JP2002068519A - Carrying device, and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carrying device capable of restricting kicking a sheet out to realize a stable sheet carry, and an image forming device provided with that to realize high-quality image formation. SOLUTION: In this carrying device provided with a pair of carrying rollers 6 and a pair of sheet discharging rollers 7 provided on the upstream and the downstream sides of an image forming part, a pulse motor 19 to drive the carrying roller 6a, and idler gears 16, 17, and 18 and a sheet discharging roller gear 15b to transmit driving force of the pulse motor 19 to the sheet discharging roller 7a, the diameter D2 of the sheet discharging roller 7a is set to be smaller than the diameter D1 of the carrying roller 6a by 0.99%, and a holding force ratio between the carrying paired rollers 6 and the sheet discharging rollers 7 is set to be 1:2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conveying apparatus for intermittently conveying a sheet while constraining a sheet by a plurality of conveying means, and more particularly, to a conveying apparatus which can be suitably used for an ink jet recording type image forming apparatus. is there.

[0002]

2. Description of the Related Art Conventionally, image forming apparatuses employing various recording methods have been put into practical use. Among them, an ink jet method, a thermal transfer method, etc. are relatively inexpensive and can be made smaller and quieter, and can be used for personal use. It is widely used for office use. In an image forming apparatus using these recording methods, it is general to form an image by moving a sheet relatively to a recording unit in the apparatus.

In the printer of the serial scan system using the ink jet system or the like, the sheet is intermittently stepped by a predetermined width to form an image by a predetermined width.

In general, a sheet is conveyed using a pair of conveying rollers arranged on the upstream and downstream sides of the recording section. Then, in order to reduce the margin generated in the sheet, recording was performed on the leading end of the sheet in a state where the sheet was nipped only by the roller pair on the upstream side of the recording unit, and the sheet was nipped by both the upstream and downstream roller pairs. In this state, recording is performed on the intermediate portion, and recording is performed on the rear end portion in a state where the sheet is nipped only by the roller pair on the downstream side of the recording portion.

In the above-described ink jet system, when plain paper is used as a sheet, the ink tends to elongate at a recording portion by ink, and when a thin sheet is used, slack tends to occur. Therefore, even when the sheet is conveyed in cooperation with the roller pair on the upstream side and the downstream side of the recording unit, it is necessary to regulate the conveyance amount of the roller pair on the upstream side in order to convey the sheet accurately.

For example, in FIG. 6, when the sheet P is sandwiched between the roller pair 106 on the upstream side of the recording head 108 and the roller pair 107 on the downstream side, the sheet clamping force (P1) of the upstream roller pair 106 is reduced. Downstream roller pair 1
07 higher than the sheet holding force (P2) (P1> P2)
Thus, the transport amount is regulated by the upstream roller pair 106, while the transport amount (L2) of the downstream roller pair 107 is larger than the transport amount (L1) of the upstream roller pair 106 (L2> L).
1), the sheet P is conveyed while the downstream roller pair 107 slips, thereby preventing the sheet P from sagging in the recording unit. Here, the transport amount is
This is the distance of sheet conveyance performed by each roller pair each time the image having the predetermined width is formed.

In order to rotationally drive the downstream roller pair 107, generally, a downstream roller pair 1 is driven from a driving source (motor).
A drive train is constituted by a gear train or a timing belt connected to the drive train 07. FIG. 7 shows a conventional example in which the drive transmission system is constituted by a gear train.

[0008]

However, in the case of the above-described prior art, the following problems have occurred.

When the sheet P is conveyed in the above-described conventional example, no problem occurs because the conveyance amount is determined by the roller pair 106 on the upstream side of the recording unit at the leading end and the center of the sheet P. However, when the roller pair 106 and the roller pair 107 on the downstream side of the recording unit cooperate to convey the sheet P, the sheet P is The surface of the downstream roller pair 107 slips ahead of the sheet P, which is delayed from the designed transport amount of the pair 107 and is restrained and regulated by the upstream roller pair 106, while slipping. ing.

FIG. 8 is a view of the drive transmission system constituted by the gear train shown in FIG. 7 as viewed from the direction of arrow C in FIG. Gear 1 on the upstream conveying roller 106a (shown by a broken line)
15a to a gear 115b on a downstream conveying roller 107a (shown by a broken line).
6, 117 and 118 are connected to transmit the drive.

There is a lost motion (a backlash of gear engagement) in the gear train of the drive transmission system. As described above, since the transport amount L2 by the downstream transport roller 107a is set slightly larger than the transport amount L1 by the upstream transport roller 106a, the upstream roller pair 106 and the downstream Roller pair 1
While the sheet P is conveyed cooperatively at 07, the lost motion of the drive transmission system is leaning in one direction.

The direction is a direction in which the roller pair 107 on the downstream side can freely rotate in the transport direction by an amount corresponding to the total amount of lost motion unless there is a constraint by the sheet P. Specifically, circles 141, 142, and 14 in FIG.
A backlash of gear engagement is formed at a portion indicated by 3,144.

The rear end of the sheet P is a pair of rollers 106 on the upstream side.
At the moment when the sheet P passes through the roller pair 106 on the upstream side.
Phenomenon of kicking out occurs. The mechanism of this kick-out phenomenon will be described with reference to FIG.

Reference numeral 106a denotes an upstream conveying roller;
Is a pinch roller, and P is a sheet. The pinch roller 106b is urged by the force of the spring P1 to the conveying roller 106a, and conveys the sheet P while gripping the sheet P with the pinching force P1 (FIG. 9A).

The rear end of the sheet P is a pair of rollers 106 on the upstream side.
9, the pinch roller 106b starts to return to the surface of the transport roller 106a (FIG. 9 (b)), and the sheet P is kicked out by being pushed by the pinch roller 106b (FIG. 9 (c)). )).

The degree of the kicking is mainly determined by the thickness of the sheet P and the curvature of the pinch roller 106b.
The larger the thickness of the sheet P, the more the pinch roller 106b
Has a property that kicking out becomes more remarkable as the curvature becomes larger.

In the configuration according to the conventional example, when the roller pair 106 and the roller pair 107 on the upstream side of the recording unit convey the sheet P in cooperation with each other, as shown in FIG. The backlash of the gear train of the drive transmission system that drives the pair of rollers 107 is shifted in one direction, so that the roller pair 107 on the downstream side can freely rotate in the transport direction unless restrained by the sheet P.

Therefore, when the rear end of the sheet P passes through the pair of conveying rollers 106 on the upstream side, the sheet P is kicked out,
The maximum number of sheets P corresponding to the transport amount of the total backlash
May progress at a stretch.

The sheet holding force (P2) of the downstream roller pair 107 is equal to the sheet holding force (P2) of the upstream roller pair 106.
Since the sheet P is set smaller than 1), depending on the thickness of the sheet P, the curvature of the pinch roller 106b, or the stiffness of the sheet P, the sheet P cannot be completely restrained by the pair of downstream rollers 107 and is conveyed by the total amount of backlash. There is a possibility that you will be kicked out even more than the amount equivalent.

Therefore, the sheet P is moved to the upstream roller pair 1
06, the conveyance amount of the sheet P is increased in an unstable manner, the image is not connected, and the image quality is deteriorated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art. It is an object of the present invention to suppress a kick-out of a sheet and realize a stable sheet conveyance. It is an object of the present invention to provide an image forming apparatus which realizes high-quality image formation.

[0022]

In order to achieve the above object, according to the present invention, there is provided a first conveying means for conveying a sheet, and a first conveying means provided downstream of the first conveying means in a sheet conveying direction. A second conveying unit; a driving unit for driving the first conveying unit; and a drive transmitting unit for transmitting a driving force of the driving unit to the second conveying unit. In a transport device that cooperates with the transport unit and conveys the sheet intermittently while restraining the sheet, the designed sheet transport amount of the second transport unit is made smaller than the designed sheet transport amount of the first transport unit. I made it smaller.

Accordingly, when the sheet is conveyed while being restrained by both the first and second conveying means, the second conveying means is not driven by the drive transmitting means but is driven by the first conveying means. The driving means is driven by the driving force received from the sheet sent out, and the lost motion of the drive transmitting means gradually moves toward the first conveying means.

Further, while the sheet is conveyed while being constrained by both the first and second conveyance means, the difference between the designed sheet conveyance amounts of the first and second conveyance means is determined by the drive transmission means. Is larger than the sheet conveyance amount corresponding to the lost motion.

Thus, while the sheet is conveyed while being constrained by both the first and second conveying means, the lost motion of the drive transmission means is completely deviated toward the first conveying means.

Here, that the lost motion of the drive transmission means is biased toward the first transport means means that when the first transport means is fixed, the second transport means moves in the direction opposite to the transport direction. But cannot move in the transport direction.
Conversely, if the lost motion is shifted toward the second transport means, the first transport means cannot move in the transport direction when the second transport means is fixed.

Therefore, in a state where the lost motion of the drive transmission means is biased toward the first conveyance means, even if a driving force is applied to the second conveyance means due to kicking out of the sheet by the first conveyance means, etc. The second transport means cannot move.

Also, the sheet restraining force of the second conveying means is
It may be greater than the sheet restraining force of the first conveying means.

Thus, the sheet is conveyed while being controlled by the second conveying means.

Further, it is preferable to provide a control means for increasing the drive amount of the drive means to a predetermined amount from the time when the lost motion of the drive transmission means is shifted toward the first transport means.

Further, the control means may increase the drive amount of the drive means immediately after the trailing edge of the sheet leaves the constraint of the first transport means by an amount corresponding to the lost motion of the drive transmission means.

Thus, regardless of whether the sheet is conveyed by one of the first and second conveying means and the case where the sheet is conveyed while being constrained by both, the sheet conveying amount is always kept constant. be able to.

The sheet preferably has a predetermined thickness or more.

Further, in the transport device of the present invention, the first transport means for nipping and transporting the sheet in a predetermined transport direction, and the downstream side of the first transport means in the transport direction are provided. The driving force of the second transporting means and the driving means is the second driving means.
Drive transmitting means for transmitting to the conveying means, the drive transmitting means has a play that allows the sheet sandwiched by the second conveying means to freely move a predetermined play length before and after in the conveying direction. And between the time when the leading edge of the sheet being conveyed by the first conveying means is nipped by the second conveying means and the time when the sheet rear end is released from being nipped by the first conveying means. The transport amount of the sheet by the first transport unit is configured to be longer than the play length by more than the transport amount of the sheet by the second transport unit corresponding to the drive amount of the drive unit during that time. It is characterized by being.

The second transport means has a transport roller to which the drive is transmitted by the drive transmission means, and the play of the drive transmission means allows the peripheral surface of the transport roller to freely rotate by the play length. Good.

The first transporting means transports the sheet at a first transporting speed, the second transporting means transports the sheet at a second transporting speed, and the sheet transported by the first transporting means. The amount of sheet transported by the first transport unit during a period from when the leading edge is sandwiched by the second transport unit to when the sheet rear end is released from being sandwiched by the first transport unit is the same. The first transport speed is set to the second transport speed so as to be longer than the play length of the sheet by the second transport unit corresponding to the drive amount of the drive unit.
It is good that it is faster than the transfer speed of.

The transport amount of the first transport unit after the leading edge of the sheet being transported by the first transport unit is sandwiched by the second transport unit is equivalent to the drive amount of the drive unit during that time. After the play length becomes longer than the transport amount of the sheet by the second transport unit, the transport amount of the sheet depends on the second transport unit. So that a slip occurs between the second
The holding force of the sheet by the conveying means may be larger than the holding force of the sheet by the first conveying means.

The transport amount of the first transport means after the leading edge of the sheet being transported by the first transport means is sandwiched by the second transport means corresponds to the drive amount of the drive means during that time. After the play length becomes longer than the sheet conveyance amount by the second conveyance means, the second
The conveying means may have a control means for controlling the driving means so as to convey the sheet at the first conveying speed.

The first transporting means repeats transporting and stopping by a first predetermined amount, and the second transporting means synchronizes with the first transporting means so that the second transporting means is less than the first predetermined amount. The conveyance amount of the first conveyance unit after the leading end of the sheet being conveyed by the first conveyance unit is sandwiched by the second conveyance unit, and the conveyance amount of the sheet conveyed by the first conveyance unit is repeated. After the play length is longer than the sheet conveyance amount by the second conveyance unit corresponding to the driving amount of the driving unit, the sheet conveyance amount depends on the second conveyance unit, and the sheet and the sheet The sheet holding force by the second conveying means is configured to be larger than the sheet holding force by the first conveying means so that a slip is generated between the first conveying means and the second conveying means. Transport means stops and transports the first transport amount. May have a control means for controlling said drive means to return Ri.

Further, in the transport device of the present invention, the first transport means for nipping the sheet and transporting the sheet in a predetermined transport direction, and the downstream side of the first transport means in the transport direction are provided. The driving force of the second transporting means and the driving means is the second driving means.
And a drive transmitting means for transmitting the driving force to the first conveying means.
The transport speed of the first transport unit and the second transport unit are made faster than the transport speed of the second transport unit.
By the time the trailing end of the sheet being conveyed by both of the conveyance means passes through the first conveyance means, the play in the conveyance direction of the second conveyance means by the drive transmission means is eliminated. It is characterized by having done.

Further, according to the present invention, there is provided an image forming apparatus comprising: an image forming means for forming an image on a sheet conveyed by the conveying device. 2 is provided between the two transport means.

It is preferable that the first and second transport means repeat transport and stop, and the image forming means forms an image during the stop.

[0043]

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the dimensions of the components described in this embodiment,
The materials, shapes, relative arrangements, and the like are not intended to limit the scope of the present invention only to them unless otherwise specified.

In the present embodiment, an explanation will be given using an ink jet printer as an example of the image forming apparatus.

FIG. 1 is a perspective view of a main part of a recording unit, FIG. 2 is a schematic sectional view of an image forming apparatus, FIG. 3 is an explanatory view of a lost motion of a drive transmission gear train, and FIG. is there.

First, the schematic structure of the ink jet printer will be described with reference to FIG.

A sheet feeding cassette 26 including a stacking plate 21, a first pressing unit 22, a second pressing unit 23, a contact member 24, and a sheet 25 is inserted into the main body 31 of the image forming apparatus. The sheet 25 is pressed against the paper feed roller 29 by the first pressing means 22.

In response to a start command of means (not shown), the motor for rotating the paper feed roller 29 is turned on, and the paper feed roller 29 starts rotating. As a result, only the uppermost one sheet P of the fed sheet 25 is separated and fed at the end of the wall-shaped barrier 27 of the sheet feeding cassette 26. Sheet 2
Reference numeral 5 denotes a telephone card size having a width of 54 mm, a length of 86 mm, and a thickness of 0.17 mm, which is obtained by applying an ink absorber to a PET film base.

Reference numeral 6 denotes a pair of conveying rollers as first conveying means, which is disposed upstream of the image forming means in the sheet conveying direction, and includes a driving-side conveying roller 6a and a driven-side driven roller 6b pressed against the conveying roller 6a. Equipped. Reference numeral 7 denotes a discharge roller pair as a second conveyance means, which is disposed downstream of the image forming means in the sheet conveyance direction, and includes a drive-side discharge roller 7a and a driven-side driven roller 7b pressed against the discharge roller 7a. Equipped.

Reference numeral 8 denotes a recording head as an image forming means, which is an ink jet recording system for discharging ink onto a sheet P conveyed by the conveying roller pair 6 or the discharge roller pair 7 in accordance with image information and recording. Used. That is, the recording head 8 has a fine liquid ejection orifice, a flow path, an energy action section provided in a part of the flow path, and an energy for generating droplet forming energy to act on the liquid in the action section. Generating means.

As such an energy generating means,
A recording method using an electromechanical transducer such as a piezo element, a recording method using an energy generating means for emitting heat by irradiating an electromagnetic wave such as a laser, and discharging droplets by the action of the heat, or a heating resistor. There is a recording method using an energy generating means for discharging the liquid by heating the liquid with an electrothermal converter such as a heating element.

Among them, a recording head used in an ink jet recording method for discharging a liquid sheet by thermal energy can arrange liquid discharge ports (orifices) for forming discharge droplets at a high density. It is possible to record at high resolution. Among them, a recording head using an electrothermal transducer as an energy generating means is easy to make compact, and is a recent IC with a remarkable advance in technology and reliability in the semiconductor field.
It is advantageous because it can fully utilize the advantages of the technology and micromachining technology, can be easily mounted at high density, and has a low manufacturing cost.

The recording head 8 is mounted on a carriage 9, and the carriage 9 is mounted on guide rails 10a, 10a.
The sheet reciprocates in the width direction of the sheet (the direction perpendicular to the drawing) along b. The recording head 8 records vertically downward on a sheet supported by a platen 11 disposed at an opposing position.

Next, a specific configuration of the recording section will be described with reference to FIG.

The recording head 8 is equipped with a plurality of heads capable of performing full-color recording, and includes cyan C, magenta M,
Heads 8C, 8M, 8Y, and 8Bk equipped with yellow Y and black Bk color inks are arranged side by side in the scanning direction of the carriage 9. Heads 8C, 8M, 8Y, 8 for each color
Bk ejects ink from 256 nozzles arranged in a line at a pitch of 1200 dpi, and discharges 5.4187 m on the sheet P.
Recording is performed in m width.

A drive belt 14 is connected to the carriage 9 on which the heads 8C, 8M, 8Y, 8Bk of the respective colors are mounted, and is configured to reciprocate in the direction of arrow B by a pulse motor (not shown).

A pair of transport rollers 6 and a pair of paper discharge rollers 7 are arranged on the upstream side and the downstream side of the recording section, respectively. The sheet is intermittently conveyed in the direction of arrow A by a distance equal to the recording width (recording length in the sheet conveying direction).

The diameter D2 of the discharge roller 7a is 0.99% smaller than the diameter D1 of the transport roller 6a (D2 = D1 × 0.9901). The driven roller 6b on the transport side and the driven roller 7b on the discharge side are urged by the urging means (not shown) toward the transport roller 6a and the discharge roller 7a, respectively. The ratio between the urging pressure of the driven roller 6b and the urging pressure of the driven roller 7b, that is, the ratio of the clamping force between the pair of conveying rollers 6 and the pair of discharging rollers 7 is set to 1: 2.

The transport roller 6a and the discharge roller 7a
A transport roller gear 15a and a paper discharge roller gear 15b are press-fitted and fixed to the shaft ends of these shafts, and idler gears 16, 17, and 18 are provided between these gears to drive the transport roller 6a to discharge paper. A drive transmission gear train as drive transmission means for transmitting to the roller 7a is configured.

A gear 20 is press-fitted into a pulse motor 19 as a driving means and meshes with a transport roller gear 15a. Since the gear 20, the transport roller gear 15a, and the discharge roller gear 15b all have the same number of teeth, the rotation speeds of the pulse motor 19, the transport roller 6a, and the discharge roller 7a are the same. The diameter D2 of the discharge roller 7a
Is 0.99% smaller than the diameter D1 of the transport roller 6a, so that the peripheral speed (second transport speed) of the discharge roller 7a is the peripheral speed (first transport speed) of the transport roller 6a.
Slower than.

As the pulse motor 19, a five-phase stepping motor having a basic step angle of 0.36 ° is used. The driving of the pulse motor 19 is controlled by control means 40 having a CPU, a memory, and the like, and is driven by a motor driver 41 (FIG. 1). Further, the control means 40 is also connected to a sensor 50 for detecting the leading edge of the sheet. Note that the recording width of one line in the sheet conveyance direction corresponds to a 2/5 circumference of the conveyance roller 6a. A table summarizing the above contents is shown in FIG.

FIG. 3 shows a state in which the conveying roller 6a is connected to the discharge roller 7a.
In this figure, a predetermined amount of backlash is guaranteed for the meshing of the gears. The module of each gear is 0.3, and the backlash of each of the idler gears 16, 17, 18 and the paper discharge roller gear 15b in mesh with one of the upstream gears is set to 60 μm by design.

FIG. 5 (b) shows the results obtained by calculating the free rotation angle (rotation angle of play) due to backlash from the number of teeth and the pitch circle of each gear.

When the transport roller 6a is fixed, the discharge roller 7a has a total backlash of the drive transmission gear train, which is 4.
It has a free rotation angle of 97 °. This rotation angle is the lost motion of the drive transmission gear train composed of the idler gears 16, 17, 18 and the discharge roller gear 15b. Since the diameter of the discharge roller 7a is 4.269 mm, the free rotation angle, that is, the transport amount (play length) corresponding to the lost motion is 185 μm as shown in the following equation. This also corresponds to a rotation angle of the pulse motor 19 of 13.8 steps. 4.296 × π × (4.97 / 360) = 0.185

The above calculations are based on the assumption that the dimensional accuracy of the mechanical parts such as the distance between the axes of the gears and the gears themselves is as designed. Actually, the dimensional accuracy of parts varies, so the transport amount (play length) corresponding to the lost motion, which is the total amount of backlash, is
There are some sizes around the above calculated values. For this reason,
In an actual machine, it is preferable to actually measure the transport amount corresponding to the lost motion.

Next, with reference to FIG. 4, how the sheet is conveyed by the conveying roller pair 6 and the discharge roller pair 7 will be described. FIG. 4A illustrates the moment when the sheet P is fed and conveyed by the conveying roller pair 6, and the leading edge of the sheet is detected by the sensor 50. From this point, the pulse motor 19 is intermittently driven every 400 steps.
The sheet P is intermittently conveyed by 5418.7 μm (first conveyance amount).

FIG. 4B shows a state in which the sensor 50 is
When the pulse motor 19 is driven by a predetermined number of steps by the control means 40 after being detected by
This represents the moment when the leading edge of the sheet P reaches the discharge roller pair 7 while an image is printed on the sheet P. Thereafter, the sheet P is conveyed while being constrained (gripped) by both the conveying roller pair 6 and the paper discharging roller pair 7. The designed conveying amount (second conveying amount) of the paper discharging roller 7a is as described above. As described above, since the transport amount is designed to be 0.99% smaller than the designed transport amount (first transport amount) of the transport roller 6a, the sheet P gradually advances the paper discharge roller 7a by its own stiffness, and is discharged. This eliminates play in the transport direction of the paper roller 7a.

Now, assuming that the transport amount corresponding to the lost motion is 185 μm as calculated above, the control unit 40 reduces the transport amount by the transport roller 6 to 18.689 mm from the state of FIG. When the pulse motor 19 is driven by a corresponding amount, all the lost motions of the drive transmission gear train are shifted toward the conveying roller 6a (1).
8689 x 0.0099 = 185). That is, play in the transport direction of the paper discharge roller 7a is eliminated. FIG. 4C shows this state.

From this point, the control means 40 increases the driving amount of the pulse motor 19 by one time from 400 steps to 404 steps. As previously mentioned,
The pinching force of the discharge roller pair 7 is 2 of the pinching force of the transport roller pair 6.
Since the setting is doubled, the sheet P is conveyed while being controlled by the discharge roller pair 7.

Since the diameter of the discharge roller 7a is set to be 0.99% smaller than the diameter of the transport roller 6a, the drive amount is increased by 1% and a predetermined transport amount is guaranteed (5365. 0 × 404/400 = 5418.
7). That is, the amount of one conveyance by the paper discharge roller 7a changes to the first amount of conveyance.

At this time, although the designed transport amount of the transport roller 6a is naturally increased by 1%, the sheet P does not buckle due to its stiffness, and the sheet P and the transport roller 6a slip.

In the present embodiment, as described above, the thickness is set to 0.
Although a 17 mm PET-based film is used as a sheet, a sheet having a thickness of 0.12 mm or more (105 g /
(corresponding to a sheet of m ² or more), the stiffness is strong, and thus the configuration of the present embodiment can favorably record an image without buckling in the recording unit. However, whether or not buckling occurs depends, of course, on the distance between the transport roller pair 6 and the discharge roller pair 7, the shape of the paper path, and the like.

FIG. 4D shows that the sheet P continues to be conveyed in such a state, and the rear end of the sheet P reaches the nip portion of the conveying roller pair 6.

From the state shown in FIG. 4C to the state shown in FIG. 4D, the backlash of the drive transmission gear train is as shown in FIG.
It is shown as follows. That is, circle 4 in FIG.
Backlash is formed at the portions indicated by 1, 42, 43, and 44, and the lost motion of the drive transmission gear train is shifted toward the transport roller 6a, so that the discharge roller 7a rotates in the direction opposite to the normal transport direction. Yes, but cannot rotate in the normal transport direction.

Therefore, even if the trailing edge of the sheet P is about to be kicked out by the pair of conveying rollers 6 at the time shown in FIG.
The sheet P is not kicked out due to the fact that it is twice the holding force of the sheet P.

At the moment when the sheet P comes out of the pair of conveying rollers 6, the driving force of the conveying roller 6 a is lost, so that the sheet P is conveyed only by the pair of discharging rollers 7.

As described above, since the lost motion of the drive transmission gear train to the discharge roller 7a is biased toward the transport roller 6a, only at this time, a pulse of 185 μm, which is the transport amount corresponding to the lost motion, is applied. Motor 1
Nine drive steps are increased by 14 steps to drive in 418 steps. After that, the driving of 404 steps is repeated again.

Although the number of steps to be increased is exactly 13.8 steps as described above, the amount of 0.2 steps is negligible since it corresponds to a transport amount of 2.7 μm.

FIG. 4E shows the state immediately before the image is printed on the sheet P and the sheet P is discharged by the discharge roller pair 7.

In printing the next sheet, the above-described operations (a) to (e) of FIG. 4 are repeated.

As described above, in the above-described conveying apparatus, the designed sheet conveying amount of the second conveying unit is smaller than the designed conveying amount of the first conveying unit. Can be brought closer to the first conveying means, and kicking out of the sheet by the first conveying means can be suppressed.

Further, while the sheet is conveyed while being constrained by both the first and second conveyance means, the difference between the designed sheet conveyance amounts of the first and second conveyance means is determined by the drive transmission means. Is configured to be larger than the sheet conveyance amount corresponding to the lost motion, the lost motion of the drive transmission means is completely deviated to the first conveyance means side, and the kicking of the sheet can be further suppressed.

Further, since the sheet restraining force of the second transport means is configured to be larger than the sheet restraining force of the first transport means, the transport amount of the first transport means exceeds the transport amount of the second transport means. Even if the sheet is about to be kicked out by the first conveying means, the second conveying means restrains the sheet and prevents slipping, thereby reliably preventing unstable conveyance of the sheet. can do.

Further, there is provided control means for increasing the drive amount of the drive means to a predetermined amount from the time when the lost motion of the drive transmission means is shifted to the side of the first conveying means. Since the driving amount of the driving unit immediately after leaving the constraint of the first conveying unit is controlled so as to be increased by an amount corresponding to the lost motion of the driving transmitting unit, the sheet conveying amount is always kept constant, and stable sheet conveyance is performed. Becomes possible.

Further, in the image forming apparatus provided with the above-described conveying device, since the sheet can be stably conveyed with a constant conveying amount, occurrence of image defects such as white streaks can be prevented and high quality can be achieved. Image formation becomes possible.

[0086]

As described above, in the present invention,
The kicking of the sheet by the first conveying means can be suppressed.

[Brief description of the drawings]

FIG. 1 is a perspective view of a main part of a recording unit of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of an image forming apparatus according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram of lost motion of a drive transmission gear train of the transport device according to the embodiment of the present invention.

FIG. 4 is an operation explanatory view of the transport device according to the embodiment of the present invention.

FIG. 5 is a table showing a specific configuration of the transport device according to the embodiment of the present invention, in which (a) is a table showing the configuration of a transport roller and a discharge roller, and (b) is a drive transmission. It is a table | surface which shows the lost motion of a gear train.

FIG. 6 is a schematic diagram of a main part of a recording unit of an image forming apparatus according to the related art.

FIG. 7 is a perspective view of a main part of a recording unit of an image forming apparatus according to the related art.

FIG. 8 is an explanatory diagram of a lost motion of a drive transmission system of a transfer device according to the related art.

FIG. 9 is an explanatory diagram of a kick-out phenomenon of a sheet in a transport device according to the related art.

[Explanation of symbols]

 Reference Signs List 6 transport roller pair 6a transport roller 6b driven roller 7 discharge roller pair 7a discharge roller 7b driven roller 8 recording head 9 carriage 10a, 10b guide rail 11 platen 15a transport roller gear 15b discharge roller gear 16, 17, 18 idler gear 19 pulse motor 20 gear 40 control means P sheet

Claims (15)

[Claims] A first conveying means for conveying a sheet; a second conveying means provided downstream of the first conveying means in a sheet conveying direction; and a driving means for driving the first conveying means. And a drive transmitting means for transmitting the driving force of the driving means to the second conveying means, wherein the first and second conveying means cooperate to convey the sheet intermittently while restraining the sheet. An apparatus according to claim 1, wherein a designed sheet conveying amount of said second conveying means is smaller than a designed sheet conveying amount of said first conveying means. 2. The method according to claim 1, wherein while the sheet is conveyed while being constrained by both the first and second conveyance means, a difference between a designed sheet conveyance amount of the first and second conveyance means is determined. 2. The conveyance device according to claim 1, wherein the sheet conveyance amount is greater than a sheet conveyance amount corresponding to a lost motion of the drive transmission unit. 3. The conveying device according to claim 1, wherein the sheet constraining force of the second conveying means is larger than the sheet constraining force of the first conveying means. 4. A control means for increasing the drive amount of said drive means to a predetermined amount from the time when the lost motion of said drive transmission means is shifted toward said first transport means. 4. The transport device according to 3. 5. The control means increases the amount of driving of the driving means immediately after the trailing edge of the sheet leaves the constraint of the first conveying means by an amount corresponding to the lost motion of the driving transmission means. The transport device according to claim 4, wherein 6. The conveying device according to claim 1, wherein the sheet has a thickness greater than a predetermined value. 7. A first conveying means for nipping a sheet and conveying the sheet in a predetermined conveying direction; a second conveying means provided downstream of the first conveying means in the conveying direction; A drive transmitting means for transmitting a driving force to the second transport means, wherein the drive transport means is configured such that the sheet held by the second transport means is free for a predetermined play length before and after in the transport direction. The sheet has a play that allows movement, and the leading end of the sheet being conveyed by the first conveying means is held by the second conveying means, and then the trailing end of the sheet is released from being held by the first conveying means. In the meantime,
The transport amount of the sheet by the first transport unit is configured to be longer than the play length by more than the transport amount of the sheet by the second transport unit corresponding to the drive amount of the drive unit during that time. A transfer device. 8. The second conveying means has a conveying roller to which drive is transmitted by the drive transmitting means, and the peripheral surface of the conveying roller freely rotates by the play length by the play of the drive transmitting means. The transfer device according to claim 7, which is capable of being used. 9. A first conveying means for conveying a sheet at a first conveying speed, a second conveying means for conveying a sheet at a second conveying speed, and being conveyed by said first conveying means. The amount by which the sheet is conveyed by the first conveying means during a period from when the leading edge of the sheet is nipped by the second conveying means to when the trailing end of the sheet is released from being nipped by the first conveying means, The first transport speed is set to be equal to or greater than the play length than the transport amount of the sheet by the second transport unit corresponding to the drive amount of the drive unit.
9. The transfer device according to claim 7, wherein the transfer speed is higher than the transfer speed. 10. The amount of conveyance of the first conveying means after the leading edge of the sheet being conveyed by the first conveying means is sandwiched by the second conveying means is equal to the driving amount of the driving means during that time. After the play length becomes longer by the play length than the transport amount of the sheet by the second transport unit, the transport amount of the sheet depends on the second transport unit, and the sheet and the first transport unit 10. The conveying apparatus according to claim 9, wherein the sheet holding force by the second conveying means is set to be larger than the sheet holding force by the first conveying means so that a slip occurs between the sheet conveying means and the sheet conveying means. . 11. The amount of conveyance of the first conveying means after the leading edge of the sheet conveyed by the first conveying means is sandwiched by the second conveying means is the amount of driving of the driving means during that time. After the play length becomes longer than the sheet conveyance amount by the second conveyance unit corresponding to the second conveyance unit, the second conveyance unit conveys the sheet at the first conveyance speed. 11. The transport device according to claim 10, further comprising control means for controlling the transfer. 12. The first transport means repeats transport and stop of a first predetermined amount, and the second transport means is smaller than the first predetermined amount in synchronization with the first transport means. Second
The conveyance and stop of the predetermined amount are repeated, and the conveyance amount of the first conveyance unit after the leading end of the sheet being conveyed by the first conveyance unit is sandwiched by the second conveyance unit, After the play length is longer than the sheet conveyance amount by the second conveyance unit corresponding to the driving amount of the driving unit, the sheet conveyance amount depends on the second conveyance unit, and the sheet and the sheet The sheet holding force by the second conveying means is configured to be larger than the sheet holding force by the first conveying means so that a slip is generated between the first conveying means and the second conveying means. 9. The transfer device according to claim 7, wherein the transfer unit includes a control unit that controls the driving unit so as to repeat the transfer and stop of the first transfer amount. 10. 13. A first transporting means for nipping and transporting a sheet in a predetermined transporting direction, a second transporting means provided downstream of the first transporting means in the transporting direction, and A drive transmitting means for transmitting a driving force to the second transport means, wherein the transport speed of the first transport means is higher than the transport speed of the second transport means, whereby the first transport means is provided. By the time the trailing edge of the sheet being conveyed by both the first and second conveying units passes through the first conveying unit, the play in the conveying direction of the second conveying unit due to the drive transmission unit has disappeared. A transport device characterized by having a configuration as described above. 14. An image forming apparatus comprising: the conveying device according to claim 1; and image forming means for forming an image on a sheet conveyed by the conveying device. An image forming apparatus, wherein the image forming unit is provided between the first and second conveying units. 15. An image forming apparatus according to claim 14, wherein said first and second transport means repeat transport and stop, and said image forming means forms an image while stopped.