JP2003323068A - Sheet wrap detection means and fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet wrap detection means which accurately detects a wrap jam without disturbing an unfixed toner image, and a fixing device. <P>SOLUTION: The sheet wrap detection means has: a first sensor 220 which is movably disposed upstream and near a fixing roller 221 in the direction in which a recording sheet P is transported, and detects the presence or absence of the recording sheet P; and a moving means 306 which moves the first sensor 220 or a part 301 of the first sensor, thereby bringing it near a recording sheet transport path Q or separating it therefrom. The sheet warp detection means detects a wrap jam which is caused by the recording sheet P remaining unseparated from the fixing roller 221 or a pressure roller 223. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a fixing roller having a heating means inside and a pressure roller, and passes a recording sheet having toner on the surface between a rotating fixing roller and pressure roller. Thus, the present invention relates to a sheet winding detection unit and a fixing device that are used in a fixing mechanism such as a fixing device that fixes toner on a recording sheet and that detects that the recording sheet is wound around a fixing roller or a pressure roller.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine or a printer, in order to fix a toner image on a recording sheet,
It is well known to use a fixing device having a fixing roller having a heating means inside and a pressure roller.

In this fixing device, the fixing roller is in contact with the toner bearing surface of the recording sheet, and the pressure roller is in contact with the rear surface thereof.

The fixing roller, or both the fixing roller and the pressure roller, has a heating means inside, and the toner is fixed on the recording sheet by the heat of the heating means and the pressure between both rollers.

One of the problems to be solved in the fixing device having such a structure is a phenomenon that the recording sheet is wound around the fixing roller or the pressure roller (hereinafter referred to as a winding jam).

In other words, the recording sheet exiting between the fixing roller and the pressure roller may be wound without being separated from the fixing roller or the pressure roller to cause a jam.

In order to prevent the winding jam, a separating claw is usually arranged near the fixing roller.

The structure will be described with reference to FIG.

FIG. 11 is a diagram showing a conventional fixing device.

1101 is a fixing roller, 1102 is a pressure roller, 1103 and 1104 are heaters as heating means,
Reference numeral 1105 is a separation claw, and P is a recording sheet.

As shown in FIG. 11, the fixing roller 1101
Separation claw 1105 is arranged in the vicinity.

The fixing roller 1101 is heated by the heater 1103.

The recording sheet P passes between the fixing roller 1101 and the pressure roller 1102.

The pressure roller 1102 is usually made of a softer material than the fixing roller 1101.
If the separation claw is arranged on the second side, the surface of the 1102 is damaged by the separation claw, and thus the separation claw cannot be placed on the 1102 side in many cases.

Therefore, the winding jam cannot be completely prevented.

The wrapping jam makes it difficult for the user who is trying to remove the jamming recording sheet to see the jammed recording sheet. Further, if the fixing device is driven without noticing the wrapping jam, the wrapping is advanced, An excessive load may be applied to the motor that drives the roller.

For this reason, there has been a demand for a means for detecting the wrapped jam separately from other jams (record sheet retention).

Conventionally, as a means for detecting a winding jam, a reflection type photo sensor is arranged in the vicinity of a fixing roller or a pressure roller to detect the presence or absence of a recording sheet stuck to a fixing device, or a conductive method. A method has been adopted in which the presence or absence of the recording sheet is determined by intermittently contacting and separating the elastic member with the pressure roller to detect the voltage.

[0019]

However, in the method using the reflection type photosensor, the heat of the fixing roller changes the characteristics of the photosensor and it is difficult to set the threshold value.

Further, there is a problem that the life of the photo sensor is shortened by heat.

Further, in the method of detecting the voltage by separating the conductive member from the pressure roller and detecting the voltage, toner and paper dust (caused by the recording sheet) adhere to the pressure roller due to long-term use of the fixing device. Since it becomes an electrical resistance, there is a problem that the presence or absence of a winding jam is erroneously detected.

Further, contact type sensors such as a photo sensor with a flag are arranged before and after the entrance of the fixing roller to detect the presence or absence of the conveyed recording sheet, and the recording sheet passes through the sensor on the inlet side. Then, there is also proposed a method of determining a jammed jam when it does not pass through the sensor on the exit side, but with this method, the unfixed toner is scattered by the impact of the sensor flag on the entrance side hitting the recording sheet. There was a problem and it could not be realized on high-speed machines.

The present invention has been made in view of the above problems, and an object of the present invention is to detect sheet wrapping which can accurately detect a wrapping jam without disturbing a toner image before fixing. Means and fixing device.

[0024]

Therefore, in the present invention, the above object is achieved by providing a sheet wrapping detecting means or a fixing device shown in any one of the following items (1) to (9). Is what you are trying to do.

(1) A fixing roller rotatably arranged to convey a recording sheet, a pressure roller paired with the fixing roller and abutting against the back surface of the recording sheet, the fixing roller or the pressing roller. A heating means for heating the pressure roller or both the fixing roller and the pressure roller;
A sheet winding detection means of a fixing mechanism for fixing the toner image on the recording sheet by passing a recording sheet carrying a toner image on the surface between the fixing roller and the pressure roller. A first sensor that is movably disposed near the upstream side of the recording sheet conveyance direction and detects the presence or absence of the recording sheet, and the first sensor or a part of the first sensor is moved to convey the recording sheet. A sheet wrapping detection unit that detects a wrapping jam that occurs when the recording sheet is not separated from the fixing roller or the pressure roller, the sheet wrapping detection unit having a moving unit that moves closer to and away from the path.

(2) Further, a second sensor disposed near the downstream side of the fixing roller in the recording sheet conveying direction and for detecting the presence or absence of the recording sheet, and a second sensor further arranged upstream of the first sensor in the conveying direction. A third sensor provided to detect the presence / absence of a recording sheet, and the fixing is performed when the recording sheet does not pass the second sensor at an expected timing after passing the third sensor. The sheet wrapping detection means according to (1) above, characterized in that the roller and the pressure roller are stopped.

(3) The first sensor or a part of the first sensor is close to the conveyance path of the recording sheet on a predetermined occasion, and is usually separated from the conveyance path of the recording sheet. The sheet wrapping detection means according to (1) or (2) above.

(4) The predetermined opportunity is when the power of the apparatus main body is turned on, when the printer recognizes a jam, or after the operation of the apparatus is temporarily stopped and then restored. The sheet wrap detection unit according to the item (3).

(5) Before the first sensor or a part of the first sensor is brought close to the conveyance path of the recording sheet before the fixing roller, the fixing roller and the pressure roller are reversely rotated for a predetermined time. The sheet wrapping detection means according to item (1) or (2) above.

(6) Further, there is provided a sensor for detecting the size of the recording sheet, and the predetermined time is determined according to the size of the recording sheet detected by the sensor. 5) A sheet wrapping detection means described in the item 5).

(7) A sheet winding detecting means according to the above (1), characterized in that a solenoid coil or a motor is used as a moving means for moving the first sensor or a part of the first sensor. .

(8) A fixing device comprising the sheet wrap detection means according to any one of the items (1) to (7).

(9) The fixing device as described in the above item (8), wherein the fixing roller and the pressure roller are reversely rotated when a winding jam is detected.

The details will be described below.

According to the present invention, the first sensor is movably disposed near the upstream side of the fixing roller in the recording sheet conveying direction and detects the presence or absence of the recording sheet, and the first sensor is moved to convey the recording sheet. A means to approach and separate from the route,
By arranging the first sensor close to the recording sheet conveying path in front of the fixing roller, the recording sheet is fed from the fixing roller or the pressure roller without searching the surfaces of the fixing roller and the pressure roller. Detects jammed jams that occur without being separated.

An object of the present invention is to detect that the recording sheet is wound around the fixing roller or the pressure roller, and the recording sheet is disposed near the downstream side of the fixing roller in the recording sheet conveying direction. The recording sheet includes a second sensor that detects passage of a sheet and a third sensor that is disposed further upstream in the transport direction than the first sensor and that detects passage of a recording sheet. When the second sensor is not passed at the expected timing after passing the third sensor, the fixing roller and the pressure roller are stopped so that the entire surface of the recording sheet normally becomes the fixing roller and the pressure roller. It does not wrap around, and a part of the recording sheet remains before the entrance of the fixing roller.

By detecting the remaining portion with the first sensor, the winding jam is detected.

Further, since the first sensor is close to the recording sheet conveying path at a predetermined opportunity and is usually separated from the recording sheet conveying path, the problem that the toner image before fixing is disturbed by the sensor flag is avoided. it can.

[0039]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be specifically described below with reference to the accompanying drawings with reference to a plurality of examples.

In the drawings, the same reference numerals indicate the same structures.

(Embodiment 1) First, Embodiment 1 will be described with reference to FIGS.

FIG. 1 is a general view of the image forming apparatus in the first embodiment, FIG. 2 is a view of the sensor used in the first embodiment, and FIG.
4A and 4B are explanatory views of the behavior of the sensor in Embodiment 1, and FIG. 4 is a flowchart of Embodiment 1.

First, an image forming apparatus using the fixing device according to the present invention will be described.

In FIG. 1, 201 is an electrophotographic laser beam printer which is an image forming apparatus using the fixing device according to the present invention.

Reference numeral 202 is a deck, 203 is a deck sheet presence sensor, 204 is a sheet size detection sensor which is a sensor for detecting the size of a recording sheet, 205 is a pickup roller, 206 is a deck feeding roller, 207 is a retard roller, 208 is a feeding sensor, 209 is a feeding / conveying roller, 210 is a pair of registration rollers, 211 is a pre-registration sensor which is a third sensor, 212 is a laser scanner unit,
213 is a process cartridge, 214 is a photosensitive drum, 215 is a charging roller, 216 is a developing device, 217 is a transfer roller, 218 is a conveyance guide, 219 is a fixing device, and 2 is a fixing device.
20 is a sensor before the fixing roller which is the first sensor.

221 is a fixing roller, 222 is a first halogen heater which is a heating means, 223 is a pressure roller, and 2 is a pressure roller.
24 is a second halogen heater, which is a heating means, and 225.
Is a second sensor, which is a fixing discharge sensor, 226 is a discharge sensor, 227 is a discharge roller pair, 228 is a laser unit, 229 is a polygon mirror, 230 is a scanner motor, 231 is an imaging lens group, 232 is a folding mirror,
233 is a printer control unit, 234 is a main motor, and 23
Reference numeral 5 is a display panel, 236 is an external device, and P is a recording sheet.

The laser beam printer 201 has a deck 202 for accommodating the recording sheets P, a deck sheet presence sensor 203 for detecting the presence or absence of the recording sheet P in the deck 202, and a size of the recording sheet P in the deck 202. A sheet size detection sensor 204 for detecting, a pickup roller 205 for feeding the recording sheet P from the deck 202, and a deck feeding roller 20 for conveying the recording sheet P fed by the pickup roller 205.
6. A retard roller 207 is provided which is paired with the deck feeding roller 206 and prevents double feeding of the recording sheets P.

A feeding sensor 208 for detecting a feeding / conveying state is provided on the downstream side of the deck feeding roller 206 in the sheet conveying direction (hereinafter, simply referred to as “downstream”), and for conveying the recording sheet P further downstream. A feed / conveyance roller 209, a registration roller pair 210 that conveys the recording sheet P in synchronism with the image forming operation, and a pre-registration sensor 211 that detects the conveyance state of the recording sheet P to the registration roller pair 210 are provided. .

Further, downstream of the registration roller pair 210, a process cartridge 213 constituting an image forming means for forming a toner image on the photosensitive drum 214 based on a laser beam from a laser scanner section 212 described later is provided in the apparatus main body. It is removably attached to.

The process cartridge 213 includes a rotatable photosensitive drum 214 and a charging roller 2 around the photosensitive drum 214.
15 and a developing device 216, and a cleaning device (not shown) are provided. During image formation, the surface of the photosensitive drum 214 is uniformly charged by the charging roller 215, and selective exposure is performed from the laser scanner unit 212. By forming the latent image, the latent image is formed on the developing unit 216.
To develop the toner into a visible image.

Then, by applying a transfer bias voltage to the transfer roller 217, the toner image is transferred to the conveyed recording sheet P to form an image.

A transport guide 2 is provided downstream of the transfer roller 217.
A fixing device 219 for thermally fixing the toner image transferred onto the recording sheet P is provided.

The fixing device 219 includes a fixing roller 221 including a first halogen heater 222, a pressure roller 223 including a second halogen heater 224, and a fixing roller front detecting a conveyance state to the fixing roller 221. Sensor 2
20 and a fixing discharge sensor 225 that detects a conveyance state from the fixing roller 221.

The fixing device 219 is provided with the sheet winding detecting means according to the present invention, and is a characteristic mechanism of the present invention. Therefore, its configuration will be described later with reference to FIGS. 2 and 3.

Further downstream, a discharge sensor 226 for detecting the state of sheet conveyance in the discharge portion and a discharge roller pair 227 for discharging the recording sheet P are arranged.

The laser scanner section 212 emits a laser beam modulated based on an image signal sent from an external device 236, which will be described later.
8. A polygon mirror 229 for scanning the laser beam from the laser unit 228 onto the photosensitive drum 214, a scanner motor 230, an imaging lens group 231, and a folding mirror 232.

The printer control unit 233 controls the laser printer 201, and although not shown in the figure, an MPU (microcomputer) equipped with a RAM, a ROM, a timer, a digital input / output port, and various input / outputs. It is composed of a control circuit and the like.

The printer control section 233 has sensors 203, 204, 208, 211, 2 for the recording sheet P of each section.
Wired with 20, 225, 226, each sensor 20
3, 204, 208, 211, 220, 225, 226
Can receive signals from.

The sensors 203, 204, 208, 211, 225, 22 other than the fixing roller front sensor 220 are provided.
6 is for detecting the recording sheet P by the sensor flag blocking the photosensor when the recording sheet P hits the sensor flag, and this structure is usually widely used.

The main motor 234 supplies power to each part.

The display panel 235 displays the status and the like to convey information to the user.

The printer controller 233 is connected to an external device 236 such as a personal computer via an interface.

In FIG. 1, the printer controller 233 is
After the recording sheet P passes through the pre-registration sensor 211, if the recording sheet P does not pass through the fixing discharge sensor 225 at an expected timing, it is determined that a jam has occurred in the printer, and the conveyance of the recording sheet P is stopped. Let

Next, the sheet wrap detection means used in the fixing device 219 will be described.

FIG. 2 shows the structure around the fixing roller front sensor 220.

Reference numeral 301 is a sensor flag which is a part of the first sensor, 302 is a contact surface, 303 is a light shielding portion, 304 is a transmissive photosensor, 305 is a lever, and 306 is a solenoid coil (hereinafter referred to as a moving means). , 307 is a spring, 308 is a fulcrum, 309 is a force point, 3
Reference numeral 10 is an action point, and Q is a recording sheet conveyance path.

The fixing roller front sensor 220 is composed of a sensor flag 301 and a transmission type photo sensor 304.

The sensor flag 301 in the figure indicates the recording sheet P.
A contact surface 302 that comes into contact with a transparent photosensor 304
The recording sheet P has a light-shielding portion 303 that shields the recording sheet P, and is arranged so as to be movable in the vertical direction with respect to the recording sheet P.

This sensor flag 301 has a lever 305.
Is connected to the solenoid 306 via.

The solenoid 306 has a spring 307,
The printer control unit 233 can switch on and off.

The lever 305 is a lever that can be rotated by a fulcrum 308 that can rotate in the direction of the arrow. When the force point 309 is pulled in the direction of the arrow a by the solenoid 306, the point of action 310 moves in the direction of the arrow b.

The transmissive photosensor 304 is connected to the printer control section 233 and transmits to the printer control section 233 whether or not the light blocking section 303 blocks the transmitted light.

Next, FIG. 3 shows an explanatory view for explaining the movement of the lever 305 from the side direction.

FIG. 3 is a diagram best showing the features of the present invention.

Reference numeral 104 denotes a separation claw for separating the recording sheet P from the fixing roller 221.

The object of the present invention is to detect the recording sheet P wound around the fixing roller 221 or the pressure roller 223, but as described above, the printer control section 23.
When the recording sheet P does not pass the fixing discharge sensor 225 at an expected timing after the recording sheet P passes the pre-registration sensor 211, it is determined that a jam has occurred in the printer, and Since the conveyance is stopped, if the length of the recording sheet P in the conveying direction is equal to or more than a certain value, the recording sheet P will not be generated when a winding jam occurs.
Does not wind around the fixing roller 221 or the pressure roller 223, and a part thereof remains in front of the entrance of the fixing roller 221.

Therefore, as shown in FIG. 3, by sensing the front of the entrance of the fixing roller 221, it is possible to detect the winding jam.

FIG. 3A shows a state where the solenoid 306 is not energized.

3 (b) and 3 (c) both show the state in which the solenoid 306 is energized, but FIG. 3 (b) shows the recording staying on the conveying path Q of the recording sheet. FIG. 3C shows a case where the sheet P is not present and a case where a winding jam occurs.

The printer control unit 233 has a predetermined opportunity, that is, when the laser beam printer 201 recognizes a jam, when the power is turned on, or after the user opens and closes the door of the laser beam printer 201 in order to process the jam (device When there is a possibility of winding jam such as after returning after the operation is temporarily stopped), the solenoid 306 is energized to bring the sensor flag 301 close to the conveyance path Q of the recording sheet.

At this time, if there is no staying recording sheet P, as shown in FIG. 3B, the light shielding unit 303 does not keep the transmission type photosensor 304 from being shielded, and the transmission type photosensor 304 does not have to be shielded. Move to the top.

If there is a wrapping jam, then FIG.
As shown in (c), the movement of the sensor flag 301 is blocked by the staying recording sheet P, and the light shielding unit 303 shields the transmissive photosensor 304 from light.

In this way, the transmissive photosensor 30
4 can detect a winding jam.

Further, since the sensor flag 301 is kept away from the recording sheet P during printing as shown in FIG. 3A, the toner is scattered by the sensor flag 301 (the sensor flag 301 corresponds to the recording sheet P). The problem that the toner image before fixing is disturbed by the impact does not occur.

FIG. 4 is a flow chart showing the procedure of the above-mentioned winding detection and the subsequent treatment.

First, the process starts in S401.

Next, in S402, the printer control unit 233.
At a predetermined opportunity, that is, the laser beam printer 201
The laser beam printer 20 when the user recognizes a jam, when the power is turned on, or when the user attempts to handle the jam.
1 is opened or closed (after the operation of the apparatus is temporarily stopped and then returned), and when there is a possibility of a jam jam, the solenoid 306 is energized (solenoid O
N), the sensor flag 301 is brought close to the conveyance path Q of the recording sheet.

Then, in S403, it is detected whether or not the transmissive photosensor 304 is shielded from light.

In S403, when the transmission type photo sensor 304 is shielded from light, the printer control section 233 determines the occurrence of a winding jam and stops the driving of the main motor 234 (S406) to display the display panel 235 and the outside. The occurrence of the winding jam is displayed on the device 236 to notify the user (S407).

Then, the process proceeds to S408.

In S403, when the transmissive photosensor 304 is not shielded from light, the printer control section 233 determines that a winding jam has not occurred, and the main motor 2
34 (S404), and the fixing roller front sensor 220
Other than sensors 203, 204, 208, 211, 22
5, the sheet carry-out route of each part is checked (S405).

Then, the process proceeds to S408.

Then, the printer controller 233 turns off the energization of the solenoid 306 (S408), and ends the processing (S409).

(Second Embodiment) Next, a second embodiment will be described with reference to FIGS.

FIG. 5 is a diagram of the sensor used in the second embodiment, FIG. 6 is a diagram for explaining the behavior of the sensor in the second embodiment, and FIG.
9 is a flowchart of the second embodiment.

In FIG. 5, 501 is a sensor flag and 5 is a sensor flag.
Reference numeral 02 is a switch, 503 is a first gear, 504 is a joining portion, 505 is a motor as a moving unit, 506 is a second gear, and 520 is a fixing roller front sensor which is the first sensor in the second embodiment. is there.

The fixing roller front sensor 520 is composed of a sensor flag 501 and a switch 502.

In this embodiment, the fixing roller front sensor 220 and the solenoid 306 shown in FIG. 2 in the first embodiment are replaced by the fixing roller front sensor 520 and the motor 50 shown in FIG.
5 and is connected via gears 503 and 506.

The sensor flag 501 in this embodiment is
It has a switch 502 and a joining portion 504 that joins with the first gear 503, and is movably arranged in the up-down direction (the direction perpendicular to the conveyance path Q of the recording sheet).

The switch 502 has such a sensitivity that the switch 502 is turned on by the pressure of the recording sheet P staying.

The switch 502 is for the printer controller 2
33, the printer control unit 233 can detect whether or not the switch 502 is pressed.

The motor 505 can be driven in both forward and reverse directions by the printer control unit 233, and the second gear 506 can be used.
And the sensor flag 501 is moved up and down via the first gear 503.

Next, FIG. 6 shows an explanatory view of the fixing device 219 in this embodiment as seen from the lateral direction.

Normally, the switch 502 is kept away from the conveyance path Q of the recording sheet as shown in FIG. 6A, but when the printer recognizes a jam, when the power is turned on, or when the user jams the jam. The motor 505 brings the recording sheet closer to the conveyance path Q of the recording sheet when a jam may occur, such as after opening and closing the door of the laser printer 1 for processing.

At this time, if there is no recording sheet P staying, the switch 502 is not pressed as shown in FIG. 6B, but if there is a winding jam, the recording sheet is as shown in FIG. 6C. P pushes switch 502 to turn it on.

The printer controller 233 uses the switch 502.
ON / OFF of detects the winding jam.

FIG. 7 shows a flow chart showing the procedure for detecting the jammed jam and the subsequent treatment.

First, the process starts in S701.

Next, in step S702, the printer control unit 233.
At a predetermined opportunity, that is, the laser beam printer 201
The laser beam printer 20 when the user recognizes a jam, when the power is turned on, or when the user attempts to handle the jam.
1 is opened and closed (after the operation of the apparatus is temporarily stopped and then returned), and when there is a possibility of a jam jam, the motor 505 is normally rotated to convey the sensor flag 501 to convey the recording sheet. Approach route Q.

Then, in step S703, the switch 502 turns off.
It is detected whether N has been done.

When the switch 502 is turned on in S703, the printer control section 233 determines the occurrence of a winding jam and stops driving the main motor 234 (S706) to display the display panel 235 and the external device 236.
The occurrence of wrapping jam is displayed to notify the user (S707).

Then, the process proceeds to S708.

When the switch 502 is not turned on in step S703, the printer control unit 233 determines that a winding jam has not occurred, drives the main motor 234 (step S704), and causes the sensors other than the fixing roller pre-sensor 220 to operate. Sensors 203, 204, 208, 211, 225, 226
The sheet carry-out route is checked according to (S70).
5).

Then, the process proceeds to S708.

Then, the printer controller 233 controls the motor 5
05 is rotated in the reverse direction (S708), the sensor flag 501 is moved away from the recording sheet conveyance path Q, and the process ends (S4).
09).

Also, in this embodiment, the switch 502
Alternatively, a wrap jam may be detected by using a pressure sensor and an appropriate pressure threshold value.

(Third Embodiment) Next, a third embodiment will be described with reference to FIGS. 8 and 9.

FIG. 8 is a diagram of the sensor used in the third embodiment, and FIG. 9 is a diagram for explaining the behavior of the sensor in the third embodiment.

801 is a sensor flag, 802 is a lever,
803 is the first rotation axis, 804 is a transmissive photosensor,
805 is a second rotary shaft, 806 is a solenoid that is a moving means, 807 is a connection point, 808 is a spring, and 820 is
It is a sensor before the fixing roller which is the first sensor in the third embodiment.

The fixing roller front sensor 820 is composed of a sensor flag 801 and a transmission type photo sensor 804.

In the first embodiment, depending on the attractive force of the solenoid 306 and the elasticity of the recording sheet P, the recording sheet P on which the sensor flag 301 stays is pushed up excessively,
Despite the recording sheets P remaining, the light blocking portion 3
It is conceivable that 03 may pass through the transmissive photosensor 304 in the upward direction, causing an error in detection.

In this embodiment, the possibility is reduced, and the fixing roller front sensor 220 shown in FIG. 2 in the first embodiment is replaced with the fixing roller front sensor 820 shown in FIG.
By using a suitable lever 802.

The sensor flag 801 indicates the first rotary shaft 80.
It is attached to a lever 802 having a concave shape so as to rotate in the arrow direction by 3.

A transmission type photo sensor 804 is attached to the lower portion of the lever 802, and the light is shielded when the sensor flag 801 reaches a certain angle.

The lever 802 is connected to the solenoid 806 by the second rotating shaft 805 so as to rotate in the arrow direction.

The solenoid 806 has a spring 808, and when not energized, the spring 808 relaxes.

The lever 802 has a connection point 807 with the solenoid 806 as a force point, a second rotation shaft 805 as a fulcrum, and a first point.
The rotating shaft 803 can be considered as the point of action, and when the solenoid 806 is energized and the connecting point 807 moves in the direction of arrow c, the first rotating shaft 803 moves in the direction of arrow d.

The sensor flag 801 is normally a lever 802.
The angle shown in FIG. 8 is maintained regardless of the angle of
When pressure is applied from the upper portion of the sensor flag 801, the sensor flag 801 rotates counterclockwise to shield the transmissive photosensor 804 from light.

In this embodiment as well, as in the first embodiment, the solenoid 806 and the transmissive photosensor 804 are connected to the printer controller 233.

FIG. 9 shows the fixing device 219 in this embodiment.
The explanatory view which looked at from the sideways direction is shown.

When the solenoid 806 is not energized, the sensor flag 801 is kept away from the recording sheet P as shown in FIG. 9 (a).

When the printer recognizes a jam, when the power is turned on, or after the user opens and closes the door of the laser printer 1 to process the jam, the printer control unit 233 may consider a jam. Then, the solenoid 806 is energized to turn on the sensor flag 801.
Is brought close to the conveyance path Q of the recording sheet.

At this time, since the sensor flag 801 maintains the angle shown in FIG. 8 regardless of the angle of the lever 802, if there is no recording sheet P remaining, it is shown in FIG. 9 (b). As described above, the sensor flag 801 does not shield the transmissive photosensor 804 from light.

On the other hand, if a winding jam occurs, as shown in FIG. 9C, the sensor flag 801 is turned on by the pressure from the recording sheet P and the transmission type photosensor 80 is displayed.
Since 4 is shielded from light, a wrapping jam can be detected.

(Fourth Embodiment) Next, a fourth embodiment will be described with reference to FIG.

FIG. 10 is a flowchart of the fourth embodiment.

In the first to third embodiments, when the winding jam occurs, the entire recording sheet P is not wound around the fixing roller 221 or the pressure roller 223, and the entrance of the fixing roller 221. I proceeded on the assumption that a part of the fixing roller remains, but the fixing roller 22
Depending on the distance between the fixing roller 221 and the fixing ejection sensor 225 and the size of the recording sheet P, the portion remaining in front of the entrance of the fixing roller 221 may be small and detection may be difficult.

Therefore, in this embodiment, when the recording sheet P passes through the pre-registration sensor 211 and then the recording sheet P does not pass through the fixing discharge sensor 225 at an expected timing, a jam is determined (hereinafter, referred to as a jam). The fixing roller 221 and the pressure roller 223 are reversely rotated by a predetermined length (or a predetermined time corresponding thereto), and it is considered that the wrapping jam is likely to occur. Perform detection processing.

The predetermined length is determined according to the size of the recording sheet P which is detected by the paper size sensor 204 in advance.

By rotating the fixing roller 221 and the pressure roller 223 in the reverse direction, the recording sheet P is sent back to the front of the entrance of the fixing roller 221, and the detection means (fixing roller pre-sensor) shown in any of the first to third embodiments 220, 520,
820) accuracy can be improved.

When the winding jam is detected by the detection processing, the fixing roller 221 and the pressure roller 223 are further rotated by a predetermined length in the reverse direction.

FIG. 10 is a flow chart showing this process.

First, in S1001, the pre-registration sensor 211
If the recording sheet P does not pass through the fixing discharge sensor 225 at an expected timing after the recording sheet P passes through, the printer control unit 233 determines that the fixing discharge delay jam has occurred.

Then, it is considered that there is a high possibility of a jammed winding, and in S1002, the fixing roller 221 and the pressure roller 2
23 is reversely rotated by a fixed length.

Next, in S1003, the jamming jam is detected by the detecting means (fixing roller pre-sensors 220, 520, 820) shown in any of the first to third embodiments.

When a wrapping jam is detected in S1003, the printer controller 233 displays the occurrence of the wrapping jam on the display panel 235 and the external device 236 to notify the user (S1006).

Then, in S1007, the fixing roller 221
Then, the pressure roller 223 is further rotated by a predetermined length in the reverse direction, and the process is ended (S1008).

In S1003, when the winding jam is not detected, the printer control section 233 determines the sensors 203, 204, 208, 2 other than the fixing roller front sensor 220.
The sheet unloading route check for each part is performed according to 11, 225, and 226 (S1004).

When a jam is detected by checking the sheet discharge path of each part in S1004, the printer control section 233 displays the announcement of the jam location on the display panel 2
35 and the external device 236 to notify the user (S1006), and the process ends (S1008).

The fixing roller 221 and the pressure roller 22
The reverse rotation of 3 may be performed after turning on the power of the main body, after opening and closing the main body door, or the like.

Further, in the first to fourth embodiments, when the fixing device 219 is detachably attached to the main body, the fixing roller front sensors 220, 520 and 820, the solenoid 3 are used.
06, 806, motor 505 and fixing paper ejection sensor 22
Note that 5 does not have to be included in the removable part.

[0152]

As described above, according to the present invention, it is possible to provide a sheet wrapping detecting means and a fixing device capable of accurately detecting a wrapping jam without disturbing a toner image before fixing.

Therefore, the drive of the apparatus can be stopped or rotated in the reverse direction at the time when the winding jam is detected, so that it is possible to avoid the serious winding jam.

[Brief description of drawings]

FIG. 1 is an overall view of an image forming apparatus according to a first embodiment.

FIG. 2 is a diagram of the sensor used in Example 1.

FIG. 3 is an explanatory view of the behavior of the sensor in the first embodiment.

FIG. 4 is a flowchart of the first embodiment.

FIG. 5 is a diagram of a sensor used in Example 2.

FIG. 6 is an explanatory diagram of sensor behavior according to the second embodiment.

FIG. 7 is a flowchart of the second embodiment.

FIG. 8 is a diagram of a sensor used in Example 3.

FIG. 9 is an explanatory view of the behavior of the sensor in the third embodiment.

FIG. 10 is a flowchart of the fourth embodiment.

FIG. 11 is a diagram showing a conventional fixing device.

[Explanation of symbols]

1 Transfer control means 104 Separation claw 211 Sensor before cash register 219 Fixing device 220 Sensor before fixing roller 221 fixing roller 223 Pressure roller 225 Fixing paper ejection sensor 233 Printer control unit 301 sensor flag 304 transmissive photo sensor 306 solenoid 501 sensor flag 502 switch 505 motor 520 Sensor before fixing roller 801 sensor flag 802 lever 804 Transmissive photo sensor 806 solenoid 820 Sensor before fixing roller P recording sheet Q Recording sheet conveyance route

Continued front page    F-term (reference) 2H027 DA39 DC05 DC10 DC14 DC19                       DE02 DE03 DE07 DE10 ED25                       EE04 EE05 EE07 EF01 EF06                       EK03 EK04 EK09                 2H033 AA14 AA18 AA37 BA08 BA10                       BB00 CA17 CA22 CA38 CA40                 2H072 AA02 AA22 AB20 CB08 EA11

Claims (9)

[Claims] 1. A fixing roller rotatably arranged to convey a recording sheet, a pressure roller that makes a pair with the fixing roller and contacts the back surface of the recording sheet, the fixing roller or the pressure roller. A roller or heating means for heating both the fixing roller and the pressure roller, and a recording sheet having a toner image on the surface thereof is passed between the fixing roller and the pressure roller, thereby forming the toner image. In the sheet wrap detection unit of the fixing mechanism for fixing the recording sheet to the recording sheet, a first sensor movably disposed near the upstream side of the fixing roller in the recording sheet conveying direction and detecting the presence or absence of the recording sheet; A fixing unit or a pressure roller, and a moving unit that moves a sensor or a part of the first sensor to move closer to or away from a conveyance path of a recording sheet. A sheet wrapping detection means for detecting a wrapping jam that occurs when the recording sheet is not separated from the sheet. 2. A second sensor, which is disposed near the downstream side of the fixing roller in the transporting direction of the recording sheet, for detecting the presence or absence of the recording sheet, and further upstream of the first sensor in the transporting direction. Third, which detects the presence of recording sheets
And the stop roller is stopped when the recording sheet does not pass through the second sensor at an expected timing after passing through the third sensor. The sheet winding detection means according to claim 1. 3. The first sensor or a part of the first sensor is close to a recording sheet conveyance path at a predetermined occasion, and is usually separated from the recording sheet conveyance path. The sheet wrapping detection means according to claim 1 or 2. 4. The predetermined opportunity is when the apparatus main body is turned on, when the printer recognizes a jam, or after the operation of the apparatus is temporarily stopped and then restored. Item 3. The sheet wrapping detection means according to item 3. 5. The fixing roller and the pressure roller are reversely rotated for a predetermined time before the first sensor or a part of the first sensor is brought close to the conveyance path of the recording sheet in front of the fixing roller. The sheet wrapping detection means according to claim 1 or 2, wherein. 6. The method according to claim 5, further comprising a sensor that detects the size of the recording sheet, and the predetermined time is determined according to the size of the recording sheet detected by the sensor. The sheet winding detection means described. 7. The sheet winding detection means according to claim 1, wherein a solenoid coil or a motor is used as a moving means for moving the first sensor or a part of the first sensor. 8. A fixing device comprising the sheet wrapping detection means according to claim 1. Description: 9. When a wrapping jam is detected,
9. The fixing device according to claim 8, wherein the fixing roller and the pressure roller are rotated in reverse.