JP6204335B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus, and more particularly to a technique for detecting rotation of a fixing belt in a sliding IH type fixing apparatus.

  Some image forming apparatuses such as a copying machine, a printer, a facsimile machine, and a multifunction machine having these functions include a so-called sliding IH (Induction Heating) type fixing device. In the sliding IH type fixing device, since the fixing belt is likely to move outward in the rotation axis direction of the fixing belt, a belt cap is attached to the end portion of the fixing belt in the rotation axis direction. Regulates close.

  In the sliding IH type fixing device, it is necessary to monitor the rotation state of the fixing belt in order to prevent the fixing belt from being heated while the rotation of the fixing belt is stopped. Accordingly, it has been proposed to monitor the rotation state of the fixing belt by detecting the rotation of the belt cap. For example, Patent Document 1 below discloses a technique for detecting whether or not the fixing belt is rotating normally by detecting the presence or absence of rotation of a belt cap that rotates together with the fixing belt.

JP 2005-249958 A

  However, in the fixing belt rotation monitoring technique disclosed in Patent Document 1, the belt cap slips with respect to the fixing belt even though the fixing belt rotates, and the belt cap is stopped. In this case, it is erroneously detected that the fixing belt itself is stopped. In order to solve this problem, it is conceivable to bond the belt cap to the fixing belt. However, if the fixing is not performed, the belt cap is bonded to the fixing belt. There is a possibility that the fixing belt is damaged due to the concentration of the load on the portion.

  SUMMARY An advantage of some aspects of the invention is to make it possible to more accurately detect whether or not a fixing belt is rotating.

An image forming apparatus according to an aspect of the present invention includes an image forming unit that performs an image forming operation for forming a toner image on a fed recording sheet,
A fixing belt that rotates with a hollow cylinder that is heated by induction; and a press roller that is in pressure contact with the fixing belt, and a recording sheet on which a toner image is formed by the image forming unit. A fixing unit for performing a fixing process for fixing the toner image on the recording paper by niping with a press roller and heating and pressing the recording paper;
A thermistor disposed inside the hollow of the fixing belt;
A belt cap that is placed in sliding contact with the end opening of the fixing belt and is rotatable with the outer peripheral surface of the end of the fixing belt;
A rotation detection mechanism that outputs a pulse in accordance with the rotation of the belt cap;
A belt rotation monitoring unit that monitors the rotation state of the fixing belt based on the pulse, and in the case where it cannot be detected that the pulse has a high level and a low level alternately, the detected temperature of the thermistor Is maintained at a predetermined target temperature and the detected temperature of the thermistor has a temperature ripple, it is determined that the fixing belt is rotating and the belt cap is idling with respect to the fixing belt. A belt rotation monitoring unit.

  According to the present invention, when the rotation of the fixing belt is detected, it is possible to detect the state in which the belt cap is idling with respect to the fixing belt. It becomes possible.

1 is a front sectional view showing a structure of an image forming apparatus according to an embodiment of the present invention. It is a perspective view of a fixing unit. FIG. 3 is a perspective sectional view taken along the line I-I ′ of FIG. 2. It is II-II 'sectional drawing of FIG. 2 is a perspective view of a fixing belt. FIG. It is a perspective view of a belt cap. (A) is a graph showing an example of PI sensor output when the fixing belt rotates, and (B) is a graph showing an example of PI sensor output when the fixing belt is stopped. 2 is a functional block diagram illustrating a main internal configuration of the image forming apparatus. FIG. (A) is a graph showing an example of temperature change of the fixing belt, and (B) is a partially enlarged graph. It is a flowchart of a belt rotation monitoring process. It is a flowchart of an alarm process when the belt cap is slipping.

  An image processing apparatus according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a front sectional view showing the structure of an image forming apparatus according to an embodiment of the present invention.

  An image forming apparatus 1 according to an embodiment of the present invention is a multifunction machine having a plurality of functions such as a copy function, a printer function, a scanner function, and a facsimile function. The image forming apparatus 1 includes an apparatus main body 11 that includes an operation unit 47, an image forming unit 12, a fixing unit 13, a paper feeding unit 14, a document feeding unit 6, a document reading unit 5, and the like.

  The operation unit 47 receives instructions such as an image forming operation execution instruction and a document reading operation execution instruction from the operator regarding various operations and processes that can be executed by the image forming apparatus 1. The operation unit 47 includes a display unit 473 that displays operation guidance to the operator.

  When the image forming apparatus 1 performs a document reading operation, the document reading unit 5 optically reads a document fed by the document feeding unit 6 or a document placed on the document placing glass 161, Generate image data. Image data generated by the document reading unit 5 is stored in a built-in HDD or a network-connected computer.

  When the image forming apparatus 1 performs an image forming operation, it is based on image data generated by the document reading operation, image data received from a computer connected to a network, image data stored in a built-in HDD, or the like. Then, the image forming unit 12 forms a toner image on the recording paper P as a recording medium fed from the paper feeding unit 14. When performing color printing, the magenta image forming unit 12M, the cyan image forming unit 12C, the yellow image forming unit 12Y, and the black image forming unit 12Bk of the image forming unit 12 respectively A toner image is formed on the photosensitive drum 121 by charging, exposure, and development processes based on an image composed of each color component constituting data, and the toner image is formed on the intermediate transfer belt 125 by the primary transfer roller 126. Let them transcribe.

  The toner images of the respective colors transferred onto the intermediate transfer belt 125 are superimposed on the intermediate transfer belt 125 with the transfer timing adjusted to form a color toner image. The secondary transfer roller 210 passes the toner image of the color formed on the surface of the intermediate transfer belt 125 from the paper supply unit 14 through the conveyance path 190 at a nip N between the intermediate transfer belt 125 and the driving roller 125a. It is transferred to the recording paper P that has been conveyed. Thereafter, the fixing unit 13 fixes the toner image on the recording paper P to the recording paper P by thermocompression bonding. The recording paper P on which the color image has been formed after completion of the fixing process is discharged to a discharge tray 151.

  The paper feed unit 14 includes a plurality of paper feed cassettes. When the size of the recording paper is designated by the operator, the pickup roller 145 of the paper feeding cassette containing the recording paper of the size is driven to rotate, and the recording paper P contained in each paper feeding cassette is moved to the nip. Transport toward part N.

  In the case of performing double-sided printing in the image forming apparatus 1, the recording paper P having an image formed on one side by the image forming unit 12 is nipped by the discharge roller pair 159, and then the recording paper P is switched back by the discharge roller pair 159 and sent to the reverse conveyance path 195, and the conveyance roller pair 19 conveys the recording paper P again upstream in the conveyance direction of the recording paper P with respect to the nip portion N and the fixing unit 13. As a result, an image is formed on the other surface of the recording paper by the image forming unit 12.

  FIG. 2 is a perspective view of the fixing unit 13. 3 is a perspective sectional view taken along the line I-I 'of FIG. 4 is a cross-sectional view taken along the line II-II ′ of FIG. The fixing unit 13 is a sliding IH type fixing device, and includes a fixing belt 131 and a press roller 132. FIG. 5 is a perspective view of the fixing belt 131. The fixing belt 131 is a hollow cylindrical endless belt. The fixing belt 131 generates heat when an eddy current is generated on its surface by the action of a magnetic field generated by an unillustrated IH heater. A press roller 132 is pressed against the fixing belt 131. The fixing belt 131 is rotationally driven by the pressing force of the press roller 132.

  As shown in FIG. 3, a thermistor 137 is disposed inside the hollow of the fixing belt 131. The thermistor 137 detects the temperature of the fixing belt 131. A press roller 132 is in pressure contact with the fixing belt 131, and the press roller 132 is rotationally driven by a motor (not shown). The fixing unit 13 nips the recording paper P on which the toner image is formed by the image forming unit 12 with the fixing belt 131 and the press roller 132, and heats and presses the recording paper P with the fixing belt 131 and the press roller 132 to form a toner image. Is fixed on the recording paper P.

  Belt caps 133 are placed over the openings at both ends of the fixing belt 131. FIG. 6 is a perspective view of the belt cap. The belt cap 133 is attached so that its inner peripheral surface is in sliding contact with the end opening of the fixing belt 131. With this attachment, the belt cap 133 can be rotated together with the outer peripheral surface of the end portion of the fixing belt 131. That is, as the fixing belt 131 rotates, the outer peripheral surface of the end portion of the fixing belt 131 and the inner peripheral surface of the belt cap 133 are rubbed to rotate the belt cap 133.

  The fixing unit 13 further includes a rotation detection mechanism that detects the rotation of the belt cap 133. The rotation detection mechanism includes, for example, a gear 134, a rotating plate 135, and a PI sensor 136. The gear 134 meshes with the belt cap 133 and the rotating plate 135. When the belt cap 133 rotates, the gear 134 rotates, and the rotating plate 135 further rotates.

  The PI sensor 136 includes a light emitter and a light receiver (not shown) that are arranged to face each other. The rotating plate 135 has wings extending radially from the rotating shaft. The rotating plate 135 rotates with the wing passing between the light emitter and the light receiver of the PI sensor 136. In this way, the wings of the rotating plate 135 enter between the light emitter and the light receiver of the PI sensor 136, thereby blocking the light from the light emitter. As a result, as long as the rotating plate 135 is rotating, the light from the light emitter of the PI sensor 136 is intermittently interrupted, and the pulse output from the PI sensor 136 is HIGH level or LOW depending on the presence or absence of the interruption. Indicates the level status. In other words, the rotation state of the fixing belt 131 can be known according to whether the pulse output of the PI sensor 136 alternately repeats the HIGH level or LOW level state.

  FIG. 7A is a graph showing an output example of the PI sensor 136 when the fixing belt 131 rotates. When the fixing belt 131 rotates and the rotating plate 135 also rotates, as shown in FIG. 7A, the pulse output of the PI sensor 136 alternately repeats the HIGH level and LOW level states.

  On the other hand, FIG. 7B is a graph showing an example of PI sensor output when the fixing belt 131 is stopped. When the fixing belt 131 is stopped, the rotating plate 135 is also stopped. Therefore, as shown in FIG. 7B, the pulse output of the PI sensor 136 becomes a fixed value of HIGH level or LOW level.

  FIG. 8 is a functional block diagram showing the main internal configuration of the image forming apparatus 1. The image forming apparatus 1 includes a control unit 10, an operation unit 47, a document feeding unit 6, a document reading unit 5, an image memory 32, an image forming unit 12, a fixing unit 13, a drive motor 70, a facsimile communication unit 71, and a network interface unit. 91, HDD 92, and the like.

  The document reading unit 5 includes a reading mechanism 163 (FIG. 1) having a light irradiation unit, a CCD sensor, and the like under the control of the control unit 10. The document reading unit 5 reads an image from the document by irradiating the document with the light irradiating unit and receiving the reflected light with a CCD sensor.

  The image memory 32 is an area for temporarily storing document image data obtained by reading by the document reading unit 5 and temporarily storing data to be printed by the image forming unit 12.

  The facsimile communication unit 71 includes an unillustrated encoding / decoding unit, modulation / demodulation unit, and NCU (Network Control Unit), and performs facsimile transmission using a public telephone network.

  The network interface unit 91 includes a communication module such as a LAN board, and transmits and receives various data to and from the local area or the computer 20 on the Internet via a LAN connected to the network interface unit 91.

  The HDD 92 is a large-capacity storage device that stores document images and the like read by the document reading unit 5.

  The driving motor 70 is a driving source that applies a rotational driving force to each rotating member of the image forming unit 12, the conveyance roller pair 19, and the like.

  The control unit 10 includes a CPU (Central Processing Unit), a RAM, a ROM, a dedicated hardware circuit, and the like, and controls overall operation of the image forming apparatus 1. The control unit 10 includes a control unit 100 and a belt rotation monitoring unit 101.

  The control unit 100 includes an operation unit 47, a document feeding unit 6, a document reading unit 5, an image memory 32, an image forming unit 12, a fixing unit 13, a drive motor 70, a facsimile communication unit 71, a network interface unit 91, an HDD 92, and the like. And control each of these parts.

  The belt rotation monitoring unit 101 monitors the rotation state of the fixing belt 131 based on the pulse output from the PI sensor 136. For example, as shown in FIG. 7A, when a pulse is output from the PI sensor 136, the belt rotation monitoring unit 101 alternately changes the state of the pulse output of the PI sensor 136 to the HIGH level or the LOW level. With the repetition, it is determined that the fixing belt 131 is rotating. On the other hand, as shown in FIG. 7B, when the pulse output of the PI sensor 136 is fixed at a constant level, the belt rotation monitoring unit 101 determines that the fixing belt 131 is stopped.

  However, if the frictional force between the fixing belt 131 and the belt cap 133 is weak, the belt cap 133 does not slide and does not rotate despite the rotation of the fixing belt 131. As a result, the pulse output of the PI sensor 136 is as shown in FIG. As shown in (B), there is no change from a certain level. For this reason, in this embodiment, the belt rotation monitoring unit 101 immediately stops the fixing belt 131 when the pulse output of the PI sensor 136 is at a constant level without alternately indicating the HIGH level and the LOW level. It is set not to be judged as being. In this case, the belt rotation monitoring unit 101 further refers to the detected temperature of the thermistor 137 and determines whether or not the belt cap 133 is slipping.

  FIG. 9A is a graph showing an example of temperature change of the fixing belt 131. FIG. 9B is a graph in which part of FIG. 9A is enlarged. Note that the temperature of the fixing belt 131 can be known from the temperature detected by the thermistor 137.

  As shown in FIG. 9A, when the controller 100 starts heating the fixing belt 131 and rotationally driving the press roller 132, the fixing belt 131 reaches a predetermined target temperature (for example, 165 to 166 ° C.). Heated. After the temperature of the fixing belt 131 reaches the target temperature, the control unit 100 performs control to keep the temperature of the fixing belt 131 constant while monitoring the temperature detected by the thermistor 137.

  Even when the control unit 100 performs control to keep the temperature of the rotating fixing belt 131 constant, the temperature of the fixing belt 131 varies slightly as shown in FIG. 9B. In other words, if a ripple occurs in the temperature of the fixing belt 131 during the control for keeping the temperature of the fixing belt 131 at the target temperature constant, it can be said that the fixing belt 131 is rotated and the fixing process is correctly performed. . Therefore, when the pulse output of the PI sensor 136 becomes the above-described constant level, the belt rotation monitoring unit 101 refers to the detected temperature of the thermistor 137 and the detected temperature of the thermistor 137 is the target temperature (for example, the target temperature). When the temperature ripple is generated and the fixing belt 131 is rotating normally, it is determined that the belt cap 133 is slipping. Accordingly, an erroneous stop of rotation of the fixing belt 131 is detected such that it is detected that the fixing belt 131 is not rotating because the belt cap 133 is not rotating even though the fixing belt 131 is rotating normally. Detection can be eliminated.

  Next, the rotation monitoring process of the fixing belt 131 by the belt rotation monitoring unit 101 will be described. FIG. 10 is a flowchart of the belt rotation monitoring process.

  The belt rotation monitoring unit 101 refers to the output signal of the PI sensor 136, and if the pulse indicating the HIGH level and the LOW level alternately is output from the PI sensor 136 (YES in S1), the fixing belt 131. Is determined to be rotating (S2).

  If the PI sensor 136 does not output a pulse indicating the HIGH level and LOW level alternately, that is, if the pulse output of the PI sensor 136 has not changed from the constant level (NO in S1), the belt The rotation monitoring unit 101 refers to the temperature detected by the thermistor 137 (S3). If the detected temperature of the thermistor 137 is not the target temperature (NO in S4), the belt rotation monitoring unit 101 determines that the rotation of the fixing belt 131 is stopped (S5).

  If the detected temperature of the thermistor 137 is the target temperature (YES in S4), the belt rotation monitoring unit 101 determines whether a ripple is generated in the detected temperature of the thermistor 137 (S6). If no ripple is generated (NO in S6), the belt rotation monitoring unit 101 determines that the fixing belt 131 is stopped (S5). On the other hand, if a ripple has occurred (YES in S6), the belt rotation monitoring unit 101 indicates that the fixing belt 131 is rotating but the belt cap 133 is not slid and does not rotate. It is determined that the vehicle is idling (S7).

  Even if the belt cap 133 slips, the fixing process can be performed normally if the fixing belt 131 rotates correctly. However, the situation in which the belt cap 133 is slipping cannot be said to be a normal state and should be corrected. Therefore, when it is determined that the belt cap 133 is slipping, the user may be notified of it.

  Next, alarm processing when the belt cap 133 is slipping will be described. FIG. 11 is a flowchart of alarm processing when the belt cap 133 is slipping.

  When the belt rotation monitoring unit 101 determines that the belt cap 133 is slipping (YES in S11), the control unit 100 confirms whether the printing process is being performed. Then, the control unit 100 waits for the printing process to end if printing is in progress (NO in S12), stops heating the fixing belt 131 during non-printing, and stops the rotation of the press roller 132 (S13). ). This is because even if the belt cap 133 is slipping, if the fixing belt 131 is rotating, the fixing process can be performed normally, and the printing process does not have to be forcibly interrupted.

  Thereafter, after the printing process is resumed by another print job process or the like (S14), when the belt rotation monitoring unit 101 determines again that the belt cap 133 slips and slips (YES in S15), the control is performed. The unit 100 causes the display unit 473 to display an abnormality alarm for the fixing unit 13 (S16). Thus, by displaying an alarm on the display unit 473, the operator can be urged to maintain the fixing unit 13. Although the fixing belt 131 is rotating normally, the belt cap 133 is idling. Although the printing is possible, the belt cap 133 is not properly attached to the fixing belt 131. The operator can be prepared for future problems.

  As described above, according to the present embodiment, the rotation of the fixing belt 131 can be correctly detected even if the belt cap 133 slips and stops with respect to the fixing belt 131.

  The present invention is not limited to the configuration of the above embodiment, and various modifications can be made. Further, in the above-described embodiment, the multi-function device is described as an embodiment of the image forming apparatus according to the present invention. However, this is only an example, and other image forming devices such as a copier, a printer, and a facsimile machine are used. It may be a device.

  Moreover, the structure and process shown by the said embodiment using FIG. 1 thru | or FIG. 11 are only one Embodiment of this invention, and are not the meaning which limits this invention to the said structure and process.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 12 Image forming part 13 Fixing part 131 Fixing belt 132 Press roller 133 Belt cap 134 Gear (Rotation detection mechanism)
135 Rotating plate (Rotation detection mechanism)
136 PI sensor (rotation detection mechanism)
137 Thermistor 100 Control unit 101 Belt rotation monitoring unit 473 Display unit P Recording paper

Claims (4)

An image forming unit that performs an image forming operation for forming a toner image on the fed recording paper;
A fixing belt that rotates with a hollow cylinder that is heated by induction; and a press roller that is in pressure contact with the fixing belt, and a recording sheet on which a toner image is formed by the image forming unit. A fixing unit for performing a fixing process for fixing the toner image on the recording paper by niping with a press roller and heating and pressing the recording paper;
A thermistor disposed inside the hollow of the fixing belt;
A belt cap that is placed in sliding contact with the end opening of the fixing belt and is rotatable with the outer peripheral surface of the end of the fixing belt;
A rotation detection mechanism that outputs a pulse in accordance with the rotation of the belt cap;
A belt rotation monitoring unit that monitors the rotation state of the fixing belt based on the pulse, and in the case where it cannot be detected that the pulse has a high level and a low level alternately, the detected temperature of the thermistor Is maintained at a predetermined target temperature and the detected temperature of the thermistor has a temperature ripple, it is determined that the fixing belt is rotating and the belt cap is idling with respect to the fixing belt. An image forming apparatus comprising: a belt rotation monitoring unit that performs the above operation.   When the belt rotation monitoring unit cannot detect that the pulse indicates a state having a high level and a low level alternately, the belt rotation monitoring unit maintains a predetermined target temperature of the thermistor or The image forming apparatus according to claim 1, wherein when the detected temperature of the mister does not satisfy any of the conditions for having a temperature ripple, it is determined that the rotation of the fixing belt is stopped. A controller that controls heating of the fixing belt and rotation of the press roller;
The control unit stops heating of the fixing belt and rotation of the press roller during non-printing when the belt rotation monitoring unit determines that the belt cap is idling. The image forming apparatus described in 1. It has a display unit that displays various information,
The image forming apparatus according to claim 3, wherein when the belt rotation monitoring unit determines again that the belt cap is idling after resuming printing, the control unit displays an alarm on the display unit.