JPH06317997A - Image forming device - Google Patents

Abstract

PURPOSE:To excellently attain fixing by setting the distance between a heating device and a transfer device larger than the maximum transfer paper width capable of forming an image and the rotational speed of the heat resistant film of the heating device faster than that of an image carrier. CONSTITUTION:This image forming device is provided with the heating device 6 allowing a pressure roller 7 to contact with a fixed/supported heating body via the heat resistant film, bringing a transfer paper between the heat resistant film and the pressure roller 7 at the same time when the heat resistant film is traveled and imparting the heat energy of the heating body to the transfer paper via the heat resistant film and a transfer roller 4 transferring an unfixed toner image on a photosensitive drum 1 as the image carrier on the transfer paper. At this time, the distance D1 between the heating device 6 and the transfer roller 4 is set larger than the maximum transfer paper width capable of forming the image D2 and the rotational speed of the heat resistant film of the heating device 6 is set faster than that of the photosensitive drum 1. Thus, the temperature of the pressure roller can be kept a prescribed value or more, without particularly changing the power consumption, etc., of a heater, so that excellent fixability can be always maintained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a laser beam printer or a digital copying machine.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a laser beam printer or a copying machine, an arrow m will be described with reference to FIG.
After charging the image carrier 1 such as a photoconductor rotating in a predetermined direction to a predetermined potential by the charging member 2, the image carrier 1 has a predetermined wavelength and light amount to obtain a desired image. The light L is irradiated to form an electrostatic latent image. A laser beam of a semiconductor laser, a fluorescent light of a halogen lamp, or the like is used as a light source of the light L that is emitted to form the electrostatic latent image.

Toner, which is a developing material for visualizing the electrostatic latent image, is adhered onto the electrostatic latent image by using electric and magnetic forces, and the visible image formed thereon is electrically converted. Transfer is performed on the transfer paper P (not shown) by using a physical force, and then the transfer paper P on which the image is formed is passed through the fixing devices 6 and 7 to which predetermined pressure and heat are applied. The toner image on the paper P is fixed.

As this fixing device, a heat pressure roller shown in FIG. 4 is generally used. The heat roller 10 has a cylindrical aluminum alloy coated with a heat-resistant and abrasion-resistant resin such as PFA. The above is used, and a halogen heater 11 is arranged inside thereof to perform heating. As the pressure roller 12, a roller 12b having a core made of stainless steel 12a and a silicone sponge bonded to the periphery is used.

However, a heat-resistant film has recently been used instead of the heat-pressure roller type fixing device, which is advantageous in that the waiting time until the fixing device warms up is short and the power consumption is low. The surf fixing device as shown in FIG. 5 has come to be used. The specific structure of the surf-fixing device using this film will be described later, but this device keeps the temperature of the entire pressure roller above a certain temperature at the same time as the temperature control of the heater in order to secure sufficient fixing property. I know that is necessary.

[0006]

For low-speed machines (about 4 ppm), quick start, which is a feature of surf fixing,
It is possible to secure sufficient fixability while maintaining the performance of low power consumption. However, medium speed machines (8pp
m), the required power consumption increases with the number of sheets to be fixed, and when the thick paper such as postcards is continuously printed, the first sheet is printed. At the end, until the next printing of the second sheet begins,
The so-called distance between papers and time are shortened, and the temperature of the pressure roller lowered by the printing of the first sheet cannot be sufficiently raised, and as a result, the fixability of the image on the second and subsequent sheets is very poor. turn into. In order to avoid this problem, it is conceivable to reduce the film thickness of the film or increase the temperature control temperature and power consumption of the heater.

However, when the film thickness is reduced, there arises a problem that the film is twisted due to the temperature difference between the film passing portion and the non-sheet passing portion, or the film is torn from the end portion. I will end up. Further, if the temperature control temperature and power consumption of the heater are increased, the heat resistant temperature of each structural member will be exceeded, which is a safety issue, and the cost will be several times higher if a member that maintains sufficient heat resistance is used. Further, there is a problem that increasing the power consumption is contrary to the low power consumption which is a characteristic of surf fixing.

[0008]

According to the image forming apparatus of the present invention, a pressure member is pressed against a fixedly supported heating body through a heat resistant film, and the transfer paper is moved to the heat resistant state as the heat resistant film moves and moves. Introduced between the film and the pressure member,
An image forming apparatus comprising: a heating device for applying heat energy of the heating member to transfer paper through the heat-resistant film; and a transfer device for transferring an unfixed toner image on an image bearing member onto the transfer paper, wherein the heating device comprises: The distance between the transfer device and
Larger than the maximum transferable paper width image formation, and the rotation speed of the heat-resistant film of the heating device is set to be larger than the rotation speed of the image carrier, or the distance between the heating device and the transfer device, The rotation speed of the heat-resistant film of the heating device is set to be higher than the rotation speed of the image carrier after the trailing edge of the transfer paper is set smaller than the maximum transferable paper width for image formation and the trailing edge of the transfer paper comes out of the image carrier and the transfer device. Is characterized by.

According to the present invention, in the image forming apparatus such as a laser beam printer or a copying machine for fixing an image by the surf fixing using the film by the above means, continuous printing can be performed without changing the film thickness of the film. In case,
By taking more time between sheets than before, it is possible to secure the fixability of the second and subsequent images even on thick paper such as postcards. That is, by setting the rotation speed of the fixing device to a large value with respect to the rotation speed of the photosensitive drum, that is, the so-called process speed (Vp), a large sheet distance / time can be secured without reducing the number of printed sheets per unit time. Even if any paper is passed, it is possible to sufficiently secure the fixability of the second and subsequent images by adjusting the temperature between the papers.

[0010]

EXAMPLES Next, examples of the present invention will be described.

<Embodiment 1> FIGS. 1 and 5 are schematic configuration diagrams showing the present embodiment. In FIG. 1, 1 is a photosensitive drum as an image carrier, and 2 is a charging member for charging the surface of the image carrier. As a charging roller, 3 is a developing roller for visualizing a latent image formed on the surface of the image carrier 1 with toner by a laser beam L, and 4 is for transferring a visible image on the image carrier onto a transfer paper. Of the transfer roller, 5 is a conveyor belt for conveying the transfer paper after the toner transfer from the transfer roller to the fixing device, 6 is a fixing device or a heating device using a heat-resistant film and a heater, and 7 is a pressing device for pressing the transfer paper to the heating device. It is a pressure roller. Further, the laser light L is irradiated onto the image carrier by the folding mirror 8.

In FIG. 5, the heating device 6 is a cylindrical heat-resistant film 6 made of polyimide or the like and having a thickness of about 50 μm.
Ceramic heater 6 which has 0 and is a heating body inside
1 is arranged, heat is applied thereby, and the heating temperature is a temperature detection element 62 such as a thermistor arranged in contact with the heater.
Adjust by As the pressure roller 7, an aluminum alloy 71 is used as a core metal, and a roller 72 made of silicone rubber is used on the outside thereof.

The present embodiment is characterized in that the transfer-fixing distance (D1) in FIG. 1 is always Dl> D2 with respect to the maximum printable paper width (D2). It can be implemented in an image forming apparatus such as a removable laser beam printer or a copying machine.

Conventionally, in the case of an 8-sheet machine, the rotational speed of the photosensitive drum or the image carrier, that is, the process speed (V
p) was about 47 mm / sec, and the paper conveyance speed in the fixing device (hereinafter referred to as the fixing speed) was also in accordance with the process speed (Vp). In this case, the distance and time between the sheets are about 5 cm and 1.1 sec, respectively.

Therefore, in this embodiment, in order to increase the distance and time between the sheets, (Vp) is 47 m without changing.
Fixing speed is approx. б1mm / sec with m / sec
Changed to. As a result, the distance between sheets and the time can be secured to be about 12 cm / 2.5 sec, which is more than double that of the conventional setting, and sufficient time can be taken to heat the pressure roller. It became possible. The fixing speed is set as above, the power consumption of the heater is 500 W, the temperature control temperature is 200 ° C., and the film thickness is 50 μm. Is.

In the conventional setting, as shown by the broken line in FIG. 2, the temperature of the pressure roller gradually decreases as printing is continued, and the temperature of the pressure roller rises between the sheets, but it is shown in the figure. As can be seen by using the fixing temperature assured as a guide, the second and subsequent sheets do not show sufficient fixing property over the entire paper. However, when a similar examination is performed based on the conditions of this embodiment, as shown by the solid line in FIG. 2, the time between sheets is sufficiently secured even when printing is continuously performed, so that the number of sheets does not depend on the number of sheets. The temperature of the pressure roller was generally higher than the fixing property guarantee temperature, and the fixing property was not deteriorated.

As described above, the fixing speed is set to a large value with respect to the process speed and the time between sheets is increased, so that the power consumption of the heater, the temperature control temperature, or the film thickness of the film is not changed. It is possible to maintain the pressure roller temperature at a certain value or higher, and it is possible to always maintain good fixability.

<Embodiment 2> The configuration of this embodiment is the same as that of FIG. 1 used in Embodiment 1, and the fixing speed is changed according to the temperature of the pressure roller that is constantly monitored, and the time between sheets is changed. Is properly secured.

The pressure roller temperature changes depending on the type of paper to be printed,
It largely depends on the paper size, and does not particularly depend on the power consumption of the heater and the controlled temperature. A simple example is A4
When the temperature change of the pressure roller when printing (75 g / cm) paper was checked, the power consumption of the heater was 500 W,
In both the case of the temperature-controlled temperature of 200 ° C. and the cases of 700 W and 220 ° C., there was only a temperature change of about 10 ° C. before the paper rushed into the fixing device and passed through.

Therefore, in the present embodiment, a thermistor (not shown) is brought into contact with the pressure roller to measure the minimum value of the temperature of the pressure roller, and the fixing speed is changed stepwise with respect to that value. It is a feature. That is, the fixing speed is set by the judgment of the CPU (not shown) based on the temperature detected by the temperature detecting means.

A4, 8-sheet machine process speed (47 m
m / sec), if the temperature shown in FIG. 2 is 5 ° C lower than the temperature at which the fixing property can be sufficiently secured, the fixing speed is б1mm.
/ Sec, 75 mm / se at 5 to 10 ° C
c When the temperature is 10 ° C. or higher, the paper interval time is set to be long by setting 94 mm / sec. The distance between the paper and the time for these fixing speeds are 12 cm and 2.5, respectively.
sec, 1бcm, 3.5sec, 20cm, 4.2s
ec. The lowest pressure roller temperature is
The determination is made at the point of the arrow of the pressure roller temperature curve, and the fixing speed is changed between the sheets until the next sheet enters the fixing device.

Under the above setting, the power consumption of the heater is set to 50
When various paper types and paper sizes were examined at 0 W and a temperature controlled temperature of 200 ° C., good fixability was exhibited even when printing was continued, and fixability was maintained even for thick paper such as postcards. It has become possible.

As described above, by changing the fixing speed according to the temperature of the pressure roller, it becomes possible to maintain a good fixing property without increasing the power consumption and reducing the performance of 8 sheets per minute. .

<Embodiment 3> FIG. 3 is a schematic diagram showing the present embodiment, and 9 is a conveyance guide for the transfer paper P while moving from the transfer roller 4 to the fixing device 6. ~ D for the paper width (D2) with the maximum fixing distance (D3)
The feature is that 3 <D2, which can be implemented in an image forming apparatus such as a laser beam printer or a copying machine having such a configuration.

In the apparatus having the above structure, when the front end of the transfer paper enters the fixing device, the rear end of the paper is still sandwiched between the photosensitive drum and the transfer roller. In that case, only the fixing speed is increased. You cannot do it. Therefore, when the trailing edge of the paper comes out of the nip between the photoconductor drum and the transfer roller, the fixing speed is increased to secure a longer paper interval time. The paper interval time in this case depends only on the transfer-fixing distance (D3) and is not affected by the paper size at all.

Distance between transfer and fixing (D3) on an 8-sheet machine (A4 size) with a process speed of 47 mm / sec.
In a device having a sheet width of 130 mm, the fixing speed is the same as the process speed of 47 mm / sec when the trailing edge of the paper is sandwiched between the photosensitive drum and the transfer roller, and when the trailing edge of the paper comes out of the photosensitive drum and the transfer roller. The fixing speed was set to 94 mm / sec and the examination was conducted. With this setting, the paper interval time is increased by about 1.4 sec, and the total time is about 2.5 sec, which is about 12 cm in distance.
The determination as to whether or not the trailing edge of the paper has come off the photosensitive drum and the transfer roller is controlled by a sequence by the detection means and the CPU, and the timing is uniquely determined when each paper size is detected.

Under the above settings, the power consumption of the heater is set to 50
When the temperature was controlled at 0 W and the temperature control temperature was 200 ° C., the temperature variation of the pressure roller with respect to the number of printed sheets when printing thick paper such as postcards was almost the same as the broken line in FIG. It became possible to maintain a high temperature at all times.

As described above, by increasing the fixing speed when the transfer paper comes out of the photosensitive drum and the transfer roller, the power consumption of the heater is not increased, and the performance of eight sheets per minute is not deteriorated. It has become possible to take a lot of time, and it has become possible to maintain good fixability regardless of paper type and paper size.

[0029]

As described above, according to the present invention, a pressure member is brought into pressure contact with a fixedly supported heating body through a heat-resistant film, and the transfer paper is moved along with the heat-resistant film while the transfer sheet is moved. An image having a heating device which is introduced between pressure members to apply the heat energy of the heating body to the transfer paper through the heat-resistant film, and a transfer device which transfers the unfixed toner image on the image carrier onto the transfer paper. In the forming device, the distance between the heating device and the transfer device is larger than the maximum transferable paper width of image formation, and the rotation speed of the heat-resistant film of the heating device is set to be larger than the rotation speed of the image carrier,
Alternatively, the distance between the heating device and the transfer device is
The rotation speed of the heat-resistant film of the heating device is set to be higher than the rotation speed of the image carrier after the trailing edge of the transfer paper is set smaller than the maximum transferable paper width for image formation and the trailing edge of the transfer paper comes out of the image carrier and the transfer device. This makes it possible to increase the fixing speed relative to the rotation speed of the image carrier, that is, the process speed, to secure a larger paper distance and time than before, and it is possible to sufficiently warm the pressure roller between paper sheets. Since there is no need to increase the power consumption of the heater and the performance of the apparatus is lowered, there is an effect that good fixing performance can be always maintained for any paper type and paper size.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram illustrating Embodiments 1 and 2 of an image forming apparatus according to the present invention.

FIG. 2 is a pressure roller temperature curve diagram illustrating Example 1 of the present invention.

FIG. 3 is a schematic configuration diagram illustrating Embodiment 3 of the image forming apparatus according to the present invention.

FIG. 4 is a sectional view of a fixing device using a conventional heating roller.

FIG. 5 is a cross-sectional view of a fixing device using a heat-resistant film in an example of the present invention.

[Explanation of symbols]

1 ... Image carrier 2 ... Charging member 3 ... Developing member 4 ... Transfer member 5 ... Paper conveying member 6 ... Heating device 7 ... Pressing roller 8 ... Folding mirror 9 ... Paper conveying guide 10 ... Heating roller 11 ... Heater 12 ... Addition Pressure roller 20 ... Heat resistant film 21 ... Ceramic heater 22 ... Temperature detection element 23 ... Pressure roller

Claims (3)

[Claims] 1. A heating member fixedly supported is brought into pressure contact with a pressure member via a heat-resistant film, and transfer paper is introduced between the heat-resistant film and the pressure member while the heat-resistant film is running and moved. An image forming apparatus comprising: a heating device for applying heat energy of a body to a transfer paper through the heat-resistant film; and a transfer device for transferring an unfixed toner image on an image carrier onto the transfer paper, wherein the heating device and the transfer An image forming apparatus, wherein a distance from the apparatus is set to be larger than a maximum transferable paper width for image formation, and a rotation speed of a heat-resistant film of a heating device is set to be higher than a rotation speed of an image carrier. 2. The image forming apparatus according to claim 1, wherein the rotation speed of the heat-resistant film of the heating device can be switched according to the temperature of the pressing member. 3. A heating member fixed and supported is pressed against a pressure member via a heat-resistant film, and a transfer paper is introduced between the heat-resistant film and the pressure member together with the traveling movement of the heat-resistant film to heat the film. An image forming apparatus comprising: a heating device for applying heat energy of a body to a transfer paper through the heat-resistant film; and a transfer device for transferring an unfixed toner image on an image carrier onto the transfer paper, wherein the heating device and the transfer The distance from the device is set smaller than the maximum transferable paper width for image formation, and after the trailing edge of the transfer paper comes out of the image carrier and the transfer device, the rotation speed of the heat-resistant film of the heating device is set to the image carrier. The image forming apparatus is characterized in that the rotation speed is higher than that of the image forming apparatus.