JP3434063B2 - Fixing device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a fixing device used in an image forming portion of an electrophotographic image forming apparatus, and in particular, toner adheres to the surface of a heating roller to prevent defective fixing, offset and the like. The present invention relates to a fixing device that can be prevented.

[0002]

2. Description of the Related Art In an image forming apparatus utilizing an electrophotographic process such as a copying machine, a printer and a facsimile machine, a toner image formed on a photoconductor is transferred onto a recording sheet and then fixed by a fixing device. An image is formed by fixing the deposited toner. The fixing device is generally composed of a heating roller equipped with a heater therein and driven to rotate, and a pressure roller which is in pressure contact with the outer peripheral surface of the heating roller, and a recording paper carrying an unfixed toner image passes between both rollers. When this is carried out, the fixing is carried out by heating this while applying pressure.

Further, in order to prevent occurrence of an offset phenomenon in which a part of the toner is transferred to the surface of the heating roller when fixing the toner, oil for improving releasability is provided on the outer peripheral surface of the heating roller. A technique has also been proposed in which an oil supply roller that supplies the surface is brought into contact with the surface. Further, a technique has been proposed in which a clean roller and a blade for removing the toner adhering to the oil supply roller are arranged (Japanese Utility Model Laid-Open No. 62-186170). However, in the technique described in the above publication, the toner once attached to the oil supply roller does not all transfer to the cleaning roller and remains a little,
There is a problem that the toner is reversely transferred to the heating roller and then reversely transferred onto the recording paper. This is a phenomenon that is often seen when the fixing device starts up. The cause is that the cleaning ability of the cleaning roller is lowered while the temperature of the cleaning roller is not sufficiently raised, and as a result, a small amount of toner remains on the surface of the oil supply roller. It was discovered by the present inventor that this phenomenon is melted by the heat of the heating roller and re-transferred, and this phenomenon does not occur when the surface temperature of the cleaning roller rises.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and in a fixing device in which a cleaning roller is in contact with the outer periphery of an oil supply roller arranged on the outer periphery of a heating roller, cleaning is performed when the device is started up. An object of the present invention is to provide a fixing device capable of preventing retransfer of toner from an oil supply roller to a heating roller that occurs due to insufficient cleaning ability of the roller.

[0005]

In order to achieve the above object, the invention according to claim 1 conveys a transfer paper under pressure between a heating roller and a pressure roller which rotates in pressure contact with the outer peripheral surface of the heating roller. In the fixing device for fixing the toner image on the transfer paper, an oil supply roller that contacts the outer peripheral surface of the heating roller to supply oil, an insulating cleaning roller that contacts the outer peripheral surface of the oil supply roller, and the cleaning unit And a cleaning device for applying a charge having a polarity opposite to that of the toner to the roller , wherein the cleaning roller operates the charging device.
The feature is that the drive is continued not only in the middle but also after the stop . In the second aspect of the present invention, in viewing the cleaning roller when the surface temperature detecting means for detecting the surface temperature of the cleaning roller is provided, that the surface temperature by the surface temperature detecting means is below a predetermined value is detected characterized by comprising a control unit for controlling the charging device so as to impart a charge. In the invention according to claim 3, the heating roller
And a pressure roller that rotates in pressure contact with the outer peripheral surface of the heating roller.
The transfer paper is nipped and conveyed to the toner image on the transfer paper.
In the fixing device for fixing the
An oil supply roller that abuts and supplies oil, and the oil
Insulating cleaning roller that contacts the outer surface of the roller
And the toner polarity with respect to the cleaning roller
And a charging device for providing a reverse polarity of the charge, the by connecting the driving source to the oil supply roller with configure this drivable causes the oil supply roller and the cleaning roller contacting spaced with respect to the heating roller contact Provide a separation mechanism,
By the control unit, the said oil supply roller and the cleaning roller only during the warm-up of the fixing device is idled together is separated from the <br/> heating roller, to and the cleaning roller from the <br/> charger Control so that an electric charge is applied to the oil supply roller and the cleaner.
When the heating roller is separated from the heating roller
Are in contact with each other .

[0006]

According to the first aspect of the invention, the cleaning roller contacting the oil applying roller contacting the heating roller is made insulative, and the charging device is arranged opposite to the cleaning roller so as to apply an electric charge having a polarity opposite to that of the toner. Since the toner is adhered, the toner adhered to the surface of the oil application roller can be electrically adhered to the cleaning roller. As a result, when the temperature of the cleaning roller is low and the toner capturing ability is low, such as at the time of rising, by performing the above charging, the toner on the oil application roller can be reliably removed. According to the second aspect of the present invention, the means for detecting the temperature of the surface of the cleaning roller is provided, and the cleaning roller is charged only when the surface temperature is equal to or lower than the predetermined reference temperature to give the electric charge. The toner removal efficiency is improved and the power consumption can be saved. According to another aspect of the invention, a drive source is connected to the oil supply roller so that the oil supply roller is rotatable, and the oil supply roller and the cleaning roller are supported on a movable side plate so that the oil supply roller and the cleaning roller can move forward and backward with respect to the heating roller. In addition, since the oil supply roller and the cleaning roller are separated from the heating roller only during the warm-up of the apparatus, the charging device gives the charge and the rotational drive is performed at the same time. (Toner stain) can be prevented

[0007]

The present invention will be described in detail below. FIG. 1 is a schematic structural explanatory view of an example of a fixing device to which the present invention is applied.
A pressure roller 3 is configured to rotate in contact with the outer peripheral surface of a heating roller 1 which has a heater 2 inside and is rotatable, and an oil supply roller 4 is provided on the outer periphery of the heating roller 1. Are abutted so as to be driven to rotate. Further, at least the surface of the oil supply roller 4 is in contact with the cleaning roller 5 made of an insulating material (dielectric material) so as to rotate together, and the outer surface of the cleaning roller 5 has a charging device 6 (charging device). Corotron) is placed opposite. The oil supply roller 4 has, for example, an oil tank inside and has a structure in which the outer circumference of the oil tank is covered with a soft and porous material, and is configured to supply a necessary amount of oil when the oil tank is rotated around the heating roller. Has been done. The cleaning roller 5 is insulative, and is configured so as to contact with the outer circumference of the oil supply roller 4 and rotate together therewith to remove the toner adhering to the outer circumference of the oil supply roller 4. The cleaning roller 5 made of an insulating material may be, for example, a cored bar having an outer circumference of epichlorohydrin rubber or Si rubber having a thickness of about 3 mm integrally laminated, or a heat-resistant resin having an outer circumference of these laminated bodies. (P
FA, PTFE, polyimide, etc.) are laminated in a thickness of 10 to 20 μm.

The charging device 6 has a well-known structure in which a discharge wire is surrounded by a casing, and includes a CPU, a memory (ROM,
RAM), I / O port and the like, by the control from the control unit 10 to energize the wire for corona discharge,
The cleaning roller 5 is charged so as to have a predetermined polarity (a polarity opposite to that of the toner). For example, if the toner on the oil supply roller is positively charged, the cleaning roller 5 is charged so as to be negatively charged. Then, the surface of the cleaning roller is negatively charged, and the positive toner attached to the surface of the oil supply roller is moved to the cleaning roller 5 side which is negatively charged in potential, so that the temperature of the cleaning roller is not sufficiently raised. Can reliably remove the toner from the oil supply roller. When the toner is negatively charged, the cleaning roller is charged so as to be positively charged.

Reference numeral 7 is a temperature detecting means such as a thermistor which is in contact with the surface of the heating roller 1 to detect the temperature,
Reference numeral 8 denotes a separation claw for peeling the recording paper from the outer circumference of the heating roller. The temperature detecting means 7 notifies the surface temperature of the heating roller to the control unit 10, and the control unit controls the heat generation temperature and time of the heater 2 based on the detected surface temperature to keep the surface temperature constant. .

Next, FIG. 2 is a schematic explanatory view of a second embodiment of the present invention. The same parts as those of the first embodiment are designated by the same reference numerals, and the duplicate description will be omitted.
The structure is different in that the surface temperature detecting means 9 such as a thermistor for detecting the surface temperature is disposed and the detected temperature is output to the control unit. When the surface temperature detecting means 9 detects the surface temperature of the cleaning roller 5 and outputs the temperature data to the control unit 10, the control unit 10 holds it in the memory and compares it with the reference temperature value, and the reference temperature value has been reached. If not, a control signal is output from the CPU to the charging device 6 to discharge the charging device 6, and the cleaning roller 5 is charged to have a polarity opposite to that of the toner. As a result, when the surface temperature of the cleaning roller reaches the reference temperature value due to the heat generated from the heating roller 1, a control signal for stopping the charging is output to the charging device to stop the charging. After this,
Even if the cleaning roller is not charged specially, the surface of the cleaning roller is sufficiently heated, so that the toner on the oil application roller can be reliably captured and removed.

FIG. 3 is a schematic structural explanatory view of a third embodiment of the present invention, in which the same parts as those in the above-mentioned respective embodiments are designated by the same reference numerals and their duplicate description is omitted, but the oil coating roller 4 and the cleaning roller are shown. 5 is rotatably supported by the movable side plate 15, the heating roller 4 is independently driven by a drive source 16 such as a motor, and the movable side plate 15 and the rollers 4, 5 supported thereby are connected by a solenoid or the like. Separation mechanism 17
The feature is that it is configured so that it can be contacted and separated by

In this embodiment, the controller operates the contact / separation mechanism 17 (solenoid ON) to separate the rollers 4 and 5 from the heating roller when the power is turned on (when the cleaning roller has a low temperature). After that, the drive source 16 is operated to start the rotation of the oil applying roller 4, and the charging device 6 applies a charge having a polarity opposite to that of the toner to surely remove the toner from the oil applying roller. . When the control unit recognizes that the surface temperature of the heating roller has reached a certain set temperature and is ready for copying, a control signal is generated for the driving source 16, the contact / separation mechanism 17, and the charging device 6 to perform all operations. Turn it off. Then, the solenoid is turned off and the spring 18 moves the movable side plate 1.
5 is moved to the left in the drawing, and the roller 4 is brought into pressure contact with the heating roller 1. In the subsequent fixing operation, the toner on the surface of the oil applying roller is accurately removed without charging the cleaning roller 5.

[0013]

As described above, according to the first aspect of the invention, the cleaning roller contacting the oil applying roller contacting the heating roller is made of an insulating material (for example, the outer periphery of the cored bar is made to have a thickness of about 3 mm). It is made by laminating and integrating chlorhydrin rubber or Si rubber, or heat-resistant resin (PFA, PTFE, polyimide, etc.) is used on the outer periphery of these laminated bodies.
.About.20 .mu.m laminated structure), and a charging device (corona discharger) is arranged to face the cleaning roller so as to apply a charge having a polarity opposite to that of the toner. The toner can be forcibly adhered electrostatically to the cleaning roller. As a result, by performing the above charging when the temperature of the cleaning roller is low and the toner capturing ability is low, such as when the equipment starts up (warm up) at the start of work,
The toner on the oil application roller can be reliably removed. As a result, it is possible to prevent a situation in which the toner remaining on the oil application roller that cannot be completely removed by the cleaning roller is retransferred to the heating roller, and finally adheres to the recording paper to stain the image.

According to the second aspect of the present invention, means for detecting the temperature of the surface of the cleaning roller is provided, and the cleaning roller is charged to give an electric charge only when the surface temperature is below a predetermined reference temperature. As a result, the toner removal efficiency is improved and the power consumption can be saved. When the surface temperature is equal to or lower than the reference temperature, it means a state after the power is turned on mainly at the start of work, so that the temperature of the cleaning roller is low such as when the equipment is warmed up (when warming up) and the toner capturing ability is low. The toner on the oil application roller can be reliably removed by performing the charging when the value is low. As a result, it is possible to prevent a situation in which the toner remaining on the oil application roller that cannot be completely removed by the cleaning roller is retransferred to the heating roller, and finally adheres to the recording paper to stain the image.

According to the third aspect of the invention, a drive source is connected to the oil supply roller so that the oil supply roller is rotatable, and the oil supply roller and the cleaning roller are supported on a movable side plate and moved back and forth with respect to the heating roller. It is configured so that the oil supply roller and the cleaning roller are separated from the heating roller only while the apparatus is warming up, and the charging apparatus charges and charges the charging roller at the same time. It is possible to prevent the occurrence of image defects (toner stain) in the above.

[Brief description of drawings]

FIG. 1 is a schematic configuration explanatory view of an example of a fixing device to which the present invention is applied.

FIG. 2 is a structural explanatory view of a second embodiment of the present invention.

FIG. 3 is a structural explanatory view of a third embodiment of the present invention.

[Explanation of symbols]

1 heating roller, 2 heater, 3 pressure roller, 4 oil supply roller, 5 cleaning roller, 6 charging device, 7 temperature detecting means, 8 separation claws, 10 control section.

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G03G 15/20 105 G03G 15/20 104 G03G 15/20 109

Claims (3)

(57) [Claims] 1. A fixing device for fixing a toner image on a transfer paper by conveying the transfer paper under pressure between the heating roller and a pressure roller that rotates in pressure contact with the outer peripheral surface of the heating roller. An oil supply roller that comes into contact with the outer peripheral surface of the heating roller to supply oil, an insulating cleaning roller that comes into contact with the outer peripheral surface of the oil supply roller, and a charging device that gives the cleaning roller an electric charge having a polarity opposite to the toner polarity. And the cleaning roller is configured to operate by the charging device.
A fixing device characterized by continuing driving not only during operation but also after stopping . Wherein providing the surface temperature detecting means for detecting the surface temperature of the cleaning roller, applying a charge to see the cleaning roller when the surface temperature is detected to be below a certain value by the surface temperature detecting means The fixing device according to claim 1, further comprising a control unit that controls the charging device. 3. A heating roller and an outer peripheral surface of the heating roller.
Transfer paper is nipped and conveyed between pressure roller that rotates by pressing
The fixing device that fixes the toner image on the transfer paper.
Te, OY supplies oil in contact with the heating roller outer peripheral surface
The oil supply roller and the outer peripheral surface of the oil supply roller
An insulating cleaning roller and the cleaning roller
Charging device that applies a charge of the opposite polarity to the toner polarity
With the door, said connect the driving source to the oil supply roller with configure this drivable, provided the separation mechanism for contacting and separating the oil supply roller and the cleaning roller against the heating roller, the control unit Accordingly, the said oil supply roller and the cleaning roller only during the warm-up of the fixing device is idled together is separated from the heating roller, and the charging device wherein controlled so as to impart a charge to the cleaning roller from the Oh
The heating roller and the cleaning roller
The fixing device according to claim 1 or 2, wherein the fixing devices are in contact with each other when they are separated from each other .