JP2002193488A - Paper feeder and image forming apparatus having the same - Google Patents

Abstract

(57) [Problem] To provide a paper feeder capable of reducing the number of parts, simplifying the configuration, and reducing the number of assembling steps, and an image forming apparatus including the same. SOLUTION: A detecting section 9, a first pressing piece 8d pressed by a sheet stored in a sheet storing means 7a, a second pressing piece 8a pressed by a sheet passing a predetermined position, and When the first or second pressing piece 8a, 8d is pressed, there is provided a detecting piece 8b, 8c that moves to a position detected by the detecting unit 9 integrally with the first or second pressing piece 8a, 8d. The presence or absence of a sheet in the sheet storage means 7a and the arrival and passage of the fed sheet to a predetermined position are detected by the detection means 8A having the movable member 8. Then, the judging means includes detecting pieces 8b, 8 by the detecting section 9 of the detecting means 8A.
Based on the detection and non-detection of c, it is determined whether there is a sheet in the sheet storage means 7a and whether the sheet is normally fed to a predetermined position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet feeder and an image forming apparatus having the same, and more particularly to detecting the presence or absence of a sheet in sheet storage means and the arrival and passage of the fed sheet to a predetermined position. The present invention relates to a configuration of a detection unit.

[0002]

2. Description of the Related Art Conventionally, for example, in an image forming apparatus such as a laser printer or a copying machine, a sheet (transfer material, photosensitive paper, etc.) which is a fed sheet is transferred by an image forming mechanism to a transfer method or a direct method. An unfixed toner image corresponding to the target image information is formed and carried, and thereafter, the sheet is introduced into a heat fixing device using a heat roller method or a film heating method, and the unfixed toner image is permanently fixed on the sheet surface. The image is heated and fixed, and output as an image formed product (print, copy).

[0003] Such an image forming apparatus is provided with a sheet feeding device for feeding a sheet stored in a sheet storing means to an image forming mechanism (image forming unit).

When such an image forming apparatus is used, it is necessary for an operator to know whether or not the sheet is normally fed and conveyed. For this reason, a detecting device is arranged in the sheet storing means, and when the detecting device detects that there is no paper in the sheet storing means or detects that the paper has run out during the feeding operation, the detecting device performs the feeding operation. Cancellation is performed so that the operator can be notified that there is no paper as a warning.

Further, a plurality of detecting devices for detecting the arrival of the sheet in the sheet conveying path are arranged, and the detecting device detects whether the sheet has arrived between the detecting devices within a predetermined time. Jam during paper transport (paper transport error)
It is determined whether or not a paper jam has occurred, and if it is determined that a paper jam has occurred, the sheet conveyance is immediately stopped, and the operator can be notified of the occurrence of the paper jam as a warning.

[0006]

However, in such a conventional sheet feeding device and an image forming apparatus provided with the same, the detecting device of the sheet storage means has only a function of simply detecting the presence or absence of a sheet. Therefore, in order to detect whether the paper in the transport path is being transported in a normal state, it is necessary to separately provide another detecting device.

Here, since each detecting device requires an actuator, a sensor, and the like, if an independent detecting device is provided independently, not only the number of components increases but also the component configuration becomes complicated and This leads to an increase in the number of assembling steps, leading to an increase in cost.

Accordingly, the present invention has been made in view of such a situation, and has a paper feeder capable of reducing the number of parts, a simplified configuration, and a reduced number of assembling steps. It is an object of the present invention to provide an image forming apparatus.

[0009]

According to the present invention, there is provided a sheet feeding device for feeding sheets stored in sheet storage means, wherein a sheet is present in the sheet storage means and a predetermined position of the fed sheet is set. Detecting means for detecting arrival and passage of the sheet, and determining whether or not a sheet is present in the sheet storage means and whether or not the sheet has been normally fed to the predetermined position based on a signal from the detecting means. Judgment means;
Wherein the detection unit includes a detection unit, a first pressing piece pressed by a sheet stored in the sheet storage means, and a second pressing piece pressed by a sheet passing through the predetermined position. A movable member having a detection piece that moves to a position detected by the detection unit integrally with the first or second pressure piece when the first or second pressure piece is pressed. The determination unit determines whether a sheet is present in the sheet storage unit and whether the sheet is normally fed to a predetermined position based on detection and non-detection of the detection piece by the detection unit. It is characterized by the following.

Further, according to the present invention, the movable member is moved from the initial position when there is no sheet in the sheet storage means to the first position by pressing the first pressing piece by the sheet stored in the sheet storage means. A first operation of rotating, a second operation of rotating the second pressing piece from the first position to a second position by pressing the second pressing piece by the sheet reaching the predetermined position, the predetermined position A third operation in which the pressing of the second pressing piece is released by the rear end of the sheet having passed through the sheet and the sheet returns to the first position from the second position, and is stored in the sheet storing means. A fourth operation in which the pressing of the first pressing piece is released by feeding the last sheet that has been fed, and returns to the initial position, and reaches the predetermined position after the fourth operation. The second sheet by the last sheet
The fifth pressing operation in which the pressing piece is pressed to rotate to the second position and the rear end of the last sheet having passed the predetermined position after the fifth operation cause the second pressing. The sixth is released when the pressing of the piece is released and returns to the initial position.
And the detecting unit detects the operation of the movable member.

Further, according to the present invention, the movable member includes first and second detection pieces that are detected by the detection section, and the detection section is configured to detect the first and second detection pieces when the movable member is at an initial position. When the movable member moves from the initial position to the first position by the first operation, the movable member is not detected, and the movable member is moved from the first position by the second operation. When the movable member moves to the second position, the second detection piece is detected. When the movable member returns to the first position by the third operation, the detection piece is not detected. Is moved to the initial position by the fourth operation, the first
When the movable member is moved to the second position by the fifth operation, the second member is detected, and the movable member is moved to the initial position by the sixth operation. In the case of moving, the first detection piece is detected.

Further, according to the present invention, the determination unit does not detect that the movable member has performed the second or fifth operation within a predetermined time after the sheet is fed. In this case, it is determined that the sheet is not normally fed to the predetermined position.

[0013] Also, in the present invention, the judging means may include the third step.
Alternatively, when the detecting section does not detect that the sixth operation has been performed, it is determined that the sheet has not normally passed the predetermined position.

According to the present invention, there is provided an image forming apparatus comprising an image forming unit and a sheet feeding device for feeding a sheet to the image forming unit, wherein the sheet feeding device is as described above. It is characterized by the following.

Further, as in the present invention, the detecting portion, the first pressing piece pressed by the sheet stored in the sheet storing means, and the second pressing piece pressed by the sheet passing through a predetermined position. When the first or second pressing piece is pressed,
The presence or absence of the sheet in the sheet storage means and the feeding of the sheet are detected by a detecting means having a movable member having the first or second pressing piece and a detecting piece that moves to a position detected by the detecting unit integrally. The arrival and passage of the sheet to a predetermined position are detected.
The determining means determines whether or not a sheet is present in the sheet storage means and whether or not the sheet has been normally fed to a predetermined position based on the detection and non-detection of the detection piece by the detecting unit of the detecting means.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a diagram showing a schematic configuration of a color image forming apparatus which is an example of an image forming apparatus provided with a sheet feeding device according to a first embodiment of the present invention.

In FIG. 1, reference numeral 100 denotes a color image forming apparatus.
The photosensitive drum 1 is an image bearing member rotatably supported in the direction. Reference numeral 4 denotes a developing device. The developing device 4 includes four developing devices 4Bk, each containing four color toners of black (Bk), magenta (M), cyan (C), and yellow (Y). 4M, 4C, and 4Y. The developing units 4Bk, 4M, 4C, 4Y
Is configured to selectively contact the photosensitive drum 1 by a contacting / separating unit (not shown).

Reference numeral 2 denotes a charger for uniformly charging the surface of the photosensitive drum 1, and 3 denotes a laser exposure optical system for forming an electrostatic latent image on the surface of the photosensitive drum 1 by scanning light (laser light). During image formation, the photosensitive drum 1 is uniformly charged by the charger 2, and then an electrostatic latent image is formed on the surface by scanning light (laser light) by the laser exposure optical system 3.

The electrostatic latent image is thereafter developed with a black toner image by attaching a black toner thereto by, for example, a developing device 4Bk.
The primary transfer is performed by the primary transfer roller 6. The formation, development, and primary transfer of the electrostatic latent image are sequentially performed for each of the four colors, whereby a four-color superimposed color toner image is formed on the intermediate transfer belt 5. Reference numeral 101 denotes an image forming unit including the photosensitive drum 1, the charger 2, the laser exposure optical system 3, the intermediate transfer belt 5, and the like.

In FIG. 1, S is a sheet, which is a sheet, and 7a is a cassette holder 7a, 7b, which is a sheet storage unit for storing the sheet S, and pickup rollers, which are sheet feeding means. Reference numeral 7c denotes an intermediate plate rotatably provided on a cassette holder 7a with a dowel (not shown) as a fulcrum. The intermediate plate 7c is loaded with paper S and is urged in the direction of the pickup roller 7b by a spring 7d. The feeding pressure to the pickup roller 7b is supplied in accordance with the amount of paper S (paper weight). Here, reference numeral 102 denotes a sheet feeding device provided with the cassette holder 7a, the pickup roller 7b, and the like.

After the sheet S is sent out from the cassette holder 7a by the pickup roller 7b, it reaches the pair of registration rollers 7g via the conveyance rollers 7e and 7f, and the intermediate transfer belt 5 is moved by the pair of registration rollers 7g.
The sheet is conveyed and introduced into the press-contact nip portion between the roller and the secondary transfer roller 10 at a predetermined timing synchronized with the rotation of the intermediate transfer belt 5.

The toner image on the intermediate transfer belt 5 is transferred by being conveyed and introduced at a predetermined timing to the press-contact nip portion between the intermediate transfer belt 5 and the secondary transfer roller 10 as described above. The paper S onto which the toner image has been transferred in this manner is transported and introduced to the fixing device 12 by the transport belt 11. After the fixing device 12 undergoes the heat fixing process of the toner image, the paper S is transported. The paper is output to a paper discharge tray 16 by a paper discharge roller pair 15 through a path 14.

Note that this color image forming apparatus 100
A duplex unit 17 is provided to enable duplex printing. In duplex printing, after the toner image is transferred to the first side (front side) and the toner image is fixed by the fixing device 12, the switching guide 13 is switched to a dotted line. The paper S is transported to the duplex unit 17 by switching to the position indicated by.

Here, the sheet S thus conveyed to the duplex unit 17 is once conveyed to the switchback conveyance path 17a, then switched back and conveyed to the double-sided conveyance path 17b, whereby the front and back are switched. Thereafter, the sheet is conveyed by the conveying roller 17c, and the re-conveying guide 7d, the conveying roller 7f, and the registration roller pair 7g
After the toner image is transferred to the second surface (back surface) by the secondary transfer roller 10, the toner image is fixed by the fixing device 12, and is discharged to the discharge tray 16.

In the drawing, reference numeral 8A denotes a detecting device which is a detecting means for detecting the presence or absence of the paper S in the cassette holder 7a (the middle plate 7c) and a jam of the paper S, and the detecting device 8A is a detecting portion. It includes a sensor 9 and an actuator 8 as an operating member.

In this embodiment, the sensor 9
As shown in FIG. 2, a light emitting unit 9a that emits light,
A photointerrupter having a light receiving unit 9b for receiving light emitted from the light emitting unit 9a and passing through the slit 9c is used. The optical path is opened or blocked by the actuator 8.

The sensor light receiving section 9b is provided at a predetermined position of the color image forming apparatus 100 with a high level signal as a light receiving signal when the light path is open, and a low level signal as a non-light receiving signal when the light path is cut off. 3 is output to the control unit 30 shown in FIG. The control unit 30 includes a CPU that performs arithmetic processing as shown in FIG.
The system includes a ROM 32 in which a control sequence of the color image forming apparatus 100 is written, and a driver 33 for operating the sensor 9.

On the other hand, the actuator 8 is rotatably supported by the color image forming apparatus 100 about a shaft (not shown), and has four arms 8a to 8d as shown in FIG. Here, among the four arms 8a to 8d, the first arm 8a located at the uppermost position and the fourth arm 8d located at the lowermost position are used to rotate the actuator 8 by being pressed by the sheet S. The second and third arms 8b and 8c at the center block the optical path of the sensor 9.

In this embodiment, the actuator 8 acts on the pickup roller 7 so as to act on all the sheets S conveyed into the apparatus by the center reference conveyance.
Installed next to b. The pickup roller 7b is urged in a counterclockwise direction by an unillustrated urging member.

Next, the sheet detecting operation of the detecting device 8A having such a configuration will be described.

First, the case where no paper is present in the cassette orchestra 7a will be described.

In this case, that is, the cassette holder 7a (the middle plate 7
In the free state where no paper is present in c), the actuator 8 is positioned such that the fourth arm 8d, which is the first pressing piece, is positioned in the groove (not shown) of the middle plate 7c as shown in FIG. The position is the home position. Here, when the actuator 8 is at the home position, the second arm 8b, which is the first detection piece, blocks the optical path of the sensor 9, and the output signal of the sensor 9 is at a low level.

When the output signal of the sensor 9 is at a low level and the state continues, the control unit 30 as a judging means determines that the actuator 8 is at the home position, that is, that the cassette Is determined not to exist.

Next, the case where the paper S is stacked on the cassette orchestra will be described.

When the sheets S are stacked on the cassette holder 7a, as shown in FIG.
d is pushed up by the sheet S, whereby the actuator 8 rotates clockwise, and moves from the home position shown in FIG. 4 to the first position shown in FIG.

Here, the movement of the actuator 8 to the first position (first operation) causes the second arm 8 to move.
The interruption of the optical path of the sensor 9 by b is released, and the output signal of the sensor 9 switches from the low level to the high level. Then, based on the change in the output signal from the sensor 9, the control unit 30 determines that the sheets S are stacked on the cassette holder 7a. That is, it is determined that the sheet S exists in the cassette holder 7a.

Next, a case where the last sheet S is fed from the cassette holder 7a and the sheet S is exhausted in the cassette holder 7a will be described.

The sheet S is sequentially fed and transported from the cassette holder 7a, and the sheet S in the cassette holder 7a eventually becomes the last sheet. This last sheet S is sent out by the pickup roller 7b, and the rear end of the actuator 8 is After passing through the fourth arm 8d, there is no longer any force to push up the fourth arm 8d, so that the actuator 8 rotates counterclockwise and moves from the first position shown in FIG. 5 to the home position shown in FIG.

Here, the second arm 8b cuts off the optical path of the sensor 9 by the return rotation of the actuator 8 to the home position (fourth operation), and the output signal of the sensor 9 changes from high level to low level. Switch to level. The output signal of the sensor 9 will be described later.
When the last sheet reaches a predetermined position, in this embodiment, the re-conveyance guide 7d, the level is switched from low level to high level.

For this reason, in order to reliably detect the return rotation of the actuator 8 to the home position, the time T1 from the start of sheet feeding to the passage of the fourth arm 8d is set in advance. If the output signal of the sensor 9 is switched from the high level to the low level in a time shorter than the set time T1, the control unit 30 determines that the sheet S has run out in the cassette holder 7a.

The uppermost first arm 8a, which is the second pressing piece of the actuator 8, is connected to the cassette holder 7a.
4 and 5, the re-conveying guide 7 of the duplex unit 17 does not need to be
d.

For this reason, the last sheet S sent out in this way is, for example, in the case of duplex printing, the duplex unit 17
After passing through the re-transport guide 7d, the first arm 8a of the actuator 8 is pressed by the leading end and the lower surface of the sheet S, so that the actuator 8
The first arm 8a shown in FIG. 6 rotates from the home position shown in FIG. 4 to a second position where the first arm 8a is retracted from the re-transport guide 7d.

The rotation of the actuator 8 (fifth operation) causes the third arm 8c to interrupt the optical path of the sensor 9. As a result, the output signal of the sensor 9 temporarily changes from the low level to the high level, and then changes to the low level.

Further, the rear end of the sheet S is
After passing through the (first arm 8a), the actuator 8 returns and rotates to return to the home position shown in FIG. The second arm 8b interrupts the optical path of the sensor 9 by the return rotation (sixth operation) of the actuator 8. As a result, the output signal of the sensor 9 temporarily changes from the low level to the high level, and then changes to the low level. FIG. 7A is a diagram showing a change in the sensor output when such an operation is performed.

As described above, the second or third arm 8b, 8
Due to a change in the signal from the sensor 9 based on the detection and non-detection of c, the cassette orchestra 7a runs out of paper, the leading edge of the paper reaches a predetermined position (re-transport guide 7d) on the transport path, and Passage of a predetermined position (re-conveyance guide 7d) can be detected.

Next, a case where the sheet S remains in the cassette holder 7a even when the sheet S is fed from the cassette holder 7a will be described.

In this case, the sheet S is fed, and the sheet S remains in the cassette holder 7a even if the rear end of the sheet S passes the fourth arm 8d of the actuator 8, so that the actuator 8 is in the state shown in FIG. Remains. Therefore, time T1
, The output signal of the sensor 9 remains at the high level.

After that, when the sheet S conveyed to the duplex unit 17 passes through the re-conveying guide 7d during the double-sided printing, the first arm 8a of the actuator 8 moves the sheet S
The actuator 8 pivots from the first position shown in FIG. 5 to the second position shown in FIG.

The rotation of the actuator 8 (second operation) causes the third arm 8c to interrupt the optical path of the sensor 9. As a result, the output signal of the sensor 9 temporarily changes from the low level to the high level, and then changes to the low level.

Thereafter, when the trailing end of the sheet S passes through the actuator 8, the actuator 8 returns from the second position shown in FIG. 6 to the first position shown in FIG.
Then, by such rotation of the actuator 8 (third operation), the output signal of the sensor 9 changes from high level to low level and then to high level. FIG. 7B is a diagram showing a change in the sensor output when such an operation is performed.

As described above, it is possible to detect from the change in the signal from the sensor 9 that the sheet S is still fed in the cassette holder 7a even if the sheet S is fed. Further, it is possible to detect that the fed sheet S reaches the predetermined position and passes the rear end of the sheet S at the predetermined position.

By the way, the detecting device 8A having such a configuration is used.
Also functions as a detecting device for detecting whether or not the paper S is normally fed.

Next, the jam detecting operation of the detecting device 8A will be described.

The control unit 30 starts detecting the sheet feed start signal (conveyance start signal) from the point of occurrence of the sheet feed start signal (conveyance start signal).
From the detection device 8A (sensor 9) within a predetermined time via
If the sheet leading edge detection signal in FIGS. 7A and 7B is not input, it is determined that the sheet S has jammed before reaching the predetermined position on the transport path.

After the paper leading edge detection signal is input,
If the sheet trailing edge detection signal is not detected from the detecting device 8A (sensor 9), it is determined that the sheet S is jammed over a predetermined position. When it is determined that a jam has occurred, the color image forming apparatus 1
00 is urgently stopped, and the occurrence of a jam is displayed.

As described above, the presence or absence of the sheet S on the cassette orch can be detected by one detecting device 8A.
In addition, normal arrival and passage of the conveyed sheet S to a predetermined position on the conveyance path can be detected, thereby detecting a sheet conveyance abnormality (jam). As a result, the number of parts can be reduced, the configuration is simplified,
Assembly efficiency also increases. This can also reduce costs.

In the above description, a case has been described in which the two arms 8b and 8c for shutting off the sensor 9 are formed integrally with one actuator 8. Is valid when the rotation direction of the actuator 8 when the sheet S is loaded is the same as the rotation direction of the actuator 8 when the sheet S reaches a predetermined position.

Therefore, if the rotation direction of the actuator 8 when the paper S is stacked on the cassette holder 7a is different from the rotation direction of the actuator 8 when the paper S reaches a predetermined position, the presence or absence of the paper is detected. It is necessary to separately provide an actuator for detecting the jam and an actuator for detecting the jam.

Next, a second embodiment of the present invention will be described in which such an actuator for detecting the presence / absence of paper and an actuator for detecting jam are separately provided.

FIG. 8 is an enlarged view of a main part of the sheet feeding device according to the present embodiment. Note that FIG.
The same reference numerals indicate the same or corresponding parts.

In the same figure, reference numeral 80 denotes a first paper detection detection sheet.
The first actuator 80 is provided with an arm 8d for rotating the actuator 80 by being pressed by the sheet S stored in the cassette orch 7a, and an arm 8b for blocking the optical path of the sensor 9.

Reference numeral 81 denotes a second actuator for detecting a jam. The second actuator 81 is located at a predetermined position, in this embodiment, the pickup roller 7b.
Guide 10 arranged upstream in the paper transport direction (see FIG. 1)
An arm 8a for rotating the second actuator 81 in contact with the sheet S fed to the sheet 2a and an arm 8c for interrupting the optical path of the sensor 9 are provided. Here, the first actuator 80 is urged in a counterclockwise direction by an unillustrated urging unit, and the second actuator 80 is urged in a clockwise direction by an unillustrated urging unit.

FIG. 9 shows a free state in which no paper is present in the cassette orchestra 7a. At this time, the arm 8d of the first actuator 80 is positioned by a groove (not shown) of the middle plate 7c. Is the home position. When the first actuator 80 is at the home position, the arm 8b blocks the optical path of the sensor 9, and the output signal of the sensor 9 is at a low level.

When the output signal of the sensor 9 is at the low level and the state continues, the control unit 30 determines that the first actuator 80 is at the home position, that is, there is no sheet in the cassette slot 7a. Judge that you have not.

On the other hand, FIG. 9 is a view showing a case where the sheets S are stacked. At this time, the arm 8d of the first actuator 80 is pressed and pushed up by the sheets S, whereby the first actuator 80 is rotated clockwise. Pivot in the direction
It moves from the home position shown in FIG. 8 to the first position shown in FIG.

Here, such a first actuator 8
0 to the first position (first operation), the interruption of the optical path of the sensor 9 by the arm 8b is released and the sensor 9
Switches from low level to high level.
Then, based on the change in the output signal from the sensor 9, the control unit 30 determines that the sheets S are stacked on the cassette holder 7a.

FIG. 10 is a view showing a state in which the paper S is conveyed along the guide 102a. At this time, the arm 8a of the second actuator 81 causes the paper S to be fed by the pickup roller 7b. The second actuator 81 rotates from the first position shown in FIG. 9 to the second position shown in FIG.

Then, such a second actuator 8
The rotation of 1 (second operation) causes the arm 8c to interrupt the optical path of the sensor 9. As a result, the output signal of the sensor 9 temporarily changes from the low level to the high level, and then changes to the low level.

Thereafter, when the rear end of the sheet S passes through the second actuator 81, the second actuator 81
Pivots from the second position shown in FIG. 9 to the first position shown in FIG. Then, by such rotation of the actuator 8 (third operation), the output signal of the sensor 9 changes from high level to low level and then to high level.

The sheet S is sequentially fed and conveyed from the cassette holder 7a, and the sheet S in the cassette holder 7a eventually becomes the last sheet. The last sheet S is sent out by the pickup roller 7b, and the rear end is the second sheet. Actuator 81
After passing through the arm 8d, there is no longer any force to push up the arm 8d, so that the first actuator 80 rotates counterclockwise and moves from the first position shown in FIG. 9 to the home position shown in FIG.

Here, such a first actuator 8
By the return rotation to the home position of 0 (fourth operation), the arm 8b interrupts the optical path of the sensor 9, and the output signal of the sensor 9 switches from high level to low level.

Further, when the arm 8a of the second actuator 81 is pushed by the last sheet S and the leading end and the lower surface of the sheet S, the second actuator 81 is moved from the home position shown in FIG. 8 to the second position shown in FIG. To the position.

Then, such a second actuator 8
The rotation of the first (fifth operation) causes the arm 8c to interrupt the optical path of the sensor 9. As a result, the output signal of the sensor 9 temporarily changes from the low level to the high level, and then changes to the low level.

When the trailing end of the sheet S passes through the second actuator 81 (arm 8a), the second actuator 81 returns to the home position shown in FIG. The arm 8b interrupts the optical path of the sensor 9 by the return rotation (sixth operation) of the second actuator 81. As a result, the output signal of the sensor 9 temporarily changes from the low level to the high level, and then changes to the low level.

Then, with this configuration,
Even if the rotation direction of the first actuator 80 when the sheets S are stacked on the cassette holder 7a and the rotation direction of the second actuator 81 when the sheets S reach a predetermined position, even if the rotation direction of the second actuator 81 is different, one detecting device 8A The presence / absence of the sheet S on the cassette orchestra can be detected, and the normal arrival and passage of the conveyed sheet S to a predetermined position on the conveyance path can be detected, whereby the sheet conveyance abnormality (jam). Can be detected.

[0077]

As described above, according to the present invention, the presence or absence of a sheet in the sheet storage means and the arrival and passage of the fed sheet to a predetermined position can be detected by one detecting means. , The number of parts can be reduced,
The configuration is simplified, and the number of assembly steps is reduced. This can also reduce costs.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a schematic configuration of a color image forming apparatus as an example of an image forming apparatus including a sheet feeding device according to a first embodiment of the present invention.

FIG. 2 is a perspective view of a detection device provided in the paper feeding device.

FIG. 3 is a diagram showing a part of a control block of the paper feeding device.

FIG. 4 is a diagram showing a state of the detection device in an initial state.

FIG. 5 is a diagram showing a state of the detection device when paper is stacked.

FIG. 6 is a diagram illustrating a state of the detection device when a sheet reaches a predetermined position.

FIG. 7 is a diagram showing a sensor output signal of the detection device.

FIG. 8 is an enlarged view of a main part of a sheet feeding device according to a second embodiment of the present invention.

FIG. 9 is a diagram showing a state of the detection device when paper is stacked.

FIG. 10 is a diagram illustrating a state of the detection device when a sheet reaches a predetermined position.

[Explanation of symbols]

 Reference numeral 7a Cassette holder 7d Re-transport guide 8A Detector 8 Actuator 8a First arm 8b Second arm 8c Third arm 8d Fourth arm 80 First actuator 81 Second actuator 9 Sensor 17 Double-sided unit 100 Color image forming apparatus 101 Image forming section 101 102 paper feeder 102a guide S paper

Claims (6)

[Claims] 1. A sheet feeding device for feeding a sheet stored in a sheet storage unit, wherein the presence / absence of a sheet in the sheet storage unit and the arrival and passage of the fed sheet to a predetermined position are detected. Detecting means, and determining means for determining, based on a signal from the detecting means, the presence or absence of a sheet in the sheet storage means and whether or not the sheet is normally fed to the predetermined position. The detection unit includes a detection unit, a first pressing piece pressed by a sheet stored in the sheet storage means, a second pressing piece pressed by a sheet passing through the predetermined position, Or a movable member having a detecting piece that moves to a position detected by the detecting unit integrally with the first or second pressing piece when the second pressing piece is pressed, The judging means is provided by the detecting unit. Serial detecting piece detection and sheet feeder presence and the sheet of the sheet of the sheet storage means and wherein the determining whether it is fed to a predetermined position correctly on the basis of non-detection. 2. The movable member according to claim 1, wherein said first pressing piece is pressed by a sheet stored in said sheet storage means from an initial position when no sheet is present in said sheet storage means.
The first operation of rotating to the position of the first position, the second pressing piece is pressed by the sheet reaching the predetermined position,
The second operation of pivoting from the second position to the second position, the second pressing piece is released from the second position by the rear end of the sheet passing the predetermined position, and the second position is moved from the second position to the second position. 1
The third operation of returning to the position shown in FIG. 3 is performed. When the last sheet stored in the sheet storing means is fed, the pressing of the first pressing piece is released, and the rotation is returned to the initial position. The fourth operation, the fifth operation in which the second pressing piece is pressed by the last sheet that has reached the predetermined position after the fourth operation and the second sheet is rotated to the second position, and the fifth operation, When the rear end of the last sheet has passed the predetermined position after the above operation, the pressing of the second pressing piece is released, and a sixth operation of returning to the initial position and rotating is performed. The sheet feeding device according to claim 1, wherein the unit detects an operation of the movable member. 3. The movable member includes first and second detection pieces that are detected by the detection section. The detection section detects the first detection piece when the movable member is at an initial position. When the movable member is moved from the initial position to the first position by the first operation, the movable member is not detected, and the movable member is moved to the first position by the second operation.
When the movable member returns to the first position by the third operation when the movable member returns to the first position by detecting the second detection piece when the movable member moves from the position to the second position, the detection piece is not detected. When the movable member has moved to the initial position by the fourth operation, the first detection piece is detected. When the movable member has moved to the second position by the fifth operation, the second detection member has been detected. And detecting the first detecting piece when the movable member has moved to the initial position in the previous period by the sixth operation. Paper equipment. 4. The method according to claim 1, wherein the determining unit determines that the movable member is in the second or fifth position within a predetermined time after the sheet is fed.
3. The sheet feeding device according to claim 2, wherein when the detection unit does not detect that the operation of (1) has been performed, it is determined that the sheet is not normally fed to the predetermined position. . 5. When the detecting unit does not detect that the third or sixth operation has been performed, the determination unit determines that the sheet has not normally passed the predetermined position. The sheet feeding device according to claim 2, wherein the determination is made. 6. An image forming apparatus comprising: an image forming unit; and a sheet feeding device for feeding a sheet to the image forming unit, wherein the sheet feeding device is any one of claims 1 to 5. An image forming apparatus characterized in that: