Patent Grant
11084676
This application is based on and claims the benefit of Japanese Patent Application No. 2018-185378 filed on Sep. 28, 2018, the contents of which are hereby incorporated by reference.
The present disclosure relates to image forming apparatuses. More particularly, the present disclosure relates to an image forming apparatus provided with a sheet storage cassette including a sheet stacking plate of which an upstream-side part in the sheet feeding direction is swingably supported.
Sheet feeding cassettes (sheet storage cassettes) are used in image forming apparatuses as exemplified by copiers and printers, for the purpose of feeding cut paper sheets and the like. In a sheet feeding cassette, a large number of unprinted sheets are stocked previously, and from the topmost layer of the sheets stacked in it, one sheet after another is fed out separately by a pickup roller, a sheet feeding roller, and the like provided near the sheet feeding cassette.
The sheet feeding cassette includes a sheet stacking plate on the top face of which sheets are stacked. The upstream end of the sheet stacking plate in the sheet feeding direction is supported inside the sheet feeding cassette, and about the point of support as a pivot, the sheet stacking plate is swingable, with a downstream-side end part of it in the sheet feeding direction as a swing end (free end). The sheet feeding cassette also includes a lift mechanism that permits the swing end of the sheet stacking plate to ascend and descend.
In this sheet feeding cassette, as the number of sheets in it decreases, the swing angle of the sheet stacking plate (its inclination angle relative to the horizontal plane) increases. Consequently, the head end position of the topmost sheet when the remaining quantity of sheets is small falls upstream, in the sheet feeding direction, of the head end position of the topmost sheet when the remaining quantity of sheets is large. This results in an increased sheet-to-sheet distance (distance from the tail end of a foregoing sheet to the head end of the following sheet) during continuous sheet feeding.
One solution to the problem is a known sheet feeding cassette in which a tail end cursor for aligning the tail ends of stacked sheets is provided with a pressing member that presses the sheets downstream in the sheet feeding direction and a biasing member that biases the pressing member downstream in the sheet feeding direction. In this sheet feeding cassette, as the remaining quantity of sheets decreases, the pressing member protrudes from the tail end cursor and moves the sheets downstream in the sheet feeding direction. This helps reduce, to a certain degree, the increases in the sheet-to-sheet distance during continuous sheet feeding.
A sheet feeding cassette in which a tail end cursor is provided with a pressing member that presses sheets downstream in the sheet feeding direction and a biasing member that biases the pressing member downstream in the sheet feeding direction is disclosed, for example, in Patent Document 1.
Inconveniently, the above-mentioned conventional sheet feeding cassette with a tail end cursor provided with a pressing member and a biasing member requires a complicated structure in the tail end cursor. Moreover, when and how much the pressing member protrudes from the tail end cursor to move sheets are affected by the stiffness of sheets and the like, and turn out to be unstable.
According to one aspect of what is disclosed herein, an image forming apparatus includes a sheet storing cassette, a lift mechanism, a sheet feeding portion, a remaining quantity sensing portion, and a control portion. A sheet storing cassette includes a sheet storing portion and a sheet stacking plate. The sheet storing portion stores sheets. The sheet stacking plate, on which the sheets are placed, is supported in the sheet storing portion so as to be ascendable and descendable about a swing pivot on the upstream side in the sheet feeding direction. The lift mechanism makes the sheet stacking plate ascend and descend. The sheet feeding portion feeds the sheets to a sheet conveying passage. The remaining quantity sensing portion senses the remaining quantity of sheets in the sheet feeding cassette. The control portion controls the sheet feeding portion. During continuous feeding of the sheets by the sheet feeding portion, the control portion controls the lift mechanism to make the sheet stacking plate ascend to a lifted position where the sheets make contact with the sheet feeding portion and feeds a foregoing sheet and then, at a sheet feeding timing a predetermined time thereafter, starts feeding the following sheet. The control portion makes the sheet feeding timing earlier as the remaining quantity of the sheets sensed by the remaining quantity sensing portion decreases.
This and other objects of the present disclosure, and the specific benefits obtained according to the present disclosure, will become apparent from the description of embodiments which follows.
An embodiment of the present disclosure will be described below with reference to the accompanying drawings.
In
A manual feed tray 102 is provided outside an upper part of the right side face of the image forming apparatus 100. The manual feed tray 102 is for placement of sheets of a different size or thickness from the sheets in the sheet feeding cassettes 1a and 1b, or sheets that are fed in one at a time, such as OHP sheets, envelopes, postcards, and invoices.
Inside the image forming apparatus 100, a sheet conveying portion 103 is arranged. The sheet conveying portion 103 is located to the right, that is, on the downstream side in the sheet feeding direction, of the cassette mount portion 101, and is located to the left, that is, on the downstream side in the sheet feeding direction, of the manual feed tray 102. Sheets P fed out of the sheet feeding cassettes 1a and 1b are conveyed vertically upward along a side face of the main body of the image forming apparatus 100 by the sheet conveying portion 103, and sheets P fed out of the manual feed tray 102 are conveyed horizontally.
On the top face of the image forming apparatus 100, a document conveying device 104 is arranged, and under it, an image reading portion 105 is arranged. When copying a document, a user places the document, comprising a plurality of sheets, on the document conveying device 104. The document conveying device 104 feeds out one sheet after another separately from the document, and the image reading portion 105 reads its image data.
On the downstream side of the sheet conveying portion 103 in the sheet conveying direction under the image reading portion 105, an image forming portion 106 and a transfer portion 107 are arranged. At the image forming portion 106, based on the image data read by the image reading portion 105, an electrostatic latent image of the document image is formed. This electrostatic latent image is developed to form a toner image. On the other hand, in synchronism with the timing of the toner image formation at the image forming portion 106, a sheet P is conveyed from the sheet feeding cassettes 1a and 1b to the transfer portion 107 via a registration roller pair 119 of the sheet conveying portion 103. The toner image formed at the image forming portion 106 is transferred to the sheet P at the transfer portion 107.
On the downstream side of the transfer portion 107, a fixing portion 108 is arranged. The sheet P to which the toner image has been transferred at the transfer portion 107 is conveyed to the fixing portion 108, and as the sheet P passes through a nip portion in a fixing roller pair comprising a heating roller and a pressure roller, the unfixed toner image is fixed to the sheet P to become a permanent image.
On the downstream side of the fixing portion 108, near the left side face of the image forming apparatus 100, a discharge/branch portion 109 is arranged. The sheet P discharged from the fixing portion 108 is, when no double-sided printing is performed, discharged from the discharge/branch portion 109 onto a sheet discharge tray 111 provided outside the left side face of the image forming apparatus 100.
Over the cassette mount portion 101, a two-side printing unit 110 is arranged. When two-side printing is performed, sheets P discharged from the fixing portion 108 are fed to the display printing unit 110 via the discharge/branch portion 109. The sheets P fed to the display printing unit 110, with its obverse and reverse sides reversed by switch-back, passes through the sheet conveying portion 103 again to be conveyed to the transfer portion 107 with the unprinted side up.
The image forming apparatus 100 is provided also with a control portion 120 which controls driving of different portions constituting the image forming apparatus 100 such as the cassette mount portion 101, the sheet conveying portion 103, the image reading portion 105, the image forming portion 106, the transfer portion 107, and the fixing portion 108.
Next, the structure of the sheet feeding cassette 1a removably mounted in the image forming apparatus 100 will be described in detail with reference to
The sheet feeding cassette 1a is mounted in the cassette mount portion 101 in the image forming apparatus 100. A cassette base (sheet storing portion) 10 that constitutes the main body portion of the sheet feeding cassette 1a is composed of a flat box open at its top face, and a bundle of sheets P is stored in it from above. In the cassette mount portion 101 inside the image forming apparatus 100, above the sheet feeding cassette 1a, a sheet feeding unit 117a (see
The sheet feeding cassette 1a is inserted in the cassette mount portion 101 by being horizontally slid in the arrow A direction shown in
A sheet stacking plate 20 on which sheets P are stacked is a plate-like member and is provided such that the downstream end in the sheet feeding direction (arrow B direction) is ascendable/descendable with respect to the cassette base 10 with stacking plate supporting portions 20a on both sides in the sheet width direction (arrow AA′ direction) acting as pivots. The stacking plate supporting portions 20a are provided at an end part on the upstream side of the sheet stacking plate 20 in the sheet feeding direction and are fixed to the cassette base 10.
On both sides of the sheet stacking plate 20 in its width direction, there is provided a pair of width regulation cursors 7a and 7b for positioning, in the width direction, the sheets P stacked on the sheet stacking plate 20 so as to be reciprocatable in the sheet width direction (arrow AA′ direction) along a width regulation cursor guide groove formed in the cassette base 10. Due to an unillustrated coordination mechanism provided under the pair of width regulation cursors 7a and 7b, when one of the pair is moved, also the other is moved in coordination. Here, the pair of width regulation cursors 7a and 7b moves symmetrically with each other about the middle line of sheets P in the width direction.
The sheet feeding cassette 1a includes a tail end cursor 9 which, by being arranged at a position corresponding to the size of sheets P, makes contact with and aligns the tail end of the sheets P stacked on the sheet stacking plate 20. Sheets P are conveyed in arrow B direction toward the sheet conveying portion 103 (see
By moving the width regulation cursors 7a and 7b and the tail end cursor 9 according to the size of sheets P stacked on the sheet stacking plate 20, the sheets P are stored in a predetermined position inside the sheet feeding cassette 1a. The sheet stacking plate 20 has notches formed along the moving ranges of the width regulation cursors 7a and 7b and the tail end cursor 9.
As shown in
The other end of the swing shaft 21 (an end part in arrow A direction in
As shown in
In the mount portion 41, a lock portion 41a is formed which has a locking groove in which the engagement pin 23 is fitted. This permits the actuator 40 to rotate together with the engagement pin 23 and the swing shaft 21.
In the fan portion 42, a reinforcing rib 42a and an arc rib 42b, which is a light shielding portion, are formed. The arc rib 42b is provided on a circumferential portion at a tip end of the fan portion 42 and projects in the axial direction of the swing shaft 21 (insertion direction of the sheet feeding cassette 1a (arrow A direction)). The cassette mount portion 101 is, as shown in
The three remaining quantity sensors 140 (140a to 140c) are arranged along the track of the arc rib 42b. When the remaining quantity of sheets on the sheet stacking plate 20 changes and the swing shaft 21 and the actuator 40 rotate, the optical path between the light emitting portion and the light receiving portion is switched between an open state and a shielded state. Thus, when three remaining quantity sensors 140a to 140c are used, the remaining quantity of sheets P on the sheet stacking plate 20 can be sensed in four steps (OFF/OFF/OFF, ON/OFF/OFF, ON/ON/OFF, ON/ON/ON).
Specifically, the sheet feeding cassette 1a can accommodate sheets P up to about 500 sheets. When the sheet feeding cassette 1a is stacked with about 500 sheets P, the sheet feeding cassette 1a is in the state shown in
When, from the state shown in
When, from the state shown in
When, from the state shown in
When, from the state shown in
Hereinafter, the state where the optical paths of the remaining quantity sensors 140a to 140c are open (OFF/OFF/OFF, with the remaining quantity of sheets about 500 to about 376) is referred to as a first state, the state where only the optical path of the remaining quantity sensor 140a is shielded from light (ON/OFF/OFF, with the remaining quantity of sheets about 375 to about 251) is referred to as a second state, the state in which only the optical path of the remaining quantity sensor 140c is open (ON/ON/OFF, with the remaining quantity of sheets about 250 to about 126) is referred to as a third state, and the state in which the optical paths of the remaining quantity sensors 140a to 140c are shield from light (ON/ON/ON, with the remaining quantity of sheets about 125 to about 1) is referred to as a fourth state. In this way, using the three remaining quantity sensors 140a to 140c, the remaining quantity of sheets P on the sheet stacking plate 20 can be sensed in four steps (the first, second, third, and fourth states).
Here, as shown in
The control portion 120, during continuous sheet feeding, makes the sheet feeding units 117a and 117b start to feed out sheets P at a sheet feeding timing a predetermined time after the detection of the foregoing sheet P by the sheet detection sensors 118a and 118b.
Although the following description deals with a case where sheets P in the sheet feeding cassette 1a are fed out, it applies also in a case where sheets P in the sheet feeding cassette 1b are fed out, and thus no overlapping description will be repeated.
The control portion 120, during continuous sheet feeding, makes the sheet feeding timing of the sheet feeding unit 117a starting sheet feeding earlier as the remaining quantity of sheets in the sheet feeding cassette 1a decreases. Here, the control portion 120, during continuous sheet feeding, makes the sheet feeding timing earlier stepwise as the remaining quantity of sheets in the sheet feeding cassette 1a decreases (as the remaining quantity sensors 140a to 140c shift from the first state to the second state, to the third state, and then to the fourth state).
Specifically, the control portion 120, in the first state (with the remaining quantity of sheets about 500 to about 376), makes the pickup roller 129a start sheet feeding at a timing a predetermined reference time after the detection of a sheet P by the sheet detection sensor 118a.
The control portion 120, in the second state (with the remaining quantity of sheets about 375 to about 251), makes the pickup roller 129a start sheet feeding before the above-mentioned reference time passes after the detection of a sheet P by the sheet detection sensor 118a. Here, the line speed of the sheet feeding unit 117a is 250 mm/sec, and thus the feeding by the pickup roller 129a starts 8 msec earlier. Thus, sheets P are displaced 2 mm (that is, 250 mm/sec×8 msec) downstream in the sheet feeding direction.
The control portion 120, in the third state (with the remaining quantity of sheets about 250 to about 126), makes the pickup roller 129a start sheet feeding at a timing earlier than in the second state. Here, the feeding by the pickup roller 129a starts 16 msec earlier. Thus, sheets P are displaced 4 mm (that is, 250 mm/sec×16 msec) downstream in the sheet feeding direction.
The control portion 120, in the fourth state (with the remaining quantity of sheets: about 125 to about 1), makes the pickup roller 129a start sheet feeding at a timing earlier than in the third state. Here, the feeding by the pickup roller 129a starts 24 msec earlier. Thus, sheets P are displaced 6 mm (that is, 250 mm/sec×24 msec) downstream in the sheet feeding direction.
Through correction of the sheet feeding timing as described above, even when the remaining quantity of sheets on the sheet stacking plate 20 has decreased until the head end position of the topmost sheet P is located on the upstream side of the head end reference position P1 in the sheet feeding direction, the increase in the sheet-to-sheet distance is suppressed to be about zero to about two millimeters.
In this embodiment, as described above, the control portion 120, during continuous sheet feeding, makes the sheet feeding timing of the sheet feeding units 117a and 117b starting sheet feeding earlier as the remaining quantity of sheets in the sheet feeding cassettes 1a and 1b decreases. This helps suppress the increase in the sheet-to-sheet distance (the distance from the tail end of a foregoing sheet P to the head end of the following sheet) during continuous sheet feeding. It is also possible, unlike with conventional sheet feeding cassettes, to adjust the sheet feeding timing without being affected by the stiffness of sheets P.
There is no need to provide the tail end cursor 9 with a pressing member for pressing sheets P downstream in the sheet feeding direction or a biasing member for biasing the pressing member downstream in the sheet feeding direction, and this helps suppress complicating the structure of the tail end cursor 9.
Owing to the features described above, with the image forming apparatus 100 according to the embodiment, it is possible, with a simple structure, to accurately suppress an increase in the sheet-to-sheet distance during continuous sheet feeding.
Moreover, as described above, the control portion 120 makes the sheet feeding timing earlier stepwise each time the remaining quantity of sheets P in the sheet feeding cassettes 1a and 1b decreases by a predetermined number of sheets (here, about 125 sheets). This allows easy adjustment of the sheet feeding timing in accordance with the remaining quantity of sheets in the sheet feeding cassettes 1a and 1b.
Moreover, as described above, the remaining quantity sensing portion 150 includes an actuator 40 that moves in coordination with the ascent and descent of the sheet stacking plate 20 and remaining quantity sensors 140 that sense the remaining quantity of sheets in the sheet feeding cassettes 1a and 1b as a result of optical paths being opened and shielded by the actuator 40. It is thus possible to easily sense the remaining quantity of sheets in the sheet feeding cassettes 1a and 1b.
Moreover, as described above, the sheet detection sensors 118a and 118b are arranged close to downstream-side parts, in the sheet conveying direction, of the sheet feeding roller pair 130a and 130b respectively, and sense the tail ends of sheets P. This makes it possible to sense sheets P at a position closer to the sheet feeding units 117a and 117b, and thus to suppress more accurately an increase in the sheet-to-sheet distance during continuous sheet feeding.
It should be understood that the embodiments disclosed herein are in every aspect illustrative and not restrictive. The scope of the present disclosure is not limited by the description of the embodiments given above but by the appended claims, and encompasses any modifications made within a sense and scope equivalent to those of the claims.
For example, although the above description deals with an example where the present disclosure is applied to a monochrome multifunction peripheral as shown in
Although the above embodiment deals with an example where a remaining quantity sensing portion 150 including remaining quantity sensors 140 and an actuator 40 is used, this is not meant to limit the present disclosure; instead, any of various types of remaining quantity sensing portion may be used. For example, it is possible to use a remaining quantity sensing portion including an optical sensor or the like that senses the height position of an upstream-side end part of the top face of the sheets P in the sheet feeding cassettes 1a and 1b or the height position of a downstream-side end part of the bottom face of the sheet stacking plate 20.
Although the above embodiment deals with an example where the sheet feeding cassettes 1a and 1b are provided with sheet detection sensors 118a and 118b respectively, this is not meant to limit the present disclosure. Instead, for example, for the sheet feeding cassettes 1a and 1b, a single sheet detection sensor 118a may be provided to be shared between them. With this configuration, it is possible to suppress an increase in the number of components. In that case, the sheet detection sensor 118a can be arranged between the sheet feeding roller pair 130a and the registration roller pair 119.
Although the above embodiment deals with an example where the sheet detection sensor 118a senses the tail end of a sheet P, it may instead sense the head end of a sheet P.
Although the above embodiment deals with an example where the remaining quantity of sheets on the sheet stacking plate 20 is sensed in four steps, this is not meant to limit the present disclosure; instead, the remaining quantity of sheets on the sheet stacking plate 20 may be sensed in two, three, or five or more steps.
| Number | Date | Country | Kind |
|---|---|---|---|
| JP2018-185378 | Sep 2018 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 20050236760 | Kang | Oct 2005 | A1 |
| 20130026699 | Maruta et al. | Jan 2013 | A1 |
| 20160355361 | Arai | Dec 2016 | A1 |
| 20190256308 | Yamashita | Aug 2019 | A1 |
| Number | Date | Country |
|---|---|---|
| 1690873 | Nov 2005 | CN |
| 102902177 | Jan 2013 | CN |
| 8-324804 | Dec 1996 | JP |
| Entry |
|---|
| Chinese Office Action dated Nov. 18, 2020, issued to corresponding Chinese Application No. 201910912712.3. |
| Number | Date | Country | |
|---|---|---|---|
| 20200102167 A1 | Apr 2020 | US |
