JP4564814B2 - Non-contact temperature detection device for fixing device - Google Patents

Description

  The present invention relates to a temperature detecting device for a fixing device of an image forming apparatus, and more particularly to a non-contact temperature detecting device for a fixing device having a heating roller having a built-in heating source and a pressure roller in pressure contact with the heating roller.

  Some image forming apparatuses such as copiers and printers form a color image on a transfer material by superimposing a plurality of color toners. For example, a full-color copying machine has an image reading unit that reads an original image and an image processing unit that decomposes the read original image into four color components of cyan, magenta, yellow, and black. Then, an electrostatic latent image for each color component is formed on the peripheral surface of the photosensitive drum by the exposure unit, and the electrostatic latent image formed on the photosensitive drum is developed into a corresponding color by four developing devices. The toner image formed on the photosensitive drum is sequentially transferred onto the intermediate transfer member to form a color toner image that is laminated. The color toner image transferred onto the intermediate transfer member is transferred onto a transfer material and conveyed to a fixing device. The fixing device is provided with a heating roller having a built-in heater and a pressure roller in pressure contact with the heating roller. The transfer material on which the toner image is formed is nipped and conveyed by the pressure contact portion between the heating roller and the pressure roller, and the color toner image on the transfer material is heated and melt-fixed by the heat from the heating roller and the pressure from the pressure roller. Is done.

  In such a fixing device, a temperature control mechanism for controlling energization of a heating source such as a heater lamp is provided so that the surface temperature of the heating roller is maintained in a temperature range suitable for fixing. Here, in order to detect the surface temperature of the heating roller, temperature detection means for detecting the surface temperature of at least one of the heating roller and the pressure roller is provided. Conventionally, as a temperature detection means, a contact-type temperature detection means in which a temperature detection element or the like is directly attached to the surface of a heating roller as a detection target has been proposed (for example, Patent Document 1). When such a temperature detecting means is in contact with the roller, there is a problem in that as the number of fixing sheets increases, the surface of the roller is rubbed and the image quality deteriorates.

  Therefore, it has been proposed to detect the temperature without bringing the temperature detecting element into contact with the roller. This non-contact type temperature detecting means includes, for example, an infrared absorbing member disposed so as to face the roller, and a thermistor for detecting the temperature of the infrared absorbing member.

In the fixing device, toner scattering or paper dust scattering occurs during image formation. If these scattered materials adhere to the infrared absorbing member, the accuracy of the detected temperature is adversely affected. Therefore, a non-contact temperature detection device has been proposed in which a cleaning mechanism for cleaning the surface of the sensor or a mechanism for detecting dirt on the infrared absorbing film is provided.
JP-A-7-286911 JP 2000-242131 A JP 2003-90763 A

  In the fixing device of the image forming apparatus, it is necessary to detect the surface temperature of the heating roller or the like and control it to a temperature suitable for fixing in order to improve the fixing performance of the toner image. In order to accurately detect the surface temperature of the object to be detected, such as a heating roller, it is necessary to remove the effects of toner and other contaminants on the non-contact temperature detection device. It is difficult to remove dirt, and such dirt may reduce the accuracy of temperature detection.

  An object of the present invention is to provide a non-contact temperature detecting device capable of suppressing the influence of the dirt attached to the temperature detection sensor on the temperature detection accuracy and accurately detecting the temperature even when the dirt is attached.

  A non-contact temperature detecting device for a fixing device according to claim 1 is a non-contact temperature detecting device for a fixing device having a heating roller having a built-in heating source and a pressure roller in pressure contact with the heating roller. Temperature sensor, a diaphragm mechanism, and a drive mechanism.

  Here, the non-contact type temperature detection sensor is for detecting the temperature of the detection object, and has a light receiving portion. The aperture mechanism is for adjusting the amount of light received by the light receiving portion of the temperature detection sensor. The drive mechanism is for driving the aperture mechanism.

  In this apparatus, when detecting the temperature of the heating roller, the non-contact temperature detection sensor detects the amount of light received by the light receiving unit and detects the temperature. In the fixing device, toner scattering or paper dust scattering occurs at the time of image formation. If these scattering toner or paper dust adheres to a non-contact temperature detection device, particularly a light receiving part, it will adversely affect accurate temperature detection. Will be given.

  In this apparatus, the amount of light received by the light receiving portion of the temperature detection sensor is adjusted by a diaphragm mechanism. For example, when dirt is attached to the light receiving unit and the amount of received light is reduced, the sensitivity of the temperature sensor is adjusted by opening the aperture. Therefore, accurate temperature detection is possible even when dirt is attached to the temperature detection sensor.

  According to a second aspect of the present invention, there is provided the non-contact temperature detecting device for a fixing device according to the first aspect, wherein the diaphragm mechanism includes a shutter and a shutter adjustment mechanism. Here, the shutter adjustment mechanism adjusts the amount of light received by the light receiving unit by adjusting the size of the shutter opening.

  In the fixing device, toner scattering or paper dust scattering occurs during image formation. If these scattered objects adhere to the non-contact temperature detecting device, the accuracy of the detected temperature is adversely affected.

  Therefore, in this apparatus, the size of the shutter opening is adjusted by the shutter adjustment mechanism, and the amount of light received by the temperature detection sensor light receiving unit is adjusted. For example, when dirt is attached to the light receiving unit and the amount of received light decreases, the sensitivity of the temperature sensor is adjusted by opening the shutter opening. Therefore, accurate temperature detection is possible even when dirt is attached to the temperature detection sensor.

  According to a third aspect of the present invention, there is provided the non-contact temperature detecting device for a fixing device according to the second aspect, wherein the shutter is two parallel plates arranged at a constant interval, and the shutter adjustment mechanism connects the parallel plates by parallel links. The distance between the parallel plates is adjusted by operating the parallel link.

  In this device, parallel plates arranged at regular intervals are connected by parallel links to form a parallel ruler, and therefore the distance between the parallel plates can be adjusted by inclining the parallel links. The size of the shutter opening can be adjusted by the structure.

  A non-contact temperature detecting device for a fixing device according to a fourth aspect is the device according to the third aspect, wherein the drive mechanism includes a rack connected to the link, a worm meshing with the rack, and a stepping for rotating the worm. And a motor.

  In this apparatus, the worm is rotated by the stepping motor, the rack engaged with the worm is linearly moved by the rotation of the worm, and the link connected to the rack is operated. Accordingly, the link operation can be realized with a simple structure, and the size of the shutter opening can be adjusted.

  The fixing device non-contact temperature detecting device according to claim 5 is the device according to claim 3, wherein the drive mechanism is a solenoid. Here, the position of the aperture mechanism is determined by a solenoid, so that the cost of the drive mechanism can be reduced and the installation space can be reduced.

  A non-contact temperature detecting device for a fixing device according to a sixth aspect is the device according to any one of the first to fifth aspects, wherein the contact-type temperature sensor for measuring the temperature of the heating roller and the control for controlling the driving of the driving mechanism are used. The unit is further provided. Here, the control unit automatically adjusts the sensitivity of the temperature detection sensor by controlling the drive mechanism based on the temperature difference between the measurement value of the contact temperature sensor and the measurement value of the non-contact temperature detection sensor. Can do.

  A non-contact temperature detecting device for a fixing device according to a seventh aspect is the device according to any one of the first to sixth aspects, wherein the temperature detecting sensor is an infrared temperature sensor. In this apparatus, the surface temperature of the detection object can be measured in a non-contact manner by an infrared temperature sensor.

  In the present invention, the amount of light received by the light receiving portion of the temperature detection sensor is adjusted by the diaphragm mechanism. For example, when the amount of light received decreases due to dirt on the light receiving portion, the sensitivity of the temperature sensor is adjusted by opening the diaphragm. Therefore, accurate temperature detection is possible even when dirt is attached to the temperature detection sensor.

  FIG. 1 is a cross-sectional view of an entire image forming apparatus in which an embodiment of the present invention is employed. A photoconductive drum 2 using an a-Si type photoconductor is disposed almost at the center of the color image forming apparatus 1 having a substantially rectangular parallelepiped shape. Around the photosensitive drum 2, a charging device 3, a yellow developing device 4, a magenta developing device 5, a cyan developing device 6, a black developing device 7, an intermediate transfer member 8, and a cleaning device 9 are arranged. The yellow developing device 4, the magenta developing device 5, and the cyan developing device 6 have a yellow toner cartridge 10, a magenta toner cartridge 11, and a cyan toner cartridge 12, respectively. A black toner cartridge 13 of the black developing device 7 is disposed above the intermediate transfer member 8. An exposure device 14 is disposed above the black toner cartridge 13. A secondary transfer roller 15 is disposed below the intermediate transfer member 8, and a separation device 16, a conveyance belt 17, and a fixing device 18 are disposed downstream of the secondary transfer roller 15 in the sheet conveyance direction. . A discharge device 40 is disposed on the upper left side of the device 1.

  The photosensitive drum 2 has an electrostatic latent image formed on the surface. The charging device 3 is installed above the photosensitive drum 2 and is a device for uniformly charging the surface of the photosensitive drum 2. The exposure device 14 is a device for forming an electrostatic latent image on the photosensitive drum 2 based on a document image read from an image data input unit (not shown). The developing devices 4, 5, 6, and 7 are devices that form toner images by supplying toner to the surface of the photosensitive drum 2 on which the electrostatic latent image is formed, and correspond to yellow, magenta, cyan, and black, respectively. Is provided. Similarly, the toner cartridges 10, 11, 12, and 13 supply yellow, magenta, cyan, and black toners. The intermediate transfer member 8 serves as a transfer member on which the toner image formed on the photosensitive drum 2 is transferred and temporarily held. The transfer device 15 is a device for transferring the toner image on the intermediate transfer body 8 to a sheet. The separating device 16 is for separating the paper onto which the toner image has been transferred from the intermediate transfer body 8. The conveyance belt 17 is for conveying the sheet on which the toner image is transferred to the fixing device. The fixing device 18 is for melting and fixing the toner image by heating and pressing, and fixing the toner image on the transfer material. The cleaning device 9 is a device for cleaning deposits such as residual developer remaining on the photosensitive drum 2.

  Here, as shown in FIG. 2a, the fixing device 18 includes a heating roller 21 incorporating a heating source (for example, a heater) and a heating roller 21 provided so as to be in pressure contact with the heating roller 21 in the Y-axis direction of FIG. 2a. The pressure roller 22 and a non-contact temperature detection device 23 that detects the surface temperatures of the heating roller 21 and the pressure roller 22 in a non-contact manner with respect to both the rollers 21 and 22 are provided. The non-contact temperature detection device 23 is disposed at substantially the same position as the central rotation axis of the heating roller 21 in the Y-axis direction in FIG. The non-contact temperature detection device 23 includes a temperature detection sensor 24 and a rotating shaft 25 that holds the temperature detection sensor 24. Further, as shown in FIG. 2 b, a contact-type temperature sensor 30 that measures the temperature of the heating roller 21 in contact with the non-sheet passing region of the heating roller 21 is provided.

  The temperature detection sensor 24 includes an infrared temperature-sensitive non-contact thermistor 24a, a transparent casing 24b provided so as to cover the periphery of the thermistor 24a, and a portion where infrared rays are incident on the thermistor 24a on the outer surface of the casing 24b. And an infrared transmission film 24c provided.

  An aperture mechanism 26 is disposed between the non-contact temperature detection device 23 and the heating roller 21. As shown in FIGS. 3A and 3B, the diaphragm mechanism 26 has shutter plates 50A and 50B arranged in parallel, and the parallel links 51A and 51B are shuttered by pins a, a ′, b, and b ′. The plates 50A and 50B are linked to form a so-called parallel crank. The link 51A is further connected to one end of the link 51C by a pin c. The other end of the link 51C is connected to the rack 52 by a pin d. The rack 52 has inclined teeth and is disposed so as to mesh with the worm gear 54 of the drive mechanism 53. The drive mechanism 53 includes a worm gear 54 and a stepping motor 55. The stepping motor 55 is provided on the further back side of the frame 35 on the back side of the apparatus, and a worm gear 54 that meshes with the rack 52 is integrally formed at the tip of the motor shaft 55. The links 51A and 51B are rotatably attached to a base plate (not shown) by pins e and e ', respectively.

  With the configuration as described above, when the stepping motor 55 is rotated forward and backward, the worm gear 54 is rotated forward and backward. When the worm gear 54 is rotated forward and backward, the rack 52 meshed with the worm gear 54 performs a linear motion to the left and right, and the link 51C pin-connected to the rack 52 is also tilted to the left and right. For example, in the first position in FIG. 3, it is assumed that the parallel crank composed of the parallel shutter plates 50A and 50B and the parallel links 51A and 51B is rectangular, and the link 51A and the link 51C are perpendicular to each other. At this time, the interval between the parallel shutter plates 50A and 50B is the maximum, and the amount of light received by the non-contact temperature sensor 24 is also the maximum. Therefore, the link 51C is moved to the right by rotating the stepping motor 55 and rotating the worm gear 54. Then, since one end of the link 51C is connected to the link 51A by the pin c, the link 51A rotates clockwise around the pins e and e ′, and includes the shutter plates 50A and 50B and the parallel links 51A and 51B. The entire parallel crank is tilted to the right. That is, the second position represented by the dotted line in FIG. 3 is obtained, and the interval between the shutter plate 50A and the shutter plate 50B is narrowed. At this time, the amount of light received by the non-contact temperature sensor 24 is minimal. On the other hand, when the link 51C moves to the left, since one end of the link 51C is connected to the link 51A by the pin c, the link 51A rotates counterclockwise around the pins e and e ′, and the shutter plate 50A, The entire parallel crank composed of 50B and the parallel links 51A and 51B is tilted to the left and recovered to the first position. This movement increases the distance between the shutter plate 50A and the shutter plate 50B. The diaphragm mechanism 26 adjusts the amount of light transmitted to the non-contact temperature sensor 24 by such movement.

  FIG. 4 shows a control block of the fixing device. Here, only the configuration related to the control of the aperture mechanism is shown. The control unit 60 includes a microcomputer having a CPU, a RAM, a ROM, and the like, and is connected to the non-contact temperature detection sensor 24, the stepping motor 55 that drives the aperture mechanism, and the contact temperature detection sensor 30.

  Next, an image forming operation will be described. At the time of image formation, the photosensitive drum 2 is charged by the charging device 3 and then exposed by the exposure device 14 to form an electrostatic latent image on the photosensitive drum 2. When the photosensitive drum 2 rotates and reaches the developing position of the yellow developing device 4 that is the first color, an electrostatic latent image corresponding to yellow is converted into a toner image by the developing device 4 and the surface of the photosensitive drum 2 corresponds to yellow. A toner image is formed. Such an operation is also performed for other colors (magenta, cyan, black). The toner images of the respective colors formed on the surface of the photosensitive drum 2 are sequentially transferred to the intermediate transfer member 8, whereby a full color toner image is formed on the intermediate transfer member 8. Thereafter, a full-color toner image is transferred to a transfer material 19 conveyed from a paper feeding unit (not shown) to a transfer position in synchronization with the transfer bias applied to the transfer device 15. The transfer material onto which the full-color toner image has been transferred is separated from the intermediate transfer member 8 by the separation device 16 and conveyed to the fixing device 18 by the conveyance belt 17. Further, the full-color toner image transferred to the transfer material 19 is fixed to the transfer material by heating and pressing by the fixing device 18, and the transfer material is discharged to the paper discharge unit 40.

  Here, toner scattering or paper dust scattering occurs in the fixing device 18 during image formation. When these scattered toner or scattered paper scraps adhere to the infrared absorption film 24c of the non-contact temperature detecting device 23, the temperature detection is adversely affected. In this embodiment, when the diaphragm mechanism 26 is provided between the non-contact temperature sensor 24 and the heating roller 21 that is the detection target, and the infrared absorbing film 24c that is the light receiving portion of the non-contact temperature sensor 24 is contaminated, By increasing the shutter opening of the diaphragm mechanism 26 compared to the case where dirt does not occur, the light shielding rate of the diaphragm mechanism 26 is reduced, the amount of light received by the infrared absorbing film 24c is increased, and the sensor caused by the dirt on the infrared absorbing film 24c. Reduce the effect of sensitivity. The control unit 60 sets the relationship between the measurement error of the infrared temperature sensor 24 due to contamination of the infrared absorbing film 24c and the light shielding rate of the diaphragm mechanism 26 as shown in Table 1, and performs control based on this set value.

  In the image forming process, the diaphragm mechanism 26 is controlled as shown in the flowchart of FIG. When the image forming apparatus is turned on, various parameters are initialized, and initial settings such as setting the temperature of the fixing unit 18 are executed. Next, in step S1, the temperature values of the non-contact temperature sensor 24 and the contact temperature sensor 30 are collated. In step S2, it is determined whether or not the difference between the temperature value of the non-contact temperature sensor 24 and the temperature value of the contact temperature sensor 30 is 35 ° C. or less. When the temperature difference is 35 ° C. or more, the process proceeds to step S3 and cleaning is performed by a cleaning mechanism (not shown). When the temperature difference is 35 ° C. or less, the process proceeds to step S4, and it is determined whether or not the relationship between the temperature difference and the light shielding rate of the diaphragm mechanism 26 is within the set value range of Table 1. If the relationship between the temperature difference and the light blocking rate of the diaphragm mechanism 26 is not within the set value range of Table 1, the process proceeds to step S5, and the light blocking rate of the diaphragm mechanism 26 is adjusted. Specifically, when the difference between the temperature value of the non-contact temperature sensor 24 and the temperature value of the contact temperature sensor 30 is 0 ° C., the aperture amount of the aperture mechanism 26 is maximized, and the shutter plate 50A and the shutter plate 50B. Is set to 30%. For example, by rotating the stepping motor 55 and rotating the worm gear 54, the rack 52 is moved to the right, and thus the link 51C is moved to the right. When the link 51C moves to the right, since one end of the link 51C is connected to the link 51A by the pin c, the link 51A also tilts to the right, and is formed of the shutter plates 50A and 50B and the parallel links 51A and 51B. The entire crank tilts to the right. That is, the second position represented by the dotted line in FIG. 3 is obtained, and the interval between the shutter plate 50A and the shutter plate 50B is narrowed. At this time, the amount of light received by the non-contact temperature sensor 24 is minimal.

  On the other hand, when the difference between the temperature value of the non-contact temperature sensor 24 and the temperature value of the contact temperature sensor 30 is, for example, 7 ° C., the light shielding rate by the shutter plate 50A and the shutter plate 50B is set to 20%. . Specifically, by rotating the stepping motor 55 and rotating the worm gear 54, the rack 52 is moved to the left, and thus the link 51C is moved to the left. When the link 51C moves to the left, the entire parallel crank composed of the shutter plates 50A and 50B and the parallel links 51A and 51B tilts to the left. By such adjustment, the interval between the shutter plate 50A and the shutter plate 50B is widened.

  Further, for example, when the difference between the temperature value of the non-contact temperature sensor 24 and the temperature value of the contact temperature sensor 30 is 35 ° C., the light shielding rate by the shutter plate 50A and the shutter plate 50B is set to 0%. Specifically, by rotating the stepping motor 55 and rotating the worm gear 54, the rack 52 is further moved to the left, and thus the link 51C is further moved to the left. When the link 51C moves to the left, the entire parallel crank composed of the shutter plates 50A and 50B and the parallel links 51A and 51B is tilted to the left and becomes the first position in FIG. At this time, the parallel crank composed of the parallel shutter plates 50A and 50B and the parallel links 51A and 51B is rectangular, the link 51A and the link 51C are perpendicular to each other, and the distance between the parallel shutter plates 50A and 50B is the maximum. It is. That is, the amount of light received by the non-contact temperature sensor 24 is also the maximum.

Next, in step S6, it is determined whether or not an image formation start key has been pressed. When the image formation start key is pressed, the process proceeds to step S7, and image formation is performed. After the image formation is completed, the process proceeds to step S8, and it is determined whether or not the image formation is ended. If the image formation is not finished, the process returns to step S2. On the other hand, when the image formation is finished, the process returns.
[Effect of this embodiment]
When a diaphragm mechanism 26 is provided between the non-contact temperature sensor 24 and the heating roller 21 that is a detection object, and the infrared absorbing film 24c that is a light receiving portion of the non-contact temperature sensor 24 is contaminated, the dirt is not generated. By increasing the aperture of the shutter of the diaphragm mechanism 26, the light shielding rate of the diaphragm mechanism 26 is reduced, the amount of light received by the infrared absorbing film 24c is increased, and the influence of sensor sensitivity due to contamination of the infrared absorbing film 24c is reduced. Can be suppressed.

1 is a schematic diagram of an image forming apparatus. The enlarged view of a fixing device. The perspective view of a fixing device. The schematic block diagram of a non-contact temperature detection apparatus. Control block of the fixing device. Control flow of fixing device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Color image forming apparatus 2 Photosensitive drum 18 Fixing device 21 Heating roller 22 Pressure roller 23 Non-contact temperature detection device 24 Non-contact temperature detection sensor 25 Rotating shaft 26 Diaphragm mechanism 28 Heating source 30 of a heating roller Contact-type temperature detection sensor 50A , 50B Shutter plates 51A, 51B, 51C Link 52 Rack 53 Drive mechanism 54 Worm gear 55 Stepping motor 60 Aperture control unit

Claims (7)

A non-contact temperature detecting device for a fixing device, comprising a heating roller having a built-in heating source and a pressure roller in pressure contact with the heating roller,
A non-contact type non-contact temperature detection sensor having a light receiving unit;
A diaphragm mechanism for adjusting the amount of light received by the light receiving portion of the non-contact temperature detection sensor;
A drive mechanism for driving the aperture mechanism;
A contact temperature sensor for measuring the temperature of the heating roller;
A control unit for controlling the drive of the drive mechanism,
The control unit controls the drive mechanism based on a temperature difference between a measurement value of the contact temperature sensor and a measurement value of the non-contact temperature detection sensor.
Non-contact temperature sensing device Fixing device. The diaphragm mechanism is
Shutter,
A shutter adjustment mechanism that adjusts the amount of light received by the light receiving unit by adjusting the size of the opening of the shutter;
The non-contact temperature detecting device for a fixing device according to claim 1. The shutter is two parallel plates arranged at regular intervals,
The shutter adjustment mechanism adjusts the distance between the parallel plates by connecting the parallel plates with a parallel link and operating the parallel link.
The non-contact temperature detecting device for a fixing device according to claim 2. The drive mechanism is
A rack connected to the link;
A worm meshing with the rack;
A stepping motor for rotating the worm,
The non-contact temperature detecting device for a fixing device according to claim 3. The drive mechanism is a solenoid coupled to the link;
The non-contact temperature detecting device for a fixing device according to claim 3. The non-contact temperature detecting sensor is an infrared temperature-sensitive sensor, non-contact temperature sensing device of the fixing device according to any one of claims 1 to 5. A fixing device having a heating roller containing a heating source and a pressure roller in pressure contact with the heating roller;
A non-contact temperature detecting device for a fixing device according to claim 1.
Image forming apparatus.

Images