JP5800186B2 - Fixing device and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device and an image forming apparatus, and more particularly to a fixing device using a fixing belt and an image forming apparatus including the fixing device.

  An electrophotographic image forming apparatus heats and fixes a toner image (unfixed image) transferred and carried on a sheet-like recording medium such as paper (hereinafter referred to as paper) to a copy or record. Output things. As such an image forming apparatus, a copying machine, a facsimile machine, a printer, and a digital multifunction machine having these functions are known.

  Known fixing devices include two rollers, that is, a fixing roller and a pressure roller pressed against the fixing roller, as well as a roller and an annular fixing belt pressed against the roller. In a fixing device including a fixing belt, a fixing belt that is wound around a plurality of rollers is arranged on a side that is in contact with a fixed image, and a pressure roller that presses a sheet is opposed to one of the rollers around which the fixing belt is wound. Deploy.

  A roller facing the pressure roller among the rollers around which the fixing belt is wound is used as a fixing roller, and a roller other than the fixing roller is provided with a heat source for heating the belt and is used as a heating roller. The fixing device including the fixing belt has an advantage that since the heat capacity of the fixing belt is small, the warm-up time can be shortened and the energy consumption can be reduced.

  Such a fixing device has a structure in which the fixing belt is locally heated in a region of about a half circumference of the heating roller. In the fixing device having such a configuration, it is necessary to keep the fixing belt rotating during heating. If the fixing belt is continuously heated while the fixing belt is not rotating, the fixing belt is locally heated, and the temperature of the portion is abnormally increased, resulting in smoke generation and belt melting. Because.

  For this reason, it is necessary to always detect the rotational running state of the fixing belt. Conventionally, instead of directly detecting the rotational running state of the fixing belt, the rotation of the fixing roller and other rollers around the fixing belt may be detected.

  However, the fixing belt and the roller around which it is slipped may slip, and in this case, even if the roller rotates, the fixing belt is not running. In this state, since the roller is detected as rotating, it is erroneously detected that the fixing belt is running despite being stopped.

  Therefore, a technique has been proposed in which at least one detection hole is provided in the belt and the detection hole is detected by a transmission type optical sensor (for example, Patent Document 1).

  Also known is a reflection type sensor instead of a transmission type sensor, where a reflection part for detection is provided on the fixing belt, and the rotation of the fixing belt is detected by detecting the reflection of light from the reflection part. ing.

  However, in the detection using the light described above, the light detection sensor must be disposed in the vicinity of the heating element, and it is difficult to satisfy the use temperature condition of the sensor.

  Further, as in the technique disclosed in Patent Document 1, if a detection hole is formed in the fixing belt, there is a problem that the strength of the fixing belt is reduced. The decrease in strength is not preferable in consideration of the tension caused by the fixing belt being wound around the roller and the pressure applied by being sandwiched between the pressure roller and the like, and improvement of this point is also desired. It was rare.

  Further, the following has been proposed as a method for detecting the rotational running state of the fixing belt without providing a detection hole in the belt (see Patent Document 2). In this state, the fixing roller is heated in a stopped state, temperature fluctuation (temperature ripple) of the partially heated fixing belt is detected, and rotation of the fixing belt is detected based on the temperature fluctuation state. . However, in this technique, the fixing belt must be heated once in a stopped state, and the control becomes complicated. Further, if the fixing is performed while the temperature fluctuation remains on the fixing belt, there is a problem that the image on the paper is affected. Furthermore, once the fixing belt starts to rotate, the temperature fluctuation is eliminated, and thereafter the running state of the fixing belt cannot be detected.

  The present invention has been made in view of such conventional problems, and does not use a sensor that is affected by heat, and does not perform processing that adversely affects the fixing belt, and detects rotation of the fixing belt. An object of the present invention is to provide a fixing device and an image forming apparatus that can be used.

The fixing device according to the present invention includes an annular fixing belt, a plurality of rollers that rotatably support the fixing belt, a heating unit that heats the fixing belt, and a sheet pressing medium that presses the sheet-like recording medium against the fixing belt. And a pressure roller, wherein one of the plurality of rollers is a heating roller including the heating unit, and the sheet-like recording medium of the peripheral surface of the heating roller that contacts the fixing belt. Is provided in a region that does not come in contact so as to be recessed from the peripheral surface toward the center of the heating roller. comprising a temperature detecting means for detecting a temperature of a portion, corresponding to the site where the heating roller, the concave portion of the fixing belt is provided Ryo The temperature variation in between said recess corresponds to the portion not provided region of the fixing belt, you detected by said temperature detecting means, characterized in that.

  According to the present invention, it is possible to detect the rotational running state of the fixing belt without using a sensor that is affected by heat or performing a process that affects the fixing belt.

1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to a first embodiment. 2 is a cross-sectional view illustrating a configuration of a fixing device of the image forming apparatus. FIG. FIG. 2 also shows the configuration of the heating roller of the fixing device, where (a) is a plan view and (b) is a cross-sectional view corresponding to the line BB in (a). FIG. 3 is a block diagram showing a control system of the fixing device in the same manner.

  Next, a fixing device according to an embodiment for carrying out the present invention (hereinafter simply referred to as an embodiment) and an image forming apparatus provided with the fixing device value will be described.

<Embodiment 1>
The image forming apparatus according to Embodiment 1 will be described below. FIG. 1 is a cross-sectional view illustrating a schematic configuration of the image forming apparatus according to the first embodiment. The image forming apparatus 100 is a color printer that forms an image on a sheet using toner of each color of yellow (Y), magenta (M), cyan (C), and black (K). The image forming apparatus 100 includes, as the image forming unit 110, image forming apparatuses 110Y (yellow), 110C (cyan), 110M (magenta), and 110K (black) for four colors. The image forming apparatus 100 includes an exposure device 120, a secondary transfer device 130, a paper supply device 140, a paper transport device 150, a toner supply device 160, and the fixing device 200 according to the first embodiment.

  The structures of the image forming devices 110Y, 110C, 110M, and 110K are the same. The image forming devices 110Y, 110C, 110M, and 110K each include a photosensitive drum 112 that is an image carrier. Further, the image forming devices 110Y, 110C, 110M, and 110K are a charging device 113 that charges the photosensitive drum 112, a cleaning device 114 that removes developer remaining on the photosensitive drum 112, and a latent image on the photosensitive drum 112. A developing device 115 for developing with toner is provided.

  The exposure device 120 includes a laser device 121 that is a light source, a mirror 122 that guides the laser light to the photosensitive drum 112, and the like. The exposure device 120 modulates and scans the laser beam based on the input image signal and exposes the photosensitive drum 112 of each of the image forming devices 110Y, 110C, 110M, and 110K to form a latent image.

  The secondary transfer device 130 includes a transfer belt 131 that is an intermediate transfer member, and suspension rollers 132, 133, and 134 that support the transfer belt 131 so as to be able to rotate. The secondary transfer device 130 also transfers the toner image formed on each photoconductive drum 112 to the transfer belt 131, and further transfers the toner image transferred onto the transfer belt 131 to a sheet. A secondary transfer roller 136 is provided.

  The paper supply device 140 includes paper cassettes 141 and 142 that store the paper bundle St, a pickup roller 143 that conveys the uppermost paper from the paper bundle disposed in the paper cassettes 141 and 142 to the secondary transfer device 130, and a conveyance. A roller pair 144 and the like are provided.

  The paper transport device 150 transports the paper from the paper supply device 140 to the outside of the apparatus through the secondary transfer device 130 and the fixing device 200. Further, when printing on both sides of the paper, the paper transport device 150 reverses the paper on which fixing has been completed and transports the paper again to the secondary transfer device 130. The paper transport device 150 includes a paper transport path 151 and a plurality of transport roller pairs 152 disposed across the paper transport path 151.

  In addition, the paper transport device 150 includes a belt transport device 153 that transports the paper on which the secondary transfer has been completed to the fixing device 200. The belt conveyance device 153 includes an annular conveyance belt 154, a driving roller 155 and a driven roller 156 that are wound around the conveyance belt 154.

  The toner replenishing device 160 replenishes the developing device 115 with toner. The toner supply device 160 includes replaceable toner bottles 160Y, 160M, 160C, and 160K for each color.

  The fixing device 200 performs fixing by applying heat and pressure to the toner image on the paper. Details of the fixing device 200 will be described later.

  A case where the image forming apparatus 100 having the above configuration performs color printing on a sheet will be described. First, in the first color yellow image forming device 110Y, the photosensitive drum 112 is uniformly charged by the charging device 113, and then a latent image is formed by the laser light emitted from the exposure device 120, and developed by the developing device 115. A toner image is formed.

  The primary transfer roller 135 transfers the toner image formed on the photosensitive drum 112 onto the transfer belt 131. The photosensitive drum 112 that has undergone the primary transfer is cleaned by the cleaning device 114 to prepare for the next image creation. The cleaning device 114 stores the collected residual toner in a waste toner collection bottle (not shown) installed in the direction of taking out the image forming device (the direction of the rotation axis of the photosensitive drum).

  A similar image forming process is performed in each of the image forming apparatuses 110C, 110M, and 110K for C, M, and K to form toner images of the respective colors, and sequentially superimposing the toner images formed on the transfer belt 131 in advance. And transcribe.

  On the other hand, the pickup roller 143 transports the paper in the paper cassettes 141 and 142 to the paper transport device 150 by the paper transport device 150, and transfers the toner image formed on the transfer belt 131 to the paper by the secondary transfer roller 136. The belt conveying device 153 conveys the paper on which the toner image is transferred to the fixing device 200, and the fixing device 200 fixes the toner image on the paper and discharges it outside the apparatus.

  Next, the fixing device 200 according to the first embodiment will be described. FIG. 2 is a cross-sectional view illustrating a configuration of a fixing device of the image forming apparatus. 3 shows the structure of the fixing roller of the fixing device. FIG. 3A is a plan view, FIG. 3B is a cross-sectional view corresponding to the line BB in FIG. 2 is a block diagram showing a control system of the fixing device shown in FIG.

  In the fixing device 200 according to the first exemplary embodiment, a concave portion that is in a non-contact state with the fixing belt 210 is formed in a region where the sheet does not contact the peripheral surface of the heating roller. The fixing belt is provided with a temperature sensor that measures the temperature of the portion that has passed through the concave portion of the heating roller. The temperature sensor detects a temperature fluctuation (temperature ripple) of the fixing belt and fixes based on the temperature fluctuation. Detects the rotational running state of the belt.

  The fixing device 200 according to the first embodiment includes an annular fixing belt 210, a fixing roller 220 and a heating roller 230 around which the fixing belt 210 is wound, and a pressure roller 240. The fixing device 200 includes a tension roller 250 that presses the fixing belt 210 from the outside of the fixing belt 210 and applies tension to the fixing belt 210. The fixing roller 220 is rotationally driven by a roller drive motor 350 (not shown in FIG. 2; see FIG. 4). The heating roller 230 and the pressure roller 240 incorporate heaters 231 and 241 as heating means.

  Further, the fixing device 200 includes a web unit 260 that cleans the fixing roller 220 and an oil application device 270 that applies oil to the heating roller 230. Further, the fixing device 200 includes a pressure roller 240 and an oil tank 280 for applying silicon oil to the pressure roller 240 by accumulating silicon oil. Further, the fixing device 200 includes a temperature sensor 290 as means for detecting the temperature of the fixing belt 210. The temperature sensor 290 is a non-contact type infrared sensor, and preferably includes a thermopile (thermopile). A thermopile is an electrical element that converts thermal energy into electrical energy, and is configured by connecting a plurality of thermocouples in series or in parallel. Various other suitable means for detecting the temperature can be adopted.

  In the fixing device 200 according to the first exemplary embodiment, the peripheral surface of the heating roller 230 is provided with a concave portion 232 that is provided in a region where the paper does not contact so as to be recessed from the peripheral surface toward the center, and is in a non-contact state with the fixing belt. Form. The temperature sensor 290 measures the temperature of the portion of the fixing belt 210 that has passed through the recess 232. The temperature sensor 290 measures the temperature fluctuation (temperature ripple) of the fixing belt 210 and detects the rotational running state of the fixing belt 210. In the figure, reference numeral 157 denotes a sensor that detects the temperature of the conveyor belt 154 of the belt conveyor 153.

  Here, the temperature sensor 290 is disposed between the heating roller 230 and the inlet of the nip portion 211. This nip portion is formed between the fixing roller 220 winding portion of the fixing belt 210 and the pressure roller 240. The fixing device value 200 detects the rotational driving of the fixing belt 210 by the temperature sensor 290 and controls the temperature of the fixing belt 210 based on the detection result of the temperature sensor 290. Note that sensors for temperature control and rotation detection may be provided separately.

  Next, the heating roller 230 will be described in detail. 3A and 3B show the configuration of the heating roller, in which FIG. 3A is a plan view and FIG. 3B is a cross-sectional view corresponding to the line BB in FIG. In the fixing device 200 according to the first embodiment, two concave portions 232 are provided on the surface of the heating roller 230. The recess 232 is formed on the opposite side across the center of the heating roller 230. The recess 232 is formed in a region of the heating roller 230 where the paper does not contact (paper non-contact region in FIG. 3). Further, the width direction dimension (w in the figure) of the recess 232 is made larger than the sum of the detection width of the temperature sensor 290 and the axial movement dimension of the heating roller 230.

  In the fixing device 200 according to the first embodiment, the recesses 232 are provided at two locations, but the recesses 232 may be at least one location. The recess 232 is formed at the same position as the temperature sensor 290 in the paper width direction. Furthermore, the recess 232 only needs to be provided on one side of the heating roller 230 in the width direction. The depth of the recess 232 is sufficient if a temperature fluctuation that can be detected by the temperature sensor 290 is generated in the fixing belt 210, and this is determined based on the roller rotation linear velocity and temperature. Note that the recess 232 may be provided through the cylindrical member 235 depending on the thickness of the cylindrical member 235 of the heating roller 230.

  Next, control of the fixing device 200 will be described. The fixing device 200 controls the running state of the fixing belt 210 and the heating state of the heating roller 230 based on the detection value of the temperature sensor 290. FIG. 4 is a block diagram illustrating a control system of the fixing device according to the first embodiment. The fixing device 200 is controlled by the fixing device control device 300. The fixing device control device 300 includes a microcomputer that includes a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and the like. In the fixing device control device 300, the CPU executes a program stored in the ROM to realize its function. Note that the fixing device control device 300 is a control device that performs overall control of the image forming apparatus 100 and can share the functions thereof.

  As shown in FIG. 4, the fixing device control device 300 includes a travel state detection unit 310 and a travel control unit 320. Further, the fixing device control apparatus 300 includes a temperature detection means, a travel control means 320 for controlling the roller drive motor 350 based on the travel state detected by the travel state detection means 310, a temperature detection means 330, and a heating control means 340. With.

  The running state detection unit 310 detects the rotational running state of the fixing belt 210 from the temperature fluctuation of the fixing belt 210 detected by the temperature sensor 290. That is, the running state detection unit 310 monitors whether a low temperature region detected by the fixing belt 210 appears at a predetermined timing. This low temperature region occurs in a region corresponding to the recess 232 of the fixing belt 210, and the detection timing of the low temperature region is determined by the traveling speed of the fixing belt 210.

  The travel control unit 320 feedback-controls the roller drive motor 350 based on the detection result of the travel state detection unit 310. That is, the travel control unit 320 controls the roller drive motor 350 based on the travel speed of the fixing belt 210 based on the detection timing of the low temperature region.

  The temperature detection unit 330 detects the temperature of the fixing belt 210 from the detection value of the temperature sensor 290. The heating control unit 340 increases or decreases the voltage to the heater 231 of the heating roller 230 based on the detected temperature in a region other than the low temperature region, and controls the fixing belt 210 to have a predetermined temperature.

  As described above, according to the first embodiment, the rotational running state of the fixing belt 210 is detected without using a sensor that depends on ambient temperature conditions and without providing a detection hole that hinders structural uniformity in the fixing belt. And temperature control.

Further, according to the first embodiment, the temperature sensor 290 is disposed between the heating roller 230 and the nip portion 211. For this reason, temperature measurement can be performed in a state where the fixing belt 210 is sufficiently warmed, and it becomes easy to detect temperature fluctuations at the concave portion 232 of the heating roller 230 and a portion where the concave portion is not formed.

<Other embodiments>
In Embodiment 1, although the recessed part was formed in two places in the heating roller, the recessed part can be formed in one place or three places or more in the heating roller. Increasing the number of recesses makes it possible to accurately detect the speed of the fixing belt. In the first embodiment, a color printer is described as an example of the image forming apparatus. However, the image forming apparatus may be a copying machine, a facsimile machine, or a digital multifunction machine.

200: fixing device 210: fixing belt 211: nip portion 220: fixing roller 230: heating rollers 231, 241: heater 232: concave portion 240: pressure rollers 231, 241: heater 250: tension roller 260: web unit 270: oil application Device 280: Oil tank 290: Temperature sensor 300: Fixing device control device 310: Travel state detection means 320: Travel control means 330: Temperature detection means 340: Heating control means 350: Roller drive motor

JP 2002-40839 A JP 2010-122450 A

Claims (7)

A fixing device comprising: an annular fixing belt; a plurality of rollers that rotatably support the fixing belt; a heating unit that heats the fixing belt; and a pressure roller that presses the sheet-like recording medium against the fixing belt. In
One of the plurality of rollers is a heating roller provided with the heating means,
Wherein among the peripheral surfaces of the fixing belt contacts the heating roller, said in the region where the sheet-like recording medium is not in contact, non-contact with the fixing belt is provided as recessed toward the center of the heating roller from the circumferential surface Forming a recess that becomes
Wherein the fixing belt, comprising a temperature detecting means for detect the temperature of a portion that has passed through the concave portion of the heating roller,
A temperature fluctuation between the region of the heating roller corresponding to the portion where the concave portion of the fixing belt is provided and the region corresponding to the portion of the fixing belt where the concave portion is not provided is caused by the temperature detecting means. you detection,
A fixing device. Belt fixing device according to claim 1, characterized in that it comprises a running condition detecting means for detecting a rotational driving state before Symbol fixing belt based on the temperature change of the fixing belt detected by said temperature detecting means. The fixing device according to claim 2, further comprising a belt traveling control unit that feeds back a moving state of the fixing belt detected by the traveling state detecting unit to control a speed of the fixing belt.   The belt fixing device according to any one of claims 1 to 3, wherein the temperature detecting means is disposed between the heating roller and an inlet of a fixing nip formed by a fixing belt.   The fixing device according to claim 1, wherein the temperature detection unit includes a thermopile. The fixing according to claim 1, characterized in that it comprises a heating control means for controlling an energization state to the heating means based on the temperature of the fixing belt, wherein the temperature detecting means detects to claim 5 apparatus. A fixing device according to any one of claims 1 to 5,
An image forming unit for forming a toner image on a sheet-like recording medium conveyed to the fixing device;
An image forming apparatus comprising: