JP2009037077A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent curling of a record medium (paper) by making the temperature difference of a fixing member smaller, and to shorten a warm-up time by preventing the dispersion of the heat of the fixing member. <P>SOLUTION: The fixing device is configured so that an unfixed image formed on the record medium P passes through a fixing nip formed by at least two or more fixing members 2, 4 and 5, and is heated and pressurized, to be fixed, and at least one of the fixing members 2, 4 and 5 as a rotating body comprises a pressure roller 5 and has a control mechanism for arbitrarily adjusting the rotational speed of the pressure roller 5. In the fixing device, the control mechanism has a humidity detecting means for detecting environmental humidity in the vicinity and changes the rotational speed of the pressure roller 5 during warm-up operation, based on humidity detected by the humidity detecting means. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fixing device that fixes toner on a recording medium with heat and pressure, and an image forming apparatus such as a copying machine, a printer, and a facsimile machine equipped with the fixing device.

Of the two or more fixing members forming the fixing nip portion, a fixing device in which a heating member is provided only in one fixing member, or a heating member is provided in another fixing member. In a fixing device having a difference in heat capacity or heating capacity of a heating member, a large temperature difference may occur between the fixing members at the end of warm-up.
For example, in a fixing device in which a pressure roller not having a heat source is pressed against a fixing roller having a heating member, the pressure roller is mainly heated only through a pressure contact portion (fixing nip portion) with the fixing roller. At the end of warm-up, the pressure roller is at a lower temperature than the fixing roller, and a large temperature difference occurs between the two rollers.
Even if the pressure roller has a heat source, heat conduction is poor when the rubber of the pressure roller is thick, and the surface temperature of the pressure roller does not increase during a rapid temperature increase such as warm-up.
Under such circumstances, when a recording medium (transfer paper) that is placed in a high humidity environment and absorbs a large amount of water passes through the fixing nip portion, a difference occurs in the degree of dryness on the front and back of the recording medium. The curling is generated, and the transportability and loading capacity are reduced.

For this phenomenon, various technologies such as a method for warming up based on temperature / humidity information, a method for correcting temperature based on calculation results of temperature / humidity sensor information, and a method for changing pressure contact force and rotation speed have been proposed. (For example, see Patent Documents 1 to 4).
Patent Document 1 discloses a technique for changing a warm-up method based on humidity information. In this technology, the temperature of the pressure roller and the fixing roller is increased by increasing the warm-up time when the humidity is high, or by continuing the warm-up operation until the fixing member with the slower heating rate reaches a predetermined temperature. The difference is reduced to prevent paper curling.
In Patent Document 2, the temperature difference between the pressure roller and the fixing roller is reduced by increasing the temperature of the pressure roller and lowering the temperature of the fixing roller based on the temperature and humidity information, thereby preventing the curling of the recording medium. The technology to do is disclosed.
Patent Document 3 discloses a technique for performing temperature correction based on calculation results of a plurality of temperature / humidity sensor information. In Patent Document 4, the temperature of a fixing member that does not have a heat source is set to a set temperature during fixing standby. In order to increase the speed quickly, a technique for changing the pressure contact force and the rotational speed is disclosed.
JP 2005-099373 A JP 2005-345488 A JP 2006-208509 A JP 2001-083833 A

However, the technique of Patent Document 1 is a technique in which additional warm-up is performed up to a specified temperature or up to a specified time, and Patent Documents 2, 3, and 4 basically set the sheet passing through the fixing nip. Technology related to temperature.
As described above, during the warm-up, the pressure roller is mainly heated only through the pressure contact portion (fixing nip portion) with the fixing roller, so that it takes time to raise the temperature of the pressure roller.
This means that the temperature of the pressure roller can be increased quickly by rotating the fixing roller and the pressure roller quickly. However, in an environment where the recording medium is not curled, the temperature of the pressure roller is increased. It is not necessary, and it is necessary to rotate at a low speed so that the temperature rise of the fixing roller does not become slow.
Accordingly, an object of the present invention is to reduce the temperature difference of the landing member by changing the rotation speed of the pressure roller during the warm-up based on the temperature and humidity information in consideration of the above-described situation, and the recording medium An object of the present invention is to provide a fixing device that prevents curling of (paper), prevents heat from being dispersed in a fixing member, and shortens the warm-up time, and an image forming apparatus equipped with the fixing device.

In order to solve the above-described problems, the invention described in claim 1 heats and presses an unfixed image formed on a recording medium through a fixing nip formed by at least two fixing members. In the fixing device, at least one of the fixing members that are rotating bodies is formed of a pressure roller, and has a control mechanism that arbitrarily adjusts the rotation speed of the pressure roller. The mechanism includes a fixing device that includes a humidity detecting unit that detects environmental humidity in the vicinity, and changes the rotation speed of the pressure roller during the warm-up operation based on the humidity detected by the humidity detecting unit. .
According to a second aspect of the present invention, when the humidity detected by the humidity detecting means is high, the rotation speed of the pressure roller is set faster than the rotation speed when the humidity is low. Features a fixing device.
According to a third aspect of the present invention, there is provided the fixing device according to the first or second aspect, wherein the rotation speed of the pressure roller during the warm-up operation is set faster than the rotation speed during the printing operation.

According to a fourth aspect of the present invention, the control mechanism includes a temperature detection unit that detects a surrounding environmental temperature, the environmental temperature detected by the temperature detection unit, and the environmental humidity detected by the humidity detection unit. The fixing device according to claim 1, wherein the rotation speed of the pressure roller during the warm-up operation is changed according to environmental humidity.
According to a fifth aspect of the present invention, the rotation speed of the pressure roller during warm-up is set to be the fastest rotation speed when the environmental temperature is high and the environmental humidity is high. Features the fixing device described.
According to a sixth aspect of the present invention, there is provided a heating roller having a heater built therein, a fixing roller on which an endless fixing belt is stretched together with the heating roller, and facing the fixing roller via the fixing belt. And a pressure roller containing a heater for heating, and a recording medium is conveyed using a fixing nip formed between the fixing belt and the pressure roller as a recording medium conveyance path. The fixing device according to any one of the above is characterized.
According to the seventh aspect of the present invention, the electrostatic latent image formed on the image carrier of the image forming unit is visualized by developing with toner, the toner image is transferred onto a transfer device, 7. An image forming apparatus for transferring the toner image onto a conveyed recording medium and fixing the toner image on the recording medium, wherein the fixing device fixes the toner image on the recording medium. An image forming apparatus comprising the fixing device according to any one of the above.

  According to the present invention, there is provided a humidity detection unit that detects environmental humidity in the vicinity of the image forming apparatus, and a control mechanism that changes the rotation speed of the rotating body during warm-up by the detected humidity. When the humidity is high, by increasing the rotation speed of the rotating body, the temperature difference of the fixing member can be reduced and the curling of the recording medium can be prevented. On the other hand, when the humidity is low, the rotation speed of the rotating body is slowed to prevent the heat of the fixing member from being dispersed and the warm-up time can be shortened.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram showing the configuration of an image forming apparatus to which the present invention can be applied. In the image forming apparatus A of FIG. 1, a fixing device (fixing unit) 1 forms a final end portion of a recording medium conveyance path 22 that extends substantially vertically upward in the image forming apparatus A.
The fixing device 1 in FIG. 1 includes a fixing roller 2, a heating roller 3, a fixing belt 4, and a pressure roller 5. An image forming unit 27 is disposed below the fixing device 1. The image forming unit 27 develops and visualizes the electrostatic latent image formed on the image carrier with toner, and transfers the toner image with a transfer device. The image is transferred onto a certain transfer belt 28.
The toner image transferred onto the transfer belt 28 is a recording medium (transfer paper) conveyed from the paper feed tray 21 to the downstream side of the image forming apparatus A by the paper feed roller 23 through the registration roller 25 and the recording medium conveyance path 22. The toner image is secondarily transferred onto the P at the nip between the transfer belt 28 and the secondary transfer roller 26 and conveyed to the fixing device 1.
Subsequently, the unfixed toner image is fixed while being heated and pressed in the fixing device 1, transported, transported by the paper discharge roller 29, and discharged to the paper discharge tray 30. The image forming apparatus A is also provided with a manual feed tray 24.
In the method of transporting the recording medium P upward substantially vertically through the recording medium transport path 22 as shown in FIG. 1, the distance until the recording medium P reaches the paper discharge tray 30 from the paper feed tray 21 can be shortened. There is an advantage that it is possible to shorten the time until the first printed sheet appears on the paper discharge tray 30.
A temperature / humidity sensor 31 is attached to the side surface of the image forming apparatus main body. The temperature / humidity sensor 31 can measure the environmental temperature and the environmental humidity in the vicinity of the image forming apparatus A.

FIG. 2 is an enlarged partial sectional view showing the fixing device of FIG. 1 in detail. In the fixing device 1 of FIG. 2, an endless fixing belt 4 for conveying a sheet-like medium on which toner is fixed, that is, a recording medium P, is stretched between the fixing roller 2 and the heating roller 3.
A fixing device (fixing unit) 1 includes a pressure roller 5 disposed to face the fixing roller 2 with the fixing belt 4 interposed therebetween, a heater 6 provided in each of the heating roller 3 and the pressure roller 5, 7 and a non-contact type thermistor 10 that is arranged to face the heating roller 3 with the fixing belt 4 interposed therebetween and serves as a temperature detecting means for detecting the temperature of the fixing belt 4.
Further, the thermistor 15 is provided as temperature detecting means for detecting the temperature of the pressure roller 5. The fixing belt 4 is arranged at an appropriate position and has a predetermined tension by a belt stretching member 8 and an urging member 9 which is a pressure spring that presses the fixing belt 4 outward. Yes.

The heating heater 6 in the heating roller 3 uses 1000 W (when a rated voltage is input), and the heating heater 7 in the pressure roller 5 uses 300 W (when a rated voltage is input). By using the heating heater 6 in the heating roller 3 that has a large amount of heat, the temperature of the fixing belt 4 can be increased quickly and the warm-up time can be shortened.
Since the toner used for visualizing the electrostatic latent image on the image carrier is a resin having viscoelasticity, when the toner is melted and discharged at the fixing nip, the toner may be wound around the fixing belt 4 to be jammed. Therefore, it is necessary to provide the separating member 12.
As the separation member 12, in addition to the separation claw that functions in contact with the fixing belt 4, a separation plate that is held with a small gap of about 0.2 mm to 1.0 mm from the fixing belt 4 is used. Can do. FIG. 2 further shows the unfixed toner T on the recording medium P, the entrance guide plate 11, and the recording medium conveyance path 22.
In general, when fixing unfixed toner by heating and pressing at the fixing nip, the fixing strength is dominated by the temperature of the member (the fixing belt 4 in the present invention) on the side in direct contact with the toner. Therefore, in order to increase the temperature of the fixing belt 4 rapidly, the rotation speed of the fixing belt 4 is often relatively slow.
Therefore, the warm-up time is shortened by rapidly increasing the temperature of the fixing belt 4. As a result, the temperature difference between the fixing belt 4 and the pressure roller 5 immediately after the warm-up increases. By combining a fixing method using a low heat capacity fixing belt, an energy saving and stable fixing device can be provided.
However, when a recording medium (transfer paper) that is placed in a high humidity environment and absorbs a large amount of water passes through the fixing nip, if the temperature difference between the fixing belt 4 and the pressure roller 5 is large, the recording medium This causes a difference in the degree of dryness between the front and back surfaces, causing curling of the recording medium P, and lowering the transportability and stacking capacity of the recording medium P.

FIG. 3 is a schematic block diagram showing a control mechanism of the fixing device according to the present invention. The control mechanism shown in FIG. 3 includes a temperature / humidity sensor 31 in the vicinity of the image forming apparatus, a control device 33 including a CPU, an arithmetic unit, etc., a non-contact type thermistor 10, a thermistor 15, a pressure roller driving device 34, and a pressure roller 5. It is shown.
In this control mechanism 32, based on the temperature / humidity information (here, humidity information) from the temperature / humidity sensor 31, the control device 33 determines the temperature difference between the fixing belt 4 and the pressure roller 5 in FIG. The roller driving device 34 is driven to drive the pressure roller 5 at an appropriate rotational speed.
As described above, at least one of the fixing members which are rotating bodies is formed by the pressure roller 5, and the rotation speed of the pressure roller 5 is arbitrarily adjusted by the control mechanism 32. In this case, it has a temperature / humidity sensor 31 which is a humidity detection means for detecting the environmental humidity in the vicinity where the image forming apparatus A (FIG. 1) is installed, and the warm-up operation is being performed by the humidity detected by the temperature / humidity sensor 31 The rotation speed of the pressure roller 5 is changed to a desired range.
By changing the rotation speed according to the environmental humidity, the heat distribution of the fixing member can be arbitrarily changed. When the humidity is high, the temperature difference between the members forming the fixing nip can be reduced, and the curl of the recording medium can be reduced.

Further, the control mechanism 32 sets the rotation speed of the pressure roller 5 faster when the humidity is higher than the rotation speed when the humidity is low. Thus, when the humidity is high, the temperature difference between the members forming the fixing nip can be reduced and the curling of the recording medium can be reduced.
The control mechanism 32 includes a temperature / humidity sensor 31 that is a temperature detection means for detecting the environmental temperature in the vicinity of the image forming apparatus on which the fixing device 1 according to the present invention is mounted. The rotational speed of the pressure roller 5 during the warm-up operation is changed according to the environmental humidity.
By changing the rotation speed according to the environmental temperature and the environmental humidity, the heat distribution of the fixing member can be arbitrarily changed. When the environmental temperature and environmental humidity are high, the temperature difference between the members forming the fixing nip can be reduced, and the curl of the recording medium can be reduced.

表１には、所定の環境温度及び環境湿度におけるウォームアップ中の加圧ローラ５の回転速度を示している。
加熱ローラ３内の加熱用ヒータ６を点灯し（Ｓ４）、加熱ローラ３を通して、定着ベルト４を加熱する。制御装置３３によって、非接触型のセンサであるサーミスタ１０により検知した定着ベルト４の温度がレディー（Ｒｅａｄｙ）温度に達しているかどうか判断し（Ｓ５）、レディー温度に達した時点で、ウォーミングアップ終了とし、印刷動作又は待機動作へ移行する（Ｓ６）。
ウォーミングアップ動作中に印刷要求が行なわれていた場合は、レディー温度到達後すぐに印刷動作を開始する。ウォーミングアップ終了時点で印刷要求が行なわれていない場合には、待機状態へ移行する。本発明ではレディー温度は１６０°Ｃである。
本発明では、非接触型のサーミスタ１０により検知した定着ベルト４の温度のみによって、ウォーミングアップ終了（完了）を判断するが、サーミスタ１５により加圧ローラ５の温度を検知し、定着ベルト４と加圧ローラ５の温度によってウォームアップ終了を判断することもできる。
また、本発明では、加熱ローラ３内の加熱用ヒータ６のみを点灯させて、ウォーミングアップを行ったが、加熱用ヒータ６と加圧ローラ５内の加熱用ヒータ７に電力を配分して、両方でウォーミングアップを行なうこともできる。 FIG. 4 is a flowchart showing a control flow in the fixing device of the present invention. Based on the above situation, the control method of the present invention will be described with reference to FIGS. After the power is turned on (S1), first, the ambient temperature and humidity near the image forming apparatus A (FIG. 1) are detected by the temperature / humidity sensor 31 (FIG. 1) attached to the side surface of the image forming apparatus main body (S2). .
The pressure roller 5 is rotationally driven at a rotational speed determined by Table 1 (S3). From Table 1, the rotational speed of the pressure roller 5 is 150 mm / s when the environmental temperature is 20 ° C. or higher and the environmental humidity is 75% or higher, and the rotational speed is 100 mm / s, which is slower than the above. To rotate.
[Table 1]

Table 1 shows the rotational speed of the pressure roller 5 during warm-up at a predetermined environmental temperature and environmental humidity.
The heater 6 in the heating roller 3 is turned on (S4), and the fixing belt 4 is heated through the heating roller 3. The controller 33 determines whether or not the temperature of the fixing belt 4 detected by the thermistor 10 which is a non-contact type sensor has reached the ready temperature (S5), and when the ready temperature is reached, the warm-up is finished. Then, the process proceeds to a printing operation or a standby operation (S6).
If a print request is made during the warm-up operation, the print operation is started immediately after reaching the ready temperature. If a print request has not been made at the end of warming up, the process shifts to a standby state. In the present invention, the ready temperature is 160 ° C.
In the present invention, the end of warming up (completion) is determined only by the temperature of the fixing belt 4 detected by the non-contact type thermistor 10, but the temperature of the pressure roller 5 is detected by the thermistor 15, and the fixing belt 4 is pressed. The end of warm-up can also be determined based on the temperature of the roller 5.
In the present invention, only the heating heater 6 in the heating roller 3 is turned on to warm up, but power is distributed to the heating heater 6 and the heating heater 7 in the pressure roller 5 to You can also warm up.

FIG. 5 is a graph showing the temperature transition of the fixing belt and the pressure roller at each rotation speed of the pressure roller. FIG. 5 shows the temperature transition of the fixing belt 4 and the pressure roller 5 when warming up is performed at the rotation speed of the pressure roller 5 (FIG. 2) of 100 mm / s and at the rotation speed of 150 mm / s. ing.
When the rotation speed of the pressure roller 5 is 100 mm / s, the temperature increase rate of the fixing belt 4 is high and the temperature increase rate of the pressure roller 5 is low. The warm-up time is short because the warm-up completion (completion) is determined only by the temperature of the fixing belt 4 detected by the non-contact thermistor 10. Further, although the temperature difference between the fixing belt 4 and the pressure roller 5 is large, the environmental temperature and the environmental humidity are relatively low, so the curl of the recording medium does not increase.
When the rotation speed of the pressure roller 5 is 150 mm / s, the temperature increase rate of the fixing belt 4 is slow and the temperature increase rate of the pressure roller 5 is high. Since warming-up completion (completion) is determined only by the temperature of the fixing belt 4 detected by the non-contact thermistor 10, the warm-up time is longer than when the rotational speed is 100 mm / s.
Further, the temperature difference between the fixing belt 4 and the pressure roller 5 is smaller than that at a rotational speed of 100 mm / s, and curling of the recording medium can be suppressed even in an environment where the environmental temperature and the environmental humidity are relatively high.
According to the present invention, by using the fixing device using the fixing belt 4 having a low heat capacity, an energy-saving and highly reliable image forming apparatus can be provided even in an environment where the environmental temperature and the environmental humidity are relatively high. .

1 is a schematic diagram illustrating a configuration of an image forming apparatus to which the present invention can be applied. FIG. 2 is a partial cross-sectional view illustrating an enlarged detail of the fixing device in FIG. 1. FIG. 3 is a schematic block diagram illustrating a control mechanism of a fixing device according to the present invention. 3 is a flowchart showing a control flow in the fixing device of the present invention. It is a figure which shows the temperature transition of a fixing belt and a pressure roller in each rotational speed of a pressure roller with a graph.

Explanation of symbols

A ... Image forming apparatus, P ... Recording medium, 1 ... Fixing device (fixing unit), 2 ... Fixing member (fixing roller), 3 ... Fixing member (heating roller), 4 ... Fixing member (fixing belt), 5 ... Fixing Member (pressure roller), 6 ... heater for heating (in the heating roller), 7 ... heater for heating (in the pressure roller), 10 ... non-contact type thermistor, non-contact type sensor, 15 ... thermistor, DESCRIPTION OF SYMBOLS 21 ... Paper feed part (paper feed tray), 22 ... Recording medium conveyance path, 26 ... Secondary transfer roller, 27 ... Image forming part, 28 ... Transfer device (transfer belt), 31 ... Temperature / humidity detection means (temperature / humidity) Sensor), 32 ... control mechanism, 33 ... control device, 34 ... pressure roller drive device

Claims (7)

  An unfixed image formed on the recording medium is fixed by passing through a fixing nip formed by at least two fixing members and then heated and pressurized, and at least one of the fixing members as a rotating body. Is a fixing device that is formed of a pressure roller and has a control mechanism that arbitrarily adjusts the rotation speed of the pressure roller. The control mechanism has humidity detection means for detecting environmental humidity in the vicinity, A fixing device that changes a rotation speed of the pressure roller during a warm-up operation based on humidity detected by a humidity detection unit.   2. The fixing device according to claim 1, wherein when the humidity detected by the humidity detecting means is high, the rotation speed of the pressure roller is set to be higher than the rotation speed when the humidity is low.   3. The fixing device according to claim 1, wherein a rotation speed of the pressure roller during a warm-up operation is set to be higher than a rotation speed during a printing operation.   The control mechanism includes temperature detection means for detecting a surrounding environmental temperature, and the pressurization during the warm-up operation is performed based on the environmental temperature detected by the temperature detection means and the environmental humidity detected by the humidity detection means. The fixing device according to claim 1, wherein the rotation speed of the roller is changed.   The fixing device according to claim 4, wherein the rotation speed of the pressure roller during the warm-up is set to be the fastest rotation speed when the environmental temperature is high and the environmental humidity is high.   A heating roller containing a heating heater, a fixing roller on which an endless fixing belt is stretched together with the heating roller, a heating roller which is opposed to the fixing roller with the fixing belt interposed and has a heating heater built-in. 6. The recording medium according to claim 1, further comprising a pressure roller, wherein the recording medium is conveyed using a fixing nip formed between the fixing belt and the pressure roller as a recording medium conveyance path. Fixing device.   The electrostatic latent image formed on the image carrier of the image forming unit is visualized by developing with toner, the toner image is transferred onto a transfer device, and the toner image is transferred onto the recording medium conveyed from the paper feeding unit. The image forming apparatus for transferring and fixing the toner image on the recording medium, comprising: the fixing device according to claim 1 as a fixing device for fixing the toner image on the recording medium. An image forming apparatus.

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