JP5018853B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

2. Description of the Related Art Image forming apparatuses such as laser printers are provided with a fixing device that fixes a toner image transferred onto a recording sheet to the sheet.
The fixing device includes a heating roller having a built-in heater, and a pressure roller disposed in a pressed state on the heating roller. The recording paper onto which the toner image has been transferred is conveyed between the heating roller and the pressure roller with the surface onto which the toner image has been transferred facing the heating roller. Then, while the recording paper passes between the heating roller and the pressure roller, the toner is fixed to the recording paper by heating and pressing.

The recording paper on which the toner image has been fixed is usually separated from the heating roller and the pressure roller in that order from the leading edge, and is conveyed on a conveyance path extending toward the paper discharge tray. However, the leading edge of the recording paper may move while adhering to the surface of the heating roller, and the recording paper may not be conveyed on the conveyance path.
In view of this, some image forming apparatuses employ a configuration for detecting a conveyance failure of the recording paper in the fixing device. In this image forming apparatus, for example, sensors for detecting the passage of the recording paper are provided on the upstream side and the downstream side in the conveyance direction of the recording paper with respect to the fixing device. Then, if the passage of the recording paper is not detected by the downstream sensor within a certain time from the detection of the passage of the recording paper by the upstream sensor, it is determined that a recording paper conveyance failure has occurred in the fixing device. When it is determined that a recording paper conveyance failure has occurred, the operation of the image forming apparatus is immediately stopped.

JP 2006-139034 A

  However, until a certain time has elapsed since the detection of the passage of the recording paper by the upstream sensor, the recording paper conveyance failure is not detected, and the rotation of the heating roller is continued. For this reason, there is a possibility that the leading end of the recording paper attached to the heating roller makes one turn or more as the heating roller rotates, and the recording paper is wound around the heating roller. When the recording paper is wound around the heating roller, it becomes difficult to remove the recording paper, and in the worst case, the fixing device cannot be used.

  An object of the present invention is to provide an image forming apparatus capable of preventing a recording sheet from being wound around a heating member.

In order to achieve the above object, the present invention can rotate so that the recording sheet carrying the developer image contacts the surface, and the portion of the surface that contacts the recording sheet moves in the moving direction of the recording sheet. provided, the heating member for fixing the developer image to the recording sheet by heating, and the conveyance path of the recording sheet was peeled from the heating member is conveyed, the surface and the transport path and parallel to the swing of the heating member capable of pivoting about an axis, a pivot shaft extending along said pivot axis, a swing member which Ru and a fixed posture correcting member to the swing axis, the attitude correction member said A biasing member that biases in a direction orthogonal to the swing axis, and a posture correction member that faces the posture correction member from the downstream side in the biasing direction of the biasing member, receives the posture correction member, and Holding part to hold in posture If, e Bei a detection member for detecting the swinging of the swinging member, the detection member is an optical sensor comprising a pair of light receiving elements for receiving light from the light emitting element and the light emitting element, wherein The swinging member includes a first abutting piece that abuts on the recording sheet conveyed through the conveyance path, and a second abutting that abuts on the recording sheet that moves in the direction along the surface of the heating member together with the surface of the heating member. And a position where the optical path between the light emitting element and the light receiving element is out of the optical path and the optical path is blocked when the swinging member swings due to the recording sheet coming into contact with the first contact piece. A first light-shielding piece that oscillates to the second contact piece, and a position that deviates from the optical path and a position that blocks the optical path when the oscillating member oscillates when the recording sheet comes into contact with the second contact piece. A swinging second shading piece, the first abutment piece, front The second abutment piece, the first light shielding piece, the second light shielding piece, and the posture correcting member are integrally formed, and the first light shielding piece and the second light shielding piece are respectively swung. The optical sensors are formed to have different shapes so that different detection signals are output from the optical sensors .

According to the present invention, the recording sheet carrying the developer contacts the surface of the heating member. The heating member rotates so that the portion of the surface that contacts the recording sheet moves in the moving direction of the recording sheet. While the recording sheet is in contact with the surface of the heating member, the developer image is fixed on the recording sheet by heating from the heating member.
The recording sheet is usually peeled from the surface of the heating member in order from the front end and conveyed on the conveyance path. A first contact piece of the swinging member is disposed on the transport path, and the recording sheet transported through the transport path contacts the first contact piece. The swing member is provided so as to be swingable around a swing axis parallel to the surface of the heating member and the conveyance path. When the recording sheet comes into contact with the first contact piece, the swing member swings about the swing axis, and the swing is detected by the detection member. Therefore, when the swing of the swing member due to the contact of the recording sheet with the first contact piece is detected, it can be determined that the recording sheet is normally conveyed.

  On the other hand, the recording sheet that moves in the direction along the surface of the heating member together with the surface of the heating member does not peel from the surface of the heating member, but the recording sheet contacts the second contact piece of the swinging member. When the recording sheet comes into contact with the second contact piece, the swing member swings about the swing axis, and the swing is detected by the detection member. Accordingly, when the swing of the swing member due to the contact of the recording sheet with the second contact piece is detected, the recording sheet is removed from the conveyance path and extends along the surface of the heating member along with the surface of the heating member. It can be determined that it is moving. Accordingly, by taking measures such as stopping the operation of the apparatus in response to the detection, it is possible to prevent the recording sheet from being wound around the heating member.

FIG. 1 is a side sectional view of a laser printer according to an embodiment of the present invention. FIG. 2 is a schematic side view of the paper detection mechanism and shows a state in which the swinging member is in a standby posture. FIG. 3 is a schematic side view of the swing member and the posture correcting mechanism. FIG. 4 is a schematic side view of the paper detection mechanism and shows a state in which the swing member is in the first posture. FIG. 5 is a schematic side view of the paper detection mechanism and shows a state in which the swing member is in the second posture. FIG. 6 is a schematic side view of the sheet detection mechanism according to the first reference example , and shows a state in which the swinging member is in a standby posture. FIG. 7 is a schematic side view of the paper detection mechanism according to the first reference example , and shows a state in which the swing member is in the first posture. FIG. 8 is a schematic side view of the sheet detection mechanism according to the first reference example , and shows a state in which the swing member is in the second posture. FIG. 9 is a schematic side view of the paper detection mechanism according to the second reference example , and shows a state in which the swinging member is in a standby posture. FIG. 10 is a schematic side view of the sheet detection mechanism according to the second reference example , and shows a state in which the swing member is in the first posture. FIG. 11 is a schematic side view of the sheet detection mechanism according to the second reference example , and shows a state in which the swing member is in the second posture. FIG. 12 is a schematic side view of the sheet detection mechanism according to the second embodiment of the present invention, and shows a state in which the swing member is in a standby posture. FIG. 13 is a schematic side view of the paper detection mechanism according to the second embodiment of the present invention, and shows a state in which the swing member is in the first posture. FIG. 14 is a schematic side view showing the configuration of the paper detection mechanism according to the second embodiment of the present invention, and shows a state in which the swinging member is in a standby posture. FIG. 15 is a schematic side view of a swing member and a posture correcting mechanism according to a modification of the configuration shown in FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
1. Laser Printer As shown in FIG. 1, a laser printer 1 as an example of an image forming apparatus includes a main body casing 2. A process cartridge 3 is provided in the main casing 2. The process cartridge 3 is detachably provided in the main casing 2 with the front cover 4 provided in the main casing 2 being opened.

In addition, let the side in which the front cover 4 is provided in the main body casing 2 be a front side, and let the opposite side be a rear side. Therefore, the front cover 4 is provided on the front surface of the main casing 2. Further, when the laser printer 1 is viewed from the front side, the left and right reference is used.
The process cartridge 3 includes a drum cartridge 5 and a developing cartridge 6 that is detachably attached to the drum cartridge 5 from the front.

A photosensitive drum 7 is rotatably provided on the drum cartridge 5. In the drum cartridge 5, a scorotron charger 8 and a transfer roller 9 are disposed around the photosensitive drum 7.
The developing cartridge 6 is provided with a developing roller 10. A part of the circumferential surface of the developing roller 10 is exposed from the housing of the developing cartridge 6 and is in contact with the photosensitive drum 7 from the upper front side.

A scanner unit 11 is disposed above the process cartridge 3.
As the photosensitive drum 7 rotates, the surface of the photosensitive drum 7 is uniformly charged by the scorotron charger 8 and then exposed by the laser beam emitted from the scanner unit 11. As a result, an electrostatic latent image is formed on the surface of the photosensitive drum 7. When the electrostatic latent image faces the developing roller 10 as the photosensitive drum 7 rotates, toner is supplied to the electrostatic latent image, and a toner image is formed on the surface of the photosensitive drum 7.

  At the bottom of the main casing 2, a paper feed cassette 12 that stores paper P as an example of a recording sheet is disposed. The paper P stored in the paper feed cassette 12 is conveyed to a transfer position between the photosensitive drum 7 and the transfer roller 9 by various rollers. The toner image on the surface of the photosensitive drum 7 is transferred to the paper P when facing the paper P by the action of the transfer bias applied to the transfer roller 9.

A fixing unit 13 is provided behind the process cartridge 3. The paper P on which the toner image is transferred is conveyed to the fixing unit 13. In the fixing unit 13, the toner image is fixed on the paper P by heating and pressing. The paper P on which the toner image is fixed is discharged to a paper discharge tray 14 on the upper surface of the main body casing 2 by various rollers.
2. Fixing Unit (1) Configuration for Fixing As shown in FIG. 1, the fixing unit 13 includes a box-shaped frame 21 whose front and rear surfaces are open. A heating roller 22 and a pressure roller 23 as an example of a heating member are rotatably held in the frame 21.

The heating roller 22 is formed in a cylindrical shape extending in the left-right direction. Inside the heating roller 22, a heater 24 such as a halogen lamp is incorporated. When power is supplied to the heater 24 from a power source (not shown) provided in the main body casing 2, the heater 24 generates heat and the heating roller 22 is heated.
The pressure roller 23 is disposed at a position below the rear side with respect to the heating roller 22 and is formed in a cylindrical shape extending in the left-right direction. The pressure roller 23 is in pressure contact with the peripheral surface of the heating roller 22 from the lower rear side by an urging mechanism (not shown).

  At the time of fixing the toner image on the paper P, the heating roller 22 rotates clockwise in FIG. Further, the pressure roller 23 rotates counterclockwise in FIG. As a result, the paper P is conveyed between the heating roller 22 and the pressure roller 23 from the front side to the rear side. At this time, the paper P is heated and pressed by the heating roller 22 and the pressure roller 23, and the toner image is fixed on the paper P.

Behind the heating roller 22 and the pressure roller 23, a conveyance path 25 is formed through which the paper P that has passed between the heating roller 22 and the pressure roller 23 is conveyed. Specifically, the transport path 25 is formed on a guide member 27 whose front end faces the upper part of the circumferential surface of the pressure roller 23 and extends upward on the rear side.
(2) Paper Detection Mechanism As shown in FIG. 2, a paper detection mechanism 30 for detecting passage of the paper P and winding around the heating roller 22 is provided in the frame 21.

The paper detection mechanism 30 includes a swing member 31 that is swingable with respect to the frame 21 and an optical sensor 32 as an example of a detection member for detecting the swing of the swing member 31. Yes.
The swing member 31 includes a contact member 28, a light shielding member 29, a swing shaft 33, and a posture correction member 41.

  The contact member 28 is bent at a substantially right angle in a side view, and one piece 35 has an L shape longer than the other piece 36. The one piece 35 forms a first abutting piece with which the sheet P conveyed through the conveying path 25 abuts. The other piece 36 forms a second contact piece with which the paper P moving in the circumferential direction of the heating roller 22 comes into contact. The tip of the first contact piece 35 is in contact with the guide member 27 in a state where the swing member 31 is in the standby posture shown in FIG. In this state, the tip of the second contact piece 36 is in contact with the surface of the heating roller 22.

The light shielding member 29 has an L shape bent substantially at a right angle in a side view, and has a first light shielding piece 37 and a second light shielding piece 38 extending from the bent portion with substantially the same length. In the second light shielding piece 38, a plurality of slits 39 extending from the front edge to the bent portion of the light shielding member 29 are formed at equal intervals. Thereby, the front-end | tip part of the 2nd light-shielding piece 38 has comprised the comb-tooth shape.
The contact member 28 and the light shielding member 29 are joined in a state where the bent portions are overlapped in the left-right direction so as to form a cross shape in a side view as a whole. More specifically, in the contact member 28 and the light shielding member 29, the first contact piece 35 and the second light shielding piece 38 extend on the same straight line, and the second contact piece 36 and the light shielding member 38 on a straight line orthogonal to the straight line. Each bent portion is joined in a state of being overlapped in the left-right direction so that the first light shielding piece 37 extends.

  The swing shaft 33 extends in the left-right direction, passes through the bent portions of the contact member 28 and the light shielding member 29, and is provided so as not to rotate with respect to the contact member 28 and the light shielding member 29. A base end portion of the swing shaft 33 is rotatably held by the frame 21. Thereby, the contact member 28 and the light shielding member 29 are supported by the swing shaft 33 and are provided so as to be able to swing integrally with the central axis of the swing shaft 33 as the swing axis.

  As shown in FIG. 3, the posture correcting member 41 is attached to the tip of the swing shaft 33 so as not to be relatively rotatable. The posture correcting member 41 is formed in a substantially triangular shape having a top portion 45 that protrudes downward. The top portion 45 is gently curved along the circumferential direction of the swing shaft 33. As a result, the posture correcting member 41 is formed in a shape having an upper surface 46 extending in the horizontal direction and a substantially V-shaped lower surface whose apex is rounded as a whole.

  A holding member 42 that is substantially V-shaped in a side view is provided below the posture correcting member 41. Specifically, the holding member 42 is fixedly provided below the posture correction member 41, and one end of the holding member 42 extends from the lower side of the posture correction member 41 to the front upper side, and the other end extends from the lower side of the posture correction member 41 to the rear side. It extends upward. Thus, the upper surface 47 of the holding member 42 is formed in a V-shape that protrudes downward. The apex angle formed by the V shape on the upper surface of the holding member 42 is substantially equal to the apex angle formed by the V shape on the lower surface of the posture correction member 41.

  A coil spring 43 as an example of a biasing member that biases the posture correcting member 41 toward the holding member 42 is interposed between the posture correcting member 41 and the frame 21 in a compressed state. Specifically, one end of the coil spring 43 is connected to the upper surface 46 of the posture correction member 41. The other end of the coil spring 43 is connected to the frame 21 at a position above the posture correction member 41. Thereby, the posture correcting member 41 is always urged downward by the coil spring 43.

In a state where the sheet P is not in contact with the contact member 28, the lower surface of the posture correcting member 41 is in contact with the upper surface 47 of the holding member 42 by the bias of the coil spring 43, and the swinging member 31 is in the standby state shown in FIG. Held in posture.
The optical sensor 32 is fixedly disposed at a position above the rear side with respect to the swing member 31. More specifically, as shown in FIG. 2, the optical sensor 32 is disposed at a position between the first light shielding piece 37 and the second light shielding piece 38 with the swinging member 31 in the standby posture. ing.

The optical sensor 32 includes a light emitting unit and a light receiving unit that face each other in the left-right direction. When the light from the light emitting unit is received by the light receiving unit, an ON signal is output from the light receiving unit. In the state where the swing member 31 is in the standby posture, the optical path between the light emitting unit and the light receiving unit is not blocked, and thus an ON signal is transmitted from the light receiving unit. Further, when the optical path between the light emitting unit and the light receiving unit is blocked, an off signal is output from the light receiving unit.
3. Oscillating operation of the oscillating member (1) Normal time The paper P on which the toner image has been transferred is conveyed backward by the rotation of the heating roller 22 and the pressure roller 23, and between the heating roller 22 and the pressure roller 23. Passes through the nip portion 26. At this time, the sheet P is usually peeled from the heating roller 22 in order from the leading end (the leading end in the transport direction). Then, the paper P is transported rearward along the transport path 25, and the leading end thereof contacts the first contact piece 35 from the front side.

When the paper P further moves, the first contact piece 35 is pushed backward by the paper P as shown in FIG. Thereby, the swing member 31 rotates around the swing shaft 33 in the direction in which the first contact piece 35 moves rearward (clockwise in FIG. 4).
By the rotation of the swing member 31, the swing member 31 assumes the first posture shown in FIG. With the swinging member 31 in the first posture, the tip of the first light shielding piece 37 is disposed at a position that blocks the optical path between the light emitting unit and the light receiving unit in the optical sensor 32. As a result, the output signal of the optical sensor 32 (light receiving unit) is turned off, and it is detected that the paper P is in contact with the first contact piece 35.

When the paper P is further transported along the transport path 25 and the paper P is separated from the nip portion 26, the rear end portion of the paper P is in a state along the upper surface of the guide member 27. Then, the swinging member 31 is returned to the standby posture by the action of the posture control member 41, the holding member 42, and the coil spring 43. Specifically, in a state in which the swing member 31 is in the first posture, the posture correction member 41 is tilted so that the upper surface 46 is lowered forward by the force received from the paper P. When the rear end portion of the sheet P is separated from the first contact piece 35 and the application of the force of the sheet P to the first contact piece 35 is released, the posture correcting member 41 is applied by the urging force of the coil spring 43. Is biased toward the upper surface 47 of the holding member 42. Accordingly, the posture of the posture correcting member 41 is corrected so that the upper surface 46 of the posture correcting member 41 is horizontal. Since the posture correcting member 41 and the swing shaft 33 are connected so as not to rotate relative to each other, when the posture of the posture correcting member 41 is corrected, the posture of the swing member 31 is set to the standby posture via the swing shaft 33. Returned to
(2) At the time of abnormality On the other hand, when the paper P moves in the direction along the surface of the heating roller 22 (rotation direction) together with the surface of the heating roller 22 while the front end portion of the paper P is in contact with the surface of the heating roller 22, The leading edge of the paper P contacts the second contact piece 36 from below.

When the paper P further moves along the surface of the heating roller 22, the second contact piece 36 is pushed upward by the paper P as shown in FIG. As a result, the swing member 31 rotates in the direction away from the surface of the heating roller 22 (counterclockwise in FIG. 5) with the second contact piece 36 moving upward about the swing shaft 33.
By the rotation of the swing member 31, the swing member 31 assumes the second posture shown in FIG. In a state where the swing member 31 is in the second posture, the tip of the second light shielding piece 38 is disposed at a position that blocks the optical path between the light emitting unit and the light receiving unit in the optical sensor 32. The tip part of the second light shielding piece 38 is formed in a comb shape. Therefore, as the second light shielding piece 38 moves, the slit 39 and the portion where the slit 39 is not formed are alternately opposed to the optical path. As a result, the output signal of the optical sensor 32 is alternately switched between an off signal and an on signal. Thereby, it is detected that the paper P is in contact with the second contact piece 36.

When it is detected that the paper P is in contact with the second contact piece 36, the operation of each part of the laser printer 1 is stopped. Thereafter, when the paper P that has started to be wound along the surface of the heating roller 22 is removed, the swing member 31 is returned to the standby posture by the posture correcting mechanism 40 shown in FIG. Specifically, in a state where the swing member 31 is in the second posture, the posture correction member 41 has its upper surface 46 lowered downwardly against the biasing force of the coil spring 43 due to the force received from the paper P. So as to be inclined. When the sheet P is removed and the application of the force of the sheet P to the first contact piece 35 is released, the lower surface of the posture correcting member 41 is directed toward the upper surface 47 of the holding member 42 by the biasing force of the coil spring 43. Be energized. Accordingly, the posture of the posture correcting member 41 is corrected so that the upper surface 46 of the posture correcting member 41 is horizontal. Since the posture correcting member 41 and the swing shaft 33 are connected so as not to rotate relative to each other, when the posture of the posture correcting member 41 is corrected, the posture of the swing member 31 is set to the standby posture via the swing shaft 33. Returned to
4). As described above, the paper P is usually peeled from the surface of the heating roller 22 in order from the leading edge thereof, and is transported through the transport path 25. A first contact piece 35 of the swing member 31 is disposed on the transport path 25, and the paper P transported through the transport path 25 contacts the first contact piece 35. The swing member 31 is provided so as to be swingable about a swing shaft 33 parallel to the surface of the heating roller 22 and the conveyance path 25. When the paper P comes into contact with the first contact piece 35, the swing member 31 swings around the swing shaft 33.

  The swing member 31 includes a first light shielding piece 37 and a second light shielding piece 38. The first light-shielding piece 37 has a position and an optical path that are out of the optical path between the light-emitting element and the light-receiving element when the swinging member 31 swings by the sheet P coming into contact with the first contact piece 35. Swings to the blocking position. In addition, the second light shielding piece 38 swings between the position deviated from the optical path and the position blocking the optical path when the swinging member 31 swings due to the sheet P coming into contact with the second contact piece 36. .

  The first light-shielding piece 37 and the second light-shielding piece 38 are formed in different shapes so that different detection signals are output from the optical sensor 32 when each of the first light-shielding piece 37 and the second light-shielding piece 38 swings. That is, when the paper P is transported through the transport path 25, the paper P comes into contact with the first contact piece 35, and the first light shielding piece 37 swings, the shape of the first light shielding piece 37 from the light receiving portion of the optical sensor 32. A detection signal corresponding to is output. On the other hand, when the leading end of the sheet P moves along the surface of the heating roller 22 along the surface, the sheet P contacts the second contact piece 36 and the second light shielding piece 38 swings, the optical sensor. Detection signals corresponding to the shape of the second light shielding piece 38 different from the shape of the first light shielding piece 37 are output from the 32 light receiving portions.

  Therefore, based on the detection signal from the optical sensor 32, it is possible to determine whether the paper P is transported in the transport path 25 or whether the paper P is moving in the direction along the surface together with the surface of the heating roller 22. it can. When a detection signal is output from the light receiving unit of the optical sensor 32 corresponding to the shape of the second light shielding piece 38, the operation of each unit of the laser printer 1 is stopped. Thereby, the winding of the paper P around the heating roller 22 can be prevented.

Further, a single optical sensor 32 can be used as a sensor for identifying whether the paper P is transported through the transport path 25 or whether the paper P is moving along the surface of the heating roller 22 along the surface. Can do. Therefore, the number of parts of the laser printer 1 can be reduced.
In addition to the first contact piece 35, the second contact piece 36, the first light shielding piece 37, and the second light shielding piece 38, the swing member 31 includes a posture correcting member 41 integrally therewith. . A swinging shaft 33 extending along the axis of the swinging member 31 is inserted into the posture correcting member 41. Further, the posture correcting member 41 is biased by a coil spring 43 from a direction orthogonal to the swing shaft 33. A holding member 42 is disposed below the posture correcting member 41, and the posture correcting member 41 is received by the holding member 42 and held in a constant posture. Therefore, after the swinging member 31 swings, the swinging member 31 can be returned to a certain posture.

Further, when the swing member 31 swings due to the sheet P coming into contact with the second contact piece 36, the second contact piece 36 moves away from the heating roller 22. Accordingly, it is possible to prevent the second contact piece 36 from biting into the surface of the heating roller 22 when the second contact piece 36 swings.
5. First Reference Example In FIGS. 6 to 8, parts corresponding to the parts shown in FIGS. 2 to 5 are given the same reference numerals as those given to those parts. In the following, description of the parts denoted by the same reference numerals is omitted.

As shown in FIGS. 6 to 8, the sheet detection mechanism 50 according to the first reference example detects a swing member 51 that is swingable with respect to the frame 21, and swing of the swing member 51. And an optical sensor 32.
(1) Configuration of Oscillating Member The oscillating member 51 includes a first oscillating body 55, a second oscillating body 56, an oscillating shaft 53, and a spiral spring 67.

The first oscillating body 55 has a first abutting piece 57 and a first light shielding piece 58 that are bent at substantially right angles in a side view and extend from the bent portion with substantially the same length. The first contact piece 57 is in contact with the paper P that is transported through the transport path 25. The tip of the first contact piece 57 is in contact with the guide member 27 in a state where the swing member 51 is in the standby posture shown in FIG.
The second rocking body 56 is bent at a substantially right angle in a side view, and one piece 59 has an L shape shorter than the other piece 60. One piece 59 forms a second contact piece with which the paper P moving in the circumferential direction of the heating roller 22 comes into contact. In the other piece 60, a plurality of slits 61 extending from the front end edge toward the bent portion of the second rocking body 56 are formed at equal intervals. Thus, the other piece 60 forms a comb-shaped second light shielding piece. The tip of the second contact piece 59 is in contact with the surface of the heating roller 22 in a state where the swing member 51 is in the standby posture shown in FIG.

  The first oscillating body 55 and the second oscillating body 56 form a cross shape in a side view as a whole in a state where the oscillating member 51 is in the standby posture shown in FIG. More specifically, the first rocking body 55 and the second rocking body 56 have the first abutting piece 57 and the second light shielding piece 60 extending on the same straight line while the rocking member 51 is in the standby posture. The second contact piece 59 and the first light shielding piece 58 extend on a straight line orthogonal to the straight line.

  The swing shaft 53 extends in the left-right direction, passes through the bent portions of the first swing body 55 and the second swing body 56, and is provided to be rotatable relative to the first swing body 55 and the second swing body 56. ing. A base end portion of the swing shaft 53 is held by the frame 21 so as not to rotate. Thus, the first oscillating body 55 and the second oscillating body 56 are supported by the oscillating shaft 53 and are provided so as to be able to oscillate independently with the central axis of the oscillating shaft 53 as the oscillating axis.

  Two spiral springs 67 are provided independently of each other. One spiral spring 67 has one end connected to the swing shaft 53 and the other end connected to the first swing body 55. The first oscillating body 55 is urged by one spiral spring 67 in the direction in which the first light shielding piece 58 moves downward (counterclockwise in FIG. 6). The other spiral spring 67 has one end connected to the swing shaft 53 and the other end connected to the second swing body 56. And the 2nd rocking body 56 is urged | biased by the other spiral spring 67 in the direction (clockwise rotation in FIG. 6) to which the 2nd light-shielding piece 60 moves toward the front.

Further, a first regulating member 65 and a second regulating member 66 are provided in association with the first oscillating body 55 and the second oscillating body 56, respectively.
The first restricting member 65 is formed in a boss shape protruding in the left-right direction from the frame 21, and in a state where the swinging member 51 is in a standby posture, the first restricting member 65 comes into contact with the front end portion of the first light shielding piece 58 from below. Is arranged. Further rotation of the first rocking body 55 is restricted when the first light shielding piece 58 contacts the first restricting member 65 from above.

The second restricting member 66 is formed in a boss shape that protrudes in the left-right direction from the frame 21, and is in a position where it comes into contact with the front end portion of the second light shielding piece 60 from the front in a state where the swinging member 51 is in the standby posture. Is arranged. Further rotation of the second rocking body 56 is restricted when the second light shielding piece 60 contacts the second restricting member 66 from the rear.
(2) Oscillating operation of the oscillating member (2-1) Normal time The paper P on which the toner image has been transferred is conveyed backward by the rotation of the heating roller 22 and the pressure roller 23, and is pressed against the heating roller 22. It passes through a nip portion 26 between the roller 23 and the roller 23. At this time, the sheet P is usually peeled from the heating roller 22 in order from the leading end (the leading end in the transport direction). Then, the paper P is transported rearward along the transport path 25, and the leading end thereof contacts the first contact piece 57 from the front side.

When the paper P further moves, the first contact piece 57 is pushed backward by the paper P as shown in FIG. Accordingly, the first rocking body 55 rotates around the rocking shaft 53 in the direction in which the first contact piece 57 moves upward in the front side (clockwise in FIG. 7).
By the rotation of the first oscillating body 55, the oscillating member 51 assumes the first posture shown in FIG. With the swinging member 51 in the first posture, the tip of the first light shielding piece 58 is disposed at a position that blocks the optical path between the light emitting unit and the light receiving unit in the optical sensor 32. As a result, the output signal of the optical sensor 32 (light receiving unit) is turned off, and it is detected that the paper P is in contact with the first contact piece 57. Further, in a state where the swing member 51 is in the first posture, the second swing body 56 maintains the posture in a state where the swing member 51 is in the standby posture shown in FIG.

When the paper P is further transported along the transport path 25 and the paper P is separated from the nip portion 26, the rear end portion of the paper P is in a state along the upper surface of the guide member 27. Then, the swinging member 51 is returned to the standby posture by the action of the spiral spring 67 and the first regulating member 65. Specifically, in a state where the swing member 51 is in the first posture, the first swing body 55 is displaced in posture against the biasing force of the spiral spring 67 by the force received from the paper P. When the rear end portion of the paper P is separated from the first contact piece 57 and the application of the force of the paper P to the first contact piece 57 is released, the first light shielding piece is applied by the urging force of the spiral spring 67. 58 moves in a direction approaching the first restricting member 65. Thereby, the 1st rocking | fluctuation body 55 is rotated and the attitude | position of the rocking | swiveling member 51 is returned to a standby position.
(2-2) Abnormal On the other hand, the sheet P moves in the direction (rotation direction) along the surface of the heating roller 22 together with the surface of the heating roller 22 while the leading end of the sheet P is in contact with the surface of the heating roller 22 Then, the leading end portion of the paper P comes into contact with the second contact piece 59 from below.

When the sheet P further moves along the surface of the heating roller 22, the second contact piece 59 is pushed upward by the sheet P as shown in FIG. As a result, the second rocking body 56 rotates in the direction away from the surface of the heating roller 22 (counterclockwise in FIG. 8), with the second abutment piece 59 moving upward about the rocking shaft 53. .
By the rotation of the second oscillating body 56, the oscillating member 51 assumes the second posture shown in FIG. In a state where the swinging member 51 is in the second posture, the distal end portion of the second light shielding piece 60 is disposed at a position that blocks the optical path between the light emitting portion and the light receiving portion in the optical sensor 32. The distal end portion of the second light shielding piece 60 is formed in a comb-teeth shape. Therefore, as the second light shielding piece 60 moves, the slit 61 and the portion where the slit 61 is not formed alternately face the optical path. As a result, the output signal of the optical sensor 32 is alternately switched between an off signal and an on signal. Thereby, it is detected that the sheet P is in contact with the second contact piece 59. Further, in a state where the swing member 51 is in the second posture, the first swing body 55 maintains the posture where the swing member 51 is in the standby posture shown in FIG.

When it is detected that the paper P is in contact with the second contact piece 59, the operation of each part of the laser printer 1 is stopped. After that, when the paper P that has started to be wound along the surface of the heating roller 22 is removed, the swinging member 51 is returned to the standby posture by the spiral spring 67. Specifically, in a state where the swing member 51 is in the second posture, the second swing body 56 is displaced in posture against the urging force of the spiral spring 67 by the force received from the paper P. When the paper P is removed and the application of the force of the paper P to the first contact piece 57 is released, the second light shielding piece 60 moves in a direction approaching the second regulating member 66 by the urging force of the spiral spring 67. To do. Thereby, the 2nd rocking body 56 is rotated and the attitude | position of the rocking | swiveling member 51 is returned to a standby position.
(3) Effects The same effects as those of the first embodiment can be obtained by the above configuration.

The first contact piece 57 and the first light shielding piece 58 are integrally formed. Thereby, when the paper P comes into contact with the first contact piece 57, the first light shielding piece 58 can be reliably swung. The second contact piece 59 and the second light shielding piece 60 are integrally formed. Thereby, when the paper P comes into contact with the second contact piece 59, the second light shielding piece 60 can be reliably swung.
6). Second Modification In FIGS. 9 to 11, parts corresponding to the parts shown in FIGS. 2 to 5 are given the same reference numerals as those given to the parts. In the following, description of the parts denoted by the same reference numerals is omitted.

As shown in FIGS. 9 to 11, the sheet detection mechanism 70 according to the second modification detects a swing member 71 that is swingable with respect to the frame 21 and swing of the swing member 71. A first optical sensor 72 and a second optical sensor 73 are provided as an example of a detection member.
(1) Configuration of Oscillating Member The oscillating member 71 includes a contact member 78 and a light shielding piece 77.

  The contact member 78 is bent at a substantially right angle in a side view, and one piece 75 has an L shape longer than the other piece 76. One piece 75 forms a first abutting piece with which the sheet P conveyed through the conveying path 25 abuts. The other piece 76 forms a second contact piece with which the paper P moving in the circumferential direction of the heating roller 22 comes into contact. The tip of the first contact piece 75 is in contact with the guide member 27 in a state where the swing member 71 is in the standby posture shown in FIG. In this state, the tip of the second contact piece 76 is in contact with the surface of the heating roller 22.

The light shielding piece 77 has a plate shape that extends toward the rear upper side in a state where the swinging member 71 is in the standby posture and is formed wide along the circumferential direction of the swinging shaft 74.
The contact member 78 and the light shielding piece 77 are joined in a state in which the bent portion of the contact member 78 and the base end portion of the light shielding piece 77 are overlapped in the left-right direction so as to form a Y shape as viewed from the side. Has been.

  The swing shaft 74 extends in the left-right direction, passes through the bent portion of the contact member 78 and the base end portion of the light shielding piece 77, and is provided so as not to rotate with respect to the contact member 78 and the light shielding piece 77. A base end portion of the swing shaft 74 is rotatably held by the frame 21. Thereby, the contact member 78 and the light shielding piece 77 are supported by the swing shaft 74 and are provided so as to be able to swing integrally with the central axis of the swing shaft 74 as the swing axis.

  The first optical sensor 72 and the second optical sensor 73 are fixedly disposed on both sides in the circumferential direction of the swing shaft 74 with respect to the light shielding piece 77 in a state where the swing member 71 is in the standby posture. Yes. Specifically, the first optical sensor 72 is disposed at a position above the front side of the light shielding piece 77 in a state where the swinging member 71 is in the standby posture, and the second optical sensor 73 is configured such that the swinging member 71 is The light shielding piece 77 is arranged at a position below the rear side in the standby posture.

The first optical sensor 72 and the second optical sensor 73 have the same structure. That is, the first optical sensor 72 and the second optical sensor 73 include a light emitting unit and a light receiving unit that face in the left-right direction. When the light from the light emitting unit is received by the light receiving unit, an ON signal is output from the light receiving unit. In the state shown in FIG. 9 (the state in which the swinging member 71 is in the standby posture), since the optical path between the light emitting unit and the light receiving unit is not blocked, an on signal is always transmitted from the light receiving unit. Further, when the optical path between the light emitting unit and the light receiving unit is blocked, an off signal is output from the light receiving unit.
(2) Oscillating operation of the oscillating member (2-1) Normal time The paper P on which the toner image has been transferred is conveyed backward by the rotation of the heating roller 22 and the pressure roller 23, and is pressed against the heating roller 22. It passes through a nip portion 26 between the roller 23 and the roller 23. At this time, the sheet P is usually peeled from the heating roller 22 in order from the leading end (the leading end in the transport direction). Then, the sheet P is transported rearward along the transport path 25, and the leading end thereof contacts the first contact piece 75 from the front side.

When the paper P further moves, the first contact piece 75 is pushed backward by the paper P as shown in FIG. Thus, the swing member 71 rotates around the swing shaft 74 in the direction in which the first contact piece 75 moves rearward (clockwise in FIG. 10).
By the rotation of the swing member 71, the swing member 71 assumes the first posture shown in FIG. With the swinging member 71 in the first posture, the tip of the light shielding piece 77 is disposed at a position that blocks the optical path between the light emitting unit and the light receiving unit in the first optical sensor 72. As a result, the output signal of the first optical sensor 72 (light receiving unit) becomes an off signal, and it is detected that the paper P is in contact with the first contact piece 75.

When the paper P is further transported along the transport path 25 and the paper P is separated from the nip portion 26, the rear end portion of the paper P is in a state along the upper surface of the guide member 27. Then, the swing member 71 is returned to the standby posture by a posture correction member (not shown).
(2-2) Abnormality On the other hand, the sheet P moves in the direction along the surface of the heating roller 22 (rotation direction) together with the surface of the heating roller 22 while the front end of the sheet P is in contact with the surface of the heating roller 22. Then, the leading edge of the paper P comes into contact with the second contact piece 76 from below.

When the paper P further moves along the surface of the heating roller 22, the second contact piece 76 is pushed upward by the paper P as shown in FIG. As a result, the swing member 71 rotates in the direction away from the surface of the heating roller 22 (counterclockwise in FIG. 11), with the second contact piece 76 moving upward about the swing shaft 74.
By the rotation of the swing member 71, the swing member 71 takes the second posture shown in FIG. In a state where the swing member 71 is in the second posture, the tip portion of the light shielding piece 77 is disposed at a position that blocks the optical path between the light emitting portion and the light receiving portion in the second optical sensor 73. As a result, the output signal of the second optical sensor 73 is switched off, and it is detected that the paper P is in contact with the second contact piece 76.

When it is detected that the paper P is in contact with the second contact piece 76, the operation of each part of the laser printer 1 is stopped. Thereafter, when the paper P that has started to be wound along the surface of the heating roller 22 is removed, the swing member 71 is returned to the standby posture by a posture correction member (not shown).
(3) Effects The same effects as those of the first embodiment can be obtained by the above configuration.

The swing member 71 includes a light shielding piece 77 formed integrally with the first contact piece 75 and the second contact piece 76. The first optical sensor 72 is composed of a light emitting element and a pair of light receiving elements that receive light from the light emitting element, and when the swing member 71 swings due to the sheet P coming into contact with the first contact piece 75. The light path is blocked by the light shielding piece 77. Accordingly, it is possible to detect that the paper P has come into contact with the first contact piece 75 by blocking the optical path of the first optical sensor 72. The second optical sensor 73 includes a light emitting element and a pair of light receiving elements that receive light from the light emitting element, and the swinging member 71 swings when the sheet P contacts the second contact piece 76. Sometimes, the light path is arranged at a position where the light path is blocked by the light shielding piece 77. Accordingly, it is possible to detect that the sheet P has come into contact with the second contact piece 76 by blocking the optical path of the second optical sensor 73.
7). Second Embodiment In FIGS. 12 to 14, parts corresponding to the parts shown in FIGS. 6 to 8 are given the same reference numerals as those given to those parts. In the following, description of the parts denoted by the same reference numerals is omitted.

In the paper detection mechanism 50 according to the first reference example , as shown in FIGS. 6 to 8, the first light-shielding piece 58 and the second light-shielding piece 60 are made different in shape so that one optical sensor 32 can perform the first. It is configured to detect which of the first contact piece 57 and the second contact piece 59 is in contact with the paper P.
On the other hand, in the paper detection mechanism 80 according to the second embodiment of the present invention, the two members of the optical sensor (the first optical sensor 82 and the second optical sensor 83) are used. It is configured to detect swing.
(1) Configuration of Oscillating Member The oscillating member 81 includes a first oscillating body 85, a second oscillating body 86, and an oscillating shaft 84.

The first oscillating body 85 includes a first abutting piece 87 and a first light shielding piece 88 that are bent at substantially right angles in a side view and extend from the bent portion with substantially the same length. The first contact piece 87 is in contact with the paper P transported through the transport path 25.
The second rocking body 86 is bent at a substantially right angle in a side view, and one piece 89 has an L shape shorter than the other piece 90. One piece 89 forms a second contact piece with which the paper P moving in the circumferential direction of the heating roller 22 comes into contact. The other piece 90 forms a second light shielding piece.

  The first oscillating body 85 and the second oscillating body 86 form a cross shape in a side view as a whole in a state where the oscillating member 81 is in the standby posture shown in FIG. More specifically, in the state where the swing member 81 is in the standby posture, the first swing body 85 and the second swing body 86 have the first contact piece 87 and the second light shielding piece 90 extending on the same straight line. The second contact piece 89 and the first light shielding piece 88 extend on a straight line orthogonal to the straight line.

  The swing shaft 84 extends in the left-right direction, passes through the bent portions of the first swing body 85 and the second swing body 86, and is provided to be rotatable relative to the first swing body 85 and the second swing body 86. ing. The base end portion of the swing shaft 83 is held by the frame 21 so as not to rotate. Thus, the first oscillating body 85 and the second oscillating body 86 are supported by the oscillating shaft 84 and are provided so as to be able to oscillate independently with the central axis of the oscillating shaft 84 as the oscillating axis.

The first optical sensor 82 is fixedly disposed at a position that overlaps the front end of the first light shielding piece 88 in a side view with the swinging member 81 in a standby posture. In addition, the second optical sensor 83 is fixedly disposed at a position overlapping the tip of the second light shielding piece 90 in a side view with the swinging member 81 in a standby posture.
The first optical sensor 82 and the second optical sensor 83 have the same structure. That is, the first optical sensor 82 and the second optical sensor 83 include a light emitting unit and a light receiving unit that face in the left-right direction. When the light from the light emitting unit is received by the light receiving unit, an ON signal is output from the light receiving unit. In the state shown in FIG. 9 (the state in which the swinging member 81 is in the standby position), the optical path between the light emitting unit and the light receiving unit is blocked by the first light shielding piece 88 and the second light shielding piece 90. Therefore, an off signal is always transmitted from each light receiving unit. Further, when the first light shielding piece 88 and the second light shielding piece 90 are out of the optical path between the light emitting unit and the light receiving unit, an on signal is output from the light receiving unit.
(2) Oscillating operation of the oscillating member (2-1) Normal time The paper P on which the toner image has been transferred is conveyed backward by the rotation of the heating roller 22 and the pressure roller 23, and is pressed against the heating roller 22. It passes through a nip portion 26 between the roller 23 and the roller 23. At this time, the sheet P is usually peeled from the heating roller 22 in order from the leading end (the leading end in the transport direction). Then, the sheet P is transported rearward along the transport path 25, and the leading end thereof contacts the first contact piece 87 from the front side.

When the paper P further moves, the first contact piece 87 is pushed backward by the paper P as shown in FIG. Accordingly, the first rocking body 85 rotates around the rocking shaft 84 in the direction in which the first contact piece 87 moves upward in the front side (clockwise in FIG. 13).
By the rotation of the swing member 81 (first swing body 85), the swing member 81 takes the first posture shown in FIG. With the swinging member 81 in the first posture, the tip of the first light shielding piece 88 is retracted from a position that blocks the optical path between the light emitting unit and the light receiving unit in the first optical sensor 82. As a result, the output signal of the first optical sensor 82 (light receiving unit) becomes an ON signal, and it is detected that the paper P is in contact with the first contact piece 87. Further, in a state where the swing member 81 is in the first posture, the second swing body 86 maintains the posture where the swing member 81 is in the standby posture shown in FIG.

When the paper P is further transported along the transport path 25 and the paper P is separated from the nip portion 26, the rear end portion of the paper P is in a state along the upper surface of the guide member 27. Then, the swing member 81 is returned to the standby posture by a posture correction member (not shown).
(2-2) Abnormal On the other hand, the sheet P moves in the direction (rotation direction) along the surface of the heating roller 22 together with the surface of the heating roller 22 while the leading end of the sheet P is in contact with the surface of the heating roller 22. Then, the second contact piece 89 is pushed upward by the paper P. Thereby, the second rocking body 86 rotates about the rocking shaft 84 in the direction in which the second contact piece 89 moves upward and moves away from the surface of the heating roller 22 (counterclockwise in FIG. 14). .

  Due to the rotation of the second oscillating body 86, the oscillating member 81 assumes the second posture shown in FIG. In a state where the swing member 81 is in the second posture, the tip portion of the second light shielding piece 90 is retracted from a position that blocks the optical path between the light emitting unit and the light receiving unit in the optical sensor 32. As a result, the output signal of the second optical sensor 83 (light receiving unit) becomes an ON signal, and it is detected that the paper P is in contact with the second contact piece 89. Further, in a state where the swing member 81 is in the second posture, the first swing body 85 maintains the posture where the swing member 81 is in the standby posture shown in FIG.

When it is detected that the paper P is in contact with the second contact piece 89, the operation of each part of the laser printer 1 is stopped. Thereafter, when the paper P that has started to be wound along the surface of the heating roller 22 is removed, the swing member 81 is returned to the standby posture by a posture correction member (not shown).
(3) Operational Effects Even with the configuration described above, the same effects as those of the first embodiment can be obtained.
8). Modifications While the four embodiments of the present invention have been described above, the present invention can also be implemented in other forms.

For example, in each of the above embodiments, the heating roller 22 is illustrated as an example of the heating member, but a film heating heating member may be employed.
The heating member of the film heating method is, for example, disposed in a region surrounded by a pair of film driving rollers opposed in the front-rear direction, an endless belt-shaped heating film wound around the film driving roller, and the heating film. And a heater. The pressure roller is in pressure contact with the lower portion of the heating film from below. When such a film heating type heating member is employed, the second contact pieces 36, 59, 76, 89 in each of the above embodiments are preferably disposed in contact with the surface of the heating film. . Thus, even if the leading edge of the paper P is in close contact with the surface of the heating film, the leading edge of the paper P contacts the second contact pieces 36, 59, 76, 89. 81 can be reliably swung. Therefore, it is possible to reliably detect a state in which the paper P moves in the direction along the surface of the heating film.

Also, as shown in FIG. 3, in the first embodiment, the coil spring 43 is provided between the posture correcting member 41 and the frame 21 in a compressed state. However, as shown in FIG. The spring 43 may be provided between the posture correcting member 41 and the frame 21 in the extended state.
In addition, a monochrome laser printer is illustrated as an example of the image forming apparatus, but the present invention can also be applied to a color printer.

DESCRIPTION OF SYMBOLS 1 Laser printer 22 Heating roller 25 Conveying path 31 Oscillating member 32 Optical sensor 33 Oscillating shaft 35 First contact piece 36 Second contact piece 37 First light shielding piece 38 Second light shielding piece 41 Posture correction member 42 Holding member 43 Coil spring 51 Oscillating member 52 Optical sensor 53 Oscillating shaft 57 First contact piece 58 First light shielding piece 59 Second contact piece 60 Second light shielding piece 71 Oscillating member 72 First optical sensor 73 Second Optical sensor 74 Oscillating shaft 75 First abutting piece 76 Second abutting piece 77 Light-shielding piece 81 Oscillating member 82 First optical sensor 83 Second optical sensor 84 Oscillating shaft 87 First abutting piece 88 First 1 light shielding piece 89 second contact piece 90 second light shielding piece P paper

Claims (5)

The recording sheet carrying the developer image is in contact with the surface, and a portion of the surface that contacts the recording sheet is rotatably provided so as to move in the moving direction of the recording sheet. A heating member for fixing;
A conveyance path through which the recording sheet peeled from the heating member is conveyed;
Swingably provided around the surface and the transport path and parallel to the swing axis of the heating member, and a pivot shaft extending along said pivot axis, a fixed posture correcting member to the rocking axis a swing member which Ru provided with,
A biasing member that biases the posture correcting member from a direction orthogonal to the swing axis;
A holding member that faces the posture correcting member from the downstream side in the biasing direction by the biasing member, receives the posture correcting member, and holds the posture correcting member in a fixed posture;
E Bei a detection member for detecting the swinging of the swinging member,
The detection member is an optical sensor composed of a light emitting element and a pair of light receiving elements that receive light from the light emitting element,
The swing member is
A first abutting piece that abuts a recording sheet conveyed through the conveying path;
A second contact piece that contacts a recording sheet that moves in a direction along the surface of the heating member together with the surface of the heating member;
When the swinging member swings due to the recording sheet coming into contact with the first contact piece, it swings to a position deviating from the optical path between the light emitting element and the light receiving element and a position blocking the optical path. A moving first light shielding piece;
A second light-blocking piece that swings to a position that is out of the optical path and a position that blocks the optical path when the swinging member swings due to the recording sheet coming into contact with the second contact piece;
With
The first contact piece, the second contact piece, the first light shielding piece, the second light shielding piece, and the posture correcting member are integrally formed,
The image forming apparatus, wherein the first light-shielding piece and the second light-shielding piece are formed in different shapes so that different detection signals are output from the optical sensor when each of the first light-shielding piece and the second light-shielding piece swings . The image forming apparatus according to claim 1, wherein the second contact piece is in contact with a surface of the heating member. Said second contact piece, when the second recording sheet to the contact piece the swing member swings by abutment, moves away from the heating element, according to claim 1 or 2 Image forming apparatus. The heating member has a cylindrical surface, which is a heating roller heater is incorporated, the image forming apparatus according to any one of claims 1-3. The heating member is
A film wound in a tubular shape,
The image forming apparatus according to any one of claims 1 to 3, further comprising a heater disposed in a region surrounded by the film.

Images