Information
-
Patent Grant
-
6334725
-
Patent Number
6,334,725
-
Date Filed
Wednesday, August 16, 200023 years ago
-
Date Issued
Tuesday, January 1, 200222 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
- Fitzpatrick, Cella, Harper & Scinto
-
CPC
-
US Classifications
Field of Search
US
- 074 409
- 074 4115
- 074 412 R
- 074 413
- 074 435
- 074 448
- 074 462
- 271 1013
- 271 114
- 271 147
- 400 624
- 400 629
- 400 636
- 400 6362
-
International Classifications
-
Abstract
In a drive transmitting apparatus for selectively transmitting a driving force from a drive source to a driving member through clutch means to achieve a positive switching operation, the clutch means includes an output gear having a non-entirely toothed portion not including a predetermined number of teeth in a tooth width-wise direction and an entirely toothed portion having no non-toothed portion, a gear opposed to the non-toothed portion of the output gear and rotated by a driving force, a trigger gear meshed with the entirely toothed portion of the output gear and freely rotatable with respect to a shaft and movable in a thrust direction, and ratchet portions formed on opposed side surfaces of the gear and the trigger gear so that, when the trigger gear is slid in the thrust direction to engage the ratchet portions by each other, a driving force is transmitted from the gear to the output gear.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a drive transmitting apparatus for selectively transmitting a driving force from a drive source to a driving member through clutch means and an image forming apparatus using such a drive transmitting apparatus.
2. Related Background Art
Among drive transmitting mechanisms for image forming apparatuses, there is a mechanism in which a partially non-toothed gear having a non-toothed portion is used as clutch means for effecting connection and disconnection of a driving force, as disclosed in Japanese Patent Application Laid-open No. 10-274312. According to this mechanism, in a normal condition, the non-toothed portion is opposed to a drive gear to block transmission of the driving force to the partially non-toothed gear, and, when the partially non-toothed gear is slightly rotated by trigger means such as a solenoid, the drive gear is engaged by the partially non-toothed gear, thereby transmitting the driving force to the partially non-toothed gear. When the partially non-toothed gear is rotated by one revolution, since the transmission of the driving force is blocked again by the non-toothed portion, this mechanism acts as a one revolution controlling clutch.
On the other hand, as disclosed in Japanese Patent Application Laid-open No. 9-141966, there is an apparatus in which a driving force is switched by connecting a disconnecting clutch means of a driving system by utilizing a movement of a carriage. In this apparatus, a pair of clutch gears having triangular teeth (ratchets) formed on opposed side surfaces and engageable with each other are provided, and, when one of the clutch gears is pushed toward the other clutch gear by the carriage, the triangular teeth are engaged by each other, thereby transmitting a driving force. According to this arrangement, a construction in which one of the clutch gears is pushed by using a solenoid is not required, and trigger for transmitting the driving force can be achieved by using the movement of the carriage itself, thereby reducing the cost.
However, in the above-mentioned conventional technique, when the drive gear begins to be engaged by the partially non-toothed gear, the tops of the teeth may abut against each other to cause poor engagement, with the result that noise may be generated or an out-of-phase condition of a motor may be caused. In the technique disclosed in Japanese Patent Application Laid-open No. 10-274312, although special tooth configurations in which inclined surfaces are formed on the teeth are adopted to avoid such inconvenience, it is difficult to set the optimum tooth configurations.
On the other hand, in the technique disclosed in Japanese Patent Application Laid-open No. 9-141966, as shown in
FIG. 9
, a trigger tooth portion
901
b
complementary to the non-toothed portion is provided aside the non-toothed portion
901
a
of the partially non-toothed gear
901
, and the drive gear
902
is opposed to the non-toothed portion
901
a
and a driven gear
903
is disposed in an engagement relationship to the trigger tooth portion
901
b.
The driven gear
903
has no self-driving ability and can be moved in a thrust direction so as to contact with and separate from the drive gear
902
. When the driven gear
903
is urged against the drive gear
902
, the opposed triangular teeth (not shown) engageable with each other are meshed with each other, thereby transmitting the driving force of the drive gear
902
to the driven gear
903
. As a result, the driving force from the drive gear
902
is transmitted to the partially non-toothed gear
901
through the driven gear
903
, thereby starting rotation of the partially non-toothed gear
901
. When the partially non-toothed gear
901
is rotated by a predetermined amount, the drive gear
902
is engaged by a toothed portion
901
c
of the partially non-toothed gear
901
, with the result that, even when the urging of the driven gear
903
against the drive gear
902
is released, the driving force can be transmitted. In this case, so long as the phases of the gear portions of the gears
902
,
903
in a condition that the triangular teeth are engaged by each other are aligned with each other, since the tooth of the drive gear
902
is smoothly engaged by the toothed portion
901
c
of the partially non-toothed gear
901
, the tops of the teeth of both gears are prevented from abutting against each other to cause the poor engagement.
However, immediately before the partially non-toothed gear
901
is rotated by one revolution to return to its initial position again, when the driven gear
903
freely rotatable without transmission of the driving force due to disconnection of the triangular tooth from the triangular tooth of the drive gear
903
is engaged by the trigger tooth portion
901
b
again, the tops of the teeth of the driven gear
903
and the trigger tooth portion
901
b
may abut against each other to cause poor engagement.
In this case, so long as a condition that the driven gear
903
is urged against the drive gear
902
is maintained while the partially non-toothed gear
901
is rotated by one revolution, since the phases of the gears can be aligned even when the driven gear
903
and the trigger tooth portion
901
b
are engaged by each other again, this problem can be solved. However, meanwhile, the carriage must be retained in a predetermined position for urging the driven gear
903
against the drive gear
902
, thereby delaying the further recording operation.
SUMMARY OF THE INVENTION
The present invention aims to eliminate the above-mentioned conventional drawbacks, and an object of the present invention is to provide a drive transmitting apparatus in which a positive switching operation can be achieved without noise and/or poor drive transmission from a drive source, and an image forming apparatus using such a drive transmitting apparatus.
Another object of the present invention is to provide a drive transmitting apparatus comprising an output gear having a non-toothed portion not including a predetermined number of teeth and an entirely toothed portion having no non-toothed portion in a tooth width-wise direction, an input gear disposed at a position where it can be opposed to the non-toothed portion of the output gear and rotated by a driving force from a drive source, a trigger gear meshed with the entirely toothed portion of the output gear and rotatable with respect to a rotary shaft and movable in a thrust direction so as to contact with and separate from the output gear, and engagement portions provided on opposed side surfaces of the input gear and the trigger gear and engageable with each other, and wherein, when the input gear and the trigger gear are engaged by each other through the engagement portions, the driving force from the drive source is selectively transmitted to a driving member through clutch means for synchronizing phases of the input gear and the trigger gear, and an image forming apparatus using such a drive transmitting apparatus.
A further object of the present invention is to provide a drive transmitting apparatus in which a positive switching operation can be achieved without noise and/or poor drive transmission from a drive source by providing a construction in which tops of teeth of an input gear and an output gear do not abut against each other by aligning phases of engagement portions of the input gear and a trigger gear, and an image forming apparatus using such a drive transmitting apparatus.
A still further object of the present invention is to provide a drive transmitting apparatus in which engagement portions of two gears are constituted by ratchets having relative symmetrical configurations and engageable with each other so that, when phases of two gears are aligned, a gap is created between the ratchets.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a perspective view showing an ink jet printer according to a first embodiment of the present invention;
FIG. 2
is a schematic plan view of a sheet feeding mechanism;
FIGS. 3A
,
3
B and
3
C are explanatory views for explaining a drive transmitting system of clutch means;
FIGS. 4A and 4B
are development views of a gear train;
FIG. 5
is a schematic perspective view of a partially non-toothed gear;
FIGS. 6A
,
6
B,
6
C and
6
D are explanatory views showing ON/OFF conditions of a clutch depending upon positions of a slider;
FIGS. 7A and 7B
are explanatory views showing a relationship between an ASF-system output gear and an ASF-system clutch gear and an ASF-system clutch trigger gear;
FIG. 8
is a development view of a ratchet portion according to a second embodiment of the present invention; and
FIG. 9
is an explanatory view showing a conventional technique.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Now, an image forming apparatus using a drive transmitting apparatus according to an embodiment of the present invention will be explained with reference to the accompanying drawings.
[First Embodiment]
Here, an entire construction of the image forming apparatus will first be described, and then, the drive transmitting apparatus will be described. (Construction of image forming apparatus)
FIG. 1
is a perspective view showing an ink jet printer according to the first embodiment of the present invention, and
FIG. 2
is a schematic plan view of a sheet feeding mechanism.
In
FIGS. 1 and 2
, sheet feeding means
100
serve to separate and feed sheets stacked on a stacking tray
101
one by one by rotating a sheet feeding roller
102
. The sheet fed by the sheet feeding means
100
is conveyed onto a platen
301
by a conveying roller
302
forming a part of conveying means. After recording is effected on the sheet by recording means
200
, the sheet is discharged out of the printer.
The recording means
200
according to the illustrated embodiment are of serial ink jet recording type in which a carriage
201
is reciprocally movable along a guide shaft
202
and an ink cartridge
203
integrally including a recording head and an ink tank is mounted on the carriage
201
. By discharging ink from the recording head in response to a shifting movement of the carriage
201
, an ink image is formed on the sheet (recording medium) conveyed to a recording area defined between the opposed carriage
201
and platen
301
. Incidentally, at an end of a shifting range of the carriage
201
, recovery means
500
for recovering an ink discharging function of the recording head are disposed in a confronting relation to the recording head. The recovery means
500
serve to maintain a good recording condition of the recording head by recovering ink clogging and have a cap and pumping means. Further, in place of the ink cartridge
203
, a recording head and an ink tank may be provided independently.
Incidentally, according to the illustrated embodiment, in an ink discharging arrangement, an electrical/thermal converter is energized in response to a recording signal to generate thermal energy by which film boiling is generated in the ink, and the recording is effected by discharging the ink from a discharge port of the recording head by growth and contraction of a bubble generated by the film boiling. Regarding representative construction and principle, it is preferable that a fundamental principle is used, for example, as disclosed in U.S. Pat. No. 4,723,129 or No. 4,740,796. Although this system can be applied to both so-called on-demand type and continuous type, particularly, the on-demand type is effective because, by applying at least one drive signal for giving abrupt temperature increase exceeding nucleate boiling and corresponding to recording information to the electrical/thermal converter opposed to the sheet and a liquid flow path holding liquid (ink), thermal energy is generated in the electrical/thermal converter to generate the film boiling on an acting surface of the recording head, thereby forming a bubble corresponding to the drive signal in the liquid. Due to the growth and contraction of the bubble, the liquid is discharged from the discharge port, thereby forming at least one liquid droplet. When the drive signal has a pulse shape, since the growth and contraction of the bubble can be effected promptly and properly, particularly excellent liquid discharging can be achieved. This is more preferable.
(Driving Force Transmitting Arrangement)
Next, a driving force transmitting arrangement for transmitting a driving force to the sheet feeding means
100
and the conveying means such as the conveying roller
302
will be described.
In the illustrated embodiment, a driving force from a pulse motor
305
as a drive source is selectively transmitted to the sheet feeding means
100
, conveying roller
302
and recovery means
500
through clutch means
600
.
As shown in
FIG. 2
, the driving force from the pulse motor
305
is transmitted to a conveying gear
303
secured to one end of the conveying roller
302
through a speed reduction gear
306
, thereby rotating the conveying roller
302
. Further, the driving force can be transmitted to the sheet feeding means
100
and the recovery means
500
by an LF-system output gear
304
secured to the other end of the conveying roller
302
.
Now, a construction of the clutch means
600
will be fully explained.
FIGS. 3A
to
3
C are explanatory views for explaining a drive transmitting system of the clutch means
600
, where
FIG. 3A
is a plan view,
FIG. 3B
is a schematic right side view and
FIG. 3C
is a schematic left side view.
A drive base
601
is provided with an LF-system transmission gear
602
for receiving a driving force from the LF-system output gear
304
, an ASF-system output gear
603
for transmitting the driving force to the sheet feeding means
100
, and a pump-type output gear
604
for transmitting the driving force to the pump means
503
, so that the driving force from the LF-system transmission gear
602
is appropriately connected to or disconnected from the sheet feeding means
100
and the pump means
503
through a clutch mechanism which will be described later.
A driving force switching operation is effected by the shifting movement of the carriage
201
. That is to say, normally, although the driving force of the pulse motor
305
is transmitted to only the conveying roller
302
, when the pulse motor
305
is driven in a condition that the carriage
201
is in a predetermined position, the driving force is transmitted to the sheet feeding means
100
or the pump means
503
, thereby driving the sheet feeding means or the pump means.
Next, a gear train for transmitting the driving force will be explained with reference to
FIGS. 4A and 4B
. Incidentally,
FIGS. 4A and 4B
are development views of the gear train. In
FIGS. 4A and 4B
, both ends of a transmission shaft
605
having a key way
605
a
are rotatably supported by the drive base
601
, and the LF-system transmission gear
602
and a pump transmission gear
606
are mounted on the both ends through key portions
602
a
,
606
a
(
FIGS. 3B and 3C
) so that these gears cannot be rotated and are fixed with respect to a thrust direction.
Further, a slide gear
607
is mounted on the transmission shaft
605
at a central portion thereof for movement in the thrust direction, and the slide gear cannot be rotated with respect to the transmission shaft
605
by the presence of a key portion but can be rotated together with the transmission shaft. When the slide gear
607
is in a predetermined position, the slide gear is engaged by an idle gear
608
which is attached to the drive base
601
through an idle gear shaft
609
.
Further, both ends of an ASF-system clutch shaft
610
having a key way
610
a are rotatably supported by the drive base
601
, and there are provided a switching gear
611
having two gear portions
611
a,
611
b, an ASF-system clutch trigger gear
612
, an ASF-system clutch gear
613
as an input gear, and a biasing lever
614
(FIGS.
3
A and
3
C). The switching gear
611
is rotated together with the ASF-system clutch shaft
610
by the presence of a key portion, and two gear portions
611
a
,
611
b
have the same module and the same number of teeth. The gear
611
a
is meshed with the idle gear
608
, and, as shown in
FIG. 4B
, the gear
611
b
is engaged by the slide gear
607
when the latter is shifted.
The ASF-system clutch gear
613
is also rotated together with the ASF-system clutch shaft
610
by the presence of a key portion. On the other hand, the ASF-system clutch trigger gear
612
can freely be rotated with respect to the ASF-system clutch shaft
610
and can be shifted in the thrust direction. The biasing lever
614
is also rotatably mounted on the clutch shaft to regulate the position of the ASF-system clutch gear
613
in the thrust direction (In
FIGS. 4A and 4B
, the ASF-system clutch gear
613
abuts against the biasing lever
614
(not shown) to further leftward movement of the clutch gear).
An ASF-system output gear
603
having two gear portions and a cam portion is rotatably supported by the drive base
601
. A gear
603
a
serves to transmit a driving force to the sheet feeding means
100
and is meshed with an ASF-system input gear
103
(
FIG. 2
) to serve to transmit the driving force to the sheet feeding roller
102
through
104
,
105
(FIG.
2
). A gear
603
b
is an output gear meshed with the ASF-system clutch gear
613
and the ASF-system clutch trigger gear
612
.
FIG. 5
is a schematic perspective view of the partially non-toothed gear. The gear
603
b
has a non-toothed portion
603
d
opposed to the ASF-system clutch gear
613
and obtained by cutting away several teeth with leaving a tooth width w′ with respect to an entire tooth width W. That is to say, the gear
603
b
has the non-toothed portion
603
d
obtained by cutting away several teeth in the tooth width-wise direction, and an entirely toothed portion
603
e
having no non-toothed portion.
The biasing lever
614
biased by a spring is engaged by a cam portion
603
c
to regulate the phase of the non-toothed portion
603
d
of the ASF-system output gear
603
.
On the other hand, the drive transmission to the pump means
503
is similar to the drive transmission to the sheet feeding means. Namely, the driving force from the LF-system transmission gear
602
is transmitted to the coaxial pump-system transmission gear
606
, and a pump-system clutch gear
630
is disposed to mesh with the pump-system transmission gear
606
. The pump-system clutch gear
630
is rotatably supported on a pump-system clutch shaft
631
having both ends supported by the drive base
601
, and, adjacent to the pump-system clutch gear
630
, a pump-system clutch trigger gear
632
is rotatably supported on the pump-system clutch shaft
631
for a shifting movement in the thrust direction. Similar to the ASF-system output gear
603
, the pump-system output gear
604
has a non-toothed portion
604
a
and an entirely toothed portion
604
c
, and the non-toothed portion
604
a
is opposed to the pump-system clutch gear
630
. Further, a cam portion
604
b
of the pump-system output gear is engaged by biasing means (not shown) to regulate the phase of the non-toothed portion
604
a.
The slide gear
607
is positioned between regulating walls
616
a
and
616
b
of a slide holder
616
and is always biased toward the regulating wall
616
a
by a spring
617
. The slide holder
616
can be shifted along the transmission shaft
605
and the pump-system clutch shaft
631
so that a boss
616
c
can be engaged by a slider
619
(FIGS.
3
A and
3
B). That is to say, when the slider
619
is shifted, the slide holder
616
is also shifted, thereby shifting the slide gear
607
.
The shifting movement of the slider
619
is effected by the shifted carriage
201
abutting and pushing the slider. During the recording operation, the slider
619
and the carriage
201
are not engaged by each other, but, when the sheet feeding operation or the recovery operation is required, the slider
619
is shifted to a predetermined position by the shifting movement of the carriage.
FIGS. 6A
to
6
D show ON/OFF conditions of the clutch depending upon positions of the slider, and particularly
FIG. 6A
shows a normal conveying position. In this case, the clutch of the sheet feeding means and the clutch of the pump are both in an OFF condition, and only the conveying roller
302
is driven by the pulse motor
305
.
In a first feeding position, as the slider
619
is shifted to a position shown in
FIG. 6B
, a boss
620
a
of a first trigger lever
620
is rotated along a cam portion
619
a
of the slider
619
. The rotation of the first trigger lever
620
acts on a second trigger lever
622
through a trigger spring
621
, with the result that the ASF-system clutch trigger gear
612
is pushed by a boss
622
a
of the second trigger lever
622
.
A compression spring
623
is disposed between the ASF-system clutch gear
613
and the ASF-system clutch trigger gear
612
to bias these gears away from each other. However, since a spring force of the trigger spring
621
is greater than a spring force of the compression spring
623
, the ASF-system clutch trigger gear
612
is shifted toward the ASF-system clutch gear
613
in the thrust direction, with the result that a ratchet portion
612
a
as an engagement portion formed on a side surface of the ASF-system clutch trigger gear
612
is engaged by a ratchet portion
613
a
as an engagement portion formed on a side surface of the ASF-system clutch gear
613
.
A displacement amount of the second trigger lever
622
is set to be greater than a displacement amount of the ASF-system clutch trigger gear
612
, and a difference in displacement amount is absorbed by the trigger spring
621
. Thus, even if the position of the slider
619
is slightly changed due to dimensional errors of parts, the ASF-system clutch gear
613
and the ASF-system clutch trigger gear
612
can positively be engaged by each other.
In a second feeding position, the slider
619
is shifted to a position shown in
FIG. 6C
, and, similar to the first feeding position, the ratchet portions
613
a
,
612
a
of the ASF-system clutch gear
613
and the ASF-system clutch trigger gear
612
are maintained in the engaged condition. However, the slide gear
607
is shifted by the shifting movement of the slide holder
616
, with the result that, as shown in
FIG. 4B
, the slide gear is disengaged from the idle gear
608
and is engaged by the gear portion
611
b
of the switching gear
611
. As a result, in the drive transmitting system, since the idle gear
608
is skipped, the rotational direction of the sheet feeding roller with respect to the conveying roller
302
is reversed in comparison with the first feeding position. That is to say, in the first feeding position, when the conveying roller
302
is rotated to feed the sheet in the normal or forward direction, the sheet feeding roller
102
is also rotated to feed the sheet in the normal direction; whereas, in the second feeding position, when the conveying roller
302
is rotated to feed the sheet in the reverse direction, the sheet feeding roller
102
is rotated to feed the sheet in the normal direction.
When the slider
619
is shifted to a position shown in
FIG. 6D
, a pump position is obtained. In this position, since the boss
620
a
of the first trigger lever
620
is dropped along the cam portion
619
a
, the ASF-type clutch trigger gear
612
is separated from the ASF-system clutch gear
613
by the compression spring
623
, thereby achieving the clutch OFF condition. On the other hand, by the shifting movement of the slide holder
616
, a pump-system trigger rod
635
pushes the pump-type clutch trigger gear
632
through a spring
634
. As a result, ratchet portions
630
a
,
632
a
as engagement portions of the pump-system clutch gear
630
and the pump-system clutch trigger gear
632
are engaged by each other, thereby achieving the clutch ON condition. Also in this case, a pushing amount of the pump-system trigger rod
635
is set to be greater than a displacement amount of the pump-system clutch trigger gear
632
, and a difference therebetween is absorbed by the spring
634
. Thus, even if the position of the slider
619
is slightly changed due to dimensional errors of parts, the pump-system clutch gear
630
and the pump-system clutch trigger gear
632
can positively be engaged by each other.
Now, further detailed explanation is made with reference to the clutch means (first clutch means) of the sheet feeding means as an example. Incidentally, since the clutch means (second clutch means) of the pump is similar, explanation thereof will be omitted here.
As shown in
FIG. 7A
, since the ASF-system clutch gear
613
is opposed to the non-toothed portion
603
d
of the ASF-system output gear
603
, even when the ASF-system clutch gear
613
is rotated together with the ASF-system clutch shaft
610
, the driving force is not transmitted to the ASF-system output gear
603
. On the other hand, as shown in
FIG. 7B
, although the ASF-system clutch trigger gear
612
is always engaged by the ASF-system output gear
603
, since the ASF-system clutch trigger gear
612
can freely be rotated with respect to the ASF-system clutch shaft
610
, even when the ASF-system clutch shaft
610
is rotated, the ASF-system clutch trigger gear
612
is maintained in the stopped condition. In this case, the cam surface
603
c
of the ASF-system output gear
603
is pushed by the biasing lever
614
, thereby preventing inadvertent rotation of the gear (refer to FIG.
3
C).
Further, the ratchet portions
613
a
,
612
a
engageable with each other are symmetrically formed on inner surfaces of the ASF-system clutch gear
613
and the ASF-system clutch trigger gear
612
(the ratchet portion
613
a
is formed on a rear surface of the ASF-system clutch gear
613
shown in
FIG. 7A
) so that, in the condition (clutch ON condition) that the ratchet portions are engaged by each other, when the ASF-system clutch shaft
610
is rotated, the ASF-system clutch gear
613
is rotated to rotate the ASF-system clutch trigger gear
612
through the ratchet portions. As a result, since the ASF-system output gear
603
starts to be rotated, the phase of the non-toothed portion is deviated, thereby engaging the gear
603
b
and the ASF-system clutch gear
613
with each other. Thereafter, if the ASF-system clutch trigger gear
612
is separated, the driving force can be transmitted to the ASF-system output gear
603
only by the ASF-system clutch gear
613
. And, when the ASF-system output gear
603
is rotated by one revolution to return the non-toothed portion to the initial phase, the drive transmission is automatically disconnected.
According to this, so long as the phases of the gears and ratchet portions
613
a
,
612
a
of the ASF-system clutch gear
613
and the ASF-system clutch trigger gear
612
are aligned (i.e., so long as the phases of teeth of the ASF-system clutch gear
613
and the ASF-system clutch trigger gear
612
are synchronized when the ratchet portions
613
a
,
612
a
are engaged by each other), since the ASF-system clutch gear
613
and the ASF-system output gear
603
start to be engaged by being guided by the entirely toothed portion
603
e
(having the tooth width W′) of the ASF-system output gear
603
(i.e., by rotating the ASF-system output gear
603
by transmitting the driving force to the entirely toothed portion
603
e
engaged by the ASF-system clutch trigger gear
612
ratchet-connected to the ASF-system clutch gear
613
), a problem that tops of the teeth of the gears abut against each other to cause poor engagement can be eliminated, and, further, since the ASF-system clutch trigger gear
612
is always engaged by the ASF-system output gear
603
, the tops of the teeth do not, of course, abut against each other.
Accordingly, problems regarding noise and out-of-phase of motor can be eliminated, and the positive switching operation can be achieved. Further, since the pushing of the ASF-system clutch trigger gear
612
by means of the carriage
201
only requires a minimum time until the ASF-system clutch gear
613
and the ASF-system output gear
603
are engaged by each other, it is not required that the carriage
201
remains in the trigger position until the ASF-system output gear
603
is rotated by one revolution. Thus, the recording operation is not delayed.
[Second Embodiment]
Next, as a second embodiment of the present invention, a construction of the drive transmitting apparatus for effecting the drive switching more positively will be explained. Incidentally, here, only constructions different from those in the first embodiment will be explained and the same constructions will be omitted from explanation.
In the first embodiment, an example that the ASF-system clutch gear
613
and the ASF-system output gear
603
start to be engaged smoothly by aligning the phase of the gears in the condition that the ratchets of the ASF-system clutch gear
613
and the ASF-system clutch trigger gear
612
are engaged by each other was explained.
However, immediately after, there is a duration in which both the ASF-system clutch gear
613
and the ASF-system clutch trigger gear
612
are engaged by the gear
603
b
of the ASF-system output gear. In this case, if the phases of the gears and ratchets of the ASF-system clutch gear
613
and the ASF-system clutch trigger gear
612
are deviated and the deviated amount is greater than backlash, three gears may be strongly urged against each other to increase rotational load extremely or three gears may be strongly engaged by each other to prevent rotations thereof. Furthermore, the ASF-system clutch trigger gear
612
may not be separated only by the force of the compression spring
623
.
Thus, it is required that a dimensional relationship between the gears and the ratchets be governed severely. However, in the second embodiment, as shown in
FIG. 8
which is a development view of the ratchets, by setting so that a gap is created between the ratchets when tooth tips (marking portions) of the ASF-system clutch gear
613
and the ASF-system clutch trigger gear
612
are aligned, the above-mentioned problems can be eliminated.
That is to say, even if the phases of the ratchets and the tooth tips are slightly deviated due to the dimensional errors of parts, since such deviation can be absorbed by the gap, the gears do not abut against each other. On the other hand, however, when the ASF-system clutch gear
613
and the ASF-system clutch trigger gear
612
are operated in the condition that they are engaged by each other, the tooth tips thereof are deviated by an amount corresponding to the gap due to the set gap. Thus, when the ASF-system clutch gear
613
and the ASF-system output gear
603
start to be engaged by each other, deviation will occur. However, so long as the deviation amount is smaller than about ¼ of the circular pitch of the gear (dimension corresponding to ¼ of circumference of one gear), the tooth tips do not abut against each other to achieve the positive engagement. With this arrangement, without governing of the several dimensional errors of parts, since the positive switching operation can be effected, the manufacturing cost can be reduced.
[Third Embodiment]
In the above-mentioned embodiments, while an example that the ink jet recording system is used as the recording system of the image forming apparatus was explained, the recording system of the image forming apparatus using the above-mentioned drive transmitting apparatus is not limited to the ink jet recording system, but a thermal transfer recording system, a heat-sensitive transfer recording system or an impact recording system may be used.
Further, the above-mentioned drive transmitting system can be applied to other apparatus such as an image reading apparatus in which an original is fed to a reading position and information on the original is read by reciprocally shifting a carriage having a reading sensor thereon, as well as the image forming apparatus.
According to the above-mentioned embodiments explained in detail, by aligning the phases of the gears and the engagement portions of the input gear and the trigger gear, the tooth tips do not abut against each other in engagement between the input gear and the output gear. Thus, the positive switching of the driving force can be achieved without the noise and the poor drive transmission from the drive source (for example, out-of-phase of the motor).
Further, when the trigger gear is operated by the shifting movement of the carriage, since the pushing time of the trigger gear is minimum, the recording operation is not delayed.
Claims
- 1. An image forming apparatus having a drive transmitting apparatus for selectively transmitting a driving force from a drive source to a driving member through clutch means, said apparatus comprising:head holding means for holding a recording head; an output gear having a non-toothed portion not including a predetermined number of teeth in a tooth width-wise direction and an entirely toothed portion having no non-toothed portion; an input gear disposed at a position where it can be opposed to said non-toothed portion of said output gear and rotated by a driving force from said drive source; a trigger gear meshed with said entirely toothed portion of said output gear and rotatable with respect to a rotary shaft and movable in a thrust direction so as to contact with and separate from said output gear; and engagement portions provided on opposed side surfaces of said input gear and said trigger gear and engageable with each other, wherein when said input gear and said trigger gear are engaged by each other through said engagement portions, phases of gears of said input gear and said trigger gear are synchronized.
- 2. An image forming apparatus according to claim 1, wherein said engagement portions comprise ratchets having symmetrical configuration and engageable with each other, and, a gap is created between said ratchets when the phases of said input gear and said trigger gear are aligned.
- 3. An image forming apparatus according to claim 2, wherein the gap is smaller than ¼ of circumference of the gear.
- 4. An image forming apparatus according to claim 1, wherein the gap is smaller than ¼ of a circular pitch of the gear.
- 5. An image forming apparatus according to claim 1, wherein drive switching of said drive transmitting apparatus is effected by shifting said head holding means and abutting said head holding means against said drive transmitting apparatus.
- 6. An image forming apparatus according to claim 1 or 2, wherein said recording head is an ink jet recording head for discharging ink.
- 7. A drive transmitting apparatus for selectively transmitting a driving force from a drive source to a driving member through clutch means, said apparatus comprising:an output gear having a non-toothed portion not including a predetermined number of teeth in a tooth width-wise direction and an entirely toothed portion having no non-toothed portion; an input gear disposed at a position where it can be opposed to said non-toothed portion of said output gear and rotated by a driving force from said drive source; a trigger gear meshed with said entirely toothed portion of said output gear and rotatable with respect to a rotary shaft and movable in a thrust direction so as to contact with and separate from said output gear; and engagement portions provided on opposed side surfaces of said input gear and said trigger gear and engageable with each other, wherein when said input gear and said trigger gear are engaged by each other through said engagement portions, phases of gears of said input gear and said trigger gear are synchronized.
- 8. A drive transmitting apparatus according to claim 7, wherein said engagement portions comprise ratchets having symmetrical configuration and engageable with each other, and, a gap is created between said ratchets when the phases of said input gear and said trigger gear are aligned.
- 9. A drive transmitting apparatus according to claim 8, wherein the gap is smaller than ¼ of a circular pitch of the gear.
- 10. A drive transmitting apparatus according to claim 8, wherein the gap is smaller than ¼ of circumference of the gear.
Priority Claims (2)
Number |
Date |
Country |
Kind |
11-233803 |
Aug 1999 |
JP |
|
12-231326 |
Jul 2000 |
JP |
|
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