JP2004198984A - Roller unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a roller unit which does not leave marks of a coil spring on the outer periphery of a fixing roller. <P>SOLUTION: A stainless coil spring 62 (an example of wire in this invention) which is wound in a spiral is installed in a hollow part of a core metal 52. A metal plate 64 with good heat conductivity is brought into contact with both end parts 62a and 62b in the longitudinal direction of the coil spring 62. A fan 66 blowing air to the metal plate 64 is installed in the vicinity of the metal plate 64. By having the fan 66 driven, air is blown to the metal plate 64 and the metal plate 64 is cooled. Therefore, since when the coil spring 62 is heated, the heat is conducted to the metal plate 64, the coil spring 62 is also cooled. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a roller unit that conveys a recording medium or the like while nipping it with another roller.
[0002]
[Prior art]
2. Description of the Related Art As an output device of a computer or a 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 carrier such as a photosensitive drum is irradiated with light (eg, laser) carrying image information to form an electrostatic latent image, and a developing roller is used for the electrostatic latent image. Then, a developed image is formed by supplying toner, 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 has been formed is transported to a fixing device, where the transfer image is fixed on the recording medium. The fixing device is usually provided with a fixing roller having a built-in heater and a pressure roller which is in pressure contact with the fixing roller. When fixing the transferred image on the recording medium, the transferred image is heated at a predetermined fixing temperature while being conveyed while nipping and transporting the recording medium between a fixing roller and a pressure roller, and at the same time, pressure is applied. The transferred image is fixed on the recording medium by the heating and the pressing. The recording medium on which the transfer image is fixed is discharged while being nipped by a discharge roller or the like.
[0003]
The fixing device will be described with reference to FIG.
[0004]
FIG. 8 is a schematic diagram showing a schematic configuration of a conventional fixing device.
[0005]
The fixing device 100 is for permanently visualizing the toner (image) 102 on a recording medium 104 such as recording paper. The recording medium 104 conveyed in the direction of arrow A by the conveyance unit (not shown) is guided by the fixing entrance guide 106 and enters the nip 108 between the fixing roller 120 and the pressure roller 130.
[0006]
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. The fixing roller 120 has a built-in heat source (heating element) such as a halogen lamp 122. A controller (not shown) controls the halogen lamp 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, a roller in which a fluororesin layer 126 having good releasability is coated on the outer peripheral surface of a cored bar 124 made of, for example, a pipe member made of iron or aluminum is used. The fixing roller 120 is rotated in the direction of arrow B by a driving source (not shown).
[0008]
The pressure roller 130 is for pressing the recording medium 104 against the fixing roller 120 at a predetermined pressure. As the pressure roller 130, a roller in which an outer peripheral surface of, for example, a metal core bar 132 is coated with an elastic layer 134 of, for example, silicone rubber or fluorine rubber to a predetermined thickness is used. While pressing the pressure roller 130 against the fixing roller 120 with a predetermined pressure and rotating 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 108, the toner 102 on the recording medium 104 melts at the above-mentioned fixing temperature, and the melted toner 102 is pressed against the recording medium 104 with the above-mentioned load, and 104. The recording medium 104 on which the toner 102 has been fixed is separated from the fixing roller 120 by the separation claw 142, reaches a discharge roller (not shown), and is discharged outside the apparatus by the discharge roller.
[0010]
The fixing roller 120 is required to have a quick rise 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 body is completely cooled down to when the main switch is turned on and the first copy is discharged is 30 seconds or less. This rise time is getting shorter every year.
[0011]
Further, in a standby state in which a main switch of the image forming apparatus main body is turned on, it is required to reduce power consumption for warming the fixing device as much as possible. For this reason, in the standby state, it is necessary to completely turn off the heater of the fixing device. When the heater of the fixing device is completely turned off in the standby state as described above, in order to set the fixing roller to a predetermined temperature almost simultaneously with turning on the heater, the thickness of the fixing roller is reduced to reduce its heat capacity. Need to be kept. For this reason, a fixing roller made of an aluminum alloy having good thermal conductivity is often used.
[0012]
In order to shorten the rise time, the thickness of the aluminum fixing roller 120 has recently been reduced to about 0.8 mm. When the thickness of the fixing roller 120 is further reduced, 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 by heat and pressure, the fixing The roller 120 may be deformed.
[0013]
In order to solve the above-described problem, a technique has been proposed in which a helical coil spring is inserted inside the fixing roller 120 to reinforce the fixing roller 120 (for example, see Patent Document 1).
[0014]
This technique will be described with reference to FIG.
[0015]
FIG. 9 is a cross-sectional view illustrating the fixing roller into which the coil spring is inserted. In this figure, the same components as those shown in FIG. 8 are denoted by the same reference numerals.
[0016]
A spirally wound coil spring 150 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.
[0017]
[Patent Document 1]
JP-A-10-116675
[Problems to be solved by the invention]
While an image is being formed on a recording medium by the image forming apparatus, as described above, the controller (not shown) controls the halogen lamp 122 based on the outer peripheral surface temperature measured by the thermistor 140, and 120 is maintained at a predetermined fixing temperature. Therefore, the coil spring 150 is also maintained at the predetermined fixing temperature or a temperature in the vicinity thereof.
[0019]
On the other hand, after the image has been formed on the recording medium 104, the power to the halogen lamp 122 is cut off, and the fixing roller 120 starts to cool. In this case, the core metal 124 may contract earlier than the coil spring 150 due to a difference in expansion rate between the core metal 124 and the coil spring 150. When the core metal 124 contracts earlier than the coil spring 150 in this way, the coil spring 150 strongly presses the outer peripheral surface of the core metal 124 from the inside. For this reason, in the case of the thin cored bar 124, the portion of the outer peripheral surface of the cored bar 124 where the coil spring 150 is in contact with the inner peripheral surface on the opposite side protrudes slightly outward from the other portions. . As a result, traces of the coil spring 150 may remain on the outer peripheral surface of the fixing roller 120 after the fixing roller 120 has cooled. If traces of the coil spring 150 remain on the outer peripheral surface of the fixing roller 120, a fixing failure occurs.
[0020]
In view of the above circumstances, an object of the present invention is to provide a roller unit that leaves no trace of a coil spring on the outer peripheral surface of a fixing roller.
[0021]
[Means for Solving the Problems]
In order to achieve the above object, a first roller unit of the present invention includes a hollow cylindrical roller, and a cylindrical roller that extends in the longitudinal direction of the cylindrical roller while being spirally wound around a hollow portion of the cylindrical roller. And a wire that contacts the inner peripheral surface of the shaped roller and presses the inner peripheral surface outward.
(1) A wire cooling means for cooling only the wire is provided.
[0022]
here,
(2) The wire rod cooling means includes:
(2-1) a cooling member that contacts both ends in the longitudinal direction or one end in the longitudinal direction of the wire and removes heat from the wire;
(2-2) A cooler for cooling the cooling member may be provided.
[0023]
Also,
(3) The cooler may be driven after the rotating cylindrical roller stops.
[0024]
In order to achieve the above object, a second roller unit of the present invention comprises: a hollow cylindrical roller; and a cylindrical roller extending in a longitudinal direction of the cylindrical roller while being spirally wound around a hollow portion of the cylindrical roller. And a wire that contacts the inner peripheral surface of the shaped roller and presses the inner peripheral surface outward.
(4) The wire is arranged in a heat-resistant tube.
[0025]
here,
(5) The heat-resistant tube has an air inlet formed at one end in the longitudinal direction or both ends in the longitudinal direction for sending air into the tube.
(6) A fan that feeds air from the air inlet into the tube may be provided.
[0026]
Also,
(7) The fan may be driven after the rotating cylindrical roller stops.
[0027]
BEST MODE FOR CARRYING OUT THE INVENTION
The schematic structure of an image forming apparatus in which one embodiment of the roller unit of the present invention is incorporated 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 the roller unit of the present invention is incorporated.
[0029]
On the top surface of the copying machine 10, a document pressing plate 12 having a rectangular parallelepiped shape which can be opened and closed is arranged. An image reading device 14 that reads an image recorded on a document is arranged below the document pressing plate 12. The upper surface (upper wall) of the image reading device 14 is a platen 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. At the lower part of the copying machine 10, a cassette 16 for accommodating a plurality of cut sheets is provided so as to be able to be taken in and out of the copying machine 10. A space is formed on the left side of the copying machine 10, and a discharge tray 18 on which discharged recording paper is stacked is formed.
[0031]
A procedure for forming an image in the copying machine 10 will be described.
[0032]
In order to form an image recorded on a document on a recording medium, the document pressure plate 12 is opened, and the document is placed on the upper surface of a platen glass (not shown) so that the image surface faces down. The original is pressed and fixed by the original cover 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 a laser beam, and this laser beam is applied to the photosensitive drum 22 via a scanner mirror 20a rotating at a high speed and a folding mirror 20b. The photosensitive drum 22 is uniformly charged by the charger 24, and an electrostatic latent image is formed on the photosensitive drum 22 irradiated with the laser beam. This 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 E (feeding direction) by the feed roller 28 and is transported to the transfer roller 34 by the transport 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 holding the recording medium together with the photosensitive drum 22. The recording medium on which the developed image has been transferred is guided to the fixing device 40 by the transport guide 36. The fixing device 40 includes a fixing roller 50 (an example of a roller unit according to 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 nipped by the two rollers 50 and 70, and the developed image is fixed on the recording medium. The recording medium on which the developed image has been fixed in this manner is discharged by the discharge roller 80 and stacked on the discharge tray 18.
[0035]
The basic configuration of the above-described fixing device 40 is the same as the configuration of the conventional fixing device 100 shown in FIG. The fixing device 40 differs from the fixing device 100 in a fixing roller 50. The structure of the fixing roller will be described with reference to FIGS.
[0036]
FIG. 2 is a cross-sectional view of the fixing roller cut in a longitudinal direction to show the inside thereof, and a coil spring is omitted. FIG. 3 is an explanatory diagram showing a fixing roller into which a coil spring is inserted. FIG. 4 is a side view showing both ends in the longitudinal direction of the fixing roller.
[0037]
The fixing roller 50 includes a pipe-shaped (hollow cylindrical) cored bar 52 (an example of a cylindrical roller according to the present invention) made of an alloy of aluminum and magnesium. The outer diameter of the central portion of the core bar 52 in the longitudinal direction is smaller than the outer diameter of 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 manner, the pinching force of both ends in the longitudinal direction of the fixing roller 50 in the nip formed by the fixing roller 50 and the pressure roller 70 (pressing the recording medium against the recording medium) Force) is greater than the longitudinal center. Therefore, the recording medium conveyed while being nipped between the fixing roller 50 and the pressure roller 70 does not have a warp or a wrinkle. In addition, the diameter of both ends in the longitudinal direction of the cored bar 52 is larger by about 0.07 mm to 0.13 mm than the central part in the longitudinal direction.
[0038]
A drive gear 56 for rotating the fixing roller 50 is fixed to one longitudinal end of the fixing roller 50. The drive gear 56 is connected to a drive motor (not shown) via another gear or the like. When the drive motor is driven, the drive gear 56 rotates around a rotation center shaft 58, and this rotation causes the drive gear 56 to rotate. The fixing roller 50 also rotates about the rotation center shaft 58.
[0039]
The core 52 is cut so that its thickness is about 0.3 to 0.4 mm over the entire area. Here, the thickness of the cored bar 52 is 0.4 mm, and the outer diameter of the cored bar 52 is 30 mm. A release layer 54 is formed on the outer peripheral surface of the cored bar 52. The release layer 54 is formed by forming a fluororesin layer on the surface of a fluororesin, an oil-impregnated silicone rubber, or a silicone rubber layer having a high release property.
[0040]
In a hollow portion of the cored bar 52 (inside the fixing roller 50), a halogen lamp 60 extending in alignment with the rotation center axis 58 is disposed. As shown in FIGS. 2 and 3, the halogen lamp 60 is bent at both ends in the longitudinal direction of the fixing roller 50 and deviates from the rotation center shaft 58.
[0041]
A spiral coiled stainless steel coil spring 62 (an example of a wire according to the present invention) is disposed in a hollow portion of the cored bar 52 (inside the fixing roller 50). Here, the outer diameter of the coil spring 62 is 30 mm, and the wire diameter is 1.0 mm. For this reason, the coil spring 62 contacts the inner wall surface (which is an example of the inner peripheral surface in the present invention) 52a surrounding the hollow portion of the cored bar 52 and presses (presses) the inner wall surface 52a outward. ). Further, the coil spring 62 is arranged coaxially with the core 52. Therefore, the coil spring 62 rotates together with the metal core 52 about the rotation center axis 58.
[0042]
Both ends 62a and 62b in the longitudinal direction of the coil spring 62 extend so as to coincide with the rotation center axis 58 and protrude to the outside in the longitudinal direction of the cored bar 52. At the protruding portions (both longitudinal end portions 62a and 62b of the coil spring 62), a metal plate 64 having good thermal conductivity (an example of a cooling member according to the present invention, made of copper or aluminum) is provided. It is fixed in contact.
[0043]
In the vicinity of the metal plate 64, a fan 66 (an example of a cooler according to the present invention) that blows air to the metal plate 64 is arranged. When the fan 66 is driven, wind is sent to the metal plate 64 to cool the metal plate 64. Therefore, when the coil spring 62 is being heated, the heat is conducted to the metal plate 64, so that the coil spring 62 is also cooled. The above-described metal plate 64 and the fan 66 constitute a wire rod cooling means according to the present invention.
[0044]
By the way, while the copying machine 10 is forming an image on a recording medium, as described above, the halogen lamp 60 is controlled, and the outer peripheral surface temperature of the fixing roller 50 is maintained at a predetermined fixing temperature. Therefore, the coil spring 62 is also maintained at the predetermined fixing temperature or a temperature in the vicinity thereof. On the other hand, after the image has been formed on the recording medium, the power supply to the halogen lamp 60 is cut off, and the fixing roller 50 starts to cool. In this case, the core metal 52 contracts faster than the coil spring 62 due to the difference in the expansion rate between the aluminum core metal 52 and the stainless steel coil spring 62. When the core bar 52 contracts earlier than the coil spring 62 in this way, the coil spring 62 strongly presses the outer peripheral surface of the core bar 52 from the inside. Therefore, in the thin cored bar 52, the portion of the outer peripheral surface of the cored bar 52 where the coil spring 62 is in contact with the inner peripheral surface on the opposite side protrudes slightly outward from the other portions. As a result, the mark of the coil spring 62 may remain on the outer peripheral surface of the fixing roller 50 after the fixing roller 50 has cooled.
[0045]
Therefore, in the present embodiment, when the energization of the halogen lamp 60 is stopped and the fixing roller 50 is stopped and cooling is started, the fan 66 is driven to cool the metal plate 64 to force the coil spring 62 to forcibly. Then, the coil spring 62 contracts faster than the cored bar 52. As a result, the coil spring 62 does not strongly press the outer peripheral surface of the cored bar 52 from the inside, so that after the fixing roller 50 cools, no trace of the coil spring 62 remains on the outer peripheral surface of the fixing roller 50.
[0046]
Another technique for forcibly cooling the coil spring 62 will be described with reference to FIGS.
[0047]
FIG. 5 is a cross-sectional view showing the inside of the fixing roller cut in the longitudinal direction. 6A is a cross-sectional view taken along the line CC of FIG. 5, and FIG. 6B is a plan view showing one end of the fixing roller in the longitudinal direction. FIG. 7A is an explanatory view showing one longitudinal end of the coil spring, and FIG. 7B is a side view showing the fixing roller of FIG. 5. In these figures, the same components as those shown in FIGS. 2 to 4 are denoted by the same reference numerals.
[0048]
The coil spring 62 inserted inside the fixing roller 90 is covered with a heat-resistant tube 92. For this reason, the coil spring 62 is disposed in the tube 92. As the tube 92, a fluororesin tube or a silicone rubber tube having heat resistance of 300 ° C. and an inner diameter of 2.0 mm to 10.0 mm is used. At one end in the longitudinal direction of the tube 92, an air inlet 94a for sending air into the inside is formed. The air inlet 94a is formed in an air inlet member 94 fixed to a second joint 96b described later.
[0049]
The tube 92 and the air feeding member 94 are connected via a joint 96. The joint 96 includes a first joint 96a that rotates together with the tube 92, and a second joint 96b rotatably fixed to the first joint 96a. The second joint 96b is fixed to the air sending member 94 in which the air sending port 94a is formed. Therefore, even if the first joint 96a rotates, the second joint 96b does not rotate. The joint 96 has a hole (communication hole, not shown) for communicating the tube 92 with the air feeding member 94.
[0050]
In the vicinity of the air inlet 94a, a fan 98 for sending air to the air inlet 94a is arranged. By driving the fan 98, air is fed into the tube 92 from the air inlet 94 a through the communication hole of the joint 96. Therefore, when it is desired to cool the coil spring 62, the coil spring 62 is cooled by the air sent into the tube 92.
[0051]
In this example, when the current to the halogen lamp 60 is cut off and the fixing roller 50 is stopped and cooled, the fan 98 is driven to blow air into the tube 92 to force the coil spring 62. Upon cooling, the coil spring 62 contracts faster than the cored bar 52. As a result, the coil spring 62 does not strongly press the outer peripheral surface of the cored bar 52 from the inside, so that after the fixing roller 50 cools, no trace of the coil spring 62 remains on the outer peripheral surface of the fixing roller 50.
[0052]
【The invention's effect】
As described above, in the first roller unit of the present invention, the wire in the cylindrical roller can be cooled by the wire cooling means. Therefore, when both the heated cylindrical roller and the wire are cooled, only the wire can be forcibly cooled. For this reason, when the cylindrical roller and the wire are naturally cooled, only the wire is forcibly cooled, so that the contraction of the wire is accelerated. As a result, since the contraction of the cylindrical roller is faster than the contraction of the wire and the wire does not strongly press the cylindrical roller outward, no trace of the wire is generated on the cylindrical roller.
[0053]
Here, the wire cooling means includes a cooling member that contacts both ends in the longitudinal direction or one end in the longitudinal direction of the wire and removes heat from the wire, and a cooler that cools the cooling member. In this case, the wire is forcibly cooled more reliably.
[0054]
Further, when the cooler is driven after the rotating cylindrical roller is stopped, when the cylindrical roller being heated during rotation is stopped and cooled, the wire is forcibly cooled. Is done. For this reason, the wire contracts faster than the cylindrical roller, and the wire does not strongly press the cylindrical roller outward, so that no trace of the wire is generated on the cylindrical roller.
[0055]
Further, in the second roller unit of the present invention, since the wire is disposed in the heat-resistant tube, when the cylindrical roller is heated, the heat is not easily transmitted to the wire and the wire is not easily heated. Therefore, when cooling the heated cylindrical roller, the contraction of the cylindrical roller is faster than the contraction of the wire, and the wire does not strongly press the cylindrical roller outward. Does not occur.
[0056]
Here, the heat-resistant tube has an air inlet for sending air into the inside at one end or both ends in the longitudinal direction, and the tube is connected to the tube from the air inlet. If a fan for sending air into the tube is provided, the fan can be driven to send air into the tube, so that the wire can be forcibly cooled more reliably.
[0057]
Further, when the fan is driven after the rotating cylindrical roller is stopped, the wire is forcibly cooled when stopping and cooling the cylindrical roller being heated during rotation. You. For this reason, the wire contracts faster than the cylindrical roller, and the wire does not strongly press the cylindrical roller outward, so that no trace of the wire is generated on 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 of the fixing roller cut in a longitudinal direction to show the inside thereof, in which a coil spring is omitted.
FIG. 3 is an explanatory diagram illustrating a fixing roller into which a coil spring is inserted.
FIG. 4 is a side view showing both ends in the longitudinal direction of the fixing roller.
FIG. 5 is a cross-sectional view illustrating the inside of a fixing roller cut in a longitudinal direction thereof.
6A is a cross-sectional view taken along the line CC of FIG. 5, and FIG. 6B is a plan view showing the vicinity of one longitudinal end of the coil spring.
7A is an explanatory view showing one end in a longitudinal direction of a coil spring, and FIG. 7B is a side view showing the fixing roller of FIG. 5;
FIG. 8 is a schematic diagram illustrating a schematic configuration of a conventional fixing device.
FIG. 9 is a sectional view showing a fixing roller into which a coil spring is inserted.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Copier 50, 90 Fixing roller 52 Core metal 60 Halogen lamp 62 Coil spring 64 Metal plate 66, 98 Fan 70 Pressure roller 92 Tube 94 Air feeding member 94a Air feeding port 96 Joint

Claims (6)

A hollow cylindrical roller,
A wire that extends in the longitudinal direction of the cylindrical roller while being spirally wound around 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. In the roller unit,
A roller unit comprising a wire cooling means for cooling only the wire. The wire cooling means,
A cooling member that contacts both ends in the longitudinal direction or one end in the longitudinal direction of the wire and removes heat from the wire,
The roller unit according to claim 1, further comprising a cooler for cooling the cooling member. The cooler is
The roller unit according to claim 2, wherein the roller unit is driven after the rotating cylindrical roller stops. A hollow cylindrical roller,
A wire that extends in the longitudinal direction of the cylindrical roller while being spirally wound around 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. In the roller unit,
The wire rod is
A roller unit, wherein the roller unit is disposed in a heat-resistant tube. The heat-resistant tube is
At one end in the longitudinal direction or both ends in the longitudinal direction, an air inlet for sending air into the inside is formed,
The roller unit according to claim 4, further comprising a fan that sends air from the air inlet to the inside of the tube. The fan,
The roller unit according to claim 5, wherein the roller unit is driven after the rotating cylindrical roller stops.

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