JP4690732B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus for an electrophotographic process such as a copying machine, a printer, and a facsimile machine, and more particularly to an image forming apparatus including a fixing device that fixes a toner image to a transfer material by heating.

Some image forming apparatuses such as copying machines, facsimile machines, printers, and printing machines fix an unfixed image transferred and carried on a recording medium such as paper and print it out as a copy.
A fixing device used for fixing has a configuration in which a pair of rollers are arranged to face each other, one roller is used as a heating roller, and the other roller is used as a pressure roller for a recording medium. In this configuration, the unfixed image is fused and fixed by the heat from the heating roller while the recording medium is nipped and conveyed in the nip portion between the heating roller and the pressure roller.
In addition to the above-described configuration, the fixing device has a configuration in which a roller and a belt are combined. In this configuration, instead of the heating roller, a belt wound around a pair of rollers is used, and a pressure roller is opposed to one of the rollers. Of the pair of rollers, the roller that drives the belt in cooperation with the roller on the side facing the pressure roller is provided with a heat source for heating from the back side of the belt. A heat source is provided for heating. The belt has a smaller volume and a smaller heat capacity than the roller, so that the temperature can be increased for a short time, and the temperature rise at the start-up is faster than the configuration using only the heating roller and the pressure roller described above. There is. In addition, by applying a heat source with a pressure roller, the temperature rise is accelerated on both the front and back sides of the belt. When aluminum having a high thermal conductivity is used for each roller as a constitution of the belt, stainless steel is used as a base in contact with the roller surface, and a belt body made of a release layer made of silicon rubber or fluorine resin is arranged on the surface 2. There is a layer structure. It is well known that the temperature of the fixing member is achieved by controlling the heating of the heater so as to be detected by the temperature detecting means and maintain the target temperature.

However, the recording medium to be fixed is affected by the storage environment and the temperature is not constant. Since the required amount of heat changes depending on the temperature at which the recording medium is fixed, it is often proposed to detect the external environment and control the fixing temperature.
For example, in Patent Document 1, the temperature sensor provided in the image forming apparatus room is disposed at a position that is not easily affected by the heat generated by the fixing unit. Since the ambient temperature cannot be detected, the sensor value is not used after the job starts. During standby, the fixing temperature is corrected based on environmental temperature detection. The specific position of the sensor is not disclosed.

Japanese Patent Laid-Open No. 10-39672

However, in the above configuration, if the fixing temperature correction is not performed by detecting the environment even during the job at the initial power-on or job initial temperature, the temperature of the transfer paper before feeding does not change. Due to an increase in the temperature of the conveyance path, the amount of heat applied to the transfer paper at the time of fixing approach becomes excessive, causing curling of the transfer paper after fixing, resulting in problems such as stitching and binding misalignment at the finisher.
In view of the above problems, an object of the present invention is to provide an image forming apparatus including a fixing device that has good toner fixing property and does not cause transfer paper curl after printing.

In order to solve the above problems, the present invention provides a fixing device that fixes a transfer material carrying an unfixed toner image by heating, a temperature detection unit that detects the temperature in the image forming apparatus having the fixing device, and And a control unit that corrects a control temperature of the fixing device based on a detection result of the temperature detection unit. The temperature detection unit includes a temperature detection unit that detects a temperature of a cover of the fixing device, and a transfer belt. A temperature detecting means for detecting the temperature, when the continuous printing time is a predetermined time or more, the control temperature is corrected based on the detected temperature of the transfer belt, and when the continuous printing time is less than the predetermined time, Ru der image forming apparatus and corrects the control temperature based on the detected temperature of the cover of the fixing device.

The present invention is based on a fixing device for fixing by heating a transfer material carrying an unfixed toner image, a temperature detecting means for detecting the temperature in the image forming apparatus having the fixing device, and a detection result of the temperature detecting means. in the image forming apparatus and a control means for correcting the control temperature of the fixing device Te, the temperature detecting means includes temperature detecting means for detecting the temperature of the conveying guide plate arranged between the fixing nip and the transfer nip A temperature detecting means for detecting the temperature of the transfer belt, and when the continuous printing time is a predetermined time or more, the control temperature is corrected based on the detected temperature of the transfer belt, and the continuous printing time is less than the predetermined time. case, Ru der image forming apparatus and corrects the control temperature based on the detected temperature of the sheet guide.
According to the present invention, in any one of the above image forming apparatuses, the fixing device is a fixing device using at least one endless belt.

  According to the present invention, it is possible to provide an image forming apparatus including a fixing device that has good toner fixing property and does not cause transfer paper curl after printing.

  The best mode for carrying out the present invention will be described below with reference to the drawings. The following description is an example of the best mode of the present invention, and it is easy for a person skilled in the art to make other embodiments within the scope of the claims by making changes and modifications within the scope of the claims. However, this does not limit the scope of the claims.

FIG. 1 is a diagram illustrating an image forming apparatus including a fixing device according to the present invention. The configuration will be described below. The image forming apparatus shown in FIG. 1 is used as a copier or printer capable of forming a full color image by a quadruple tandem method. In addition to this, there is a facsimile apparatus capable of performing the same image forming process as the above-described copying machine and printer based on a received image signal. Note that the image forming apparatus includes not only the above-described color image but also an apparatus that targets a single color image.
The image forming apparatus 20 shown in FIG. 1 forms a color image directly from a latent image carrier onto a recording sheet by superimposing and transferring an image for each color separation onto a recording sheet such as paper adsorbed to a transfer belt used as a transfer body. Is used. In FIG. 1, an image forming apparatus 20 includes the following apparatuses. Image forming devices 21Y, 21M, 21C, and 21BK that form images of respective colors according to the original image, transfer devices 22 that are arranged to face the image forming devices 21Y, 21M, 21C, and 21BK, and the respective image forming devices A first paper feed cassette 24A, a first paper feed cassette 24A provided in a paper feed device 24, a manual feed tray 23 as a sheet supply means for feeding a recording sheet to a transfer area where the devices 21Y, 21M, 21C, 21BK and the transfer device 22 face each other. Two sheet feeding cassettes 24B, registration rollers 30 for supplying the recording sheets conveyed from the manual feed tray 23 and the sheet feeding cassettes 24, 24 in accordance with the image forming timings of the image forming apparatuses 21Y, 21M, 21C, 21BK; And a fixing device 1 for fixing the sheet-like medium after transfer in the transfer area.

The image forming apparatus 20 generally includes plain paper (hereinafter simply referred to as plain paper) used for copying and the like, OHP sheets, 90K paper such as cards and postcards, thick paper having a basis weight of about 100 g / m ² or more, envelopes, and the like. Any so-called special sheet (hereinafter simply referred to as a special sheet) having a heat capacity larger than that of the paper can be used as the sheet-like medium.
Each of the image forming devices 21C, 21Y, 21M, and 21BK develops each color of cyan, yellow, magenta, and black, and uses different toner colors, but the configuration is the same. The configuration of 21C will be described as a representative of the image forming devices 21C, 21Y, 21M, and 21BK. The image forming device 21C includes a photosensitive drum 25C as an electrostatic latent image carrier, a charging device 27C arranged in order in the clockwise direction in the drawing, which is the rotational direction of the photosensitive drum 25C, and a developing device. 26C and a cleaning device 28C, and a well-known configuration is used that receives exposure light from the writing device 29 between the charging device 27C and the developing device 26C. In addition to the drum shape, the electrostatic latent image carrier may have a belt shape.

FIG. 2 is a view showing a fixing device according to the present invention. As shown in FIG. 2, the fixing device 1 includes an endless fixing belt 2 for conveying a sheet-like medium on which toner is fixed, a heating roller 3 and a fixing roller 4 around which the fixing belt 2 is stretched, A pressure roller 5 disposed opposite to the fixing roller 4 via the fixing belt 2, a heater 6, 7 provided inside the pressure roller 5, the fixing belt 2, and the pressure roller 5 A belt-side thermistor 13 and a pressure-side thermistor 14 are provided as temperature detecting means that are arranged to face each other and detect the respective temperatures. The fixing belt 2 applies an appropriate predetermined tension to the fixing belt 2 by urging the tension roller 120 from the inside of the fixing belt 2 by an elastic body (not shown) such as a spring.
The fixing roller 4 includes a cored bar 9 and a heat-resistant porous layer elastic body layer 10 that covers the cored bar 9. The fixing roller 4 is urged in a direction to come into pressure contact with the pressure roller 5 by an elastic body (not shown) such as a spring. Reference numeral 12 denotes a guide for guiding the sheet-like medium P to be fixed toward the first fixing unit.
The minute amount oil application roller 121 is brought into contact with the pressure roller 5 by an elastic body (not shown) such as a spring, and for the purpose of improving the releasability between the fixing belt 2 and the toner, a minute amount of silicon oil is pressed against the fixing belt 2 and the pressure. It is applied to the surface of the roller 5. Further, a cleaning roller 122 is brought into contact with the surface of the minute amount oil application roller 121 for the purpose of preventing toner sticking on the surface of the minute amount oil application roller 121.

(Embodiment 1)
FIG. 3 is a diagram illustrating the position of the temperature sensor in the first embodiment. As shown in FIG. 3, in the first embodiment, the temperature sensor S1 is provided in the frame of the writing device 29, and the temperature of the frame of the writing device is detected. The fixing temperature is corrected based on the temperature detected by the temperature sensor S1. The temperature detection may be the temperature of the object or the atmosphere.
FIG. 4 is a diagram showing the relationship between the temperature detected by the temperature sensor and the correction temperature. As shown in FIG. 4, the correction value varies depending on the detected temperature, and the temperature selected here is adjusted to the fixing temperature. The position of the temperature sensor S1 of the present embodiment is approximately 150 mm from the main heating source of the fixing device 1 (corresponding to the heating roller 3 shown in FIG. 2 in the first embodiment), but is within approximately 200 mm from the fixing device. Good. The temperature detection sensor S1 is for detecting the temperature of the apparatus heated by the heat generated by the fixing apparatus 1, and its purpose is to indirectly detect the temperature of the transfer paper entering the fixing apparatus 1 ( 3) in the present embodiment in consideration of the influence of airflow, heat conduction, etc. in the apparatus. It becomes the position shown.

(Embodiment 2)
FIG. 5 is a diagram illustrating the position of the temperature sensor in the second embodiment. The conveyance path of the transfer paper P indicates the position of the temperature sensor S1 of the image forming apparatus different from that of the first embodiment. In the second embodiment, the temperature sensor 1 is disposed in an apparatus main body (housing) (not shown). In the second embodiment, similarly to the first embodiment, the temperature sensor S <b> 1 is disposed between the transfer device 22 and the fixing device 1.
(Embodiment 3)
FIG. 6 is a diagram illustrating an arrangement of temperature sensors in the third, fourth, and fifth embodiments. FIG. 7 is a diagram illustrating a temperature curve in the third embodiment. In the third embodiment, a temperature sensor S2 as temperature detecting means is disposed on the upper part of the fixing cover. Since the fixing cover is easily affected by the temperature in the fixing device, it is suitable for correcting the fixing temperature at a relatively early time (until t1 shown in FIG. 7) after the operation of the device starts. Suitable for thin paper sensitive to temperature.

(Embodiment 4)
As shown in FIG. 6, in the fourth embodiment, a temperature sensor S3 as temperature detecting means is arranged on the fixing inlet guide plate. Since the fixing inlet guide plate gradually increases in temperature as compared with the fixing cover, it is suitable for correcting the temperature for a relatively long time (until t2 shown in FIG. 7) after the apparatus starts operating. Applicable to transfer paper in general.
(Embodiment 5)
As shown in FIG. 6, in the fifth embodiment, a temperature sensor S4 as temperature detecting means is arranged on the surface of the transfer belt.
Since the transfer belt is transported while being in close contact with the transfer paper for a relatively long time, the transfer belt does not reach a higher temperature than the guide plate, but has a great influence on the transfer paper. It is suitable for correcting when printing continuously for a long time.
(Embodiment 6)
Further, as the sixth embodiment, two of the embodiments described in any of the first to fifth embodiments may be combined. As a result, the temperature can be accurately corrected from the initial stage over time.

  Further, it is known that the characteristics of the fixing device 1 using an endless belt is an effective means for shortening the warm-up time and reducing the energy consumption, but the present invention has a problem due to excessive heat quantity such as curling. At the same time, as shown in FIG. 7, when the amount of heat is insufficient, the temperature is increased by correction (for example, when it is 25 ° C. or less), and when the amount of heat is excessive, the temperature is corrected. (For example, at 35 ° C. or higher), the heat quantity is optimized, and the effect is exhibited in a fixing means that has a smaller heat capacity than a roller, that is, is easy to warm and cool like a belt. Is.

1 is a diagram illustrating an image forming apparatus including a fixing device according to the present invention. 1 is a diagram illustrating a fixing device according to the present invention. It is a figure which shows the position of the temperature sensor in Embodiment 1. FIG. It is a figure which shows the relationship between the detection temperature of a temperature sensor, and correction | amendment temperature. It is a figure which shows the position of the temperature sensor in Embodiment 2. It is a figure which shows arrangement | positioning of the temperature sensor in Embodiment 3, 4, and 5. FIG. It is a figure which shows the temperature curve in Embodiment 3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fixing device 2 Fixing belt 3 Heating roller 4 Fixing roller 5 Pressure roller 6, 7 Heater 9 Core metal 10 Elastic body layer 12 Guide 13, 14 Thermistor 20 Image forming device 21 Image forming device 22 Transfer device 23 Manual feed tray 24 Paper feed Cassette 25 Photosensitive drum 26 Developing device 27 Charging device 28 Cleaning device 29 Writing device 30 Registration roller 31 Paper discharge tray 120 Tension roller 121 Trace application roller 122 Cleaning roller S1 Temperature detection means (temperature sensor)
S2 Temperature detection means (temperature sensor)
S3 Temperature detection means (temperature sensor)
S4 Temperature detection means (temperature sensor)
P transfer paper

Claims (3)

A fixing device for fixing by heating a transfer material carrying an unfixed toner image;
Temperature detecting means for detecting the temperature in the image forming apparatus having the fixing device;
An image forming apparatus having control means for correcting a control temperature of the fixing device based on a detection result of the temperature detection means,
The temperature detecting means is a temperature detecting means for detecting the temperature of the cover of the fixing device, and a temperature detecting means for detecting the temperature of the transfer belt,
When the continuous printing time is equal to or longer than the predetermined time, the control temperature is corrected based on the detected temperature of the transfer belt, and when the continuous printing time is less than the predetermined time, based on the detected temperature of the cover of the fixing device. And correcting the control temperature . A fixing device for fixing by heating a transfer material carrying an unfixed toner image;
Temperature detecting means for detecting the temperature in the image forming apparatus having the fixing device;
An image forming apparatus comprising: a control unit that corrects a control temperature of the fixing device based on a detection result of the temperature detection unit;
The temperature detection means is a temperature detection means for detecting the temperature of a conveyance guide plate disposed between the transfer nip and the fixing nip, and a temperature detection means for detecting the temperature of the transfer belt,
When the continuous printing time is equal to or longer than the predetermined time, the control temperature is corrected based on the detected temperature of the transfer belt. When the continuous printing time is less than the predetermined time, based on the detected temperature of the transport guide plate. An image forming apparatus that corrects the control temperature . The image forming apparatus according to claim 1, wherein
The image forming apparatus, wherein the fixing device is a fixing device using at least one endless belt .

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