JP2007055699A - Sheet detecting device, image forming device, sheet detecting method and control method for fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve cost reduction by a simple mechanism. <P>SOLUTION: This sheet detecting device 80 is provided with a first actuator 82 and a second actuator 84 moved while abutting on a passing sheet and with one detecting part 86 detecting displacement of the first and second actuators 82, 84. The first and second actuators 82, 84 are arranged such that their positions in the sheet width direction differ from each other. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a sheet detection apparatus and an image forming apparatus having the sheet detection apparatus.

  Generally, an image forming apparatus such as a copying machine, a printer, or a facsimile is provided with a sheet detection device that detects a sheet (paper) conveyed on a conveyance path. As this type of sheet detection device, for example, a device that detects the type of sheet to be conveyed, the length of the sheet, and the like in the vicinity of a fixing device composed of a pair of rotating bodies (pressure roll and heating roll) that are pressed against each other. is there. However, when a sheet having a width smaller than the setting is conveyed (mismatch), heat is applied to the sheet in a size difference portion (non-sheet passing region of the press contact portion) between the set sheet and the passing sheet in the fixing device. In some cases, the fixing device is damaged due to overheating without being consumed. Thus, there is known a device that detects the width of a sheet by arranging a plurality of temperature sensors, photo sensors, and the like in the width direction of the sheet. Further, there is known one that monitors the temperature of the non-sheet passing portion with a sub-thermistor (second temperature detecting means) (for example, Patent Document 1).

JP 2001-282039 A

  However, in the above-described conventional invention, the cost tends to increase due to an increase in the number of parts such as sensors.

  An object of the present invention is to provide a sheet detection apparatus and an image forming apparatus that can solve the above-described conventional problems and can realize cost reduction with a simple mechanism.

  In order to achieve the above object, the first feature of the present invention is that at least two actuators that move in contact with a passing sheet, and one detector that detects displacement of the at least two actuators. And the at least two actuators are in a sheet detecting device arranged so that positions in the width direction of the sheet are different.

  Preferably, each of the at least two actuators has a detected portion that is detected by the detecting portion, and the at least two detected portions are detected by the detecting portion at different times with respect to one passing sheet. Is done.

  Suitably, the said detection part is comprised from the photo sensor.

  According to a second aspect of the present invention, a sheet supply unit that supplies a sheet having a plurality of sheet widths, and a sheet on which the toner image is formed and heated from the sheet supply unit are heated to form a sheet of the toner image. A fixing device for fixing the sheet to the sheet, and a sheet detecting device for detecting the passage of the sheet in the vicinity of the downstream side of the fixing device, and the sheet detecting device is in contact with the passing sheet and moves. And at least two actuators for detecting the displacement of the at least two actuators, the at least two actuators being arranged so that the positions in the width direction of the sheet are different, and the detection result of the sheet detection device Accordingly, the image forming apparatus includes a control unit that controls heating of the fixing device.

  Preferably, the control unit includes a determination unit that determines whether or not the sheet width of the sheet supplied from the sheet supply unit is a planned value based on a detection result of the sheet detection unit.

  A third feature of the present invention is that at least two actuators move in contact with a passing sheet, and the displacement of the at least two actuators is detected by one detection unit, and the at least two actuators are the sheet. In the sheet detection method, the positions of the sheets in the width direction are different from each other, and the passage of the sheet and the width of the sheet are detected.

  A fourth feature of the present invention is that a sheet having a plurality of sheet widths is supplied by a sheet supply unit, and the toner image is fixed on the sheet by heating the sheet on which the toner image is formed by a fixing device. The at least two actuators are moved in contact with the passing sheet, the displacement of the at least two actuators is detected by one detection unit, and the at least two actuators are positioned at different positions in the width direction of the sheet. The sheet detection device arranged detects the passage of the sheet and the width of the sheet, and the determination device planned the sheet width of the sheet supplied from the sheet supply device from the detection result of the sheet detection device. It is determined whether or not it is, and the control unit controls the heating of the fixing device according to the determination result of the determination unit. The control method of wearing the device.

  According to the present invention, it is configured to have one detection unit that detects the displacement of at least two actuators that move in contact with the passing sheet, and the at least two actuators are arranged so that the positions in the width direction of the sheet are different. Therefore, cost reduction can be realized by a simple mechanism.

Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an outline of an image forming apparatus 10 in which a fixing device according to an embodiment of the present invention is used. In FIG. 1, an image forming apparatus 10 includes an image forming apparatus main body 12, an image forming unit 14 is provided in the image forming apparatus main body 12, and a discharge unit 16 is provided on the upper portion of the image forming apparatus main body 12. At the same time, sheet supply devices 18 and 18 as sheet supply means for supplying, for example, two-stage sheets are disposed below the image forming apparatus main body 12.

  The sheet supply devices 18 and 18 include a sheet supply device main body 20 and sheet cassettes 22 and 22 in which sheets (paper sheets) 21 are accommodated. The sheet cassettes 22 and 22 are provided in the sheet supply apparatus main bodies 20 and 20 so as to be freely drawn out, and each of the sheet cassettes 22 accommodates sheets 21 having a plurality of sizes (sheet widths). Accordingly, the sheet supply devices 18 and 18 are configured to supply sheets having a plurality of sizes (sheet widths). Further, the sheet supply apparatus main body 20 is provided with a feed roll 24 and a retard roll 26 facing the feed roll 24.

  The conveyance path 28 is a sheet conveyance path from the feed roll 24 to the discharge port 29, and this conveyance path 28 is in the vicinity of the back side (the left side surface in FIG. 1) of the image forming apparatus main body 12 and supplies the sheet at the lowest end. A portion formed substantially vertically from the device 18 to a fixing device 38 to be described later is included. A transfer device 36 and an image carrier 34 which will be described later are disposed on the upstream side of the fixing device 38 in the conveyance path 28, and a registration roll 30 is disposed on the upstream side of the transfer device 36 and the image carrier 34. Further, a discharge roll 40 is disposed in the vicinity of the conveyance path 28 and the discharge port 29.

  Accordingly, the sheet 21 is fed out from the sheet cassette 22 of the sheet supply device 18 by the cooperation of the feed roll 24 and the retard roll 26, conveyed to the registration roll 30, and temporarily stopped by the registration roll 30, and takes timing. A developer image is transferred between an image carrier 34 and a transfer device 36 which will be described later, and the transferred developer image is fixed by a fixing device 38 and discharged to a discharge unit 16 by a discharge roll 40.

  The image forming unit 14 is of an electrophotographic system, and is charged by the image carrier 34 made of a photosensitive member, a charging device 42 made of, for example, a charging roll for uniformly charging the image carrier 34, and the charging device 42. An optical writing device 44 that writes a latent image on the image carrier 34 with light, a developing device 46 that visualizes the latent image of the image carrier 34 formed by the optical writing device 44 with a developer (toner), and this development A transfer device 36 configured to transfer a toner image to the sheet by the device 46, for example, a transfer roll, a cleaning device 48 for cleaning the developer remaining on the image carrier 34, and a sheet on which the toner image is formed by the transfer device 36 is heated. And a fixing device 38 for fixing the toner to the sheet. The optical writing device 44 is composed of, for example, a scanning laser exposure device, and forms a latent image on the image carrier 34 across a process cartridge 32 described later. The cleaning device 48 includes a cleaning blade 50 that contacts the image carrier 34 and a developer recovery unit 52 that stores the developer scraped off by the cleaning blade 50. The optical writing device 44 may use an LED, a surface emitting laser, or the like as another embodiment.

In the process cartridge 32, the image carrier 34, the charging device 42, the developing device 46, and the cleaning device 48 are integrated, and these can be replaced as a unit.
Further, a control device 54 as a control means is disposed in the image forming apparatus main body 12, and this control device 54 controls each part provided in the image forming apparatus main body 12.

  In FIG. 2, the peripheral configuration of the fixing device 38 is shown. The fixing device 38 includes a casing 58 that is detachably fixed to the image forming apparatus main body 12, and a heating roll 60 and a pressure roll 62 as rotating bodies are rotatably supported by the casing 58. . The pressure roll 62 is pressed against the heating roll 60 by a pressure elastic body (not shown) made of a coil spring or the like, so that a nip portion 64 is formed.

The above-described conveyance path 28 is configured in the vertical direction across the nip portion 64, and the sheet 21 (shown in FIG. 1) is conveyed from the bottom to the top. An inlet chute (conveyance guide 66) made of, for example, a plate-like metal is disposed on the downstream side of the nip portion 64.
A sheet detection device 80 is disposed in the vicinity of the downstream side of the fixing device 38.

  The pressure roll 62 has a rotating shaft 68 made of, for example, stainless steel or iron, a heat-resistant elastic body layer 70 made of, for example, silicon sponge, and a coating covering the heat-resistant elastic body layer 70. Layer 72. The heating roll 60 includes a cylindrical core 74 and a release layer 76 that covers the surface side of the core 74. A heater 78 made of, for example, a lamp is disposed in the heating roll 60 to heat the heating roll 60. A plurality of heaters 78 are arranged in the axial direction of the heating roll 60, and the heat distribution in the axial direction of the heating roll 60 can be changed by turning on or off each heater 78. The heat distribution of the heating roll 60 is controlled by the control device 54 described above.

3 and 4 show details of the sheet detection device 80. FIG.
As illustrated in FIG. 3B, the sheet detection device 80 includes a first actuator 82, a second actuator 84 disposed in the vicinity of the upper portion of the first actuator 82, and a detection unit 86. .

The first actuator 82 is a first support shaft 88 supported by the image forming apparatus main body 12 (shown in FIG. 1) so as to be rotatable (movable), a first abutting portion 90, and a detected portion. A first light shielding portion 92 is provided.
The first contact portion 90 is formed integrally with the first support shaft 88 and is disposed so as to contact a sheet passing through the conveyance path 28. Further, the first light shielding portion 92 is formed integrally with the first support shaft 88 so that when the first actuator 82 is stationary, an optical signal from the detection portion 86 described later is blocked (light-shielded). It has become.

The second actuator 84 includes a second support shaft 94 that is rotatably (movable) supported by the image forming apparatus main body 12 (shown in FIG. 1), two second contact portions 96 and 96, and It has the 2nd light-shielding part 98 as a to-be-detected part.
The second contact portions 96 are formed integrally with the second support shaft 94 at both ends of the second support shaft 94 and are disposed so as to contact the sheet passing through the conveyance path 28. . Further, the second light shielding portion 98 is formed integrally with the second support shaft 94, and when the second actuator 84 rotates (moves), an optical signal from the detection portion 86 described later is blocked (light shielding). It is supposed to be.

  The detection unit 86 includes a photosensor, and includes a light emitting unit 100 that outputs an optical signal and a light receiving unit 102 that receives the optical signal output from the light emitting unit 100. The detection unit 86 detects the movement (rotation) of the first light shielding unit 92 of the first actuator 82 and the second light shielding unit 98 of the second actuator 84. In other words, the first light shielding unit 92 and the second light shielding unit 98 block the optical path of the optical signal output from the light emitting position L1 of the light emitting unit 100 toward the light receiving position L2 of the light receiving unit 102. The light receiving unit 102 outputs a signal indicating that the optical signal is interrupted to the control device 54 (shown in FIG. 1) when the optical path is interrupted. In this way, the displacement of the two actuators is detected by one detection unit 86.

  In FIG. 4, the position at which the first contact portion 90 and the second contact portions 96, 96 of the sheet detection device 80 are disposed, the sheet having a different size in the width direction, and the nip portion 64 of the fixing device 38. The relationship with the heat distribution (temperature relative to axial position) is shown.

  As shown in FIG. 4A, the first contact portion 90 of the first actuator 82 is disposed, for example, so as to be positioned at a substantially central portion of the sheet passing through the conveyance path 28. In other words, the first contact portion 90 is positioned at the approximate center in the width direction of each of the sheets having different sizes in the width direction (for example, a narrow size sheet and a wide size sheet). Therefore, the first abutting portion 90 is disposed at a position where it abuts on all sheets passing through the conveyance path 28.

  As shown in FIG. 4A, the two second abutting portions 96, 96 of the second actuator 84 are, for example, a wide sheet side end passing through the conveyance path 28 and a narrow size. It arrange | positions so that it may be located between a sheet | seat side edge part. Accordingly, the second abutting portions 96 and 96 are disposed at positions that abut against the wide-size sheet passing through the conveyance path 28 and do not abut against the narrow-size sheet passing through the conveyance path 28. Thus, the two actuators (the first actuator 82 and the second actuator 84) are arranged so that the positions in the width direction of the sheet are different.

  FIG. 4C shows the heat distribution (temperature relative to the position in the axial direction) of the nip portion 64 of the fixing device 38 described above. The heating roll 60 has an optimum temperature (fixing temperature) corresponding to the sheet size set by the user. However, for example, when a sheet having a narrower width than the setting is conveyed (mismatch), the size difference portion between the set sheet (for example, a wide size sheet) and a passing sheet (for example, a narrow size sheet) is not detected. In the sheet passing area (A1 and A2 in FIG. 4), as shown in FIG. 4C, the heat is not consumed by the sheet, but is overheated. Therefore, the second contact portions 96, 96 of the second actuator 94 described above are portions where the heating roll 60 can be overheated in order to detect a mismatch, that is, a non-sheet passing area (A1 and A2 in FIG. 4). ) Is arranged at a position corresponding to.

5 and 6 show a series of operations of the sheet detection device 80. FIG.
5 shows a series of operations of the sheet detection device 80 when a wide size sheet passes, and FIG. 6 shows a series of operations of the sheet detection device 80 when a narrow size sheet passes.

[When passing a wide sheet]
First, the operation of the sheet detection apparatus 80 when a wide-size sheet passes is described.
When the sheet 21 is not conveyed (does not pass through) the conveyance path 28, the first actuator 82 and the second actuator 84 are stationary at the initial position (home position) as shown in FIG. is doing. At this time, the first light shielding unit 92 of the first actuator 82 blocks (shields) the optical path of the optical signal output from the light emitting unit 100 of the detection unit 86 toward the light receiving unit 102. At this time, the second light shielding portion 98 of the second actuator 84 is located at a position (outside the light receiving portion) that is out of the light emitting position L1 and the light receiving position L2 of the light emitting portion 100 and the light receiving portion 102 of the detecting portion 86.
Therefore, the light receiving unit 102 of the detection unit 86 outputs a signal (OFF) indicating that the optical signal is blocked to the control device 54 (shown in FIG. 1).

When the sheet 21 (wide-size sheet) passes through the conveyance path 28 and the leading end of the sheet 21 and the first contact portion 90 of the first actuator 82 come into contact with each other, as shown in FIG. The first actuator 82 moves around the first support shaft 88 (rotates in the direction of arrow A in FIG. 5), and the first light shielding portion 92 of the first actuator 82 moves outside the light receiving portion. At this time, since the second contact portions 96, 96 of the second actuator 84 and the leading end portion of the sheet 21 are not in contact, the second actuator 84 is in the initial position (position shown in FIG. 5A). It is stationary.
Therefore, the light receiving unit 102 of the detection unit 86 outputs a signal (ON) indicating that the optical signal is received to the control device 54 (shown in FIG. 1).

When the leading end of the sheet 21 (the wide-size sheet) passes through the first contact portion 90 of the first actuator 82, the leading end of the sheet 21 and the second actuator 84 of the second actuator 84 are shown in FIG. 2 abutment portions 96 abut. When the leading end of the sheet 21 and the second contact portion 96 come into contact with each other, the second actuator 84 moves around the second support shaft 94 (rotates in the direction of arrow B in FIG. 5), and the second actuator 84 moves. The second light-shielding part 96 of the actuator 84 passes (light-shields) the light-receiving position of the light-receiving part 102 and further moves out of the light-receiving part. At this time, since the first contact portion 90 of the first actuator 82 and the sheet 21 remain in contact with each other, the first light shielding portion 92 of the first actuator 82 moves out of the light receiving portion. ing.
Therefore, the light receiving unit 102 of the detection unit 86 is a signal (OFF) indicating that the optical signal is cut off from a signal (ON) indicating that the optical signal is received by the control device 54 (shown in FIG. 1). Further, a signal (ON) indicating that the optical signal is received is output. That is, the light receiving unit 102 outputs ON → OFF → ON to the control device 54.

When the contact between the rear end portion of the sheet 21 (the wide-size sheet) and the first contact portion 90 of the first actuator 82 is released, as shown in FIG. Moves about the first support shaft 88 (rotates in the direction of arrow C in FIG. 5), and the first light shielding portion 92 of the first actuator 82 is directed from the light emitting portion 100 of the detection portion 86 toward the light receiving portion 102. The optical path of the output optical signal is blocked (shielded). That is, the first actuator 82 returns to the initial position (home position) shown in FIG. Subsequently, when the contact between the rear end portion of the sheet 21 (the wide size sheet) and the second contact portion 96 of the second actuator 84 is released, the second actuator 84 is moved to FIG. Return to the indicated initial position (home position).
Therefore, the light receiving unit 102 of the detection unit 86 is a signal (OFF) indicating that the optical signal is cut off from a signal (ON) indicating that the optical signal is received by the control device 54 (shown in FIG. 1). Is output.

[When passing through a narrow sheet]
Next, a series of operations of the sheet detection apparatus 80 when a narrow-size sheet is passed will be described.
Here, only the parts different from the operation of the sheet detection apparatus 80 when the above-described wide-size sheet is passed will be described, and redundant description will be omitted.

Even if the leading end of the sheet 21 (narrow size sheet) passes through the first contact portion 90 of the first actuator 82, as shown in FIG. 6C, the sheet 21 (narrow size sheet) And the second contact portion 96 of the second actuator 84 are not in contact with each other, and the second actuator 84 is stationary at the initial position (home position). At this time, since the first contact portion 90 of the first actuator 82 and the sheet 21 remain in contact with each other, the first light shielding portion 92 of the first actuator 82 moves out of the light receiving portion. ing. Thus, when a narrow-sized sheet passes, the sheet and the second actuator 84 do not contact each other.
Therefore, the light receiving unit 102 of the detection unit 86 outputs a signal (ON) indicating that the optical signal is received to the control device 54 (shown in FIG. 1).

  As described above, the first light-shielding portion 92 of the first actuator 82 and the second light-shielding portion 98 of the second actuator 84 are detected by the detection portion 86 at different times with respect to one passing sheet. Thus, the passage of the sheet and the width of the sheet are detected.

FIG. 7 shows an output signal when a wide size sheet passes and an output signal when a narrow size sheet passes.
As shown in FIG. 7, due to the difference in operation between the first actuator 82 and the second actuator 84 described above, the output signal when the light receiving unit 102 of the detection unit 86 passes the wide sheet and the narrow sheet. There is a difference in the output signal when passing. Specifically, when comparing the output signal when passing through a wide sheet and the output signal when passing through a narrow sheet, the output signal when passing through a wide sheet has more ON and OFF times. Become. Thus, the difference in sheet width can be distinguished by the difference in output signal.

  Next, a method for controlling the fixing device 38 by the control device 54 will be described.

FIG. 8 shows an example of the control circuit of the control device 54.
The control device 54 includes a CPU 55 and a memory 56, and for example, a fixing device 38, a sheet supply device 18, a sheet detection device 80, and the like are connected to the control device 54. Therefore, the output signal of the sheet detection device 80 is input to the control device 54 as described above. The control device 54 controls the heating of the fixing device 38 and the sheet supply of the sheet supply device 18 in accordance with the output signal (detection result) of the sheet detection device 80.

  Next, a control method of the control device 54 will be described.

FIG. 9 shows an example of a control method of the control device 54.
As shown in FIG. 9, in step 10 (S10), the user sets a sheet size (sheet width) to be printed. Specifically, the user inputs a sheet size from a user interface device (not shown) or the like. The set sheet size (sheet width) is stored in the memory 56.

  In step 12 (S12), the control device 54 determines a heat distribution optimal for the set sheet size (sheet width). Further, the control device 54 controls each of the heaters 78 arranged in the heating roll 60 of the fixing device 38 according to the determined heat distribution.

  In step 14 (S14), the control device 54 drives the sheet supply device 18 to start sheet supply.

  In step 16 (S16), the sheet detection device 80 detects the passage of the sheet supplied from the sheet supply device 18 and the width of the sheet. The control device 54 determines whether or not the sheet has passed from the detection result of the sheet detection device 80. If it is determined that the sheet has passed within the predetermined time, the process proceeds to S18. If it is determined that the sheet has not passed within the predetermined time, the process proceeds to S26.

In step 18 (S18), the control device 54 determines whether or not the width of the sheet supplied from the sheet supply device 18 has been planned based on the detection result of the sheet detection device 80. That is, the control device 54 determines whether or not the sheet size (sheet width) set by the user matches the detection result (width of the passed sheet) of the sheet detection device 80. Specifically, the user's sheet size setting stored in the memory 56 is compared with the output signal of the detection unit 86 of the sheet detection device 80. For example, the control device 54 determines whether or not a sheet having a narrower width than the user setting is conveyed (mismatch) depending on the state of the output signal transmitted from the sheet detection device 80 (difference in output signal depending on the sheet width). judge.
If it is determined that the sheet width of the sheet supplied from the sheet supply device 18 is the expected one, the process proceeds to S22. If it is determined that the sheet width is not the expected one, the process proceeds to S20.

  In step 20 (S20), the control device 54 corrects the heat distribution of the fixing device 54. That is, a plurality of heaters 78 arranged in the heating roll 60 of the fixing device 38 are controlled according to the detection result of the sheet detection device 80 (the width of the passed sheet). For example, when a sheet having a narrower width than the setting passes, the control device 54 performs control such as lowering the target temperature of the heater 78 or turning off the heater 78 corresponding to the non-sheet passing area.

  In step 22 (S22), the control device 54 heats the sheet on which the toner image is formed with the determined heat distribution to fix the toner image on the sheet.

  In step 24 (S24), the control device 54 causes the discharge roller 40 to discharge the sheet on which the toner image is fixed to the discharge unit 16.

  In step 26 (S26), the control device 54 stops the sheet supply device 18 and the fixing device 38.

As described above, the sheet detection device 80 described above can detect the passage of the sheet and the width of the sheet, and by controlling the heating of the fixing device 38 according to the detection result of the sheet detection device 80, It is possible to prevent damage to the fixing device due to an overheated state.
In addition, as described above, the sheet detection device 80 has a simple structure that detects two actuators with a single detection unit, so that the number of components such as sensors can be reduced, thereby realizing cost reduction.

1 is a cross-sectional view of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a side view showing the periphery of the fixing device of the image forming apparatus according to the embodiment of the present invention. 1 shows a sheet detection apparatus according to an embodiment of the present invention, in which (a) is a top view of the sheet detection apparatus, and (b) is a front view of the sheet detection apparatus. The position of the first contact portion and the second contact portion of the sheet detection apparatus according to the embodiment of the present invention, the sheet having a different size in the width direction, and the heat distribution (the axial direction) of the nip portion. (A) is a top view of the sheet detection device, (b) is a schematic diagram showing sheets having different sizes in the width direction, and (c) is a graph showing a heat distribution. is there. 4A and 4B show a series of operations when a wide-size sheet passes in the sheet detection apparatus according to the embodiment of the present invention, where FIG. 5A shows a state where no sheet passes, and FIG. 5B shows a first contact portion and a sheet. (C) is a schematic view showing a state in which the second contact part and the sheet front end are in contact, and (d) is a schematic view showing a state in which the sheet rear end has passed through the first contact part. . FIG. 6 shows a series of operations when a narrow-size sheet passes in the sheet detection apparatus according to the embodiment of the present invention, where (a) shows a state where no sheet passes, and (b) shows a first contact portion and A state in which the front end of the sheet is in contact, (c) is a state in which the first contact portion is in contact with the front end of the sheet, and (d) is a schematic diagram illustrating a state in which the rear end of the sheet has passed through the first contact portion. It is. 6 is a time chart showing output signals when a wide size sheet passes and a narrow size sheet passes in the sheet detection apparatus according to the embodiment of the present invention. 2 is a block diagram illustrating a control circuit used in the image forming apparatus according to the embodiment of the present invention. FIG. 5 is a flowchart illustrating a control method in a control device used in the image forming apparatus according to the embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 12 Image forming apparatus main body 18 Sheet supply apparatus 38 Fixing apparatus 55 CPU
56 memory 58 control device 80 sheet detection device 82 first actuator 84 second actuator 86 detection unit 92 first light shielding unit 98 second light shielding unit

Claims (7)

  And at least two actuators that move in contact with the passing sheet and a detection unit that detects displacement of the at least two actuators, the positions of the at least two actuators being different in the width direction of the sheet. A sheet detection apparatus, wherein the sheet detection apparatus is arranged.   Each of the at least two actuators has a detected portion that is detected by the detecting portion, and the at least two detected portions are detected by the detecting portion at different times with respect to one passing sheet. The sheet detection apparatus according to claim 1, wherein   The sheet detection apparatus according to claim 1, wherein the detection unit includes a photosensor.   Sheet supply means for supplying a sheet having a plurality of sheet widths, a fixing device that is supplied from the sheet supply means, heats the sheet on which the toner image is formed, and fixes the toner image on the sheet, and downstream of the fixing device A sheet detection device that detects the passage of the sheet in the vicinity of the side, the sheet detection device detects at least two actuators that move in contact with the passing sheet, and detects displacement of the at least two actuators A control unit that controls the heating of the fixing device in accordance with a detection result of the sheet detection device. An image forming apparatus having means.   The image forming apparatus according to claim 4, wherein the control unit includes a determination unit that determines whether the sheet width of the sheet supplied from the sheet supply unit is a planned value based on a detection result of the sheet detection unit.   At least two actuators contact and move on the passing sheet, and the displacement of the at least two actuators is detected by one detection unit, and the at least two actuators are arranged so that the positions in the width direction of the sheet are different. The sheet detection method detects the passage of the sheet and the width of the sheet. A sheet supply means supplies a sheet having a plurality of sheet widths,
A fixing device that heats the sheet on which the toner image is formed and fixes the toner image on the sheet;
A sheet in which at least two actuators move in contact with the passing sheet, the displacement of the at least two actuators is detected by one detection unit, and the at least two actuators are arranged at positions in the width direction of different sheets. The detection device detects the passage of the sheet and the width of the sheet,
The determination unit determines whether or not the sheet width of the sheet supplied from the sheet supply unit is a planned one based on the detection result of the sheet detection device,
A control method of a fixing device in which heating of the fixing device is controlled by a control unit according to a determination result of the determination unit.

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