JP2018021997A - Fixing apparatus and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing apparatus which can detect a paper jam before fixation earlier.SOLUTION: A fixing apparatus 5 includes a fixing member 41 to be heated, a pressure member 42 which is brought into pressure contact with the fixing member 41 to form a fixing nip N, and temperature detection means 44 which detects a temperature of the fixing member 41. The temperature detection means 44 is arranged facing the fixing member 41 upstream of the fixing nip N in a conveyance direction of a sheet, across a conveyance path 29 of the sheet moving toward the fixing nip N, detects a temperature of the fixing member 41 when the sheet is not conveyed in a detection area between the temperature detection means 44 and the fixing member 41, and detects a temperature of the sheet when the sheet is conveyed in the detection area, to detect entry and exit of the sheet, on the basis of a difference between the detected temperatures.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a fixing device that fixes a toner image onto a sheet and an image forming apparatus including the fixing device.

  Image forming apparatuses such as printers and copiers are provided with a fixing device that fixes a toner image onto a sheet. The fixing device includes a fixing member to be heated and a pressure member pressed against the fixing member, and the sheet passes through a fixing nip formed between the fixing member and the pressure member, so that the toner The image is heated and pressurized and fixed on the paper.

  In such a fixing device, the temperature of the fixing member is detected by a temperature sensor, and the temperature of the fixing member is managed based on the detected temperature. As the temperature sensor, a non-contact type temperature sensor is generally used.

  Patent Document 1 and Patent Document 2 describe a fixing device that includes a temperature sensor that is disposed on the downstream side of the fixing nip in the sheet conveyance direction with a conveyance path interposed therebetween and detects the temperature of the fixing member in a non-contact manner. Yes. In these fixing devices, the presence / absence of a sheet can be detected based on the difference between the temperature of the fixing member detected by the temperature sensor and the temperature of the sheet passing through the fixing nip. In the fixing device described in Patent Document 2, the passage time of a sheet is detected from the presence or absence of the sheet, and the occurrence of a paper jam or the like is detected.

JP-A-2-236579 JP-A-10-198216

  However, like the fixing device described in Patent Document 2, when detecting the paper passage time after detecting the temperature of the paper after passing through the fixing nip, it takes time until the paper passes through the fixing nip. Thus, detection of a paper jam occurring at the transfer unit is delayed. If the detection is delayed, the length of the jammed paper that wraps around the image carrier increases, making it difficult to remove the jammed paper, or the image carrier is subjected to a heavy load due to friction between the image carrier and the jammed paper. Problem occurs.

  SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a fixing device that can detect a paper jam occurring before fixing, and an image forming apparatus including the fixing device.

  In order to achieve the above object, a fixing device of the present invention includes a heated fixing member, a pressure member that presses against the fixing member to form a fixing nip, and a temperature detection member that detects the temperature of the fixing member. The temperature detecting member is disposed opposite to the fixing member on the upstream side of the fixing nip with respect to the sheet conveyance direction with the sheet conveyance path toward the fixing nip interposed therebetween. The temperature of the fixing member is detected when the sheet is not conveyed through the detection area between the temperature detection means and the fixing member, and the temperature of the sheet is detected when the sheet is conveyed through the detection area. Detecting and detecting the entry and exit of the paper from the detection area based on the detected temperature difference.

  By adopting such a configuration, the sheet can be detected at an earlier stage, so that the conveyance failure of the sheet can be detected at an early stage.

  An image forming apparatus according to the present invention includes the fixing device described above, a transfer device that is provided upstream of the fixing device in the transport direction and transfers a toner image from an image carrier to a sheet, and the transfer device. And a pre-transfer paper detection member provided on the upstream side in the transport direction to detect entry and exit of the paper, and a predetermined time has elapsed from the time when the pre-transfer paper detection member detected entry of the paper. If the temperature detection member does not detect the entry of the sheet later, it is determined that the sheet is not properly conveyed.

  By adopting such a configuration, it is possible to detect a paper conveyance failure that occurs in the transfer device at an early stage, thereby shortening the length of the paper that wraps around the image carrier, simplifying the removal of the paper and at the time of paper removal. The load on the image carrier from the paper can be reduced.

  According to the present invention, the sheet can be detected at an earlier stage, so that the conveyance failure of the sheet can be detected at an early stage.

1 is a cross-sectional view schematically showing an internal structure of a color printer according to an embodiment of the present invention. FIG. 2 is a diagram illustrating the periphery of a secondary transfer unit and a fixing device of a color printer according to an embodiment of the present invention. 6 is a flowchart illustrating paper detection processing of the color printer according to the embodiment of the present invention.

  Hereinafter, a fixing device and an image forming apparatus according to an embodiment of the present disclosure will be described with reference to the accompanying drawings.

  First, the overall configuration of a color printer 1 as an image forming apparatus will be described with reference to FIG. FIG. 1 is a schematic diagram showing an outline of a color printer. In the following description, the front side of the sheet of FIG. 1 is the front side (front side) of the color printer 1, and the left-right direction is based on the direction of the color printer 1 viewed from the front side.

  The apparatus main body 2 of the color printer 1 includes a paper feed cassette 3 that accommodates the paper S, an image forming unit 4 that forms a full-color toner image on the paper S, and a fixing device 5 that fixes the toner image on the paper S. A discharge device 6 for discharging the paper S on which the toner image is fixed and a paper discharge tray 7 for receiving the discharged paper S are provided.

  The image forming unit 4 includes an exposure device 9, an image forming unit 10 provided for each toner of four colors (yellow, magenta, cyan, and black), an intermediate transfer unit 11 provided above each image forming unit 10, And a toner container 12 for storing toner of each color.

  The image forming unit 10 includes a photosensitive drum 15 on which an electrostatic latent image is formed, a charging device 16 that charges the photosensitive drum 15, and a toner container 12 that corresponds to the electrostatic latent image formed on the photosensitive drum 15. A developing device 17 that develops the toner supplied from the toner, and a cleaning device 18 that removes the toner remaining on the surface of the photosensitive drum 15.

  The intermediate transfer unit 11 includes an endless intermediate transfer belt 20 as an image carrier and four primary transfer rollers 21 disposed in a hollow portion of the intermediate transfer belt 20. The intermediate transfer belt 20 is wound between the driving roller 22 and the driven roller 23 and circulates as the driving roller 22 rotates. Each primary transfer roller 21 is opposed to the photosensitive drum 15 with the intermediate transfer belt 20 interposed therebetween, and a primary transfer portion 25 is formed between the intermediate transfer belt 20 and the photosensitive drum 15. Further, a secondary transfer roller 27 as a transfer device for transferring a toner image from the intermediate transfer belt 20 faces the drive roller 22 with the intermediate transfer belt 20 interposed therebetween, and between the intermediate transfer belt 20 and the secondary transfer roller 27. A secondary transfer portion 28 is formed on the substrate.

  In the apparatus main body 2, a paper conveyance path 29 is formed from the paper feed cassette 3 through the secondary transfer unit 28 and the fixing device 5 to the paper discharge device 6.

  In each image forming unit 10, after the photosensitive drum 15 is charged by the charging device 16, exposure corresponding to the image data is performed by the exposure device 9, and an electrostatic latent image is formed on the photosensitive drum 15. The electrostatic latent image is developed into a toner image by the developing device 17. The toner image is transferred from the photosensitive drum 15 to the intermediate transfer belt 20 by the primary transfer unit 25. The toner images developed by the four image forming units 10 are transferred to the intermediate transfer belt 20, so that a full-color toner image is formed on the intermediate transfer belt 20. The toner remaining on each photosensitive drum 15 is removed by the cleaning device 18.

  Further, the paper S sent out from the paper feed cassette 3 is transported along the transport path 29, and the full color toner image formed on the intermediate transfer belt 20 is transferred onto the paper S in the secondary transfer unit 28. The sheet S to which the full color toner image is transferred is conveyed to the fixing device 5, and the full color toner image is transferred to the sheet S. The paper S on which the full-color toner image is fixed is discharged from the paper discharge device 6 to the paper discharge tray 7.

  Next, the structure around the secondary transfer unit 28 and the fixing device 5 will be described with reference to FIG. FIG. 2 is a view showing the periphery of the secondary transfer unit and the fixing device.

  A conveyance path 29 from the secondary transfer unit 28 to the fixing device 5 is provided with a pre-fixing guide 31 that guides the back side surface of the paper S (the surface on which toner is not transferred). The pre-fixing guide 31 is curved so as to be directed obliquely upward to the left while being curved convexly on the right side. A pre-transfer paper detection sensor 33 is provided upstream of the secondary transfer unit 28 in the paper conveyance direction. The pre-transfer paper detection sensor 33 can use a switch with an actuator, for example. The actuator is rotatably provided so as to protrude into the transport path 29. When the leading edge of the paper S transported along the transport path 29 contacts the actuator, the actuator is pushed by the leading edge of the paper S and rotates. The switch is switched by moving, and the presence or absence of the paper S is detected.

  The fixing device 5 includes a fixing housing 40, a fixing roller 41 as a heated fixing member housed in the fixing housing 40, and a pressure roller 42 as a pressure member that forms a fixing nip N in pressure contact with the fixing roller 41. And a pair of discharge rollers 43 provided downstream of the fixing nip N in the transport direction. Further, the fixing device 5 is provided with a temperature sensor 44 and a discharged paper detection sensor 45. The temperature sensor 44 is a temperature detection unit that is provided in the pre-fixing guide 31 and detects the temperature of the fixing roller 41. The discharged paper detection sensor 45 is provided between the fixing nip N and the pair of discharge rollers 43 to detect the presence or absence of paper that has passed through the fixing nip N and to detect the winding of the paper around the fixing roller 41.

  In the fixing housing 40, an inlet 40 a and an outlet 40 b for the paper S are formed along the conveyance path 29. The inlet 40a opens obliquely downward to the right and the outlet 40b opens obliquely upward to the left. Inside the fixing housing 40, a fixing roller accommodating portion 40 c below the conveying path 29 and a pressure roller accommodating portion 40 d above the conveying path 29 are formed.

  The fixing roller 41 is rotatably supported by the fixing roller housing recess 40c and is heated by a heat source (not shown). The pressure roller 42 is rotatably supported by the pressure roller housing recess 40 d and presses against the fixing roller 41 to form a fixing nip N. The pair of discharge rollers 43 are rotatably supported by the outlet 40 b of the fixing housing 40 with the conveyance path 29 interposed therebetween. Between the fixing nip N and the pair of discharge rollers 43, a discharge guide 40e for guiding the back surface of the sheet S is provided.

  The temperature sensor 44 is an infrared sensor that detects the temperature of the detection target surface in a non-contact manner by receiving infrared light emitted from the detection target surface with the light receiving surface 44a. As such a temperature sensor 44, a thermopile can be used, for example. The temperature sensor 44 is supported by the pre-fixing guide 31 so as to face the fixing roller 41 with the conveyance path 29 interposed therebetween.

  The temperature sensor 44 detects the surface temperature of the fixing roller 41 when the sheet S is not conveyed through the detection area between the fixing roller 41 and the light receiving surface 44a, and the sheet S is conveyed through the detection area. Detects the temperature of the back side of the paper S. Since the temperature of the back side of the sheet S is lower than the temperature of the fixing roller 41, the entry of the sheet S can be detected by the detected temperature difference. That is, the timing at which the temperature changes from a high level to a low level indicates the timing at which the leading edge of the paper S enters the detection area of the temperature sensor 44, and the timing at which the temperature fluctuates from the low level to the high level is Indicates the timing of leaving the detection area.

  The discharged paper detection sensor 45 is supported by the discharge guide 40e and detects the presence or absence of the paper S conveyed along the discharge guide 40e. The discharged paper detection sensor 45 can use, for example, a switch with an actuator similar to the pre-transfer paper detection sensor 33.

  The outputs of the pre-transfer sheet detection sensor 33 and the temperature sensor 44 are input to the control unit 50, respectively. The control unit 50 controls the printing operation of the image forming unit 4 and the on / off of the heating source of the fixing device 5.

  The sheet detection process in the fixing device 6 having the above configuration will be described with reference to the flowchart of FIG.

  When the printing command is input in step S1, the control unit 50 proceeds to step S2, detects the surface temperature of the fixing roller 41 in the detection area by the temperature sensor 44, and the detected surface temperature is equal to or higher than the target temperature T. Determine whether or not. As a result, when the surface temperature of the fixing roller 41 is lower than the target temperature T, the process proceeds to step S3, and the heating source is controlled so that the surface temperature of the fixing roller 41 becomes equal to or higher than the target temperature T1. On the other hand, if the surface temperature of the fixing roller 41 is equal to or higher than the target temperature T in step S2, the process proceeds to step S4 and the conveyance of the paper S is started.

  Next, in step S5, after storing the reference time t1 when the entry of the sheet is detected by the pre-transfer sheet detection sensor 33, the process proceeds to step S6.

  In step S6, the estimated entry time t2 when the sheet S enters the detection area of the temperature sensor 44 when the sheet S is normally conveyed is calculated. The scheduled entry time t2 is a time elapsed from the reference time t1 by the time obtained by dividing the distance between the detection area of the pre-transfer paper detection sensor 33 and the detection area of the temperature sensor 44 by the conveyance speed of the paper S.

  In step S7, it is determined whether or not the entry of the sheet S is detected by the temperature sensor 44 at the scheduled entry time t2. As a result, if the temperature sensor 44 detects the entry of the sheet S at the scheduled entry time t2, it is determined that the sheet S is normally conveyed, and the process proceeds to step S8. On the other hand, if the entry of the sheet S is not detected at the scheduled entry time t2, a paper jam occurs in the conveyance path 29 from the detection area of the pre-transfer sheet detection sensor 33 to the detection area of the temperature sensor 44, that is, in the secondary transfer unit 28. Is determined to have occurred. Therefore, after proceeding to step S9 to notify of a paper jam, the process proceeds to step S10 and the printing operation in the image forming unit 4 is stopped.

  In step S8, when the sheet S is normally conveyed, a scheduled exit time t3 at which the trailing edge of the sheet S exits the detection area of the temperature sensor 44 is calculated. The scheduled exit time t3 is a time elapsed from the scheduled entry time t2 by the time obtained by dividing the length in the transport direction of the paper S by the transport speed of the paper S.

  In step S11, it is determined whether or not the exit of the sheet S is detected by the temperature sensor 44 at the scheduled exit time t3. As a result, when the temperature sensor 44 detects the withdrawal of the paper S at the scheduled withdrawal time t3, it is determined that the paper S is being conveyed normally. On the other hand, if the exit of the sheet S is not detected at the scheduled exit time t3, it is determined that a paper jam has occurred in the fixing nip N. Therefore, after proceeding to step S9 to notify the paper jam, the routine proceeds to step S10 and the printing operation in the image forming unit 4 is stopped.

  As described above, in the color printer 1 of the present invention, since the entry of the sheet S is detected on the front side of the fixing nip N, the conveyance failure of the sheet can be detected at an early stage. For example, it is possible to detect a paper jam of the paper S mainly generated in the secondary transfer unit 28 at an earlier stage than the case where the discharge paper detection sensor 45 provided on the downstream side of the fixing nip N detects the entrance of the paper S. . Therefore, the load applied to the intermediate transfer belt 20 by the jammed paper S can be reduced. That is, by detecting the paper jam at an early stage and stopping the printing operation, when the paper jam occurs in the secondary transfer unit 28, the length of the paper S wound around the intermediate transfer belt 20 can be shortened. The load applied to the intermediate transfer belt 20 is reduced by friction between the jammed paper S and the intermediate transfer belt 20, and the wound paper S can be easily taken out.

  In the case of a monocolor printer, since the length of the paper S wound around the photosensitive drum can be shortened, the load that the paper S jammed on the photosensitive drum can be reduced.

  Furthermore, since the temperature sensor 44 can detect the temperature of the fixing roller 41 and determine the conveyance failure of the paper S, the number of sensors can be reduced and the configuration and control of the fixing device 5 can be simplified. The discharged paper detection sensor 45 detects paper wrapping around the fixing roller 41 as described above, and is indispensable for ensuring safety.

  Note that the above description of the embodiment of the present invention describes a preferred embodiment of the image forming apparatus according to the present invention, and thus may have various technically preferable limitations. The technical scope of the present invention is not limited to this embodiment unless specifically described to limit the present invention. Furthermore, the constituent elements in the embodiments of the present invention described above can be appropriately replaced with existing constituent elements, and various variations including combinations with other existing constituent elements are possible. The description of the embodiment of the present invention is not intended to limit the content of the invention described in the claims.

1 Color printer (image forming device)
5 Fixing device 20 Intermediate transfer belt (image carrier)
27 Secondary transfer roller (transfer device)
33 Pre-transfer paper detection sensor 41 Fixing roller (fixing member)
42 Pressure roller (Pressure member)
44 Temperature sensor (temperature detection means)

Claims (2)

A fixing device comprising: a heated fixing member; a pressure member that presses against the fixing member to form a fixing nip; and a temperature detection unit that detects a temperature of the fixing member,
The temperature detecting means includes
The sheet is disposed opposite the fixing member on the upstream side of the fixing nip with respect to the conveyance direction of the sheet with respect to the conveyance path of the sheet toward the fixing nip.
The temperature of the fixing member is detected when the sheet is not conveyed through the detection area between the temperature detection unit and the fixing member, and the temperature of the sheet is detected when the sheet is conveyed through the detection area. And a fixing device that detects the entry and exit of the sheet from the detection area based on the detected temperature difference. A fixing device according to claim 1;
A transfer device that is provided upstream of the fixing device in the transport direction and transfers a toner image from an image carrier to paper;
A pre-transfer paper detection member that is provided upstream of the transfer device in the transport direction and detects entry and withdrawal of the paper;
An image characterized in that a paper conveyance failure is determined when the temperature detection unit does not detect the entry of the paper after a lapse of a predetermined time from the time when the pre-transfer paper detection member detects the entry of the paper. Forming equipment.

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