JP2015086028A - Paper feeding device and image forming apparatus - Google Patents

Abstract

Before the start of image formation using a developer, it is possible to detect the presence or absence of a medium to be fed next. When it is detected that there is no medium to be fed, image formation is performed. Is stopped, and a sheet feeding device capable of preventing contamination of the secondary transfer unit and an image forming apparatus including the sheet feeding device are provided. A medium tray on which a medium is placed, a sheet feeding member that feeds the medium, a conveying roller member that conveys the medium to the sheet feeding member, and a conveying roller member that are disposed opposite to each other and are in contact with the medium A counter member having a friction member and a counter frame that supports the friction member, biasing means for biasing the counter member upstream in the sheet feeding direction of the medium, and displacement of the counter member from a predetermined position of the medium tray are detected. Detecting means, and the opposing member stops at a predetermined position of the medium tray by the urging force of the urging means in a state where the medium is not placed on the medium tray, and the detecting means moves to the downstream side of the medium feeding direction. The displacement of the facing member accompanying the transport operation is detected. [Selection] Figure 1

Description

  The present invention relates to a sheet feeding device that feeds a medium to an image forming apparatus, and an image forming apparatus including the sheet feeding device.

  2. Description of the Related Art Conventionally, in an image forming apparatus that performs color printing or monochrome printing, there is an apparatus that employs an intermediate transfer method using an intermediate transfer belt as an image forming method. In the intermediate transfer method, the developer image formed in the image forming unit is temporarily transferred to the intermediate transfer belt (primary transfer), and then the developer image on the intermediate transfer belt is transferred to the medium (secondary transfer). ) To obtain a printed image.

JP 2012-53390 A

  However, in an image forming apparatus having a conventional configuration, for the purpose of improving the printing speed during continuous printing, image formation using a developer for the next medium is completed before feeding of the medium being printed is completed. There was something that started.

  By the way, after the image formation using the developer is started, if there is no medium to be fed, the previously formed developer image is wasted, or the secondary transfer means is caused by the formed developer image. As a result, it was soiled, causing back-stained printing.

  The present invention has been made in view of such a situation, and an object of the present invention is to detect the presence or absence of a medium to be fed next before the start of image formation using a developer. When a state in which no medium is fed is detected, the image forming is stopped to prevent the secondary transfer unit from being soiled, and the image forming apparatus including the sheet feeding device Is to provide.

  In order to solve the above problems, a paper feeding device according to the present invention is placed on a medium tray for placing a plurality of media, a paper feeding member for feeding the media into the device, and the media tray. And a conveying roller member that conveys the medium to the sheet feeding member by rotating the medium, a friction member that is disposed to face the conveying roller member and that contacts the medium, and a counter frame that supports the friction member. A counter member; a biasing unit that biases the counter member upstream in the sheet feeding direction of the medium; and a detection unit that detects displacement of the counter member from a predetermined position of the medium tray. In a state where the medium is not placed on the medium tray, the medium is stopped at a predetermined position of the medium tray by the urging force of the urging means, and the detecting means places the medium on the medium tray. Where In, it is characterized by detecting the displacement of the facing member with the conveying operation of the sheet feeding direction downstream side of the medium by the conveying roller member.

  In addition, the image forming apparatus according to the present invention rotates a medium tray on which a plurality of media are loaded, a sheet feeding member that feeds the medium into the apparatus, and the medium loaded on the medium tray. A conveying roller member that conveys to the paper feeding member; a counter member that is disposed to face the conveying roller member and that contacts the medium; and a counter frame that supports the friction member; An urging unit that urges a member upstream of the medium in the paper feeding direction; and a detecting unit that detects a displacement of the counter member from a predetermined position of the medium tray. The counter member is disposed on the medium tray. In a state where the medium is not placed, the urging force of the urging means stops at a predetermined position of the medium tray, and the detection means is configured to place the medium on the medium tray when the medium is placed. An image is formed on the sheet fed into the apparatus by the sheet feeding member, and a sheet feeding apparatus that detects the displacement of the facing member accompanying the conveyance operation of the medium to the downstream side in the sheet feeding direction by the feeding roller member. And an image forming unit.

  According to the present invention, it is possible to detect the presence / absence of a medium to be fed next before the start of image formation using a developer. By stopping the image formation, it is possible to provide a paper feeding device capable of preventing the secondary transfer unit from being stained and an image forming apparatus including the paper feeding device.

FIG. 2 is a side cross-sectional view for explaining a main configuration of the printer according to the first embodiment. FIG. 3 is a side cross-sectional view illustrating a configuration of a paper feed unit in the first embodiment. It is a perspective view explaining the structure of a friction piece unit. It is a fragmentary perspective view explaining the structure of the notch part of the tray with which a friction piece unit is mounted | worn. It is a figure explaining the state by which the projection part of the friction piece frame was penetrated by the guide groove of a notch part. It is a figure explaining the displacement of the friction piece unit accompanying paper feeding operation. It is a figure explaining the displacement of the friction piece unit accompanying paper feeding operation. FIG. 3 is a side cross-sectional view illustrating a configuration of a paper feed unit in the first embodiment.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, this invention is not limited to the following description, In the range which does not deviate from the summary of this invention, it can change suitably.

[First embodiment]
In the description of the first embodiment, a printer 1 as an image forming apparatus provided with a sheet feeding device according to the present invention will be described. The printer 1 includes a plurality of electrophotographic process units as image forming units. For example, the printer 1 is an intermediate transfer type capable of printing an image based on print data input from an external terminal such as a host computer on a sheet P as a medium. An image forming apparatus.

  FIG. 1 is a side cross-sectional view for explaining a main configuration of the printer 1. The printer 1 is a paper cassette 10 that stores paper P as a medium before printing, and a paper feeding device according to the present embodiment, and feeds the paper P placed on the tray 202 to the print timing adjustment unit 50. A paper feed unit 20, a transport roller pair 30 that transports the paper P fed from the paper cassette 10 to the print timing adjustment unit 50, and a paper feed that detects that the paper P is fed to the print timing adjustment unit 50. A sensor 40, a print timing adjustment unit 50 that feeds the paper P fed by the paper cassette 10 or the paper feed unit 20 in the direction of the arrow x in the figure and feeds it to the transfer belt unit 70, and each developer color. The electrophotographic process unit 60 for forming the corresponding developer image, and the developer image formed in the electrophotographic process unit 60 are primarily transferred to the intermediate transfer belt 71. A transfer belt unit 70 for secondary transfer of the developer image transferred to the intermediate transfer belt 71 to the paper P, and a fixing unit 80 for fixing the developer image on the paper P transferred by the transfer belt unit 70; , A discharge sensor 90 that detects the passage of the paper P on which the developer image is fixed by the fixing unit 70, a transport roller pair 100 that transports the paper P to the medium discharge transport path S, and a medium discharge transport path by the transport roller pair 100. A discharge roller pair 110 for discharging the paper P conveyed to S through the paper discharge port 120 and a stacker 130 for stacking the paper P discharged by the discharge roller pair 110 are provided.

  Here, the paper cassette 10 stores the paper P stacked therein, and is detachably attached to the lower part of the printer 1. In the upper part of the paper cassette 10, a pickup roller 11 that separates and feeds the paper P one by one from its uppermost portion, and a registration roller pair 12 that transports the paper P fed by the pickup roller 11 to the transport roller 30 are arranged. It is installed. The registration roller pair 12 is provided in pressure contact with each other, and is rotated by a driving force transmitted from a driving source (not shown), and the sheet P fed from the pickup roller 11 is nipped and conveyed to the conveying roller pair 30.

  The paper feeding unit 20 is composed of a pair of rollers provided in pressure contact with each other. The paper feeding unit 20 sandwiches and conveys the paper P to the print adjustment timing adjustment unit 50 and the paper P placed on the tray 202 And a pickup roller 203 that is separated from the top one by one and fed to the paper feeding unit 201. A detailed configuration of the paper feeding unit 20 will be described later.

  The conveyance roller pair 30 is provided in pressure contact with each other, is rotated by a driving force transmitted from a driving source (not shown), and sandwiches and conveys the paper P conveyed from the registration roller pair 12 to the printing timing adjustment unit 50.

  The paper feed sensor 40 is a mechanical sensor for detecting that the paper P is fed to the print timing adjustment unit 50, and mechanically operates every time the paper P passes.

  The printing timing adjustment unit 50 is provided in a state where it is at least in pressure contact with each other, rotates by a driving force transmitted from a driving source (not shown), and transfers the paper P fed from the paper cassette 10 or the paper feeding unit 20 to the transfer belt. A roller pair transported to the unit 70 and a writing sensor (not shown) for detecting that the paper P is transported to the roller pair are provided. The developer image primarily transferred to the intermediate transfer belt 71 is transferred to the paper P 2 Adjust the printing timing for the next transfer.

  The electrophotographic process unit 60 includes a process unit 60C, a process unit 60M, and a process unit that form developer images corresponding to developer colors of cyan (C), magenta (M), yellow (Y), and black (K). 60Y and a process unit 60K. Each of the process units 60C, 60M, 60Y, and 60K contains a developer of each color, and a developer image based on the input print data is a photosensitive drum 61C that is an organic photoreceptor, and a photosensitive drum. 61M, formed on the surface of the photosensitive drum 61Y and the photosensitive drum 61K.

  The transfer belt unit 70 primarily transfers the developer image formed in the electrophotographic process unit 60 to the intermediate transfer belt 71, and secondarily transfers the developer image transferred to the intermediate transfer belt 71 to the paper P. Such a transfer belt unit 70 is a developer image formed on the surface of the intermediate transfer belt 71 and the photosensitive drum 61C, the photosensitive drum 61M, the photosensitive drum 61Y, and the photosensitive drum 61K included in each process unit of the electrophotographic process unit 60. The primary transfer roller 72C, the primary transfer roller 72M, the primary transfer roller 72Y, and the primary transfer roller 72K that primarily transfer the toner to the intermediate transfer belt 71, and the developer image transferred to the intermediate transfer belt 71 on the sheet P And a secondary transfer roller pair 73 for secondary transfer.

  The intermediate transfer belt 71 is an endless belt member stretched by a roller 74, a roller 75, and a secondary transfer roller pair 73. When primary transfer of a developer image is performed, a control unit (not shown) Based on the control, each roller rotates to drive in the direction of arrow y in the figure.

  The primary transfer roller 72C, the primary transfer roller 72M, the primary transfer roller 72Y, and the primary transfer roller 72K are provided in the process unit 60C, the process unit 60M, the process unit 60Y, and the process unit 60K of the electrophotographic process unit 60, respectively. The photosensitive drum 61 </ b> C, the photosensitive drum 61 </ b> M, the photosensitive drum 61 </ b> Y, and the photosensitive drum 61 </ b> K are disposed in pressure contact with the intermediate transfer belt 71. A predetermined transfer voltage is applied to the primary transfer roller 72C, the primary transfer roller 72M, the primary transfer roller 72Y, and the primary transfer roller 72K from a high voltage power source (not shown) based on the control (not shown). The developer image formed on each photosensitive drum surface is transferred to the intermediate transfer belt 71 by the transfer voltage.

  The pair of secondary transfer rollers 73 are disposed in pressure contact with each other via the intermediate transfer belt 71. A predetermined transfer voltage is applied to the pair of secondary transfer rollers 73 from a high voltage power source (not shown) based on control (not shown), and the developer image transferred to the intermediate transfer belt 71 has two sheets of paper 2. The next transfer roller 73 is transferred onto the paper P in synchronization with the timing of passing through the nip formed by each roller.

  The fixing unit 80 includes a fixing roller 81 and a pressure roller 82 that are disposed in pressure contact with each other, and a temperature detection unit such as a thermistor (not shown). The fixing roller 81 is formed, for example, by covering a hollow cylindrical metal core made of aluminum or the like with a heat-resistant elastic layer of silicone rubber and coating a PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer) tube thereon. Is formed by. In the cored bar, for example, a heater 81a such as a halogen lamp is provided. The pressure roller 82 has a structure in which a heat-resistant elastic layer of silicone rubber is coated on a metal core made of aluminum or the like, and PFA is coated thereon, so that a pressure contact portion is formed between the pressure roller 82 and the heat roller. It is arranged. In the core bar, for example, a heater 82a such as a halogen lamp is provided. The thermistor is a means for detecting the surface temperature of the fixing roller 81 and is disposed in the vicinity of the fixing roller 81 in a non-contact manner or in contact therewith. By controlling the heater based on the detection result of the surface temperature of the fixing roller 81 detected by the thermistor, the surface temperature of the fixing roller 81 is maintained at a predetermined temperature. Heat and pressure are applied to the developer on the paper P when the paper P on which the developer image has been transferred passes through a nip formed by the fixing roller 81 and the pressure roller 82 maintained at a predetermined temperature. Then, the developer melts and the developer image is fixed.

  The discharge sensor 90 is a mechanical sensor for detecting the passage of the paper P on which the developer image is fixed by the fixing unit 80, and mechanically operates every time the paper P passes.

  The transport roller pair 100 is provided in pressure contact with each other, and is rotated by a driving force transmitted from a driving source (not shown) to transport the paper P to the paper discharge transport path S.

  The discharge roller pair 110 is provided in pressure contact with each other, and is rotated by a driving force transmitted from a driving source (not shown), and the paper P is stacked using the outer casing of the apparatus via the paper discharge port 120. To 130.

  Next, a detailed configuration of the paper feeding unit 20 according to the present embodiment will be described. FIG. 2 is a side cross-sectional view illustrating the configuration of the paper feeding unit 20. FIG. 3 is a perspective view illustrating the configuration of the friction piece unit 205 as the facing member according to the present embodiment, and FIG. 4 illustrates the configuration of the notch portion of the tray 202 on which the friction piece unit 205 is mounted. It is a fragmentary perspective view. The paper feed unit 20 includes a pair of rollers provided in pressure contact with each other. The paper feed unit 20 serves as a paper feed member that sandwiches and conveys the paper P to the print adjustment timing adjustment unit 50, and a tray 202 as a medium tray. In addition to the pick-up roller 203 as a conveying roller member that separates the paper P placed on the sheet one by one from the top and feeds it to the paper feeding unit 201, a spring 204 as a biasing means, a friction piece unit 205, And a sensor 208 as detection means.

  As described above, the sheet feeding unit 201 includes the sheet feeding roller 201a and the retard roller 201b as a pair of rollers, and the sheet P conveyed with the rotation of the pickup roller 203 (in the description of FIG. The paper P2 and the paper P3) are fed one by one to the print timing adjustment unit 50 shown in FIG.

  The tray 202 is a rectangular plate-like member having a placement area larger than the paper size of the paper P to be placed (for example, A4 portrait orientation, A4 landscape orientation). The tray 202 is formed with a notch for holding the friction piece unit 205 movably in the longitudinal direction of the tray 202, that is, in the transport direction of the paper P. The configuration of the notch will be described later together with the description of the friction piece unit 205. Note that one end side of the tray 202 on the paper feed unit 201 side is pivotally supported so as to be rotatable in forward and reverse directions with respect to the main body of the printer 1, and is separated from a position where it abuts on the pickup roller 203 depending on the presence or absence of the paper P. It is configured to be able to rotate to a position where

  The pickup roller 203 is rotated in the direction of the arrow in FIG. 2 by a driving force transmitted from a driving source (not shown), and the paper P placed on the tray 202 is moved in the order of the uppermost paper P1, paper P2, and paper P3. It is conveyed to the paper feed unit 201.

  One end of the spring 204 is fixed to the tray 202 and the other end is locked to the friction piece unit 205, and biases the friction piece unit 205 in the direction opposite to the conveyance direction of the paper P.

  The friction piece unit 205 is disposed to face the pickup roller 203. As shown in FIG. 3, the friction piece unit 205 includes a friction material 207 as a friction member that contacts the paper P and a friction piece frame 206 as an opposing frame that supports the friction material 207. The friction piece frame 206 includes a protruding portion 206 a formed so as to be able to be inserted into a guide groove in a notch portion provided in the tray 202, and a light shielding portion 206 b formed so as to face the detection portion of the sensor 208. The friction material 207 includes a friction material support portion 206c that supports the friction material 207 by, for example, bonding. The length of the light shielding unit 206b according to the present embodiment in the conveyance direction of the paper P (the length indicated by m in FIG. 2) is the distance that the leading edge of the paper P placed on the tray 202 reaches the paper feeding unit 201 (FIG. 2). The distance is set to be larger than the distance indicated by the middle l. For example, when the distance at which the leading edge of the paper P placed on the tray 202 reaches the paper feeding unit 201 is 1, the length of the light shielding unit 206b in the paper P transport direction is greater than 2.

  As the friction material 207, any material can be used as long as it generates a frictional force with the paper P when the paper P is fed out by the pickup roller 203. In this embodiment, the frictional force between the pickup roller 203 and the paper P1, the frictional force between the papers P such as between the paper P1 and the paper P2, or between the paper P2 and the paper P3, the paper P3 and the friction material. The relationship between the friction force between the pickup roller 203 and the paper P1> the friction force between the paper P3 and the friction material 207 and the biasing force due to the spring 204> It is set so that the frictional force relationship between the sheets P, such as between the sheets P1 and P2 or between the sheets P2 and P3, is satisfied.

  The sensor 208 is an optical sensor that is provided at a predetermined position of the tray 202 and is formed of, for example, a photo interrupter. The sensor 208 can detect the displacement of the friction piece unit 205 on the tray 202 by detecting that the light emitted from the light emitting unit (not shown) is blocked and transmitted by the detection unit serving as the light receiving unit.

  Here, the structure of the notch part 202a formed in the tray 202 is demonstrated using FIG.4 and FIG.5. FIG. 5 is a diagram illustrating a state where the protrusion 206a of the friction piece frame 206 is inserted into the guide groove 202b of the notch 202a. As described above, the notch 202 a is formed on the pickup roller 203 side of the tray 202 to hold the friction piece unit 205 movably in the paper P conveyance direction. A guide groove 202b formed so that 206a can be inserted, a guide groove 202c for guiding the light shielding portion 206b of the friction piece frame 206, and a locking hole 202d for locking the spring 204 are provided. As shown in FIG. 5, the protrusion 206a of the friction piece frame 206 is inserted into the guide groove 202b of the notch 202a, and the friction piece unit 205 is held so as to be movable in the conveyance direction of the paper P.

  Next, the operation of the printer 1 including the paper feeding unit 20 having the above configuration will be described.

  First, the paper P (paper P 1, paper P 2, paper P 3) placed on the tray 202 is fed out of the paper P 1 by the rotation of the pickup roller 203 and conveyed to the paper feeding unit 201. In a state where a plurality of sheets P are placed on the sheet feeding tray 202, the uppermost sheet P 1 is fed out by the frictional force generated between the pickup roller 203 and the sheet P and is fed to the sheet feeding unit 201. After the conveyance, the sheet is further fed to the print timing adjustment unit 50 in the printer 1 device.

  At this time, since the sheet P3 placed immediately above the friction piece unit 205 is stopped, the position of the sheet 202 on the upstream side in the transport direction of the sheet P of the tray 202 by the urging force of the spring 204 (hereinafter referred to as the home position). Do not move.

  However, if the paper P is made of a material that is easily charged with static electricity, as shown in FIG. 6, when the uppermost paper P1 is fed out by the pickup roller 203, the paper P2 and the paper P3 below it are also In some cases, the sheet is conveyed to the sheet feeding unit 201.

  In such a state, the friction piece unit 205 moves the same distance in the direction of the arrow z in the drawing as the sheet P3 placed immediately above moves to the sheet feeding unit 201. In the present embodiment, the paper feed unit 201 is a retard roller type paper feed mechanism having a retard roller 201b facing the paper feed roller 201a, and therefore, a plurality of sheets of paper P conveyed are printed while being fed one by one. Since the sheet P is fed to the timing adjustment unit 50, the sheet P (sheet P3) immediately above the friction piece unit 205 is stopped at that position until the sheet P (sheet P2) superimposed thereon is finished. . Therefore, the friction piece unit 205 is also stopped at the same position.

  As described above, the length of the light shielding unit 206b according to this embodiment in the conveyance direction of the paper P (the length indicated by m in FIG. 2) is such that the front end of the paper P placed on the tray 202 reaches the paper feeding unit 201. Therefore, the sensor 208 provided on the tray 202 is in a state in which the displacement of the friction piece unit 205 is not detected.

  Thereafter, when feeding of the paper P (P3) placed immediately above the friction piece unit 205 is started, the paper P (P3) moves to the downstream side in the transport direction of the paper P from the paper feeding unit 201. Accordingly, the friction piece unit 205 moves more than the distance at which the leading edge of the paper P placed on the tray 202 reaches the paper feed unit 201. As a result, as shown in FIG. 7, the detection unit 208 a of the sensor 208 can detect the light emitted by the light emitting unit (not shown), and the displacement of the friction piece unit 205 can be detected. Then, by detecting the displacement of the friction piece unit 205, it is possible to grasp that feeding of the last one of the sheets P (sheet P3) placed on the tray 202 has started.

  Immediately before the paper P is fed to the print timing adjustment unit 50, the electrophotographic process unit 60 converts the developer image based on the input print data into the photosensitive drum 61C, the photosensitive drum 61M, and the photosensitive drum 61Y, which are organic photosensitive members. , Formed on the surface of the photosensitive drum 61K. The developer image formed in the electrophotographic process unit 60 is primarily transferred to the intermediate transfer belt 71 by the transfer belt unit 70, and then is transferred to the sheet P in accordance with the arrival of the sheet P at the print timing adjustment unit 50. Next transferred. The sheet P on which the developer image has been transferred is conveyed to the fixing unit 80 and passes through a nip formed by a fixing roller 81 and a pressure roller 82 maintained at a predetermined temperature, thereby developing on the sheet P. Heat and pressure are applied to the developer, the developer melts, and the developer image is fixed. The paper P that has passed through the fixing unit 80 is discharged to the stacker 130 by the discharge roller pair 110 through the paper discharge port 120, and a series of image forming operations is completed.

  As described above, according to the first embodiment, it is possible to detect the feed information of the last sheet before the image formation using the developer is started, and the next sheet is fed. When it is detected that there is no sheet to be printed, image formation can be interrupted at an early stage to prevent the secondary transfer unit from being stained.

[Second Embodiment]
The paper feed unit according to the second embodiment is substantially the same as the configuration of the paper feed unit 20 according to the first embodiment. Accordingly, in the following description, the same configurations and operations as those of the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  FIG. 8 is a side cross-sectional view illustrating the configuration of the paper feed unit according to the present embodiment. In the present embodiment, the difference from the first embodiment is that an L-shaped recess 202 ′ is formed in the guide groove 202′b of the tray 202 ′ facing the protrusion 206a of the friction piece frame 206 constituting the friction piece unit 205. This is the point where e is formed.

  The recess 202′e feeds the protrusion 206a of the friction piece frame 206 at a position where the friction piece unit 205 has moved farther than the distance at which the leading edge of the paper placed on the tray 202 ′ reaches the paper feed unit 201. It is arrange | positioned facing the part side.

  A paper feed frame 209 as a position restricting unit is a paper conveyance guide to the paper feed unit 201, and a distance at which the front end of the paper on which the friction piece unit 205 is placed on the tray 202 ′ reaches the paper feed unit 201. In the position moved more than the position, the position is located below the friction piece unit 205, and the tray 202 ′ is lowered at the position as it is, that is, rotated on one end side of the tray 202 ′ on the paper feed unit 201 side. When it moves from the contact position to a position separated from the contact position, it is arranged so as to be in a position to contact the tip end portion 206d of the friction piece frame 206.

  Next, the operation of the printer provided with the paper feed unit having the above configuration will be described.

  As in the first embodiment, when the feeding of the paper P placed on the tray 202 ′ is started and the last one is fed, the friction piece unit 205 is placed on the tray 202 ′. When the distance at which the leading edge of the paper P reaches the paper feeding unit 201 also moves greatly, the protrusion 206a of the frictional piece frame 206 becomes an L-shaped concave part 202 ′ formed in the guide groove 202′b of the tray 202 ′. It falls into e due to its own weight. At this time, the L-shaped portion of the recess 202′e serves as a stopper, and the friction piece unit 205 is not pulled back to the home position by the urging force of the spring 204 even when the paper P being fed is exhausted.

When the tray 202 ′ is lowered manually or automatically after the last sheet is completely fed, the sheet feeding frame 209 and the tip end portion 206d of the friction piece frame 206 come into contact with each other, and the friction piece unit 205 is brought into contact. Rotates. As a result, the protrusion 206a of the friction piece frame 206 comes out of the L-shaped recess 202′e formed in the guide groove 202′b, and the friction piece unit 205 is pulled back to the home position by the urging force of the spring 204. Become.

  As described above, according to the second embodiment, in addition to the effects of the first embodiment, after the displacement of the friction piece unit is detected during paper feeding, the friction piece unit is inadvertently pulled back to the home position. Therefore, stable detection is possible.

  In the description of the embodiment of the present invention, the example has been described using the paper feeding method of feeding the paper placed on the tray from the uppermost part. However, the present invention is not limited to this, and the method of feeding the lowermost paper. It doesn't matter. In this case, it can be realized by reversing the vertical relationship between the arrangement positions of the pickup roller and the friction piece unit.

  Note that the present invention can be applied to an image forming apparatus that prints on paper, and the transfer method can use both the direct transfer method and the intermediate transfer method.

DESCRIPTION OF SYMBOLS 1 Printer 10 Paper cassette 11 Pickup roller 12 Registration roller pair 20 Paper feed unit 30 Carrying roller pair 40 Paper feed sensor 50 Print timing adjustment part 60 Electrophotographic process unit 60C, 60M, 60Y, 60K Process unit 61C, 61M, 61Y, 61K Photosensitive drum 70 Transfer belt unit 71 Intermediate transfer belt 72C, 72M, 72Y, 72K Primary transfer roller 73 Secondary transfer roller pair 74 Roller 75 Roller 80 Fixing unit 81 Fixing roller 81a Heating heater 82 Pressure roller 82a Heating heater 90 Discharge sensor 100 transport roller pair 110 discharge roller pair 120 paper discharge port 130 stacker 201 paper feed unit 201a paper feed roller 201b retard roller 202, 202 'tray 202a notch 202b, 202b' guide Groove 202c guide groove 202d locking hole 202'e recess 203 pickup roller 204 spring 205 friction strip unit 206 friction piece frame 206a protruding portion 206b shielding portion 206c friction member support portion 207 the friction material 208 sensor 209 paper feed frame

Claims (8)

A medium tray for placing a plurality of media;
A paper feeding member for feeding the medium into the apparatus;
A conveying roller member that conveys the medium placed on the medium tray to the paper feeding member by rotating;
A counter member that is disposed to face the transport roller member and has a friction member that contacts the medium and a counter frame that supports the friction member;
Urging means for urging the facing member upstream in the sheet feeding direction of the medium;
Detecting means for detecting displacement of the counter member from a predetermined position of the medium tray;
The opposing member is stationary at a predetermined position of the medium tray by the urging force of the urging means in a state where the medium is not placed on the medium tray.
The detection means detects a displacement of the facing member accompanying a transport operation of the medium to the downstream side in the paper feeding direction by the transport roller member when the medium is placed on the medium tray. Paper feeding device to be used. One end side of the medium tray is pivotally supported so as to be rotatable in forward and reverse directions with respect to the apparatus main body, and the opposing member moves between a position where it abuts on the transport roller member and a position where it is separated from the transport roller member. The paper feeding device according to claim 1, wherein the paper feeding device is possible. The counter member has the friction member disposed on the downstream side in the paper feeding direction, the counter frame surface is disposed on the upstream side in the paper feeding direction, and the length of the friction member in the paper feeding direction is mounted on the medium tray. The paper feeding device according to claim 1, wherein a tip of the placed medium is longer than a distance until the leading edge of the medium reaches the paper feeding member by a transport operation by the transport roller member. The detection means is a photo interrupter,
The detection unit detects displacement of the opposing member by detecting light shielding and transmission by a light shielding part provided in the opposing member. The paper feeder described. The amount of movement of the facing member to the downstream side in the sheet feeding direction is larger than the distance until the leading edge of the medium placed on the medium tray reaches the sheet feeding member by the conveying operation by the conveying roller member. Set,
The detecting means detects that the opposing member has moved more than a distance until the leading edge of the medium placed on the medium tray reaches the paper feeding member by a conveying operation by the conveying roller member. The sheet feeding device according to claim 4. The counter member is arranged such that the friction member is arranged in a portion facing the transport roller member at a predetermined position of the medium tray, and the leading end of the medium reaches the paper feed member by the transport operation by the transport roller member. The sheet feeding device according to any one of claims 1 to 5, wherein the opposed frame surface is arranged at a portion facing the conveying roller member at a position moved more than a distance. The medium tray is capable of rotating one end side of the counter member at a position where the counter member has moved larger than the distance until the leading edge of the medium reaches the paper feeding member by the transport operation by the transport roller member. The sheet feeding device according to any one of claims 1 to 6, further comprising a position regulating unit that maintains a position in a state where the facing member is rotated. A paper feeding device according to any one of claims 1 to 7,
An image forming apparatus comprising: an image forming unit that forms an image on the medium fed into the apparatus by the paper feeding member.