JP2007254089A - Paper feeding mechanism and image forming device provided with it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a paper feeding mechanism capable of varying pressing force to a feeding means according to the kind of the loaded recording paper and stably feeding the various papers. <P>SOLUTION: A pickup roller 3 is constituted such that it can be vertically moved with turning of a holder 17 by rotatably supporting one end by the holder 17 turnably supported on a rotation shaft 4a of a feed roller 4. Further, on the holder 17, a pressing plate 17a extending in an upstream in a paper conveying direction is integrally formed on an end opposite to an end supported on the rotation shaft 4a, and a compression spring 18, i.e., a pressing force increase means is arranged above the pressing plate 17a. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a paper feed mechanism that is provided in an image forming apparatus such as a printer, a copier, or a facsimile machine and that feeds recording paper stored in a paper feed cassette to an image forming unit.

  2. Description of the Related Art Conventionally, in image forming apparatuses such as printers, copiers, and facsimile machines, as a paper feeding mechanism for feeding recording paper to an image forming unit, a paper feeding cassette that stores recording paper, A paper feeding mechanism is used that is composed of a pickup roller that is disposed above and that feeds recording paper stored in a paper feeding cassette to the image forming unit in order from the uppermost paper.

  As an example of such a paper feeding mechanism, Patent Document 1 discloses that a paper stacking plate on which recording paper supported in a swingable manner in a paper feed cassette is loaded, and a paper stacking plate that rotates while pressing the paper stacking plate from below. The lifter, which is a rotating member that lifts the paper stacking plate, and the detection lever that is swingably supported above the paper feed cassette and whose tip is in contact with the uppermost recording paper, and the detection lever position are detected. There has been proposed a paper feed mechanism comprising a height detecting means for detecting the height of the topmost recording paper of the recording paper loaded on the paper stacking plate.

In this paper feed mechanism, when a paper feed cassette containing recording paper is mounted on the image forming apparatus main body, the lifter motor provided in the image forming apparatus rotates the lifter so that the paper stacking plate is moved upward. And the recording paper loaded on the paper stacking plate is pushed up. At this time, the paper surface height of the recording paper is detected by the height detection means and the rotation of the paper stacking plate is controlled, so that the paper surface height becomes a predetermined height that can always be fed by the pickup roller. It is configured as follows.
Japanese Patent Laid-Open No. 2001-220022

  However, in the paper feeding mechanism described in Patent Document 1, the paper surface height of the stacked recording paper is maintained at a position suitable for feeding by controlling the rotation of the paper stacking plate. The pressing force to the pickup roller is constant. For this reason, for example, when recording sheets having different basis weights are used, an appropriate pressing force cannot be obtained, and a paper feeding failure such as non-feeding or double feeding may occur.

  In the present invention, in view of the above-described circumstances, the pressing force of the pickup roller onto the recording sheet can be changed according to the type of the recording sheet to be stacked, and various sheets can be stably fed. An object of the present invention is to provide a sheet feeding mechanism and an image forming apparatus including the same.

  In order to achieve the above object, the present invention provides a paper stacking plate on which recording paper configured to be movable up and down, a lifting means for moving the paper stacking plate up and down, and a recording stacked on the paper stacking plate. A biasing means for biasing the pickup roller in a downward direction in a paper feed mechanism comprising a pickup roller that is movable in a vertical direction and feeds the recording paper by contacting the top of the paper with a predetermined pressure; The biasing force is increased in accordance with the upward movement of the pickup roller, and the pressing force of the pickup roller against the recording paper can be adjusted by adjusting the height position of the pickup roller. It is a feature.

  According to the present invention, in the paper feed mechanism having the above-described configuration, a detection unit that detects a height position of the pickup roller, and a biasing unit that is applied to the pickup roller according to the height position of the pickup roller. Storage means storing the urging force, and control means for controlling the vertical movement of the paper stacking plate and the pickup roller and feeding of the recording paper, the control means including the detection result of the detection means and the storage Compared with the information of the means, feeding of the recording paper by the pickup roller is started only when the pickup roller is at a target height position or at a position set according to the paper type. .

  According to the present invention, in the paper feed mechanism having the above-described configuration, a feed roller that transports the fed recording paper further downstream is disposed downstream of the pickup roller in the paper transport direction. It is supported by a holder that is configured to be rotatable about the rotation axis of the feed roller, and when the paper stacking plate is moved up and down by the elevating means, the pickup roller rotates upward or downward about the feed roller. It is configured to move.

  Further, the present invention is an image forming apparatus provided with the paper feed mechanism having the above-described configuration.

  According to the first configuration of the present invention, the biasing means is provided so that the downward biasing force is increased in accordance with the upward movement of the pickup roller, thereby adjusting the height position of the pickup roller. Since the pressing force of the pickup roller to the recording paper can be increased, the pressing force of the pickup roller to the recording paper can be changed according to the type of the recording paper loaded on the paper stacking plate.

  Further, according to the second configuration of the present invention, in the paper feeding mechanism of the first configuration, the control unit is used to control the lifter according to the detection result of the detection unit and the information of the storage unit. Since the height position of the pickup roller can be accurately detected by means, it is possible to reliably obtain the pressing force of the target pickup roller against the recording paper, and when the pickup roller is not at the target height position. In this case, since feeding is not started, it is possible to prevent sheet feeding defects such as non-feeding and double feeding that occur when an appropriate pressing force cannot be obtained.

  Further, according to the third configuration of the present invention, in the paper feeding mechanism having the first or second configuration, the pickup roller is supported by a holder configured to be rotatable about the rotation shaft of the feed roller. Since the pickup roller rotates in the vertical direction around the feed roller, the distance from the feed roller is kept constant even if the pickup roller rotates up and down. The recorded recording sheet is surely sent out to the feed roller.

  Further, according to the fourth configuration of the present invention, by mounting the paper feeding mechanism of any of the first to third configurations, the pressing force of the pickup roller to the recording paper can be changed, An image forming apparatus capable of stably feeding various types of paper can be provided.

  The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of an image forming apparatus including a paper feed mechanism according to the present embodiment. In this embodiment, a laser beam printer is exemplified as an example of the image forming apparatus. However, it goes without saying that the present invention can be applied to a copying machine, a facsimile machine, or the like other than the printer.

  As shown in FIG. 1, a paper feed cassette 2 that accommodates recording paper P and is configured to be detachable from the main body of the image forming apparatus 1 is provided below the image forming apparatus 1. A pickup roller 3 for sending out the recording paper P stored in the paper feeding cassette 2 is disposed above the paper feeding cassette 2, and the recording paper sent out downstream of the pickup roller 3 in the paper transport direction. A feed roller 4 that conveys P further downstream is disposed.

  In addition, the paper cassette 2 lifts the paper stacking plate 5 with the upstream end in the paper transport direction rotatably supported by the paper feed cassette 2 and the downstream end of the paper stacking plate 5 from below. A lifter 6 is provided so that the stacked recording sheets P are pressed against the pickup roller 3. A retard roller 7 is disposed so as to be in pressure contact with the feed roller 4, and the recording paper P fed by the pickup roller 3 is rolled at the nip portion between the feed roller 4 and the retard roller 7, so It is configured to prevent sending.

  Further, in the image forming apparatus 1, an image is formed on a conveyance roller pair 8, a registration roller pair 9, and a photosensitive drum 10 a that is an electrophotographic photosensitive member that conveys the recording paper P separated and fed from the paper feeding cassette 2. The image forming means 10, the scanner unit 11 for irradiating the photosensitive drum 10a with information light D based on the image information, the transfer means 12 for transferring the image formed on the photosensitive drum 10a to the recording paper P, and the transferred image A fixing unit 13 for fixing the recording paper P and a discharge roller pair 14 for discharging the recording paper P on which the image is fixed to the outside of the apparatus are provided.

  The image forming unit 10 includes the above-described photosensitive drum 10 a and at least one process unit, and is unitized as a process cartridge that is detachable from the image forming apparatus 1. Examples of the process means include a charging means for charging the photosensitive drum 10a, a developing means for developing a latent image formed on the photosensitive drum 10a, and a cleaning means for cleaning toner remaining on the surface of the photosensitive drum 10a. There is.

  In the image forming apparatus 1 having such a configuration, information light D based on image information is irradiated from the scanner unit 11 to the photosensitive drum 10a, a latent image is formed on the photosensitive drum 10a, and the latent image is developed. As a result, a toner image is formed on the photosensitive drum 10a. In synchronism with the formation of the toner image, the recording paper P is separated and fed from the paper feeding cassette 2 one by one, and is conveyed to the image forming means 10 by the conveying roller pair 8 and the registration roller pair 9, The toner image formed on the photosensitive drum 10 a constituting the forming unit 10 is transferred onto the recording paper P by the transfer unit 12. The recording sheet P after the transfer is conveyed to the fixing unit 13, the transferred toner image is fixed by the fixing unit 13, and further discharged to the outside by the discharge roller pair 14.

  Next, the paper feed mechanism according to the present embodiment will be described in detail with reference to FIGS. FIG. 2 is a schematic diagram illustrating the vicinity of the downstream portion in the transport direction of the paper feed mechanism provided in the image forming apparatus. FIG. 3 is a schematic diagram showing the vicinity of the downstream portion in the transport direction of the paper feed mechanism, similar to FIG. 2, and shows a state in which the paper stacking plate is rotated so as to increase the pressing force of the pickup roller to the recording paper. ing. As shown in FIG. 2, the paper feed mechanism according to this embodiment includes a pickup roller 3, a feed roller 4, a paper stacking plate 5, a lifter 6, and a retard roller 7.

  As described above, the sheet stacking plate 5 is rotatably supported by the sheet feeding cassette 2 at the upstream end in the sheet transport direction, and downstream of the sheet stacking plate 5 on the downstream side of the sheet stacking plate 5 in the sheet transport direction. A lifter 6 is provided that lifts the end by pressing it from below. The lifter 6 is rotatably supported by the paper feeding cassette 2 by a support shaft 6a. When the lifter 15 is rotated by the lift motor 15, the sheet stacking plate 5 is rotated upward to load the stacker. The recorded recording sheet P is lifted up to a position where it can be fed by the pickup roller 3.

  The feed roller 4 is rotatably supported on the main body of the image forming apparatus 1 by a rotation shaft 4a, and is rotated in the paper transport direction by a driving force from the paper feed motor 16. The retard roller 7 is rotatably supported on the paper feed cassette 2 by a rotating shaft 7a, and is pressed against the feed roller 4 by an urging means (not shown) to form a nip portion. Further, a torque limiter (not shown) is provided on the rotation shaft 7a of the retard roller 7, and is configured to be driven to rotate by the feed roller 4 only when a predetermined rotational force is applied.

  The pickup roller 3 is rotatably supported by a holder 17 on a rotation shaft 3a provided at the center, and rotates by the driving force of the feed roller 4 transmitted by a gear or the like (not shown) to move the recording paper P downstream. It will be sent out. In addition, the holder 17 that supports the pickup roller 3 is supported at one end of the holder 17 so as to be rotatable on the rotation shaft 4 a of the feed roller 4, whereby the pickup roller 3 moves up and down as the holder 17 rotates. It is configured to be able to. Since the holder 17 rotates about the rotation shaft 4a of the feed roller 4, the distance between the pickup roller 3 and the feed roller 4 is kept constant.

  Further, the holder 17 is integrally formed with a pressing plate 17a extending upstream in the paper transport direction at an end opposite to the end supported by the rotating shaft 4a, and is attached above the pressing plate 17a. A compression spring 18 as a biasing means is disposed. The compression spring 18 is in a free length state when the holder 17 is in a position rotated to the lower limit. When the holder 17 is rotated upward, the compression spring 18 is compressed by the pressing plate 17a, An urging force corresponding to the amount of compression is applied to the pressing plate 17a, and the holder 17 is urged downward.

  Therefore, as described above, when the paper stacking plate 5 is rotated upward by the lifter 6, the recording paper P is lifted up to a position where the recording paper P can be fed. However, as shown in FIG. Is not in contact with the compression spring 18, the pressing force of the pickup roller 3 against the recording paper P is only the pressing force due to the weight of the pickup roller 3, the holder 17, and the pressing plate 17a. It has become. If the pressing plate 17a is in contact with the compression spring 18 in a free length state with the pickup roller 3 at the lowest point, the urging force proportional to the amount by which the pressing plate 17a is pushed up by the lifter 6 is used. Is preferable because it can be imparted.

  Here, when the paper stacking plate 5 is further rotated upward by the lifter 6, the pickup roller 3 is pushed up by the recording paper P and the holder 17 is rotated upward. As shown in FIG. The compression spring 18 is compressed by 17a. As a result, the pressing force of the pickup roller 3 against the recording paper P is increased by the urging force corresponding to the compression amount of the compression spring 18, so that the pickup roller 3 is rotated as the holder 17 is rotated upward. The pressing force can be increased.

  In addition, a detecting means 19 having a plurality of sensors 19a is arranged on the rotation path of the pressing plate 17a, and thereby the height position of the pressing plate 17a can be detected stepwise. ing. Since the compression amount of the compression spring 18 is determined by the height position of the pressing plate 17a, the detection unit 19 detects the pressing force of the pickup roller 3 on the recording paper P. As the sensor 19a, an optical sensor such as a photo interrupter or a physical sensor such as an actuator switch can be used.

  Further, the main body of the image forming apparatus 1 is provided with an operation panel 20 and a ROM 21. The operation panel 20 is configured to input and set various types of information such as the type, thickness, and size of the recording paper P stored in the paper feed cassette 2, and the main body of the image forming apparatus 1 so that the user can easily operate it. Is provided on the exterior surface. The ROM 21 is a storage unit that stores the pressing force of the pickup roller 3 suitable for feeding various types of recording paper P and the height position of the pressing plate 17a that can obtain the pressing force.

  Furthermore, the image forming apparatus 1 main body is provided with a control means 22. The control means 22 detects the height position of the pressing plate 17a by the detection means 19 based on the information input from the operation panel 20, and drives the lift motor 15 by comparing with the condition stored in the ROM 21 in advance. Alternatively, the paper feed motor 16 is driven only when it is stopped and the condition is met.

  Next, the sheet feeding operation of the sheet feeding mechanism according to the present embodiment will be described according to the steps in FIG. 5 with reference to FIGS. FIG. 5 is a flowchart showing the operation of the paper feed mechanism of the present invention.

  First, before starting image formation, the user operates the operation panel 20 to input various information such as the type, thickness, and size of the recording paper P stored in the paper feed cassette 2 (step S1). The means 22 is a pressing plate that can obtain the pressing force to the recording paper P of the pickup roller 3 suitable for feeding the stored recording paper P and the pressing force based on the inputted various information. The height position of 17a is called from the ROM 21.

  Next, when image formation is started by the user (step S2), the control means 22 drives the lift motor 15 and rotates the paper stacking plate 5 by the lifter 6, and as shown in FIG. P is lifted to a position where it can be fed by the pickup roller 3. At this time, the detection means 19 detects the height position of the pressing plate 17a, and transmits the detection result to the control means 22 (step S3).

  The control means 22 compares the detection result received from the detection means 19 with the height position of the pressing plate 17a suitable for paper feeding obtained from the ROM 21, and determines whether or not the pressing plate 17a is at the target position. If the pressing plate 17a is not at the target height position (step S4), the lift motor 15 is driven (step S5), the sheet stacking plate 5 is rotated by the lifter 6, and the pressing plate 17a is used as the target. The holder 17 is rotated so as to be positioned at the height of.

  Then, after rotating the holder 17, the height position of the pressing plate 17a is detected again by the detecting means 19, and when the pressing plate 17a is not at the target height position, the lift motor 15 is driven again. On the other hand, when the height position of the pressing plate 17a detected by the detection means 19 is at the target position, the control means 22 drives the paper feed motor 16 to rotate the pickup roller 3 and the feed roller 4 to perform recording. The feeding of the paper P is started (step S6).

  When the pickup roller 3 and the feed roller 4 are rotationally driven in the paper transport direction by the paper feed motor 16, the retard roller 7 is in direct contact with the feed roller 4, and the frictional force of the contact portion is strong, and the retard roller 7 Since a torque greater than a predetermined value is applied, the torque limiter acts and the retard roller 7 is rotated by the feed roller 4. As a result, the recording paper P delivered by the pickup roller 3 smoothly enters the nip portion between the feed roller 4 and the retard roller 7.

  When a plurality of recording papers P are simultaneously fed to the nip portion by the pickup roller 3, the frictional force between the recording papers P is small, and a predetermined or higher rotational force is applied from the feed roller 4 to the retard roller 7. Therefore, the torque limiter does not act and the retard roller 7 does not rotate following the feed roller 4. As a result, only the uppermost recording sheet P in contact with the feed roller 4 is transported to the downstream side.

  The recording paper P conveyed downstream by the feed roller 4 and the retard roller 7 forms an image by the image forming means 10 or the like as described above. Finally, it is determined whether or not the image forming process has been completed by the control means 22 (step S7). If the process is continued, the process returns to step S3 and the same procedure is repeated (steps S3 to S7).

  In addition, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the meaning of this invention. For example, in the above-described embodiment, the compression spring 18 is used as the urging unit. However, a plate spring or a torsion spring may be used, or a tension spring that pulls downward may be used. It is also possible to increase the pressing force in advance by attaching a weight or the like to the tip of the pressing plate 17a. Further, in the above-described embodiment, various types of information are input using the operation panel 20, but may be configured to be input via an external interface such as a personal computer.

  In the above embodiment, the pickup roller 3 is supported by the holder 17 whose one end is rotatably supported by the rotation shaft 4 a of the feed roller 4. For example, the pickup roller 3 is not provided with the holder 17. The pressing force may be adjusted by bringing the urging means directly into contact with the rotary shaft 3a. Furthermore, in the above embodiment, the paper stacking plate 5 that rotatably supports the upstream end portion in the paper transport direction and the lifter 6 that presses and lifts the downstream end portion of the paper stacking plate 5 from below are provided. Although the paper feed mechanism using the paper cassette 2 has been described, this is configured so that, for example, the paper stacking plate is suspended and supported by a plurality of wires, and the paper stacking plate can be moved up and down horizontally by winding up the wires. It is also possible to use a new paper cassette.

  The present invention can be used in a paper feeding device provided in an image forming apparatus such as a printer. In particular, the paper stacked on the paper storage unit is fed by a feeding unit provided above the paper storage unit. It can be used for a paper feeder.

FIG. 1 is a schematic configuration diagram of an image forming apparatus including a paper feed mechanism according to the present embodiment. FIG. 4 is a schematic diagram illustrating a periphery of a downstream portion in a transport direction of a paper feed mechanism provided in the image forming apparatus. FIG. 4 is a schematic diagram showing the vicinity of the downstream portion in the transport direction of the paper feed mechanism, similarly to FIG. 2, and shows a state in which the paper stacking plate is rotated so as to increase the pressing force of the pickup roller to the recording paper. . These are flowcharts showing the operation of the paper feed mechanism of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 3 Pickup roller 3a Rotating shaft 4 Feed roller 4a Rotating shaft 5 Paper loading plate 6 Lifter (lifting means)
6a support shaft 7 retard roller 7a rotating shaft 15 lift motor (lifting means)
16 Feeding motor 17 Holder 17a Pressing plate 18 Compression spring (biasing means)
19 Detection means 19a Sensor 20 Operation panel 21 ROM (storage means)
22 Control means P Recording paper

Claims (4)

A sheet stacking plate on which recording sheets configured to move up and down are stacked, an elevating means for moving the sheet stacking board up and down, and abutting at a predetermined pressure on the top of the recording sheets stacked on the sheet stacking plate In a paper feed mechanism having a pickup roller that can move in the vertical direction for feeding recording paper,
The urging means for urging the pickup roller downward is provided so that the urging force is increased in accordance with the upward movement of the pickup roller, and the pickup roller is adjusted by adjusting the height position of the pickup roller. A paper feed mechanism characterized in that the pressing force of the roller against the recording paper can be adjusted. Detection means for detecting the height position of the pickup roller, storage means for storing the urging force of the urging means applied to the pickup roller in accordance with the height position of the pickup roller, and the sheet stacking plate And a control means for controlling the vertical movement of the pickup roller and feeding of the recording paper,
The control means compares the detection result of the detection means with the information in the storage means, and only when the pickup roller is at a target height position or at a position set according to the paper type. 2. The paper feeding mechanism according to claim 1, wherein the feeding of the recording paper is started.   A feed roller that conveys the fed recording paper further downstream is disposed downstream of the pickup roller in the sheet conveyance direction, and the pickup roller is configured to be rotatable about the rotation axis of the feed roller. The pick-up roller is configured to rotate upward or downward about the feed roller when the sheet stacking plate is moved up and down by the elevating means. The sheet feeding mechanism according to claim 1 or 2.   An image forming apparatus comprising the paper feed mechanism according to claim 1.

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