JP2007047126A - Temperature detector and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a noncontact type temperature detector capable of accurately detecting temperature of a non-detection member even if variation in environmental temperature is rapid. <P>SOLUTION: In determining surface temperature t1 of a heating roller 3a in a fixing region L1 based on two detection outputs from a noncontact type thermister 61, a control section 55 firstly refers to a temperature correction table Dt1 and determines a temperature correction amount Δtc corresponding to the temperature Tc of a temperature detecting section body 61a itself detected directly by a first thermister element 61-1. The control section 55 then refers to a surface temperature retrieval table Dt2, retrieves the detection output level of a second thermister element 61-2 corresponding to the corrected temperature Tcd, and retrieves and determines a surface temperature t1 of the heating roller 3a corresponding to the retrieved detection output level of the retrieved second thermister element 61-2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a temperature detection device that detects the temperature of a member to be detected using two temperature sensors, and an image forming apparatus including the same.

  In an electrophotographic image forming apparatus such as a copying machine, a facsimile machine, and a printer, an electrostatic latent image is formed on a photosensitive member, the electrostatic latent image is developed with toner, and a toner image is formed on the photosensitive member. The toner image is transferred from the photoreceptor to the recording paper, and the toner image on the recording paper is fixed by heating and pressing.

  In the fixing device for fixing the toner image, the recording paper is sandwiched between the heating roller and the pressure roller and heated and pressurized, whereby the toner image on the recording paper is heated and melted and fixed. In order to uniformly fix the toner image on the recording paper, the surface temperature of the heating roller must be uniform, and substantially the entire heating roller is uniformly heated while detecting the surface temperature of the heating roller. There is a need.

  As a temperature detector for detecting the surface temperature of the heating roller, for example, there is a thermistor, and this temperature detector is often brought into contact with the surface of the heating roller to detect the surface temperature of the heating roller.

  Further, in Patent Document 1, proportional control, integral control, and differential control are selectively performed on an adjustment circuit that adjusts the energization amount of the roller heater based on the roller surface temperature detected by the thermistor. Thus, the control accuracy of the roller surface temperature is improved.

  On the other hand, in the case of a monochrome image, since only black toner is used, the toner layer of the monochrome image on the recording paper is as thin as 20 to 30 μm. On the other hand, in the case of a color image, since a color image is formed by superimposing a plurality of color toners on a recording sheet, the toner layer of the color image on the recording sheet is as thick as 50 to 80 μm.

Therefore, in a monochrome image, for example, a nip area is formed between a metal heating roller coated with Teflon (registered trademark) or titanium and a pressure roller coated with SiO ₂ rubber, and recording is performed in this nip area. Even if the toner layer on the paper can be fixed, the toner layer of the color image cannot be sufficiently fixed in such a nip region.

  This is because the toner layer of the color image is thick, and in order to heat and melt the toner layer, it is necessary to transfer the heat of the heating roller to the toner layer of the color image more sufficiently than to heat and melt the toner layer of the monochrome image. This is because the heat of the heating roller cannot be sufficiently transferred to the toner layer in the nip region.

Therefore, in the color image fixing device, the surfaces of both the heating roller and the pressure roller are covered with SiO ₂ rubber, thereby increasing the width of the nip region. In the nip area where the width is increased, the area of the recording paper in contact with the heating roller is increased, so that the heat of the heating roller is sufficiently transmitted to the toner layer on the recording paper to surely heat and melt the toner layer. It can be sufficiently fixed.

However, in the color image forming apparatus, if the temperature detector is brought into contact with the surface of the heating roller in order to control the surface temperature of the heating roller, the surface of the heating roller is made of SiO ₂ rubber. The contact of the detector caused scratches on the surface of the heating roller, resulting in uneven fixing.

  In particular, in recent years, an increase in printing speed has been demanded for color image forming apparatuses, and since the rotation speed of the heating roller and pressure roller of the fixing device has been increased, the surface of the heating roller is brought into contact with the temperature detector. Many scratches are likely to occur, which causes a reduction in image quality.

For this reason, a non-contact type temperature detection device that can detect the temperature of the surface without contacting the surface of the heating roller may be employed.
Japanese Patent Laid-Open No. 11-161099

  By the way, in the non-contact type temperature detection device, the temperature detection unit including the first and second temperature sensors is arranged in the vicinity of the heating roller, and the respective temperatures detected by the first and second temperature sensors are set. Based on this, the surface temperature of the heating roller is detected.

  The second temperature sensor detects the surface temperature of the member to be detected in a non-contact manner. Since this non-contact temperature detection is affected by the environmental temperature, the temperature of the temperature detection unit itself is detected as the environmental temperature by the first temperature sensor, and is detected by the second temperature sensor based on the temperature of the temperature detection unit itself. The surface temperature of the non-detecting member is corrected. More specifically, a data table for deriving the surface temperature of the non-detection member from each detected temperature detected by the first and second temperature sensors is created in advance, and referring to this data table, The surface temperature of the non-detection member is derived from the detected temperatures of the first and second temperature sensors.

  However, such a non-contact type temperature detection device can detect the surface temperature of the non-detection member accurately in a situation where the environmental temperature is substantially constant or changes slowly, for example, an image forming apparatus, for example. In a situation where the environmental temperature changes abruptly as in the inside, a detection error of the surface temperature of the non-detection member is likely to occur. This is because even if the temperature of the temperature detection unit itself is detected by the first temperature sensor, the temperature of the temperature detection unit itself follows the environment temperature with a delay, and thus the temperature detection unit itself detected by the first temperature sensor. This is because there is a difference between the ambient temperature and the ambient temperature, and this difference is reflected as a detection error of the surface temperature of the non-detection member.

  In Patent Document 1, as described above, the surface temperature of the roller detected by the thermistor is not used as it is, but the energization amount to the roller heater is adjusted based on this surface temperature. The control accuracy is improved. However, since the thermistor is brought into contact with the surface of the roller here, such a technique cannot be applied to a non-contact type temperature detecting device.

  Therefore, the present invention has been made in view of the above-described conventional problems, and is a non-contact type temperature capable of accurately detecting the temperature of a non-detection member even when the environmental temperature changes rapidly. It is an object to provide a detection device and an image forming apparatus including the detection device.

  In order to solve the above problems, the temperature detection device of the present invention includes a first temperature sensor whose detection target is the temperature of the temperature detection unit itself and a second temperature sensor whose detection target is the surface temperature of the detected member. A temperature detection device that includes a temperature detection unit and detects the surface temperature of the detected member based on the detection output of the first temperature sensor and the detection output of the second temperature sensor, detected by the first temperature sensor. A temperature correction table for correcting the temperature, and a surface temperature search for searching for the surface temperature of the detected member corresponding to the temperature corrected using the temperature correction table and the temperature detected by the second temperature sensor And a surface temperature of the detected member is detected using the temperature correction table and the surface temperature search table.

  In the present invention, the temperature detector is provided in a non-contact manner on the member to be detected.

  Furthermore, in the present invention, the temperature correction table is set in advance according to the environment in which the member to be detected is installed.

  Further, in the present invention, the sign of the temperature correction amount according to the temperature correction table changes with a specified temperature as a boundary.

  On the other hand, an image forming apparatus according to the present invention includes the temperature detection device according to the present invention.

  In the present invention, the detected member whose surface temperature is detected by the temperature detecting device is a fixing roller for fixing the toner image on the recording paper.

  Furthermore, in the present invention, the sign of the temperature correction amount according to the temperature correction table changes with the toner softening temperature as a boundary.

  According to such a temperature detection apparatus of the present invention, the temperature of the temperature detection unit itself detected by the first temperature sensor is corrected using the temperature correction table. For this reason, in the situation where the environmental temperature changes rapidly, the temperature of the temperature detection unit itself detected by the first temperature sensor follows the environmental temperature with a delay, and between the temperature detected by the first temperature sensor and the environmental temperature. Even if there is a difference, the temperature correction table can be used to perform correction so that the detected temperature approximates the environmental temperature. And since the surface temperature of the detected member corresponding to the corrected temperature and the temperature detected by the second temperature sensor is derived by searching the surface temperature search table, the surface temperature of the detected member is accurately determined. Can be sought.

  Since the temperature detection unit of such a temperature detection device is provided in a non-contact manner on the member to be detected, the non-detection member is not damaged.

  The temperature correction table is set in advance according to the environment where the member to be detected is installed. That is, the degree of temperature delay of the temperature detection unit itself with respect to the environmental temperature changes according to the separation distance between the temperature detection unit and the detected member, the change rate of the environmental temperature, and the like. It is necessary to appropriately set the contents of the temperature correction table according to the change rate or the like. For example, the sign of the temperature correction amount according to the temperature correction table is changed with the specified temperature as a boundary.

  On the other hand, according to the image forming apparatus of the present invention, the temperature detecting apparatus of the present invention is provided. For example, the detected member whose surface temperature is detected by the temperature detecting device is a fixing roller for fixing a toner image on a recording sheet. As a result, the surface temperature of the fixing roller can be accurately detected in a non-contact manner, and scratches on the surface of the fixing roller due to contact with the sensor can be prevented.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a side view showing an image forming apparatus to which an embodiment of a fixing device of the present invention is applied. The image forming apparatus 100 is a color laser printer that records a color image on a recording sheet. The exposure apparatus 1, image forming stations Pa, Pb, Pc, and Pd, an intermediate transfer belt apparatus 2, a fixing apparatus 3, and a sheet conveying apparatus. 4 and a sheet feeder 5 and the like.

  The image forming stations Pa, Pb, Pc, and Pd respectively form black (K), cyan (C), magenta (M), and yellow (Y) toner images, and transfer the respective color toner images to the intermediate transfer belt device. 2 is transferred to the intermediate transfer belt 11. These image forming stations Pa, Pb, Pc, and Pd include developing devices 21a to 21d, photosensitive drums 23a to 23d, chargers 24a to 24d, and cleaner devices 25a to 25d.

  Each of the photosensitive drums 23a to 23d is pressed by the primary transfer rollers 26a to 26d via the intermediate transfer belt 11, and has the same peripheral speed as that of the intermediate transfer belt 11 that rotates and moves in the arrow direction B. It is rotated together with the transfer belt 11. The primary transfer rollers 26 a to 26 d also rotate following the intermediate transfer belt 11 at the same peripheral speed as the intermediate transfer belt 11 that rotates and moves in the arrow direction B.

  Each of the chargers 24a to 24d is of a roller type, a brush type, or a charger type that is in contact with the photosensitive drums 23a to 23d, and uniformly charges the surfaces of the photosensitive drums 23a to 23d.

  The exposure apparatus 1 includes a laser light source 1a that emits a laser beam to each photosensitive drum 23a to 23d, and a plurality of mirrors 1b that guide each laser beam to each photosensitive drum 23a to 23d. Each laser beam is irradiated on the surface of each of the photosensitive drums 23a to 23d while modulating each laser beam according to the image data, thereby forming each electrostatic latent image on the surface of each of the photosensitive drums 23a to 23d. .

  As the exposure apparatus 1, a write head in which light emitting elements such as EL and LED are arranged in an array may be used.

  Each of the developing devices 21a to 21d has a toner of each color, and attaches the toner of each color to the electrostatic latent image on the surface of each of the photoconductor drums 23a to 23d, so that each photoconductor drum 23a to 23d. A toner image of each color is formed on the surface. These toner images are transferred from the photosensitive drums 23a to 23d to the intermediate transfer belt 11 and superimposed.

  The intermediate transfer belt device 2 includes an intermediate transfer belt 11, primary transfer rollers 26 a to 26 d, a driving support roller 31, a driven support roller 32, a secondary transfer roller 33, and the like, and the intermediate transfer belt 11 is driven and supported. The primary transfer rollers 26 a to 26 d and the secondary transfer roller 33 are pressed against the intermediate transfer belt 11 while being supported by the roller 31 and the driven support roller 32 so as to be rotatable.

  The intermediate transfer belt 11 is formed of a synthetic resin film having a thickness of about 100 μm to 150 μm, for example. The secondary transfer roller 33 is supported so as to be movable left and right. When the secondary transfer roller 33 is moved rightward, the intermediate transfer belt 11 is sandwiched between the secondary transfer roller 33 and the drive support roller 31 to form a nip region. The drive support roller 31 functions as a backup roller for the secondary transfer roller 33, and rotates with the respective nip areas between the primary transfer rollers 26a to 26d and the photosensitive drums 23a to 23d downstream. When driven, the intermediate transfer belt 11 is pulled and rotated in the arrow direction B. Thereby, each nip area is stably maintained.

  In order to more stably form the nip areas between the primary transfer rollers 26a to 26d and the photosensitive drums 23a to 23d, the primary transfer rollers 26a to 26d and the photosensitive drums 23a to 23d are formed. Preferably, one of them is made of a hard material and the other is made of an elastic material.

  Each of the primary transfer rollers 26a to 26d is formed, for example, by coating the outer periphery of a metal shaft having a diameter of 8 mm to 10 mm with a conductive elastic material (EPDM, urethane foam, or the like). The primary transfer rollers 26a to 26d are opposite in polarity to the toner charging polarity in a state where the intermediate transfer belt 11 is sandwiched between nip regions between the primary transfer rollers 26a to 26d and the photosensitive drums 23a to 23d. Are applied to the toner on the surfaces of the photosensitive drums 23a to 23d via the intermediate transfer belt 11, and the toner on the surfaces of the photosensitive drums 23a to 23d is attracted to the intermediate transfer belt 11. To transcribe. As a result, the toner images of the respective colors are transferred to the intermediate transfer belt 11 and superimposed.

  In addition, as each primary transfer roller 26a-26d, you may use a brush etc. instead of a roller.

  The cleaning device 34 is, for example, a cleaning blade that is in sliding contact with the surface of the intermediate transfer belt 11 and removes toner remaining on the surface of the intermediate transfer belt 11 to prevent fogging of an image to be printed next time.

  The toner images of the respective colors transferred and superimposed on the intermediate transfer belt 11 in this way are conveyed to the nip area between the drive support roller 31 and the secondary transfer roller 33 as the intermediate transfer belt 11 rotates. Then, the leading edge of each color toner image on the intermediate transfer belt 11 and the leading edge of the recording paper conveyed by the registration roller 8 are aligned, and the toner image of each color is superimposed on the recording paper to record the toner image of each color. Transferred to paper.

  Subsequently, the recording paper is conveyed to the fixing device 3, where it is sandwiched between the heating roller 3a and the pressure roller 3b. As a result, the toner of each color on the recording paper is heated and melted and mixed, and the toner image of each color is fixed as a color image on the recording paper.

  Further, the recording paper is transported to the paper discharge tray 35 by the paper transport device 4 and discharged here face down.

  On the other hand, in the image forming apparatus 100, the recording paper is stacked and accommodated in the paper feed cassette 6. In the paper transport device 4, the recording paper in the paper feed cassette 6 is pulled out one by one by the pickup roller 7-1 and the recording paper is transported to the registration roller 8 by the transport roller 4-1.

  Alternatively, the recording paper is placed on the manual paper feed tray 9. In the paper feeding device 5, the recording paper in the manual paper feeding tray 9 is pulled out by the pickup roller 7-2, and the recording paper is conveyed to the registration roller 8 of the paper conveying device 4 by the respective conveying rollers 4-7 and 4-8. .

  In the paper transport device 4, the recording paper is temporarily stopped by the registration rollers 8, the leading edges of the recording paper are aligned, and the leading edge of the recording paper is the leading edge of the toner image formed on the intermediate transfer belt 11 of the intermediate transfer belt device 2. At the overlapping timing, the recording sheet is conveyed to the secondary transfer roller 33 by the registration roller 8.

  It is also possible to form a monochrome image using only the image forming station Pa and transfer the monochrome image to the intermediate transfer belt 11 of the intermediate transfer belt device 2. Similarly to the color image, this monochrome image is also transferred from the intermediate transfer belt 11 to the recording paper and fixed on the recording paper.

  When printing on both sides of the recording paper, not only the surface of the recording paper, the image on the surface of the recording paper is fixed by the fixing device 3 and then the recording paper is being conveyed by the conveying roller 4-3 of the paper conveying device 4. Then, the conveying roller 4-3 is stopped and then reversely rotated, the recording sheet is passed through the reversing path 4r of the sheet conveying apparatus 4, the recording sheet is reversed, and the recording sheet is guided to the registration roller 8 for recording. Similar to the front side of the paper, an image is recorded and fixed on the back side of the recording paper, and the recording paper is discharged to the paper discharge tray 35.

  Next, the fixing device 3 of this embodiment will be described in detail. FIG. 2 is a cross-sectional view showing the heating roller 3a and the pressure roller 3b of the fixing device 3 cut in the vertical direction, and FIG. 3 shows the heating roller 3a of the fixing device 3 cut in the horizontal direction. It is a longitudinal cross-sectional view.

  In the fixing device 3 of the present embodiment, the heating roller 3a and the pressure roller 3b are rotatably supported, the rollers 3a and 3b are pressed against each other, and the recording paper is sandwiched between the rollers 3a and 3b. A nip area N is formed, one of the heating roller 3a and the pressure roller 3b is rotationally driven, the other is driven to rotate, and the recording paper is introduced into the nip area N between the rollers 3a and 3b. The rollers 3a and 3b apply pressure and heat to the recording paper. Thereby, as described above, the toner of each color on the recording paper is heated and melted and mixed, and the toner image of each color is fixed on the recording paper as a color image.

  Further, the cleaning rollers 71 and 71 are pressed against the heating roller 3a and the pressure roller 3b to remove toner, paper dust, and the like adhering to the surfaces of the rollers 3a and 3b.

  Further, the paper separating claws 72 and 72 are pressed against the heating roller 3a and the pressure roller 3b, and the recording paper is peeled off from the surfaces of the rollers 3a and 3b. Prevents wrapping around.

The heating roller 3a is obtained by coating the peripheral surface of a metal cylinder 51 with an elastic layer 52 made of SiO ₂ rubber. Respective flanges 51a are provided on both edges of the cylindrical body 51, and an elastic layer 52 is disposed between the flanges 51a. In addition, a pipe-like shaft 51b is projected from the center of each flange 51a of the cylindrical body 51, and each pipe-like shaft 51b is rotatably supported. Further, a main heater 53 and a sub heater 54 are arranged inside the cylindrical body 51 along the longitudinal direction of the heating roller 3 a, and the heating roller 3 a is heated by the heat generated by the main heater 53 or the sub heater 54. Terminals 53a at both ends of the main heater 53 and terminals 54a at both ends of the sub-heater 54 are connected to the control unit 55 through each pipe-shaped shaft 51b.

  FIG. 4 is a graph showing the temperature distribution characteristic A of the heating roller 3 a heated by the main heater 53 and the temperature distribution characteristic B of the heating roller 3 a heated by the sub heater 54. The main heater 53 is disposed near the center of the heating roller 3a, and heats the heating roller 3a in the fixing region L1 near the center. When the heating roller 3a is heated only by the main heater 53, the surface temperature of the heating roller 3a uniformly increases in the fixing region L1 near the center, and the surface temperature of the heating roller 3a increases as the distance from the fixing region L1 increases. descend.

  The sub-heater 54 has two heater portions 54b and 54b. The heater portions 54b and 54b are distributed and arranged on both sides of the heating roller 3a, and the heating roller is used in the two fixing regions L2 on both sides. 3a is heated. In the heating state of the heating roller 3a by only the heater portions 54b and 54b, the surface temperature of the heating roller 3a uniformly increases in the two fixing regions L2 on both sides, and the more the heating roller 3a is separated from these fixing regions L2, The surface temperature decreases.

  Therefore, when only the main heater 53 generates heat, the temperature distribution characteristic A is obtained, and the surface temperature of the heating roller 3a becomes uniform only in the fixing region L1.

  Further, when the sub heater 54 is caused to generate heat, the main heater 53 is also necessarily caused to generate heat. Thereby, the surface temperature of the heating roller 3a becomes uniform in the entire fixing region L including the fixing region L1 and each fixing region L2. As shown in FIG. 3, the entire fixing region L is slightly wider than the heat generating region M where the main heater 53 and the sub heater are present when viewed from the peripheral surface side of the heating roller 3a.

  When fixing the toner of each color on the recording paper, the surface temperature of the heating roller 3a in the fixing region L1 or the surface temperature of the heating roller 3a in the entire fixing region L is maintained at the specified temperature T1. By maintaining the surface temperature of the heating roller 3a at the specified temperature T1, the toner of each color on the recording paper is appropriately heated and melted and fixed.

Similarly to the heating roller 3a, the pressure roller 3b is also formed by coating the peripheral surface of a metallic cylindrical body 56 with an elastic layer 57 made of SiO ₂ rubber. Similarly to the cylindrical body 51 of the heating roller 3a, the cylindrical body 56 has flanges (not shown) and pipe-like shafts (not shown) on both edges thereof, and each pipe-like shaft is freely rotatable. It is supported. A single heater 58 is disposed inside the cylindrical body 56 along the longitudinal direction of the pressure roller 3b, and the pressure roller 3b is heated by the heat generated by the heater 58. Terminals at both ends of the heater 58 are also connected to the control unit 55 through pipe-shaped shafts at both ends of the cylindrical body 56.

  The heater 58 heats substantially the entire pressure roller 3b, and uniformly increases the surface temperature of the pressure roller 3b in the entire fixing region L in FIG.

  When fixing the toner of each color on the recording paper, the surface temperature of the pressure roller 3b in the entire fixing region L is maintained at a specified temperature T1 similar to that of the heating roller 3a. By maintaining the surface temperature of the pressure roller 3b at the specified temperature T1, the recording paper is heated, and the toner fixability to the recording paper is improved.

  Next, a non-contact thermistor 61 is disposed at a position slightly spaced from the surface of the elastic layer 52 of the heating roller 3a in the vicinity of the approximate center of the heating roller 3a. A contact thermistor 62 is disposed in contact with the end of the elastic layer 53 of the heating roller 3a. As shown in FIG. 3, the end portion of the heating roller 3 a corresponds to a portion that does not overlap the main heater 53 and the sub heater when viewed from the peripheral surface side of the heating roller 3 a, that is, a portion outside the heat generation region M.

  As shown in FIG. 5, the non-contact type thermistor 61 has first and second thermistor elements 61-1 and 61-2 built in the temperature detection unit main body 61a. The surface temperature Tb of 3a is indirectly detected, and the temperature Tc of the temperature detection unit main body 61a itself is directly detected by the first thermistor element 61-1. The detection output of the second thermistor element 61-2 is output to the control unit 55 through the output detection unit 65. The detection output of the first thermistor element 61-1 is output to the control unit 55 through the output detection unit 64. The control unit 55 is based on two detection outputs from the non-contact thermistor 61, that is, the surface temperature Tb of the heating roller 3a detected indirectly and the temperature Tc of the temperature detection unit main body 61a itself detected directly. Then, the surface temperature t1 of the heating roller 3a in the fixing region L1 is accurately obtained.

  The contact type thermistor 62 directly detects the surface temperature of the end portion of the elastic layer 52 of the heating roller 3a. However, at the end portion of the elastic layer 52 of the heating roller 3a, the surface temperature t3 at the end portion is lower than the surface temperature t2 in the fixing region L2, as is apparent from the temperature distribution characteristic B of FIG. Therefore, the control unit 55 corrects the surface temperature t3 at the end indicated by the detection output of the contact type thermistor 62, and obtains the surface temperature t2 in the fixing region L2.

  For example, the main heater 53 and the sub heater 54 of the heating roller 3a are caused to generate heat so that the surface temperature of the heating roller 3a is gradually increased from the normal temperature, and the surface temperature t3 of the end portion of the heating roller 3a and the surface temperature t2 in the fixing region L2. And the ratio α between the surface temperature t3 of the end portion and the surface temperature t2 in the fixing region L2 is obtained each time the surface temperature t3 of the end portion of the heating roller 3a changes stepwise. Then, a data table Dt0 in which the end surface temperature t3 and the ratio α are associated with each other as shown in FIG. 6 is created in advance, and this data table Dt0 is stored in the control unit 55.

  When the main heater 53 and the sub-heater 54 generate heat, the control unit 55 searches the data table Dt0 for a ratio α corresponding to the surface temperature t3 of the end indicated by the detection output of the contact type thermistor 62, and this ratio α is determined as the surface temperature. The surface temperature t2 in the fixing region L2 is obtained by multiplying by t3.

  Here, the decrease in the surface temperature at the end of the heating roller 3a occurs due to direct heat dissipation from the heating roller 3a, heat dissipation due to heat conduction from the heating roller 3a to peripheral members, or the like. Since the amount of heat radiation is substantially specified, the surface temperature t2 in the fixing region L2 can be obtained based on the surface temperature t3 of the end portion of the heating roller 3a and the ratio α using the data table Dt0 as described above. .

  Thus, in the fixing region L1, the non-contact type thermistor 61 is arranged slightly spaced from the surface of the elastic layer 52 of the heating roller 3a, so that the surface of the elastic layer 52 is not damaged. Further, since the contact type thermistor 62 is disposed in contact with the end of the elastic layer 53 of the heating roller 3a that is out of the entire fixing region L, this end contributes to fixing of the toner on the recording paper. Even if the contact-type thermistor 62 comes into contact with the end portion, the end portion does not cause uneven fixing of the recording paper.

  Further, since only one large non-contact thermistor 61 is used and the small contact thermistor 62 is used in combination, the fixing device 3 and the image forming apparatus 100 need not be enlarged.

  On the other hand, a contact thermistor 63 is disposed in the vicinity of the center of the elastic layer 57 of the pressure roller 3b. The contact thermistor 63 directly detects the surface temperature near the center of the elastic layer 57. Further, the heater 58 of the pressure roller 3b uniformly increases the surface temperature of the pressure roller 3b in the entire fixing region L as described above. Therefore, the control unit 55 can obtain the surface temperature of the pressure roller 3 b indicated by the detection output of the contact type thermistor 63 as the surface temperature in the entire fixing region L.

  Even if the elastic layer 57 of the pressure roller 3b is damaged by the contact of the contact type thermistor 63, the pressure roller 3b only heats the recording paper itself, and directly heats the toner on the recording paper. Therefore, scratches on the elastic layer 57 of the heating roller 3b do not cause uneven fixing of the recording paper.

  In the fixing device 3 having such a configuration, when the image forming apparatus 100 is in the standby mode or the energy saving mode, the surface temperature of the heating roller 3a and the surface temperature of the pressure roller 3b are suppressed to a specified temperature T1 or less.

  That is, the control unit 55 obtains the surface temperature t1 of the heating roller 3a in the fixing region L1 from the detection output of the non-contact type thermistor 61, and the heating roller 3a so that the surface temperature t1 becomes a constant temperature equal to or lower than the specified temperature T1. The surface temperature t2 of the heating roller 3a in the fixing region L2 is obtained from the detection output of the contact type thermistor 62, and the surface temperature t2 becomes a constant temperature equal to or lower than the specified temperature T1. Similarly, the energization to the sub-heater 54 of the heating roller 3a is controlled on and off. Similarly, the control unit 55 performs on / off control of energization of the heater 58 of the pressure roller 3b so that the surface temperature of the pressure roller 3b detected by the contact type thermistor 63 becomes a constant temperature equal to or lower than the specified temperature T1. Thereby, in the standby mode or the energy saving mode, the power consumption of the fixing device 3 is reduced while the surface temperature of the heating roller 3a and the surface temperature of the pressure roller 3b are maintained at a constant temperature in the entire fixing region L.

  Next, when a print request is generated, the control unit 55 performs on / off control of energization to the heater 58 of the pressure roller 3b according to the surface temperature of the pressure roller 3b detected by the contact type thermistor 63, and the pressure roller The surface temperature of 3b is raised to the specified temperature T1.

  Whether the control unit 55 inputs the width of the recording sheet from the outside, and performs the energization control of the main heater 53 and the sub heater 54 of the heating roller 3a based only on the detection output of the non-contact type thermistor 61 according to the width. Alternatively, it is determined whether to perform energization control of the main heater 53 and the sub heater 54 of the heating roller 3a based on the detection output of the non-contact type thermistor 61 and the detection output of the contact type thermistor 62.

  For example, when the recording sheet is the standard size B4 and the recording sheet passes through the entire fixing region L slightly narrower than the entire width of the heating roller 3a, it is determined that the energization control is performed based only on the detection output of the non-contact type thermistor 61. When the recording sheet is the standard size A4 and the recording sheet passes through the fixing region L1 having a narrow width, it is determined that the energization control is performed based on the detection output of the non-contact type thermistor 61 and the detection output of the contact type thermistor 62. .

  If the control unit 55 determines that the recording sheet is the standard size B4 and the energization control is performed only based on the detection output of the non-contact thermistor 61, the control unit 55 determines that the recording paper in the fixing region L1 is based on the detection output of the non-contact thermistor 61. The surface temperature t1 of the heating roller 3a is obtained, and the energization to the main heater 53 and the sub heater 54 of the heating roller 3a is both turned on / off so that the surface temperature t1 becomes the specified temperature T1.

  That is, when the recording paper is the standard size B4 and the recording paper passes through the entire fixing region L, the main heater 53 and the sub heater 54 are based on the surface temperature t1 in the fixing region L1 indicated by the detection output of the non-contact type thermistor 61. The surface temperature t1 in the fixing region L1 is controlled to the specified temperature T1. As a result, even in the entire fixing region L, the surface temperature t1 of the heating roller 3a becomes the specified temperature T1.

  Further, if the control unit 55 determines that the recording paper is the standard size A4 and the energization control is performed based on the detection output of the non-contact type thermistor 61 and the detection output of the contact type thermistor 62, the control unit 55 of the non-contact type thermistor 61 The surface temperature t1 of the heating roller 3a in the fixing region L1 is obtained from the detection output, and the energization to the main heater 53 is on / off controlled so that the surface temperature t1 becomes the specified temperature T1, and from the detection output of the contact type thermistor 62. The surface temperature t2 of the heating roller 3a in the fixing region L2 is obtained, and the energization to the sub-heater 54 of the heating roller 3a is on / off controlled so that the surface temperature t2 becomes the specified temperature T1.

  That is, when the recording sheet is the standard size A and the recording sheet passes through the narrow fixing region L1, the energization control to the main heater 53 of the heating roller 3a is performed based on the detection output of the non-contact type thermistor 61. Based on the detection output of the contact type thermistor 62, energization control to the sub heater 54 of the heating roller 3a is performed. Thereby, at least the surface temperature t1 of the heating roller 3a in the fixing region L1 is controlled to the specified temperature T1.

  FIG. 7 is a graph showing the surface temperature distribution of the heating roller 3a when the recording paper passes through the nip region N between the heating roller 3a and the pressure roller 3b. When the recording paper passes through the entire fixing area L, the surface temperature t1 is maintained at the specified temperature T1 at any location in the entire fixing area L as indicated by the solid line C. However, in the entire fixing region L, the heat amount of the heating roller 3a is deprived by the recording paper and the toner on the recording paper, whereas the heat amount of the heating roller 3a is not deprived on both sides of the entire fixing region L. As a result of continuous energization of the main heater 53 and the sub heater 54, the heating roller 3a is overheated, and the surface temperature t1 is higher than the specified temperature T1.

  Further, when the recording paper passes through the narrow fixing region L1, the surface temperature t1 in the fixing region L1 is substantially maintained at the specified temperature T1. Further, since energization control to the sub-heater 54 is performed based on the detection output of the contact type thermistor 62, the surface temperature t2 in the fixing region L2 is substantially maintained at the specified temperature T1. Even if the recording paper passes through the fixing region L1 having a narrow width, if the energization control to the main heater 53 and the sub heater 54 of the heating roller 3a is performed based only on the detection output of the non-contact thermistor 61, FIG. 7, even if the surface temperature t1 in the fixing region L1 can be maintained at the specified temperature T1, the heat amount of the heating roller 3a is not deprived by the recording paper or toner in the fixing region L2. 53 and the sub-heater 54 are continuously energized, the heating roller 3a becomes overheated, and the surface temperature t2 becomes much higher than the specified temperature T1.

  By the way, as shown in FIG. 5, the non-contact type thermistor 61 has first and second thermistor elements 61-1 and 61-2 built in the temperature detection unit main body 61a, and indirectly by the second thermistor element 61-2. The detected surface temperature Tb of the heating roller 3a and the temperature Tc of the temperature detection unit main body 61a detected directly by the first thermistor element 61-1 are output to the control unit 55. And the control part 55 is based on two detection outputs from the non-contact type thermistor 61, ie, the surface temperature Tb of the heating roller 3a detected indirectly and the temperature Tc of the temperature detection part main body 61a itself detected directly. Based on this, the surface temperature t1 of the heating roller 3a in the fixing region L1 is accurately obtained.

  Here, the controller 55 stores a temperature correction table Dt1 as shown in FIG. 8 and a surface temperature search table Dt2 as shown in FIG. 9 in order to accurately obtain the surface temperature t1 of the heating roller 3a in the fixing region L1. And hold it. In these tables Dt1 and Dt2, since the minimum width of temperature change is actually set to about 0.1 ° C., the data amount is enormous, but the data amount is reduced and described. In order to simplify the above, the minimum width of the temperature change is set to about 10 ° C.

  The temperature correction table Dt1 in FIG. 8 is used to correct the temperature Tc of the temperature detection unit main body 61a itself directly detected by the first thermistor element 61-1, and to accurately determine the environmental temperature of the fixing device 3. . Here, the content of the temperature correction table Dt1 is shown in a graph, but it is actually similar to a numerical table.

  In this temperature correction table Dt1, the temperature Tc of the temperature detection unit main body 61a itself directly detected by the first thermistor element 61-1 and the temperature correction amount Δtc are stored in association with each other. The range of the temperature Tc of the temperature detection unit main body 61a itself is set to 0 to 120 ° C. in consideration of the installation environment (such as the room) of the image forming apparatus 100 and the temperature rise limit inside the image forming apparatus 100. A temperature correction amount Δtc corresponding to the range of temperature Tc is experimentally obtained and set.

  Further, as is apparent from the temperature correction table Dt1 of FIG. 8, the temperature correction amount Δtc becomes 0 when the temperature Tc of the temperature detection unit main body 61a detected directly by the first thermistor element 61-1 is around 60 ° C. Yes. For this reason, when the temperature Tc of the temperature detection part main body 61a detected directly is around 60 ° C., it can be said that the temperature Tc substantially matches the environmental temperature. When the temperature Tc is lower than 60 ° C., the temperature correction amount Δtc is negative, and when the temperature Tc is higher than 60 ° C., the temperature correction amount Δtc is positive.

  This temperature Tc 60 ° C. is substantially equal to the softening temperature of the toner. Therefore, it can be said that the first thermistor element 61-1 is disposed at a position where the environmental temperature corresponding to the softening temperature of the toner can be detected most accurately.

  Here, since the environmental temperature changes abruptly inside the image forming apparatus 100, the temperature Tc of the temperature detection unit main body 61 a itself cannot follow the environmental temperature, and is between the temperature Tc of the temperature detection unit main body 61 a itself and the environmental temperature. And the difference is reflected as a detection error of the surface temperature t1 of the heating roller 3a.

  For example, in the fixing device 3 of the image forming apparatus 100, the environmental temperature is equal to room temperature immediately before the start, and heating of the heating roller 3a and the pressure roller 3b is started after the start. When the temperature of 3b is raised to a certain temperature to enter the standby mode or the energy saving mode, and when further printing is requested, the heating roller 3a and the pressure roller 3b are further heated, and the temperature of each of the rollers 3a and 3b is a certain temperature. The temperature is raised to the above specified temperature. In printing, air flows due to rotation of the rollers 3a and 3b, etc., or heat is absorbed by the recording paper and the like, and the temperature fluctuations and unevenness of the rollers 3a and 3b are likely to occur. Further, after printing, the temperature of the heating roller 3a and the pressure roller 3b is lowered again from the specified temperature to a constant temperature. Since the temperature Tc of the temperature detection unit main body 61a itself follows the temperature change in the fixing device 3 with a delay, a difference occurs between the temperature Tc of the temperature detection unit main body 61a itself and the environmental temperature. The difference is reflected as a detection error of the surface temperature t1 of the heating roller 3a.

  For this reason, it is necessary to perform correction so that the temperature Tc of the temperature detection unit main body 61a itself approximates the environmental temperature.

  Specifically, a temperature correction amount Δtc corresponding to the detected temperature Tc of the temperature detection unit main body 61a itself is obtained with reference to the temperature correction table Dt1. When the image forming apparatus 100 is in the standby mode or the energy saving mode, or when the rotation of the rollers 3a and 3b of the fixing device 3 is decelerated, the temperature detection unit main body 61a itself that has detected the temperature correction amount Δtc. The corrected temperature Tcd is obtained by adding to the temperature Tc. When the image forming apparatus 100 is printing and the rollers 3a and 3b of the fixing device 3 are rotating or the rotation of the rollers 3a and 3b is accelerated, an air flow is generated. Since the difference between the temperature Tc of the temperature detection unit main body 61a itself and the environmental temperature further changes due to the air flow, + 2 ° C. is added to the temperature correction amount Δtc, and this sum is detected. The corrected temperature Tcd is obtained by adding to the temperature Tc of the main part 61a itself.

  Actually, as the temperature correction table Dt1, a table in which the detection output level of the first thermistor element 61-1 corresponding to the temperature Tc of the temperature detection unit main body 61a itself is associated with the correction amount of the detection output level is used. It is done. Further, instead of adding + 2 ° C. to the temperature correction amount Δtc, the correction amount of the detected output level is increased or decreased by a level corresponding to + 2 ° C. Then, the correction amount is added to the detection output level, and the corrected detection output level is obtained.

  The surface temperature search table Dt2 in FIG. 9 is used to obtain the surface temperature t1 of the heating roller 3a based on the corrected detection output level of the first thermistor element 61-1 and the detection output level of the second thermistor element 61-2. Is.

  In the surface temperature search table Dt2, a plurality of detection output levels of the second thermistor element 61-2 are stored in association with the temperature Tcd corrected based on the temperature correction table Dt1 of FIG. The surface temperature t1 of the heating roller 3a is stored in association with each detected output level of -2. For example, each detection output level 3.8629-3 of the second thermistor element 61-2 is associated with the corrected temperature Tcd = 60 ° C. (corrected detection output level 3.8629V of the first thermistor element 61-1). 3907V is stored, and the surface temperature t1 = 60 to 250 ° C. of the heating roller 3a is stored in association with the detection output levels 3.8629 to 3.3907V of the second thermistor element 61-2. Further, each detected output level 2.9437-2 of the second thermistor element 61-2 is associated with the corrected temperature Tcd = 90 ° C. (corrected detected output level 2.9623V of the first thermistor element 61-1). 5321V is stored, and the surface temperature t1 = 100 to 250 ° C. of the heating roller 3a is stored in association with the detected output levels 2.9437 to 2.5321V of the second thermistor element 61-2.

  According to the surface temperature search table Dt2, for example, the corrected temperature Tcd = 60 ° C. (corrected detection output level 3.8629 V of the first thermistor element 61-1), and the second thermistor element 61-2 When the detected output level is 3.7027V, the surface temperature t1 of the heating roller 3a is 150 ° C. Further, the corrected temperature Tcd = 90 ° C. (corrected detection output level of the first thermistor element 61-1 2.9623V) and the detection output level of the second thermistor element 61-2 is 2.8350V. Sometimes, the surface temperature t1 of the heating roller 3a is 150 ° C.

  As apparent from the surface temperature search table Dt2, the surface temperature t1 of the heating roller 3a is not specified even if only the detection output level of the second thermistor element 61-2 is specified. If the corrected detection output level of the first thermistor element 61-1 and the detection output level of the second thermistor element 61-2 are not specified, the surface temperature t1 is not specified.

  This is because the surface temperature Tb of the heating roller 3a is detected by the second thermistor element 61-2 in a non-contact manner, and the detection output by the second thermistor element 61-2 is affected by the environmental temperature. It is. For this reason, the first thermistor element 61-1 detects the temperature Tc of the temperature detection unit main body 61a itself, obtains a corrected temperature Tcd (approximate to the environmental temperature) based on the temperature correction table Dt1 of FIG. Based on the detected temperature Tcd and the surface temperature Tb of the heating roller 3a detected by the second thermistor element 61-2, the surface temperature t1 of the heating roller 3a is accurately obtained.

  Therefore, when the controller 55 obtains the surface temperature t1 of the heating roller 3a in the fixing region L1 based on the two detection outputs from the non-contact thermistor 61, first, referring to the temperature correction table Dt1 in FIG. A temperature correction amount Δtc corresponding to the temperature Tc of the temperature detection unit main body 61a detected directly by the first thermistor element 61-1 is obtained. When the image forming apparatus 100 is in the standby mode or the energy saving mode, or when the rotation of the rollers 3a and 3b of the fixing device 3 is decelerated, the temperature detection unit main body 61a itself that has detected the temperature correction amount Δtc. The corrected temperature Tcd is obtained by adding to the temperature Tc. When the image forming apparatus 100 is printing and the rollers 3a and 3b of the fixing device 3 are rotating or the rotation of the rollers 3a and 3b is accelerated, the temperature correction amount Δtc is + 2 ° C. And the sum is added to the detected temperature Tc of the temperature detection unit main body 61a itself to obtain a corrected temperature Tcd. Thereafter, the control unit 55 refers to the surface temperature search table Dt2 in FIG. 9 to search the detection output level of the second thermistor element 61-2 corresponding to the corrected temperature Tcd, and further search the second thermistor. The surface temperature t1 of the heating roller 3a corresponding to the detected output level of the element 61-2 is retrieved and obtained. Thereby, the surface temperature t1 of the heating roller 3a can be accurately obtained.

  As described above, in this embodiment, even if there is a difference between the temperature Tc of the temperature detection unit main body 61a detected directly by the first thermistor element 61-1 and the environmental temperature, the temperature correction table Dt1 is used. Then, the temperature Tc of the temperature detection unit main body 61a itself directly detected is corrected, and then detected by the corrected temperature Tcd and the second thermistor element 61-2 with reference to the surface temperature search table Dt2. Since the surface temperature t1 of the heating roller 3a corresponding to the temperature Tb is retrieved and obtained, the surface temperature t1 of the heating roller 3a can be obtained accurately.

  In addition, this invention is not limited to the said embodiment, It can deform | transform variously. For example, the temperature correction table Dt1 in FIG. 8 should be set according to the distance between the first thermistor element 61-1 and the non-detection member, the rate of change in the environmental temperature, and the like (value and positive / negative). Is not specified. Also, the surface temperature search table Dt2 in FIG. 9 should be set according to the characteristics of the non-contact type thermistor, and its contents (value and positive / negative) are not specified.

  In addition, the temperature detection device of the present invention is not limited to an image forming apparatus, and may be applied to any non-contact type sensor as long as it is a non-contact type sensor installed in a situation where the environmental temperature varies. Is possible.

1 is a side view showing an image forming apparatus to which an embodiment of a fixing device of the present invention is applied. FIG. 3 is a transverse cross-sectional view showing the heating roller and the pressure roller of the fixing device of the present embodiment broken in the vertical direction. FIG. 3 is a longitudinal sectional view showing the heating roller of the fixing device in FIG. 2 broken in the horizontal direction. It is a graph which shows the temperature distribution characteristic A of the heating roller heated by the main heater, and the temperature distribution characteristic B of the heating roller heated by the sub heater. FIG. 3 is a diagram conceptually illustrating a non-contact thermistor that detects a surface temperature of a heating roller of the fixing device in FIG. 2. It is a figure which shows notionally the data table which matched the surface temperature and ratio of the edge part of a heating roller. It is a graph which shows the surface temperature distribution of a heating roller when a recording paper passes through the nip area between a heating roller and a pressure roller. 3 is a graph conceptually showing the contents of a temperature correction table used to detect the surface temperature of the heating roller of the fixing device of FIG. 2. FIG. 3 is a chart conceptually showing a surface temperature search table used for detecting the surface temperature of the heating roller of the fixing device of FIG. 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Exposure apparatus 2 Intermediate transfer belt apparatus 3 Fixing apparatus 3a Heating roller 3b Pressure roller 4 Paper conveying apparatus 5 Paper feeding apparatus 6 Paper feeding cassette 7-1, 7-2 Pickup roller 8 Registration roller 9 Manual paper feed tray 11 Intermediate transfer Belts 21, 21a to 21d Developing devices 23, 23a to 23d Photoconductor drums 24a to 24d Chargers 25a to 25d Cleaners 51 and 56 Cylindrical bodies 52 and 57 Elastic layer 53 Main heater 54 Sub heater 55 Control unit 58 Heater 61 Non-contact type Thermistors 62 and 63 Contact type thermistor 71 Cleaning roller 72 Paper separation claw Dt1 Temperature correction table Dt2 Surface temperature search table

Claims (7)

A temperature detection unit including a first temperature sensor whose detection target is the temperature of the temperature detection unit itself and a second temperature sensor whose detection target is the surface temperature of the member to be detected; a detection output of the first temperature sensor; and In the temperature detection device that detects the surface temperature of the detected member based on the detection output of the second temperature sensor,
A temperature correction table for correcting the temperature detected by the first temperature sensor;
A surface temperature search table for searching for a surface temperature of the detected member corresponding to a temperature corrected using the temperature correction table and a temperature detected by a second temperature sensor;
A temperature detection apparatus for detecting a surface temperature of the detected member using the temperature correction table and the surface temperature search table. The temperature detection device according to claim 1, wherein the temperature detection unit is provided in a non-contact manner on the member to be detected. The temperature detection apparatus according to claim 1, wherein the temperature correction table is set in advance according to an environment in which the member to be detected is installed. The temperature detection apparatus according to claim 1, wherein the sign of the temperature correction amount based on the temperature correction table changes with a specified temperature as a boundary. An image forming apparatus comprising the temperature detection device according to claim 1. 6. The image forming apparatus according to claim 5, wherein the detected member whose surface temperature is detected by the temperature detecting device is a fixing roller for fixing the toner image on the recording paper. The image forming apparatus according to claim 5, wherein the sign of the temperature correction amount according to the temperature correction table changes with a softening temperature of the toner as a boundary.

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