JP3368229B2 - Sheet stacking apparatus and image forming apparatus having the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a laser beam printer or an electrophotographic copying machine, and more particularly to a sheet stacking apparatus for smoothly feeding sheets and an image forming apparatus including the same. It is about.

[0002]

2. Description of the Related Art A sheet stacking apparatus in a conventional image forming apparatus has a sheet feeding cassette body 1 as shown in FIG.
A middle plate 50 that is rotatably supported in the paper feed cassette body 1 about a rotation support shaft 50a; and the middle plate 50 is a sheet insertion port of an image forming apparatus body (not shown). A spring 55 urged toward a sheet feeding roller 3 as a feeding unit provided in the vicinity, a rear end regulating member 53 for aligning the rear ends of the sheets stacked on the intermediate plate 50, and an intermediate plate 50 on the intermediate plate 50. And a width regulating member 60 for regulating the widthwise position of the sheets stacked on the intermediate plate 50, and the middle plate 50 is pivotally supported on the side wall 1a of the sheet feeding cassette body 1 on the trailing end side in the sheet passing direction. It is rotatably provided by.

In the sheet stacking apparatus described above, the rotational moment that rotates the tip of the intermediate plate 50 downward due to the weight of the stacked sheets and the urging force of the spring 55 pushes the tip of the intermediate plate 50 upward. The contact pressure between the sheet feed roller 3 and the sheet (sheet feed pressure) is kept substantially constant by setting the spring constant so that the difference from the rotating moment is almost constant regardless of the load amount. Is commonly used.

The tip of the intermediate plate 50 has a rotary support shaft 50a.
Draw a locus of an arc centered at. Further, the wall surface of the sheet feeding cassette body 1 on the leading end side in the sheet passing direction is provided with the middle plate 50 so that the positions of the sheets stacked on the middle plate 50 do not vary in the front-rear direction.
The curved surface is formed so as to maintain a predetermined clearance with respect to the locus of the tip of the. Moreover, in order to prevent the curved surface of the wall surface from becoming an undercut shape, the pivot shaft 50a is arranged above the side wall 1a of the sheet feeding cassette main body 1, and the tip of the intermediate plate 50 is moved as the sheet stacking amount decreases. Generally, it is formed in a locus that gradually extends forward in the sheet passing direction.

Further, in the sheet stacking apparatus using the claw separation method or the friction separation method, it is necessary to make the position of the leading edge of the sheet contacting the sheet feeding roller 3 substantially constant regardless of the number of stacked sheets, and 500 sheets are required. In a large-capacity paper feed deck such as stacking, the middle plate 5
0 rear end regulating member 53 for regulating the position of the rear end of the sheet
Is used.

[0006]

However, in the above-described sheet stacking apparatus, in the case of a specific sheet having the same size and density, the contact pressure between the sheet feeding roller 3 and the sheet is almost independent of the stacking amount. Although it becomes constant, when another sheet having a different size or density is stacked, the set spring constant is different from the spring constant of the sheet. Therefore, the moment balance is lost and the feeding roller 3 and the sheet are fed. The paper pressure varies greatly when the paper is fully loaded with a large difference in weight depending on the size and density of the sheets.

In particular, for thick paper which requires a large sheet feeding pressure, the number of sheets is small even if the stacking height is the same, and the sheet gap is small, so that the density of the entire sheet bundle is high and the sheet feeding pressure is low. . On the other hand, in the case of thin paper that needs to maintain a low paper feed pressure to prevent double feeding, the paper feed pressure becomes high on the contrary.

Further, since the trailing edge regulating member 53 is arranged on the intermediate plate 50, the trailing edge regulating member 53 is fitted to a small size sheet (sheet passing direction shown by a chain double-dashed line in FIG. 4A). When the number of stacked sheets decreases, the upper end of the trailing edge regulating member 53 projects upward from the side wall 1a. Therefore, when the paper feed cassette is attached to or detached from the image forming apparatus main body, it is necessary to prevent the upper end of the trailing edge regulating member 53 from contacting the image forming apparatus main body, and therefore it is necessary to secure a space. The device becomes larger.

Further, in order to reduce the above-mentioned variation of the sheet feeding pressure and prevent the upper end of the trailing edge regulating member 53 from projecting from the side wall 1a, the position of the rotary support shaft 50a of the intermediate plate 50 is set as shown in FIG. By moving to the leading end side in the sheet passing direction as shown in (b), it is possible to balance the weight of the sheet before and after the rotation support shaft 50a in the sheet passing direction and reduce the weight that balances with the spring of the sheet. , If configured like this,
The amount of movement of the rear end of the middle plate 50 in the vertical direction increases, and the bottom of the paper feed cassette body 1 needs to be deeper as shown in FIG.

Further, in order to suppress the skew of the sheet and improve the printing accuracy, it is necessary to form the width regulating member 60 to be long in the sheet passing direction.
When the position is moved to the leading end side in the sheet passing direction, the width regulating member 6
The length of 0 in the paper passing direction must be shortened, and the printing accuracy cannot be improved.

Further, when the rotation support shaft 50a is arranged near the upper edge of the side wall 1a, at least the side wall 1a near the rotation support shaft 50a needs to be raised corresponding to the position of the rotation support shaft 50a. There is. Therefore, in order to prevent the sheets from being accommodated in the sheet feeding cassette main body 1 and to support the weight of the intermediate plate 50 and the sheets stacked on the intermediate plate 50 at the lower rigid upper edge of the side wall 1a, the sheet feeding cassette It is necessary to increase the rigidity of the side wall.

The present invention has been made in view of the above points, and its first object is to prevent the contact pressure between the sheet and the feeding means from varying due to the size and density of the sheet, and It is an object of the present invention to provide a sheet stacking device that facilitates loading and unloading of sheets and suppresses skewing of the sheets to improve printing accuracy, and an image forming apparatus including the sheet stacking device.

A second object of the present invention is to provide a sheet stacking apparatus which supports the stacking means at two places of the cassette body having high rigidity to stabilize the behavior of the stacking means, and an image including the sheet stacking apparatus. To provide a forming apparatus.

A third object of the present invention is to make the cassette body small regardless of the size of the sheet,
An object of the present invention is to provide a compact sheet stacking device and an image forming apparatus including the same.

[0015]

In order to achieve the above object, a sheet stacking apparatus according to a first aspect of the present invention is a sheet stacking device which is housed in a cassette body and stacks sheets, and a sheet feeding device. A feeding means for feeding and a biasing means for press-contacting the sheets on the stacking means, wherein the feeding means is rotatably supported by the cassette body and the feeding means via the sheets. The load transmitting member that supports the leading end side of the stacking unit in the sheet passing direction so as to be in pressure contact, and the side that is supported in the cassette main body so as to be vertically movable in parallel and that supports the stacking unit on the load transmitting member. A load receiving member connected on the opposite side and rotatably connected to the trailing end side of the stacking means in the sheet passing direction is provided, and moves in parallel with the action of the rotational moment on the leading end side of the stacking means in the sheet passing direction. By the load receiving member And the action of the torque from the paper feeding direction rear end side of the mounting means, characterized in that it has to be canceled in the load transfer member.

According to the second aspect of the present invention, the load transmission member pivotally supports an intermediate portion on a side wall of the cassette body on the leading end side in the sheet passing direction, and has one end through which the stacking means passes. An arm member that rotatably supports the front end side in the paper direction, and the load receiving member is rotatably supported by the other end of the load transmitting member and the side wall of the cassette body at the rear end side in the paper passing direction. It is erected on and supported movably.

According to the third aspect of the present invention, the trailing edge regulating member that regulates the trailing edge position of the sheets stacked on the stacking unit is arranged on the load receiving member so as to be movable in the sheet passing direction.

An image forming apparatus according to a fourth aspect of the present invention is a sheet stacking apparatus according to any one of the first to third aspects, and sheets fed from the sheet stacking apparatus by the sheet feeding means. And an image forming unit for forming an image.

[Operation] Based on the above configuration, when a downward rotation moment acts on the leading end side of the stacking means in the sheet passing direction by the sheet placed on the stacking means, the load receiving member is used to receive the load. A force acts to translate the member upward. At the same time, a downward rotation moment is applied to the trailing end side of the stacking means in the sheet passing direction by the sheets placed on the stacking means, and both rotation moments of the stacking means tip end side in the sheet passing direction. And the rotational moment acting on the rear end side in the sheet passing direction is canceled out. As a result, the urging force of the urging unit that presses the stacking unit against the sheet feeding unit is not affected by the weight of the sheet.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

<First Embodiment> FIG. 1 is a sectional view showing a first embodiment of a sheet stacking apparatus according to the present invention.
FIG. 3 is a plan view showing the above sheet stacking device, and FIG. 3 is an overall configuration diagram showing an image forming apparatus equipped with the above sheet stacking device.

First, an image forming apparatus equipped with the sheet stacking apparatus of this embodiment will be described with reference to FIG. In the present embodiment, a laser beam printer will be described as an example of the image forming apparatus.

In FIG. 3, reference numeral 20 denotes a laser beam printer 20 as an image forming apparatus. The laser beam printer 20 is provided with a paper feed cassette 30 as a cassette body on which a plurality of sheets S are stacked. The laser beam printer 20 is provided with a paper feed roller 3 that rotates only when a sheet is fed at the paper feed port, and when the paper feed roller 3 rotates in the direction of arrow R3 (counterclockwise direction), the paper feed cassette 30 The sheet S is fed from. The sheets S fed by the sheet feeding roller 3 are separated one by one by the separating unit 2, and are conveyed by the conveying roller pair 4 and the registration roller pair 5 toward the image forming unit.

The laser beam printer 20 has a pair of conveying rollers 4 for conveying the sheet S, a pair of registration rollers 5, and a toner image transfer as an image forming portion for transferring the toner image onto the sheet S guided by the pair of registration rollers 5. The unit 8, the developing device 10 that visualizes the electrostatic latent image on the photosensitive drum 7 that constitutes the toner image transfer unit 8, and the toner image visualized on the photosensitive drum 7 is transferred to the sheet S. The transfer roller 6 and the fixing device 15 that fixes the toner image on the sheet S are provided.

Then, the sheet S is fed from the paper feed cassette 30 by the paper feed roller 3 and is separated by the separating means 2 into one.
The sheets are separated one by one, and are guided to the toner image transfer portion 8 by the conveying roller pair 4 and the registration roller pair 5.

Further, the photosensitive drum 7 is uniformly charged by the charger 9 by rotating in the direction of arrow R7 (clockwise direction). After that, the photosensitive drum 7 is exposed by the selective laser light based on the image signal emitted from the laser scanner 22, and an electrostatic latent image is formed. The electrostatic latent image on the photosensitive drum 7 is visualized (toner image) by the developing device 10.

Next, the toner image formed on the photosensitive drum 7 is electrically attracted by the transfer roller 6, and the sheet S passing through the toner image transfer portion 8 is then drawn.
Are sequentially transferred to the print surface (the upper surface in FIG. 3) of, and a toner image is formed on the sheet S.

Thereafter, the sheet S is guided to the nip between the heating means 13 of the fixing device 15 and the pressure roller 14 which is in pressure contact with the heating means 13, and the toner image transferred onto the sheet surface in the process of the sheet S passing through the nip. Is heated and pressed to be fixed on the sheet surface.

The sheet S that has passed through the fixing device 15 is discharged onto the discharge tray 21 through the discharge path 16 by the discharge rollers 18 and 19.

Next, the sheet stacking apparatus according to this embodiment will be described with reference to FIGS. 1 and 2.

In FIG. 1, the paper feed cassette 30 is provided with a load transmission member 32 and an arm member 33 on both left and right sides with an intermediate plate 31 serving as a loading means interposed therebetween. Of the load transmission member 32, an intermediate portion 32a thereof is rotatably supported by a side wall 30a on the front end side of the main body of the paper feed cassette 30 by a shaft 34a, and an arm member 33 has a front end portion 33a in the paper feeding direction on the side wall. A shaft 34b is rotatably supported by a shaft 30a.

Reference numeral 35 denotes a load receiving member disposed in the paper feeding cassette 30, and the load receiving member 35 is the paper feeding cassette 3.
The standing portions 35a arranged along the left and right side walls of 0 are continuously formed by the flat portion 35b so as to be integrally formed. Further, the front end of the load receiving member 35 and the rear end of the load transmitting member 32 are rotatably supported by the connecting shaft 36a, and the rear end of the load receiving member 35 and the rear end of the arm member 33 are separated from each other. It is rotatably supported by the connecting shaft 36b. Further, a rear end side support portion 31a of the middle plate 31 is rotatably supported by an intermediate portion of the load receiving member 35 by a connecting shaft 36c.

The intermediate plate 31 has a sheet stacking surface having a length in the sheet passing direction close to a standard sheet size such as A4 size or letter size, and has a front end side supporting portion 31b at the leading end in the sheet passing direction. An elongated hole 31c is formed in the tip end side support portion 31b, and the load transmitting member 3 is formed in the elongated hole 31c.
A shaft 36d provided at the tip of 2 is slidably inserted. Further, springs 37, 37 are provided on the front end side of the main body of the paper feed cassette 30 as a biasing means for pushing the middle plate 31 upward. And the middle plate 3
When a standard-size sheet S is stacked on the sheet 1, the weight of the sheet S is substantially evenly distributed to the front end side support portion 31b and the rear end side support portion 31a.

Reference numeral 38 denotes a rear end regulating member provided on the flat surface portion 35b so as to be movable along the sheet passing direction. The rear end regulating member 38 is movable in the sheet passing direction according to the sheet size. . 39 is a sheet S stacked on the intermediate plate 31
The width regulating member 39 regulates the position in the width direction of the sheet feeding device. The width regulating member 39 is movably supported in the width direction of the main body of the sheet feeding cassette 30.

In the present embodiment, the distance L ₁ from the shaft 34a to the shaft 34b is determined by the connecting shaft 36a to the connecting shaft 36b.
And the distance L ₃ from the shaft 34a to the connecting shaft 36a is equal to the distance L ₂ from the shaft 34b to the connecting shaft 36b.
₄ is formed to have the same length as ₄ , and the connecting shaft 36a has a shaft 34a.
The connecting shaft 36b is located rearward of the paper feed direction and rotates in the lower range, and the connecting shaft 36b is located rearward of the shaft 34b in the paper feed direction and rotates in the lower range to form a parallel link mechanism. As a result, the load receiving member 35 moves in parallel while maintaining the horizontal state. Further, the shaft 36d moves in a range closer to the leading end side in the sheet passing direction than the shaft 34a.

That is, the connecting shaft 36a and the shaft 36d are provided at a predetermined distance from the shaft 34a, and the connecting shaft 36a
And a line connecting the shaft 34a and the shaft 34a and the shaft 36d.
The angle θ formed by the line connecting the
Within the range of 0 °), the tip end side of the intermediate plate 31 can be vertically rotated about the connecting shaft 36c as the load receiving member 35 constituting the link mechanism is moved in parallel. Therefore, as the number of stacked sheets S decreases, the intermediate plate 31 is rotated by the springs 37, 37 to the two-dot chain line state shown in FIG. .

The above-mentioned distances L ₁ , L ₂ , L ₃ , L ₄
By subtly changing the relationship between the values of
5 movements can be adjusted. That is, for example, L
By setting ₁ <L ₂ or L ₃ <L ₄ , the vertical movement amount of the rear end portion of the load receiving member 35 is larger than the vertical movement amount of the front end portion. Therefore, the trajectory of the load receiving member 35 can be set according to individual design conditions such as space restrictions.

Next, the operation of the intermediate plate in the situation where sheets of various sizes are stacked will be described.

When a standard size sheet S is fully loaded on the intermediate plate 31, the weight of the sheet S is substantially evenly distributed on the front end side support portion 31b and the rear end side support portion 31a of the intermediate plate 31. In other words, the load applied to the rear end side support portion 31 a of the middle plate 31 is the load bearing member 35 and the connecting shaft 36 of the middle plate 31.
The load receiving member 35 tries to move downward in parallel by acting on c. As a result, a moment for rotating the load transmission member 32 in the counterclockwise direction is generated. This moment gives a force in the direction of pushing up the tip of the intermediate plate 31.

On the other hand, the weight of the sheet S hanging on the leading end side support portion 31b of the middle plate 31 acts as a moment for rotating the leading end of the middle plate 31 in the direction of pushing it down. These two moments act in the directions of canceling each other, and the difference in the force for the sheet bundle to push down the leading end of the intermediate plate 31 due to the difference in the density of the sheets S becomes small, and the sheets S stacked on the intermediate plate 31 are reduced. It is possible to suppress variations in the sheet feeding pressure based on the weight of the sheet.

Further, when a small size sheet S is fully loaded, the weight of the sheet S is reduced, so that the force by which the sheet S pushes down the leading end side supporting portion 31b is reduced, but at the same time, the center of gravity of the sheet bundle is the leading end side in the sheet passing direction. To move to the tip side support part 3
A large amount of load is distributed to the front end side support portion 31b and the load distributed to the rear end side support portion 31a. For this reason, since the force for rotating the leading end side support portion 31b of the intermediate plate 31 in the direction of pushing it up becomes small, the variation in the sheet feeding pressure is reduced.
In this case, the front end side support portion 31b and the rear end side support portion 31
The ratio of the load applied to a is inversely proportional to the distance from the position of the center of gravity of the sheet bundle to the shaft 36d that passes through the leading end side support portion 31b and the distance to the connecting shaft 36c that rotatably supports the rear end side support portion 31a. Therefore, the optimum positions of the front end side support portion 31b and the rear end side support portion 31a may be set according to the sheet size that ensures the passage of the paper by moving the rear end regulation member 38.

On the contrary, since a long sheet S of, for example, a legal size is longer than the length of the sheet stacking surface of the intermediate plate 31, its rear end is stacked on the flat surface portion 35b of the load receiving member 35. There is. With this configuration,
The weight of the portion of the long sheet S protruding from the sheet stacking surface works in the direction of pushing up the front end side support portion 31b, and the feeding pressure is higher than that of the standard size sheet S.
Since a thin sheet is generally not used for the long sheet S, there is no fear of double feeding, which is not a big problem.

By configuring the load transmitting member 32, the load receiving member 35, the arm member 33 and the intermediate plate 31 as described above, the weight of the sheet S is adjusted to the tip side support portion 3 of the intermediate plate 31.
By offsetting each other by the 1b and the rear end side support portion 31a, it is possible to suppress variations in the sheet feeding pressure due to the size and density of the sheet S.

Further, by providing the shaft 34a of the load transmitting member 32 and the shaft 34b of the arm member 33 on the relatively high rigidity portion of the side wall 30a, the weight of the intermediate plate 31 and the sheet bundle is increased at two high rigidity positions. I will support it Middle plate 3
The behavior of 1 can be stabilized.

Moreover, since the shafts 34a and 34b can be arranged downward, the side wall 30a of the paper feeding cassette 30 is provided.
The height of the sheet S can be reduced, and a large amount of sheets S can be easily taken in and out.

Further, since the intermediate plate 31 is not directly supported by the main body of the sheet feeding cassette 30, it is possible to dispose the width regulating member 39 having a sufficient length in the sheet passing direction, so that the skew of the sheet S can be prevented. It is possible to suppress and improve the printing accuracy.

Further, the length of the intermediate plate 31 is set to a length in the sheet passing direction which is close to the standard sheet size, and the long sheet rear end is loaded on the load receiving member 35. Therefore, it is not necessary to deepen the bottom of the main body of the sheet feeding cassette 30, and the rear end regulating member 38 is disposed on the load receiving member 35, so that the rear end regulating member 38 can be adjusted to the sheet S of any size. However, the vertical movement range does not change, and there is no need to make a space for preventing the upper end of the trailing edge regulating member 38 from contacting the laser beam printer.
Space can be used effectively.

[0048]

As is apparent from the above description, when a downward rotation moment is applied to the leading end side of the stacking means in the sheet passing direction by a sheet placed on the stacking means, the load is transmitted via the load transmitting member. A force that translates the receiving member upward is applied, and at the same time, a downward rotation moment acts on the trailing end side of the stacking unit in the sheet passing direction by the sheets mounted on the stacking unit. Since both rotation moments cancel out the rotation moments acting on the support portions on the front end side and the rear end side of the stacking unit in the sheet passing direction, the sheet feeding pressure between the sheet feeding unit and the sheet depending on the size and density of the sheet. It is possible to suppress the unevenness of the sheet, and to prevent the conveyance failure due to the thick paper and the double feeding due to the thin paper.

Further, since the load receiving member that moves in parallel is rotated by the load transmitting member that rotates in response to the parallel movement of the subordinate receiving member, the stacking means pressed by the biasing means is rotated. The height of the side wall of the main body can be kept low, so that the sheets can be easily taken in and out.

Further, since the load transmitting member and the arm member are rotatably supported by the highly rigid side wall portions of the cassette body, the behavior of the loading means can be stabilized and the loading means can be communicated. Since the rear end side in the paper direction does not pivot significantly in the vertical direction, the cassette body can be made small and compact regardless of the size of the sheet.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of a sheet stacking device according to the present invention.

FIG. 2 is a plan view showing the sheet stacking apparatus of the above.

FIG. 3 is an overall configuration diagram showing an image forming apparatus equipped with the above-described sheet stacking apparatus.

FIG. 4A is a sectional view showing an example of a conventional sheet stacking apparatus, and FIG. 4B is a sectional view showing another example of a conventional sheet stacking apparatus.

[Explanation of symbols]

3 Feeding means (paper feed roller) 8 Image forming section (toner image transfer section) 30 cassettes (paper feed cassettes) 30a side wall 31 Loading means (middle plate) 32 Load transmission member 33 Arm member 35 Load receiving member 37 Biasing means (spring) 38 Rear end regulating member S sheet

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-8-91591 (JP, A) JP-A-59-182132 (JP, A) JP-A-55-151440 (JP, A) JP-A-3- 56326 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) B65H 1/12 310

Claims (4)

(57) [Claims] 1. A sheet stacking apparatus which is housed in a cassette main body and has stacking means for stacking sheets, and biasing means for pressing the sheets on the stacking means to a feeding means for feeding the sheets. A load transmission member that is rotatably supported by the cassette body and that supports the leading end side of the stacking means in the sheet passing direction so as to be pressed against the feeding means via the sheet; A load receiver that is supported so as to be movable in parallel in the vertical direction, is connected to the load transmission member on the side opposite to the side that supports the stacking means, and is rotatably connected to the rear end side of the stacking means in the sheet passing direction. The load transfer means includes the action of a rotational moment on the leading end side of the stacking means in the sheet passing direction and the action of a rotating moment on the trailing end side of the stacking means by the load receiving member that moves in parallel. Member smell The sheet stacking device is characterized in that they are offset by each other. 2. The load transmission member rotatably supports an intermediate portion on a side wall of the cassette main body in a sheet passing direction tip side, and has one end rotatably a sheet passing direction tip side of the stacking means. The load receiving member is movably mounted on the other end of the load transmitting member and an arm member rotatably supported on a side wall of the cassette body on the rear end side in the sheet feeding direction. The sheet stacking apparatus according to claim 1, wherein the sheet stacking apparatus is supported. 3. A rear end regulating member that regulates a rear end position of a sheet stacked on the stacking unit is disposed on the load receiving member so as to be movable in a sheet passing direction. Alternatively, the sheet stacking device according to claim 2. 4. The sheet stacking device according to claim 1, and an image forming unit that forms an image on a sheet fed by the feeding unit from the sheet stacking device. An image forming apparatus characterized in that