JP3176198B2 - Drive transmission device and sheet feeding device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive transmission device used for a sheet feeding device for feeding a document or recording paper to an image forming apparatus such as a facsimile, a copying machine, a printer and the like.

[0002]

2. Description of the Related Art In a sheet feeding apparatus, a lifter mechanism is provided for keeping the uppermost height of stacked sheets substantially constant, and the sheets are fed from a fixed height by a feeding roller or the like. There is something.

In this type of lifter mechanism, control for keeping the height of the uppermost position of the sheet constant has conventionally been such that a lever or the like is brought into contact with the uppermost surface of the sheet and displacement of the lever is detected by an electric sensor such as a photo sensor. There is a device that detects a target by a target sensor and raises / lowers a mounting table or the like on which a sheet is loaded based on the detection.

The lifting operation is performed by a dedicated motor,
It is performed by appropriately driving an electric actuator such as an electromagnetic clutch and a solenoid.

In such a drive system of the lifter mechanism, for example, to control the rotation such as one rotation control, FIG.
Toothless gear 11 with a part of the teeth cut out as shown in FIG.
7 is used. In this case, when the missing tooth portion corresponds to the gear 118 on the mating side, the transmission of the drive is interrupted.

[0006]

However, the missing tooth gear has the following problems.

[0007] When the parallelism between the shaft of the toothless gear and the shaft of the mating gear slightly deviates, the tooth tips may collide with each other and drive transmission may not be performed smoothly. Therefore, a loss of driving torque, generation of abnormal noise, and the like may occur. In the worst case, the drive system is locked and rotation may not be transmitted at all, or the teeth of the gear may be damaged.

In particular, when the apparatus is used for a long period of time, there is a problem that the parallelism is disturbed due to backlash of each axis, which causes the above-mentioned problem and deteriorates the durability of the apparatus.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to realize smooth engagement between a toothless gear and a mating gear.

[0010]

According to the present invention, there is provided a toothless gear with a part of teeth cut out, and a mating gear engaged with the toothless gear, wherein the toothless part of the toothless gear is formed. In a state in which the transmission of the drive is interrupted in a state of facing the counterpart gear, the drive transmission device that transmits the drive when the missing tooth gear and the counterpart gear mesh with each other, wherein the missing tooth portion is the counterpart gear. When the missing tooth gear rotates from the state facing the gear and starts meshing with the other gear, the meshing of the missing gear with the other gear in the tooth portion meshing with the other gear of the missing tooth gear is performed. The tooth width of the starting portion is smaller than the tooth width of the other portion of the missing tooth gear. Further, the present invention provides a sheet feeding apparatus which includes a lifter mechanism for lifting up a sheet supporting means to lift a sheet stacked on the sheet supporting means, and feeding the sheet lifted by the lifter mechanism by a feeding means. A toothed gear having a partially cut-out tooth and a counterpart gear meshing with the toothless gear, and driven in a state where the toothless portion of the toothless gear faces the counterpart gear. When the missing tooth gear and the mating gear are engaged with each other, there is provided driving force transmitting means for transmitting the driving force of a driving source to the lifter mechanism, and the missing tooth portion is provided with the mating gear. When the missing tooth gear rotates and starts meshing with the counterpart gear from a state in which it faces the counterpart gear, the counterpart gear in the tooth portion of the chipping gear that meshes with the counterpart gear. Characterized by being narrower than the tooth width of the other portions of 該欠 only gear tooth width of the portion begins chewing and.

[0011]

According to the above construction, the tooth width of the toothless portion at the beginning of biting is reduced and the amount of intersection of the tooth tip line at the moment of starting biting is reduced. Collision between the tooth tips can be avoided as much as possible.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a sheet feeding apparatus according to the present invention will be described with reference to FIGS. FIG. 1 shows a state where the sheet cassette 4 is to be mounted on 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 pick-up roller. These three rollers separate and feed the sheets S stacked and stored in the sheet cassette 4 one by one. I do.

The frame 7 is provided with a stepping motor (not shown). The driving force from the stepping motor is applied to the shaft 1 a of the feed roller 1 and the retard roller 2.
To the shaft 2a. The pickup roller 3 rotates by transmitting the driving force of the feed roller 1 via a gear train (not shown).

The retard roller 2 is supported by a swingable support member (not shown), and can be moved toward and away from the feed roller 1. A torque limiter (not shown) is provided on the shaft 2a of the retard roller 2, and the forward and reverse rotation of the retard roller 2 is controlled by the torque limiter.

Reference numeral 5 denotes a roller holder for supporting the feed roller 1 and the pickup roller 3. The roller holder 5 is swingably supported by the shaft 1a of the feed roller 1, whereby the pickup roller 3 is fed. The roller 1 is supported swingably around a shaft 1 a. 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 the frame 7.

A mechanism for moving the pickup roller 3 up and down in conjunction with the mounting of the sheet cassette 4 is provided inside the elongated hole 8 in the frame 7. As shown in FIGS. 3 and 4, the mechanism includes a lever member 40 and a spring 45 for urging the lever member 40 clockwise. The lever member 40 is formed of a metal wire,
A push-up portion 40a which is swingably supported by a bearing portion 7a formed integrally with the frame 7 and pushes up the pickup roller shaft 6 inserted through the elongated hole 8;
An abutting portion 40b which is pressed when the sheet cassette 4 is mounted on the apparatus main body and swings the lever member 40 against the urging force of the spring 45.

In FIG. 1, a lift arm lever 10 is rotatably attached to a shaft 9 integrally formed with the frame 7, and the lift arm lever 10 is rotated by a spring 11 attached to one end. It is biased clockwise in FIG. The pickup roller shaft 6 is in contact with one end of the lift arm lever 10.
Further, the other end of the lift arm lever 10 extends near the pickup cam 12, and swings the lift arm lever 10 by rotating the pickup cam 12. Thereby, the pickup roller 12 is moved up and down via the lift arm lever 10 by rotating the pickup cam 12 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 slides and a gear portion 12b which can mesh with the drive gear 13. The gear portion 12b has no teeth, that is, a so-called missing tooth. It is gear. The pickup cam 12 is urged counterclockwise in FIG. 1 by urging means such as a spring (not shown), and its rotation is regulated by a flapper type solenoid 14 against the urging force of the urging means. I have. 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 employed in this embodiment will be described in detail.

A gear 17 is rotatably supported by the frame 7, and the gear 17 has a lift-up cam 18 on the same axis. The gear 17 is provided with the drive gear 13
This is a missing tooth gear that is provided so as to be able to mesh with the gear and has no teeth. 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) meshes with a tooth surface of the sector ratchet gear 22 by a spring 19b. Has been energized. Then, the lift arm pawl 19 swings around the shaft 20 by the rotation of the lift-up cam 18, and rotates the fan-shaped ratchet gear 22 one tooth at a time in a counterclockwise direction in FIG. 1.

A claw portion 21a (shown in FIG. 13) of a rotatably supported lift lock claw 21 is urged by a spring 21b on the tooth surface of the sector-shaped ratchet gear 22 to rotate the sector-shaped ratchet gear 22 in reverse. 1 (clockwise rotation in FIG. 1).

With this configuration, the lift arm pawl 19 rotates the fan-shaped ratchet gear 22 while the lift lock pawl 21 prevents the reverse rotation of the fan-shaped ratchet gear 22, and is integrally formed with the fan-shaped ratchet gear 22. The lift-up member 23 is raised from the opening 4 a formed in the sheet cassette 4, thereby lifting up the sheet S in the sheet cassette 4. The sheet cassette 4 is provided with a swingable middle plate 4b. The sheets S are stacked on the middle plate 4b, and the sheet is lifted by swinging the lift portion 23a of the lift-up member 23 from below. Can be

Here, the configuration 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 sector-shaped ratchet gear 22, and a connection shaft portion 23b for connecting them are integrally formed. The lift-up member 23 is preferably made of, for example, a resin containing glass and has high rigidity.

FIG. 2B shows a fan-shaped ratchet gear 22.
The lift-up member 23 has a two-body configuration using a resin such as polyacetal having a slidability necessary for the above-mentioned process, and using a resin having a high rigidity, for example, a resin containing glass for the lift portion 23a and the connection shaft portion 23b. 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 integral structure or the two-body structure can withstand a large weight, it can sufficiently cope with, for example, a large-size sheet or a sheet cassette capable of stacking a large number of sheets. ing. In the case of an integral structure, the fan-shaped ratchet gear 22 is used.
No phase shift occurs between the sheet S and the lift portion 23a, and the phase shift can be prevented as much as possible with a two-body structure, so that the height control of the sheet S can be performed with high accuracy.

In FIG. 1, reference numeral 24 denotes a lifter trigger lever. The lifter trigger lever 24 is swingably supported around a shaft 9 integrally formed from the frame 7, and is urged clockwise in FIG. 1 by a spring 25. One end of the lifter trigger lever 24 has a function as a regulating member for regulating the rotation of the missing tooth gear 17 integrated with the lift-up cam 18 described above. 13, the rotation of the toothless gear 17 is restricted. The other end of the lifter trigger lever 24 is positioned so as to come into contact with 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 to release the restriction on the rotation of the lift-up cam 18 at one end thereof.
Is slightly rotated by urging means (not shown). This rotation causes the toothless gear 17 and the drive gear 13 to mesh with each other, causing the lift-up cam 18 to rotate. The lift-arm pawl 19 swings to rotate the sector-shaped ratchet gear 22 to raise the lift-up member 23. Further, 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 denotes a pickup lock lever.
The spring 25 is biased clockwise in FIG. 1 to form a claw portion a and an eave portion b having a shape protruding above the pickup roller shaft 6. The claw portion a has a function of catching and locking the tip when the lift-up lever 10 moves to the lowest position, and the eaves portion b comes into contact when the pickup roller shaft 6 moves up, and the pickup lock lever 30 is moved by the spring 25. 1 to rotate counterclockwise in FIG. 1 so that the tip of the lift-up lever 10 is
And lifts the lift-up lever 10.

Reference numeral 31 denotes a photosensor for detecting the mounting of the sheet cassette 4, and reference numeral 32 denotes a connecting lever. 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. The latch claw 41 is connected to a handle 48 provided on the front side of the apparatus via a rod 47. ing. The latch pawl 41 is normally urged counterclockwise by a spring 46,
To rotate clockwise.

The connection lever 32 is connected to the sheet cassette 4
The latch pawls 41 provided on the main body are pivoted by fitting. As shown in FIG. 5A, when the sheet cassette 4 is not mounted, the connecting lever 32 is lowered. When the sheet cassette 4 is mounted, the latch pawl 41 is connected as shown in FIG. 5B. The connection lever 32 is rotated and raised while being fitted to the lever 32. When the latch pawl 41 and the connection lever 32 are fitted, the sheet cassette 4 is fixed by engaging the pawl portion 41 a of the latch pawl 41 with the engaging portion 7 b formed on the frame 7. The connection lever 32 is integrally formed with a flag 32a for shielding the photo sensor 31 from light.
Detects the mounting of the sheet cassette 4 by shielding the photo sensor 31 from light.

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

Next, the toothless gears 12b and 17 used in the pickup cam 12 and the lift-up cam 18 will be described with reference to FIGS. FIG. 6 shows an example of a conventional missing tooth gear.

In this embodiment, as shown in FIG. 7, the toothless gears 12b and 17 are such that the tooth widths of the parts 12c and 17a which start to mesh with the driving gear 13 which is the mating partner gear are smaller than those of the other parts. The tooth width is formed so that the tooth width gradually narrows as the portions 12c and 17a at which the engagement starts are closer to the end at the side at which the engagement with the mating gear 13 starts.

[0038] In addition, the robbed portions 12d and 17b are formed inside the portions 12c and 17a at which the toothless gears 12b and 17 start to mesh with the drive gear 13, thereby cushioning the impact when the teeth mesh. Can be.

With this structure, as shown in FIG. 7B (a diagram viewed from the radial direction of FIG. 7A), even if the degree of parallelism of the shafts of the gears meshing with each other is slightly out of alignment, the tips of the tooth tips are not aligned. Collision can be avoided as much as possible. Compared This is because, as seen in comparison with the conventional missing tooth gear shown in FIG. 6, cross amount C of the tip line of the moment to start chewing the cross of the prior art C _p (shown in b of FIG. 6) But it can be understood from the fact that it is very small.

[0040]

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

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

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. Note that, as shown in FIG.
Is also maintained at the position where the pickup roller shaft 6 is lifted. At this time, as shown in FIG. 5A, the connection lever 32 is in a lowered state, and the mounting of the sheet cassette 4 is not detected because the flag 32a does not shield the photosensor 31 from light.

Next, a 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.
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 an urging means (not shown), and the gear portion 1 of the pickup cam 12 is rotated.
The drive gear 13 meshes with the drive gear 2a, and the drive is transmitted, so that the pickup cam 12 makes one rotation in the direction of the arrow. As described above, when the gears mesh with each other, the meshing start portion 12c of the gear portion 12b, which is the toothless gear, is set narrower than the drive gear 13, so that the meshing is performed smoothly and abnormal noise such as a collision noise is generated. Never do. After one rotation, the missing tooth portion of the gear portion 12a again faces the drive gear 13 to interrupt the transmission of the drive.

When the pickup cam 12 makes one rotation, the lift-up lever 10 is lowered, and one end thereof is hooked on 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 a biasing means such as a spring (not shown). This lowering causes the pickup roller shaft 6
When the lifter trigger lever 24 is rotated, the other end of the lifter trigger lever 24 is released from the rotation restriction position of the lift-up cam 18. The lever member 40 is, as shown in FIG.
By moving the pickup roller shaft 6 from the raised position to the lowered position, the lowering of the pickup roller shaft 6 is not restricted.

The lift-up cam 18, for which the restriction has been released, rotates as the integrally formed missing tooth gear 17 meshes with the drive gear 13 and swings the lift arm pawl 19.
As a result, the sector-shaped ratchet gear 22 rotates counterclockwise, and the lift portion 23a of the lift-up member 23 rotates to lift the sheet in the sheet cassette 4 (FIG. 11).
And the state shown in FIG. 13A). As described above, the meshing start portion 17a of the toothless gear 17 is also set to be narrower than the drive gear 13 at the time of meshing of the gears, so that meshing is performed smoothly and abnormal noise such as collision noise is generated. Nothing.

When the sheet S is lifted, the pickup roller 3 is raised, and when the pickup roller shaft 6 is raised to a predetermined height, the eaves portion b of the pickup lock lever 30 is lifted and the pickup lock lever 30 is lifted.
Rotates counterclockwise to unlock the lift-up lever 10. At the moment when the lift is released, the lift-up lever 10 raises the pickup roller 3 to the highest state by the action of the spring 11 to bring the apparatus into a standby state in which the sheet can be fed (see FIG. 12 and FIG. 13B). State shown).

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

That is, the pickup roller 3 comes into contact with the uppermost surface of the sheet for a time determined by the shape and the angular velocity of the pickup cam 12, and then rises away from the sheet. During this time, 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 one by one.

When the height of the paper surface is reduced in accordance with the sheet feeding, 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, thereby forming a sector by 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 height is maintained substantially constant.

By a series of these operations, the pick-up roller 3 comes into contact with the sheet S only when the sheet S is fed out of the cassette 4, and at other times, the pickup roller 3 is separated upward from the sheet S, so that the feed roller 1 and the retard roller 2 can maximize the ability to prevent double feed of sheet S,
Double feed can be reliably prevented.

Here, the standby state, that is, the setting of the height of the uppermost sheet at the time of feeding the first sheet after the sheet cassette 4 is mounted on the apparatus main body will be described.

When the sheet cassette 4 is mounted, first, the lifter mechanism raises the sheet, the pickup lock lever 30 releases the lift-up lever 10, and the pickup roller 3 is jumped up via the shaft 6 by the lift-up lever 10. In this flip-up process, the lifting operation of the sheet S by the lifter mechanism is stopped by moving the lifter trigger lever 24 to the rotation restricting position of the lift-up cam 18. 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 this release timing can be set as appropriate according to the shape of the pickup lock lever 30, as shown in FIG. . The height P ₁ the uppermost sheet when this standby state.

Next, as the position of the sheet uppermost in continuous feed is described above, when the amount is reduced the uppermost sheet height of the sheet S is P _2, the lift-up cam lifter trigger lever 24 is Move from the rotation restricting position 18 to release 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, and the sheet S is lifted by the lift-up member 23. The movement amount ΔP of the sheet S by one ratchet 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 uppermost sheet setting satisfies the following equation.

P ₂ <P ₁ <P ₃ (= P ₂ + ΔP) Practically, if P ₁ and P ₂ are substantially the same, they function satisfactorily. It has been 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
Optimal paper feeding can be performed by setting ₁ .

Here, a case where such setting is not performed will be described. For example, if P ₂ −5 mm> P ₁ , as shown in FIG.
When the standby state is set by mounting the sheet, the uppermost sheet of the sheet becomes too low, and the sheet fed by the pickup roller 3 collides with the retard roller 2 serving as the separating means, thereby causing a feeding failure such as a jam. There is a fear.

When P ₁ > P ₃ +5 mm,
As shown in FIG. 17B, the top of the sheet in the standby state becomes too high, and the sheet sent out by the pickup roller 3 collides with the feed roller 1 serving as the separating means, which causes a feeding failure such as a jam. This may occur. Therefore, in order not to cause such a problem, it is necessary to set an optimum height of the uppermost sheet.

Next, withdrawal of the sheet cassette 4 from the apparatus main body when replenishing the sheets S will be described. When pulling out the sheet cassette 4 from the apparatus main body,
By operating the handle 48 of the sheet cassette 4, the latch claw 41 on the sheet cassette 4 side is lowered, whereby the coupling lever 32 is lowered, whereby the rotation of the lift-up cam 18 is restricted. At the same time, lift arm claw 1
9. Both lift lock claws 21 are fan-shaped ratchet gears 2.
2, the lifter part integrally formed with the sheet cassette 2 is lowered to lower the paper surface, and the sheet cassette 4 can be extracted from the apparatus main body.

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

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

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 so.

As shown in FIG. 18B, when the latch pawl 41 of the sheet cassette 4 engages with the frame 7, the latch pawl 41 rotates and pushes the connecting lever 32 downward in the drawing. 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 down the lift-up lever 10 in the downward direction in FIG. In this fixed state, the lift arm pawl 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. After the latch pawl 41 is fitted to the connection lever 32, the connection lever 32
Is raised, the engaging portion 32b does not hinder the vertical movement of the lift-up lever 10 (the state shown in FIG. 18C).

As described above, when the lift-up lever 10 is fixed by the lift-up lock lever 30 in conjunction with the mounting operation of the sheet cassette 4 without operating the solenoid 14, as shown in FIG. ,
The standby state can be set without using the photo sensor 31 for detecting the mounting of the sheet cassette 4.

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

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

The sheet sent from the sheet cassette 4 is discharged through an image forming unit 101 and a fixing unit 109 described later. The image forming unit 101 includes a printer 100
An electrophotographic photosensitive drum 103 serving as an image bearing member is provided with a process cartridge 102 which is detachable from the photosensitive drum 103.
Charging means 104 for charging the surface of the photosensitive drum 103
Developing means 105 for forming a toner image on the photosensitive drum 10
A cleaning means 106 for removing the toner remaining on the surface of No. 3 is provided. Photosensitive drum 103
Is exposed by image light emitted from the scanner unit 107 in accordance with an image signal.

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, and applies a voltage having a polarity opposite to that of the toner image to the transfer roller 108 to transfer the toner image on the photosensitive drum 103 to the sheet. Transfer to

The sheet on which the toner image has been transferred by the transfer roller 108 is sent to the fixing unit 109. This fixing unit 1
A fixing roller 110 is disposed 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 sheet sent from the sheet cassette 4 is transferred with the toner image by the process cartridge 102 and the transfer roller 108, and the transferred toner image is fixed by the fixing unit 109 and is discharged.

[0074]

As described in detail above, the present invention provides
By making the tooth width of the part of the missing tooth gear that starts to mesh with the counterpart gear narrower than the tooth width of the other parts, the amount of intersection of the tooth tip line at the moment of starting to mesh is reduced, and the degree of parallelism of the axes of each gear is reduced. Even if the teeth are out of order, it is possible to avoid collision between the tips as much as possible.

For this reason, the gears are smoothly meshed, and efficient drive transmission is performed. In addition, it is possible to greatly reduce the loss of driving torque, the generation of abnormal noise, and the like. Further, it is possible to reliably prevent the drive system from being locked or the gear tips from being damaged.

[Brief description of the 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 apparatus shown in FIG.

3 is an operation diagram of a mechanism provided in the apparatus shown in FIG. 1 for vertically moving a pickup roller.

FIG. 4 is a perspective view of the mechanism shown in FIG. 3;

FIG. 5 is a longitudinal sectional view showing a mounting operation of a sheet cassette in the apparatus shown in FIG. 1;

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

FIG. 7 is a view showing an example of a toothless gear according to the present invention;

8 is a perspective view showing a state when a sheet cassette is mounted in the apparatus shown in FIG. 1;

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

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

FIG. 11 is a perspective view showing a state in the middle of setting the apparatus shown in FIG. 1 to a standby state;

FIG. 12 is a perspective view showing a standby state in the apparatus shown in FIG. 1;

FIG. 13 is an enlarged view of a main part showing the operation of the apparatus shown in FIG. 1 from the intermediate state to the standby state to the standby state;

FIG. 14 is an enlarged view of a main part showing a state during sheet feeding in the apparatus shown in FIG. 1;

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

FIG. 16 is a view showing a movement range of a topmost sheet by a lifter mechanism in the apparatus shown in FIG. 1;

FIG. 17 is a diagram illustrating a state of a sheet feeding failure due to a position error of a topmost sheet in a standby state in the apparatus illustrated in FIG. 1;

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

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

[Explanation of symbols]

 12b Gear part (missing tooth gear) 12c Biting start part 13 Drive gear (partner gear) 17 Chipping gear 17a Biting start part 17b Meat steal part

Claims (12)

(57) [Claims] 1. A toothless gear having a part of teeth cut out,
When the missing tooth portion of the missing gear is opposed to the other gear, transmission of drive is interrupted, and the missing gear and the other gear are engaged. A drive transmission device that transmits drive when meshed with the gear, when the missing tooth gear rotates from the state where the missing tooth portion faces the opposite gear and starts meshing with the opposite gear. A drive transmission, wherein a tooth width of a portion of the toothless gear that meshes with the counterpart gear is started to be smaller than a tooth width of another part of the toothless gear. apparatus. 2. The tooth width of a portion of the toothless gear that starts meshing with the counterpart gear is gradually reduced as approaching the end of the toothless gear that starts meshing with the counterpart gear. 3. The drive transmission device according to claim 1. 3. The drive transmission device according to claim 1, wherein a carving portion is provided radially inward corresponding to a portion of the toothless gear in which the tooth width is reduced. 4. The drive transmission device according to claim 1, further comprising a lock unit that stops the missing tooth gear at a position where the missing tooth portion faces the counterpart gear. 5. The drive transmission device according to claim 4, wherein said lock means is a solenoid. 6. A sheet feeding apparatus comprising: a lifter mechanism for lifting up a sheet supporting means to lift a sheet stacked on the sheet supporting means; and feeding the sheet lifted by the lifter mechanism by a feeding means. It has a toothless gear with a part of the teeth cut out, and a mating gear that meshes with the toothless gear. When the toothless part of the toothless gear faces the mating gear, the driving gear is driven. In a state in which transmission is interrupted and the missing gear and the mating gear are engaged with each other, a driving force transmitting means for transmitting a driving force of a driving source to the lifter mechanism is provided, and the missing gear portion is provided to the mating gear. When the missing tooth gear rotates from the opposed state and starts meshing with the mating gear, the mating gear in the tooth portion of the missing gear that meshes with the mating gear. A sheet feeding apparatus is characterized in that narrower than the tooth width of the other portions of 該欠 only gear tooth width of the portion begins chewing and. 7. The tooth width of a part of the toothless gear which starts to mesh with the counterpart gear is gradually reduced as the portion approaches the end of the toothless gear that starts to mesh with the counterpart gear. 3. The sheet feeding device according to 1. 8. The sheet feeding device according to claim 6, wherein a carved portion is provided radially inward corresponding to a portion of the toothless gear in which the tooth width is reduced. 9. The sheet feeding device according to claim 6, wherein the lifter mechanism includes a lock unit that stops the missing tooth gear at a position where the missing tooth portion faces the counterpart gear. . 10. The sheet feeding device according to claim 9, wherein said locking means is a solenoid. 11. A lifter mechanism for reducing the number of sheets loaded on the sheet support means in order to keep the uppermost height of the sheets supported by the sheet support means substantially constant. 10. The sheet feeding device according to claim 9, further comprising a release unit configured to release a lock of the lock unit and transmit a driving force to the lifter mechanism in accordance with a higher-order displacement. 12. An image forming apparatus comprising: the sheet feeding device according to claim 6; and an image forming unit that forms an image on a sheet fed from the sheet feeding device. Characteristic image forming apparatus.