JP2010072047A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce defective fixing due to lowering of temperature at the end of a heating member heating a toner image during the waiting time. <P>SOLUTION: A first temperature sensor is arranged in the center of a fixing member, while a second temperature sensor is arranged at the end of the fixing member. During the waiting time, switching between temperature control of the fixing member at a waiting temperature 1 meeting the first temperature sensor and temperature control of the fixing member at a waiting temperature 2 meeting the second temperature sensor is carried out according to the temperature in the center of the fixing member. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a heating device used in an electrophotographic image forming apparatus (a copying machine, a facsimile, a printer, a multifunction machine, etc.), and more particularly to temperature control.

As this type of heating device, as shown in Patent Document 1,
A temperature detection member is provided in the paper passing area of the heating roller for heating the toner image, and the energization to the heater for heating the heating member is adjusted based on the detection temperature of the temperature detection member. Further, a temperature detection member is also provided in the non-sheet passing region. When the temperature detection member detects an abnormally high temperature of the heating roller, the energization to the heater is interrupted.
JP-A-6-11995

  However, if the power supply to the heater is adjusted in accordance with the output of the temperature detection member provided in the central portion, which is the sheet passing area of the heating roller, the temperature at the end of the heating roller is lowered, resulting in poor fixing. This is because the heat radiation amount at the end is larger than the heat radiation amount at the center.

  In particular, after the heating roller is cooled to room temperature, it goes through a startup state in which the heating roller is heated to a predetermined standby temperature, and then waits for the start of the toner image heating operation by maintaining the heating roller at this standby temperature. Then, this phenomenon appears remarkably in this standby state. That is, the heat applied to the inside of the heating roller in the standing state moves to the outside of the heating roller in the standby state. Then, a so-called overshoot in which the temperature of the surface of the heating roller rises due to the movement of the heat, and the detection temperature of the temperature detection member increases. As a result, energization to the heater is turned off, and the temperature of the end portion with a large amount of heat radiation becomes low.

  Further, in the low temperature environment, the heat radiation amount at the end of the heating roller is larger than that in the normal environment, so that the temperature at the end becomes lower.

  Here, if the above-described standby temperature is set high, it is possible to prevent the end of the heating roller from becoming low temperature in a low temperature environment. However, in this case, energization of the heater is adjusted so that the standby temperature is high even in a normal environment where the temperature drop at the end of the heating roller is small, and power consumption in the standby state increases.

  On the other hand, if the temperature detection member is provided at the end of the heating roller to adjust the energization to the heater, the temperature at the center of the heating roller is lowered in the standby state after heating the toner image on the small size paper, and then the toner to be heated Fixing failure occurs at the center of the image. This is because after the heating operation is performed on a small size recording material, the end of the heating roller is at a higher temperature than the central portion, and the heater is turned off before the central portion is heated to the standby temperature. Because it will be done.

  The present invention provides a heating member that heats a toner image on a recording material, a heating source that raises the temperature of the heating member by being supplied with electric power, and a first temperature that detects the temperature of a central portion in the longitudinal direction of the heating member. In the image forming apparatus having a detection member and a second temperature detection member that detects the temperature of the end portion in the longitudinal direction of the heating member, the first temperature detection is performed until the temperature of the central portion rises to a predetermined temperature. According to the output of the member, after the temperature is raised to a predetermined temperature, it has a power control means for controlling the power supplied to the heating source according to the output of the second temperature detection member. To do.

  According to the present invention, it is possible to prevent the end of the heating roller from becoming low temperature and to reduce fixing defects.

  Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.

[Example 1]
First, the overall configuration of an image forming apparatus including the image heating apparatus of the present invention will be described with reference to FIG.

  In the image forming apparatus of FIG. 10, at the time of the copy function, an image based on the image information from the image scanner 10 that reads the image information of the original is formed on the paper P as a recording material.

  At the time of the printer function, it has a printer receiving means 11 for receiving print data created by an external device such as a personal computer (not shown). Then, the image forming apparatus receives print data via a communication line (not shown), and forms an image on the paper P based on image information from the print data.

  A facsimile transmission / reception means 12 is provided for receiving facsimile data transmitted via a communication line (not shown). When the facsimile function is used, the image forming apparatus receives facsimile data via a communication line (not shown). Then, an image based on the image information from the facsimile data is formed on the paper P.

  Next, an image forming method in the image forming apparatus of FIG. 10 will be described.

  In the image forming apparatus of FIG. 10, the photosensitive drum 1 rotates in the direction of arrow I, and the surface of the photosensitive drum 1 is uniformly and uniformly charged by the charging device (for example, charging roller) 2 (for example, charging potential: −). 400V). Next, the exposure device 3 irradiates the surface of the photosensitive drum 1 with, for example, laser light 3a corresponding to the image information, thereby forming an electrostatic latent image on the photosensitive drum 1 (for example, exposure portion potential: −50 V). .

  Next, the electrostatic latent image on the photosensitive drum 1 is negatively charged by a developing sleeve 4 a (for example, DC: −250 V, AC: 1 KVpp / 2.5 KHz) that rotates by applying a bias of the developing device 4. Toner K is developed. In this way, a toner K image is formed on the portion of the photosensitive drum 1 irradiated with the laser light.

  The toner K image on the photosensitive drum 1 is taken out from the paper feed cassette 9 by a plus voltage (for example, DC: +2 KV) applied to a transfer device (for example, transfer roller) 5 and is conveyed to the transfer unit through the path J. Is electrostatically transferred onto the sheet P. Thereafter, the sheet P carrying the toner K image is discharged from the positive charge of the sheet P by a minus voltage (for example, DC: −1 KV) applied to the separation device (for example, a charge eliminating needle) 6, thereby causing a photosensitive drum. The recording material P is separated from 1. Then, the paper P carrying the toner K image is conveyed to the fixing device 100 and receives the heat and pressure to fix the toner K image on the paper P. After the fixing process is completed, the paper P is discharged by selecting face-up discharge in the path L or face-down discharge in the path M.

  On the other hand, the photosensitive drum 1 that has completed the transfer process, after the transfer residual toner on the photosensitive drum 1 is removed by the cleaning device 7, is uniformly charged again by the charging device 2 to prepare for the next image formation.

  Next, the fixing device in FIG. 1 will be described.

  As shown in FIG. 1, the fixing device 100 includes a fixing roller 101 as a fixing member (heating member) and a pressure roller 102 as a pressure member. Further, halogen heaters 111 a and 111 b as heating sources for heating the fixing roller 101 and halogen heaters 112 a and 112 b for heating the pressure roller 102 are provided. Further, a first temperature sensor 121a as a first temperature detection member that detects the temperature of the center (first position) in the longitudinal direction of the surface of the fixing roller 101, and a second temperature detection that detects the temperature of the end (second position). A second temperature sensor 121b is provided as a member. And the temperature sensor 122a which detects the temperature of the center part of the pressure roller 102 surface, and 122b which detects the temperature of an edge part are provided.

  Further, a power supply 131 that supplies power to the halogen heaters 111a, 111b, 112a, and 112b, and a heater control unit 130 serving as a power control unit that controls the power supplied to the halogen heaters 111a, 111b, 112a, and 112b are provided. The longitudinal direction is a direction perpendicular to the transport direction of the paper P.

  The fixing roller 101 is rotationally driven in a direction indicated by an arrow A by a driving source (not shown) at a predetermined speed, for example, a peripheral speed of 500 mm / sec. For example, the fixing roller 101 has a thickness of 3 mm of silicone rubber as a heat-resistant elastic layer on a metal cylindrical cored bar (made of aluminum in this embodiment) having an outer diameter of 74 mm, a thickness of 6 mm, and a length of 350 mm. Covered. Further, on the elastic layer, in order to improve the releasability with the toner, a fluorine-based resin (in this embodiment, a PFA tube) as a heat-resistant release layer is coated with a thickness of 100 μm.

  In this embodiment, the fixing roller 101 coated with an elastic layer is used. However, a fixing roller coated with a release layer on a metal cylindrical core metal without an elastic layer may be used.

  In addition, halogen heaters 111 a and 111 b are disposed inside the cored bar of the fixing roller 101.

  The surface temperature of the fixing roller 101 is detected by the first temperature sensor 121a or the second temperature sensor 121b that contacts the fixing roller 101. The heater control unit 131 controls the power supply 131 based on the detected temperature (result) of the first temperature sensor 121a or the second temperature sensor 121b, and performs ON / OFF control of the halogen heaters 111a and 111b.

  The pressure roller 102 is pressed to the fixing roller 101 with a predetermined pressure by a pressing unit (not shown) to form a nip N with the fixing roller 101. Then, it is driven to rotate with the fixing roller 101 in a direction indicated by an arrow B at a predetermined speed, for example, a peripheral speed of 500 mm / sec.

  In the pressure roller 102, for example, a silicone rubber as a heat-resistant elastic layer is coated with a thickness of 3 mm on a metal cylindrical cored bar having an outer diameter of 54 mm, a thickness of 3 mm, and a length of 350 mm. Further, on the elastic layer, a fluorine resin as a heat-resistant release layer is coated with a thickness of 100 μm in order to improve the release property with the toner. In the pressure roller 102 of this embodiment, the core is made of iron, and the heat-resistant release layer is a PFA tube.

  In addition, halogen heaters 112a and 112b as heating sources are disposed inside the pressure roller 102.

  The surface temperature of the pressure roller 102 is detected by a temperature sensor 122a or 122b that contacts the pressure roller 102.

  The heater control unit 131 controls the power supply 131 based on the detection result of the temperature sensor 122a or the second temperature sensor 122b, and performs ON / OFF control of the halogen heaters 112a and 112b.

  The paper P carrying the unfixed toner K by the image forming apparatus is conveyed to the nip N, and the toner K is fixed on the paper P by the heat and pressure of the nip N.

  As shown in FIG. 2, the fixing device 100 is a central reference fixing device through which the paper P is passed through substantially the center in the longitudinal direction of the fixing roller 101 and the pressure roller 102. On the outer peripheral surface of the fixing roller 101, the first temperature sensor 121 a is disposed in the sheet passing portion E of the paper P 2 having the minimum width E, and the second temperature sensor 121 b is disposed at the end of the fixing roller 101. Detect the surface temperature of.

  In the present embodiment, the second temperature sensor 121b is disposed in the non-sheet passing portion F of the sheet P1 having the maximum width D for the purpose of measuring the temperature of the fixing roller 101 in the non-sheet passing portion.

  As shown in FIG. 3, it is not necessary to detect the temperature rise of the non-sheet passing portion having the maximum width D, and when the temperature rise of the non-sheet passing portion of the paper having a width smaller than the maximum width D is detected, the second The temperature sensor 121b may be disposed in the non-sheet passing area of the paper P2 having the minimum width E and in the sheet passing area having the maximum width D. Further, it may be configured to be disposed at the inner end of the paper passing area having the maximum width D.

  Here, referring back to FIG. 1, the heater control unit 130 that performs temperature control of the present embodiment will be described. The heater control unit 130 includes a microcomputer (CPU), a memory (ROM) as storage means, and the like, and detects detection signals from the first temperature sensor 121a and the second temperature sensor 121b at predetermined time intervals to detect the detected temperature. Convert to Based on the detected temperature, the heater controller 130 controls the energization amount to the halogen heaters 111a and 111b, thereby controlling the temperature of the fixing roller 101 to a predetermined temperature. For example, when the detected temperature is lower than the target temperature, predetermined power is supplied (ON) to the halogen heaters 111a and 111b to raise the temperature of the fixing roller 101. When the detected temperature is higher than the target temperature, the energization to the halogen heaters 111a and 111b is cut off (OFF) to lower the fixing roller 101 temperature.

  FIG. 4 is a schematic diagram showing the detected temperature of the first temperature sensor 121a of the fixing roller 101 on the vertical axis and the state of the fixing device over time on the horizontal axis from the power-on of the image forming apparatus.

  As shown in FIG. 4, when the image forming apparatus is turned on (H1), the halogen heaters 111a, 111b, 112a, 111b of the fixing apparatus 100 are turned on, and the fixing roller 101 is heated from room temperature to a standby temperature, for example, 200 ° C. H1 to H2 to be caused are in a rising state.

  In the standing state, for example, when the fixing roller temperature is from room temperature to 150 ° C., the temperature is raised while the rotation of the fixing roller 101 is stopped. From 150 ° C. to 200 ° C., the fixing roller 101 and the pressure roller 102 are rotationally driven to raise the temperature, thereby reducing the temperature unevenness in the circumferential direction of the fixing roller 101 and the pressure roller 102. In the startup state, the heater control unit 130 performs temperature control according to the temperature detected by the first temperature sensor 121a.

  When the temperature reaches the standby temperature in H2, the process shifts to a standby state of H2 to H3 for controlling the temperature of the fixing roller 101 to the standby temperature. When the standby state is entered, the fixing device 100 can perform the fixing operation, and the image forming apparatus can form an image. In the standby state, the temperature control of the fixing roller 101 is performed by the standby control which is a feature of the present invention. . Although standby control will be described later, the temperature sensors referred to by the heater control unit 130 to perform temperature control according to the detected temperature (output) of the first temperature sensor are the first temperature sensor 121a and the second temperature sensor 121b. One is selected. In the above-described startup state, the heater control unit 130 performs temperature control according to the temperature detected by the first temperature sensor 121a. The fixing (heating) operation is started at H3, and the fixing roller 101 is shifted to a fixing state of H3 to H4 in which the temperature is controlled to a fixing temperature, for example, 180 ° C. When shifting to the fixing state, the heater control unit 130 controls the temperature of the fixing roller 101 according to the temperature detected by the first temperature sensor 121a, as in the standing state. The fixing temperature is the temperature of the fixing roller 101 during the fixing (heating) operation.

  After completion of the fixing (heating) operation, the process again shifts to a standby state at H4 to H5, and the temperature control of the fixing roller 101 is performed by the above-described standby control. When the standby state continues for a predetermined time or more, the process proceeds to the H5 to sleep state in which the halogen heaters 111a, 111b, 112a, and 111b of the fixing device 100 are turned off.

  Here, with reference to FIG. 5, the standby control, which is a feature of the present invention, will be described.

  The standby control is temperature control of the fixing roller 101 when the fixing device 100 is in a standby state. FIG. 5 shows a flowchart of control executed by the heater control unit 130.

  When the fixing device 100 enters a standby state (S1), the heater control unit 130 of the fixing device 100 compares the temperature detected by the first temperature sensor 121a with a standby temperature 1, for example, 200 ° C. (S2).

  In S2, when the temperature detected by the first temperature sensor 121a is lower than the standby temperature 1 (200 ° C.) (NO in S2), the temperature at the center of the fixing roller 101 is determined using the first temperature sensor 121a at the center of the fixing roller 101. Is controlled so that the standby temperature becomes 1 (200 ° C.). Specifically, the power supply 131 supplies (ON) predetermined power to the halogen heaters 111a and 111b to increase the temperature of the fixing roller 101. Then, it is determined whether or not the standby state is to be continued (S5), and when shifting to another control (NO in S5), for example, shifting to fixing control for performing a fixing operation or sleep control for turning off the heater for power saving is performed. In this case, the standby control is terminated and the process proceeds to another control. When the standby state is continued (YES in S5), the flow returns to S2 and the flow for comparing the detected temperature of the first temperature sensor 121a with the standby temperature 1 is repeated.

  In S2, when the temperature detected by the first temperature sensor 121a is equal to or higher than the standby temperature 1 (200 ° C.) (YES in S2), the temperature at the end of the fixing roller 101 is determined using the second temperature sensor 121b at the end of the fixing roller 101. Is controlled to a standby temperature of 2, for example, 190 ° C. Specifically, when the temperature detected by the second temperature sensor 121b is lower than 190 ° C., the power source 131 supplies (ON) predetermined power to the halogen heaters 111a and 111b to increase the temperature of the fixing roller 101. When the temperature detected by the second temperature sensor 121b is 190 ° C. or higher, the power supply 131 cuts off (turns off) the energization of the halogen heaters 111a and 111b, thereby lowering the temperature of the fixing roller 101. Then, it is determined whether or not the standby control is continued (S5), and when the control shifts to another control (NO in S5), the standby control is terminated and the control shifts to another control. When the standby control is continued (YES in S5), the process returns to S2 and the flow for comparing the detected temperature of the first temperature sensor 121a with the standby temperature 1 is repeated.

  Here, in this embodiment, the standby temperature 2 is set to a lower limit value 190 ° C. at which fixing ability can be secured in a low temperature environment, and the detected temperature at the first temperature sensor 121a in the equilibrium state at that time is 200 ° C. 1 was 200 degreeC.

  Accordingly, since the temperature drop at the end of the fixing roller 101 is smaller in the normal environment than in the low temperature environment, when the temperature detected by the first temperature sensor 121a is 200 ° C., the temperature detected by the second temperature sensor 121b is 190 ° C. or higher. . Then, the ON / OFF control of the heaters 111a and 111b based on the comparison between the detected temperature of the first temperature sensor 121a and the standby temperature 1 is the main control, and the temperature is controlled to the standby temperature 1 using the first temperature sensor 121a. It becomes the same behavior.

  Further, when the environmental temperature decreases from the normal environment to the low temperature environment, the end temperature decrease of the fixing roller 101 increases, and the heaters 111a and 111b are turned on and off by comparing the detected temperature of the second temperature sensor 121b with the standby temperature 2. Control is the main control. At this time, the detected temperature of the first temperature sensor 121a is 200 ° C. or higher, and the same behavior as the operation of controlling the temperature to the standby temperature 2 of 190 ° C. using the second temperature sensor 121b is obtained.

  In this embodiment, during standby, the first temperature sensor 121a at the center of the fixing roller 101 is always monitored, and temperature control is performed so that the first temperature sensor in the sheet passing area becomes the standby temperature 1 (200 ° C.). Further, the temperature is controlled so that the second temperature sensor 121b at the end of the fixing roller 101 has a standby temperature 2 (190 ° C.). In this way, the fixing roller 101 can always maintain a predetermined temperature (190 ° C.) or higher within the maximum width sheet passing region (D) regardless of the environment. Therefore, when shifting from the standby state to the fixing state, it is possible to ensure the fixing property across the entire sheet even in a low temperature environment.

  By the way, when shifting to the fixing operation, the temperature of the fixing roller 101 is taken by the paper P and decreases. Particularly when the core of the fixing roller 101 is thick and the fixing roller 101 is covered with an elastic layer, it takes time for the amount of heat to reach the surface of the fixing roller 101 even when the heaters 111a and 111b are turned on. The temperature drop of the fixing roller 101 due to the passing of the paper P is large.

  Therefore, in this embodiment, “standby temperature 1 (200 ° C.) is higher than the fixing temperature (180 ° C.)” and the core metal temperature of the fixing roller 101 is maintained at a high temperature during standby.

  This is because, even when the fixing operation is started and the surface temperature of the fixing roller 101 is lowered to the fixing temperature (180 ° C.), the heaters 111a and 111b are turned on according to the detection result of the first temperature sensor 121a. Is configured to be able to be maintained at the fixing temperature (180 ° C.).

  That is, since the cored bar of the fixing roller 101 is kept at a high temperature during standby, even if the surface temperature of the fixing roller 101 is lowered, the heat of the cored bar immediately reaches the surface, and the surface temperature of the central part is equal to the fixing temperature ( 180 ° C.).

  In this way, by maintaining the end portion of the fixing roller 101 at 190 ° C. or higher by the second temperature sensor 121b during standby, the central portion of the fixing roller 101 is maintained at a fixing temperature of 180 ° C. during fixing. . At that time, the end portion of the fixing roller 101 can be maintained at 170 ° C. or higher at which fixing ability can be secured.

  Therefore, by maintaining the end of the fixing roller 101 at 190 ° C. or higher during standby, the end of the fixing roller 101 can be set at 170 ° C. or higher at which fixing can be ensured during fixing.

  As Comparative Example 1 of standby control according to the present exemplary embodiment, in a configuration in which only the temperature of the fixing roller 101 is controlled to the standby temperature 1 (200 ° C.) by the first temperature sensor 121a during standby, the fixability is low. A problem occurs. This is because, in a low temperature environment, the heat radiation amount at the end of the fixing roller 101 becomes large, and the temperature becomes less than 190 ° C. at which the fixing property can be secured at the end of the fixing roller 101.

  Further, since heat is generated from the end portion of the fixing roller 101 even at the time of start-up, the temperature at the center portion of the fixing roller 101 is usually high and the end portion temperature is low. Furthermore, since the temperature of the entire fixing device is low at the time of start-up, the amount of heat released from the end is large, and the amount of temperature decrease at the end is large compared to that during standby.

  In particular, when an overshoot occurs in which the central temperature of the fixing roller 101 greatly exceeds the standby temperature 1 at the start-up, the control shifts to the standby control after the start-up, and the detected temperature of the first temperature sensor 121a becomes the standby temperature 1. The heaters 111a and 111b are turned off until the pressure decreases to the maximum.

  As a result, the temperature detected by the second temperature sensor 121b at the end of the fixing roller 101 becomes less than 190 ° C. at which the fixability can be secured, and the fixability at the end of the paper P during fixing is reduced.

  As a comparative example 2 of standby control in this embodiment, when the configuration in which the temperature of the fixing roller 101 is only controlled to the standby temperature 2 (190 ° C.) by the second temperature sensor 121b during standby is used, fixing during fixing is performed. It becomes low. This is because the temperature at the end of the fixing roller 101 rises due to the temperature rise of the non-sheet passing portion during the standby after passing through the small size paper, and the temperature becomes less than 190 ° C. at which the fixing property can be secured at the center portion of the fixing roller 101. This is because fixability at the time of fixing is lowered.

  Here, FIG. 6 is a schematic diagram showing a temperature distribution in the longitudinal direction of the fixing roller 101 according to the first embodiment of the present invention. The vertical axis represents the temperature of the fixing roller 101, and the horizontal axis represents the fixing roller position.

  The thick line G1 indicates the temperature distribution in the equilibrium state during standby, and the thin line G2 indicates the temperature distribution during standby immediately after passing the minimum width (E) size paper.

  As indicated by G2 in FIG. 6, the temperature distribution of the fixing roller 101 after passing through the small-size paper is increased by the fixing temperature of 180 ° C. in the paper passing area and the non-paper passing area is increased by the temperature rise in the non-paper passing section. The detection temperature of the temperature sensor 121b is 220 ° C. In this state, when the temperature of the fixing roller 101 is controlled at the standby temperature 2 (190 ° C.) by the second temperature sensor 121b of the comparative example 2, the heaters 111a and 111b are moved until the temperature detected by the second temperature sensor 121b reaches 190 ° C. It becomes OFF. Therefore, since the temperature of the fixing roller 101 in the central portion of the sheet passing area is lower than 190 ° C., there arises a problem that the fixing property at the time of fixing is deteriorated in the central portion.

  By performing the above-described standby control during standby, even if the fixing roller 101 has a history such as overshoot after start-up or non-sheet passing portion temperature increase after fixing, the fixing roller 101 does not depend on the environmental temperature. A predetermined temperature or higher can be secured in the entire longitudinal direction, and good fixability can be obtained during fixing.

  In this embodiment, if the standby temperature 1 ≦ the standby temperature, the temperature at the end of the fixing roller 101 during standby is usually low, so the temperature is controlled by the second temperature sensor 121b at the end of the fixing roller 101. For this reason, depending on the degree of temperature decrease at the end of the fixing roller 101 and the previous history, the temperature at the center of the fixing roller during standby may be less than 200 ° C. For example, when printing thick paper, the temperature at the center is decreased. This causes a problem that the fixing property is deteriorated.

  When standby temperature 1 = standby temperature 2 = 200 ° C., the temperature of the fixing roller 101 is higher than necessary, so that power consumption during standby increases and energy saving cannot be achieved.

  Therefore, as in this embodiment, if “standby temperature 1 (200 ° C.)> Standby temperature 2 (190 ° C.)”, the temperature of the center portion of the fixing roller 101 is maintained at 200 ° C. or higher and at the same time the end portion. Can be maintained at 190 ° C. or higher. In this way, it is more preferable because both the central portion and the end portion can secure a certain level of fixability and save energy.

  In this embodiment, the standby temperature 1 is 200 ° C. and the standby temperature 2 is 190 ° C., but may be arbitrarily set depending on the configuration of the fixing device. Although the fixing temperature is set to 180 ° C. and lower than the standby temperature 1, the fixing temperature may be set to 210 ° C. and higher than the standby temperature 1 depending on the fixing device configuration. Further, a plurality of fixing temperatures may be used, such as 180 ° C. when the paper is thin and 190 ° C. when the paper is thick.

  However, in the case of “standby temperature 1 ≧ fixing temperature”, since the paper reaches the fixing device as soon as printing is started, the temperature distribution of the fixing roller 101 during standby tends to affect the fixability. The effect of the invention is great.

  On the other hand, in the case of “standby temperature <fixing temperature”, when a fixing operation is performed at the start of printing, the heaters 111a and 111b are turned on to increase the temperature of the fixing roller 101 and increase the end temperature of the fixing roller 101. For this reason, it is possible to secure the fixability of the end portion by setting the fixing temperature high or the like, so that the effect is reduced as compared with the case of “standby temperature 1 ≧ fixing temperature”.

  In this embodiment, the temperature control during standby is described. However, when the temperature of the fixing roller 101 is raised from room temperature to a predetermined temperature (standby temperature or fixing temperature), the temperature is detected by the first temperature sensor 121a. It is good to control.

  This is because the temperature distribution of the fixing roller 101 is high at the center and the temperature at the end is low even at the time of start-up. In other words, the temperature control at the central high temperature part is smaller than the temperature control at the low temperature part at the end, and the overshoot that causes the fixing roller temperature to rise above the predetermined temperature is reduced. This is because it can be done.

  Further, even during fixing, the temperature of the sheet passing area can be maintained at the fixing temperature by controlling the temperature of the fixing roller 101 to the fixing temperature using the first temperature sensor 121a that is the sheet passing area. Can be secured.

  Therefore, it is preferable to control the temperature using the first temperature sensor 121a at the time of start-up, the first temperature sensor 121a and the second temperature sensor 121b at the time of standby, and the first temperature sensor 121a at the time of fixing.

[Example 2]
A second embodiment according to the present invention will be described with reference to FIGS.

  About the member of the same structure and function as Example 1, the same number as Example 1 is attached | subjected and description is abbreviate | omitted. Also in this embodiment, at the time of standby, the temperature control of the fixing roller 101 is performed by the standby control described in the first embodiment.

  In this embodiment, the halogen heater 111a (referred to as the first halogen heater 111a) of the fixing roller 101 is, for example, 600 W, and the heat generation amount at the center as shown in FIG. A central high heater having a heat generation distribution is used. On the other hand, as the halogen heater 111b (referred to as the second halogen heater 111b), for example, 600 W, an end portion having a heat generation distribution of 30% at the center portion when the heat generation amount at the end portion as shown in FIG. Use a high heater. In this embodiment, the halogen heaters 111a and 111b have the same total calorific value.

  The temperature of both the first heater 111a and the second heater 111b is controlled in order to quickly rise at the time of start-up, that is, to shorten the warm-up time, or to quickly supply the amount of heat lost to the paper at the time of fixing. Used for.

  On the other hand, at the time of standby, that is, when standby control is executed, the first halogen heater 111a that is the central high heater is always turned off and is not used for temperature control, and only the second halogen heater 111b that is the end high heater is turned on and off. Used for temperature control.

  Therefore, at the time of standby, by using the heater 111b that generates a large amount of heat at the end portion, the temperature drop due to heat radiation at the end portion of the fixing roller 101 can be reduced, so that the fixability of the paper end portion during fixing can be improved. Further, by reducing the temperature drop at the end of the fixing roller 101, for example, when the temperature is controlled by the second temperature sensor 121b during standby at a low temperature, the temperature rise at the center can be reduced. Can be made uniform, and the fixability in the paper at the time of fixing can be made uniform.

  Therefore, by setting “first heater 111a power consumption <second heater 111b power consumption” during standby, the temperature drop at the end of the fixing roller 101 is reduced, and the fixability of the paper end at the time of fixing is improved. Fixability can be made uniform.

  Depending on the configuration of the fixing device, the first heater 111a is not always turned off during standby, and the second heater 111b is turned on, for example, the first heater 111a is turned on for 2 seconds and turned off for 2 seconds to turn on 50%. And so on.

Example 3
FIG. 1 and Example 3 according to the present invention will be described.

  About the member of the same structure and function as Example 1, the same number as Example 1 is attached | subjected and description is abbreviate | omitted. Also in this embodiment, at the time of standby, the temperature control of the fixing roller 101 is performed by the standby control described in the first embodiment.

  In the present embodiment, in the case of the fixing device 100 of FIG. 1 in the standby state, the fixing roller 101 and the pressure roller 102 are separated from each other without being affected by heat from the pressure roller 102. More precisely, the temperature of the fixing roller 101 is controlled.

  When the fixing roller 101 and the pressure roller 102 are in a pressure contact state during standby, there is a problem in that the temperature of the fixing roller 101 cannot be accurately controlled when the positions of the temperature sensors 121a and 121b are relatively close to the nip N. There has occurred. This is because, for example, since the standby temperature of the fixing roller 101 is 200 ° C. and the standby temperature of the pressure roller 102 is 130 ° C., the heat of the fixing roller 101 is taken away by the pressure roller in the nip N.

  This is because the temperature distribution in the longitudinal direction of the pressure roller 102 also decreases at the end due to heat radiation from the end. When the pressure roller 102 is in pressure contact with the fixing roller 101 in this state, the amount of heat taken by the pressure roller 102 by the pressure roller 102 at the nip N is small at the center of the fixing roller 101 and large at the end. Therefore, at the end portion of the fixing roller 101, the end portion temperature further decreases due to the amount of heat taken away by the pressure roller 102 in addition to heat radiation.

  Accordingly, the temperature control during standby is maintained at the standby temperature 2 (for example, 190 ° C.) by the second temperature sensor 121b at the end of the fixing roller 101, so that the temperature at the center of the fixing roller 101 increases. . As a result, the temperature distribution in the longitudinal direction of the fixing roller 101 cannot be made uniform, and the fixability cannot be made uniform.

  This is because the fixing property can be secured over the entire area of the paper P, but the fixing property at the central portion becomes too high, the glossiness at the central portion is high, and the glossiness at the edge portion is low, that is, gloss unevenness. Will occur.

  Therefore, the fixing roller 101 and the pressure roller 102 are separated from each other during standby. As a result, since the thermal influence on the fixing roller 101 by the pressure roller 102 can be eliminated, the temperature of the fixing roller 101 is accurately controlled, and the temperature in the longitudinal direction is not increased without increasing the temperature of the central portion. Uniformity can be achieved, fixing properties can be made uniform, and uneven gloss can be prevented.

  Further, when the fixing roller 101 and the pressure roller 102 are kept in a pressed state during standby, the elastic layer of each roller is deformed in the nip N, and the trace becomes uneven glossiness of the image. Problem occurs. However, this problem can be prevented by separating the fixing roller 101 and the pressure roller 102 from each other.

Example 4
Embodiment 4 according to the present invention will be described with reference to FIG.

  FIG. 9 is a schematic front view of an example of the external heat fixing device according to the fourth embodiment of the present invention. Although described along FIG. 9, members having the same configuration and function as those of the first embodiment are denoted by the same reference numerals and description thereof is omitted. Also in this embodiment, at the time of standby, the temperature control of the fixing roller 101 is performed by the standby control described in the first embodiment.

  As shown by the fixing device 200 in FIG. 9, an external heating fixing device that heats the fixing roller 101 with an external heating roller 103 as an external heating member has been proposed.

  The external heating roller 103 is pressed to the fixing roller 101 with a predetermined pressure by a not-shown pressing unit to form a nip N1 with the fixing roller 101, and has a predetermined speed in the direction of arrow C, for example, 500 mm / The fixing roller 101 is driven to rotate at a peripheral speed of sec.

  The external heating roller 103 has, for example, a 50 μm fluorine resin as a heat-resistant release layer on a metal cylindrical cored bar having an outer diameter of 30 mm, a thickness of 3 mm, and a length of 350 mm in order to improve releasability from the toner. Covered with thickness. In the external heating roller 103 of this embodiment, the core metal is made of aluminum, and the heat-resistant release layer is a PFA tube.

  In addition, halogen heaters 113a and 113b as heating sources are arranged inside the external heating roller 103.

  The surface temperature of the external heating roller 103 is temperature-controlled by the heater control unit 130 based on the detection value of the temperature sensor 123a or 123b that contacts the external heating roller 103. In this temperature control, the heater control means 130 turns on / off the power supply 131 that supplies power to the halogen heaters 113a and 113b according to the temperature detected by the temperature sensor 123a or 123b, and sets the surface temperature of the external heating roller 103 to a predetermined value. The temperature is set to 220 ° C. in this embodiment.

  Also in such a fixing device 200, the temperature of the fixing roller 101 is accurately controlled by the configuration in which the fixing roller 101 and the pressure roller 102 are separated from each other and the fixing roller 101 and the external heating roller 103 are separated from each other during standby. can do. This is because the thermal influence that the fixing roller 191 receives from the external heating roller 103 during standby can be reduced.

  When the fixing roller 101 and the external heating roller 103 are in a pressure contact state during standby, the temperature of the fixing roller 101 cannot be accurately controlled when the positions of the temperature sensors 121a and 121b are relatively close to the nip N1. There has occurred. For example, if the standby temperature of the fixing roller 101 is 200 ° C. and the standby temperature of the external heating roller 103 is 220 ° C., the heat of the external heating roller 103 flows into the fixing roller 101 at the nip N1.

  This is because, for example, the temperature distribution in the longitudinal direction of the external heating roller 103 also causes a temperature drop at the end due to heat radiation from the end. In this state, when the external heating roller 103 is pressed against the fixing roller 101, the amount of heat that the external heating roller 103 gives to the fixing roller 101 at the nip N1 is large at the center of the fixing roller 101 and small at the end.

  Therefore, the temperature of the fixing roller 101 is high at the center portion and is decreased at the end portion.

  In the standby temperature control, the standby temperature 2 (for example, 190 ° C.) is maintained by the second temperature sensor 121b at the end of the fixing roller 101. As a result, the temperature at the center of the fixing roller 101 rises, the temperature distribution in the longitudinal direction of the fixing roller 101 cannot be made uniform, and the fixability cannot be made uniform.

  As described above, the fixing property can be secured over the entire area of the paper P, but the fixing property at the central portion becomes too high, the glossiness at the central portion is high, and the glossiness at the edge portion is low. That is, the problem of uneven glossiness occurs.

  Therefore, in the standby state, the fixing roller 101 and the pressure roller 102 are separated from each other, and further, the fixing roller 101 and the external heating roller 103 are separated from each other, so that the longitudinal temperature distribution can be made uniform and the fixing property can be made uniform. Further, the occurrence of uneven gloss can be prevented. By separating the pressure roller 102 and the external heating roller 103 from each other, the thermal influence of the pressure roller 102 and the external heating roller 103 on the fixing roller 101 is reduced. This is because it is possible to prevent the temperature from rising.

  Further, when the fixing roller 101 and the external heating roller 103 are kept in a pressurized state during standby, the elastic layer of the fixing roller 101 is deformed in the nip N1, and the trace becomes uneven glossiness of the image. Problem occurs. However, this problem can also be prevented by separating the fixing roller 101 and the external heating roller 103 from each other.

In the above, although the Example of this invention was described,
The numerical values and schematic diagrams in the first to fourth embodiments of the present invention are examples for simplifying the description of the embodiments, and can be arbitrarily determined according to the configuration and settings of the fixing device.

  Further, the present invention is not limited to the fixing device described in the embodiments, and can be applied to other forms of fixing devices such as arbitrarily combining the embodiments.

  In the present embodiment, the contact type temperature sensor is used as the temperature sensor, but the effect of the present invention is the same even when a non-contact type temperature sensor is used.

  In this embodiment, the roller system has been described, but the same effect can be obtained by using a belt system (fixing belt, pressure belt, external heating belt).

  In this embodiment, the temperature control of the fixing roller during standby has been described. However, the present invention can be similarly applied to the temperature control of the pressure roller and the external heating roller, and the effect of maintaining the longitudinal temperature at a predetermined temperature or more is the same. is there.

1 is a schematic front view illustrating an example of a fixing device according to Embodiment 1 of the present invention. 1 is a schematic side view illustrating an example of a fixing device according to a first embodiment of the present invention. FIG. 5 is a schematic side view illustrating another example of the fixing device according to the first exemplary embodiment of the present invention. FIG. 3 is a schematic diagram illustrating a fixing device state. It is a control flowchart concerning Example 1 of the present invention. FIG. 3 is a schematic diagram illustrating a longitudinal temperature distribution of a fixing roller according to Embodiment 1 of the present invention. It is a schematic diagram of heat generation distribution of the first heater 111a according to the second embodiment of the present invention. It is a schematic diagram of heat generation distribution of the second heater 111b according to the second embodiment of the present invention. It is a schematic diagram of the front view which shows an example of the external heating fixing device which concerns on Example 4 of this invention. 1 is a schematic diagram illustrating an example of an image forming apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Fixing device 200 External heating fixing device 101 Fixing roller 102 Pressure roller 103 External heating roller 111a, 111b Fixing heater 112a, 112b Pressing heater 113a, 113b External heating heater 121a Fixing roller first temperature sensor 121b Fixing roller second temperature sensor 122a, 122b Pressure roller temperature sensor 123a, 123b External heating roller temperature sensor 130 Heater control unit 131 Power supply P sheet P1 maximum width sheet P2 minimum width sheet K toner

Claims (5)

A heating member for heating the toner image on the recording material;
A heating source that is supplied with electric power to raise the temperature of the heating member;
A first temperature detecting member for detecting a temperature of a central portion in the longitudinal direction of the heating member;
An image forming apparatus having a second temperature detection member for detecting a temperature of an end portion in a longitudinal direction of the heating member;
Depending on the output of the first temperature detecting member until the temperature of the central portion rises to a predetermined temperature, depending on the output of the second temperature detecting member after the temperature of the central portion rises to the predetermined temperature. An image heating apparatus comprising power control means for controlling power supplied to the heating source.   2. The image heating apparatus according to claim 1, wherein the predetermined temperature is higher than a temperature of the heating member when the heating member performs a heating operation of a toner image.   3. The power control unit controls power supplied to the heating source according to an output of the first temperature detection member when the heating member performs a heating operation of a toner image. Any one of the image heating apparatus. The heating source includes a first heater having a calorific value at a central portion in the longitudinal direction larger than a calorific value at an end portion;
A second heater having a heat generation amount at an end portion in the longitudinal direction larger than a heat generation amount at a center portion in the longitudinal direction;
4. The image forming apparatus according to claim 1, wherein when the power control unit performs the control, the power supplied to the second heater is larger than the power supplied to the first heater. 5.   An external heating member that contacts the surface of the heating member that heats the toner image and that heats the heating member, and when the power control means performs the control, the external heating member is separated from the heating member. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.

Images