JP4154657B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrophotographic image forming apparatus.
[0002]
[Prior art]
As this type of image forming apparatus, an image forming apparatus having a fixing device composed of a pair of rotating bodies pressed against each other is well known. The sheet is conveyed between the rotating bodies, and the toner on the sheet is fixed to the sheet by heat and pressure. In such a fixing device, since the sheet is nipped and conveyed by two rotating bodies, the sheet may be wound around, for example, one rotating body. For this reason, a separation claw that contacts the rotating body is provided on the downstream side of the fixing device, and the sheet to be wound around the heat roll is separated by the separation claw.
[0003]
However, the peeling nails alone may not be sufficient from a safety standpoint. For this reason, conventionally, a light reflection type sensor is provided on the rotating body, and it is determined whether or not the sheet is wound based on the density of light reflected from the rotating body when the sheet is wound and when the sheet is not wound. One is known (Patent Document 1).
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 7-311511
[Problems to be solved by the invention]
However, in the above-described conventional example, since the sheet after the sheet is wound around the rotating body is detected, only post-processing can be handled, and there may be cases where the safety is insufficient.
[0006]
SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus that can quickly detect a sheet jam in the fixing device and can quickly cope with the sheet jam in an image forming apparatus having a fixing device composed of a pair of rotating bodies. There is.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the first feature of the present invention is that a fixing device having a pair of opposed rotating bodies, a conveying path for conveying a sheet between the rotating bodies of the fixing apparatus, and the conveying path And a sheet detecting means for detecting the sheet disposed on the downstream side of the fixing apparatus , wherein the sheet detecting means is an actuator that contacts and displaces the sheet; A detection unit that detects the displacement of the actuator, and the actuator has a shielding unit that shields radiant heat from the fixing device, and the shielding unit extends in a rotation axis direction of the actuator, and together with the actuator It is in a rotating image forming apparatus. Since the sheet detecting means is located in the conveyance path on the downstream side of the fixing device and opposed to the fixing device, when the sheet tries to wind around the rotating body, the sheet detecting means detects no sheet, and the sheet in the fixing device Jam can be detected. Further, by separating the sheet detection means into the actuator and the detection unit, the detection unit can be less affected by the heat from the fixing device.
[0009]
Further, in order for the detection unit to reduce the influence of heat from the fixing device, it is preferable to dispose the detection unit at a position farther from the rotating body than the sheet contact portion of the actuator.
[0010]
Moreover, it is preferable to provide a cooling means for cooling the detection unit. The cooling means can be constituted by a cooling fan provided in the image forming apparatus. This cooling fan does not need to be dedicated to the detection unit, and can also serve as a cooling unit for the power supply device, the process cartridge, the sheet, etc. In this case, an air flow path that guides air to the detection unit is configured. This is enough. By providing the cooling means in this way, the temperature of the detection unit can be kept low, and malfunction due to temperature rise can be prevented. Further, a heat insulating material that thermally blocks between the detection unit and the fixing device may be provided, or a heat radiating plate may be provided in the detection unit.
[0011]
The rotating body of the fixing device includes, for example, a heat roll and a pressure roll with a built-in heater, but is not necessarily a roll and can be appropriately replaced with a belt type. In addition, a heater may be incorporated in both rotating bodies, and a ceramic heater formed near the surface of the rotating body may be used as the heater.
[0012]
The second feature of the present invention is that a fixing device having a pair of opposed rotating members, a conveyance path for conveying a sheet between the rotating members of the fixing device, and a sheet on the downstream side of the fixing device. An actuator that has a peeling claw that peels from the rotating body, and a sheet detection unit that is disposed in the conveyance path in the vicinity of the peeling claw and detects the sheet , and the sheet detection unit abuts on the sheet and is displaced. And a detection unit that detects the displacement of the actuator, wherein the actuator has a shielding unit that shields radiant heat from the fixing device, and the shielding unit extends in a rotation axis direction of the actuator, The image forming apparatus rotates together with the actuator . Therefore, since the posture of the sheet is stable in the vicinity of the peeling claw, variation in the detection position of the sheet can be reduced and the sheet can be detected stably.
[0013]
A third feature of the present invention is that a fixing device having a pair of opposed rotating bodies, a conveying unit that conveys a sheet toward the fixing device, and a downstream of the fixing device in the conveying path. A sheet detection unit that is disposed opposite to the fixing device and detects the sheet, and a determination unit that determines whether the sheet conveyed by the conveyance unit is detected by the sheet detection unit within a predetermined time when the determination result of the determining means, when the sheet is determined not to be transported within a predetermined time, and control means for interrupting the power supply to at least the fixing device, the sheet detecting means, the sheet And an actuator that detects displacement of the actuator, and the actuator has a shielding portion that shields radiant heat from the fixing device. The shielding portion is spread in the rotation axis direction of the actuator, in the image forming apparatus which rotates together with the actuator. Therefore, when it is determined that the sheet is not conveyed within a predetermined time, at least the power supply to the fixing device is cut off, so that the power is cut off immediately when the sheet is wound around the rotating body to ensure safety. It is something that can be done.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
In FIG. 1, a first embodiment of the present invention is shown. The fixing device 36 includes a pair of rotating bodies, for example, a heat roll 90 including a heater 96 and a pressure roll 92, and the heat roll 90 and the pressure roll 92 rotate in contact with each other. The sheet S to which the toner has been transferred passes between the heat roll 90 and the pressure roll 92 and is nipped by the nip portion 94, and the toner on the sheet S is fixed to the sheet S.
[0015]
The sheet detection device 106 includes an actuator 108 and a detection unit 110. The actuator 108 is disposed on the downstream side of the fixing device 36 and is configured, for example, by connecting a sheet contact portion 112 and a detected portion 116. The sheet abutting portion 112 is rotatably supported via a rotating shaft 114, and the leading end portion of the sheet abutting portion 112 faces the conveyance path 32, near the other end of the sheet abutting portion 112. It is connected to the detected part 116.
[0016]
The detection unit 110 is composed of, for example, a photo interrupter, and detects the displacement of the detection unit 116 of the actuator 108. That is, when there is an actuator at the position indicated by the solid line in the figure, light transmission and reception between the light emitting element and the light receiving element is blocked, and when the actuator 108 is displaced to the position indicated by the two-dot chain line in the figure, the light emitting element When the light receiving element receives the light, the displacement of the actuator 108 is detected.
[0017]
When the sheet S passes through the nip portion 94 of the fixing device 36, the leading edge of the sheet S comes into contact with the vicinity of the leading edge of the sheet contact portion 112 of the actuator 108, so that the sheet contact portion 112 is counteracted around the rotation shaft 114. Rotated clockwise, the detected portion 116 is displaced downward to be detached from the detecting portion 110, and it is detected that the leading edge of the sheet S has passed through the fixing device 36. On the other hand, when a jam occurs, such as when the sheet S is wound around the heat roll 90, the position of the actuator 108 remains the same even if a predetermined time has elapsed after the sheet S passes a predetermined point, and a jam has occurred. Judge that. According to this embodiment, by separating the sheet detection device 106 into the actuator 108 and the detection unit 110, the detection unit 110 can be separated from the heat roll 90, and malfunctions due to the heat of the heat roll 90 are prevented. Can be prevented.
[0018]
In FIG. 2, a second embodiment of the present invention is shown. In the second embodiment, when compared with the first embodiment described above, the actuator 108 in the first embodiment separates the sheet contact portion 112 and the detected portion 116 from each other. In the second embodiment, the sheet contact portion 112 and the detected portion 116 are integrated. In addition, the image forming apparatus is provided with a blower fan 72 and a vent hole 34, and an air flow passing through the detection unit 110 is formed by the blower fan 72 and the vent hole 34. A cooling means for cooling 110 is configured. The detection unit 110 may malfunction when the temperature rises, and the malfunction is prevented by cooling the detection unit 110.
[0019]
Also in the second embodiment, when the sheet S passes through the nip portion 94 of the fixing device as in the first embodiment, the leading edge of the sheet S abuts on the sheet abutting portion 112 of the actuator 108, thereby detecting the object to be detected. The unit 116 is displaced downward to be detached from the detection unit 110 and detects that the leading edge of the sheet S has passed through the fixing device 36. On the other hand, when a jam occurs, such as when the sheet S is wound around the heat roll 90, the position of the actuator 108 remains the same even if a predetermined time has elapsed after the sheet S passes a predetermined point, and a jam has occurred. It can be judged as a thing.
[0020]
【Example】
Next, an embodiment in which the present invention is applied to an actual image forming apparatus will be described.
In FIG. 3, the image forming apparatus 10 includes an image forming apparatus main body 12, an image forming unit 14 is mounted in the image forming apparatus main body 12, and a discharge unit 16 described later is provided above the image forming apparatus main body 12. For example, two-stage sheet feeding units 18 a and 18 b are disposed below the image forming apparatus main body 12. Further, below the image forming apparatus main body 12, two-stage sheet feeding units 18c and 18d that are detachably mounted as options are arranged.
[0021]
Each of the paper feeding units 18a to 18d has a paper feeding unit main body 20 and a paper feeding cassette 22 in which sheets are stored. The paper feed cassette 22 is slidably attached to the paper feed unit main body 20, and is pulled out in the front direction (right direction in FIG. 3). In addition, a nudger roll 24 is disposed in the upper portion near the back end of the paper feed cassette 22, and a retard roll 26 and a feed roll 28 are disposed in front of the nudger roll 24. Further, the optional paper feed units 18c and 18d are provided with a pair of feed rolls 30 respectively.
[0022]
The conveyance path 32 is a sheet path from the nudger roll 24 to the discharge port 34 of the lowermost sheet feeding unit 18d, and this conveyance path 32 is near the back surface (left side surface in FIG. 3) of the image forming apparatus main body 12. In addition, it has a portion that is formed substantially vertically from the feed roll 30 of the lowermost paper feed unit 18d to the fixing device 36 described later. A transfer device 42 and an image carrier 44 described later are disposed on the upstream side of the fixing device 36 in the conveyance path 32, and a resist roll 38 is disposed on the upstream side of the transfer device 42 and the image carrier 44. Further, a discharge roll 40 is disposed in the vicinity of the discharge port 34 of the conveyance path 32.
[0023]
Therefore, the sheet fed from the sheet feeding cassette 22 of the sheet feeding unit 18 a to 18 d by the nudger roll 24 is rolled by the retard roll 26 and the feed roll 28 and guided to the conveyance path 32, and is temporarily stopped by the registration roll 38. The developer image is transferred between a transfer device 42 and an image carrier 44, which will be described later, at timing, and the transferred toner image is fixed by the fixing device 36, and is discharged from the discharge port 34 by the discharge roll 40. It is discharged to the discharge unit 16.
[0024]
However, in the case of duplex printing, it is returned to the reverse path. That is, the front side of the discharge roll 40 in the transport path 30 is divided into two forks, and a switching claw 46 is provided at the divided portion, and a reverse path 48 is formed from the divided portion to the registration roll 38. The reversing path 48 is provided with transport rolls 50a to 50c. In the case of double-sided printing, the switching claw 46 is switched to the side that opens the reversing path 48, and the discharge roll 40 is in front of the rear end of the recording medium. At this time, the discharge roll 40 is reversed, the recording medium is guided to the reverse path 48, and is discharged from the discharge port 34 to the discharge unit 16 through the registration roll 38, the transfer device 42, the image carrier 44 and the fixing device 36. It is.
[0025]
The discharge unit 16 includes an inclined part 52 that is rotatable with respect to the image forming apparatus main body. The inclined portion 52 has a low discharge port portion and is inclined so as to gradually increase toward the front direction (the right direction in FIG. 1). The inclined portion 52 is supported by the image forming apparatus main body 12 so as to be rotatable around the lower end. As shown by a two-dot chain line in FIG. 3, when the inclined portion 52 is rotated upward and opened, an opening portion 54 is formed, and a process cartridge 66 (to be described later) can be attached and detached through the opening portion 54. .
[0026]
The image forming unit 14 is of, for example, an electrophotographic system, and is charged by the image carrier 44 made of a photosensitive member, a charging device 56 made of, for example, a charging roll that uniformly charges the image carrier 44, and the charging device 56. An optical writing device 58 that writes a latent image on the image carrier 44 with light, a developing device 60 that visualizes the latent image of the image carrier 44 formed by the optical writing device 58 with toner, and the developing device 60 A transfer device 42 composed of, for example, a transfer roll for transferring a toner image onto a sheet, a cleaning device 62 composed of, for example, a blade for cleaning toner remaining on the image carrier 44, and a toner image on a sheet transferred by the transfer device 42 And a fixing device 36 for fixing the sheet. The optical writing device 58 is composed of, for example, a scanning type laser exposure device, and is arranged in the vicinity of the front surface of the image forming apparatus main body 12 in parallel with the paper feeding units 18a to 18d described above. The developing device 60 includes a developing roll 64 that conveys toner to the image carrier 44.
[0027]
The process cartridge 66 is obtained by integrating the image carrier 44, the charging device 54, the developing device 60, and the cleaning device 60. The process cartridge 66 is disposed immediately below the inclined portion 52 of the discharge portion 16 and is attached / detached via the opening portion 54 formed when the inclined portion 52 is opened as described above. A shielding plate 68 is provided between the process cartridge 66 and the fixing device 36 so as to block radiant heat from the fixing device 36 to the process cartridge 66.
[0028]
The first blower fan 70 is for intake air and is disposed obliquely above the optical writing device 58 described above. Further, the second blower fan 72 is for exhaust, and is disposed in the vicinity of the reverse path 48 on the back side of the image forming apparatus main body 12. An intake duct 74 is provided on the upstream side of the first blower fan 70 so as to take in air from an intake hole (not shown) formed in the side surface of the image forming apparatus main body 12. A power supply device 76 that supplies power to each part of the image forming apparatus is disposed in the vicinity of the air intake hole, and the power supply device 76 and the optical writing device 58 are cooled by the air sucked from the air intake hole. . An air guide 78 is provided on the downstream side of the first blower fan 70, and the air guide 78 directs air toward the inner surface of the inclined portion 52. A large number of ribs 80 are formed on the inner surface of the inclined portion 52 so as to guide air between the inclined portion 52 and the process cartridge 66. Further, the shield plate 68 is provided with a vent hole 82 and a lattice-like sheet guide 84 provided between the transfer device 42 and the fixing device 36. The air is sucked into the second blower fan 72 through the sheet guide 84 and is exhausted from the exhaust hole 86 formed in the image forming apparatus main body 12. Further, the discharge port 34 described above also serves as a ventilation hole, and the air sucked from the discharge port 34 is guided to a detection unit of a fixing device 36 described later to cool the detection unit.
[0029]
4 and 5, details of the fixing device 36 are shown. In the fixing device 36, a heat roll 90 and a pressure roll 92, which are a pair of rotating bodies, are disposed in the fixing device main body 88, and the heat roll 90 and the pressure roll 92 rotate in pressure contact with each other at the nip portion 94. A heater 96 made of a lamp is disposed in the heat roll 90 to heat the heat roll 90. The above-described conveyance path 32 is configured in the vertical direction across the nip portion 94, and the sheet is conveyed from the bottom to the top. An inlet chute 98 is disposed upstream of the nip portion 94, and outlet chutes 100 a and 100 b are disposed downstream of the nip portion 92. The outlet chutes 100a and 100b are alternately formed on the heat roll 90 side and the pressure roll 92 side, and the outlet chutes 100a on the pressure roll 92 side rotate upward to allow the sheet to pass therethrough. Yes.
[0030]
A thermostat 102 is in contact with the heat roll 90, and the surface temperature of the heat roll 90 is detected by the thermostat 102. Further, a separation claw 104 is provided in the vicinity of the downstream side of the nip portion 94, and this separation claw 104 is urged toward the heat roll 90 with a weak force that does not damage the surface of the heat roll 90, The tip of the peeling claw 104 is in pressure contact with the surface of the heat roll 90, and the sheet to be wound around the heat roll 90 is peeled off. The peeling claws 104 are arranged on both sides in the vicinity of a sheet detection device 106 described later.
[0031]
The sheet detection device 106 is disposed in the vicinity of the downstream side of the nip portion 94. The sheet detection device 106 includes an actuator 108 and a detection unit 110.
[0032]
As shown in FIGS. 6 and 7, the actuator 108 includes a sheet contact portion 112 that is positioned substantially at the center and extends obliquely, a rotating shaft 114 to which the sheet contact portion 112 is fixed, and a sheet contact portion. A detected portion 116 extending rearward from the portion 112 and shielding portions 118a and 118b extending left and right from the sheet contact portion 112. The sheet contact portion 112 is disposed at substantially the same position as the outlet side chutes 100a and 100b. The rotating shaft 114 is supported by bearings 120a and 120b provided on the outlet side chute 100b so as to be rotatable on both sides of the rotating shaft 114. In addition, an elastic member 122 is provided at one end of the rotation shaft 114 with the fixing device main body 88, and the sheet abutting portion 112 urges the actuator 108 so as to close the conveyance path 32. . Further, a stopper 124 is provided on the rotating shaft 114, and the sheet contact portion 112 is positioned by the stopper 124. The shielding portions 118 a and 118 b are interposed between the heat roll 90 and the detection unit 110 and block radiant heat from the heat roll 90 to the detection unit 110.
[0033]
The detection unit 110 includes a photo interrupter provided in the fixing device main body 88. The detection unit 116 of the actuator 108 is disposed between the light emitting element and the light receiving element, and detects the displacement of the actuator 108. In the fixing device main body 88, openings 126a and 126b are formed above and below the detection unit 110 so that the above-described airflow is guided to the detection unit 110.
[0034]
Therefore, the sheet guided to the inlet side chute 98 and entering the nip portion 94 passes under the pressure and heat in the nip portion 94, and at the moment when the leading end of the sheet tries to hit the outlet side chutes 100a and 100b. The actuator 108 abuts against the sheet abutting portion 112 of the actuator 108, the actuator 108 rotates about the rotation shaft 114 against the elastic member 122, and the detected portion 116 is detached from the detecting portion 110. When the light receiving element receives the light from, it is detected that the leading edge of the sheet has passed. On the other hand, when the sheet is wound around the heat roll 90 and is not peeled off by the peeling claw 104, the leading edge of the sheet does not come into contact with the sheet contact portion 112 within a predetermined time, and the actuator 108 is not displaced and is detected. When the light from the light emitting element of the unit 110 is blocked by the detected part 116 of the actuator 108 and does not reach the light receiving element, it is determined as a sheet jam.
[0035]
FIG. 8 shows a part of the control circuit in the image forming apparatus. Various signals including the on / off signal from the detection unit 110 described above are input to the main control circuit 128. The main control circuit 128 generates a control signal from an input signal and controls each part of the image forming apparatus, and includes a power control circuit 130 and a resist roll drive motor 132. The power supply control circuit 130 controls the above-described power supply device 76 to control the power supply to each part including the heater 96 of the heat roll 90.
[0036]
FIG. 9 shows a control flow relating to sheet detection in the main control circuit 128. First, in step S10, the registration roll is driven at a predetermined timing, and the counter or timer is operated when the registration roll is started. In the next step S12, it is determined whether or not a predetermined time has elapsed since the start of driving the registration roll. If it is determined in step S12 that the predetermined time has not elapsed, the process proceeds to the next step S14, where it is detected whether or not the detection unit has detected a sheet. If no sheet is detected, the process returns to step S12 and predetermined The detection of the sheet by the detection unit within the time is monitored. If a sheet is detected in step S14, the leading edge of the sheet has passed through the fixing device within a predetermined time, so that the process ends as normal. On the other hand, if it is determined in step S12 that the predetermined time has elapsed, the leading edge of the sheet has not passed through the fixing device even after the predetermined time has elapsed, and thus a sheet jam such as the sheet winding around the heat roll occurs. As a result, a power cut-off signal is sent to the power control circuit 130 to cut off the power supply from the power supply device 76. As a result, the power supply including the heater of the heat roll is cut off, so that safety can be ensured.
[0037]
In the above embodiment, the rotation start point of the registration roll is set as the sheet detection start point. However, the present invention is not limited to this. As another embodiment, a sheet detection device is further provided upstream of the fixing device. The sheet detection by the sheet detection apparatus may be used as a starting point.
[0038]
【The invention's effect】
As described above, according to the present invention, the sheet detection unit disposed opposite to the fixing device detects the sheet passing through the fixing device, so that the sheet jam in the fixing device can be detected quickly, Safety can be ensured.
[Brief description of the drawings]
FIG. 1 is a side view showing a fixing device and its peripheral portion in a first embodiment of the present invention.
FIG. 2 is a side view showing a fixing device and its peripheral portion in a second embodiment of the present invention.
FIG. 3 is a side view showing an image forming apparatus according to an embodiment of the present invention.
FIG. 4 is a cross-sectional view showing a fixing device unit used in an image forming apparatus according to an embodiment of the present invention.
FIG. 5 is a perspective view illustrating a main part of a fixing device unit used in the image forming apparatus according to the exemplary embodiment of the present invention.
FIG. 6 is a perspective view showing the actuator of the sheet detection apparatus used in the image forming apparatus according to the embodiment of the present invention as seen from the back side.
FIG. 7 is a front view showing an actuator of the sheet detection apparatus used in the image forming apparatus according to the embodiment of the present invention.
FIG. 8 is a circuit diagram illustrating a control circuit of the image forming apparatus according to the embodiment of the present invention.
FIG. 9 is a flowchart showing a control flow related to sheet detection in the main control circuit of 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 14 Image forming means 32 Conveyance path 34 Discharge port (ventilation hole)
36 fixing device 38 resist roll 70 first blower fan 72 second blower fan 90 heat roll 92 pressure roll 106 sheet detection device 108 actuator 110 detection unit 112 sheet contact portion 114 rotating shaft 116 detected portion

Claims (5)

A fixing device having a pair of opposed rotating bodies;
A conveyance path for conveying a sheet between the rotating bodies of the fixing device;
A sheet detecting unit disposed on the downstream side of the fixing device so as to face the fixing device and detecting the sheet ;
The sheet detection means includes an actuator that contacts and displaces the sheet, and a detection unit that detects the displacement of the actuator,
The actuator has a shielding part that shields radiant heat from the fixing device,
The shielding unit is an image forming apparatus that extends in a rotation axis direction of the actuator and rotates together with the actuator . The detection unit, an image forming apparatus according to claim 1, wherein the seat abutment portion of the actuator are arranged in a position away from the rotor. The detecting portion image forming apparatus in accordance with claim 1 or 2 cooling means is provided for cooling the. A fixing device having a pair of opposed rotating bodies;
A conveyance path for conveying a sheet between the rotating bodies of the fixing device;
A peeling claw for peeling the sheet from the rotating body on the downstream side of the fixing device;
A sheet detecting unit disposed in the conveyance path in the vicinity of the peeling claw and detecting the sheet ;
The sheet detection means includes an actuator that contacts and displaces the sheet, and a detection unit that detects the displacement of the actuator,
The actuator has a shielding part that shields radiant heat from the fixing device,
The shielding unit is an image forming apparatus that extends in a rotation axis direction of the actuator and rotates together with the actuator . A fixing device having a pair of opposed rotating bodies;
Conveying means for conveying the sheet toward the fixing device;
A sheet detecting unit disposed on the downstream side of the fixing device and facing the fixing device in the conveyance path, and detecting the sheet;
Determining means for determining whether or not the sheet conveyed by the conveying means has been detected by the sheet detecting means within a predetermined time;
A control unit that cuts off power supply to at least the fixing device when it is determined that the sheet is not conveyed within a predetermined time as a result of the determination by the determination unit ;
The sheet detection means includes an actuator that contacts and displaces the sheet, and a detection unit that detects the displacement of the actuator,
The actuator has a shielding part that shields radiant heat from the fixing device,
The shielding unit is an image forming apparatus that extends in a rotation axis direction of the actuator and rotates together with the actuator .

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