JPH07144771A - Sheet feeder and image forming device - Google Patents

Abstract

PURPOSE:To provide a sheet feeder by which cost can be reduced and an installing characteristic can be improved and the occurrence of a malfunction or the like can be prevented. CONSTITUTION:A solenoid is actuated by a paper feed signal, and a tooth lacking gear 12b and a driving gear 13 are meshed with each other, and a cam part 12a is rotated, and swings a lift-up lever 10. Thereby, a pickup roller 3 is lowered, and comes into contact with the uppermost sheet position and sends out a sheet S. When the cam part 12a is further rotated, the pickup lever 10 raises a shaft 6, and separates the pickup roller 3 from the sheet S. When a tooth lacking part of the tooth lacking gear 12b is opposed to the driving gear 13, transmission of driving is cut off, and a sheet feeder is put in a standby condition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet feeding device provided in an image forming apparatus such as a printer, a copying machine or a facsimile, and more particularly to a lifter for keeping the height of the uppermost sheet substantially constant. The present invention relates to a sheet feeding device provided with a mechanism.

[0002]

2. Description of the Related Art A sheet feeding apparatus provided in an image forming apparatus is provided with a lifter mechanism for keeping the uppermost height of stacked sheets substantially constant, and the sheet is fed from a constant height. There is one that is fed by a feeding means such as a paper roller.

In this type of lifter mechanism, the control for keeping the uppermost height of the seat constant has hitherto been performed by bringing a lever into contact with the uppermost surface of the seat, and the displacement of the lever is electrically detected by a photosensor or the like. The detection is performed by a sensor, and based on this detection, an electric actuator such as a dedicated motor, an electromagnetic clutch, and a powerful solenoid for raising and lowering a mounting table on which sheets are stacked is appropriately driven.

Further, in the conventional sheet feeding device,
There is one in which the feeding means is brought into contact with and separated from the uppermost sheet whose height is constant by a lifter mechanism. This is performed in order to reduce the load (back tension) applied to the sheet by separating the feeding unit from the fed sheet when one sheet is fed.

Conventionally, an electric actuator such as a dedicated motor, electromagnetic clutch or solenoid is used as a mechanism for bringing the feeding means into contact with and separating from the sheet, similarly to the lifter mechanism.

[0006]

However, the conventional sheet feeding device having the above-mentioned lifter mechanism and the mechanism for moving the above-mentioned feeding means has the following problems. 1) Since electrical sensors and actuators are used,
High cost. In addition, electric capacity is required. 2) Wiring for electrically connecting electrical sensors, actuators, etc. is increased, and wiring mistakes such as miswiring are likely to occur. 3) The control sequence of the paper feeding system becomes complicated, and it tends to cause malfunction.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a sheet feeding apparatus which is low in cost, has a good assembling property, and can prevent the occurrence of malfunctions and the like.

[0008]

SUMMARY OF THE INVENTION According to the present invention, there is provided a sheet placing means for placing a sheet, and an up and down swing for contacting and separating the uppermost sheet placed on the sheet placing means. A movably supported feed unit that feeds the uppermost sheet when it comes into contact with the uppermost sheet, and a swinging unit that swings the feeding unit to bring the sheet into contact with and separate from the uppermost sheet. The rocking means includes a missing tooth gear clutch for controlling rotation in which drive transmission is stopped when a missing tooth portion of the missing tooth gear faces the drive gear, and the missing tooth gear clutch. It is characterized by comprising a cam that interlocks with rotation transmission, and a connecting means that engages with the cam and the feeding means and swings the feeding means by the operation of the cam.

Further, the sheet feeding device having the above structure is provided with a missing tooth gear clutch for controlling rotation so that transmission of rotational drive is stopped when the missing tooth portion of the missing tooth gear faces the drive gear. , The tooth-missing gear clutch is provided for position regulation with the drive gear and the tooth-missing portion facing each other, and releases the position regulation when the feeding means is lower than a predetermined first position. Then, the drive gear and the tooth-missing gear are meshed with each other to transmit the rotational drive, and when the feeding means reaches the predetermined second position, the position is controlled and the rotational drive is shut off. An operating member that swings a lift arm pawl by transmission of rotational drive controlled by the restricting means, and a ratchet gear that is provided so as to be meshable with the lift arm pawl and that rotates by the swing of the lift arm pawl,
A lift portion that raises the sheet placing means by rotation of the ratchet gear, and a sheet placing plate on which a sheet is placed is moved up and down so that the uppermost height of the placed sheet is substantially constant. You may combine the lifter mechanism hold | maintained at.

[0010]

According to the above construction, the feeding means is separated from the top of the sheet when the drive gear and the tooth-missing gear face the tooth-missing portion, and swings when the drive gear and the tooth-missing gear mesh with each other. It swings by the moving means and comes into contact with the top of the sheet and feeds the sheet.

Also, in the lifter mechanism, when the number of sheets placed on the sheet placing means decreases, the regulation releasing means releases the regulation of the regulating member, whereby the missing gear is rotated by the drive gear. By this rotation, the lift arm pawls and the ratchet gear cause the lift portion to raise the sheet placing means, and when the uppermost height of the sheet reaches a predetermined height, the regulating member again regulates the missing tooth gear to move the uppermost sheet. By stopping the height of the sheet at a predetermined position, the uppermost height of the sheet is always held at a substantially constant position.

As described above, the raising / lowering operation of the feeding means and the operation of the lifter mechanism can be controlled by the toothless gear clutch including the drive gear and the toothless gear.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the sheet feeding apparatus of the present invention will be described with reference to FIGS. FIG. 1 shows a state in which the sheet cassette 4 is about to be attached to the apparatus main body from the direction of the arrow.

Reference numeral 1 denotes a feed roller, 2 denotes a retard roller, and 3 denotes a pickup roller. These three rollers separate and feed the sheets S stacked and stored in the sheet cassette 4 one by one. To do.

The frame 7 is provided with a stepping motor (not shown), and the driving force from the stepping motor is the shaft 1a of the feed roller 1 and the retard roller 2
Is transmitted to the shaft 2a. The pickup roller 3 is configured so that the driving force of the feed roller 1 is transmitted via a gear train (not shown) to rotate.

The retard roller 2 is supported by a swingable support member (not shown) and can be brought into contact with or separated from the feed roller 1. The shaft 2a of the retard roller 2 is provided with a torque limiter (not shown), and the torque limiter controls the normal and reverse rotation of the retard roller 2.

Reference numeral 5 denotes a roller holder which supports the feed roller 1 and the pickup roller 3, and the roller holder 5 is swingably supported by the shaft 1a of the feed roller 1, whereby the pickup roller 3 feeds. The roller 1 is swingably supported around the shaft 1a. Reference numeral 6 denotes a pickup roller shaft (hereinafter referred to as a pickup roller shaft), which extends rightward in FIG. 1 through an elongated hole 8 formed in a frame 7.

Inside the elongated hole 8 in the frame 7, there is provided a mechanism for moving the pickup roller 3 up and down in synchronization with the mounting of the sheet cassette 4. As shown in FIGS. 3 and 4, this mechanism is composed of a lever member 40 and a spring 45 that biases the lever member 40 in the clockwise direction. The lever member 40 is formed of a metal wire rod,
A push-up portion 40a that is swingably supported by a bearing portion 7a formed integrally with the frame 7 and that pushes up the pickup roller shaft 6 that is inserted into the elongated hole 8,
The sheet cassette 4 is configured to include a contact portion 40b that is pressed when the sheet cassette 4 is attached to the apparatus main body and swings the lever member 40 against the biasing force of the spring 45.

In FIG. 1, a lift arm lever 10 is rotatably attached to a shaft 9 formed integrally with a frame 7, and the lift arm lever 10 is attached by a spring 11 attached to one end thereof. It is biased clockwise in FIG. The pickup roller shaft 6 is in contact with one end of the lift arm lever 10.
The other end of the lift arm lever 10 extends near the pickup cam 12, and the pickup cam 12 rotates to swing the lift arm lever 10. As a result, when the pickup cam 12 rotates, the pickup roller shaft 6 is moved up and down via the lift arm lever 10 to move the pickup roller 3 up and down.

The pickup cam 12 is composed of a cam portion 12a with which the lift arm lever 10 is slidably in contact, and a gear portion 12b capable of meshing with the drive gear 13. The gear portion 12b has no teeth, so-called missing teeth. It is a gear. The pickup cam 12 is biased counterclockwise in FIG. 1 by a biasing means such as a spring (not shown), and its rotation is restricted by a flapper type solenoid 14 against the biasing force of the biasing means. There is. The driving force from the main motor 15 of the apparatus main body is transmitted to the driving gear 13 via the gear 16, and the driving gear 13 is constantly rotating.

Next, the lifter mechanism adopted in this embodiment will be described in detail.

A gear 17 is rotatably supported on the frame 7, and the gear 17 is provided with a lift-up cam 18 coaxially therewith. This gear 17 is the drive gear 13
It is a toothless gear that is provided so that it can mesh with and has no teeth. Further, the gear 17 is biased counterclockwise by a biasing means (not shown).

Reference numeral 19 denotes a lift arm pawl, which is swingably supported around a shaft 20 so that a pawl portion 19a (shown in FIG. 10) is meshed with a tooth surface of a fan-shaped ratchet gear 22 by a spring 19b. Is urged by. Then, the lift arm pawl 19 swings around the shaft 20 by the rotation of the lift-up cam 18, and the fan-shaped ratchet gear 22 rotates counterclockwise in FIG. 1 one tooth at a time.

On the tooth surface of the fan-shaped ratchet gear 22, a pawl portion 21a (shown in FIG. 13) of a lift lock pawl 21 rotatably supported is biased by a spring 21b, so that the fan-shaped ratchet gear 22 rotates in the reverse direction ( (A clockwise rotation in FIG. 1) is prevented.

With this structure, the lift arm pawl 19 rotates the fan-shaped ratchet gear 22 while the lift-lock pawl 21 prevents the fan-shaped ratchet gear 22 from rotating in the reverse direction, and is integrally formed with the fan-shaped ratchet gear 22. The lift-up member 23 is raised from the opening 4a formed in the sheet cassette 4, and the sheet S in the sheet cassette 4 is lifted up by this. The sheet cassette 4 includes a swingable middle plate 4b. The sheets S are stacked on the middle plate 4b, and the lift portion 23a of the lift-up member 23 swings from below to lift the sheet. To be

The structure of the lift-up member 23 will be described with reference to FIG.

FIG. 2A shows a lift-up member 23 of a completely integrated type, in which a lift portion 23a, a fan-shaped ratchet gear 22 and a connecting shaft portion 23b for connecting the lift-up members 23a are integrally formed. The lift-up member 23 is preferably made of, for example, a resin containing glass or the like and has high rigidity.

FIG. 2B shows a fan-shaped ratchet gear 22.
The lift-up member 23 has a two-piece structure in which a resin such as a polyacetal-based resin having a necessary sliding property is used, and the lift portion 23a and the connecting shaft portion 23b are made of, for example, a resin having high rigidity, such as glass. The fan-shaped ratchet gear 22
It is positioned on the connecting shaft portion 23b by fitting the boss and the hole, and is firmly fixed by the screw 27.

Since the lift-up member 23 having the one-piece structure or the two-piece structure can withstand a large weight, it is possible to sufficiently cope with, for example, a large-sized sheet or a sheet cassette capable of stacking a large number of sheets. ing. In addition, in the case of the integrated structure, the fan-shaped ratchet gear 22
Since the phase shift between the lift section 23a and the lift section 23a does not occur, and the phase shift can be prevented as much as possible even with a two-piece structure, the height of the sheet S can be accurately controlled.

In FIG. 1, reference numeral 24 is a lifter trigger lever. The lifter trigger lever 24 is swingably supported around a shaft 9 formed integrally with the frame 7, and is urged clockwise by a spring 25 in FIG. One end of the lifter trigger lever 24 has a function as a regulating member that regulates the rotation of the tooth-chipped gear 17 integrated with the lift-up cam 18 described above, and the tooth-chipped portion of the tooth-chipped gear 17 is a drive gear. The rotation of the tooth-missing gear 17 is restricted in a state of facing the gear 13. The other end of the lifter trigger lever 24 is positioned so as to contact the shaft 6 of the pickup roller 3 when the pickup roller 3 is lowered to a predetermined height.

When the pick-up roller shaft 6 is lowered to a predetermined height, the lifter trigger lever 24 rotates and the restriction portion at one end releases the rotation restriction of the lift-up cam 18, whereby the lift-up cam 18 is lifted.
Is slightly rotated by an urging means (not shown). By this rotation, the toothless gear 17 and the drive gear 13 mesh with each other, the lift-up cam 18 rotates, and the lift-arm pawl 19 swings to rotate the fan-shaped ratchet gear 22 and lift the lift-up member 23. When the lift-up member 23 rises and the pickup roller 3 rises via the sheet S, the lifter trigger lever 24 returns to the clockwise rotation and regulates the rotation of the lift-up cam 18 again.

Reference numeral 30 is a pickup lock lever,
The spring 25 is biased clockwise in FIG. 1 to form a claw portion a and an eaves portion b having a shape protruding above the pickup roller shaft 6. The claw portion a has a function of locking the tip of the lift-up lever 10 when the lift-up lever 10 is moved to the lowest position, and the eaves portion b abuts when the pick-up roller shaft 6 rises to make the pick-up lock lever 30 spring 25. 1 is rotated counterclockwise in FIG. 1 against the urging force of the lift-up lever 10 so that the tip of the lift-up lever 10 is claw a.
It has a function of lifting the lift-up lever 10 by releasing the lift-up lever 10.

Reference numeral 31 is a photosensor for detecting attachment of the sheet cassette 4, 32 is a connecting lever, and the connecting lever 32 is swingably supported by a shaft 33.

As shown in FIG. 5, a latch claw 41 is rotatably attached to the sheet cassette 4, and the latch claw 41 is connected via a rod 47 to a handle 48 provided on the front side of the apparatus. ing. The latch claw 41 is normally biased counterclockwise by a spring 46, but a handle 48
Rotate clockwise by pulling.

The connecting lever 32 is used for the sheet cassette 4
The latch claw 41 provided at the position is fitted to swing. As shown in FIG. 5A, the connecting lever 32 is lowered when the sheet cassette 4 is not attached, and when the sheet cassette 4 is attached, the latch claw 41 is connected as shown in FIG. 5B. It fits in the lever 32 and the connecting lever 32 is rotated and raised. When the latch claw 41 and the connecting lever 32 are fitted to each other, the claw portion 41a of the latch claw 41 is engaged with the engaging portion 7b formed on the frame 7, whereby the sheet cassette 4 is fixed. A flag 32a for shielding the photo sensor 31 from light is integrally formed on the connecting lever 32, and the flag 32a is attached when the sheet cassette 4 is mounted.
Shuts off the photo sensor 31 to detect the attachment of the sheet cassette 4.

A part of the connecting lever 32 protrudes in the vicinity of the lift-up cam 18 and restricts the rotation of the lift-up cam 18 when the connecting lever 32 is located below when the sheet cassette 4 is not mounted. It is supposed to do. In this state, the lifter trigger lever 24
The lift-up cam 18 cannot rotate regardless of the position. When the seat cassette 4 is mounted and the connecting lever 32 is raised, the lift-up cam 18 is restricted in rotation by the lifter trigger lever 24.

The missing tooth gears 12b and 17 used for the pickup cam 12 and the lift-up cam 18 will be described with reference to FIGS. 6 and 7. It should be noted that FIG. 6 shows an example of a conventional toothless gear.

In the present embodiment, as shown in FIG. 7, the tooth-missing gears 12b and 17 have tooth widths of portions 12c and 17a at which they start to mesh with the driving gear 13 which is a mating gear to be meshed with each other more than other portions. It is formed so that it becomes narrower and becomes gradually narrower as it gets closer to the beginning of biting.

Further, inside of the meshing start portions 12c and 17a of the chipped tooth gears 12b and 17 with the drive gear 13, there are formed recessed portions 12d and 17b so as to buffer the impact during the meshing of the teeth. You can

With this structure, as shown in FIG. 7b (a view seen from the radial direction of FIG. 7a), even if the parallelism of the gear shafts that mesh with each other is slightly different, You can avoid collisions as much as possible. As can be seen from the comparison with the conventional missing tooth gear shown in FIG. 6, the crossing amount C of the tip line at the moment of starting the biting is compared with the crossing amount C _p of the conventional one (shown in b of FIG. 6). However, it can be understood from the fact that it is very small.

In this embodiment, the tooth width of the part where the biting starts is made narrower than that of the other parts to prevent the rigidity of the teeth of the other parts from being lowered.
It is also possible to make all the tooth portions narrower than the tooth width of the counterpart gear.

Next, the operation of the structure of the sheet feeding device will be described.

First, before the sheet cassette 4 accommodating the sheets S is mounted, the drive gear is driven by the drive force of the main motor 15 on the apparatus main body side as shown in FIGS. 1, 8 and 10a. 13 is continuously rotating, but since the toothless portions of both the pickup cam 12 and the lift-up cam 18 face the drive gear 13, the rotation transmission is restricted and the operation is stopped. There is.

The lift-up member 23 formed integrally is in the lowest position, and the pickup roller 3 is held in the highest position by the lift-up lever 10 pushing up the pickup roller shaft 6. As shown in FIG. 3A, the lever member 40
Is also maintained at a position where the pickup roller shaft 6 is lifted. At this time, as shown in FIG. 5A, the connecting lever 32 is in the lowered state, and the flag 32a does not shield the photosensor 31 from light shielding, so that the mounting of the sheet cassette 4 is not detected.

Next, the state after the sheet cassette 4 is mounted will be described.

When the sheet cassette 4 is mounted on the main body of the apparatus, as shown in FIG. 5B, the latch claw 41 of the sheet cassette 4 causes the connecting lever 32 to rotate and be lifted.
The flag 32a shields the photo sensor 31 from light and detects the mounting of the sheet cassette 4.

As shown in FIGS. 9 and 10b, when the mounting of the sheet cassette 4 is detected, the solenoid 14 operates to release the rotation restriction of the pickup cam 12.
As a result, the pickup cam 12 is slightly rotated by the biasing means (not shown), and the gear portion 1 of the pickup cam 12 is rotated.
2a and the drive gear 13 mesh with each other, the drive is transmitted, and the pickup cam 12 makes one rotation in the arrow direction. When the gears are meshed with each other, as described above, the meshing start portion 12c of the gear portion 12b, which is the tooth-missing gear, is set to be narrower than that of the drive gear 13, so that the meshing is smoothly performed and an abnormal noise such as a collision noise is generated. There is nothing to do. After one rotation, the missing tooth portion of the gear portion 12a again faces the drive gear 13 and the drive transmission is interrupted.

When the pickup cam 12 makes one rotation, the lift-up lever 10 lowers and one end thereof is caught by the claw portion a of the pickup lock lever 30 to lock the lift-up lever 10. At this time, the pickup roller 3 is lowered by its own weight or by an urging means such as a spring (not shown). This lowering causes the pickup roller shaft 6
The lower end of the lifter trigger lever 24 is released from the rotation restricting position of the lift-up cam 18 by rotating the lifter trigger lever 24. Note that the lever member 40, as shown in FIG.
Since the pickup roller shaft 6 has been moved to the position where the pickup roller shaft 6 is lowered from the lifted position, the lowering of the pickup roller shaft 6 is not restricted.

In the lift-up cam 18 whose regulation has been released, the chipped tooth gear 17 formed integrally rotates with the drive gear 13 to swing the lift arm pawl 19.
As a result, the fan-shaped ratchet gear 22 rotates counterclockwise, the lift portion 23a of the lift-up member 23 rotates, and the sheet in the sheet cassette 4 is lifted (FIG. 11).
And the state shown in FIG. 13a). Even when the gears are meshed with each other, as described above, the meshing start portion 17a of the missing tooth gear 17 is set to be narrower than the drive gear 13, so that the meshing is smoothly performed and an abnormal noise such as a collision noise is generated. Never.

When the sheet S rises, the pickup roller 3 rises, and when the pickup roller shaft 6 rises to a predetermined height, the eaves portion b of the pickup lock lever 30 is lifted to pick up the pickup lock lever 30.
Rotates counterclockwise to unlock the lift-up lever 10. At the moment when this is released, the lift-up lever 10 lifts the pickup roller 3 to the most raised state by the action of the spring 11 and puts the apparatus in a standby state in which sheet feeding is possible (see b in FIGS. 12 and 13). State shown).

Thereafter, as shown in FIG. 14, the pickup cam 12 is rotated by operating the solenoid 14 in conjunction with the sheet feeding start signal, and the lift-up lever 10 is swung to pick up the pickup roller shaft 6. However, since the pickup roller 3 does not lower to a position lower than the height (top surface) of the sheet S, the pickup roller shaft 6 causes the pickup lock lever 3 to move downward.
The movement of 0 is restricted, and it does not rotate clockwise from the position shown in FIG. Therefore, the lift-up lever 10
Is not locked by the pickup lock lever 30 in the lowered position, and the pickup roller shaft 6 is not fixed in the lowered position.

That is, the pickup roller 3 abuts on the uppermost surface of the sheet for a time determined by the shape and angular velocity of the pickup cam 12, and then rises apart from the sheet. During this period, the feed roller 1, the retard roller 2, and the pickup roller 3 are driven by a stepping motor (not shown) to separate and feed the sheets S from the sheet cassette 4.

When the height of the paper surface is lowered in response to the feeding of the sheet, one end of the lifter trigger lever 24 is pushed down by the pickup roller shaft 6, and the rotation restricting member of the lift-up cam 18 is disengaged to form a fan shape for one latch. The ratchet gear 22 rotates to lift the sheet S by the lift portion 23a of the lift-up member 23. By repeating this operation, the paper surface height is maintained substantially constant.

By the series of operations described above, the pickup roller 3 contacts the sheet S only when the sheet S is fed from the cassette 4, and is separated upward from the sheet S otherwise, so that the feed roller 1 and the retard roller 3 are separated. 2 can maximize the effect of preventing double feeding of sheets S,
Double feeding can be reliably prevented.

The setting of the height of the uppermost sheet in the standby state, that is, at the time of feeding the first first sheet after the sheet cassette 4 is attached to the apparatus main body will be described.

When the sheet cassette 4 is mounted, the lifter mechanism first raises the sheet, the pickup lock lever 30 releases the lift-up lever 10, and the lift-up lever 10 causes the pickup roller 3 to be flipped up via the shaft 6. In this flip-up process, the lifter trigger lever 24 moves to the rotation restricting position of the lift-up cam 18 to stop the lifting operation of the sheet S by the lifter mechanism. That is, the uppermost position of the seat is determined by the timing at which the pickup lock lever 30 releases the lift-up lever 10, and the release timing can be appropriately set depending on the shape of the pickup lock lever 30, as shown in FIG. . It is assumed that the height P ₁ is the highest height of the seat in this standby state.

Next, as described above, when the amount of the sheet S decreases and the height of the uppermost sheet reaches P ₂ at the uppermost sheet position during continuous sheet feeding, the lifter trigger lever 24 moves the lift-up cam. It moves from the rotation restriction position of 18 and cancels the restriction. As a result, the lift-up cam 18 rotates to swing the lift arm pawl 19, the fan-shaped ratchet gear 22 rotates counterclockwise by one ratchet tooth, and the lift-up member 23 lifts the sheet S. The movement amount ΔP of the sheet S by one ratchet tooth is defined as
The height of the seat top level after moving to P ₃ (Fig. 16
reference).

Here, it is most ideal that the setting of the uppermost sheet should satisfy the following equation.

P ₂ <P ₁ <P ₃ (= P ₂ + ΔP) In practice, if P ₁ and P ₂ are substantially the same, it will function sufficiently, and experimentally satisfy the following equation. I have confirmed that it is good.

P ₂ −5 mm <P ₁ <P ₃ +5 mm (= P ₂ + ΔP + 5 mm) As described above, the height P of the uppermost sheet in the standby state is set.
Optimal paper feeding can be performed by setting ₁ .

Here, a case where such a setting is not performed will be described. For example, in the case of P ₂ -5 mm> P ₁ , as shown in FIG.
The uppermost sheet becomes too low when the sheet is mounted and enters the standby state, and the sheet sent out by the pickup roller 3 collides with the retard roller 2 which is a separating means, and a feeding failure such as a jam occurs. There is a risk.

When P ₁ > P ₃ +5 mm,
As shown in b of FIG. 17, the uppermost sheet in the standby state becomes too high, and the sheet sent out by the pickup roller 3 collides with the feed roller 1 which is a separating means, so that a feeding failure such as a jam occurs. It may occur. Therefore, in order to prevent such a problem, it is necessary to optimally set the height of the seat top.

Next, withdrawal of the sheet cassette 4 from the apparatus main body when replenishing the sheet S will be described. When pulling out the sheet cassette 4 from the main body of the device,
By operating the handle 48 of the sheet cassette 4, the latch claw 41 on the sheet cassette 4 side is lowered, which lowers the connecting lever 32, thereby restricting the rotation of the lift-up cam 18. At the same time, lift arm claw 1
9, both lift lock pawls 21 are fan-shaped ratchet gears 2
The sheet lifted from the sheet cassette 4 is released from 2, and the lift portion integrally formed therewith is lowered so that the sheet cassette 4 can be pulled out from the apparatus main body.

During the sheet feeding operation, for example, when the main motor 15 of the main body of the apparatus is stopped by accidentally turning off the power, the pickup cam 12 may stop in the state of meshing with the drive gear 13. is there. In this case, the lift-up lever 10 may stop at the lowest position depending on the phase of the pickup cam 12, and at this time, the pickup roller 3 is positioned at the lowest position in the sheet cassette 4 and the sheet cassette. 4 is very difficult to pull out.

However, even in this case, as described above, by the action of the lever member 40 that moves the pickup roller 3 up and down in conjunction with the attachment and detachment of the sheet cassette 4, the sheet cassette 4 is pulled out a little and the pickup roller is pulled out. The sheet cassette 4 can be easily pulled out by raising the height of the sheet cassette 3.

In the above embodiment, the mounting of the sheet cassette 4 is detected by the photo sensor 31 and the solenoid is operated based on the detection to set the standby state. However, the standby state is set by the configuration shown in FIG. You may do it.

As shown in FIG. 18B, when the latch claw 41 of the sheet cassette 4 engages with the frame 7, the latch claw 41 rotates and pushes the connecting lever 32 downward in the figure. At this time, the engaging portion 32 of the connecting lever 32
The lift-up lever 10 is fixed by the pickup lock lever 30 by pulling the lift-up lever 10 downward in FIG. In this fixed state, the lift arm claw 19 swings, the fan-shaped ratchet gear 22 rotates counterclockwise, and the sheet in the sheet cassette 4 is lifted by the lift-up member 23. The subsequent operation is the same as in the above embodiment. In addition, after the latch claw 41 is fitted to the connecting lever 32, the connecting lever 32 is
Is raised, the engaging portion 32b does not hinder the vertical movement of the lift-up lever 10 (state shown in c of FIG. 18).

As shown in FIG. 18, the lift-up lever 10 is fixed by the lift-up lock lever 30 in synchronism with the mounting operation of the sheet cassette 4 without operating the solenoid 14. ,
It is possible to set the sheet cassette 4 in the standby state without using the photo sensor 31 for detecting the mounting of the sheet cassette 4.

Next, an image forming apparatus equipped with the above-described sheet feeding device will be described with reference to FIG. In this embodiment, an image forming apparatus using a laser beam printer will be described.

The sheet cassette 4 is a front loading type which is mounted from the front of the printer 100, and the sheets stacked in the sheet cassette 4 are sent out in the direction orthogonal to the mounting direction of the sheet cassette 4.

The sheet sent out from the sheet cassette 4 is discharged through the image forming section 101 and a fixing section 109 described later. The image forming unit 101 includes a printer 100.
The process cartridge 102 is detachable from the process cartridge 102. The process cartridge 102 includes the electrophotographic photosensitive drum 103, which is an image carrier, and the photosensitive drum 103.
Means 104 for charging the surface of the photosensitive drum, the photosensitive drum 103
Developing means 105 for forming a toner image on the photosensitive drum 10
A cleaning unit 106 and the like for removing the toner remaining on the surface of No. 3 are provided. Photosensitive drum 103
Is exposed by the image light emitted from the scanner unit 107 according to the image signal.

Further, the image forming section 101 is provided with a transfer roller 108 for transferring the toner image formed on the surface of the photosensitive drum 103 to a sheet. The transfer roller 108 presses the sheet sent from the sheet cassette 4 onto the photosensitive drum 103. By applying a voltage having a polarity opposite to that of the toner image to the transfer roller 108, the toner image on the photosensitive drum 103 is transferred onto the sheet. Transfer to.

The sheet on which the toner image is transferred by the transfer roller 108 is sent to the fixing unit 109. This fixing unit 1
A fixing roller 110 is arranged at 09, and heat and pressure are applied by the fixing roller 110 to fix the toner image on the sheet.

As described above, the toner image on the sheet sent from the sheet cassette 4 is transferred by the process cartridge 102 and the transfer roller 108, and the transferred toner image is fixed and discharged by the fixing unit 109.

[0075]

As described in detail above, the present invention is
By controlling the rotation of the toothless gear clutch that performs one rotation control, it is possible to control the lifting operation of the feeding means and the control operation of the uppermost seat of the lifter mechanism.
Electric components such as an electromagnetic clutch, a solenoid, a motor, and a photo sensor, which have been conventionally used, are not required, and the cost can be reduced, and the malfunction can be prevented.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of a sheet feeding device equipped with a drive transmission device of the present invention.

FIG. 2 is a perspective view showing an example of an integrated lift-up member provided in the device shown in FIG.

FIG. 3 is an operation diagram of a mechanism, which is provided in the apparatus shown in FIG. 1, that moves a pickup roller up and down in synchronization with mounting of a sheet cassette.

FIG. 4 is a perspective view of the mechanism shown in FIG.

5 is a longitudinal sectional view showing a mounting operation of the sheet cassette in the apparatus shown in FIG.

FIG. 6 is a diagram showing an example of a conventional toothless gear.

FIG. 7 is a diagram showing an example of a toothless gear of the present invention.

8 is a perspective view showing a state in which the sheet cassette is mounted in the apparatus shown in FIG.

9 is a perspective view showing a start state for bringing the apparatus shown in FIG. 1 into a standby state.

10 is an enlarged view of an essential part showing an operation from a mounted state of the sheet cassette in the apparatus shown in FIG. 1 to a start state for changing to a standby state.

FIG. 11 is a perspective view showing a state in the middle of making the apparatus shown in FIG. 1 into a standby state.

FIG. 12 is a perspective view showing a standby state in the apparatus shown in FIG.

FIG. 13 is an enlarged view of a main part showing an operation from a halfway state to a standby state in the apparatus shown in FIG.

14 is an enlarged view of an essential part showing a state at the time of sheet feeding in the apparatus shown in FIG.

FIG. 15 is an enlarged view of a main part of the apparatus shown in FIG. 1 in a standby state.

16 is a diagram showing a moving range of a seat uppermost position by a lifter mechanism in the apparatus shown in FIG.

FIG. 17 is a diagram showing a state of a sheet feeding failure due to a height position failure of the uppermost sheet in the standby state in the apparatus shown in FIG.

FIG. 18 is a vertical sectional view showing a mounted state of a sheet cassette according to another embodiment.

FIG. 19 is a vertical sectional view showing an example of a printer equipped with a sheet feeding device using the present invention.

[Explanation of symbols]

 3 Pickup Roller (Feeding Means) 4 Sheet Cassette 4b Middle Plate (Sheet Placement Means) 10 Lift Arm Lever (Coupling Means) 12 Pickup Cam 12a Cam Part (Cam) 12b Missing Teeth (Gear Clutch) 13 Drive Gear (Gear clutch with missing teeth) 17 Gear (Gear clutch with missing teeth) 19 Lift arm claw 22 Fan-shaped ratchet gear (ratchet gear) 23a Lift part 24 Lifter trigger lever (regulating means) 30 Pickup lock lever (locking means) 40 Lever member (separation) Means) 45 spring (separating means)

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication H04N 1/00 108 C (72) Inventor Tomoyuki Araki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Takahiro Kurita 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Teruo Komatsu 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. Within

Claims (8)

[Claims] 1. A sheet placing means for placing a sheet, and a top and bottom swingable support for contacting and separating the uppermost sheet placed on the sheet placing means, and the uppermost sheet. A sheet feeding means for feeding the sheet when the sheet comes into contact with the sheet, and a swinging means for swinging the sheet feeding means so as to bring the sheet into contact with and separate from the uppermost sheet. A tooth-missing gear clutch for controlling rotation in which drive transmission is stopped when a tooth-missing tooth portion of the tooth-missing gear faces the drive gear; and a cam that interlocks with rotation transmission by the tooth-missing gear clutch, A sheet feeding device, comprising: a coupling unit that engages with the cam and the feeding unit and swings the feeding unit by the operation of the cam. 2. The sheet placing means has a lifter mechanism for raising and lowering a sheet placing plate on which a sheet is placed to keep the uppermost height of the placed sheet substantially constant. The lifter mechanism includes a rotation control means for controlling the transmission of the rotation drive, an operating member for swinging the lift arm pawl by the transmission of the rotation drive by the rotation control means, and a meshing member provided on the lift arm pawl. And a lift portion for rotating the ratchet gear to rotate the ratchet gear, and a lift portion for raising the sheet placing means by the rotation of the ratchet gear, the rotation control according to the position of the feeding means. The sheet feeding apparatus according to claim 1, wherein the lift is operated by appropriately transmitting rotation by means. 3. A missing tooth gear clutch for controlling rotation in which transmission of rotational drive is stopped when a missing tooth portion of a missing tooth gear faces a drive gear, and the missing tooth gear clutch. The toothed gear clutch is provided so that the position can be regulated with the drive gear and the missing tooth portion facing each other, and the position regulation is released when the feeding means becomes lower than a predetermined first position, A drive gear and a toothless gear that are engaged with each other to transmit rotational drive, and when the feeding means reaches a predetermined second position, position control is performed to block rotational drive. The sheet feeding device according to claim 2. 4. The sheet feeding apparatus according to claim 3, wherein the sheet placing means is an intermediate plate provided in a sheet cassette that is detachably attached to the apparatus body. 5. A separation means for separating the feeding means from a sheet stored in the sheet cassette, and the separation means cancels the separation operation in response to mounting of the sheet cassette. The sheet feeding device described in. 6. A lock means for locking the connecting means by releasing the engagement of the connecting means with the feeding means when the sheet cassette is mounted on the main body of the apparatus. 5. The lock of the connecting means is released in association with the raising of the feeding means to a predetermined third position.
The sheet feeding device described in. 7. The uppermost height of the seat when the locking means is unlocked is substantially the same as the uppermost height of the seat that abuts when the feeding means is in the second position. The sheet feeding device according to claim 6, wherein the third position is set. 8. A sheet placing means for placing a sheet, and an uppermost sheet supported on the uppermost sheet placed on the sheet placing means so as to come into contact with and separate from the uppermost sheet so as to be vertically swingable. Sheet feeding means for feeding the sheet when the sheet comes into contact with the sheet, swinging means for swinging the sheet feeding means so as to bring the sheet into contact with and separate from the uppermost sheet, and the sheet feeding means. An image forming unit for forming an image on a sheet, wherein the swinging unit is provided with a chipping portion for controlling rotation so that drive transmission is stopped when a chipped tooth portion of the chipped tooth gear faces a drive gear. A tooth gear clutch, a cam that interlocks with rotation transmission by the toothless gear clutch, and a coupling means that engages with the cam and the feeding means and swings the feeding means by the operation of the cam. Image forming apparatus characterized by having .