JP2006337488A - Control method of fixing device, and fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control method of a fixing device capable of improving the accuracy of temperature control of a pressurization object by changing the correction coefficient of the temperature detected by a contactless temperature detecting means according to a warming up degree of the fixing device. <P>SOLUTION: The fixing device 50 is equipped with a rotatable heating object 12 which heats and fixes a toner image, the pressurization object 24 which is brought into pressure contact with the heating object 12 to form a nip section 30 therebetween, first temperature detecting means 20a, 20b which detect the temperature of the heating object 12, a second temperature detecting means 44 which is arranged in proximity to the pressurization object 24 without contact therewith in order to detect the temperature of the pressurization object 24, and a controller 72 which subjects the heating object 12 and the pressurization object 24 respectively to the temperature control, in which the controller 72 determines the correction coefficient R based on the detection temperatures 20a, 20b of the first temperature detecting means, determines the temperature T' after correction of the pressurization object 24 by multiplying the detection temperature T of the second temperature detecting means 44 by the correction coefficient R, and controls the temperature of the pressurization object 24 based on the temperature T' after the correction. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fixing device control method, a fixing device, and an image forming apparatus used for an electrophotographic copying machine, a printer, and the like.

Conventionally, in an electrophotographic image forming apparatus, a fixing device for heat-fixing a toner image formed on a sheet surface is used. As the fixing device, for example, Patent Document 1 discloses a fixing device shown in FIG. The fixing device 10 includes, for example, a resin endless sheet-like fixing belt 12. The fixing belt 12 is stretched between a rotatable heating roller 14 and a nip forming member 16 fixedly disposed so as not to rotate in a state where a predetermined tension is applied.
JP 2004-286924 A

  For example, a heater such as a halogen lamp (hereinafter referred to as “heating heater”) 18 is built in the heating roller 14 formed of a metal cylinder. A thermistor 20 is disposed in contact with the outer surface of the heating roller 14.

  The nip forming member 16 is formed of, for example, a heat resistant resin and extends so as to support the entire width of the fixing belt 12. A back-up member 22 made of, for example, a metal rod is disposed on the back surface of the nip forming member 16, and the back-up member 22 prevents the nip forming member 16 from being bent in a direction perpendicular to its longitudinal direction. .

  A pressure roller 24 is in pressure contact with the portion of the fixing belt 12 supported by the nip forming member 16. The pressure roller 24 is rotationally driven in the direction of arrow A. The pressure roller 24 has a two-layer structure including, for example, a metal cylindrical cored bar 26 that forms an inner layer, and an elastic layer 28 such as silicone rubber bonded to the outer peripheral surface of the cored bar 26. .

  The surface of the nip forming member 16 facing the pressure roller 24 is formed as a concave curved surface having a radius of curvature (for example, 15.4 mm) that is substantially the same as the radius (for example, 15 mm) of the pressure roller 24. Accordingly, a wide nip portion 30 having a length of, for example, 9 mm along the circumferential direction of the pressure roller 24 is formed between the fixing belt 12 and the pressure roller 24 that are in contact with each other.

  In the fixing device 10 configured as described above, the fixing belt 12 rotates in the arrow B direction when the pressure roller 24 is rotationally driven in the arrow A direction. At this time, the heating roller 14 rotates in the direction of arrow C according to the rotation of the fixing belt 12, but the fixing belt 12 slides along the surface of the nip forming member 16 because the nip forming member 16 is fixed so as not to rotate. Will do.

  The heating roller 14 is heated from the inside by a heating side heater 18. By controlling the heating side heater 18 on and off while monitoring the temperature with the thermistor 20, the heating roller 14 is heated and maintained at about 190 ° C., for example. By transferring heat from the heating roller 14 thus heated, the rotating fixing belt 12 is heated to, for example, about 170 ° C. over its entire circumference.

  When the fixing belt 12 is heated to about 170 ° C., the fixing device 10 is ready for fixing. In this state, when a sheet carrying a toner image on the surface is introduced into the nip portion 30 from the lower side and conveyed upward, the toner image in contact with the fixing belt 12 is heat-fixed on the sheet.

  In the above-described fixing device 10, the pressure roller 24 does not have a heating source. However, like the fixing device 40 shown in FIG. 5, the pressure roller 24 also has a heater such as a halogen lamp (hereinafter referred to as “pressure side heater”). Some have built-in 42). The reason why the pressure side heater 42 is provided on the pressure roller 24 is that the paper passing through the nip portion 30 is also heated from the back side to improve the fixing performance, and the paper per unit time when the paper is continuously fed. If the surface temperature of the pressure roller 24 decreases due to an increase in the amount of heat taken and the temperature difference between the nip portion 30 and the fixing belt 12 increases, the amount of paper curl after fixing increases, so the pressure roller 24 is positively activated. For example, the amount of curling is suppressed by heating automatically.

  In this fixing device 40, the thermistor 44 is disposed in contact with the outer peripheral surface of the pressure roller 24, and the pressure side heater 42 is turned on and off based on the temperature detected by the thermistor 44, thereby controlling the surface temperature of the pressure roller 44. The temperature is controlled to be raised and maintained at about 120 ° C.

  In the fixing device 40, since the thermistor 44 is disposed in contact with the rotating pressure roller 24, the surface of the elastic layer 28 of the pressure roller 24 and the contact surface of the thermistor 44 wear. When the thermistor 44 wears, the temperature detection performance changes, and when the pressure roller 24 wears, it causes image noise. Further, when the thermistor 44 is in contact with the pressure roller 24, paper dust, toner, and the like accumulate and solidify between the thermistor 44 and the pressure roller 24, and further damage the pressure roller 24, Such foreign matter may be carried and adhere to the image.

  In order to solve such a problem, the thermistor 44 is disposed in close proximity to the pressure roller 24 in a non-contact manner, and the detected temperature of the thermistor 44 is multiplied by a correction coefficient corresponding to the distance to the pressure roller 24. It is conceivable to obtain the temperature of the pressure roller 24. However, when the thermistor 44 is arranged in non-contact with the pressure roller 24, the detected temperature of the thermistor 44 is affected by the ambient temperature in the vicinity thereof, so the detected temperature of the thermistor 44 is multiplied by a certain correction coefficient. However, there is a problem that an accurate temperature of the pressure roller 24 cannot be obtained. If the accurate temperature of the pressure roller 24 cannot be obtained, the temperature of the pressure roller 24 cannot be accurately controlled.

  On the other hand, since the ambient temperature in the vicinity of the thermistor 44 changes depending on the warming condition of the fixing device 40, the temperature of the pressure roller 24 can be detected more accurately by changing the correction coefficient depending on the warming condition of the fixing device 40. become.

  Accordingly, the present invention provides a fixing device capable of improving the accuracy of temperature control of the pressure member by changing the correction coefficient of the temperature detected by the non-contact temperature detecting means according to the warming condition of the fixing device, and the control thereof. It is an object to provide a method.

In order to solve the above-described problems, the present invention provides a rotatable heating body that heats and fixes a toner image, and a rotatable pressure body that is in pressure contact with the heating body and forms a nip portion between the heating body. First temperature detection means for detecting the temperature of the heating body, second temperature detection means arranged in close proximity to the pressure body for detecting the temperature of the pressure body, and A control method of a fixing device including a heating unit and a control unit that adjusts the temperature of each of the pressure members,
The control unit determines a correction coefficient based on the temperature detected by the first temperature detection unit, multiplies the detection temperature of the second temperature detection unit by the correction coefficient, and obtains a corrected temperature of the pressurizing body, The temperature of the pressurizing body is controlled based on the corrected temperature.

  In the control method of the fixing device of the present invention, the first temperature detecting means includes two temperature detectors in contact with the heating body, and the control unit determines the two temperatures in order to determine the correction coefficient. You may use at least one of each detection temperature of a detector as a judgment element.

  In the fixing device control method of the present invention, the control unit may use the temperature detected by the second temperature detecting means as a determination factor in order to determine the correction coefficient.

The fixing device of the present invention includes a rotatable heating body that heats and fixes a toner image, a rotatable pressure body that is pressed against the heating body and forms a nip portion with the heating body, and the heating body First temperature detecting means for detecting the temperature of the pressurizing body, second temperature detecting means disposed in close proximity to the pressurizing body in order to detect the temperature of the pressurizing body, the heating body and the heating element. A fixing device including a controller for controlling the temperature of each pressure body,
The control unit determines a correction coefficient based on the temperature detected by the first temperature detection unit, multiplies the detection temperature of the second temperature detection unit by the correction coefficient, and obtains a corrected temperature of the pressurizing body, The temperature of the pressurizing body is controlled based on the corrected temperature.

  In the fixing device according to the aspect of the invention, the first temperature detection unit includes two temperature detectors in contact with the heating body, and the control unit is configured to determine the correction coefficient in order to determine the correction coefficient. At least one of the detected temperatures may be used as a determination factor.

  In the fixing device of the present invention, the control unit may also use the temperature detected by the second temperature detecting means as a determination factor in order to determine the correction coefficient.

  Furthermore, the present invention provides an image forming apparatus provided with the fixing device.

  In the fixing device control method and the fixing device of the present invention, the correction coefficient is determined based on the temperature detected by the first temperature detecting means. That is, the ambient temperature in the vicinity of the second temperature detection means is estimated based on the temperature detected by the first temperature detection means, and the correction coefficient is changed according to the estimated ambient temperature. In this way, the correction coefficient is changed according to the ambient temperature in the vicinity of the second temperature detection means arranged in a non-contact manner on the pressurized body, and the corrected temperature is obtained by multiplying the correction coefficient by the detection temperature of the second temperature detection means. As a result, the temperature of the pressurizing body can be detected more accurately, whereby the accuracy of temperature control of the pressurizing body by the control unit can be improved. As a result, there is no variation in the temperature of the pressure member, and the stability of the fixed image is improved.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 shows a schematic configuration of an image forming apparatus 100 using a fixing device 50 according to an embodiment of the present invention. The image forming apparatus 100 includes a photosensitive drum 52 that is driven to rotate in the direction of arrow D. Around the photosensitive drum 52, a charging device 54 for uniformly charging the surface of the photosensitive drum 52 in order along the rotation direction, and the surface of the uniformly charged photosensitive drum 12 is laser-exposed to form an electrostatic latent image. An exposure device 56 for forming the toner, a developing device 58 for developing the electrostatic latent image formed on the surface of the photosensitive drum 52 with toner into a toner image, and a transfer device for transferring the toner image from the photosensitive drum 52 to a sheet. 60 is disposed.

  A paper feed tray 62 is disposed below the image forming apparatus 100. The sheets P stacked and accommodated in the sheet feeding tray 62 are sent out one by one from the upper side to the sheet conveying path 66 by the sheet feeding roller 64. The sheet conveyance path 66 extends from the sheet feed roller 64 to the registration roller pair 68, the transfer portion between the photosensitive drum 52 and the transfer device 60, and the fixing device 50 to the discharge roller 70.

  In addition, the image forming apparatus 100 includes a control unit 72. The control unit 72 controls the operation of the entire image forming apparatus 100 and also controls the fixing device 50 as will be described later.

  In the image forming apparatus 100 having the above-described configuration, the surface of the photosensitive drum 52 is uniformly charged by the charging device 54 and then subjected to laser exposure according to the image data by the exposure device 56 to form an electrostatic latent image. . The electrostatic latent image is developed with toner by the developing device 58 to become a toner image. The toner image moves to a transfer portion that is a position facing the transfer device 60 according to the rotation of the photosensitive drum 52.

  The paper P sent out from the paper feed tray 62 to the paper transport path 66 by the paper feed roller 64 is temporarily stopped by the registration roller pair 68 and then sent to the transfer portion at a timing when the toner image moves to the transfer portion. In the transfer unit, the toner image is transferred from the photosensitive drum 52 to the surface of the paper P by the electrostatic action of the transfer device 60.

  Thereafter, the toner image is heated and fixed on the paper P on which the toner image is transferred when passing through the fixing device 50. Then, the paper P is discharged onto the paper discharge tray 76 by the paper discharge roller pair 70 through the paper discharge port 74.

Next, the fixing device 50 of this embodiment will be described including its control method.
The basic configuration of the fixing device 50 is substantially the same as the fixing device 40 described above with reference to FIG. That is, as shown in FIG. 2, the fixing device 50 includes, for example, a resin endless sheet-like fixing belt (heating body) 12. The fixing belt 12 is stretched between a rotatable heating roller 14 and a nip forming member 16 fixedly disposed so as not to rotate in a state where a predetermined tension is applied.

  For example, a heater such as a halogen lamp with an output of 700 W (hereinafter referred to as “heating-side heater”) 18 is built in the heating roller 14 formed of a metal cylinder, for example. The heating heater 18 is controlled to be turned on / off by the control unit 72. In addition, two thermistors (temperature detectors) 20a and 20b, which are first temperature detection means, are arranged in contact with the outer surface of the heating roller 14. The thermistor 20 a is in contact with the axial center of the heating roller 14, and the thermistor 20 b is in contact with one axial end of the heating roller 14. The detected temperatures by the thermistors 20a and 20b are input to the control unit 72, respectively.

  Note that the first temperature detection means for detecting the temperature of the heating roller 14 may be only one thermistor disposed in contact with the center or end of the heating roller 14. The thermistors 20a and 20b as the first temperature detection means directly detect the temperature of the heating roller 14, but constitute a means for indirectly detecting the temperature of the fixing belt 12 as the heating body. To do.

  The nip forming member 16 is formed of, for example, a heat resistant resin and extends so as to support the entire width of the fixing belt 12. A back-up member 22 made of, for example, a metal rod is disposed on the back surface of the nip forming member 16, and the back-up member 22 prevents the nip forming member 16 from being bent in a direction perpendicular to its longitudinal direction. .

  A pressure roller (pressure body) 24 is pressed against the portion of the fixing belt 12 supported by the nip forming member 16. The pressure roller 24 is rotationally driven in the direction of arrow A. The pressure roller 24 has a two-layer structure composed of, for example, a metal cylindrical cored bar 26 that forms an inner layer and an elastic layer 28 such as silicone rubber that forms an outer layer bonded to the outer peripheral surface of the cored bar 26. Have.

  The surface of the nip forming member 16 facing the pressure roller 24 is formed as a concave curved surface having a radius of curvature (for example, 15.4 mm) that is substantially the same as the radius (for example, 15 mm) of the pressure roller 24. Accordingly, a wide nip portion 30 having a length of, for example, 9 mm along the circumferential direction of the pressure roller 24 is formed between the fixing belt 12 and the pressure roller 24 that are in contact with each other.

  The pressure roller 24 has a built-in heater 42 such as a halogen lamp having an output of 300 W (hereinafter, referred to as “pressure side heater”). The pressure side heater 42 is controlled to be turned on / off by the control unit 72. Further, in the vicinity of the outer peripheral surface of the pressure roller 24, a thermistor 44 as a second temperature detecting means is disposed in close proximity to the pressure roller 24 in a non-contact manner. The temperature detected by the thermistor 44 is input to the controller 72.

  In the fixing device 10 configured as described above, a warm-up operation is performed as follows. The warm-up operation is performed when the main power source is turned on in the morning, when the main power source is turned on again, when the image forming apparatus body cover is closed after jamming or unit replacement, or when the sleep mode is restored.

  When the pressure roller 24 is driven to rotate in the direction of arrow A, the fixing belt 12 rotates in the direction of arrow B. At this time, the heating roller 14 rotates in the direction of arrow C according to the rotation of the fixing belt 12, but the fixing belt 12 slides along the surface of the nip forming member 16 because the nip forming member 16 is fixed so as not to rotate. Will do.

  The heating roller 14 is heated from the inside by a heating side heater 18. By controlling the heating side heater 18 on and off while monitoring the temperature with the thermistors 20a and 20b, the heating roller 14 is heated to a set temperature, for example, about 190 ° C. and held. By transferring heat from the heating roller 14 thus heated, the rotating fixing belt 12 is heated to, for example, about 170 ° C. over its entire circumference.

  The pressure roller 24 is also heated from the inside by the pressure side heater 42. At this time, the temperature of the pressure roller 24 to be raised is detected by the thermistor 44 and input to the controller 72. However, since the thermistor 44 is not in contact with the pressure roller 24, the temperature detected by the thermistor 44 is lower than the actual temperature of the pressure roller 24. Therefore, the control unit 72 uses the corrected temperature T ′ obtained by multiplying the detected temperature T of the thermistor 44 by the correction coefficient R as a basis for temperature control of the pressure roller 24. The pressure roller 24 is heated up to about 120 ° C. where the post-correction temperature T ′ is the set temperature and is held. When the heating roller 14 and the pressure roller 24 are each heated to a predetermined set temperature, the warm-up operation is completed.

  When the warm-up operation is completed, the control unit 72 sets a ready flag indicating that the fixing is possible. In this state, when there is a print command, the control unit 72 executes an image forming operation and a fixing operation. That is, in the fixing device 50, when the paper P carrying the toner image on the surface thereof is introduced from the lower side into the nip portion 30 and conveyed upward, the toner image in contact with the fixing belt 12 is heated and fixed on the paper. The

  On the other hand, when there is no print command with the ready flag set, the fixing device 50 enters a standby state. In this standby state, the pressure roller 24 and the fixing belt 12 are in a rotation stopped state, and the temperature is controlled so that the heating roller 14 and the pressure roller 24 are held at the respective set temperatures.

  As described above, the control unit 72 uses the corrected temperature T ′ obtained by multiplying the detected temperature T of the thermistor 44 by the correction coefficient R as the basis of the temperature control of the pressure roller 24. However, since the thermistor 44 is arranged in a non-contact manner with the pressure roller 24, the detected temperature T of the thermistor 44 is affected by the ambient temperature in the vicinity thereof, and therefore a constant correction coefficient is applied to the detected temperature of the thermistor 44. Even if they are multiplied, the accurate temperature of the pressure roller 24 cannot be obtained. Therefore, unless the accurate temperature of the pressure roller 24 is obtained, the temperature of the pressure roller 24 cannot be accurately controlled. Therefore, in the fixing device 50 of the present embodiment, the correction coefficient R is determined as follows.

The control unit 72 has a memory, and a table as shown in FIG. 3 is stored in the memory. In the table of FIG. 3, the central temperature T _A of the heating roller 14 detected by the thermistor 20a, the difference T _C between the central temperature T _A and the end temperature T _B of the heating roller 14 detected by the thermistor 20b, Based on the temperature T detected by the thermistor 44, the correction coefficient R is set to No. It is changed in 32 steps from 1 to 32 (however, since the correction coefficient R having the same value is included here, 32 types of correction coefficients R do not exist). The control unit 72 determines the correction coefficient R based on the T _A , T _C and T.

That is, the ambient temperature in the vicinity of the thermistor 44 is estimated from the warming condition of the fixing device 50 based on the T _A , T _C , and T, and the correction coefficient R is changed according to the estimated ambient temperature. In this way, the correction coefficient R is changed in accordance with the ambient temperature in the vicinity of the thermistor 44 arranged in a non-contact manner on the pressure roller 24, and the corrected temperature T ′ is obtained by multiplying the correction coefficient R by the detection temperature T of the thermistor 44. As a result, the temperature of the pressure roller 24 can be detected more accurately, whereby the accuracy of temperature control of the pressure roller 24 by the control unit 72 can be improved. As a result, the temperature variation of the pressure roller 24 is eliminated, and the stability of the fixed image is improved.

Here, the table shown in FIG. 3 is merely an example, and various changes can be considered in the method of determining the correction coefficient R by the control unit 72. For example, in the table of FIG. 3, T _A , T _C , and T are used as determination elements for determining the correction coefficient R, but only T _A and T _C may be used as determination elements. In this case, according to the example of FIG. 3, the correction coefficient R is divided into eight stages. Alternatively, only T _A (or T _B ) may be used as a determination factor for determining the correction coefficient R. In this case, according to the table of FIG. 3, the correction coefficient R is divided into four stages. Even when the correction coefficient R is determined in this way, the accuracy of temperature control of the pressure roller 24 by the control unit 72 can be improved as compared with the case where the correction coefficient R is always constant.

  The fixing device of the present invention is not limited to the above-described embodiment, and various modifications can be made.

  For example, as a heater for heating the heating roller 14 and the pressure roller 24, for example, an IH heater or a sheet heater can be used in addition to the halogen lamp. Further, the present invention is applicable even when the pressure roller 24 does not have a heater.

  In the fixing device 50, the nip forming member 16 that is fixedly disposed so as not to rotate is used as a member that supports the fixing belt 12 so as to face the pressure roller 24. Instead, a rotatable roller is used. In this case, the fixing belt 12 may be supported from the inside by three or more rollers.

  The present invention can also be applied to a roller pair type fixing device in which the heating roller 14 and the pressure roller 24 are in direct pressure contact. In this case, the heating roller 14 becomes a heating body.

  Further, the present invention can be applied to a fixing device using a pressure belt having a two-layer structure of an inner base material layer and an outer elastic layer as a pressure member, instead of the pressure roller 24.

  Furthermore, the image forming apparatus provided with the fixing device of the present invention may be a monochrome or full-color copying machine, a printer, a facsimile machine, or a complex machine thereof.

1 is a schematic configuration diagram of an image forming apparatus. The side view of a fixing device. The table | surface used in order that a control part determines a correction coefficient. FIG. 6 is a diagram illustrating an example of a conventional fixing device. FIG. 10 is a diagram illustrating another example of a conventional fixing device.

Explanation of symbols

12 ... Fusing belt (heating body)
14 ... Heating roller 16 ... Nip forming member 18 ... Heating side heaters 20a, 20b ... Thermistor (first temperature detecting means, temperature detector)
24 ... Pressure roller (Pressure body)
30 ... Nip part 42 ... Pressure side heater 44 ... Thermistor (second temperature detecting means)
50. Fixing device 72 ... Control unit 100 ... Image forming apparatus

Claims (7)

A rotatable heating body that heats and fixes a toner image, a rotatable pressure body that is pressed against the heating body and forms a nip portion with the heating body, and a first that detects the temperature of the heating body Temperature detection means, second temperature detection means arranged in close proximity to the pressure body to detect the temperature of the pressure body, temperature control of the heating body and the pressure body, respectively. A control method of a fixing device including a control unit,
The control unit determines a correction coefficient based on the temperature detected by the first temperature detection unit, multiplies the detection temperature of the second temperature detection unit by the correction coefficient, and obtains a corrected temperature of the pressurizing body, A method of controlling a fixing device, wherein the temperature of the pressure member is controlled based on the corrected temperature.   The first temperature detection means includes two temperature detectors brought into contact with the heating body, and the control unit determines at least one of the detection temperatures of the two temperature detectors in order to determine the correction coefficient. The fixing device control method according to claim 1, wherein the fixing device control method is used as a determination element.   3. The fixing device control method according to claim 1, wherein the control unit uses the temperature detected by the second temperature detection unit as a determination factor in order to determine the correction coefficient. 4. A rotatable heating body that heats and fixes a toner image, a rotatable pressure body that is pressed against the heating body and forms a nip portion with the heating body, and a first that detects the temperature of the heating body The temperature detection means, the second temperature detection means disposed in close proximity to the pressure body in order to detect the temperature of the pressure body, and the temperature of the heating body and the pressure body are adjusted. A fixing device including a control unit,
The control unit determines a correction coefficient based on the temperature detected by the first temperature detection unit, multiplies the detection temperature of the second temperature detection unit by the correction coefficient, and obtains a corrected temperature of the pressurizing body, A fixing device that controls the temperature of the pressure member based on the corrected temperature.   The first temperature detection means includes two temperature detectors brought into contact with the heating body, and the control unit determines at least one of the detection temperatures of the two temperature detectors in order to determine the correction coefficient. The fixing device according to claim 4, wherein the fixing device is used as a determination element.   The fixing device according to claim 4, wherein the control unit uses the detected temperature of the second temperature detecting unit as a determination factor in order to determine the correction coefficient. An image forming apparatus comprising the fixing device according to claim 4.

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