JPH04316078A - Thermal fixing device - Google Patents

Abstract

PURPOSE:To attain the improvement of fixing properties and the prevention of an offset by controlling fixing conditions in consideration of the surface roughness of a transfer material, as well. CONSTITUTION:A detector 10 detecting the surface roughness of the transfer material P is provided on the upper stream position of a fixing device. First, a fixing temp. is changed when the output value of the detector 10 is a prescribed one or above. Second, the cleaning capacity of a cleaning device 7, or the oil coating quantity of an oil coating device 28 is changed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal fixing device that fixes a transfer material having an unfixed developer image by heating and conveying it under pressure using a roller or an endless belt.

0002

[Prior Art] Conventionally, in electrophotography, a toner image, which is an unfixed developer image, is formed on a transfer material such as paper by a method called the Carlson process, and then the toner image is fixed as a permanent image. Ta. Various fixing methods have been proposed, but in terms of fixability, the most common method is to fix the toner image by heating it.Among them, a method that fixes the toner image by bringing a heating element into direct contact with the toner image is the most common method. , is often used.

FIG. 6 shows an example of a heat roller fixing method, which is a typical example of such a heat fixing method. The basic configuration includes a fixing roller 18 having a heat source 20 such as a halogen lamp,
It consists of a pressure roller 19 having an elastic layer such as silicone rubber that is in pressure contact with the pressure roller 19, and when both rollers rotate and transfer material P such as paper is conveyed under pressure between the rollers, the toner image T is thermally melted. After exiting the pair of rollers, the image is cooled and forms a fixed image.

[0004] In a method such as this hot roller fixing method in which a heating body comes into direct contact with a toner image, a so-called offset phenomenon occurs in which a portion of the toner image adheres to the heating body during thermal melting. Therefore, in many cases, in order to reduce the offset, a release agent such as silicone oil is applied or a cleaning means is provided to remove the offset toner. In this example, a release agent application means 35 and a cleaning means 36 are also provided. Note that it is not essential to use both methods together.

[0005] The fixing temperature of the heat source 20 is set so as to satisfy fixing performance in a low temperature environment. However, since the set temperature is set simply by taking into account low-temperature environments, if the thickness, material (pulp paper, Mylar paper, etc.) or size of the transfer material differs, the heat capacity of the transfer material will also differ, causing the transfer Some materials did not satisfy the fixation properties.

Therefore, in order to compensate for this drawback, the thickness, material, and size of the transfer material are detected by appropriate detection means before the transfer material enters the heat fixing device, and the Some devices are designed to set the fixing temperature depending on the information.

[0007]

Problems to be Solved by the Invention In such a heat fixing method, fixing performance and offset amount are influenced by various factors. Among them, the influence of transfer materials is large. For example, generally speaking, if the transfer material (paper) is thick, it will be difficult to fix because of its large heat capacity, and if it is thin, it will be easy to fix. For this reason, it has been proposed to detect the thickness and weight of the transfer material and change the fixing conditions. However, when we actually investigated it, we found that even papers of the same thickness and weight may have different fixing properties and offsets. It was also discovered that even if the paper is the same, the fixing properties and offset are different on the front and back sides of the paper. Furthermore, it has been confirmed that even if the fixing properties on the front and back sides of the paper are made the same, there may still be a difference in offset.

In other words, it has been concluded that simply detecting the thickness and weight of the paper is not sufficient to prevent the offset phenomenon even if fixing performance can be maintained.

Another object of the present invention is to change the fixing conditions in consideration of the surface shape of the transfer material, thereby achieving sufficient fixing performance and preventing the offset phenomenon.

0010

[Means for Solving the Problems] As a result of studying the above-mentioned development, the present inventors discovered that the surface shape of the transfer material, particularly its roughness, has a large effect on the fixability and the amount of offset.

According to the present invention, the above-mentioned object is achieved by heating and pinching a transfer material having an unfixed developer image on a roller or an endless belt and conveying the unfixed developer image on the transfer paper according to the first invention. A thermal fixing device for fixing a developer image has a detection means for detecting the surface shape of the transfer paper, and the fixing temperature is variable according to the output value of the detection means, Fixing properties can be improved.

Further, according to the present invention, according to the second invention, a transfer material having an unfixed developer image is heated and conveyed under pressure with a roller or an endless belt, so that the unfixed developer on the transfer paper is A thermal fixing device for fixing an image, comprising at least one of means for cleaning the roller or belt and means for applying a release agent thereto, and a detection means for detecting the surface shape of the transfer paper, and the detection means for detecting the surface shape of the transfer paper. Offset can be prevented by making at least one of the cleaning ability of the cleaning means and the amount of application by the release agent applying means variable in accordance with the output value of the means.

[0013]

According to the first aspect of the invention, when the surface roughness of the transfer material is large based on the output value of the detection means, the fixing temperature is increased to ensure fixing performance. Furthermore, when the surface is smooth, the fixing temperature does not need to be high, and is therefore lowered.

Further, in the second invention, if a transfer material with a rough surface is used, the cleaning force is increased to ensure that even if there is a large amount of offset toner, according to the output value of the detection means. This can be removed and/or the amount of release agent applied can be increased to suppress the occurrence of offset. In addition, if a transfer material with a smooth surface is used, offset toner can be sufficiently removed even if the cleaning power is reduced, and (or) even if the amount of release agent applied is small, offset toner may still occur. can be suppressed.

[0015]

Embodiments Hereinafter, embodiments of the present invention will be described based on the accompanying drawings.

First Embodiment FIG. 1 is a schematic sectional view of an electrophotographic apparatus according to a first embodiment of the present invention.

As is well known, the region where a toner image is formed includes a charging device 2, an image exposure device 3, and a charging device 2, an image exposure device 3,
A developing device 4, transfer separation chargers 5 and 6, a cleaning device 7, and a pre-exposure 8 are arranged, and a toner image is formed on the photoreceptor 1 by an image forming method called the Carlson method.

This toner image is transferred as an unfixed toner image onto a transfer material P such as paper (hereinafter referred to as paper) supplied from a paper feeding system, and is then fixed on the paper as a permanent image by a fixing device 9. After that, the paper is ejected.

In the present invention, a detection device 10 for detecting the surface properties of the paper is provided on the conveyance system for conveying the paper.

FIG. 2 shows an outline of this detection device.

The detection device 10 includes a metal conveyance guide 13,
13', it is provided facing the lower guide 13, and is gently pressurized from the back side by a biasing member 14. Therefore, the paper P is conveyed while being sandwiched between the detection means and the guide plate 13 under light pressure.

As shown in FIG. 2, the detection means 10 is an element having a structure in which a flexible elastic body 12 such as a sponge is wrapped with a conductive film 11, and the film 11 is connected to a capacitance meter 15. There is. Further, the opposing guide plates 13 are grounded or grounded via a known impedance element. Furthermore, the detection element includes a guide plate 13.
A magnetic body 16 is attached on the surface facing ',
A gap sensor 17 is attached to the guide plate 13' opposite to this (the gap sensor 17 measures the distance between the magnetic body 16 and the sensor using an eddy current measurement method).

In such a configuration, when paper enters between the sensing element and the guide plate 13, the gap sensor 17
Since the detected value changes by the thickness of the paper that has entered, the thickness of the paper passing through can be determined. In addition, the capacitance detected by the capacitance meter is the capacitance C1 of the paper itself and the paper guide plate 13.
It is detected as the combined capacitance of the capacitance C2 due to the gap between the paper and the film 11. Of these, C1 depends on the paper thickness, so C1 can be determined from the paper thickness obtained from the gap sensor. Therefore, the remaining capacity is due to C2 and is proportional to the surface roughness of the paper, so the rougher the surface, the greater the capacity. In this way, surface roughness can be roughly detected based on the magnitude of the detected capacitance.

On the other hand, as the fixing device, a direct heating type thermal fixing device in which a heating member comes into contact with the paper is used, and as an example, a thermal roller fixing device is shown in FIG. The basic configuration is almost the same as that shown in FIG. 6, and includes a heating source 20 (such as a halogen heater), whose surface temperature is controlled by a temperature control element 21 to a predetermined temperature according to the detected roughness of the paper surface. A pressure contact portion (nip) is formed between the fixed fixing roller 18 and the pressure roller 19 having an elastic layer, and by passing the paper carrying the unfixed toner image between this pair of rollers, the paper is heated and nipped. A fixed image is obtained by applying pressure.

A cleaning roller 22 (for example, an elastic roller whose surface is wrapped with a nonwoven fabric) for cleaning the offset toner is provided in contact with the fixing roller 18 . Here, the cleaning roller 22 has a center shaft 23 rotatably attached to an arm 25, and the arm 25 is swingable around the swing center shaft 24. A biasing member 27 is connected to press the roller against the fixing roller. Further, a solenoid 26 is provided at an intermediate portion between the swing center shaft 24 and the biasing member 27. When this solenoid is pulled (ON state hereafter), the cleaning roller comes into light pressure contact with the fixing roller as shown by the broken line in the figure, and if it is not pulled (hereinafter OFF state), the cleaning roller comes into strong pressure contact state as shown by the solid line. It is set as follows.

Next, the operating state of the apparatus of this embodiment having the above structure will be explained.

As described above, when the copy button (not shown) is pressed, the process of forming a toner image progresses on the photoreceptor, and the paper P is fed in synchronization with this. As described above, when the paper is conveyed between the conveyance guides 13 and 13', the roughness of the paper is detected by the detection means 10. The toner image on the photoreceptor is transferred onto the paper as an unfixed image by the transfer charger 5, and then conveyed to the fixing device 9 where it is fixed. In this fixing step, since the roughness of the paper is detected in advance, the fixing temperature is selected depending on the roughness. For example, if the paper surface roughness RZ value is less than 15 μm, the fixing temperature is set to 180°C, and if the paper surface roughness RZ value is 15 μm or more, the fixing temperature is set to 10°C.
Set to a high temperature of 190°C to increase fixing ability. As described above, since the fixing temperature is set according to the roughness of the paper, defective fixing is prevented.

Furthermore, in the fixing step, the pressure applied by the cleaning roller is selected depending on the detected roughness of the paper. For example, a limited value (slicing level) is set in advance for the surface roughness RZ, and if the paper is rougher than this value, the solenoid 26 is turned off and the cleaning roller is brought into strong pressure contact to increase the cleaning ability, and the surface roughness is reduced to less than the specified value. In the case of paper with a roughness of 100 mL, the cleaning ability is weakened by turning on the solenoid 26 and applying light pressure to the cleaning roller. In this way, the paper after fixing is ejected from the main body of the machine and copying is completed (the copying mode may be changed to duplex or multiplex mode). The electrical process of detecting the surface roughness and turning the solenoid on and off according to the value can be easily carried out and is not important to the present invention, so it will not be described here. omitted.

[0029] By doing so, it is possible to ensure an appropriate cleaning power depending on the surface properties of the paper, and to reliably remove offset toner. In addition, normally, if the cleaning roller is pressed too hard, the fixing roller may be damaged quickly, but as in this example, the pressure is increased only when necessary, so the load on the fixing roller is reduced.
The life of the fixing roller can be extended. In fact, according to the studies of the present inventors, in the above example, the slice level is RZ=
By setting a value of 11 μm and applying strong pressure to the cleaning roller when the value is above this value, and applying weak pressure when the value is less than this value, almost satisfactory results were obtained for various types of paper.

[0030] In the above, RZ was used as the surface property, but other indexes expressing the surface property, such as RMAX
It is also possible to set the slice level by .

Further, the cleaning means is not limited to the roller type of this embodiment, and various mechanisms for changing the cleaning ability thereof can be applied. Further, in this embodiment, the cleaning ability is changed over in two stages, but it is also possible as an embodiment of the present invention to change over the cleaning ability finely in multiple stages depending on the surface properties of the paper.

<Second Embodiment> When the electrophotographic apparatus is a high-speed machine, after the roughness of the paper is detected, the paper is transferred to the fixing device before the fixing roller temperature reaches the fixing temperature corresponding to the roughness of the paper. Sometimes it passes through 9. In such cases,
Conveyance of the paper is temporarily stopped immediately before the paper enters the registration rollers 22 in FIG. 1, and the paper is conveyed after the fixing roller reaches a fixing temperature corresponding to the roughness of the paper. This results in
Even in high-speed machines, fixing can be performed at an appropriate fixing temperature, and poor fixing performance can be prevented.

<Third Embodiment> In the first embodiment, a fixing device equipped with a cleaning device was explained, but a fixing device equipped with an oil application device may also be used, and an example thereof is shown in the figure as a third embodiment. 4.

In the fixing device shown in FIG.
A heat-resistant felt 28 for supplying oil to the fixing roller 18 can be brought into contact with the fixing roller 18 at one end thereof. The other end of the felt 28 is located in an oil pan 29 and is immersed in oil, and the oil that has permeated the felt 28 is applied to the fixing roller.

The contact end side of the felt 28 is bonded to a sheet metal 32, and includes a biasing member 30 that presses the felt 28 toward the fixing roller 18, and a solenoid 31 that is connected to the sheet metal and changes the pressing force of the felt 28. It is provided. As in the case of the first embodiment, when the solenoid 31 is turned ON, the felt 28 comes into light pressure contact, which reduces the amount of oil applied, and when it turns OFF, the oil is squeezed out from the felt 28 due to strong pressure contact, reducing the amount of oil applied. increase. Such a fixing device is used in the same main body as in the first embodiment. After the paper roughness detection and toner image formation go through the same steps as in the first embodiment (descriptions are omitted as they are redundant), the paper carrying the unfixed toner image reaches the fixing device. Here, since the roughness of the paper has been detected in advance, the amount of oil applied is changed according to that value. For example, if paper with roughness exceeding a specified value is received, the solenoid 31 is turned off to increase the amount of oil applied; otherwise, the solenoid 31 is turned on to reduce the amount of oil applied. This allows only the necessary and sufficient amount of oil to be supplied according to the roughness of the paper, reducing offset regardless of the roughness of the paper, and reducing oil waste by supplying the minimum amount of oil needed. avoids unnecessary use.

[0036] In this example, felt was used as the release agent (oil) application means, but the application means are not limited to this, and may include those using a porous member and rollers. It can be applied to all the methods proposed and used in the past. Further, a method such as a web method that combines oil application and cleaning can also be applied.

<Fourth Embodiment> In the above embodiment, the surface properties of both sides of the paper were detected and controlled, but with ordinary paper, there is usually a difference in the surface properties between the front and back sides of the paper. Therefore, as mentioned above, the fixing properties and offset amount differ between the front and back sides of the paper. Therefore, it may be sufficient to actually detect and control the surface properties of the surface of the paper on which the toner image is placed. The present embodiment is one of such embodiments, and is characterized in that the surface properties of the paper (on the side on which the toner is placed) are optically detected.

As shown in FIG. 5, a light source (parallel light such as a laser beam is preferable, but a condensed light It is composed of a light receiving element (CCD) 34 that detects reflected light from the paper surface. The light emitted from the light source 33 is reflected by the surface of the paper, and most of it enters the light receiving element 34. At this time, if the surface of the paper is smooth, the light is reflected in an almost constant direction, so the light is not received. The spread of light on the element 34 is small. However, if the surface is rough, the light will be diffusely reflected and will be incident on the light receiving element 34 in a spread state. The degree of this spread depends on the surface quality of the paper that is exposed to the light. Therefore, from the spread of the reflected light detected by the light receiving element 34, only the surface quality of the paper on the side on which the toner image is placed can be detected. Note that in reality, the output from the light receiving element 34 is calculated by the CPU and calculated as the surface quality of the paper, but such a circuit itself is well known and is not the essence of this embodiment. Therefore, the explanation will be omitted. Hereinafter, similar to the previous embodiment described above,
Depending on the detected surface properties of the paper, the fusing temperature of the fusing device may be selected, or the cleaning capacity and/or
By controlling the amount of oil applied, it is possible to maintain cleaning performance, use oil appropriately, and reduce the load on the fixing roller while ensuring fixing performance and suppressing the occurrence of offset. Further, in this embodiment in particular, since the surface properties of only the surface on which toner is actually placed are detected and controlled, the above-mentioned characteristics can be made more appropriate than in the above-mentioned embodiments.

In this embodiment, an example of optical detection was shown as a means for detecting the surface properties of the surface on which toner is placed, but the detection method is not limited to such an optical method. Instead, various known methods can be applied, such as a method of tracing the surface of paper with a stylus to directly detect its surface properties.

Furthermore, in the embodiments described above, the means for detecting the surface quality of the paper was provided on the conveying path immediately after feeding the paper, but the arrangement is not limited to this, and it may be located upstream of the fixing device. However, there is no problem even if it is immediately before that.

Further, the heat fixing device to which the above examples are applied is not limited to the heat roller type described in the example described, but for example,
The present invention can also be applied to a fixing device that uses a film instead of a roller, as shown in No. 3-313182.

[0042]

As described above, in the first invention of the present application, the roughness of the surface of the transfer material is measured by the detection means arranged upstream of the fixing device to detect the roughness of the transfer material. However, by setting the optimum fixing temperature according to the output value of the detection means, it is possible to obtain a satisfactory fixing performance even when the surface of the transfer material is rough.

Further, in the second invention, in obtaining a fixed toner image by passing an unfixed toner image through a fixing device equipped with an offset toner cleaning means and/or a release agent application means, the fixing device On the upstream side, there is a means for detecting the surface properties of the paper being passed, and the cleaning ability and/or the amount of release agent applied is controlled according to the surface properties of the paper detected by the detection means. Reliable removal of offset toner and/or
The effect of suppressing the amount of generation and reducing the influence on the image due to offset is obtained. In addition, since the cleaning power is increased as needed, the load on the fixing roller is reduced, contributing to longer life of the roller.Furthermore, since only the appropriate amount of mold release agent is always used, the mold release agent remains effective for a long time. It can be used for.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of an electrophotographic apparatus employing an apparatus according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of a detection device for detecting the surface quality of a transfer material provided on a conveyance path used in the apparatus according to the first embodiment of the present invention.

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

FIG. 4 is a sectional view of a fixing device according to a third embodiment of the present invention.

FIG. 5 is a configuration diagram of a detection device for detecting the surface properties of a transfer material in a fourth embodiment of the present invention.

FIG. 6 is a configuration diagram showing an example of a conventional fixing device.

[Explanation of symbols]

7　Cleaner 9 Fixing device 10 Detection means 18 Fixing roller 19 Pressure roller 20 Heating source 22 Cleaning roller 28 Oil coated felt

Claims (5)

[Claims] 1. A thermal fixing device that fixes the unfixed developer image on the transfer paper by heating and pinching a transfer material having an unfixed developer image with a roller or an endless belt, wherein the transfer material has an unfixed developer image on the transfer paper. It has a detection means for detecting the surface shape of
A thermal fixing device characterized in that a fixing temperature is variable according to an output value of the detection means. 2. When the surface roughness detected by the detection means is larger than a specified value, the conveyance of the transfer material is stopped until a fixing temperature determined in accordance with the specified value is reached. The heat fixing device described in . 3. In a thermal fixing device that fixes the unfixed developer image on the transfer paper by heating and pinching a transfer material having an unfixed developer image with a roller or an endless belt, the roller or at least one of a means for cleaning the belt and a means for applying a release agent thereto;
and a detection means for detecting the surface shape of the transfer paper, and at least one of the cleaning ability of the cleaning means and the amount of application by the release agent application means is variable according to the output value of the detection means. A heat fixing device featuring: 4. The detecting means detects the surface roughness of the transfer paper as the surface shape, and at least one of the cleaning ability and the amount of the release agent applied is variable according to the detected value. heat fixing device. 5. When the surface roughness detected by the detection means is larger than a specified value, the cleaning ability and the application amount of the mold release agent are increased, and when the surface roughness is small, the cleaning ability and the application amount are increased. 5. The heat fixing device according to claim 1, wherein the amount of heat fixing is reduced.