Information
-
Patent Grant
-
6183151
-
Patent Number
6,183,151
-
Date Filed
Wednesday, June 30, 199925 years ago
-
Date Issued
Tuesday, February 6, 200123 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Hilten; John S.
- Nguyen; Anthony H.
Agents
- Fitzpatrick, Cella, Harper & Scinto
-
CPC
-
US Classifications
Field of Search
US
- 400 582
- 400 578
- 400 624
- 400 596
- 400 605
-
International Classifications
-
Abstract
The present invention provides sheet feeding apparatus comprises a sheet stacking means, a sheet feeding rotary member, conveying means, leading edge detecting means, driving means, and control means, and the control means controls a conveying amount of the sheet by the normal and reverse rotations of the conveying means, in accordance with a sheet leading edge blank amount and a normal rotation convey amount of the sheet.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sheet feeding apparatus for feeding sheets one by one, and more particularly, it relates to a sheet feeding apparatus used with a recording apparatus such as a copying machine, a printer and the like.
2. Related Background Art
In the past, there has been proposed a sheet feeding apparatus used with a recording apparatus such as a copying machine, a printer and the like, in which, for example, sheets are fed out one by one by means of a semi-circular feed roller one rotation of which is controlled, and the fed sheet is supplied to a recording portion by a convey roller. The feed roller is provided with a flag in order to stop the feed roller after one rotation, and, by detecting the flag by a sensor (photo-interrupter or the like), completion of one rotation of the feed roller is detected. Further, in a drive system, a driving force of a convey roller rotatable normally and reversely is switched by a pendulum gear to effect connection or disconnection of transmission of the driving force. That is to say, when the convey roller is rotated in a normal direction, the driving force is transmitted to the feed roller by the pendulum gear; whereas, when the convey roller is rotated in a reverse direction, the transmission of the driving force is released. Incidentally, in the released position, a slide lever can be fitted into a support member of the pendulum gear to fixedly keep the posture of the gear, and, when the convey roller is rotated in the normal direction, only the convey roller can be rotated. The slide lever is disengaged from the support member of the pendulum gear when a carriage on which a recording head is mounted is shifted up to an end of the apparatus, with the result that the pendulum gear can freely be moved. In the condition that the fixing of the pendulum gear is released, when the convey roller is rotated in the normal direction, the feed roller is rotated together with the convey roller.
In a fundamental flow of the sheet in the sheet feeding, first of all, the carriage is shifted up to the end of the apparatus to rotate the convey roller and the feed roller, thereby feeding out a single sheet. When the completion of one rotation of the feed roller is detected by the sensor, the convey roller is rotated in the reverse direction by a predetermined amount, thereby releasing the transmission of the driving force to the feed roller. Here, when the carriage is returned toward a center of the apparatus, the slide lever is fitted into the support member of the pendulum gear to fix the posture of the gear, and only the convey roller is rotated, with the result that the sheet is conveyed to the recording portion only by the convey roller.
However, due to dispersion in sheet features, since a time period from when the rotation of the feed roller is started to when a leading edge of the sheet reaches a sheet leading edge detecting sensor (referred to as “PE sensor” hereinafter) is varied from sheet to sheet, when one rotation of the feed roller is completed, a distance from the convey roller (sheet leading edge detecting sensor) to the leading edge of the sheet is also varied from sheet to sheet. Thus, a dispersion correcting operation, i.e., a feeding operation of the leading edge to an initial position in which, as shown in
FIGS. 9A
to
9
D, after one rotation of the feed roller is completed, the sheet is set at an image leading portion recording position by reverse and normal rotations of the convey roller is required.
In
FIGS. 9A
to
9
D, “P” indicates the sheet;
100
denotes the convey roller;
101
denotes the PE sensor (sheet leading edge detecting sensor); and
102
denotes the recording head. Further, “β” indicates a normal convey distance of the sheet P from when the leading edge of the sheet is detected by the PE sensor
101
to when one rotation of the feed roller is completed; “ε” indicates a distance from the PE sensor
101
to a recording position of the recording head
102
; “γ” indicates a reverse rotation amount required for the above-mentioned drive switching; “σ” indicates a backlash correction amount when the normal rotation is effected again; “δ1” indicates a blank amount from the leading edge of the sheet to a leading portion of a record permitting area; and “δ2” indicates a blank amount from the leading portion of the record permitting area to an image leading end portion based upon image data.
FIG. 9A
shows a condition that the sheet P is fed out by the distance β after one rotation of the feed roller was completed.
FIG. 9B
shows a condition that the sheet is returned by rotating the convey roller reversely by an amount corresponding to by the sum of the reverse rotation amount γ required for the drive switching, an excessive fed amount in FIG.
9
A and the backlash correction amount σ of the drive switching portion. In this case, the reverse rotation amount of the convey roller is defined as (β−ε+σ−δ1), and diameters of the rollers are designed so that this reverse rotation amount becomes greater than the reverse rotation amount γ required for the drive switching without fail.
FIG. 9C
shows a condition that the sheet is fed out by rotating the convey roller in the normal direction by the backlash correction amount σ. As a result, the leading portion of the record permitting area is fed to the recording position (record starting position) of the recording head.
FIG. 9D
shows a condition that the sheet is fed out by rotating the convey roller in the normal direction by the blank amount δ2 with reference to the blank amount δ2 to the image leading portion based upon the image data. From this condition, the recording is started.
However, in the above-mentioned conventional apparatus, as mentioned above, since the leading edge of the sheet is returned up to the recording position of the recording head and then is fed out by the blank amount regardless of the image data, the shifting amount and time of the sheet required for the heading to the recording position become great, thereby worsening the record processing speed of the recording apparatus.
Concretely, for example, when β=20 mm, ε=8 mm, γ=5 mm, σ=1 mm, δ1=2 mm and δ2=4 mm, the shifting amount of the sheet required for the heading will be (β−ε+σ−δ1+σ−δ2)=16 mm.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide reduce a shifting amount of a sheet required for heading to a recording position, thereby improving a processing speed of an apparatus.
The present invention provides a sheet feeding apparatus comprising a sheet stacking means for supporting a sheet, a sheet feeding rotary member for feeding out the sheet from the sheet stacking means by one rotation control, a conveying means for conveying the sheet fed out by the sheet feeding rotary member to a recording means, a leading edge detecting means for detecting a leading edge of the sheet fed out by the sheet feeding rotary member, a driving means for rotating the conveying means in normal and reverse directions, and a control means for controlling the driving means, and wherein the control means controls a conveying amount of the sheet by the normal and reverse rotations of the conveying means, in accordance with a sheet leading edge blank amount obtained by adding a blank amount between the leading edge of the sheet and a leading portion of a record permitting area to a blank amount at a leading edge of image data, and, a normal rotation conveying amount of the sheet from when the leading edge of the sheet is detected by the leading edge detecting means to when one rotation of the sheet feeding rotary member is completed, referring to the blank amount at the leading edge of image data prior to initiation of feeding of the leading edge of the sheet to an initial position, when the sheet is conveyed to feed the leading edge of the sheet to an initial position after the sheet is fed out by one rotation of the sheet feeding rotary member.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a perspective view showing a schematic construction of a recording apparatus having an automatic sheet feeding apparatus;
FIGS. 2A and 2B
are explanatory views showing a gear switching portion between a conveying roller and a sheet feeding roller;
FIG. 3
is a plan view of the automatic sheet feeding apparatus;
FIGS. 4A and 4B
are side views of the automatic sheet feeding apparatus;
FIGS. 5A and 5B
are side views of a sheet feeding roller portion of the automatic sheet feeding apparatus;
FIG. 6
is a flow chart showing control in a sheet feeding operation;
FIGS. 7A
,
7
B and
7
C are explanatory views of a feeding operation of a leading edge to an initial position;
FIGS. 8A
,
8
B and
8
C are explanatory views of a feeding operation of a leading edge to an initial position; and
FIGS. 9A
,
9
B,
9
C and
9
D are views of for explaining a conventional technique.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention will now be fully explained in connection with a sheet feeding apparatus and a recording apparatus according to an embodiment with reference to the accompanying drawings.
Now, a sheet feeding apparatus and a recording apparatus according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. Incidentally, in this embodiment, an ink jet recording apparatus having an automatic sheet feeding apparatus as the sheet feeding apparatus will be explained as an example.
FIG. 1
is a perspective view showing a schematic construction of the recording apparatus having the automatic sheet feeding apparatus in this embodiment. In
FIG. 1
, a sheet feeding portion
11
as the automatic. sheet feeding apparatus is attached to a main body
3
of the apparatus at an angle of 30 to 60 degrees. Sheets P set in the sheet feeding portion
11
are to be discharged horizontally after recording. The sheet feeding portion
11
includes a sheet feeding roller
5
, a separation claw
17
, a movable side guide
19
, a base
20
, a pressure plate
21
(all are shown in FIG.
3
), pressure plate springs
22
(FIGS.
5
A and
5
B), gears
25
to
30
, a release cam
31
, a claw spring
32
, a releasing lever
33
and a releasing cam
35
(all are shown in FIGS.
4
A and
4
B). Normally, the pressure plate
21
is lowered to a position shown in
FIG. 5A
by the release cam
31
, with the result that the sheet P is spaced apart from the sheet feeding roller
5
.
In a condition that the sheets P are set, a driving force of a convey roller
36
(
FIGS. 7A
to
7
C and
FIGS. 8A
to
8
C) is transmitted to the sheet feeding roller
5
and the release cam
31
through the gears
25
to
30
. When the release cam
31
is separated from the pressure plate
21
, the pressure plate
21
is lifted up to a position shown in
FIG. 5B
, with the result that the sheet P contacts with the sheet feeding roller
5
. The sheets P are picked up by rotation of the sheet feeding roller
5
and are separated one by one by the separation claw
17
. The separated sheet P is sent to a sheet convey portion
12
. The sheet feeding roller
5
and the release cam
31
are rotated by one rotation until the sheet P is sent to the sheet convey portion, and, in the condition that the pressure plate
21
is released from the sheet feeding roller
5
is restored again, the driving force from the convey roller
36
is disconnected, and this initial condition is maintained.
The sheet convey portion includes the convey roller
36
, a pinch roller
37
, a PE sensor
42
(all are shown in
FIGS. 7A
to
7
C and
FIGS. 8A
to
8
C), and a platen
46
(FIG.
1
). The sheet P sent to the sheet convey portion is guided by the platen
46
, a pinch roller guide (not shown) and an upper guide (not shown) and is sent to a pair of rollers comprised of the convey roller
36
and the pinch roller
37
. The PE sensor
42
is disposed in front of the pair of rollers. When a leading edge of the sheet P is detected by the PE sensor
42
, a printing position on the sheet P is determined by the PE sensor
42
. The pinch roller
37
is biased by a pinch roller spring (not shown) via the pinch roller guide so that the pinch roller is urged against the convey roller
36
, thereby providing a conveying force for the sheet P.
The sheet P sent by the pair of rollers
36
,
37
is advanced on the platen
46
by the pair of rollers
36
,
37
rotated by an LF motor (convey motor)
47
; meanwhile, the recording is effected by a recording head
49
on the basis of predetermined image information. Incidentally, the recording head
49
is of ink jet recording type for effecting the recording by discharging ink, and in the illustrated embodiment, the recording head is integrally formed with an ink tank to form an easy replaceable ink jet recording head. The recording head has electrical/thermal converters so that ink is discharged from a discharge port by growth and contraction of a bubble generated in the ink by film-boiling caused by thermal energy created by energizing the electrical/thermal converter in response to a record signal, thereby effecting the recording.
In
FIGS. 2A and 2B
, a switching output gear
81
is integrally formed with the convey roller
36
and is reversibly rotated by the LF motor
47
. A switching arm
82
has a base portion rotatably mounted on a support shaft
36
a
integral with the convey roller
36
. A switching output gear
83
is rotatably mounted on a free end of the switching arm
82
and can be engaged with the input gear
25
by rotation of the switching arm
82
to transmit normal rotation of the convey roller
36
to the input gear
25
and the associated sheet feeding roller
5
. A control apparatus
80
controls rotations of the LF motor
47
and the convey roller
36
in a manner which will be described later.
A carriage portion (recording portion)
15
includes a carriage
50
to which the recording head
49
is attached, a guide shaft
51
for guiding reciprocal scan of the carriage
50
in a direction perpendicular to a conveying direction of the sheet P, a guide
52
for holding a rear end (at an upper part of the apparatus) of the carriage
50
to maintain a predetermined gap between the recording head
49
and the sheet P, a timing belt
55
for transmitting drive of a carriage motor
53
to the carriage
50
, an idle pulley
56
for applying tension to the timing belt
55
, and a flexible cable
57
for transmitting a head drive signal from an electric substrate to the recording head
49
. The recording head
49
is scanned together with the carriage
50
in the direction perpendicular to the sheet conveying direction, so that the image is formed on the sheet P being conveyed on the platen
46
.
A sheet discharge portion includes sheet discharge rollers
59
, transmission rollers
60
for transmitting the driving force of the convey roller
36
to the sheet discharge rollers
59
, spurs
61
for aiding sheet discharging, and a sheet discharge tray
62
. The sheet P is discharged onto the sheet discharge tray
62
by the sheet discharge rollers
59
and the spurs
61
without distorting the image on the sheet P. Incidentally, the spurs are so designed as to have small contact area with the sheet, so that, even when the spurs are contacted with the imaged surface of the sheet, the image on the sheet is not distorted.
A cleaning portion
16
includes a pump
63
for cleaning the recording head
49
, a cap
65
for preventing drying of the recording head
49
, and a drive switching lever
66
for switching the driving force of the convey roller
36
between the sheet feeding portion
11
and the pump
63
. When the sheet is fed, except for cleaning, the drive switching lever
66
is in a condition that the lever is entered into a hole
82
c
of the switching arm
82
shown in
FIG. 2A
, so that, since the switching output gear
83
to be rotated around a center of the convey roller
36
is fixed or secured at a predetermined position, the driving force of the convey roller
36
is not transmitted to the pump
63
and the sheet feeding portion
11
.
By shifting the carriage
50
, when the drive switching lever
66
is shifted in a direction shown by the arrow A in
FIG. 1
, the drive switching lever
66
is disengaged from the hole
82
c
of the switching arm
82
, and the switching output gear
83
is shifted as shown in
FIGS. 2A and 2B
by the normal or reverse rotation of the convey roller
36
. In a condition that the carriage
50
is secured at the shifted position in the direction A, when the convey roller
36
is rotated normally, the driving force of the LF motor
47
is transmitted to the sheet feeding portion
11
; whereas, when the convey roller
36
is rotated reversely, the driving force of the LF motor
47
is transmitted to the pump
63
.
Further, as the LF motor for driving the convey roller
36
and the carriage motor
53
for driving the carriage
50
, stepping motors rotated by predetermined angles in response to signals sent from drivers (not shown) are used.
As shown in
FIG. 3
, the sheet feeding roller
5
is provided with a sensor plate
69
having a diameter smaller than a diameter of a sheet feeding rubber
67
attached to the sheet feeding roller
5
. The sensor plate
69
has a cut-out portion so that, only when the sheet feeding roller
5
and the release cam
31
are located at their initial positions (
FIG. 5A
) where the pressure plate
21
is released, light from a roller sensor comprised of a photo-interrupter directly attached to the electric substrate (not shown) is not interrupted. By detecting the condition of the sensor plate
69
, an angular position of the sheet feeding roller
5
and an angular position of the release cam
31
operated in synchronous with the sheet feeding roller
5
with the same phase can be detected, thereby providing a control timing of the sheet P in a sheet feeding sequence.
Next, main parts of the sheet feeding portion
11
will be described. Various parts of the sheet feeding portion
11
are attached to the base
20
to form a unit. As shown in
FIG. 3
, in the illustrated embodiment, the sheet feeding portion
11
serves to feed the sheet by utilizing one lateral edge of the sheet P as a reference, and a sheet standard (reference) surface is constituted by an inner wall of a right side plate of the base
20
. As shown in
FIG. 5A
, the base
20
has a shape so that the pressure plate
21
can be retarded as shown in FIG.
5
A. Further, the base is provided with recessed portions for positioning the pressure plate springs
22
at positions substantially opposed to roller portions
5
c
of the sheet feeding roller
5
.
The pressure plate
21
is connected to the base
20
via pressure plate shafts
21
b
provided on both upper end portions of the pressure plate so that the pressure plate can be rotated around the pressure plate shafts
21
b
. As shown in
FIG. 3
, separation pads
73
made of material having relatively high frictional coefficient such as synthetic leather are adhered to the pressure plate
21
at positions opposed to the roller portions
5
c
of the sheet feeding roller
5
, so that, when the number of the sheets on the pressure plate becomes few, double-feeding is prevented. Further, the movable side guide
19
slidable in a left-and-right direction is attached onto the pressure plate
21
, so that, even when different size sheets P are used, one lateral edges of the sheets can be aligned by utilizing the sheet standard surface.
The sheet feeding roller
5
is rotatably supported by the base
20
at its both ends. The sheet feeding roller
5
is a integrally molded plastic part including a shaft portion
5
b
and the roller portions
5
c
, and the sheet feeding rubbers
67
for conveying the sheet P are provided on outer peripheral surfaces of the roller portions
5
c
. Each roller portion
5
c
has a D-cut (semicircular) shape. Further, sub-rollers
75
each having a radius smaller than a radius of the sheet feeding rubber
67
attached to the sheet feeding roller
5
by 0.5 mm to 3.0 mm are provided on both sides of the roller portion
5
c
, so that contamination of the image or positional deviation of the sheet feeding roller
5
is prevented by not contacting the sheet P with the roller rubbers
67
of the sheet feeding roller
5
other than the sheet feeding.
Further, in the illustrated embodiment, there are two roller portions
5
c
along the axial direction, which are spaced apart from the sheet standard surface by about 40 mm and about 170 mm, respectively. Accordingly, a recording sheet having A4 size is conveyed by the two roller portions
5
c
, and a post card is conveyed by only the single roller portion
5
c
near the sheet standard surface.
When the drive switching lever
66
of the cleaning portion
16
is shifted in the direction A in
FIG. 1
by the carriage
50
to rotate the convey roller
36
normally, the switching output gear
83
is shifted to be engaged by the input gear
25
, thereby transmitting the driving force to the sheet feeding portion
11
(refer to FIG.
2
B). In this case, since the switching output gear
83
is rocked toward the direction engaging with the input gear
25
to engage by the latter, so long as these gears once meshed with each other, even when the carriage
50
is retarded to a direction opposite to the direction A, the engagement between the gears is maintained to continue the transmission of the driving force.
The input gear
25
transmits the driving force to a sheet feeding roller gear
28
coupled to the sheet feeding roller
5
through idler gears
26
,
27
. The sheet feeding roller
5
is rotated by the sheet feeding roller gear
28
to convey the sheet P.
Further, as shown in
FIGS. 4A and 4B
, the sheet feeding roller gear
28
transmits the driving force to the release cam
31
through a clutch gear
29
and an idler gear
30
. In this case, the sheet feeding roller
5
and the release cam
31
are designed and arranged so that phases thereof are aligned with each other for each rotation. As a result, as shown in
FIG. 4B
, in the condition that the pressure plate
21
is released, as shown in
FIG. 5A
, the sheet feeding roller
5
is designed and arranged so that the semi-circular portions are opposed to the pressure plate
21
.
The release cam
31
is so shaped that it releases the pressure plate
21
only between the angle of about 120 degrees of semi-circular portions of the sheet feeding roller
5
and that it contacts with the sheet P or the pressure plate
21
with an urging force of about 200 g to about 500 g when portion of the sheet feeding roller
5
other than the semi-circular portions is opposed to the pressure plate
21
. Further, the release cam
31
releases the pressure plate
21
by depressing a depressed portion
21
c
of the pressure plate
21
protruded from a hole formed in the right side plate of the base
20
(refer to FIG.
4
B).
In this case, the pressure plate cam
76
attached to the base
20
is depressed by a cam
21
d
near the depressed portion
21
c
of the pressure plate
21
, with the result that the pressure plate cam
76
is rotated around a center
76
b
. And, a cam (not shown) outside of the left roller portion
5
c
is lowered by the pressure plate cam
76
. As a result, even when the depressed portion
21
c
of the pressure plate
21
is depressed, the pressure plate
21
is not inclined with respect to the base
20
, so that the pressure plate is released substantially horizontally.
The clutch gear
29
is provided at its interior with a clutch spring
77
(
FIG. 3
) so that the clutch spring
77
is tightened in a direction B in
FIG. 4A
, thereby preventing reverse rotation. Thus, when the switching from the sheet feeding portion
11
to the sheet convey portion is effected by the reverse rotation of the LF motor
47
or when the jammed sheet is removed or pulled by the operator, the sheet feeding roller
5
is not subjected to reverse rotation.
The separation claw
17
can be rotated around a center
17
b
and is biased by the claw spring
32
against the sheet P or the pressure plate
21
with an elastic force of about 20 g to about 100 g. The separation claw
17
serves to separate recording sheets P comprised of normal sheets and is positioned near the sheet standard surface as shown in
FIGS. 4A and 4B
to cover a corner of the sheet P in a triangular fashion. Since the sheets P are subjected to resistance from the triangular claw, the sheets can be separated one by one. Further, separation of thick sheets other than normal sheet is effected by abutting the sheets against a lower guide portion
20
b
(
FIGS. 5A and 5B
) of the base
20
(without engaging the separation claw
17
with the sheets) to utilize frictional resistance of the lower guide portion
20
b
, thereby separating the sheets one by one.
The releasing lever
33
and the releasing cam
35
. (
FIG. 4A
) are provided in coaxial with the release cam
31
(FIG.
4
B). The releasing lever
33
and the releasing cam
35
are not synchronous with the release cam
31
but are operated independently and aid to set the sheets P by the operator. The releasing lever
33
and the releasing cam
35
are interconnected through a gear.
The releasing lever
33
assumes (1) a feed position, (2) a thick sheet set position and (3) a normal sheet set position. An angle between these positions is selected to about 20 degrees to about 50 degrees. A ratio between the gears are set so that the releasing cam
35
is rotated by about 90 degrees in correspondence to three positions of the releasing lever
33
.
(1) In the feed position, the releasing cam
35
does not act on the depressed portion
21
c
of the pressure plate
21
and a depressed portion
17
c
of the separation claw
17
. This position is selected during normal sheet feeding.
(2) In the thick sheet set position, since the releasing cam
35
depresses only the depressed portion
21
c
of the pressure plate
21
, the separation claw
17
is lowered to follow the pressure plate
21
, with the result that the thick sheets can be set without engaging by the separation claw
17
.
(3) In the normal sheet set position, since the releasing cam
35
depresses both the depressed portion
21
c
of the pressure plate
21
and the depressed portion
17
c
of the separation claw
17
, the separation claw
17
is lifted with respect to the pressure plate
21
, with the result that the normal sheets can be set with engaging by the separation claw
17
.
Incidentally, the above-mentioned group of gears (except for the sheet feeding roller shaft
79
), separation claw
17
, releasing lever
33
and releasing cam
35
are provided on shafts provided on the right side plate of the base
20
and are rotated around the shafts. Next, function and control of the sheet feeding portion
11
in the sheet feeding will be fully explained.
FIG. 6
is a flow chart showing entire control. Although such control can be divided into control effected when the sheet feeding roller
5
is in the predetermined initial position and control effected if the sheet feeding roller is not in the predetermined initial position (trouble condition), in the illustrated embodiment, only the control effected when the sheet feeding roller
5
is in the predetermined initial position will be described.
In
FIG. 6
, in response to a sheet feeding start signal, first of all, in S
200
, while referring the image data from the host (for example, a computer to which the recording apparatus is connected), a blank amount at the leading edge of the image data is read out. In S
202
, the carriage
50
is shifted to shift the drive switching lever
66
so that the driving force of the convey roller
36
can be transmitted to the sheet feeding portion
11
(ASF position).
Then, in S
203
, the condition of the sheet feeding roller is judged (by the roller sensor). If the sheet feeding roller
5
is in the initial position, the program goes to S
204
; whereas, if the sheet feeding roller
5
is not in the initial position, initialization of the sheet feeding roller
5
is effected (S
207
). When the sheet feeding roller
5
is in the initial position, in S
204
, the sheet feeding roller
5
is rotated and, in S
205
, the edge of the sensor plate
69
(change from dark to bright of the sensor) is detected. In S
206
, by counting the number (N1) of drive pulses of the LF motor
47
after the detection, the angular position of the sheet feeding roller
5
can be controlled correctly, thereby effecting high accurate control.
When the sheet feeding roller
5
is rotated by about 60 degrees to bring cylindrical portions of the sheet feeding rubbers
67
to a position opposed to the sheet P, the release cam
31
rotated in synchronous with the sheet feeding roller
5
releases the pressure plate
21
. As a result, since the sheet P is urged against the sheet feeding rubbers
67
by the biasing forces of the pressure plate springs
72
, the conveying force for the sheet P is generated. After the pressure plate
21
is released, the carriage
50
can be retarded, so that the initializing operation (ink pre-discharge, wiping and the like) of the recording head
49
can freely be performed during the sheet feeding.
In S
208
, the leading edge of the sheet P being conveyed is detected by the PE sensor
42
. If the PE sensor
42
is turned ON till the sheet feeding roller
5
is rotated by the predetermined amount, in S
209
, data (N2) of the position of the leading edge of the sheet is sought on the basis of the angular position of the sheet feeding roller
5
when the PE sensor
42
is turned ON and such data is stored. Then, in S
210
, by continuing the rotation of the sheet feeding roller
5
until the roller sensor is turned ON, the sheet P is conveyed ahead of the pair of rollers comprised of the convey roller
36
and the pinch roller
37
. In S
211
, when the roller sensor is turned ON, the rotation of the convey roller
36
is stopped, and the position data (N3) thereof is stored.
In the feeding operation (heading) of the leading edge to the initial position for setting the leading edge blank (S
212
), the convey roller
36
is rotated reversely by the predetermined amount to disengage the switching output gear
83
from the input gear
25
, thereby shifting the gear
83
up to the position shown in FIG.
2
A. Thereafter, the convey roller
36
is rotated normally by the predetermined amount. When this feeding operation (heading) of the sheet is finished, the sheet feeding operation is completed.
Next, calculation of the normal and reverse rotation amounts of the convey roller in the feeding operation of the leading edge to the initial position for setting the leading edge blank will be explained with reference to
FIGS. 7A
to
7
C and
FIGS. 8A
to
8
C.
In
FIGS. 7A
to
7
C and
FIGS. 8A
to
8
C, “β” indicates a distance between the PE sensor
42
and the leading edge of the sheet when the sheet feeding roller
5
is stopped (completion of one rotation thereof), calculated on the basis of the data N2, N3; “γ” indicates a pre-set minimum reverse rotation amount required for switching the switching output gear
83
from the position shown in
FIG. 2B
to the position shown in
FIG. 2A
; “σ” indicates a pre-set normal rotation amount required for removing backlash; “δ” indicates a blank amount at the leading edge of the sheet obtained by adding the blank δ2 for the image leading portion based upon the image data referred before initiation of the feeding operation (heading) to the pre-set blank δ1 between the leading edge of the sheet and the leading portion of the record permitting area (δ1+δ2); and “ε” indicates a pre-set distance from the PE sensor
42
to the recording position (write starting position) of the recording head
49
.
In the illustrated embodiment, after the sheet feeding roller
5
is rotated by one rotation, when the feeding operation of the leading edge of the sheet to the initial position is effected by the reverse and normal rotations of the convey roller
36
, before the initiation of such feeding operation, by referring the blank at the leading edge of the image data, in accordance with the blank amount at the leading edge of the sheet obtained by adding the blank at the leading edge of the image data to the blank between the leading edge of the sheet and the leading portion of the record permitting area, and in accordance with the normal rotation amount of the sheet P until one rotation of the sheet feeding roller
5
is completed after the leading edge of the sheet was detected, the conveying amount of the sheet P achieved by the reverse and normal rotations of the convey roller
36
is controlled.
Concretely, as shown in
FIG. 7A
, after the sheet feeding roller
5
is rotated by one rotation, if the relationship between the distances is (ε−σ+γ<β−δ) (i.e., if the blank amount is small), as shown in
FIG. 7B
, the convey roller
36
is rotated reversely in a direction shown by the thick arrow to convey the sheet P in the reverse direction by a distance {(β−δ)−(ε−σ)}, so that the position of the switching output gear
83
is fixed by the drive switching lever
66
. Thereafter, as shown in
FIG. 7C
, the convey roller
38
is rotated again normally in a direction shown by the thick arrow to convey the sheet P in the normal direction by the distance σ.
More specifically, for example, similar to the conventional case, when β=20 mm, ε=8 mm, γ=5 mm, σ=1 mm, δ1=2 mm and δ2=4 mm, the shifting amount of the sheet required for the feeding operation of the leading edge to the initial position becomes {(β−δ)−(ε−σ)+σ}=8 mm, which is greatly reduced in comparison with
16
mm in the conventional case.
On the other hand, as shown in
FIG. 8A
, after the sheet feeding roller
5
is rotated by one rotation, if the relationship between the distances is (ε−σ+γ>β−δ) (i.e., if the blank amount is great), as shown in
FIG. 8B
, the convey roller
36
is rotated reversely in a direction shown by the arrow to convey the sheet P in the reverse direction by the distance γ, so that the position of the switching output gear
83
is fixed by the drive switching lever
66
. Thereafter, as shown in
FIG. 8C
, the convey roller
38
is rotated again normally in a direction shown by the arrow to convey the sheet P in the normal direction by a distance {ε−(β−γ−δ)}.
As is in the above case, for example, similar to the conventional case, when β=20 mm, ε=8 mm, γ=5 mm, σ=1 mm and δ1=2 mm and further when δ2=8 mm (more disadvantageous in the conventional case), the shifting amount of the sheet required for the feeding operation of the leading edge to the initial position becomes {γ+ε−(β−γ−δ)}=6 mm, which is further greatly reduced in comparison with 16 mm in the conventional case.
When the feeding operation (heading) of the leading edge to the initial position to set the leading edge blank is completed in this way, the proper heading amount is set, and the recording can be started.
With the arrangement as mentioned above, according to the illustrated embodiment, the conveying amount regarding feeding operation of the leading edge of the sheet to the initial position can be minimized, thereby improving the processing speed of the apparatus.
Incidentally, if the record starting position of the recording head along the sheet conveying direction is varied with recording modes, the blank amount at the leading edge of the image data and the recording mode prior to the initiation of the feeding operation of the leading edge of the sheet to the initial position are referred to, and, on the basis of such information, a distance ε2 from the PE sensor
42
to a record starting position of the recording head (recording head element) corresponding to said recording mode is used, in place of the above-mentioned distance ε. In this way, the conveying amount regarding feeding operation of the leading edge of the sheet to the initial position can be further reduced.
In the illustrated embodiment, while an example that the printer is used as the recording apparatus was explained, the present invention is not limited to such an example, but may be applied, for example, to other recording apparatuses such as a copying machine, a facsimile and the like, and, by applying the present invention to a sheet feeding apparatus used with such a recording apparatus, the same advantages can be achieved.
Further, in the illustrated embodiment, while an example that the sheet feeding apparatus is detachably attachable to the recording apparatus was explained, the present invention is not limited to such an example, but may be applied, for example, to a sheet feeding apparatus integrally incorporated into a recording apparatus, and, by applying the present invention to a sheet feeding apparatus, the same advantages can be achieved.
Finally, in the illustrated embodiment, while an example that the recording system is of an electrophotographic type was explained, the present invention is not limited to such an example, but may use, for example, other recording systems such as an ink jet recording system.
Claims
- 1. A sheet feeding apparatus comprising:sheet stacking means for supporting a sheet; a sheet feeding rotary member for feeding out the sheet from said sheet stacking means by one rotation control; conveying means for conveying the sheet fed out by said sheet feeding rotary member to recording means; leading edge detecting means for detecting a leading edge of the sheet fed out by said sheet feeding rotary member; driving means for rotating said conveying means in normal and reverse directions; and drive transmission means for transmitting a driving force from said driving means to said sheet feeding rotary member. wherein said drive transmission means comprises an output gear and an input gear, said output gear capable of shifting to an engage position where said output gear is engaged with said input gear in the normal rotation of said conveying means in order to transmit the driving force and shifting to a disengage position where said output gear is disengaged from said input gear in the reverse rotation of said conveying means in order to release of transmission of the driving force, and fixing means for fixing or releasing a position of said output gear; and control means for controlling said driving means so as to feed the leading edge of the sheet to the initial position by the normal and reverse rotations of said conveying means after the sheet is fed out by one rotation of said sheet feeding rotary member, in accordance with a sheet leading edge blank amount based on a blank amount at the leading edge of the image data referred prior to initiation of a feeding operation of the leading edge of the sheet to an initial position, and, in accordance with a normal rotation convey amount of the sheet from when the leading edge of the sheet is detected by said leading edge detecting means to when one rotation of said sheet feeding rotary member is completed.
- 2. A sheet feeding apparatus according to claim 1, wherein said sheet leading edge blank amount is obtained by adding a blank amount between the leading edge of the sheet and a leading portion of a record permitting area to a blank amount at a leading edge of image data.
- 3. A sheet feeding apparatus according to claim 2, wherein, when it is assumed that a normal rotation convey distance from when the leading end of the sheet is detected by said leading edge detecting means to when one rotation of said sheet feeding rotary member is completed is β, a reverse rotation convey amount required for shifting said switching output gear to the position where said switching output gear is disengaged from said input gear is γ, a normal rotation convey amount required for removing backlash in the normal rotation after the reverse rotation is σ, a blank amount at the leading edge of the sheet is δ, and a normal rotation convey amount from said leading edge detecting means to a recording position is ε, if a relationship between said distances is (ε−σ+γ<β−δ) after said sheet feeding rotary member is rotated by one rotation, said conveying means is rotated reversely to convey the sheet in the reverse direction by a distance {(β−δ)−(ε−σ)}, so that the position of said switching output gear is fixed by said fixing means, and, thereafter, said conveying means is rotated normally to convey the sheet in the normal direction by said distance σ, and, if said relationship is (ε−σ+γ>β−δ), said conveying means is rotated reversely to convey the sheet in the reverse direction by said distance δ, so that the position of said switching output gear is fixed by said fixing means, and, thereafter, said conveying means is rotated normally to convey the sheet in the normal direction by a distance {ε−(β−γδ)}.
- 4. A sheet feeding apparatus according to claim 2, wherein, if a record starting position of said recording means in a sheet conveying direction is varied with recording modes, the blank amount at the leading edge of the image data and the recording mode prior to the initiation of the feeding operation of the leading edge of the sheet to the initial position are referred to, and, when it is assumed that a normal rotation convey distance from when the leading end of the sheet is detected by said leading edge detecting means to when one rotation of said sheet feeding rotary member is completed is β, a reverse rotation convey amount required for shifting said switching output gear to the position where said switching output gear is disengaged from said input gear is γ, a normal rotation convey amount required for removing backlash in the normal rotation after the reverse rotation is σ, a blank amount at the leading edge of the sheet is δ, and a normal rotation convey amount from said leading edge detecting means to a recording position of said recording means corresponding to said recording mode is ε2, if a relationship between said distances is (ε2−σ+γ<β−δ) after said sheet feeding rotary member is rotated by one rotation, said conveying means is rotated reversely to convey the sheet in the reverse direction by a distance {(β−δ)−(ε2−σ)}, so that the position of said switching output gear is fixed by said fixing means, and, thereafter, said conveying means is rotated normally to convey the sheet in the normal direction by said distance σ, and, if said relationship is (ε2−σ+γ>β−δ), said conveying means is rotated reversely to convey the sheet in the reverse direction by said distance y, so that the position of said switching output gear is fixed by said fixing means, and, thereafter, said conveying means is rotated normally to convey the sheet in the normal direction by a distance {ε2−(β−γ−δ)}.
- 5. A recording apparatus comprising:sheet stacking means for supporting a sheet; a sheet feeding rotary member for feeding out the sheet from said sheet stacking means by one rotation control; conveying means for conveying the sheet fed out by said sheet feeding rotary member to recording means; leading edge detecting means for detecting a leading edge of the sheet fed out by said sheet feeding rotary member; driving means for rotating said conveying means in normal and reverse directions; control means for controlling said driving means; and recording means for recording on the sheet conveyed by said conveying means; and wherein said control means controls a conveying amount of the sheet by the normal and reverse rotations of said conveying means, in accordance with a sheet leading edge blank amount obtained by adding a blank amount between the leading edge of the sheet and a leading portion of a record permitting area to a blank amount at a leading edge of image data, and, in accordance with a normal rotation convey amount of the sheet from when the leading edge of the sheet is detected by said leading edge detecting means to when one rotation of said sheet feeding rotation member is completed, to a blank amount at the leading edge of the image data prior to initiation of a feeding operation of the leading edge of the sheet to an initial position, when the sheet is conveyed to feed the leading edge of the sheet to the initial position by the normal and reverse rotation of said conveying means after the sheet is fed out by one rotation of said sheet feeding rotary member.
- 6. A recording apparatus according to claim 5, wherein said recording means is of an ink jet recording type in which ink is discharged onto the sheet to record.
Priority Claims (1)
Number |
Date |
Country |
Kind |
10-190073 |
Jul 1998 |
JP |
|
US Referenced Citations (7)
Foreign Referenced Citations (2)
Number |
Date |
Country |
401009767 |
Jan 1989 |
JP |
404062077 |
Jan 1989 |
JP |