear attached to the fixing roller of FIG. FIG. 8 is a perspective view showing a procedure for attaching the gear of FIG.
[0009]
The fixing roller 100 has a configuration in which a coil spring 104 is inserted into an inner space of a cylindrical and thin cored bar roller 102. The coil spring 104 reinforces the core metal roller 102 by pressing the inner peripheral surface of the core metal roller 102 outward. A driving gear 106 for rotating the cored bar roller 102 by an external driving force is fixed to the longitudinal end of the cored bar roller 102. In order to fix the drive gear 106, two slits (concave portions) 102a are formed at the longitudinal end portion of the cored bar roller 102. On the other hand, the drive gear 106 is formed with ribs (convex portions) 106a that fit into the slits 102a. The rib 106a of the drive gear 106 is fitted into the slit 102a of the core metal roller 102, and the drive gear 106 is fixed to the core metal roller 102 by a semicircular retaining member 108.
[0010]
[Problems to be solved by the invention]
In the fixing roller 100 described above, when the load torque applied to the core metal roller 102 is large, the slit 102a may be broken and the drive may not be transmitted. In order to obtain a load torque that does not destroy the slit 102a, it is necessary to greatly reduce the pressure applied by a pressure roller (not shown). However, when this pressure is greatly reduced, the fixing property becomes insufficient and the fixing device cannot be used. Further, since the retaining member 108 for preventing the drive gear 106 from slipping out of the core metal roller 102 is necessary, the number of parts is increased accordingly.
[0011]
In view of the above circumstances, a first object of the present invention is to provide a roller unit that prevents the thin roller from being broken. A second object is to provide a roller unit with a small number of parts.
[0012]
[Means for Solving the Problems]
In order to achieve the first object, the first roller unit of the present invention comprises:
(1) a hollow cylindrical roller;
(2) One end of the spiral 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 is the cylindrical roller. A wire fixed to one longitudinal end;
(3) It is attached to the other end in the longitudinal direction opposite to the one end in the longitudinal direction of the cylindrical roller, and includes a gear to which the other end opposite to the one end is fixed. ,
(4) The cylindrical roller also rotates when the gear rotates in a direction in which the winding diameter of the wire expands.
[0013]
here,
(5) The spiral one end of the wire rod may be fixed by being inserted into a hole formed at one end in the longitudinal direction of the cylindrical roller and detachably engaged.
[0014]
further,
(6) The gear directly transmits the driving force of the gear to the other longitudinal end of the cylindrical roller.
(7) The directly transmitted driving force may be weaker than the driving force directly transmitted from the gear to the other end of the wire.
[0015]
Furthermore,
(8) The cylindrical roller has a recess formed at the other end in the longitudinal direction.
(9) The gear may be formed with a convex portion to be fitted into the concave portion.
[0016]
Furthermore,
(10) The wire may draw the gear toward the one end in the longitudinal direction of the cylindrical roller.
[0017]
In order to achieve the second object, the second roller unit of the present invention comprises:
(11) a hollow cylindrical roller;
(12) 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. ,
(13) A gear fixed to the end of the wire at the other end in the longitudinal direction opposite to the one end in the longitudinal direction so as to be drawn toward the one end in the longitudinal direction of the cylindrical roller. It is characterized by this.
[0018]
here,
(14) The cylindrical roller has a recess formed at the other end in the longitudinal direction,
(15) The gear is formed with a protrusion into which the recess is fitted, and a hole into which an end of the wire is inserted,
(16) The wire may be drawn toward the longitudinal end of the cylindrical roller by inserting and fixing the end of the wire into the hole of the gear.
[0019]
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.
[0020]
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.
[0021]
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.
[0022]
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.
[0023]
A procedure for forming an image with the copying machine 10 will be described.
[0024]
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.
[0025]
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.
[0026]
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 and a pressure roller 70. 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.
[0027]
The fixing roller 50 will be described with reference to FIGS.
[0028]
FIG. 2 is a cross-sectional view schematically showing an example of a fixing roller employing the roller unit of the present invention. FIG. 3 is a perspective view showing one end portion of the fixing roller in FIG. 2 in the longitudinal direction. 4 is a perspective view showing the other end in the longitudinal direction of the fixing roller of FIG.
[0029]
The fixing roller 50 includes a pipe-shaped (cylindrical) roller main body 52 (an example of the cylindrical roller according to the present invention) made of aluminum having a thickness of about 0.3 to 0.5 mm. A release layer 54 is formed on the outer peripheral surface of the roller body 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.
[0030]
A spiral spring 60 (which is an example of a wire according to the present invention) is disposed in a hollow portion of the roller body 52 (inside the fixing roller 50). The coil spring 60 is in contact with an inner wall surface (an example of an inner peripheral surface referred to in the present invention) 52a surrounding the hollow portion of the roller body 52 and pushes (presses) the inner wall surface 52a outward. Here, the coil spring 60 is used as a reinforcing member that reinforces the roller body 52. However, any member may be used as long as the heat capacity is small and the reinforcing effect is high.
[0031]
When manufacturing the fixing roller 50 described above, a coil spring 60 having an outer diameter that is 1 to 2% larger than the inner diameter of the roller body 52 is prepared, and both end portions in the longitudinal direction of the coil spring 60 are arranged in a reduced diameter direction (winding The mold release layer 54 is inserted into the hollow portion of the roller body 52 formed on the outer peripheral surface in a state twisted in a tight direction and a 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.
[0032]
At one end in the longitudinal direction of the roller body 52, a circular collar 53 is formed so as to close the cylindrical opening. As shown in FIG. 3, the flange 53 is formed with an elliptical hole 53a. The coil spring 60 described above extends in the longitudinal direction of the roller body 52 while being spirally wound around the hollow portion of the roller body 52, and one end 60a of the coil spring 60 is hooked in the hole 53a. As described above, the one end 60 a of the coil spring 60 is hooked in the hole 53 a, thereby fixing the one end 60 a of the coil spring 60 to the one end in the longitudinal direction of the roller body 52. A circular hole 53b is formed at the center of the flange 53.
[0033]
A driving gear 90 (which is an example of a gear according to the present invention) is attached to the other longitudinal end of the roller body 52 opposite to the longitudinal one end, as shown in FIG. The drive gear 90 is for transmitting a driving force for rotating the roller body 52 to the roller body 52. A gear portion 92 (portion where the gear is formed) of the drive gear 90 is located outside the roller body 52. On the other hand, the fitting portion 94 (portion other than the gear portion 92) of the drive gear 90 is fitted into the roller body 52.
[0034]
As shown in FIG. 4, a key-shaped hole 94 a is formed in the fitting portion 94 of the drive gear 90. The other end 60b opposite to the one end 60a of the coil spring is pushed into the flange 94a. As a result, the other end 60 b of the coil spring 60 is fixed to the drive gear 90. Further, the drive gear 90 is pulled toward one end in the longitudinal direction of the roller main body 52 (the portion where the flange 53 is formed) by the coil spring 60. Therefore, the coil spring 60 prevents the drive gear 90 from slipping out of the roller main body 52, and other members that prevent the drive gear 90 from coming off are unnecessary.
[0035]
The drive gear 90 rotates in the direction of arrow B shown in FIG. This arrow B direction is also a direction in which the winding diameter of the coil spring 60 is increased (the outer diameter is increased). Thus, by rotating the drive gear 90 in the direction of arrow B, the winding diameter of the coil spring 60 tends to increase, and the entire coil spring 60 contacts the inner wall surface 52a of the roller body 52 so that the inner wall surface 52a is moved outward. Press on. For this reason, the driving force transmitted from the drive gear 90 to the coil spring 60 is dispersed throughout the roller body 52 and the roller body 52 rotates. As described above, the driving force of the driving gear 90 is not concentrated on a part of the roller body 52 but dispersed throughout the roller body 52. Therefore, even if the roller body 52 is thin, the roller body 52 rotates without being broken. To do. In addition, since the coil spring 60 pushes the inner wall surface 52a of the roller body 52 outward, the roller body 52 is reinforced by the coil spring 60 and its strength is increased.
[0036]
Another embodiment will be described with reference to FIG.
[0037]
FIG. 5 is a perspective view showing the other end in the longitudinal direction of the roller body and the drive gear according to another embodiment. In this figure, the same components as those shown in FIG. 4 are denoted by the same reference numerals. One end portion in the longitudinal direction of the roller body 152 has the same structure as the roller body 52 shown in FIG.
[0038]
A driving gear 190 (which is an example of a gear according to the present invention) is attached to the other longitudinal end portion of the roller body 152 (which is an example of a cylindrical roller according to the present invention). The drive gear 190 is for transmitting a driving force for rotating the roller body 152 to the roller body 152. A gear portion 192 (portion where the gear is formed) of the drive gear 190 is located outside the roller body 152. On the other hand, the fitting portion 194 of the drive gear 190 (the portion other than the gear portion 192) is fitted inside the roller body 152.
[0039]
A plurality of holes 194 a are formed in the cylindrical portion of the fitting portion 194 of the drive gear 190. The other end portion 60b of the coil spring 60 is inserted into and hooked into any of these holes 194a. As a result, the other end 60 b of the coil spring 60 is fixed to the drive gear 190, and the drive gear 190 is pulled toward one end in the longitudinal direction of the roller main body 152 (the portion where the flange 53 is formed). . Therefore, the coil spring 60 prevents the drive gear 190 from slipping out of the roller main body 152, and other members for preventing the drive gear 90 from coming off are unnecessary.
[0040]
As described above, since the drive gear 190 has a plurality of holes 194a, even if the position of the end 60b varies due to manufacturing variations of the coil spring 60, the end 60b is It can be securely inserted into the hole 194a.
[0041]
A slit 152 a extending in the direction of arrow C is formed at the other longitudinal end of the roller body 152. The slits 152a are formed one by one at positions facing each other (positions shifted by 180 ° in the circumferential direction). Further, a rib 194b (only one is shown in FIG. 5) that fits into the two slits 152a is formed in the cylindrical portion of the fitting portion 194 of the drive gear 190.
[0042]
When the drive gear 190 rotates, the driving force of this rotation is transmitted to the coil spring 60 and directly to the roller body 152 through the rib 194b and the slit 152a. In this case, the driving force transmitted directly to the roller body 152 through the rib 194b and the slit 152a is weaker than the driving force transmitted from the drive gear 190 to the coil spring 60. That is, the driving force transmitted to the coil spring 60 is stronger than the driving force via the rib 194b or the like. For this reason, the rib 194 b and the slit 152 a play an auxiliary role to transmit the driving force of the driving gear 190 to the roller body 152. Further, the driving force transmitted to the coil spring 60 is dispersed and transmitted to the roller main body 152 in the same manner as when the driving force is transmitted from the driving gear 90 to the coil spring 60. Accordingly, the driving force of the driving gear 190 is further dispersed and transmitted to the roller body 152.
[0043]
A procedure for inserting the end 60b of the coil spring 60 into one of the holes 194a will be described.
[0044]
Rather than the circumferential distance (first distance) from the slit 152a of the roller main body 152 to the end 60b of the coil spring 60, the hole 194a into which the end 60b of the coil spring 60 is inserted to the rib 194b of the drive gear 190. The hole 194a into which the end portion 60b is inserted is selected so that the circumferential distance (second distance) becomes longer. After this selection, the end 60b is pulled out in the direction of arrow C, and the end 60b is inserted into the selected hole 194a. By setting the second distance to be longer than the first distance in this way, the coil spring 60 presses the inner wall surface 152a of the roller body 152 outward. On the other hand, when the second distance is shorter than the first distance, the coil spring 60 cannot contact the inner wall surface 152a of the roller body 152. For this reason, the driving force from the driving gear 190 is not distributed to the coil spring 60, and the driving force concentrates on the slit 152a and the slit 152a is destroyed.
[0045]
In the above example, the case where the roller unit of the present invention is applied to the fixing roller has been described. However, the roller unit of the present invention can be applied to a cylindrical thin roller such as a photosensitive drum or a developing sleeve.
[0046]
【The invention's effect】
As described above, in the first roller unit of the present invention, the driving force when the gear rotates in the direction in which the winding diameter of the wire expands is transmitted to the wire since the other end of the wire is fixed to the gear. . In addition, one end of the wire is fixed to one end in the longitudinal direction of the cylindrical roller, and the driving force transmitted to the wire is dispersed throughout the wire to increase its winding diameter. Push the circumference outward. For this reason, the driving force transmitted to the wire is dispersed throughout the cylindrical roller, and the cylindrical roller rotates. Thus, since the driving force of the gear is not concentrated on a part of the cylindrical roller but dispersed throughout the cylindrical roller, even if the cylindrical roller is thin, the cylindrical roller rotates without being broken. Moreover, since the wire rod pushes the inner peripheral surface of the cylindrical roller outward, the cylindrical roller is reinforced by the wire rod, and its strength is increased.
[0047]
Here, when the one end of the spiral of the wire is fixed by being inserted into a hole formed in one end of the cylindrical roller in the longitudinal direction and detachably engaged, Can be easily fixed by inserting a wire rod into the roller. Moreover, the exchange of the wire is easy.
[0048]
Further, the gear transmits the driving force of the gear directly to the other longitudinal end of the cylindrical roller, and the directly transmitted driving force is transmitted from the gear to the other of the wire. If it is weaker than the driving force transmitted directly to the end, the gear driving force is transmitted directly to the other longitudinal end of the cylindrical roller, so that the gear driving force is further dispersed. Transmitted to the cylindrical roller.
[0049]
Furthermore, the cylindrical roller has a concave portion formed at the other end in the longitudinal direction, and the gear has a convex portion that is fitted into the concave portion. The force can be easily and directly transmitted to the other longitudinal end of the cylindrical roller.
[0050]
Furthermore, when the wire attracts the gear toward the one end in the longitudinal direction of the cylindrical roller, it is possible to prevent the gear from coming out of the cylindrical roller.
[0051]
Moreover, in the 2nd roller unit of this invention, since a wire pulls a gear toward the longitudinal direction other end part of a cylindrical roller, it can prevent that a gear slips out from a cylindrical roller. In addition, since the wire presses the inner peripheral surface of the cylindrical roller outward, the cylindrical roller is reinforced by the wire and the strength thereof is increased.
[0052]
Here, the cylindrical roller has a concave portion formed at the other end in the longitudinal direction, and the gear has a convex portion fitted into the concave portion and a hole into which an end portion of the wire is inserted. In the case where the wire rod is formed, and the end portion of the wire rod is inserted into and fixed to the hole of the gear, the gear is pulled toward one end portion in the longitudinal direction of the cylindrical roller. It is possible to simplify the configuration that prevents the toner from slipping out of the cylindrical roller.
[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 cross-sectional view schematically showing an example of a fixing roller employing the roller unit of the present invention.
3 is a perspective view showing one end portion in the longitudinal direction of the fixing roller of FIG. 2. FIG.
4 is a perspective view showing the other end portion in the longitudinal direction of the fixing roller in FIG. 2; FIG.
FIG. 5 is a perspective view showing the other end in the longitudinal direction of a roller body and a drive gear according to another embodiment.
FIG. 6 is a partially cutaway view showing an example of a conventional fixing roller.
7 is a perspective view showing a gear attached to the fixing roller of FIG. 6. FIG.
8 is a perspective view showing a procedure for attaching the gear of FIG. 7; FIG.
[Explanation of symbols]
50 Fixing Rollers 52, 152 Roller Main Body 52a Inner Wall Surface 53b Hole 60 Coil Spring 60a Coil Spring Ends 90, 190 Drive Gear

Claims (7)

A hollow cylindrical roller;
One end of the cylindrical roller 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. A fixed wire,
The cylindrical roller is attached to the other end in the longitudinal direction opposite to the one end in the longitudinal direction, and has a gear to which the other end opposite to the one end is fixed.
The roller unit is characterized in that the winding diameter of the wire is increased by the rotation of the gear, and the inner peripheral surface of the cylindrical roller is pressed outward . The one end of the wire is
The roller unit according to claim 1, wherein the roller unit is fixed by being inserted into a hole formed at one longitudinal end of the cylindrical roller and detachably engaged. The gear is
Transmitting the driving force of the gear directly to the other longitudinal end of the cylindrical roller;
The roller unit according to claim 1 or 2, wherein the directly transmitted driving force is weaker than the directly transmitted driving force from the gear to the other end of the wire. The cylindrical roller has a recess formed at the other end in the longitudinal direction,
The roller unit according to claim 3, wherein the gear is formed with a convex portion that is fitted into the concave portion. The wire is
The roller unit according to any one of claims 1 to 4, wherein the gear is pulled toward the one end in the longitudinal direction of the cylindrical roller. 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 and presses the inner peripheral surface outward;
A gear fixed to the end of the wire at the other end in the longitudinal direction opposite to the one end in the longitudinal direction so as to be drawn toward the one end in the longitudinal direction of the cylindrical roller;
The roller unit is characterized in that the winding diameter of the wire is increased by the rotation of the gear, and the inner peripheral surface of the cylindrical roller is pressed outward . The cylindrical roller has a recess formed at the other end in the longitudinal direction,
The gear is formed with a protrusion into which the recess is fitted and a hole into which an end of the wire is inserted,
7. The wire according to claim 6, wherein an end portion of the wire rod is inserted into and fixed to the hole of the gear to draw the gear toward one end portion in the longitudinal direction of the cylindrical roller. Roller unit.

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