JP2008151856A - Fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device which is more excellent in quick start performance and energy saving performance than a fixing device adopting an on-demand fixing system, concretely, which can improve fixability and drop fixing temperature by extending a period of time required for heating toner than heretofore and applying pressure to the toner after being sufficiently melted. <P>SOLUTION: A heating means is disposed on a pressure means composed of upper and lower rollers forming a nip between them. An area heated by a heating means is made wider than an area pressed by the pressure means. In the area heated by the heating means, the pressing means is disposed in the downstream side of an image forming medium conveyance path. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine or a printer.

  In a transfer type image forming apparatus using electrophotographic technology, a film heating type fixing device is used in a fixing unit that fixes a toner image transferred onto a transfer object such as recording paper by heating and pressing. (For example, see Patent Document 1).

  This film heating system is a system in which a heater is adhered to one surface side of a heat resistant film and a heated material is adhered to the other surface side, and the heat energy of the heater is applied to the heated object via the heat resistant film.

  FIG. 3 shows a schematic diagram of a fixing device employing a film heating method.

  This apparatus is composed of a ceramic heater 10 as a heating element, a stay 11 that supports the heater, and a thin cylindrical film 12 made of a heat-resistant resin material wound around a stay that supports the heater. It consists of a pressure roller 13 and the like that form a nip portion N in pressure contact with the heater.

  The pressure roller is driven to rotate, so that the film 12 is driven to rotate, the heater 10 is energized, and the temperature is adjusted to a predetermined temperature. A recording material 7 which is a heated body to which the toner image 14 is transferred in a transfer section (not shown) is conveyed, introduced into the nip N, and sandwiched and conveyed with the film 12 to the heater 10 This heat is applied to the recording material 7 through the film 12 to soften the unfixed image (toner image) 14 on the surface of the recording material and heat-fix it.

Since the heat capacities of the film 12 and the heater 10 are small, the time required for the heater 10 to be energized and adjusted to a predetermined temperature is short, and this fixing method is excellent in quick start performance and power saving performance.
Japanese Unexamined Patent Publication No. 2-157878

  In recent years, further quick start characteristics and power saving characteristics of printers are required from the market.

  By using a low heat capacity component, it is necessary to further improve the efficiency even in the film fixing method having excellent quick start property and power saving property.

  When printing is started and the paper to which the unfixed toner image is transferred passes through the nip portion N in the fixing device, heat is applied to the paper, and further pressure is applied to fix the toner image on the paper.

  The width of the nip portion N is about 10 mm even if it is large in the film fixing system.

  If the conveyance speed of the image forming medium is 100 mm / sec, the nip passing time at one point on the image forming medium is 0.1 sec.

  In order to melt an unfixed toner image in such a very short time and simultaneously fix it on the image forming medium by applying pressure, it is necessary to heat the toner image at a temperature higher than that required for melting the toner. The present invention proposes a fixing device that can solve such problems and can perform fixing with higher thermal efficiency.

  The present invention is a fixing device having the following configuration.

  (1) an image carrier, a charging device for charging the image carrier, a means for writing information by creating an electrostatic latent image on a charging surface of the image carrier, and the electrostatic latent image with toner Development means for visualizing and means for transferring the visualized toner image onto the image recording medium, applying heat to the toner image transferred onto the image recording medium and applying pressure to the image recording medium In the fixing device of the image forming apparatus having a fixing means, the fixing means has a light source and a heat source as heating means, and irradiates light from the light source or radiant heat from the heat source toward the image recording medium to give energy. The toner is absorbed and melted by the toner on the image recording medium, and is then fixed on the image recording medium by applying pressure by a pressurizing unit. The pressurizing unit is provided in a heating area by light irradiation and heat irradiation. Special that The fixing device to be.

  (2) The light source or heat source is covered with a certain gap with a reflector opened in front of the pressurizing region including the conveyance path of the image recording medium, and all the light from the light source and the radiant heat from the heat source are directly 2. The fixing device according to claim 1, wherein the fixing device is configured to be reflected by a reflecting plate and irradiated onto an image forming medium conveyance path.

  (3) The pressurizing means is arranged slightly downstream in the heating area, and an upstream side of the pressurizing means has a preheating area that is heated before the toner image is pressurized. Item 3. The fixing device according to Item 1 or 2.

  With the configuration according to the present invention, it is possible to form a fixing device that satisfies the power saving performance.

  The light and heat irradiation area is wider than the pressure area, and the pressure means is included in the light and heat irradiation area, so that the pressure means is warmed and the unfixed toner image on the image forming medium enters the pressure area. Before the image forming medium is irradiated with light and heat directly and presupposed by preheating, it is fixed on the image forming medium by the pressurizing means.

  The preheated area that is preheated before the image forming medium is pressed can be expanded to more than double the pressed area by changing the degree of opening of the reflector, which is larger than the nip width in the conventional film heating method. It can be taken widely.

  In addition, since the heating area is wider than the pressure area and the pressure unit is arranged in the heating area, not only the toner image on the image forming medium is warmed, but also the roller as the pressure unit is simultaneously heated. In addition, the fixability can be improved.

  By providing the preheating region upstream of the pressurizing means, the toner can be sufficiently melted, the fixing property can be improved, and the temperature required for fixing can be lowered.

  As described above, according to the present invention, the fixing temperature can be lowered by adopting a fixing device configuration that efficiently applies heat to the toner and improves the fixing property, thereby forming a more energy-saving fixing device. It becomes possible.

(Example 1)
Hereinafter, the present invention will be described in detail.

  FIG. 1 shows the structure of the fixing device of the present invention.

  The heating means 1 preferably uses a halogen lamp or carbon lamp as a light source and a ceramic heater as a heat source. In this embodiment, a halogen lamp is used as a light source. The heating means 1 is arranged at a position slightly away from the image forming medium conveyance path. Furthermore, the heating means 1 is curved and has a structure covered with a reflecting plate 2 opened to the conveyance path side. The curvature of the curved portion is adjusted so that all the light and heat emitted from the heating means are reflected on the image forming medium conveyance path, and immediately below that is a heating region 3 by light and heat.

  A pressure means 4 composed of upper and lower pressure rollers is provided slightly downstream of the heating region 3. These two pressure rollers have a structure in which a metal core is covered with rubber, and press each other to form a nip portion N on the image forming medium conveyance path.

  The pressure roller is provided with temperature detection means, and is configured so that appropriate heat is supplied to the image forming medium 7 to stabilize the fixing property and to prevent ignition due to temperature rise.

  A reflection plate 5 is provided directly below the image forming medium conveyance path, and reflects light and heat from the heating means to increase thermal efficiency.

  Further, the curved reflector 5 is configured to open larger toward the upstream side than the downstream side when viewed from the heating means 1 and to take a large preheating region 6.

  The image forming medium 7 conveyed to the fixing device first enters the preheating region 6, and the energy from the heating means 1 is sufficiently absorbed by the unfixed toner image on the image forming medium and melted.

  Thereafter, the toner enters the nip portion N of the pressurizing means 4 and the melted unfixed toner image is fixed on the image forming medium.

  At this time, the pressurizing unit 4 is also heated by being supplied with light or heat energy from the heating unit 1, and the toner image is also supplied with heat in the nip N, and is better fixed on the image forming medium. The Rukoto. Therefore, the color of the roller surface used for the pressurizing means 4 is desirably a color that easily absorbs energy (black).

  In Example 1, Examples 1-1 and 1-2 in which the color of the roller surface used for the pressing unit 4 was changed were performed, and power consumption and fixability were evaluated, respectively. In addition, Comparative Example 1 was also performed for comparison with the Example.

<Evaluation>
The evaluation results are shown in Table 1. Hereinafter, the evaluation method and consideration based on the table will be described in detail.

  A far-infrared halogen lamp having a diameter of 6 mm, a rated voltage of 100 V, and a power consumption of 400 W was used as the heating means 1. The roller used for the pressing means 4 has a structure in which a metal core is covered with Si rubber, and the diameter is 10 mm for both the upper and lower rollers. The width of the heating area 9 was 40 mm, and the width of the preheating area 12 was 25 mm.

  After energizing the halogen lamp and adjusting the temperature to various temperatures with the temperature detection means provided on the pressure roller, the unfixed paper is passed 15 seconds later. Specifically, power consumption until 30 seconds after the start of heater energization was measured.

  As the unfixed image, black and halftone (gray) 5 mm square images were arranged at 9 locations on letter size paper.

  The halftone pattern of this embodiment is a pattern in which a pixel density of 600 dpi is formed by a 3 × 3 matrix, and this is formed in a staggered pattern with one dot and one space.

  After measuring the halftone density of the image after passing through the fixing device with a density meter (Macbeth), rub the image with a dedicated rubbing tester and measure the halftone density after rubbing again. The rate of decline was calculated.

  The rubbing tester has a structure in which 200 g of metal weight is placed on a table that fixes the sheet by static electricity, in accordance with 5 mm square black and halftone patterns placed on the sheet at nine locations. Silbon C paper (manufactured by Ozu Sangyo Co., Ltd.) is sandwiched between the paper and the weight. The table for fixing the paper can reciprocate in the longitudinal direction of the paper. At this time, the image is rubbed against the Sylbon C paper and is lost. In this example, the image was rubbed after 5 reciprocations.

  This density reduction rate was calculated for all nine halftone images on letter-size paper, and an average value was calculated as an index representing the fixability under that condition. That is, it is determined that the smaller the density reduction rate, the higher the fixability.

  Further, from the waveform of power consumption measurement, the rise time from the start of energization of the halogen lamp to the predetermined temperature until the start of temperature control was read.

  When the rising time is short, the integrated power consumed at the time of starting is reduced, which is a good index showing the power saving property as well as the quick start property.

  In each of the examples and comparative examples, the pressure roller temperature was set to 140 ° C., and the fixing device rise time and the fixability were measured when the recording material conveyance speed was set to 100 mm / sec. did. A summary of the rise time of the fixing device and the density reduction rate is shown in Table 1.

実施例1-1ではハロゲンランプ通電開始されると400Wの電力がハロゲンランプに投入され、光照射領域の加熱が始まった。温調が始まるまでに要した時間は5.5secであった。ハロゲンランプ通電開始より15秒後に通紙させた未定着トナー像の擦り試験前後の濃度低下率は15%であった。

In Example 1-1, when energization of the halogen lamp was started, 400 W of electric power was supplied to the halogen lamp, and heating of the light irradiation region started. The time required for temperature control to start was 5.5 seconds. The density reduction rate before and after the rubbing test of the unfixed toner image passed through the paper 15 seconds after the start of energization of the halogen lamp was 15%.

  In Example 1-2, the time required from the start of energization of the halogen lamp to the start of temperature control was 4 seconds. It seems that the rise of the fixing device was accelerated because the energy of the light irradiated by the black pressure roller was well absorbed. Further, the density reduction rate before and after the rubbing test of the unfixed toner image that was passed 15 seconds after the start of energization of the halogen lamp was 10%. Since the temperature of the pressure roller was higher than that of Example 1-1, it seems that the fixing property was improved.

  As Comparative Example 1-1, the same evaluation was performed using a conventional film-fixing-type fixing device. The rise time was 6 seconds, and before and after the rubbing test of the unfixed toner image that was passed 15 seconds after the heater energization started. The rate of concentration decrease was 30%.

  From the above comparison, it has been found that the configuration of the present invention can provide a fixing device that has a faster rise and better fixability than the conventional film fixing method.

  It was also found that increasing the light absorption efficiency by setting the color of the pressure roller to black has the effect of increasing the rising speed and improving the fixability.

(Example 2)
In Example 1, the halogen lamp was disposed above the image forming medium conveyance path, and a reflector was provided below the image forming medium conveyance path. Thermal efficiency was increased by reflecting the light and heat from above to the lower reflector.

  In Example 2, a halogen lamp was also provided below, and light and heat were irradiated from above and below the image forming medium. The configuration diagram is shown in FIG.

  The heating means 1 is arranged at a position slightly away from the image forming medium conveyance path. Furthermore, the heating means 1 is curved and has a structure covered with a reflecting plate 2 opened to the conveyance path side. The curvature of the curved portion is adjusted so that all the light and heat emitted from the heating means are reflected on the image forming medium conveyance path, and immediately below that is a heating region 9 by light and heat.

  A pressurizing means 4 composed of two upper and lower rollers is provided slightly downstream of the heating region 3. These two rollers have a structure in which a metal core is covered with rubber, and press each other to form a nip portion N on the image forming medium conveyance path.

  A heating unit 8 is provided directly below the image forming medium conveyance path, and is configured to irradiate light and heat from below the image forming medium.

  This heating means 8 is curved in the same manner as the heating means 7 disposed above, and has a structure covered with a reflection plate 9 opened to the conveyance path side. The curvature of the curved portion is adjusted so that all the light and heat emitted from the heating means are reflected on the image forming medium conveyance path, and a heating area 6 by light and heat is directly above.

  Similarly to the reflector 2, the curved reflector 9 is configured to open larger toward the upstream side than the downstream side when viewed from the heating means 8, so that the preheating region 6 is made larger.

  The image forming medium conveyed to the fixing device first enters the preheating area 6 and the energy from the heating means 1 and 8 is sufficiently absorbed by the unfixed toner image on the image forming medium and melted. The

  Thereafter, the toner enters the nip portion N of the pressurizing means 4 and the melted unfixed toner image is fixed on the image forming medium.

  At this time, the pressurizing means 4 is also heated by being supplied with light or heat energy from the heating means 1 and 8, and the toner image is also supplied with heat in the nip N, so that it can be used as an image forming medium. It will be fixed. Therefore, it is desirable that the color of the roller surface used for the pressing means 4 is a color that easily absorbs energy.

  In this Example 2, Examples 2-1 to 2-5 were performed in which the energization ratio of the upper and lower heating means and the color of the roller surface used for the pressing means 4 were changed, and the power consumption and the fixability were evaluated, respectively. It was.

<Evaluation>
The evaluation results are shown in Table 2. Since the evaluation method is the same as in Example 1, it will not be described here. Only the discussion based on the table is detailed.

実施例2-1ではハロゲンランプ1および5にMAX値となる400Wの電力を投入した。定着装置の立ち上がりに要した時間は1.5secで15sec後に通紙した未定着画像の濃度低下率は3%であった。

In Example 2-1, the halogen lamps 1 and 5 were charged with 400 W of electric power that was the maximum value. The time required for the fixing device to start up was 1.5 seconds, and the density reduction rate of the unfixed image that was passed after 15 seconds was 3%.

  In Example 2-2, 300 W of electric power was supplied to the halogen lamps 1 and 5 by changing the input voltage. The rise time was 3 sec and the concentration reduction rate was 5%.

  In Examples 2-1 and 2-2, the total power consumption increased, but the rise time was increased by that amount, and the fixing property was improved.

  In Example 2-3, 200 W of electric power was applied to the halogen lamps 1 and 5 while changing the input voltage. The rise time was 5.5 sec and the concentration reduction rate was 15%.

  In Example 2-4, when the input voltage was changed and 100 W of electric power was applied to the halogen lamps 1 and 5 respectively, the rise time was 10 seconds and the concentration reduction rate was 35%.

  In Example 2-5, 200 W of electric power was supplied to the halogen lamps 1 and 5 in the same manner as in Example 2-3. Since the color of the pressure roller was black, the energy absorption efficiency increased, the rise time was 4 seconds, and the density reduction rate was 10%.

1 is a conceptual diagram of a fixing device according to the present invention (Example 1). FIG. 3 is a conceptual diagram of a fixing device according to the present invention (Example 2). Schematic of a fixing device that employs a film heating method that is a conventional example.

Explanation of symbols

1 Halogen lamp (top)
2 Reflector (top)
3 Heating area
4 Pressurizing means
5 Reflector
6 Preheating area N Nip
7 Recording material
8 Halogen lamp (bottom)
9 Reflector (bottom)
10 Ceramic heater
11 stays
12 films
13 Pressure roller
14 Toner image

Claims (3)

  An image carrier, a charging device for charging the image carrier, a means for writing information by creating an electrostatic latent image on a charging surface of the image carrier, and development for visualizing the electrostatic latent image with toner And means for transferring the visualized toner image onto the image recording medium, applying heat to the toner image transferred onto the image recording medium, and fixing the image on the image recording medium by applying pressure. In the fixing device of the image forming apparatus, the fixing unit includes a light source and a heat source as a heating unit, and irradiates light from the light source or radiant heat from the heat source toward the image recording medium. After the toner is absorbed and melted by the toner above, it is fixed on the image recording medium by being pressed by a pressing means, and the pressing means is provided in a heating area by light irradiation and heat irradiation. Features The fixing device to be.   The light source or the heat source is covered with a certain gap with a reflector opened before the pressurizing area including the conveyance path of the image recording medium, and the light from the light source and the radiant heat from the heat source are all directly or the reflector. 2. The fixing device according to claim 1, wherein the fixing device is configured to be reflected on the image forming medium conveying path.   2. The pressurizing unit is disposed slightly downstream in the heating region, and a preheating region is provided on the upstream side of the pressurizing unit and heated before the toner image is pressurized. The fixing device according to 2.

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