JPH08113375A - Drive transmission device, sheet feeding device, and image forming apparatus - Google Patents

Abstract

(57) [Summary] [Purpose] To reduce the collision noise, which is annoying when a missing gear starts meshing with a mating gear. [Structure] Several teeth 200 of the missing tooth gears 12b and 17 on the side where they start to mesh with a mating gear (drive gear) 13 are made softer than other teeth 201. As the material of the tooth 200 portion, for example, various kinds of elastic, rubber, nylon, etc. are used. Further, the tooth 200 portion is formed by the gears 12b, 17
It is integrated by two-color molding.

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 or the like for feeding a sheet such as a document or a recording sheet to an image forming apparatus such as a facsimile, a copying machine or a printer.

[0002]

2. Description of the Related Art In a sheet feeding apparatus provided in an image forming apparatus such as a facsimile machine, a copying machine, a printer or the like, in order to keep the height of the uppermost sheet stacked on a sheet stacking means substantially constant. There is also a lifter device for feeding a sheet from a certain height by a feeding roller or the like.

In this type of lifter device, control for keeping the height of the uppermost sheet constant is performed by bringing a lever or the like into contact with the uppermost sheet surface, and the displacement of the lever or the like is detected by an electric sensor such as a photosensor. The sheet stacking means, which stacks the sheets, is moved up and down based on the detection.

The raising / lowering operation of the sheet stacking means is carried out by appropriately driving an electric actuator such as a dedicated motor, electromagnetic clutch, or solenoid.

In the drive transmission device of such a lifter device, for example, in order to control rotation such as one-rotation control, a toothless gear in which some teeth on the circumference are cut off as shown in FIG. There is one using 117. This is to cut off the drive transmission when the missing tooth portion 117a corresponds to the mating gear. In general, the toothless gear 117 and the mating gear that meshes with the toothless gear 117 are formed entirely of metal.

[0006]

However, the drive transmission device of the above-mentioned conventional lifter device using the metal tooth-chipped gear 117 has the following problems.

That is, when the chipped tooth gear 117 starts to mesh with the mating gear, the tooth surfaces collide with each other, and a collision noise is generated. In particular, when the driven side driven and controlled by the toothless gear clutch is required to continuously rotate at a relatively high speed, this collision sound becomes very annoying. This is because the peripheral speed of the gear on the driving side and the peripheral speed of the tooth-missing gear on the driven side are different, so that the tooth surfaces collide violently at the moment when they mesh.

Therefore, the present invention has been made in view of the above-mentioned circumstances, and a collision noise which causes an offensive effect by absorbing the impact force between the tooth flanks when the toothless gear starts to mesh with the gear on the other side is generated. An object of the present invention is to provide a drive transmission device that does not occur.

[0009]

DISCLOSURE OF THE INVENTION The present invention relates to a drive transmission device in which one of the drive transmission elements is a toothless gear (17) in which some teeth on the circumference are cut off.

In order to achieve the above object, the present invention provides, among the plurality of teeth of the toothless gear (17),
It is characterized in that some of the teeth (200) on the starting end side, which start meshing with the mating gear (13), are made softer than the other teeth (201).

[0011]

According to the present invention having the above-mentioned structure, the missing tooth gear (17) is provided with the gear (1) on the opposite side of the soft tooth (200).
3) It will start to mesh with the teeth. Therefore, the impact force generated when the tooth surfaces collide with each other is absorbed by the mating gear (13).

As a result, the collision noise generated when the tooth surfaces collide with each other is almost eliminated, and the ears are not disturbed. It is also possible to prevent damage to the teeth of both gears (13, 17).

The reference numerals in parentheses refer to the drawings and do not limit the structure of the present invention.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. <Embodiment 1> FIG. 1 shows the configuration of a sheet feeding device provided with a drive transmission device of the present invention. Note that FIG. 1 shows a state in which the sheet cassette 4 is about to be attached to the main body of the image forming apparatus 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 the sheets S stacked and stored in the sheet cassette 4 one by one. To send.

A stepping motor (not shown) is provided on the frame 7, and the driving force from the stepping motor is transmitted to the shaft 1a of the feed roller 1 and the shaft 2a of the retard roller 2. 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 shaft of the pickup roller 3 (hereinafter referred to as a pickup roller shaft), which extends rightward in FIG. 1 through an arcuate hole 8 formed in the frame 7.

Inside the 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,
The sheet cassette 4 and the push-up portion 40a, which is swingably supported by the bearing portion 7a formed integrally with the frame 7 and pushes up the pickup roller shaft 6 inserted into the hole 8, are provided in the main body of the image forming apparatus. It is composed of an abutting portion 40b which is pressed when mounted 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 the 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 contacted, 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 image forming 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 by the frame 7, and the gear 17 is provided with a lift-up cam 18 coaxially therewith. This gear 17 corresponds to the drive gear 13
It is a toothless gear that is provided so that it can mesh with 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 and is provided so that a pawl portion 19a (see FIG. 10) is engaged by a spring 19b with a tooth surface of a fan-shaped ratchet gear 22. It is energized. Then, the lift arm pawl 19 is rotated by the lift-up cam 18 to rotate the shaft 20.
, And the fan-shaped ratchet gear 22 is rotated counterclockwise in FIG. 1 one tooth at a time.

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

With this structure, the lift arm pawls 19 rotate the fan-shaped ratchet gears 22 while the lift-lock pawls 21 prevent the fan-shaped ratchet gears 22 from rotating in the reverse direction, and are integrally formed with the fan-shaped ratchet gears 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 is provided with 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 move the seat S. Can be lifted.

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 them 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.

In FIG. 2B, a resin such as polyacetal having a slidability necessary for the fan-shaped ratchet gear 22 is used, and a highly rigid resin such as glass is used for the lift portion 23a and the connecting shaft portion 23b. It is the lift-up member 23 having a two-body structure used. 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 construction or the two-piece construction as described above can withstand a large weight, it becomes possible to sufficiently cope with, for example, a large-sized sheet or a sheet cassette capable of stacking a large number of sheets. There is. Further, 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 about 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 which is integral 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 missing tooth gear 17 is regulated 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 tooth-chipped gear 17 and the drive gear 13 mesh with each other, the lift-up cam 18 rotates, the lift arm pawl 19 swings, and the fan-shaped ratchet gear 22 rotates to 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 pawl portion 30a and an eaves portion 30b which is shaped to protrude above the pickup roller shaft 6. The claw portion 30a is
When the lift-up lever 10 is moved to the lowest position, the tip of the lift-up lever 10 is hooked or re-locked.
When the pickup roller shaft 6 moves upward, the pickup lock lever 30 is rotated counterclockwise in FIG. 1 against the biasing force of the spring 25 to release the tip of the lift-up lever 10 from the claw portion 30a. It has a function of raising the lift-up lever 10.

Reference numeral 31 is a photo sensor 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 and a handle 48 provided on the front side of the image forming apparatus via a rod 47. It is connected. The latch pawl 41 is normally biased counterclockwise by a spring 46,
By pulling the handle 48, it rotates clockwise.

The connecting lever 32 swings when the latch claw 41 provided on the sheet cassette 4 is fitted thereto. As shown in FIG. 5A, when the sheet cassette 4 is not attached, the connecting lever 3
2 is lowered, and when the sheet cassette 4 is installed,
As shown in FIG. 5B, the latch claw 41 is connected to the connecting lever 3.
2 is fitted 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 4la 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.

FIG. 6 shows the structure of the tooth-missing gears 12b and 17 which the pickup cam 12 and the lift-up cam 18 have.

The tooth-missing gears 12b and 17 are made of metal (steel, for example), but the several tooth portions 2 on the starting end side that start to mesh with the drive gear 13 which is the counterpart gear.
00 is made of a softer material than the other tooth portions 201. The material forming the tooth portion 200 is, for example, various elastomers, rubber, nylon, or the like.

Here, as shown in FIG. 7, the tooth portion 200 formed separately is coupled to the toothless gears 12b and 17 (the sagittal protrusion 200a is press-fitted into the groove 200b and is bonded with an adhesive). However, the missing tooth gears 12b and 1
The tooth portion 200 may be integrated with the tooth portion 7 by two-color molding.

As described above, by making the several teeth on the side where the meshing starts from the soft material, the mating drive gear 13 surely meshes while absorbing the impact of the teeth of the soft material, and the peripheral speeds of the mutual gears. Since the teeth of the hard material for transmitting the original torque are meshed with each other after the torques become equal to each other, the impact noise caused by the difference in the peripheral speed of the teeth hardly occurs.

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

First, before the sheet cassette 4 accommodating the sheets S is mounted, the sheet cassette 4 shown in FIG. 1, FIG. 8 and FIG.
As shown in FIG.
Although the drive gear 13 is continuously rotated by the drive force of, the missing tooth portion of both the pickup cam 12 and the lift-up cam 18 faces the drive gear 13.
The rotation transmission is restricted and the operation is stopped.

At this time, the integrally formed lift-up member 23 is in the lowest position, and the pickup roller 3
Is held by the pickup roller shaft 6 being pushed up by the lift-up lever 10 in the most raised state. Note that, 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 32 is
Since a does not shield the photo sensor 31 from light, attachment 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 attached to the main body of the image forming apparatus, as shown in FIG. 5 (b), the latch claw 41 of the sheet cassette 4 causes the connecting lever 32 to rotate and be lifted, and the flag 32a causes the photo. The sensor 31 is shielded from light to detect the attachment 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 urging means (not shown) so that the gear portion 12b of the pickup cam 12 and the drive gear 13 are engaged with each other, the drive is transmitted, and the pickup cam 12 makes one rotation in the arrow direction. At the time of meshing the gears, as described above, the several tooth portions 20 on the side where the meshing of the gear portion 12b, which is the missing tooth gear, starts.
Since 0 is softer than the teeth of the drive gear 13, the meshing is smoothly performed, and the collision noise due to the peripheral speed difference is hardly generated.

When the pickup cam 12 makes one rotation, the lift-up lever 10 is lowered, and one end thereof is caught by the claw portion 30a of the pickup lock lever 30, and the lift-up lever 10 is locked. At this time, the pickup roller 3 is urged by its own weight or an urging means such as a spring (not shown) to descend. This lowering lowers the pickup roller shaft 6 to rotate the lifter trigger lever 24, whereby the other end of the lifter trigger lever 24 is released from the rotation restricting position of the lift-up cam 18. As shown in FIG. 3B, since the lever member 40 is moved to a position lower than the lifted position of the pickup roller shaft 6 by mounting the sheet cassette 4, the lever member 40 restricts the lowering of the pickup roller shaft 6. There is no such thing.

In the lift-up cam 18 whose regulation has been released, the tooth-missing gear 17 formed in the main body meshes with the drive gear 13 to rotate, thereby swinging 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 S in the sheet cassette 4 is lifted (FIG. 1).
And the state shown in FIG. Even when the gears are engaged, as described above, since the several tooth portions 200 of the missing tooth gear 17 on the side where the engagement is started are softer than the drive gear 13, the tooth surface caused by the peripheral speed difference at the engagement is formed. Almost no collision sound is generated between them.

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 30b of the pickup lock lever 30 is lifted and the pickup lock lever 30 rotates counterclockwise. Then, the lock of the lift-up lever 10 is released. At the moment when this is released, the lift-up lever 10 lifts the pickup roller 3 to the most raised state by the urging action of the spring 11, and puts the image forming apparatus in the standby state in which the sheet can be fed (see FIGS. 12 and 12). 13 (b)).

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 re-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 S for a time determined by the shape of the pickup cam 12 and the angular velocity, and then rises apart from the sheet S. 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 one by one.

When the height of the sheet surface is lowered in response to the feeding of the sheet S, 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 and only one latch is left. The fan-shaped ratchet gear 22 rotates and the lift portion 23a of the lift-up member 23 lifts the seat S. 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.

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

When the sheet cassette 4 is mounted, the lifter mechanism first raises the sheet S, 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. . The height of the top of the seat in this standby state is P ₁ .

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. Let ΔP be the amount of movement of the sheet S by one ratchet tooth,
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 tens ΔP) Practically, if P ₁ and P ₂ are substantially the same, it works sufficiently. We have confirmed that we are satisfied.

P ₂ -5 mm <P ₁ <P ₃ +5 mm (= P
₂ + ΔP + 5 mm) Thus, the height P of the seat top in the standby state
Optimal paper feeding can be performed by setting ₁ .

Here, a case where such a setting is not performed will be described. For example, when P ₂ −5 mm> P ₁ , as shown in FIG. 17A, the topmost sheet becomes too low when the sheet cassette 4 is mounted and the standby state is set, and the pickup The sheet S sent out by the roller 3 may collide with the retard roller 2 which is a separating means, and a feeding failure such as a jam may occur.

Further, when P ₁ > P ₃ +5 mm, as shown in FIG. 17B, the uppermost sheet in the standby state becomes too high, and the sheet S fed by the pickup roller 3 becomes too high. There is a risk of colliding with the feed roller 1 as the separating means and causing a feeding failure such as a jam. Therefore, in order to prevent such a problem, it is necessary to optimally set the height of the seat top.

Next, the pulling-out of the sheet cassette 4 from the main body of the image forming apparatus when replenishing the sheet S will be described.

When pulling out the sheet cassette 4 from the main body of the image forming apparatus, by operating the handle 48 of the sheet cassette 4, the latch claw 41 on the sheet cassette 4 side is lowered, whereby the connecting lever 32 is lowered and lifted. The rotation of the up cam 18 is restricted. At the same time, both the lift arm pawl 19 and the lift lock pawl 21 are released from the fan-shaped ratchet gear 22, and the lifter portion integrally formed with the fan-shaped ratchet gear 22 is lowered to lower the surface of the sheet cassette 4
Can be extracted from the main body of the image forming apparatus.

During the sheet feeding operation, for example, when the power is accidentally turned off and the main motor 15 of the main body of the image forming apparatus is stopped, the pickup cam 12 is stopped in the state of meshing with the drive gear 13. There are cases. 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 configuration shown in FIG. 18 sets the standby state. 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 3 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 the figure by 2b. In this fixed state, the lift arm pawl 19 swings, the fan-shaped ratchet gear 22 rotates counterclockwise, and the lift-up member 23 lifts the sheet S in the re-sheet cassette 4.
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 3
Since 2 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 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. <Embodiment 2> FIG. 19 shows another structural example of the tooth-missing gears 12b and 17.

Here, several tooth portions 202 on the starting end side which start to mesh with the driving gear 13 on the other side are replaced with other tooth portions 2.
The tooth portion 202 is made of a softer material than
So that it can be bent in the radial direction of the gear.
04 is provided.

Therefore, in the tooth-missing gears 12b and 17 having this structure, the impact force at the time of starting meshing with the mating gear 13 is further absorbed, and the collision noise is significantly reduced.

FIG. 20 shows an example of the overall construction of a laser beam printer as an image forming apparatus equipped with the sheet feeding device.

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

The sheet S delivered from the sheet cassette 4 passes through the image forming section 101 and the fixing section 109 and is ejected to the outside of the machine. The image forming unit 101 includes a printer body 1
00 is provided with a detachable process cartridge 102. The process cartridge 102 includes an electrophotographic photosensitive drum 103, which is an image carrier, a charging unit 104 for charging the surface of the photosensitive drum 103, and a photosensitive drum 103. A developing unit 105 for forming a toner image, a cleaning unit 106 for removing toner remaining on the surface of the photosensitive drum 103, and the like are provided. The 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 the sheet S. The transfer roller 108 presses the sheet S 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 S.

The sheet S onto which the toner image has been transferred by the transfer roller 108 is sent to the fixing section 109. A fixing roller 110 is arranged in the fixing unit 109, and heat and pressure are applied by the fixing roller 110 to fix the toner image on the sheet S.

As described above, the toner image is transferred to the sheet S sent from the sheet cassette 4 by the process cartridge 102 and the transfer roller 108, and the fixing unit 109 is used.
The toner image transferred by is fixed and discharged to the outside of the apparatus.

[0078]

As described above, in the drive transmission device of the present invention, since the several teeth on the starting end side of the tooth-missing gear are soft teeth, when the tooth-missing gear meshes with the mating gear, The impact force will be absorbed by the gear on the other side. Therefore, the collision noise generated when the tooth surfaces collide with each other is almost eliminated, and there is no annoyance to the ears. Further, it is possible to prevent damage to the teeth due to impact.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration of a sheet feeding device including a drive transmission device of the present invention.

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

FIG. 3 is an operation diagram of a mechanism for vertically moving a pickup roller, which is provided in the device shown in FIG.

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

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

FIG. 6 is a perspective view showing the configuration of a toothless gear that constitutes the drive transmission device of the present invention.

FIG. 7 is a perspective view for explaining a method of incorporating soft teeth into the same missing tooth gear.

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 starting 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 the mounted state of the sheet cassette in the apparatus shown in FIG. 1 to a start state for changing to a standby state.

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

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

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

FIG. 14 is an enlarged view of an essential part showing a state during 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 the lifter mechanism in the apparatus shown in FIG.

17 is a diagram showing a state of 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 by another method.

FIG. 19 is a perspective view showing the structure of a missing tooth gear according to another embodiment.

FIG. 20 is a vertical cross-sectional side view showing the configuration of a printer (image forming apparatus) including a sheet feeding device to which the present invention is applied.

FIG. 21 is a perspective view showing a configuration of a tooth-missing gear included in a lifter device of a conventional sheet feeding device.

[Explanation of symbols]

12b Pickup cam gear portion (chipped gear) 13 Drive gear (counter gear) 17 Gear (chipped gear) 200,202 Several teeth on start side 201,203 Other teeth

Claims (6)

[Claims] 1. A drive transmission device in which a toothless gear with a part of the teeth on the circumference being cut off is used as one of the drive transmission elements, wherein a mating gear is included in the plurality of teeth of the toothless gear. A drive transmission device characterized in that several teeth on the starting end side that start to mesh with are made softer than the other teeth. 2. The drive transmission device according to claim 1, wherein the soft tooth portion is made of plastic or the like, and is integrated with the chipped gear by two-color molding. 3. A thinning portion is provided on the starting end side of the chipped gear so that the soft tooth portion is bent in the gear radial direction when meshing with the mating gear. Drive transmission device. 4. A locking means for locking the rotation of the missing tooth gear, wherein when the locking means locks the missing tooth gear, the missing tooth gear rotates at a position where the missing tooth portion faces the mating gear. 2. The drive transmission device according to claim 1, wherein when the locking means releases the lock of the toothless gear, the toothless gear meshes with the mating gear from the starting end side. 5. A sheet feeding device having a lifter device for keeping the height of the uppermost sheet stacked on the sheet stacking means substantially constant, in which some teeth on the circumference are cut off. A drive transmission device in which a tooth gear is provided in the drive transmission path, and among the plurality of teeth of the toothless gear, some of the starting end side teeth that start meshing with the other gear are softer than the other teeth. A sheet feeding device comprising the lifter device. 6. An image forming apparatus, comprising: the sheet feeding device according to claim 5; and an image forming unit that forms an image on a sheet fed from the sheet feeding device.