JP2002179254A - Sheet feeding device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a feeding device sufficiently having both high feeding performance and low cost, and an image forming device having it. SOLUTION: Typical structures of the sheet feeding device and the image forming device comprise an oscillatable intermediate plate for loading and supporting a plurality of sheets, a feeding means for feeding the loaded sheets, an energizing member for energizing the intermediate plate toward the feeding means, and an intermediate plate controlling means for moving the intermediate plate to switch between abutting and separating of the feeding means for the upper surface of the loaded sheets. The intermediate plate controlling means comprises a locking means for holding the intermediate plate in a separating state of the upper surface of the sheets from the feeding means, a releasing means for releasing the holding of the intermediate plate by the locking means, and a separating means for moving the intermediate plate in the separating direction from the feeding means by a predetermined distance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for forming an image on a sheet, and more particularly to a sheet feeding apparatus for feeding a sheet.

[0002]

2. Description of the Related Art In an image forming apparatus for forming an image on a sheet-like recording medium, there is a case where a sheet feeding device for separating and feeding one by one from a large number of stacked sheets is provided. Many. A conventional retard separation type sheet feeding apparatus will be described with reference to FIG.

In FIG. 1, a sheet S stacked in a storage 100 is conveyed downstream by a pickup roller 102 capable of controlling the separation and contact of the sheet S by a solenoid 106. Downstream of the pickup roller 102, a separation / conveyance mechanism including a feed roller 103 and a separation roller 104 that abuts and presses the feed roller 103 is disposed. Feed roller 103
Is rotationally driven in the transport direction so as to send out the sheet S,
The separation roller 104 is attached via a torque limiter (not shown) to a separation drive shaft that rotates in a direction to push the sheet S back to the storage 100. Thus, when a plurality of sheets S are nipped between the nip portions of both rollers, excess sheets are pushed back to the storage 100, and double feeding is prevented beforehand.

Next, a series of operations of the feeding device will be described. When the storage is mounted on the image forming apparatus main body, the drive of the lifter motor 105 is transmitted to a lifter (not shown),
In response, the middle plate 109 in the storage 100 pushes up the sheet S. When the upper surface position of the sheet S reaches an appropriate feeding position, the output of the sheet detection sensor 108 turns ON, and the driving of the lifter motor 105 stops, and the sheet can be fed. In the feeding operation, first, the solenoid 106 is turned off.
By performing F, the pickup roller 102 comes into contact with the upper surface of the sheet. Next, the drive is transmitted to each roller, and the sheet S is conveyed to the downstream side. The leading end of the sheet S is the feed roller 10
When the sheet S is passed through the nip between the roller 3 and the separation roller 104, the conveyance of the sheet S is taken over from the pickup roller 102 to the feeding roller 103. Therefore, the solenoid 106 is turned on, and the pickup roller 102 is retracted from the surface of the sheet S.

[0005]

In the above-described conventional feeding apparatus, high feeding performance is realized,
A sheet detection sensor 108 for stabilizing the sheet height at the time of feeding and a lifter motor 105 for lifting the paper surface are required. Further, the mechanism becomes complicated, for example, a pickup roller 102 that can be moved up and down must be provided exclusively for the pickup operation, so that the cost must be increased.

In contrast to the above-described high-performance and high-cost feeding system, a conventional low-cost feeding device employs a separation pad system using a half-moon-shaped feeding roller 122 as shown in FIG. Widely used. Unlike the previous example, this feeding device does not detect or adjust the sheet height, and
The sheet S is always fed by the action of the biasing spring 121.
It is pressed and contacted to the 22 side. The feeding roller 122 has a half-moon shape, and a freely rotatable abutting roller 123 is arranged on both sides thereof. In the feeding standby state, the notched portion of the feeding roller 122 faces the sheet, so that the abutting roller 123 contacts the sheet, and the feeding roller 122 does not contact the sheet S.

When the drive is transmitted to the feed roller 122 and the roller portion of the feed roller 122 contacts the sheet, the sheet is picked up. Thereafter, the separation of the sheet is performed by the separation pad 120 which is in pressure contact with the outer periphery of the feeding roller 122, and the sheet is conveyed downstream. This configuration solves the cost problem,
During the feeding operation, since the middle plate 109 is always in pressure contact with the feeding roller, the separation resistance of the sheet is extremely large, and in terms of feeding performance such as double feeding resistance, the retard separation method is used. Greatly inferior to

As a feeding device having no pickup roller and having improved feeding performance, there is a separation pad system having an intermediate plate lifting mechanism widely used for a manual feeding portion. Its configuration is almost the same as that of the middle plate constantly pressurized described above, except that the feeding roller is a perfect circle, and the middle plate has two states of a pressurized state and a retracted state during the feeding operation. Can be taken.

In such a configuration, the pressurization of the middle plate can be released after the sheet pick-up is completed, so that the sheet separating performance can be greatly improved as compared with the configuration in which the sheet is constantly pressurized. Can be. However, since the position of the middle plate in the retracted state is determined by design irrespective of the number of stacked sheets, the moving distance of the middle plate becomes larger as approaching the last sheet compared to when the sheet is full, and the feeding timing is unstable. Becomes For this reason, it cannot be applied to a large-capacity feeding device such as a cassette feeding device.
It is said that the upper limit is about 100 sheets.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a feeding apparatus capable of sufficiently satisfying both high feeding performance and low cost, and an image forming apparatus having the same.

[0011]

In order to solve the above-mentioned problems, a typical configuration of a sheet feeding apparatus and an image forming apparatus according to the present invention is a swingable swingable apparatus for stacking and supporting a plurality of sheets. A middle plate, feeding means for sending out the stacked sheets, a biasing member for biasing the middle plate toward the feeding means, and the feeding means for the upper surface of the stacked sheets And a middle plate control means for moving the middle plate so as to switch the contact and separation of the middle plate, wherein the middle plate control means holds the middle plate in a state where the upper surface of the sheet is separated from the feeding means. Stopping means, releasing means for releasing the holding of the middle plate by the locking means, and separating means for moving the middle plate by a predetermined amount in a direction away from the feeding means. And

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] A first embodiment of a sheet feeding apparatus and an image forming apparatus according to the present invention will be described. FIG. 1 is a schematic configuration diagram of a sheet feeding device according to the present embodiment, FIG. 2 is a developed view of a driving mechanism of the sheet feeding device,
FIG. 3 is an exploded perspective view illustrating a part of the driving mechanism, FIG.
5 and 6 are diagrams illustrating the operation of the drive mechanism, FIG. 7 is a timing chart illustrating the operation of the sheet feeding device during the feeding operation, and FIG. 8 is a diagram illustrating the entire configuration of the image forming apparatus. .

(Image Forming Apparatus) First, the entire image forming apparatus will be described with reference to FIG. The image forming apparatus shown in FIG. 8 is a copying machine adopting an electrophotographic system, and has a document table 2 made of a transparent glass plate fixedly provided on an upper portion of a copying machine body 1. An original pressure plate 3 is provided on the upper part of the original platen 2, and presses and fixes an original P placed on a predetermined position of the original platen 2 with the original surface facing downward.

On the lower side of the document table 2, an optical system comprising a lamp 4 for illuminating the document P, reflecting mirrors 5 to 10 for guiding a light image of the illuminated document P to the photosensitive drum 12, and an imaging lens 11. A system is provided. Note that the lamp 4 and the reflection mirrors 5 to 7 move at a predetermined speed in the direction of arrow a in FIG. An optical latent image is formed by irradiating a uniformly charged photosensitive drum 12 with a light image from this optical system.

The image forming section is a photosensitive drum 12 as an image carrier.
A charging device 13 for uniformly charging the surface of the photosensitive drum 12, a developing device 14 for developing an electrostatic latent image formed on the photosensitive drum 12 by the optical system, and a developing device 14 for developing on the photosensitive drum 12. A transfer charger 19 for transferring the transferred toner image onto the sheet S, a separator 20 for separating the sheet S from the photosensitive drum 12, a cleaner 26 for removing residual toner on the photosensitive drum 12 after transferring the toner image, and the like. ing.

A plurality of feeding cassettes 30a to 30d for stacking and storing sheets S to be fed are detachably provided at the lower portion of the copying machine main body 1, and each of the feeding cassettes 30a to 30d is a feeding unit which is a sheet feeding device to be described later. 31a to 31d are provided. The sheet S fed by the feeding unit 31 is conveyed in synchronism with the toner image on the photosensitive drum 12 by the registration roller pair 18, and is conveyed to the fixing device 22 by the conveying unit 21 as conveying means. In the fixing device 22, the toner image is permanently fixed on the sheet S by applying heat and pressure, and is discharged and stacked on a discharge tray 25 outside the apparatus by a discharge roller 24.

(Sheet Feeding Apparatus) Next, the configuration of the sheet feeding apparatus will be described. As shown in FIG. 1, the feeding cassette 30 includes a middle plate 67 that supports the bottom surface of the stacked sheets S, a lifter (biasing member) 65 for lifting the sheet S through the middle plate 67, A lifter spring 66 is provided to apply a biasing force when the lifter 65 lifts the sheet S.
The lifter 65 is rotatably supported around a shaft 65a serving as a fulcrum, and a lifter gear 70 is mounted coaxially.

A feeding roller (feeding means) 60 and a separation roller facing the feeding roller 60 are provided at the front edge of the feeding cassette 30 in the feeding direction.
61 are provided. Separation roller gear of separation roller shaft 64
The feed roller gear 55 between the feed roller shaft 57 and the feed roller shaft 62 is an idler gear.
The sheet S is driven and connected via 56 (see FIG. 2), and rotates in a direction to push the sheet S back to the feeding cassette 30 during feeding.
The separation roller 61 is attached to a separation roller shaft 64 via a torque limiter 63. When only one sheet S is held between the nip between the feeding roller 60 and the separation roller 61, the separation roller 61 is taken along the sheet S. Follows in the transport direction,
When double feeding occurs, the double feeding sheet acts to be pushed back to the feeding cassette 30.

As shown in FIG. 2, the driving mechanism of the sheet feeding device includes a clutch cam 50, a clutch gear 51, a feeding driving gear 52, and a middle plate separating gear (separating means) rotatably supported by the feeding unit 31. ) 53, controlled by a rotatable middle plate pressing cam (release means) 54. These gears and cams are all integrated, and each time the solenoid 75 is turned on,
It rotates and performs a predetermined control, and returns to the initial state. Hereinafter, these gears and cams are collectively referred to as a control gear train.

The flapper of the solenoid 75 is the clutch cam 50
In a state where the rotation of the control gear train is stopped by engaging with the control gear train (hereinafter referred to as a standby state), the control gear train is urged in the rotational direction by an urging spring (not shown). Also clutch gear
For 51, as shown in FIG.
The part facing the motor gear 77 of 76 is missing teeth,
The drive of the feed motor 76 is not transmitted to the control gear train until the solenoid 75 is turned on and the teeth of the clutch gear 51 are engaged with the motor gear 77. As shown in FIG. 3, the feed drive gear 52 has a missing tooth at a position facing the feed roller gear 55 in the standby state. Therefore, in the standby state, the feed roller 60 bears the load of the torque limiter 63 but can rotate freely. The relationship between the feed drive gear 52 and the feed roller gear 55 will be described later.

(Medium Plate Elevating Mechanism) As shown in FIG. 4, the intermediate plate elevating mechanism, which is the essence of the present invention, engages with a lifter gear 70 provided at the end of a lifter 65 and a lifter gear 70 to reduce the driving speed. Lifter drive gears 71a, 71b, ratchet gear 72 integrally formed with lifter drive gears 71a, 71b,
And a stopper (locking means) 73 that bites into the ratchet gear 72 to prevent the lifter 65 from rising.

First, the middle plate pressing operation will be described with reference to FIG. The stopper 73 is urged by a spring (not shown) in a direction to bite into the ratchet gear 72, and the ratchet gear 72 is urged in a direction to bite into the stopper 73 by the action of the lifter spring 66. Is stationary, and the positions of the lifter 65 and the middle plate 67 are also kept constant. When the solenoid 75 is turned on and the rotation of the control gear train starts (FIG. 5 (a)), the middle plate pressing cam 54 is eventually stopped by the stopper.
73 is separated from the ratchet gear 72 (FIG. 5 (b)). Then, since there is no thing that suppresses the biasing force of the lifter spring 66,
The lifter 65 rises, and the middle plate 67 presses the sheet S against the feed roller 60 (FIG. 5C).

Next, the operation of separating the middle plate will be described with reference to FIG. The intermediate plate separation gear 53 located at a position facing the lifter drive gear 71a has a gear portion only on a part of the circumference, but the other regions are missing teeth. The middle plate separation gear 53 rotates (FIG. 6 (a)), and the gear part is the lifter drive gear 71b.
, The middle plate separation gear 53 rotates the lifter driving gear 71b in the direction in which the lifter 65 is lowered while opposing the urging force of the lifter spring 66 (FIG. 6 (b)). At this time, the ratchet gear 72 also rotates together with the lifter driving gear 71b,
Since the rotation is in the opposite direction to the lock direction by the stopper 73, the stopper 73 escapes while riding over the ratchet shape. When the lifting of the middle plate separation gear 53 by the lifter is completed, the stopper 73 and the ratchet gear 72 are engaged at that position.
The positions of 65 and the middle plate 67 are maintained as they are (FIG. 6 (c)).

The amount of retreat of the middle plate 67 separating from the feed roller 60 can be freely set by the ejection of the middle plate separation gear 53. Further, the ratchet gear 72 and the lifter 65 are in phase with each other, and when the angle of the lifter 65 is below the lower limit position in design, not shown, but corresponds to the stopper 73 on the ratchet gear 72. Since the ratchet shape is not provided, the lifter 65 does not drop too much.

The driving of the feed roller 60 is controlled by a feed drive gear 52 of a control gear train. As described above, the feed driving gear 52 includes a toothless portion (including a region facing the feed roller gear 55 in a standby state) for cutting off the drive transmission to the feed roller 60, and the feed roller 60. And a gear portion for transmitting the drive to the motor. The number of teeth of the gear portion is set so that the feeding roller 60 can convey the sheet S with a margin from the feeding cassette 30 to a conveying roller (not shown) downstream of the feeding roller. Since the feed roller 60 and the separation roller 61 are drivingly connected by the idler gear 56, one rotation control of the control gear train is completed, the process returns to the standby state, and the drive is transmitted from the feed drive gear 52 to the feed roller gear 55. Even after the sheet S is pulled out, the separation roller shaft 64 rotates in the direction of pushing the sheet S back to the feed cassette 30 as a reaction to rotate the feed roller 60 in the forward direction while the sheet S is pulled out by the downstream transport roller. I do. As a result, the separation roller 61 continues the separation operation until the sheet S is completely pulled out from the nip between the feed roller 60 and the separation roller 61.

The individual operation of each mechanism described above will be described in the order of a series of feeding operation timings. FIG.
9 is a timing chart illustrating the state of the middle plate 67 and the feeding roller 60 during the feeding operation together with the operating states of the gears and the cams constituting the control gear train.

When the solenoid 75 is turned on and the control gear train starts rotating (t1), first, the intermediate plate pressing cam 54 is
73 is removed (t2), and the intermediate plate 67 presses the sheet S against the feed roller 60 (t3). After the pressurization of the sheet S is completed, the gear portion of the feed drive gear 52 meshes with the feed roller gear 55, and the feed roller 60 rotates to pick up the sheet S (t4). When the leading end of the sheet S has passed the nip portion between the feed roller 60 and the separation roller 61, the middle plate separation gear 53 rotates the lifter drive gear 71b (t5), and the middle plate 67 is moved from the feed roller 60. Separate.

Thereafter, the feeding roller 60 conveys the sheet S to the downstream conveying roller, and after the drive input from the feeding driving gear 52 is completed (t6), the sheet S is pulled out by the downstream conveying roller. Until the sheet S (t8) is reached, the user follows the sheet S. When the one-rotation control ends (t7), the control gear train stops rotating and enters a standby state because the flapper of the solenoid 75 and the projection of the clutch cam 50 are engaged.

As described above, in the present embodiment, the drive mechanism from the feed motor 76 to the control gear train and the drive mechanism downstream from the control gear train are divided, and the former is on the feed unit 31 side, and the latter is on the feed unit 31 side. It is configured on the feed cassette 30 side. Therefore, in the drive transmission portions of the two, the toothless portions on the control gear train side always face the respective gears on the side of the feed cassette 30 in the standby state, so that when the feed cassette 30 is attached or detached, the tooth tips of the two may not interfere. Absent.

Further, the user inserts the sheet S into the feeding cassette 30.
When the sheets are stacked, the sheets S can be easily supplied by setting the sheets S so that the middle plate 67 is pushed down. This is because when the middle plate 67 is pushed down, the stopper 73 engages with the ratchet gear 72 in that state, and the height of the middle plate 67 is maintained at that position.

[Second Embodiment] A second embodiment of the sheet feeding apparatus and the image forming apparatus according to the present invention will be described. FIG. 9 is a schematic configuration diagram of a sheet feeding device according to the present embodiment, and FIG. 10 is a developed view of a driving mechanism of the sheet feeding device. And the description is omitted.

In the first embodiment, the feeding motor
Only the feed gear unit 76 and the control gear train are arranged on the feed unit 31 side, and feeds driven parts such as the middle plate elevating mechanism including the lifter drive gears 71a and 71b and the ratchet gear 72, the feed roller 60, and the feed roller gear 55. The configuration provided on the cassette 30 has been described. On the other hand, in the present embodiment, most of these
This is an example provided on the 31 side. With such a drive arrangement, it is possible to prevent the user from directly touching the drive unit when the feed cassette 30 is pulled out from the copying machine main body. The sheet separation mechanism employs a separation pad system in which a separation pad is pressed against a feed roller to separate a sheet.

As shown in FIG. 9A, the feed roller 60 is disposed on the feed unit 31 side, but the separation pad 69 is provided on the feed cassette 30 and is fed by a link mechanism (not shown). Only when the feeding cassette 30 is at the proper position, the feeding roller 30 is pressed against the feeding roller 60, and when the feeding cassette 30 is pulled out, the pressing is released and the feeding cassette 30 is separated from the feeding roller 60.

In the drive mechanism shown in FIG.
A first lifter gear 85 is provided on a shaft 65a of the 65, and is drivingly connected to a ratchet gear 72 via a second lifter gear 86, a third lifter gear 87, and a lifter gear. Two of the first lifter gear 85 and the second lifter gear 86 are provided on the feed cassette 30 side, and the third lifter gear 87 is provided on the feed cassette 30 side. The second lifter gear 86 has a coupling portion 86a,
When the feeding cassette 30 is mounted on the copying machine main body, the feeding cassette 30 is coaxially engaged with the coupling portion 87a of the third lifter gear 87 to be drivingly connected. That is, only the first lifter gear 85 and the second lifter gear 86 are the drive mechanisms that can be attached and detached together with the feed cassette 30, and most other driven parts such as the feed roller 60, the ratchet gear 72, and the stopper 73 The side is configured. The first lifter gear 85 has a missing tooth portion,
When the angle of 65 is below the lower limit position, the missing tooth portion comes to a position facing the second lifter gear 86, so that the lifter 65
Is not broken down too much.

By the way, if the stopper 73 and the ratchet gear 72 are configured on the feed unit 31 side as in this embodiment,
When the feeding cassette 30 is pulled out of the copying machine main body and the drive connection by the coupling portions 86a and 87a is disconnected, there is no means for holding the position of the middle plate 67, and the middle plate 67 jumps up to the maximum height. For the same reason, when the user sets a sheet in the feeding cassette 30, the operation is difficult because the middle plate 67 does not lower.

In order to solve this problem, in this embodiment, a sheet pressing claw 88 is provided at the front edge of the feeding cassette 30 in the feeding direction. The sheet pressing claws 88 are arranged at two places on both sides of the feeding roller 60, and regulate the upper surface position of the sheet when the sheets are stacked.

As shown in FIG. 9A, the sheet pressing claw 88 is urged by a spring (not shown) in a direction to press the upper surface of the sheet. 67 regulates lifting of seats. The user stacks the sheets in such a manner as to push the sheets under the sheet holding claws 88, but since the sheet holding claws 88 do not need to be so large, they do not hinder the stacking.

As shown in FIG. 10 (b), when the feeding cassette 30 is inserted into the apparatus main body and comes to the proper mounting position, the projection 90 provided on the apparatus main body is moved to the lever portion of the sheet pressing claw 88.
The user pushes 88 a to rotate it, and retracts so as to sneak into the feeding guide 89. As a result, in the state where the feeding cassette 30 is mounted on the copying machine main body, the regulation of the middle plate position by the sheet pressing claw 88 is released, and the feeding operation becomes possible. Also,
When pulling out the feeding cassette 30 from the apparatus main body, the reverse operation is performed, and the position of the middle plate is regulated.

In the present embodiment, the sheet holding claw 88 is configured as described above in order to attach and detach the feeding cassette 30 in a direction perpendicular to the feeding direction. However, for example, if it is configured to be attached and detached in the transport direction as often used in printers, it is not necessary to make the sheet pressing claw 88 movable, and a fixed type loading upper claw is provided on a member for regulating the sheet width direction. Just do it.

[Other Embodiments] The sheet feeding apparatus and the image forming apparatus according to the present invention are not limited to the structures of the above embodiments. For example, instead of the stopper 73 and the intermediate plate pressing cam 54, , Directly ratchet gear 75
It may be made to engage with 72. Also, rather than pressurizing the middle plate 67 via the lifter 65, the lifter gear 70
By providing an elevating member as described above, a configuration in which the intermediate plate 67 is directly pressed may be employed. Further, in the present embodiment, the description has been given by using the rotating middle plate 67 as an example. However, for example, a middle plate configuration that lifts up vertically while keeping the angle of the sheet stacking surface constant may be used.

Similarly, the configuration around the feed roller 60 is not limited to the above embodiments, and any separation mechanism may be employed. Either side may be provided. Also, a pickup roller is arranged upstream of the feed roller 60,
The configuration may be such that the sheet is pressurized by 67 not on the feed roller 60 but on a pickup roller as feeding means.

[0042]

According to the structure described above,
In the sheet feeding apparatus and the image forming apparatus according to the present invention, it is said that, when picking up a sheet, the middle plate is pressed against the feeding roller, and after the completion of the pickup, the middle plate is retracted to facilitate the separation of the sheet. The lifting and lowering control of the middle plate can be stably performed with a very simple and low-cost mechanism. As a result, the role of the pickup roller in the conventional feeding device can be performed by the feeding roller and the intermediate plate, and the pickup roller can be eliminated. Also, after the pickup is completed, the pressurization by the middle plate is released, so the sheet separation resistance can be extremely reduced compared to the conventional configuration using a half-moon feed roller, and the double feed resistance is greatly improved. Could be improved.

Further, unlike the conventional sheet feeding apparatus in which the sheet height is adjusted by a sheet detection sensor, a mechanical structure is employed in which the sheet is separated by a predetermined amount from the position where the sheet comes into contact with the sheet feeding means. This eliminates the need for a sheet detection sensor and eliminates the need for a lifter motor for lifting the middle plate. Thus, it is possible to greatly simplify the apparatus and reduce the cost without impairing the feeding performance.

Further, since the distance between the upper surface of the sheet and the feeding means at the time of separation of the middle plate is always constant and the distance can be kept to a necessary minimum irrespective of the number of stacked sheets, the mechanism is simple. Nevertheless, it is possible to perform an accurate operation that can cope with high-speed feeding.

Further, as compared with the feeding device having the middle plate elevating mechanism used in the conventional manual feeding device, the middle plate is retracted by a predetermined amount from the position at the time of pressurization. In addition, the moving distance during the elevating operation is extremely small, and it is possible to sufficiently cope with large-capacity loading while maintaining the feeding stability.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a sheet feeding device according to a first embodiment.

FIG. 2 is a development view of a driving mechanism of the sheet feeding device.

FIG. 3 is an exploded perspective view illustrating a part of a driving mechanism.

FIG. 4 is a side view of the driving mechanism of the sheet feeding apparatus as viewed from the back side of the apparatus.

FIG. 5 is a diagram for explaining the operation of the drive mechanism.

FIG. 6 is a diagram illustrating the operation of a drive mechanism.

FIG. 7 is a timing chart illustrating an operation of the sheet feeding apparatus during a feeding operation.

FIG. 8 is a diagram illustrating an overall configuration of an image forming apparatus.

FIG. 9 is a schematic configuration diagram of a sheet feeding device according to a second embodiment.

FIG. 10 is a development view of a driving mechanism of the sheet feeding device.

FIG. 11 is a diagram illustrating a conventional sheet feeding apparatus of a retard separation type.

FIG. 12 is a diagram illustrating a conventional separation pad type sheet feeding apparatus.

[Explanation of symbols]

 P: Original S: Sheet 1: Copy machine body 2: Original platen 3: Original cover plate 4: Lamp 5-10: Reflecting mirror 11: Imaging lens 12: Photosensitive drum 13: Charger 14: Developing device 18: Registration roller Pair 19: Transfer charger 20: Separator band 21: Transport unit 22: Fixing unit 24: Discharge roller 25: Discharge tray 26: Cleaner 30: Feed cassette 31: Feed unit 50: Clutch cam 51: Clutch gear 52: Feed drive gear 53… Medium plate separation gear 54… Medium plate pressing cam 55… Feed roller gear 56… Idler gear 57… Separation roller gear 60… Feed roller 61… Separation roller 62… Feed roller shaft 63… Torque limiter 64… Separating roller shaft 65 ... Lifter 65a ... Shaft 66 ... Lifter spring 67 ... Middle plate 69 ... Separation pad 70 ... Lifter gear 71a ... Lifter drive gear 71b ... Lifter drive gear 72 ... Ratchet gear 73 ... Stopper 75 ... Solenoi 76 ... feeding motor 77 ... motor gear 85 ... first lifter gear 86 ... second lifter gear 86a ... coupling part 87 ... third lifter gear 87a ... coupling part 88 ... sheet pressing claw 88a ... lever part 89 ... feeding guide 90 ... projection Department

Claims (8)

[Claims] 1. A swingable middle plate for stacking and supporting a plurality of sheets, feeding means for sending out the stacked sheets, and attaching the middle plate toward the feeding means. A biasing member for biasing, and a middle plate control unit that moves the middle plate so that the contact of the feeding unit with the upper surface of the stacked sheets is switched, and the middle plate control unit includes: Locking means for holding the middle plate in a state where the upper surface of the sheet is separated from the feeding means; releasing means for releasing the holding of the middle plate by the locking means; and A sheet feeding device having a separating means for moving a predetermined amount in a separating direction. 2. The locking means comprises: a ratchet gear that rotates or slides in conjunction with the position of the middle plate; and a stopper that locks the position of the middle plate by engaging with the ratchet gear. The sheet feeding device according to claim 1, wherein: 3. The releasing means is a rotatable cam, and the stopper is released from engagement with the ratchet gear by pushing the stopper in the course of rotation of the releasing means, so that the feeding of the intermediate plate is performed. 3. A sheet feeding apparatus according to claim 2, wherein said sheet feeding apparatus is urged in a direction in which said means comes into contact with said means. 4. The separation means is a toothless gear having teeth only on a part of the circumference, and a gear portion of the toothless gear is engaged with a gear interlocked with the intermediate plate, 2. The sheet feeding device according to claim 1, wherein the intermediate plate is moved in a direction away from the feeding unit by a predetermined amount set by the number of teeth. 5. The operation of the canceling means and the separating means are synchronized, and pressurization and separation of the intermediate plate are switched at a predetermined timing every time a control instruction is given. The sheet feeding device according to any one of claims 1 to 4. 6. The middle plate control means is synchronized with the drive control of the feeding means, and operates the middle plate and the feeding means at a predetermined timing each time a feed start instruction is given. The method according to claim 1, wherein
The sheet feeding device according to any one of the preceding claims. 7. The predetermined timing at which the middle plate control unit and the feeding unit operate are as follows: the release unit releases the holding of the middle plate by the locking unit; 7. The sheet feeding apparatus according to claim 6, wherein the separating unit separates the middle plate from the feeding unit, and the feeding unit stops rotating. 8. An image forming apparatus comprising: the sheet feeding device according to claim 1; an image forming unit configured to form an image on a sheet; and a conveying unit configured to convey the sheet. apparatus.