JP3939055B2 - Thermal fixing device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heat fixing device in an image forming apparatus such as a copying machine, a facsimile, a printer, and the like, and an image forming apparatus including the device .
[0002]
[Prior art]
Conventionally, in the case of an image forming apparatus such as a copying machine, a developed image (visible image) obtained by developing an electrostatic latent image formed on a photosensitive member with a developing device is transferred onto a transfer paper, Copying is performed by fixing the unfixed toner image transferred to the transfer paper by a thermal fixing device. FIG. 9 shows a conventional heat fixing device. The heat fixing device 1 includes a heat roller 2 having a halogen heater 9 therein, and pressure applied to the heat roller 2 by pressing the heat roller 2 and a spring or the like. The transfer sheet holding the unfixed toner is passed through the nip portion between the rollers 2 and 3, and the toner image is fixed on the transfer sheet by applying pressure while heating the toner. . Further, a contact-type temperature sensor 26 is provided on the surface of the heat roller 2, and the temperature sensor 26 detects the temperature of the peripheral surface of the heat roller 2, and energizes the halogen heater 9 based on the detection result. Temperature control of the entire heat roller 2 is performed.
[0003]
A plurality of separation claws 10 for preventing the transfer paper from being wound around the peripheral surface of the heat roller 2 are disposed at positions facing the peripheral surface of the heat roller 2. The separation claw 10 is rotatable about a support shaft 14, and a hook portion 13 extending upward is provided at the upper end portion of the separation claw 10. One end of the tension spring 12 (in the drawing) The right side) is installed. On the other hand, the other end (left side in the figure) of the tension spring 12 is attached to the frame portion 15. As a result, the leading end of the separation claw 10 is always in contact with the heat roller 2 side by the urging force of the tension spring 12, so that the transfer paper is prevented from being wrapped around the heat roller 2. Further, a paper jam detection sensor (not shown) such as a photo interrupter is disposed at a predetermined position in the heat fixing apparatus 1, and the paper jam of the transfer paper in the apparatus 1 is detected by this detection sensor.
[0004]
In addition to the configuration of the thermal fixing device described above, for example, in Japanese Patent Laid-Open No. 10-198216, a temperature sensor is heated from the back side of the paper on the paper discharge side with respect to the nip portion of the heat roller and the pressure roller. It is arranged to detect the surface temperature of the roller, this temperature sensor detects the surface temperature of the heat roller when the paper is not in the measurement area, and the temperature of the back side of the paper when the paper is in the measurement area It has been proposed to detect the occurrence of a paper jam by detecting the passage time of the measurement area of the paper based on the temperature difference between the detection temperatures.
[0005]
[Problems to be solved by the invention]
However, the conventional thermal fixing apparatus described above has the following problems. That is, since the temperature sensor 26 is always in sliding contact with the surface of the heat roller 2, the release layer on the surface of the heat roller 2 is worn and deteriorated, causing the durability of the heat roller 2 to decrease. It was. Further, there is a problem in that offset toner accumulates with time between the heat roller 2 and the temperature sensor 26, and an abnormal image is generated when the toner adheres to the transfer paper. For this reason, in recent years, measures have been taken to make the temperature sensor a non-contact type sensor that is not a contact type sensor. However, since the temperature inside the thermal fixing apparatus 1 is generally higher than 100 ° C., a temperature sensor is provided outside the apparatus 1. In addition, it is necessary to use a heat-resistant component as a temperature sensor or to interpose a relay actuator as a temperature sensor, which increases the component cost. Further, the conventional method has a problem that when the transfer paper is wound around the surface of the heat roller, the winding cannot be directly detected. Further, even in the case of the heat fixing device described in the above-mentioned publication, there is a problem that the temperature of the heat fixing device cannot be measured during the sheet passing.
[0006]
Further, as shown in FIG. 7 , in the case of an image (solid portion) in which toner is distributed at a high density at the leading end portion of the transfer paper P and the thin transfer paper P, the toner and the heat roller 2 It has been confirmed that the transfer paper P is easily wound around the heat roller 2 due to the viscosity of the toner. For this reason, there is a measure to prevent winding of the transfer paper by providing a so-called “non-image area” that does not adhere toner with a width of several millimeters at the leading edge of the image. When the release performance of the coat layer is lowered, there is a possibility that winding around the heat roller 2 is extremely likely to occur. At the same time, since the “separation performance” of the tip of the separation claw 10 also deteriorates due to wear, toner adhesion, etc., the transfer paper P slips between the separation claw 10 and the heat roller 2, so The transfer paper may be completely wound (see FIG. 9 ).
[0007]
As described above, when the transfer paper P is wound around the heat roller 2, the transfer paper P is completely left inside the heat fixing apparatus 1. Therefore, whether the transfer paper P remains from the outside. If it is left as it is without being noticed by the user, there is a possibility that the fixing property is deteriorated, an offset image is generated, and the wrapping transfer paper P is ignited.
[0008]
Accordingly, the object of the present invention is to eliminate the problems of the conventional heat fixing device as described above, and to eliminate the need for a contact-type temperature sensor, which is simple in structure and inexpensive, and that there is a paper jam. An object of the present invention is to provide a thermal fixing device that can accurately detect and prevent abnormal images and firing of transfer paper and the like, and can improve safety, and an image forming apparatus including the thermal fixing device.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 is a non-contact measurement of a temperature of a heat roller having a heater therein , a pressure roller, and the surface of the heat roller. In the thermal fixing device of an image forming apparatus provided with a non-contact type temperature sensor, the temperature sensor is disposed at a position facing the surface of the heat roller, and detects the temperature of the surface of the heat roller when the image forming apparatus is in operation. In addition to controlling the heater according to the result, when the transfer paper is stuck on the surface of the heat roller, it becomes possible to detect the winding of the transfer paper by the emissivity difference between the heat roller surface and the transfer paper. In the space formed in the radial direction of the temperature sensor and the heat roller, an arcuate guide plate for guiding the transfer of the transfer paper is provided along the surface of the heat roller. The plate is provided with a measurement hole so that the temperature sensor can detect the temperature of the surface of the heat roller, and a first upstream of the heat roller rotation direction upstream of the range where the temperature sensor of the guide plate detects the surface of the heat roller. The separation claw is provided in contact with the heat roller, and the second separation claw is provided in contact with the heat roller on the downstream side .
[0010]
According to a second aspect of the present invention, there is provided an image forming apparatus including the thermal fixing apparatus according to the first aspect.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
In the first embodiment of the present invention shown in FIG. 1, parts that are the same as those in the conventional example are given the same reference numerals and explanation thereof is omitted, and different parts are mainly explained. The present invention is characterized in that not only the surface temperature of the heat roller is detected by a non-contact type temperature sensor, but also the presence or absence of the transfer paper wound around the surface of the heat roller is detected by the difference in emissivity of the object to be measured. .
[0013]
Hereinafter, a first embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a perspective view of a heat fixing apparatus which is a subject of the present invention. That is, as shown in FIG. 1, the heat fixing device 1 has a heat roller 2 and a pressure roller 3, and the heat roller 2 has a halogen heater 9 for heating inside, and against the L-shaped side plate 5. The bearing 8 is rotatably supported. One end of the heat roller 2 is connected to a drive source (not shown), and is driven to rotate in the direction of the arrow in FIG. On the other hand, the pressure roller 3 is rotatably supported by a pressure bearing 6 such as a heat resistant resin so as to be movable in the central axis direction with respect to the side plate 5. A compression spring 7 is interposed between the pressure bearing 6 and the side plate 5 of the pressure roller 3, and the pressure roller 3 is pressed against the heat roller 2 side by the elasticity of the compression spring 7. 10 is a separation claw, and this separation claw 10 is rotatable about a support shaft 14. The urging force of the tension spring 12 always makes the tip of the separation claw 10 abut on the heat roller 2 side to the heat roller 2. The transfer paper is prevented from being wrapped. The number of separation claws 10 is appropriately set in accordance with the width of the transfer paper that can pass. For example, in the case of an image forming apparatus capable of passing A4 width (297 mm), about five are provided. .
[0014]
In the fixing step, the transfer paper on which a visible image is formed is conveyed from the inlet guide plate 17 of the heat fixing device 1 to the nip portion between the heat roller 2 and the pressure roller 3. The heat roller 2 is heated to a normal melting temperature of the toner, for example, about 160 to 180 ° C. by the halogen heater 9, and the toner is fixed on the transfer paper P as a permanent image by this heat and the pressure applied by the compression spring 7. . Then, the transfer paper P that has passed through the nip portion is separated from the heat roller 2 along the guide portion 11 of the separation claw 10, discharged to the outside of the apparatus 1 by the paper discharge roller 19, and discharged along the paper discharge guide plate 18. Paper is ejected by 20. Reference numeral 16 denotes a non-contact type temperature sensor 16 which is attached to an arbitrary position facing the heat roller 2, for example, above the heat roller 2 so that the temperature measurement range a is within the heat roller 2. is there. That is, if the temperature measurement range a extends to a range other than the heat roller 2, the temperature of the object other than the heat roller 2 is also measured at the same time, and the actual surface temperature of the heat roller 2 cannot be detected accurately.
[0015]
Here, there are various types of non-contact type temperature sensor 16, but in the case of a device such as a radiation thermometer or thermopile that measures the amount of infrared radiation of the object to be measured, the infrared emissivity of the object to be measured is the object. Because it depends on the emissivity, correction of the emissivity is necessary. In other words, the emissivity is 1 in the case of an ideal black body, but the emissivity of the heat roller 2 having a black release layer containing carbon or the like is about 0.9, and the emissivity is adjusted in advance accordingly. It can be measured by the temperature sensor 16 without any difference from the actual temperature. However, when the transfer paper P is completely wound around the surface of the heat roller 2, the white portion of the transfer paper P itself is measured. Since the white portion has an emissivity that is much lower than the emissivity of the heat roller 2, the measured temperature changes abruptly. Therefore, in the present invention, the procedure according to the flowchart shown in FIG. 3 is performed. That is, for example, when a temperature change of X (deg) or more is measured in one second, the CPU of the image forming apparatus main body detects “fixing abnormality” and stops the image forming apparatus. At this time, the fact that the recording sheet P is wound around the surface of the heat roller 2 is displayed on the operation panel. As another detection method, a change region of the surface temperature of the heat roller 2 is measured in advance, and when a value outside the temperature range is indicated, it is determined as “high temperature abnormality”, and the image forming apparatus is stopped to promptly A method of notifying the user so as to remove the transfer paper P wound around the sheet may be performed.
[0016]
Here, when the transfer paper P is continuously used with the transfer paper P wound around the surface of the heat roller 2, the worst case is to generate an abnormal image such as a fixing failure or an offset image as described above. The temperature of the roller 2 cannot be accurately measured and is controlled at a high temperature with respect to the set temperature, causing the release layer on the surface of the heat roller 2 to be damaged, welding of other components, or the rolled transfer paper P Since there is a risk of ignition, it is necessary to remove the recording sheet P that is securely wound. Further, even if the image forming apparatus main body is turned off without removing the transfer paper P when an abnormality occurs, the abnormality information is stored in the storage device of the image forming apparatus main body, and is recorded and held even when the power is turned on again. When the winding of the paper P is not reliably removed, the image forming apparatus may not be used.
[0017]
Here, when the heat roller 2 and the separation claw 10 are worn with time as described above, the transfer paper P that has passed through the separation claw 10 enters the unexpected space of the heat fixing apparatus 1 as shown in FIG. There is a fear. In order to prevent such a problem more reliably, a guide plate for guiding the transfer paper P is provided in the second embodiment of the present invention. That is, as shown in FIGS. 5 and 6, an arcuate guide plate 23 is provided at the outer peripheral portion of the heat roller 2 and downstream of the contact position between the heat roller 2 and the separation claw 10. This guide plate 23 not only reliably guides the transfer paper P to the space between the heat roller 2 and the temperature sensor 16 but also prevents an unexpected entry into the space. In addition, a measurement hole 24 for measurement by the temperature sensor 16 is formed in a substantially central portion of the guide plate 23, and a predetermined temperature measurement range can be measured through the measurement hole 24.
[0018]
FIG. 8 shows a third embodiment of the present invention. That is, in the third embodiment, as shown in FIG. 8 , a separation claw 25 ( second separation claw) separate from the separation claw 10 (first separation claw) is provided at the downstream end position of the guide plate 23. At least one or more is provided at an appropriate position in the longitudinal direction of the heat roller 2. By providing the separation claw 25, the transfer paper P wound around the heat roller 2 passes through the separation claw 10 and is then blocked by the separation claw 25. In this way, the transfer paper guided to the temperature measurement range of the temperature sensor 16 is reliably stopped within the predetermined temperature measurement range by the separation claw 25.
[0019]
【The invention's effect】
The invention has been described above, a first aspect of the present invention, a heat roller having a heater therein, and a pressure roller, a non-contact type for measuring the temperature in a non-contact of the heat roller surface temperature In the thermal fixing device of the image forming apparatus provided with the sensor, the temperature sensor is disposed at a position facing the surface of the heat roller, detects the temperature of the surface of the heat roller when the image forming apparatus is in operation, and the heater according to the result When the transfer paper sticks around the surface of the heat roller, it can be detected by the difference in emissivity between the heat roller surface and the transfer paper. There is an effect that the presence of a paper jam can be accurately detected by a detected temperature change of a non-contact type temperature sensor that controls the temperature of the heat roller during operation of the image forming apparatus. In addition, because the transfer paper is reliably guided to the detection range of the temperature sensor, paper jams can be easily detected, and abnormal images and firing of the transfer paper can be prevented and safety can be improved. There is an effect that can be. In addition, an arcuate guide plate for guiding the transfer paper is provided along the surface of the heat roller in a space formed in the radial direction of the temperature sensor and the heat roller. Has a measurement hole so that the temperature of the surface of the heat roller can be detected, preventing the transfer paper wrapped around the heat roller from entering the unexpected space in the fixing unit and arranging it as a residual paper detection Thus, there is an effect that the guide can be surely guided within the detection range of the non-contact type temperature sensor, and the detection rate of the remaining sheet detection can be further improved. Furthermore, a first separation claw is provided in contact with the heat roller on the upstream side in the heat roller rotation direction from the range in which the temperature sensor of the guide plate detects the heat roller surface, and the second separation on the downstream side. Since the nail is provided in contact with the heat roller, there is a high possibility that the transfer paper will be blocked within the detection range of the non-contact type temperature sensor, and the detection accuracy of the paper jam may be improved. There is an effect that can be done.
[0020]
Since the invention described in claim 2 is an image forming apparatus provided with the heat fixing device described in claim 1, the image forming apparatus can similarly expect the operational effects expected of the heat fixing device. .
[Brief description of the drawings]
FIG. 1 is a perspective view showing a first embodiment of the present invention.
FIG. 2 is a schematic longitudinal section of the main part.
FIG. 3 is a flowchart showing the functional procedure.
FIG. 4 is an explanatory diagram showing a paper jam.
FIG. 5 is a schematic longitudinal sectional view showing a second embodiment of the present invention.
FIG. 6 is an enlarged perspective view showing a guide plate.
FIG. 7 is a plan view of a transfer sheet showing a solid portion .
FIG. 8 is a schematic longitudinal sectional view showing a third embodiment of the present invention.
FIG. 9 is a schematic longitudinal sectional view showing an example of a thermal fixing apparatus using a conventional contact type temperature sensor.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Thermal fixing apparatus 2 Heat roller 3 Pressure roller 5 Side plate 6 Pressure bearing 7 Compression spring 8 Bearing 9 Halogen heater
10, 25 Separating nails
12 Tension spring
14 Support shaft
15 Frame part
16, 26 Temperature sensor
23 Guide plate
24 Measuring hole

Claims (2)

In a heat fixing device of an image forming apparatus , comprising: a heat roller having a heater therein ; a pressure roller; and a non-contact type temperature sensor that measures the temperature of the surface of the heat roller in a non-contact manner. Located at the position facing the roller surface, the temperature of the heat roller surface is detected during operation of the image forming apparatus, and the heater is controlled according to the result, and the transfer paper is stuck on the surface of the heat roller. In this case, the winding of the transfer paper can be detected by the difference in emissivity between the surface of the heat roller and the transfer paper, and the transfer of the transfer paper is guided to the space formed in the radial direction of the temperature sensor and the heat roller. An arc-shaped guide plate is provided along the surface of the heat roller, and the guide plate is provided with a measurement hole so that the temperature sensor can detect the temperature of the surface of the heat roller. The first separation claw is provided in contact with the heat roller on the upstream side in the rotation direction of the heat roller from the range in which the temperature sensor of the guide plate detects the surface of the heat roller. A heat fixing device, wherein two separation claws are provided in contact with a heat roller . An image forming apparatus comprising the heat fixing device according to claim 1.

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