JP2002258664A - Fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a fixing device where a specified service life can be obtained by speeding up the response to a temperature sensor of a fixing roll which has a thinner surface and higher rigidity. SOLUTION: The fixing device TS is provided with: a thin surfaced fixing roll 1 having a heating source 5 provided inside and a plurality of ribs 4 formed on the inner surface; and a press roll 8 abutted on the fixing roll 1 at a specified pressure. A toner image is thermally melted and fixed onto transfer material by passing the transfer material to which the toner image is transferred between the two rolls. A temperature sensor 9 for controlling power feed to the heating source 5 by sensing the temperature of the fixing roll 1 is installed evading the position of the ribs of the fixing roll 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device using a fixing roller used in an apparatus utilizing an electrophotographic process, such as an electrophotographic copying machine, a facsimile, and a printer.

[0002]

2. Description of the Related Art As shown in FIG.
A fixing roller 1 used in a fixing device of an electrophotographic image forming apparatus such as a facsimile has a heat generating device such as a halogen heater 5 inside the roller and presses against a pressure roller 8 to press the nip portion N. Has formed. The fixing roller 1 melts and fixes the toner T on the transfer paper P sent to the nip N by the pressure of the nip N and the radiant heat from the heat generating device.

A general configuration of a fixing roller used in such a conventional fixing device is based on a cylindrical thin-walled roller core as a base, and a fluorine film or the like is powder-coated on an outer peripheral surface thereof, fired, and released. Coated layers.

In recent years, the thickness of the roller core of the fixing roller has been required to be further reduced in order to improve the thermal conductivity. That is, it is desired to shorten the time required to reach a temperature at which fixing can be performed by reducing the thickness of the roller core metal (rise time of the fixing roller) to promote power saving of a copying machine or the like.

[0005]

However, as described above, the fixing roller needs to have high rigidity in terms of its function, and the thickness of the roller core metal cannot be reduced unnecessarily. Therefore, a plurality of ribs are formed on the inner peripheral surface of the fixing roller to achieve both thinning and high rigidity. In such a case, the rise time of the fixing roller becomes very fast, and some of them rise in temperature by 10 ° C. or more per second. When the rise time is shortened by providing the ribs as described above, the surface temperature of the fixing roller becomes higher than the set temperature if the response of the temperature sensor is slightly delayed. As this is repeated, the release layer on the surface of the fixing roller and the claw for separating the transfer paper deteriorate, resulting in a problem that a predetermined life is not obtained. SUMMARY OF THE INVENTION It is an object of the present invention to provide a fixing device capable of obtaining a predetermined life by increasing the response speed of a temperature sensor of a fixing roller capable of realizing thinner and higher rigidity.

[0006]

In order to achieve the above object, according to the present invention, there is provided a thin fixing roller having a heating source provided therein and a plurality of ribs formed on an inner surface of the fixing roller. A pressure roller which is brought into contact with the roller at a predetermined pressure, and a transfer material on which the toner image has been transferred is inserted between these two rollers, whereby the toner image is heated and melted and fused on the transfer material. A fixing device, wherein a temperature sensor that senses the temperature of the fixing roller and controls power supply to the heating source is disposed so as to avoid a rib position of the fixing roller. According to a second aspect of the present invention, there is provided an over-temperature prevention device that cuts off power supply to the heating source when a surface temperature of the fixing roller exceeds a predetermined temperature, and is disposed so as to avoid a rib position of the fixing roller. The fixing device according to claim 2, wherein: 3. The fixing device according to claim 1, wherein all the ribs are arranged in a range where the fixing roller is in contact with the pressure roller. It is. The invention according to claim 4 is the invention according to claim 1.
An image forming apparatus comprising the fixing device according to any one of claims 1 to 3.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of a fixing device according to a first embodiment of the present invention. As shown in FIG. 1, the fixing device TS includes a fixing roller 1, a heating source 5 mounted inside the fixing roller 1, a pair of bearings 6 supporting both ends of the fixing roller 1, A driving gear 7 provided on one end side for rotating and driving the fixing roller 1;
, A rotatable pressure roller 8 that contacts the fixing roller 1 at a predetermined pressure, a temperature sensor 9 such as a thermistor that senses the surface temperature of the fixing roller 1 and controls power supply to the heating source 5, and a portion close to the fixing roller 1 ( (A contact or non-contact may be provided).

The fixing roller 1 has a thin hollow cylindrical core 3 having a plurality of annular ribs 4, in this embodiment, seven ribs 4 formed on an inner surface thereof, and is formed on the surface of the core 3. And a release layer 2. Further, the fixing roller 1 is provided with a separation claw (not shown) for separating transfer paper.

The release layer 2 is made of PFA (perfluoroalkoxy), PTFE (polytetrafluoroethylene),
It consists of a mixture of PFA and PTFE, and its thickness is 10
It is formed to 30 μm.

The metal core 3 is made of a metallic material, specifically, a metal material such as an aluminum alloy, a copper alloy, iron, and stainless steel. The thickness of the portion of the core bar 3 having no rib is preferably a thin thickness of 1 mm or less, and more preferably a thin thickness of 0.6 mm or less is suitable for exhibiting the performance of speeding up the rise. As the heating source 5, a halogen lamp, electromagnetic induction heating, or the like can be used.

There are five ribs 4 formed on the inner surface of the cored bar 3 of the fixing roller 1 within a contact area between the fixing roller 1 and the pressure roller 8 and two ribs outside the contact area. Seven are formed.

In such a thin fixing roller 1 having a plurality of ribs 4, there is a difference in the thermal response of the temperature sensor 9 at the place where the rib 4 is provided or not (the place where the rib 4 is not provided has the rib 4). If the temperature sensor 9 is provided at a position where the rib 4 is located, as shown by a broken line in FIG.
When the set temperature is reached at the position where the rib 4 exists, the temperature becomes as high as X ° C. at the position where there is no rib as shown by the solid line in FIG. As this is repeated, the release layer 2 on the surface of the fixing roller and the claw for separating the transfer paper deteriorate, and a problem arises that a predetermined life cannot be obtained.

Therefore, as shown in FIG.
Are arranged at positions where there is no rib 4. That is, the fixing roller 1 is disposed close to the surface of the thin portion of the fixing roller 1. The excessive temperature rise prevention device 10 cuts off the power supply to the heating source 5 when the surface of the fixing roller 1 becomes higher than a predetermined temperature. As the excessive temperature rise prevention device 10, a temperature fuse, a thermostat or the like can be used.

According to the fixing device of the first embodiment, since the temperature sensor 9 is arranged so as to avoid the rib position of the thin fixing roller 1, the thermal response of the temperature sensor 9 is improved, and the surface of the fixing roller has a high temperature. And the problem that the release layer on the surface of the fixing roller and the claw for separating the transfer paper are deteriorated and the predetermined life is not achieved can be prevented.

As described in the first embodiment, the thermal response changes depending on the position of the rib. Therefore, in the case where the heat source runs away from heat, if the excessive temperature rise prevention device is arranged at the position where the rib is provided, the responsiveness deteriorates. When the excessive temperature rise prevention device operates in this state, as shown by the solid line in FIG. 5, the portion without ribs operates at a high temperature of Y.degree. May not be prevented. This can be prevented by the following second embodiment.

FIG. 2 is a sectional view of a fixing device according to a second embodiment of the present invention. As shown in FIG. 2, the fixing device according to the second embodiment differs from the fixing device according to the first embodiment in FIG. 1 only in that the excessive temperature rise prevention device 10 is disposed in a portion where the rib 4 is not provided. The other configuration of the second embodiment is the same as that of the first embodiment.

According to the fixing device of the second embodiment, since the excessive temperature rise preventing device 10 is disposed avoiding the rib position of the thin fixing roller 1, the thermal response of the excessive temperature rising preventing device 10 is improved. Excessive temperature rise of the transfer paper and damage to peripheral mechanisms can be reliably prevented.

When the ribs 4 are attached to the fixing roller 1, the deflection is improved. However, when seven ribs 4 (0 non-pressing portions) are attached, the deflection curve becomes a curve C as shown in FIG. Also, as shown in FIGS. 1 and 2, when seven ribs are provided and two of them are provided in the non-pressing portion, the bending curve becomes a curve B as shown in FIG. 6, which is worse than the bending of the curve C. Become. Thus, even with the same number of ribs, the amount of deflection varies depending on whether or not the ribs 4 are in the pressing portion.

Further, as shown in a third embodiment of FIG. 3 described later, a deflection curve obtained by attaching five ribs (no non-pressing portions) has seven ribs as shown by a curve A in FIG. Curve B attached
There is not much difference.

As described above, even if a rib is provided outside the area where the rib is in contact with the pressure roller, the effect of improving the deflection is small. is there. This can be prevented by the following third embodiment.

FIG. 3 is a sectional view of a fixing device according to a third embodiment of the present invention. As shown in FIG. 3, the fixing device according to the third embodiment is different from the fixing device according to the second embodiment in FIG.
The other configuration is the same as that of the second embodiment except for the point within the range of contact with the second embodiment.

According to the fixing device of the third embodiment, the rib position of the fixing roller 1 is set within a range where the fixing roller 1 and the pressure roller 8 are in contact with each other. The deflection can be effectively improved without increasing the pressure.

FIG. 7 is an explanatory diagram showing the main configuration of an image forming apparatus provided with a fixing device according to the present invention. As shown in FIG. 7, the image forming apparatus includes a photosensitive drum 21 on which an electrostatic latent image is formed, a charging roller 22 that contacts or approaches the photosensitive drum 21 to perform a charging process, 2
A developing roller 25 for applying toner to the first electrostatic latent image;
Power supply 28 for applying a DC voltage to charging roller 22
A transfer roller 26 for transferring the toner image on the photosensitive drum 21 to the transfer paper P conveyed from the paper supply unit, a cleaning device 27 for removing and collecting residual toner on the surface of the photosensitive drum 21, A fixing device TS having a surface voltmeter 24 for measuring the surface potential of the photosensitive drum 21 and the fixing roller 1 and the pressure roller 8 of the first embodiment of FIG.
And Reference numeral 23 denotes exposure such as laser light or light reflected from a document.

An image forming operation in the image forming apparatus configured as described above will be described. First, a DC voltage is supplied from a power supply 28 to the charging roller 22 that is in contact with the photosensitive drum 21 so that the charging roller 22 contacts the photosensitive drum 21.
Is uniformly charged to a high potential.

Immediately thereafter, when the surface of the photosensitive drum 21 is exposed 23, the exposed portion has a lower potential. Since the exposure 23 has a light amount distribution corresponding to the density of the image, the exposure 23 forms a potential distribution for the recorded image, that is, an electrostatic latent image on the surface of the photosensitive drum 21.

Next, when the portion on which the electrostatic latent image is formed passes the developing roller 25, toner adheres according to the level of the potential, and a toner image is formed by visualizing the electrostatic latent image. You. Next, the transfer paper P is conveyed at a predetermined timing to a portion where the toner image is formed, and overlaps the toner image. After the toner image is transferred to the transfer paper P by the transfer roller 26, the transfer paper P is separated from the photosensitive drum 21.

Next, the separated transfer paper P is conveyed through a conveyance path, is fixed by heat and pressure by the fixing roller 1 and the pressure roller 8, and is then discharged out of the apparatus. After the transfer, the surface of the photosensitive drum 21 is cleaned by the cleaning device 2.
The cleaning process is carried out by 7 and the residual charges are further erased by a residual charge erasing means (not shown) to prepare for the next image forming process.

At this time, since the fixing roller 1 having the thinned roller core is used as the fixing roller 1,
The temperature rise rate of the fixing roller 1 can be improved, the rise time can be significantly reduced, and power saving can be achieved. That is, both the warm-up time and the lighting time of the halogen heater can be reduced.

Further, since the ribs are made thin and have high rigidity, the rising of the fixing roller is quick, power can be saved, and an image forming apparatus having stable fixing performance can be obtained.

Further, since the thermal response of the temperature sensor 9 is improved, the surface of the fixing roller does not become hot, and the release layer on the surface of the fixing roller and the claw for separating the transfer paper are deteriorated to have a predetermined life. It is possible to obtain an image forming apparatus which can also prevent the problem of no image forming apparatus.

When the fixing device TS (see FIG. 2) in which the overheating preventing device 10 is disposed so as to avoid the rib position of the thin fixing roller 1 is used, the thermal responsiveness of the overheating preventing device 10 is improved. As a result, it is possible to obtain an image forming apparatus capable of reliably preventing excessive temperature rise of the transfer sheet and damage to peripheral mechanisms.

Further, when the fixing device TS in which the rib position of the fixing roller 1 is in the range where the fixing roller 1 and the pressure roller 8 are in contact with each other is used, the fixing is performed without increasing the man-hour and the cost. A fixing device capable of effectively improving the deflection of the roller 1 can be obtained. The present invention is not limited to the above embodiment. That is, various modifications can be made without departing from the gist of the present invention.

[0033]

As described above, according to the first aspect of the present invention, since the temperature sensor is disposed so as to avoid the rib position of the fixing roller, the thermal responsiveness is improved and the surface of the fixing roller becomes high in temperature. This also prevents the problem that the release layer on the surface of the fixing roller and the claw for separating the transfer paper are deteriorated and the predetermined life is not obtained. According to the second aspect of the present invention, since the excessive temperature rise prevention device is arranged avoiding the rib position of the thin fixing roller, the thermal response is improved, and the excessive rise in the temperature of the transfer paper and the damage to the peripheral mechanism are ensured. Can be prevented. According to the third aspect of the present invention, since the rib position of the fixing roller is set within a range in which the rib is in contact with the pressure roller, the bending can be effectively improved without increasing the man-hour and cost as in the related art. . Further, according to the invention of claim 4, it is possible to obtain an image forming apparatus having the effects of any one of claims 1 to 3.

[Brief description of the drawings]

FIG. 1 is a sectional view of a fixing device according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a fixing device according to a second embodiment of the invention.

FIG. 3 is a sectional view of a fixing device according to a third embodiment of the invention.

FIG. 4 is a diagram showing a difference in thermal responsiveness of a temperature sensor depending on the presence or absence of a rib.

FIG. 5 is a diagram showing a difference in thermal responsiveness of the excessive temperature rise prevention device depending on the presence or absence of a rib.

FIG. 6 is a diagram illustrating a relationship between a pressing force and a deflection amount of a fixing roller.

FIG. 7 is an explanatory diagram illustrating a main configuration of an image forming apparatus including a fixing device according to the present invention.

FIG. 8 is a diagram illustrating a fixing roller used in a conventional electrophotographic image forming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixing roller 4 Rib 5 Heat source 8 Pressure roller 9 Temperature sensor 10 Overheat prevention device TS Fixing device

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hidenori Machida 1-3-6 Nakamagome, Ota-ku, Tokyo Stock inside Ricoh Company (72) Inventor Atsushi Ishibe 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Ricoh F term (reference) 2H033 AA18 AA24 AA42 BA32 BA34 BA38 BB12 BB30 CA07 CA30 CA34 CA45 CA48 3J103 AA02 AA13 BA03 CA52 GA02 GA57 GA58 GA60 GA66 HA04 HA05 HA15 HA33 HA36 HA37 HA41 3K058 AA73 DA02 DA

Claims (4)

[Claims] A thin fixing roller having a heating source provided therein and a plurality of ribs formed on an inner surface thereof; and a pressure roller contacting the fixing roller with a predetermined pressure. A fixing device that heats and melts the toner image by fusing the transfer material onto which the toner image has been transferred between the rollers and fuses the toner image onto the transfer material. A temperature sensor for controlling the power supply of the fixing roller is arranged so as to avoid the rib position of the fixing roller. 2. A fixing device according to claim 1, wherein an excessive temperature rise prevention device for shutting off power supply to said heating source when a surface temperature of said fixing roller exceeds a predetermined temperature is arranged so as to avoid a rib position of said fixing roller. The fixing device according to claim 2, wherein 3. The fixing device according to claim 1, wherein all the ribs of the fixing roller are arranged in a range where the rib contacts the pressure roller. 4. An image forming apparatus comprising the fixing device according to claim 1.